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A cognitive antenna array, which is designed by using the Deep Reinforcement Learning (DRL) is proposed in this paper to adapt the complex electromagnetic environment. Specifically, the phased array antenna is utilized as the manipulatable component to achieve the characteristic of beam steering with the help of the DRL algorithm. We begin by establishing a DRL-based framework, which is comprised of a microprogrammed control unit, power divider, digital phase shifter, and the patch antenna array. In the DRL algorithm, the desired beam steering is obtained through trial-and-error interactions with the environment, which is required to observe predefined rewards based on current state and action. Next, the system is trained to perform beam steering, and a set of hyper-parameters of the deep neutral network are obtained and stored for practical usage. Good agreement is achieved between the simulated and measured radiation patterns of the planar phased array antenna, which validates of the DRL-based phase distribution regulation algorithm. Finally, the algorithm is implemented in the design process of a conformal phased array antenna, and it is shown that the measured radiation performance of the array is satisfactory for different beam scan angles.

This letter presents a new circuit topology for a vector sum phase shifter where the amplitudes and phases of I and Q are simultaneously varied using a single analog control signal. The simultaneous adjustment of amplitudes and phases of I and Q allows for the vector sum's large phase tuning while maintaining its amplitude. Moreover, various functions of vector summation are all performed in a single stage, minimizing the chip real estate and power consumption. The maximum range of analog phase tuning with a constant amplitude is theoretically 180°, but in practice, it is limited by the tuning range of the utilized varactors. To achieve a large phase tuning range given varactors with limited tunability, digital control has been added to allow for coarse tuning of the phase. The utilized approach for coarse phase tuning preserves the chip area and power consumption but causes amplitude variation. The phase shifter performance is verified by simulations and measurements.

This communication presents a low-profile and efficient low-VHF antenna designed for compact Unmanned Ground Vehicles (UGVs). An effective miniaturization strategy for a top-loaded multi-element monopole antenna is proposed to improve its gain while maintaining a low profile. The approach introduces multiple closely-spaced short vertical radiating elements and a structurally-constructed 180-degree phase shifter connecting the elements on a small ground plane. The phase shifter enables electric currents flowing through the vertical elements to be in phase, resulting in enhanced radiation without increasing the antenna profile. In order to improve the antenna bandwidth, a monopole configuration with a sleeve feed and capacitive top-loading is adapted. The proposed antenna optimized for a compact UGV via parametric analysis has a height of 0.028λ at 42 MHz (the corresponding electrical size ka = 0.24). The measured performance of an antenna prototype shows the 3-dB bandwidth of 0.67 MHz and peak gain of -2.5 dBi. The proposed design can achieve more than 16 % reduction in lateral dimensions and 1-dB improvement in gain compared to the state-of-the-art design with similar topology. The performance of the antenna integrated on an actual UGV system is also evaluated by experiments.

This article presents a 2.4-4-GHz wideband 7-bit switch-type phase shifter (STPS) with a switch driver. Three switch-type phase shifting topologies are employed for the design of the phase shifter (PS), including the switched L/C structure, T-type structure, and high-/low-pass network. For minimizing the phase and amplitude deviations, an improved T-type structure with a switched filter structure has been proposed to boost the performance of the PS. Besides, a phase compensation cell also has been adapted to further decrease the phase error of the STPS. Based on the topology choice of each cell and the amplitude compensation among cells, a systematic design method is developed to extend the bandwidth of the PS. The proposed 7-bit STPS was implemented in the 0.5-μm GaAs pHEMT process. The measured root-mean-square (rms) phase error of the proposed STPS is less than 3.1° from 2.4 to 4 GHz and less than 1.5° at 2.8-3.7 GHz. The average insertion loss (IL) is 4.5-4.9 dB with an rms amplitude error of less than 0.34 dB. IP $_{{1,dB}}$ is about 30 dBm. To the best of our knowledge, this PS achieves the highest resolution and the lowest rms amplitude error among the published GaAs/GaN PSs over a similar frequency band. The IL, bandwidth, and rms phase error of the proposed PS also show good performance.

This article proposes the synthesis design method of the dual-band differential phase shifters with independent filtering passbands and predetermined phase shifts. The filtering unit of the proposed phase shifter adopts a simple branch-line structure, which possesses its characteristics of controllable dual-band frequency ratios and bandwidths. Meanwhile, the Schiffman phase alignment element holds the capability of achieving different predetermined phase shifts in dual band. In our design, dual-mode resonator and dual-mode J-inverter models for the filtering units are equivalently established, and the amplitude and phase closed-form formulas for the proposed dual-band phase shifter are further numerically obtained for the first time. This proposed work features new synthesis method, integrated higher order filtering response with two independently prescribed bandwidths, and concurrent predetermined dual-band phase shifts. Design procedures are provided in detail for a quick design. Finally, two dual-band phase shifters with different frequency ratios and phase shifts are designed and demonstrated. The experimental and measured results match well.

A circular polarization (CP)-agile and continuous beam-steerable array antenna is presented using a hybrid design approach. It is accomplished by combining digital reconfigurable antenna elements with analog continuously tunable phase shifters. To realize both polarization reconfiguration and initial phase generation for beam-scanning simultaneously, the designed antenna element enables eight states that corresponds to two CP modes with four quantized phases. The phase shifters further provide additional variable phases of -90° to 0° for antenna element excitation. Superposition of the initial and additional phases helps to satisfy a full and continuous 360° phase coverage for a beam-steerable array. Meanwhile, the phase decomposition also facilitates the design of phase shifters without complex or cascaded structures. By altering the bias states of the electronic components loaded in the array antenna, CP switching and beam scanning can be independently controlled. For verification, prototypes of the antenna element, phase shifter, and a four-element array are all fabricated and tested. Reasonable agreement is obtained between simulation and measurement. The resultant array could scan up to nearly ±40° off the boresight, along with stable radiation patterns and good CP performance.

We present a new technique to self-mitigate the RF power variations in microwave photonic phase shifters (MPPS) based on microring resonators by exploiting the root problem of varying optical intensities at different optical phase shifts to harness a varying and opposing optical equalization gain. Whilst optical gain mediums are commonly present in microwave photonic systems to overcome optical loss, choosing an appropriate equalization gain point to strike a balance between the optical gain transformation of weak and preservation of strong signals allows the proposed system to effectively achieve minimal radio frequency (RF) power variation across all signals without interfering with the RF phase shifting operation. Simulation results show an inline MPPS based on the phase and amplitude of conventional resonant structures with a capability to successfully minimize the RF power variations by 80% for up to 25 dB of phase-dependent power variations throughout the full 360° phase tuning range. Experimental results verify the MPPS operation based on a single microring resonator by significantly reducing the large RF power variations from 9 dB to less than ±1.25 dB, while maintaining the same RF phase shifting operation. We then verify the use of the proposed inline MPPS to adaptively minimize the self-interference by optimizing the phase compensation in a self-interference cancellation system. We demonstrate a cancellation bandwidth of 100 MHz with peak in-band cancellation of up to 40 dB while exhibiting the capability to recover weak signals of interest at operating center frequencies ranging from 5-20 GHz.

This letter presents a high precision wideband active vector-modulating phase shifter with high dynamic range gain control ability. Compared with conventional switching-filter phase shifter and vector-modulation phase shifter, this Δ -Σ modulated vector phase shifter can provide quasi-continuous phase and gain control capability. According to the experimental results, the dynamic range of gain control is greater than 35.5 dB. The output reflection is lower than -10 dB through the 18-50-GHz band, and the input reflection is lower than -10 dB from 18 to 45 GHz. The phase shifter occupies 700 μm x 900 μm on 0.13-μm SiGe bipolar complementary metal-oxide-semiconductor (BiCMOS) technology, and the core size is only 400 μm x 500 μm. After digital calibration, the proposed phase shifter has achieved the highest phase and gain control precision compared with the state-of-the-art digital controlled phase shifters.

A compact dual-band Wilkinson power divider (WPD) using the via-free dual-composite right/left-handed (D-CRLH) resonators is presented for application in the Beidou navigation satellite system in this paper. First, by establishing an equivalent circuit model and using Bloch theory, a dual-band resonator is further analyzed to gain insight into its working mechanism, which can exhibit -90∘ phase shift at lower frequencies and + 90∘ phase shift at upper frequencies, respectively. Then, to facilitate the design, ignoring parasitic parameters, a simplified circuit model retaining the physical meaning is presented, and the closed-form formulas for determining lumped element values of a dual-band characteristic are derived. Next, there is a significant rejection performance between two operating frequencies due to the inherent band-stop filtering effect of the D-CRLH resonator. Following that, the WPD is verified through experiments, showing excellent performance. Finally, based on this property, a dual-band feeding network (FN) is constructed by the combination of a WPD and a phase shifter with the proposed resonator. The simulated and measured results are found in good agreement with each other, which further demonstrated our proposed design conception.

This article presents the first substrate integrated waveguide (SIW) phase shifter that can be reconfigured using liquid metal (LM). This digital phase shifter exhibits low insertion loss and is reciprocal and bidirectional. It incorporates a series of holes which can be filled or emptied of liquid metal, enabling us to add or remove via connections dynamically, on-the-fly. Using a collection of such holes, it is possible to create a wall along the E-plane or H-plane of the waveguide. When the wall is in place, it blocks the passage of energy. When the wall is absent, energy is able to flow. In this way, it is possible to guide the electromagnetic (EM) waves through one of three paths, having different electrical lengths. The result is a digital switched-line phase shifter that achieves coarse steps of phase change, from 0° up to 180°, in steps of 60°. By filling or emptying individual holes, it is possible to introduce reactive loading into each path. In this way, it is possible to achieve fine phase control in steps of 10°. Using both forms of reconfiguration in unison, the proposed phase shifter is able to deliver a phase shift of up to 180°, in steps of 10°. The proposed phase shifter operates at 10 GHz and exhibits an insertion loss of less than 2.3 dB over its entire operating band. Furthermore, the underlying concept of the proposed phase shifter can be readily scaled for operation in the millimeter-wave (mm-wave) band. The existing phase shifters operating in that band exhibit significant insertion losses. MM-wave phase shifters are expected to find application in 5G mobile access points.

This letter presents a Ka-band multilayer beaming-scanning antenna based on the electronically controlled liquid crystals (LC) phase shifter and proposes a new integrated and miniaturized LC antenna structure for the first time. The antenna is composed of four planar magnetoelectric dipole antenna units, four LC-based reflective phase shifters, and the power divider network, including the bias loading and DC blocking circuits. An external four-channel adjustable power module is designed with the field-programmable gate array (FPGA) to output the independent control and continuous adjustment of bias voltage to adjust the phase. The antenna operates at the frequency of 35 GHz and has an overall size of 35 mm50 mm2.5 mm. Measured results show that by adjusting each phase of the LC-based phase shifter through the power module, the structural and functional composite array achieves the one-dimensional scanning angle from -22 to +23 and the main lobe gain of 6.7 dBi.

This letter proposes a miniaturized wideband Butler matrix (BM) based on dual-layer half-mode substrate integrated waveguide (HMSIW) structure. By virtue of the excellent features of shorter guided wavelength, flatter in-band phase slope, and more compact size of HMSIW, simple and compact couplers and phase shifter are newly designed for BM. Finally, a BM prototype is designed, fabricated, and measured. Benefiting from the proposed structure, size miniaturization over 90% is achieved in comparison with the traditional single-layer substrate integrated waveguide (SIW) type.

A broadband balun with tunable phase-shifting function is presented in this paper. The proposed structure is based on a typical tapered balun loaded with several extra varactors. The proposed balun operates similarly to a loaded line phase shifter, in which the varactors are added between the microstrip line and ground plane. It can provide balanced feed for broadband antennas, and at the same time change the phase of the balanced feed in a cost-efficient way. It is found that range of the tunable phase shift relies on the number and variable capacitance of the varactors. To simplify the design procedure and explore the optimum performance, characteristics of a uniform microstrip line loaded with lumped capacitors are studied. It is found that gap between the capacitors and length of the microstrip line have relatively large effects on the impedance matching characteristics. According to this observation, the proposed balun is designed by applying the loaded line structure to a tapered balun. Within the frequency range of 0.8 — 2 GHz, the proposed balun loaded with two varactors achieves a tunable phase shift ranging from 17° to 61°. If the number of varactors increases to four, the range of tunable phase shift is from 41° to 161°. Finally, potential usage of the new structure for low-cost phased array is briefly discussed.

We describe the design of two broadband monolithic microwave integrated circuit (MMIC) loaded-line reflective phase shifters and their performance over the 6-12-GHz band. Lange couplers with transistor-loaded transmission-line reactive loads provide variable phase shift through reverse-bias control. A GaAs phase shifter with four diode-connected transistors in each of the two reactive loads is designed with discrete inductors to provide an increasing phase shift with frequency. A GaN reflective phase shifter uses 14 transistors in each reactive load with a goal of increasing the phase shift across the band. Measurements show continuous phase shift from 40° to 70° with less than 6-dB insertion loss over the 6-10-GHz band and from 60° to 165° with less than 8-dB insertion loss across the 8-12-GHz band for the GaAs and GaN MMICs, respectively. The power performance of the MMICs is compared in terms of large-signal S-parameters, harmonics, and IP3. The GaN phase shifter exhibits similar level of harmonic generation like the GaAs device at a 20-dB higher input power.

Three RF switches and a phase shifter are proposed using the conductive bridging random access memory (CBRAM) technique. The fabrication process is developed with the Nafion membrane on a high-resistivity silicon substrate. The equivalent circuit model is established for each memristive RF switch. The proposed switches and the phase shifter have been validated by the good agreement achieved among the simulated, measured, and modeled results. The experimental results show that the series planar switch has the ON-state insertion loss (IL) below 1.69 dB and the OFF-state isolation over 25 dB up to 10 GHz, with the actuation voltages of 6.1~7.8/-1.5~-2 V. The parallel metal-insulator-metal (MIM) switch has the small ON-state IL below 0.45 dB and the OFF-state isolation over 18.4 dB when biased with 0.8~3.7/-0.5~-0.9 V. The series MIM switch has the ON-state IL below 0.61 dB and the OFF-state isolation over 21.9 dB with 0.7~2.3/-0.5~-0.9 V. The series MIM switch shows a good comprehensive performance of low actuation voltage, good uniformity, low IL, moderate isolation, and independent control. The phase shifter is realized with four series MIM switches, which provides a phase shift of 45° ± 5° from 3.8 to 4.3 GHz with the in-band IL of 2.25 dB. Compared with the conventional RF switchable devices, the proposed devices have the advantages of nonvolatility and low power consumption. Without depending on the electron beam lithography process and high-temperature phase change, the proposed technique is promising for reconfigurable RF circuits with mass production and feasibility to various substrates.

Novel microring based optical phase-shifters on Si-photonic platforms for microwave photonic applications are demonstrated. By using an add-drop microring structure in combination with an additional multimode interferometer (MMI), pure phase modulation with an ultrahigh modulation efficiency can be realized. Comparison is made to the reference all-pass ring design with both the same radius (5 m) and coupling coefficient (: ~0.2). The demonstrated structure minimizes the residual amplitude modulation (0.9 vs. 1.8 dB) for nearly 2 phase shifting over a wide optical window (1520 to 1570 nm) at the expense of a larger insertion loss (0.06 dB) due to the additional MMI. The demonstrated phase shifter structure is implemented in a Mach-Zehnder interferometer (MZI) for further study of its dynamic and linearity performance. Under forward bias, it exhibits a low V/I(0.4 V/12.7 mA), fast rise-time (3 ns), low insertion loss (0.2 dB), low residue-amplitude-modulations (

An integrated microwave photonic (IMWP) reconfigurable mixer, phase shifter, and frequency doubler based on the silicon photonics platform is proposed and theoretically investigated in this paper. The proposed structure consists of a novel dual-drive MachZehnder modulator (DDMZM) placed in parallel with an electro-optic phase modulator (PM). The novel DDMZM is a bias-free modulator that has advantages over conventional MZMs, such as bias-free operation and tunable optical-to-carrier sideband ratio (OCSR). The proposed novel structure can be configured as an IMWP phase tunable mixer or IMWP double-balanced mixer by properly adjusting optical wavelength and choosing the proper radio frequency (RF) hybrid coupler. Besides, the proposed IMWP reconfigurable mixer has the ability to perform up-converting, down-converting, RF frequency doubling, and phase shifting. The proposed structure is theoretically analyzed and is verified by simulations.

Mode-locked lasers with low noise performance, such as low timing jitter and relative intensity noise are essential for high-precision applications. In this letter, we demonstrated a 122-MHz all-polarization-maintaining mode-locked Er-doped fiber laser based on a nonlinear amplifying loop mirror. A hybrid component integrating a wavelength division multiplexer and a phase shifter is applied to increase the repetition rate. The relative intensity noise is 0.004% and 0.76% rms (integrated from 1 MHz to 100 Hz) from two output ports. The timing jitter characteristic is measured by the delayed optical heterodyne method. The timing jitter is ~1.9 fs rms (integrated from 1 MHz to 10 Hz) of both two output ports. The origin of the timing jitter of this laser is analyzed numerically based on the well-established theoretical model using the laser’s repetition rate, cavity dispersion, etc.

A new technique to realize miniaturized broadband multiway and polyphase differential phase shifters is proposed and studied in this article. In contrast to existing designs based on coupled-line and loaded stubs, the multiway phase dispersions are controlled by susceptances of multiple resonant tanks in this work, which can well enlarge the operation bandwidth (BW) and avoid the unachievable physical sizes in strip width and coupling gap over a large phase shift range on the universal reference line topology. In addition, its phase-shift range can be highly extended by properly allocating resonant frequencies of resonant tanks in each path to be specified different values. The theoretical analysis and design formula are studied, and the synthesis method is presented to determine all circuit parameters. By virtue of the quasi-lumped element technology, the proposed multiway phase shifter can be flexibly implemented on a single-layer printed circuit board (PCB) substrate with a very compact size. For demonstration, a five-way differential phase shifter in 0°-180° range has been designed, fabricated, and tested. Over a BW of 80.4%, the achieved phase shifts are 45° ± 4°, 90° ± 5°, 135° ± 5°, and 180° ± 6.3° with low insertion loss (IL) (

A new type series inertance tube pulse tube refrigerator is introduced. It includes series cold heads. Each cold head's pulse tube connects an inertance tube as phase shifter. The acoustic power of the first pulse tube is partially used by the first inertance tube for phase shifting, while the remaining is used for generating additional cooling power. It is high efficiency with multi refrigeration temperature. A two-dimensional axisymmetric model was introduced for simulation by the commercial CFD software ANSYS Fluent. The numerical results show that it has high potential for getting higher efficiency. A protype series inertance tube pulse tube refrigerator was made and tested. Its efficiency is higher than the ordinary inertance tube pulse tube refrigerator at higher temperature range. At 232K, the efficiency is increased by 10%. The results show that it is valuable for further development.

In contrast to the popular multimode orbital angular momentum (OAM) generation method that uses uniform circular array combined with phase shifter network, time-modulated circular array (TMCA) does not require multiple radio frequency chains and costly analog devices and it requires only switches. In this article, an arbitrary-order OAM generation and beam steering method for TMCA is proposed, which incorporates the existing integer-order OAM generation and beam steering method as a special case. Furthermore, we analyze the effect of elements on–off ordering on the generation of OAM beams, and prove that sequential ordering has the lowest power consumption. Finally, the effectiveness of the proposed methods is validated through electromagnetic simulations.

In this letter, a highly compact, bidirectional, wideband 6-bit resolution passive phase shifter (PS) is presented in low-cost 130-nm CMOS technology. A compact Lange differential hybrid is designed in this letter to provide quadrature signals from the input. The compact Lange hybrid is followed by a switching matrix that generates weighted sums of the quadrature signals to cover 360° and additional controlled loss using single pole single throw (SPST) switches. The matrix consists of 12 transistors, each of which is controlled by a three-level gate voltage (0, 0.6, and 1.2 V) providing higher resolution in phase shifts. The chip achieves the state-of-the-art performance with 10-dB insertion loss across 28-38 GHz. The chip also achieves an rms gain error of 0.6 dB and an rms phase error of 3° in the bandwidth, consuming no dc power and only 0.15 mm² including baluns.

A switched‐line substrate integrated waveguide 1‐bit phase shifter is designed and measured at 28 GHz. Reconfigurability is achieved through a set of floating metallized vias whose connection to the waveguide top and bottom layers can be controlled using PIN diodes. The reconfigurable vias are used to dynamically create alternative paths having different phase delays. A three‐metal layer printed circuit board stack‐up is employed to fully integrate the diode biasing network and to ease the routing of the bias signal. The high integration of the proposed configuration makes it well suited for the implementation of reconfigurable Butler matrices. The phase shift offset between the two states of this digital 1‐bit phase shifter equals 262° at 28 GHz, leading to a measured figure of merit of 161°/dB, and input 1‐dB compression point over 20 dBm. The total area is 13.72 × 10.9 mm without feeding lines and bias.

A compact filtering phase shifter is proposed using two quarter-wavelength coupled lines, two quarter-wavelength transmission lines and two face-to-face feed lines. With such circuit model, the proposed design has the advantage of compact size and simple structure when compared with the state-of-the-art designs. Multiple transmission zeros can be obtained. Constant passband for different phase shifts can be achieved by controlling the parameters of coupled lines and transmission lines. Theoretical analysis based on even-/odd-mode method guides the design. Two prototypes with the phase shifts of 45° and 90° are designed for verifying the theoretical analysis. It’s shown that the 45° (90°) phase shifter can obtain 45° ± 2.3° (90° ± 4.3°) for the 3-dB bandwidth of 51% (51%), the phase shift bandwidth of 57% (58%), and the size of 0.5 λg × 0.01 λg (0.7 λg × 0.01 λg), where λg is the guided wavelength at the center frequency.

In this work, an all‐fibre phase shifter using tapered fibre coated with molybdenum tungsten disulfide ‐ reduced graphene oxide (MoWS2‐rGO) is demonstrated. The large evanescent field of tapered fibre allows MoWS2‐rGO to absorb injected light from a 1400‐nm pump. It subsequently modifies the refractive index of both an MoWS2‐rGO solution and tapered fibre because of the thermo‐optic effect. A maximum wavelength shift of 2.489 nm is observed and the equivalent phase shift is 0.91π. The efficiency of the phase shifter is calculated at 0.0175 nm/mW. The proposed phase shifter is beneficial for a variety of applications, specifically for future optical beam‐forming networks and all optical signal processing devices.

This article presents a new electronic device – the four-port quasi-circulating quadrature hybrid (QCQH), which combines desirable features of electronic circulators and quadrature hybrids. The QCQH comprises three quarter-wavelength transmission lines and a 90° non-reciprocal phase shifter (NRPS) and is suitable for inband full duplex applications. We derive the four-port S-parameter matrix of the QCQH and the transfer functions under termination scenarios of interest. The resulting closed-form expressions are compared with the prior art electronic circulator. A 90° transmission line and lumped transformer alternatives are considered for designing a QCQH based on a two-port N-path circuit. TX isolation and transmission expressions are derived and verified against simulations, and a new wideband leakage cancellation approach is proposed. A TSMC 65 nm CMOS N-path chip is integrated on-board with a discrete, lumped, LCL transformer implementation. TX-to-antenna insertion loss of 1.4 dB and an RX NF of 4.7 dB at the frequency of 1 GHz were measured with a primary passive TX-RX isolation of 21 dB. Total isolation of more than 50 dB for an 80 MHz OFDM WiFi TX signal employing digitally equalized active leakage cancellation was achieved along with better than −40 dB TX EVM with SIC ON.

Self-excited oscillation is a method to make a resonator vibrate at its natural frequency. This is widely used in vibration sensors such as mass sensors, atomic force microscopes and stiffness sensors. Self-excited oscillation is mainly produced by positive velocity feedback and time-delayed displacement feedback including phase-shifted displacement feedback. In this paper, we consider phase-shifted displacement feedback using a phase shifter. We perform nonlinear analysis to clarify the finite steady-state amplitude of the self-excited oscillation by considering nonlinear damping without a Laplace transform in the frequency domain, and formulate the effect of the phase shifter using an ordinary differential equation. We apply the method of multiple scales to the third-order ordinary differential equations expressing the coupling between the resonator and the phase shifter. This analytically reveals the parameter range of the phase shifter that produces self-excited oscillation in the resonator and the steady-state amplitude depending on the phase shift. We conduct an experiment using a cantilever as the resonator and produce self-excited oscillation via the feedback signal based on a phase shifter in a digital computer. The theoretically predicted characteristics of the self-excited oscillation agree well with the experimental ones.

We present a fast far-field phased array calibration/beamforming method. An improved version of the rotating-element electric-field vector (REV) method, which is used to calibrate array antennas by measuring the power received at a far-field point while varying the phase of each element, is proposed. Two major improvements were made. First, a simpler algorithm was used to determine the calibration value of the conventional REV method, without disconnecting an antenna element during the calibration process. Second, a solution for a specific case was added for a more accurate categorization to use the correct formula. This improved rotating-element electric-field vector (IREV) is experimentally verified. Curve fitting and sinusoidal regression were used to reduce the number of measurements required for fast calibration/beamforming. Arrays of a $1\times 6$ phased array system comprising a 4-bit phase shifter and a 6-bit variable-gain attenuator (VGA) were calibrated using only measurements of the far-field received power. Calibrations were performed when the horn and array antennas were perfectly aligned with each other and when the latter was tilted at an angle of 12° relative to the former.

A filtering transmitarray antenna (TAA) with high-gain in-band radiations at the $X$ -band and an out-of-band low-scattering characteristic is presented in this communication. The proposed composite TAA element consists of a dual-polarized resistive sheet, a fixed bandstop frequency-selective surface (FSS) element, and an adjustable bandpass FSS element also serving as a phase shifter. The resistive element is constructed by inserting a parallel inductor–capacitor (PLC) resonant structure into the center of a lumped-resistor-loaded metallic dipole. A transparent frequency-domain window at the center operating frequency ( $f_{c}$ ) is created by the PLC resonance and is further shared by both FSS elements, hence allowing for high in-band transmission herein. At frequencies below or above $f_{c}$ , the whole composite TAA element acts as an absorber with the bandpass or bandstop FSS elements as the ground planes for the resistive sheet, respectively. The measured results show that the composite TAA can achieve gain-filtering responses with out-of-band suppression levels ≥25 dB, ~8 dB scattering cross section (SCS) reductions in 4–7 and 14–20 GHz, and the radiation gain of 25.3 dBi simultaneously. Because of these merits, the proposed design can relieve the stress on filtering circuit designs, also offering an attractive solution in stealth technology.

A novel architecture of a digital modulated polar phased-array transmitter with phase modulation (PM) phase-shifting and feed-forward controlled dynamic matching (FFCDM) is presented in this article. Phase-shifting in a PM signal path is utilized in each element, which shares many components including a phase modulator, baseband, and IF components. The characteristics of the proposed architecture are analyzed. With a constant envelope of PM signals, the implicit nonlinearity of the phase shifter in this architecture has low impact on the linearity performance of a phased-array system. Meanwhile, low phase error can be achieved by high-resolution phase interpolation with the digital predistortion (DPD) technique. Efficiency for both saturated and 6-dB back-off power is enhanced by digital power amplifier (DPA) with FFCDM. As a proof of concept, a 3–7 GHz 4-element phased-array transmitter is designed and fabricated in 40-nm CMOS based on the proposed method. The measured root-mean-square (rms) phase error of 0.3°, effective phase shifting resolution of 9-bit, and peak system efficiency of 38.2% are achieved. For 40 MHz 64-QAM modulation signal, it exhibits EVM of 5.38% and 5.37%, $P_{\text {out}}$ of 14.30 and 14.46 dBm, and PAPR of 7.08 and 6.97 at 3.5 and 5.2 GHz, respectively. The measured peak EIRP is 35.6 dBm with a unit antenna gain of 2.98 dBi at 5 GHz. The radiation patterns with 0°, 15°, 30°, and 45° steering are measured based on monopole antennas. Meanwhile, the array achieves < 4.7% and < 5.9% EVM for 64-QAM signals with bandwidths of 20 and 40 MHz, respectively.

A high-efficiency 27–30 GHz 0.13- ${{\mu } \text {m}}$ BiCMOS transmitter front end for mobile satellite communication (SATCOM) phased arrays is presented. A system-level analysis for determining the key parameters of the RF front end for the case of a SATCOM user terminal for geostationary Earth orbit (GEO) is presented. The building blocks of the beamformer, consisting of a phase shifter, variable attenuator, and power amplifier, are fully characterized. A 360° phase shifter with an accuracy of 7 bits and amplitude error of ±1.5 dB is integrated with a variable attenuator that provides a gain variation of 16 dB with phase error of ±5°. The chip has a measured transducer gain of 23 dB and a power consumption of 45 mW at OP1dB of 10.8 dBm. The power-added efficiency (PAE) of 26.7% is measured for the entire channel at OP1dB. An error vector magnitude (EVM) of −28 dB at Pout,avg of 6 dBm and PAEavg of 12% is measured for a 400-MHz bandwidth 64-QAM modulated signal. The overall size of the chip is ${1.18} \times {2.23}\,\,\text {mm}^{{2}}$ .

A continuously tunable true-time-delay phase-shifter topology based on switchable varactor-tuned transmission lines is presented. By introducing p-i-n diodes to switch different varactor-tuned transmission lines, the phase shift tuning range can be doubled compared with the conventional design, which results in 50% size reduction. For verification, two cascaded four-unit and eight-unit microstrip phase shifters are designed and fabricated on a 0.787-mm-thick Rogers RT/Duroid 5880 substrate with $\varepsilon _{r} =2.2$ and tan $\delta =0.0009$ . The measured microstrip phase shifts of the four-unit and eight-unit phase shifters are about 107° and 191° at 4 GHz, respectively, with insertion loss of less than 2.4 and 3.6 dB. The return loss is better than 15 dB from 0.5 to 4.65 GHz for all states.

A silicon Mach Zehnder modulator (MZM) with high modulation efficiency was designed using a core-based split PN junction phase shifter. The novel design of the phase shifter improves the optical confinement, reduces the optical loss. The use of the travelling wave electrode improves the coupling between the microwave and optical mode. The proposed design achieved a high modulation efficiency of 0.75V.cm with 1.5mm phase shifter. With this modulation efficiency, an extinction ratio of 7.37dB and 1.69 × 10− 12 bit error rate was achieved at a bit rate of 90Gbps. The energy per bit transmission of the data was 3.91pJ/bit. The phase shifter in silicon MZM (PS-MZM) was analysed for its supporting transmission distance and bit rate at ITU-T recommended DWDM wavelength of 1552.5 nm. It ensures that PS-MZM is suitable for on-chip and off-chip communication data centre application in unguided (free space optics (FSO)) and guided (optical fibre) transmission medium. The proposed device can also be implemented in delay lines, switches etc.

This brief presents a 15–38 GHz vector-summing phase shifter (VSPS) with the full 360° phase-shifting range in the 65nm CMOS process. An improved wideband quadrature all-pass filter (QAF) is designed to overcome the traditional one’s capacitive loading effect and exhibits wideband I/Q performance. Analysis and comparison between the proposed QAF and the traditional one are discussed. For demonstration, a prototype VSPS with the full 360° phase-shifting range from 15GHz to 38GHz using the proposed QAF is implemented in the 65nm CMOS process. The root means square (RMS) phase and gain errors are 2°~3.5° and 0.7 dB ~1 dB from 15 GHz to 38 GHz, respectively. The power consumption is 19.2mW, and the whole chip is compact with a core size of 0.16mm2.

A reconfigurable transmitarray antenna (RTA) with 360° continuous transmission phase controlling capability is designed and experimentally validated in this letter. The proposed RTA element is based on the receiver-transmitter structure. A compact varactor-based analog phase shifter using a coupled-line structure is utilized to provide a 0° to 180° continuous transmission phase. Two PIN diodes integrated on the active transmitter patch are alternatively turned on to generate an additional 180° phase shift using the current reversal mechanism. The element simulations show a magnitude insertion loss varying from 0.95 to 1.35 dB at 5.6 GHz, and a wide 3-dB transmission bandwidth of 16.7%. A prototype composed of ${\rm{16 \times 16}}$ elements is fabricated and measured. The measured broadside gain is 23.7 dBi at the design frequency with a 3-dB gain bandwidth of 15.7%. Good two-dimensional (2-D) beam steering capability within ±60° is also experimentally verified.

A switchable dual-band dual-sense (DBDS) circularly polarized (CP) patch antenna is reported in this communication, which is implemented by dual-band phase shifter of ±90°. The proposed antenna is comprised by two annular-ring radiators, four H-shape slots, and two phase-controlled feeding networks. Four H-shape slots offer desired isolation between two paths of each feeding network, and also improve the impedance matching performance in two bands. Each dual-feed network is shared by two operating radiators, supporting simultaneous dual-band functionality. Meanwhile, the dual-band phase shifter is enabled by the folded shorted stubs that provide broadband dual-CP radiation performance. Thus, for each feeding network, −90° and 90° phase differences between two orthogonal signals can be achieved in each band, respectively, so as to meet the requirements of opposite polarizations. Two pairs of single pole single throws (SPSTs) are added in the feeding networks to acquire switchable CP characteristic, meanwhile improving the isolation between two feeding networks. As a proof-of-concept, a switchable DBDS CP antenna prototype operating at 2.45 GHz/5.8 GHz industrial scientific medical (ISM) bands is prototyped and tested with a low profile of $0.036~\lambda _{0}$ . By controlling two pairs of SPSTs, the proposed patch antenna can switch from the right-handed circular polarization (RHCP)/left-handed circular polarization (LHCP) state to the LHCP/RHCP state.

This letter presents a planar endfire Yagi-Uda antenna phased array fed by a corporate network. The phase of each radiating element is controlled by a loaded line phase shifter based on liquid crystal technology. The phase shifters are meandered to minimize the dimension of the array and are measured to provide maximum differential phase shift of 400 ${^\circ }$ with a figure-of-merit of ${54}{{^\circ }\rm {dB}^{-1}}$ at 28.4 GHz. Each phase shifter is tuned individually by applying bias voltage through high impedance chromium line together with dc blocks. The array is designed for full-range scanning in E -plane with $>\!{360}{^\circ }$ phase shifters. Measurements show that it can be steered from −40 ${^\circ }$ to 40 ${^\circ }$ by applying dc bias in the range of 0–5 V and from −50 ${^\circ }$ to 60 ${^\circ }$ with degraded patterns. The maximum gain of the phased array antennas is measured to be 4.5 dBi. The array beam is able to be fast steered within approximately 1 s.

This letter presents a differential 5-bit switch-type phase shifter (PS) that is based on a 65-nm CMOS process. This PS uses a new differential PS unit, which includes a high-pass state and a low-pass state. The strengths of this PS unit include low-phase error and low-amplitude error between two states, which can effectively improve the performance of the entire 5-bit PS. The fabricated 5-bit PS has a low average insertion loss of

In this letter, a 1-bit wideband reconfigurable unit cell for transmitarray applications in Ku-band is proposed. The unit cell consists of a Vivaldi structure (transmitting), a phase shifter, and a microstrip Yagi structure (receiving). Based on the current reversal mechanism, a pair of reverse mounted PIN diodes was introduced to obtain the required phase resolution (two phase states: 0° and 180°). The unit cell is fabricated and measured using a specific waveguide simulator. The measured minimum insertion losses are 1.58 and 1.61 dB for State I and II, respectively. The insertion loss is less than 2.58 dB (1 dB bandwidth) from 14.88 to 17.28 GHz for State I, and less than 2.61 dB (1 dB bandwidth) from 14.73 to 17.25 GHz for State II. The 1 dB bandwidth of the unit cell is about 15%. The measured phase difference remains 180°, and the maximum error is only 3.8°.

This communication proposes a convex optimization algorithm to synthesize desirable beampattern for phased array with the dual-phase-shifter (DPS) structure. In the DPS structure, dual phase shifters are combined into one beamforming weight. Compared with conventional phased array, the moduli of the weight vector are not necessarily fixed constants in the DPS structure but can be changed in a continuous interval. For this reason, we propose a method that turns the beampattern synthesis problem into a convex optimization problem. The method can be readily implemented and efficiently solved using freely accessible routines. We consider how to obtain the weight vector with two beampattern synthesis problems. The first one is to maximize the mainlobe gain (or minimize the mainlobe loss) when the notch level is determined. The second one is to minimize the notch level when the mainlobe gain (or the mainlobe loss) is determined. In both cases, we can get suboptimal solutions. Under different situations, numerical results of simulations confirm the effectiveness of the two algorithms.

In this paper, we present an optimization study for the terahertz Spoof Surface Plasmon Polariton waveguides (THz-SSPP WGs) for the first time in the literature. The optimization study employs a selection method for the optimum dimensions for the THz-SSPP WGs, which targets maximizing the insertion phase and minimizing the insertion loss levels, and hence, finding the optimum set of dimensions that result in the best °/dB performance. The method first utilizes the analytical examination of the dispersion diagram to estimate a target range of dimensions for minimum insertion loss, which is then scrutinized by numerous simulations of the THz-SSPP WGs within the selected dimension range. In order to verify the optimization method, a set of THz-SSPP WGs are designed using the proposed method, fabricated, and measured in the 0.22–0.32 THz band. The measurements result in a record-low insertion loss per unit length of 0.75 dB/mm with the optimized THz-SSPP WGs. Additionally, the utilization of the optimized THz-SSPP WGs to compose a terahertz phase shifter enables a record-high figure of merit (FoM) of 102.8 °/dB, which is the most fundamental performance measure of the terahertz phase shifters. It should be indicated that both insertion loss per unit length and FoM levels make THz-SSPP WGs superior to the state-of-the-art planar terahertz waveguides. The presented method provides the most concrete evidence for the potential of the planar SSPP WGs for the terahertz band.

The time-varying deviations of the phase shifter network (PSN) may cause significant performance degradation in the millimeter-wave (mmWave) multiuser communication system, especially when serving fast-moving users. In this letter, we propose an efficient joint real-time phase shifter network calibration and beam tracking (JRTPSNC-BT) algorithm. In each tracking period, the exploration strategy is determined according to the previously tracked beam directions. Then based on the latest observation and the historical observations, the time-varying channels and the time-varying PSN deviations are jointly tracked and updated. Simulation results show the superiority of our algorithm both in calibration error and spectral efficiency.

This paper presents new analog circuits realised using switched-capacitor technique. New phase-shifter, low-pass filter and integrator circuits are proposed employing only a single positive type cu...

The performance of a proposed cross hybrid dielectric resonator antenna (DRA) element for dual polarization configuration operating at 26 GHz for 5G applications is presented in this paper. The new cross hybrid DRA unit cell is introduced which combines a cross shape DRA with a bottom loading cross microstrip patch. This technique of a bottom loading cross microstrip patch is chosen as the tuning mechanism (varying the length of the microstrip to tune the phase) instead of changing the DRA dimensions because of their ease of implementation and fabrication. By doing so, high reflection phase range with low reflection loss performance can be obtained, which is essential for a high bandwidth and high gain reflectarray for 5G applications. The design and simulation have been done using commercial software of CST MWS. The reflection loss, reflection phase and slope variation were analyzed and compared. A metallic cross microstrip patch of varying length placed beneath the DRA to act as the phase shifter to tune the phase and give smooth variation in slope with a large phase range. The proposed cross hybrid DRA unit cell provides a high reflection phase range of 342º and 1.8 dB reflection loss. The computed results are compared with experimental results revealing reasonable agreement, thereby confirming the viability of the design.

The demand for reconfigurable millimetre-wave (mm-Wave) components based on highly anisotropic liquid crystals (LC) is higher than ever before for the UK and worldwide. In this work, 60 GHz investigation on a bespoke shielded coplanar waveguide (SCPW) phase shifter structure filled with 16 types of microwave-enabled nematic LCs respectively indicates that the patterns of the device’s figure-of-merit (FoM, defined as the ratio of maximum differential phase shift to maximum insertion loss) reshuffle from those of the characterised LC materials’ FoM (defined as the ratio of tunability to maximum dissipation factor). To be more specific, GT7-29001- and MDA-03-2838-based phase shifters exhibit the highest FoM for devices, outperforming phase shifters based on GT5-28004 and TUD-566 with the highest FoM for materials. Such a mismatch between the device’s FoM and LC’s FoM implies a nonlinearly perturbed wave-occupied volume ratio effect. Furthermore, the relationship between insertion loss and the effective delay line length is nonlinear, as evidenced by measurement results of two phase shifters (0–π and 0–2π, respectively). Such nonlinearities complicate the established FoM metrics and potentially lead to a renewed interest in the selection and material synthesis of LCs to optimise reconfigurable mmWave devices, and promote their technological exploitation in phased array systems targeting demanding applications such as inter-satellite links and satellite internet.

We report a slow-light silicon modulator that enables high-speed PAM operation without using an electrical digital-to-analogue converter (DAC). Bragg grating resonators, integrated into each arm of a Mach-Zehnder modulator, enhance the phase modulation through the slow light effect. The optical 4-level PAM signal is generated by driving directly the segmented phase shifter design with two binary signals. This modulator presents an ultra-compact footprint ( LSL-MZM = 570 μm), low energy consumption (73 fJ/bit), large electro-optic bandwidth (>40 GHz). Up to 90 Gb/s is achieved over an nm-range spectral operation bandwidth ( Δλ = 2 nm). Compared to other low-energy resonator-based modulators, such as micro-rings, this operating bandwidth confers higher stability with a potential operating temperature range of ΔT = 50 °C. We further examine the robustness of the proposed design to fabrication variations by measurements of spectral properties across the wafer. This modulator is of particular interest for applications, such as short-range data communications that require multiple compact and energy-efficient modulators on a single chip.

A compact system with multiple signal processing functions is of interest in many applications. The purpose of this paper is to present a microwave photonic structure that is capable of simultaneously realising in-phase/quadrature (I/Q) mixing and phase shifting operations. The multi-function signal processor has a simple structure and can be constructed using off-the-shelf components. It is designed to enable commercial modulator bias controllers to be incorporated into the system to provide accurate phase shift and to improve system stability. Non-ideal effects in the system that cause deviation in the two output IF signal phase difference from 90° can be mitigated by adjusting a modulator bias voltage. The multi-function signal processor is theoretically analysed and experimentally demonstrated. Its performance including two output IF signals with a quadrature phase difference, wideband operation, continuous 0° to 360° IF signal phase shift and long-term stable operation are verified experimentally.