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In this paper, high-order orbital angular momentum (OAM) vortex beams (OAMVBs) are generated using reflective metasurface. Generating high-order OAMVBs using traditional reflective metasurface methods deteriorates the radiation performance that affects the mode purity of OAMVBs. A reflective metasurface is proposed to generate the OAMVBs with l = 4 mode at the designed frequency of 6 GHz. It is revealed that the radiation performance has been improved and mode purity for l = 4 is increased 12.6% by using quarter wavelength unit cell and circular aperture metasurface as compared to the conventional metasurface at the designed frequency. Moreover, the reflective metasurface can generate the OAMVBs with l = 4 mode from 5 GHz to 7.5 GHz. The measured gain is 17.93 dBi which agrees well with the simulated gain.

In this paper, a TE340-mode substrate-integrated cavity (SIC) excited 2 x 2 slot antenna subarray with two TE210-mode SICs' loading is presented at 140 GHz in low-temperature co-fired ceramic. By using the TE340-mode SIC, the number of vias used in the feeding network and the area of the feeding network can be reduced compared to the feeding network composed of conventional TE10/TE20-mode SIW power dividers. The proposed simplified and miniaturized high-order mode SIC-based feeding network leads to lower transmission loss and fabrication cost and reduces the fabrication difficulty. Each pair of radiating slots is loaded by a TE210-mode SIC to improve the impedance bandwidth and the gain performance. For the proof of concept, an 8 x 8 antenna array is further designed and measured. The measured impedance bandwidth of the proposed 8 x 8 antenna array is 10.7% from 130.3 to 145 GHz for |S11| ≤ -10 dB. The measured peak gain is 20.5 dBi. The measured radiation efficiency is 59.2%.

This paper presents the design of a 6-bit Ku-Band phase shifter implemented in 0.13um CMOS technology. The RC polyphase filter and inductors are used as the load of a differential amplifier to achieve high gain of the phase shifter. And it can suppress the phase error of IQ signal caused by non-ideal differential signal and this function is verified by simulation. The whole phase shifter adopts the actual components based on 0.13um CMOS technology. The results show that the maximum rms phase and gain errors are 3° and 0.46 dB for 64 states at 10-20 GHz. And the maximum voltage gain exceeds 11dB at 15GHz.

In this paper, a broadband high-efficiency power amplifier (PA) with a Class-J mode matching network is proposed. The output power can be improved by employing a stacked structure, additionally, the Class-J theory provides a superior method to broaden the operating frequency range among X-band with high efficiency. And the output matching network is simplified especially, exploiting the wideband nature of continuous mode Class-J PA. The circuit is fabricated in a 130 nm standard CMOS process. The power added efficiency (PAE) is greater than 20% over the range of 8.1~11.1 GHz and reaches the maximum value of 29.7%, the power gain reaches more than 12 dB over this frequency range. The saturated output power is 20.2 dBm when the input power is 5 dBm.

In this paper, a design of a wideband vortex reflec-tarray based on Pancharatnam-Berry (PB) metasurface is proposed, which consists of 20×20 elements. The patch is composed of an I-ring inlaid with an opening ring and is printed on the surface of the substrate. The other side of the substrate consist of a foam layer and a metal ground. A 360° reflection phase is achieved under the circularly polarized (CP) incidence. The simulation results show that the vortex beam carrying $l=+2$ orbital angular momentum (OAM) mode is successfully generated from 20-40 GHz, with an OAM bandwidth of 66.6%.

A 2.5 GHz low-phase noise push-pull class-C oscillator with a high-Q film bulk acoustic resonator (FBAR) is proposed in this paper. The LC-tank of the oscillator is replaced by a high-Q FBAR to obtain low phase noise. The frame structure of FBAR is used to obtain a high-Q factor resonator. Meanwhile, in the circuit implemented with FBAR, a common-mode voltage bias network is introduced into the oscillator, to ensure all transistors work in the saturation region. The class-C oscillator active part is designed in 130 nm CMOS technology. The phase noise of the FBAR-based push-pull class-C oscillator is -120.8 dBc/Hz@10kHz, the power consumption is 0.4 mW, and the figure-of-merit (FoM) is 232.7 at 10kHz offset frequency.

A 2×2 ring-loading rectangular patch antenna array with high gain and low sidelobe is proposed and designed at 55-GHz. The antenna array consists of a H-type substrate integrated waveguide (SIW) power divider, rectangular substrate integrated cavity (SIC), and radiation elements. The radiation element comprises a ring-loading rectangular patch and a backed cavity. A wide coupling slot on the upper surface of the SIC is used to excite the patch while the longitudinal slot on the SIW couples electromagnetic waves into the SIC. The proposed antenna array achieves a low sidelobe level below 13 dB by reducing the spacing of antenna elements. Simulated−results show that 10-dB impedance bandwidth of the proposed antenna array is −19.36% (48.75-59.2 GHz) with a peak gain of 14 dBi at 59 GHz.

Millimeter-wave (MMW) frequency bands possessing of high date rate capability makes them strong candidates for future 5G networks. Due to the high path loss at millimeter-wave frequency bands, high-gain MMW antennas are indispensable for future wireless communications. How to improve antenna gain is still a challenging issue. This paper presents a few of methods to improve the gain and their antenna examples are given.

A single-layer, low-sidelobe, wideband microstrip antenna array is proposed in this paper using PCB technology. In order to overcome the problem of inherent narrow impedance bandwidth of microstrip antennas, two parasitic patches are loaded on both sides of the main radiation patch to expand the impedance bandwidth. In addition, Taylor distribution is introduced in the feeding network to reduce the sidelobe level. CPW-to-microstrip transition is introduced for probe feeding. Simulation results show that: the -10 dB impedance bandwidth is 15.5% from 21.4 to 25 GHz with a peak gain of 18.1 dBi. The simulated radiation patterns agree well with the measured ones which show -25 dB sidelobe level in the H-plane. Impedance matching performance is still under testing.

This paper presents a BAW resonator structure, including the irregular shape and the frame region at the edge of top electrode to smooth electric response and suppress spurious modes. The NRN method based on Generalized Chebyshev Filter synthesis is introduced to design a BAW ladder filter. By controlling the location of the transmission zero, a higher isolation is obtained in the proper frequency domain. Using such methodology, Band 25 Rx BAW ladder filter is obtained with an insertion loss of 1.2 dB in the passband and an isolation of 52 dB in the Tx band.

A circular polarized, dual-band radio frequency identification (RFID) reader antenna is designed to simultaneously operate at ultra-high frequency (UHF) and ultra-wide band (UWB) bands for positioning systems. The phase shifters are loaded on the Wilkinson power divider, so that the current phase difference between each two ports of the four inverted F antenna is 90°, which can achieve circular polarization on the UHF band. The circularly polarized electromagnetic dipole antenna of UWB band is composed of a pair of patches, which are two rotary symmetric shapes of the same shape as electric dipoles, and two vertical patches with the metal ground as equivalent magnetic dipoles. With a rotary symmetric structure, the design can achieve a wide 3 dB axial ratio bandwidth. The overall size of the antenna is $200\ \text{mm}\times 200\ \text{mm}\times 20\ \text{mm}$ . The simulation results show that the impedance bandwidth of the UHF antenna ranges from 0.68 to 1.4 GHz and 3 dB axial-ratio bandwidth is 44.1% (0.76-1.19 GHz). The impedance bandwidth of the ultra-wide band antenna is 59.5% (3.32 - 6.13 GHz) and it covers a wide axial ratio bandwidth ( $\text{AR}\leq 3\ \text{dB}$ ) of 71.3% (3.16 - 6.66 GHz) with a peak antenna gain of 9.6 dBi. The mutual coupling between the two ports is less than −35 dB over the two bands.

This paper presents an 8 to 12 GHz broadband power amplifier with high linearity and efficiency. Large signal linearization methods are employed to improve the linearity. Sweet point control method is adopted to reduce the intermodulation products, meanwhile the active feedback technique is used to improve the 1-dB compression point. Moreover, an improved broadband matching network is proposed to expand the bandwidth of the power amplifier. The power amplifier is designed in 130 nm CMOS process. Post simulation results show that the power amplifier has an average power gain of 10.6 dB, a max power added efficiency of 29.6%, an output compression point of 13.5 dBm at center frequency, whereas the DC power consumption is only 19.2 mW.

In this paper, a compact circularly polarized (CP) radio frequency identification (RFID) tag antenna based on the electromagnetic band gap (EBG) structure is proposed for metallic objects. The compact EBG structure is composed of two-layer patches with offset vias. By inserting square loops into the patches, a reflection phase of +100° for X-polarization and −89° for Y-polarization at 915 MHz is achieved. A novel cross-dipole antenna is designed with meander arms and modified T-matching. The simulated −15 dB impedance bandwidth of the tag antenna is 100 MHz (860–960 MHz), and its corresponding 3 dB axial-ratio (AR) bandwidth is 6 MHz (917–923 MHz). In theory, the proposed tag antenna can provide a reading distance of 5.08 m when it is mounted on the metallic surface.

A X-Band linearized low noise amplifier is presented in a 130 nm CMOS process. The modified post-distortion technique is employed to reduce the extra power consumption and improve the linearity. In this design, the LNA with an unsaturated auxiliary NMOS transistor achieves the suppression of the nonlinearity. Two-stage common source network is used to enhance the gain and achieves X-band bandwidth in the proposed LNA. With low extra 0.07 mW power consumption of the post-distortion network, the simulated results of the implemented LNA show that IIP3 has been boosted to −5~3.55 dBm in the range of 8–12 GHz. The LNA has a peak gain of 14.3 dB and a minimum noise figure of 1.86 dB. It consumes a total 5.79 mW power consumption from a 600 mV supply voltage. The total chip area is 0.69 mm2.

We discuss transmission line inductor, single coil inductor, 2.5-turn inductor and multi-layer inductor, which can be used in millimeter-wave circuits. We present a multi-layer inductor implemented in 0.13 μm one-poly and seven-metal (1P7M) BiCMOS SiGe process and propose a modified double-π model for on-chip multi-layer inductor. Self-resonance frequency (SRF) beyond 100 GHz were obtained based on the measurement results, demonstrating that the multi-layer inductor can be used for millimeter-wave applications with compact size and high inductance density.

This paper presents a quadrature voltage-controlled-oscillator (QVCO) based on transconductance linearization technique. In this design, the LC-Tank was decoupled form switching MOSFET by capacitors rather than direct connecting, and the large signal voltage cross MOSFET was decreased. This design is able to reduce the nonlinearity of MOSFET transconductance and suppress output phase noise as result. The proposed circuit draws 8.36mA from a 1.8V DC supply. The phase noise is −119dBc/Hz at 1MHz offset and the tuning range is 5% wide at a center frequency of 9.36 GHz. And the phase error between I and Q signals is at most 1.5 degree. The prototype was designed and simulated in GF 130nm CMOS process. According the simulating result of layout, this proposed QVCO attains a figure-of-merit (FoM) of 198.5dBC/Hz

In this paper, we present three different antenna arrays operating at Q-band and 140-GHz band, respectively. In the first design, a 37-GHz substrate integrated waveguide (SIW)-fed $8\times 8$ magneto-electric (ME) dipole antenna array is proposed. The radiating structures are composed of metallic posts and cavities. In the second design, a 45-GHz SIW-fed $4\times 4$ metallic cross slots loading antenna array is proposed. The impedance bandwidth and the gain have been enhanced by loading the metallic cross slots atop of the SIW slots. In the above two PCB designs, the high radiation efficiencies have been obtained by adopting metallic radiating structures loading atop of the SIW slots. In the third design, a TE 340 -mode substrate integrated cavities (SICs) excited $8\times 8$ slot antenna array is presented at 140 GHz in LTCC process. Miniaturized and low loss feeding network has been achieved by using high order mode SICs.

A new subwavelength reflective unit cell is designed and used in reflectarray to generate orbital angular momentum (OAM) waves. The metallic single layer subwavelength element consists of a cross dipole patch, four symmetric square patches and a loop patch, which is printed on one side of a substrate layer. An air layer is also inserted between metallic ground and the substrate. Size of the square unit cell is quarter wavelength at designed frequency and it achieves 360° reflection phase range. A reflectrarray is designed to generate OAM waves of mode 1 for linearly polarized feed at 6 GHz. Using the proposed subwavelength element, its far-field radiation patterns and E-field phase distribution are analyzed through CST Microwave Studio. The simulated results show that the required OAM waves are generated successfully with a maximum gain of 23.3 dBi at 6 GHz.

We present a multi-layer inductor implemented in $\mathbf{0.13} \ \mu \mathbf{m}$ one-poly and seven-metal (lP7M) BiCMOS SiGe process. Self-resonance frequency (SRF) beyond 100GHz and high quality factor (Q) were obtained based on the measurement results, demonstrating that the multi-layer inductor is suitable for millimeter wave applications. Meanwhile, a modified equivalent circuit model for the multi-layer inductor is introduced. A multilayer perceptron (MLP) feedforward artificial neural networks (ANNs) is presented, which has been designed for computationally electromagnetic (EM) simulation and applied to predict the inductance characteristics.

A new substrate integrated coaxial line (SICL) is proposed at 45 GHz for low loss and small size. The insertion loss of designed transmission line is less than 0.2 dB. Then, a high gain cavity-backed antenna array based on the SICL structure is proposed for Q-band applications. The antenna array consists of $1\times 4$ cavity-backed patch antenna array, T-junction power divider based on SICL, and SICL to ground coplanar waveguide (GCPW) transition. The -10 dB impedance bandwidth is 11.44 GHz (25.42%). The gain is 15.8 dBi at 45 GHz.

A broadband multimode orbital angular momentum (OAM) four-feed circular patch antenna at 6 GHz is proposed in this study. The OAM antenna exhibits 5.8-dBi maximum gain, has an impedance bandwidth of 25% over the frequency range 5.2-6.7 GHz with more than 10-dB return loss. Additionally, the OAM modes + 1, -1 and OAM modes +2, -2 can be generated from 5.2 to 6.5 GHz, whose mode purity is much better than the previous two-feed configuration.

In this paper, we proposed a novel broadband TE 10 mode to TE 20 mode power divider based on low-temperature co-fired ceramic (LTCC) technology. Simulated results show that the -15dB bandwidth is about 29% from 53.7 to 72 GHz. This power divider can be used in antenna feeding network, filters or any other passive component design based on SIW structure in millimeter-wave regime.

A two-dimensionally scanning (2D) antenna array and polling beam scanning antenna array is designed in UHF RFID system with high stability and reliability in metal environment. The two-dimensionally scanning (2D) antenna array is composed of 3×3 antenna array, a feeding network and switches. The measured -10dB impedance bandwidth is around 30MHz. The scanning beam directions covers ±60° and scanning direction gain is 9~10dBi, respectively. The polling beam scanning antenna array is composed of three 1×2 planar inverted-F antenna (PIFA) arrays and polling beam scanning feeding network consisting switch and control module. The measured bandwidth is 50MHz (895–945MHz) under the condition of VSWR less than 2, covering Chinese, Canadian, Korean, and Australian standard of frequency ranges. The steering radiation pattern is -20°, 0°, and +25° in xoz-plane. The read rate achieve 100% in the metal environment.

In this paper, a novel low-profile substrate integrated magneto-electric (ME) dipole Antenna with structure-folded magnetic wall is proposed to reduce the thickness of a magneto-electric (ME) dipole. A hat-type structure loaded on $\pmb{\Gamma}$ -shaped probe is designed for impedance matching. In order to integrate with the chip, ground coplanar waveguide (GCPW) to r-shaped probe transition is designed at the bottom layer of the antenna. By employing the folded magnetic wall, the height of the ME dipole antenna is reduced to $\mathbf{0}. \mathbf{064}\pmb{\lambda}_{\mathbf{0}}$ (where $\pmb{\lambda}_{\mathbf{0}}$ is the wavelength of 4 GHz). Simulated and measured results show that the proposed antenna operates from 3.73 to 4.55 GHz. Symmetrical and high front-back-ratio radiation pattern is achieved with a stable gain of 5.9 dBi across its operation bandwidth.

In this paper, a circular polarized reflective phase-shifting surface which consists of 20×20 elements is designed to generate orbital angular momentum (OAM) waves at 6 GHz. The phase-shifting surface is composed of a substrate with split-rings printed on the top surface, an air layer and a metal ground. Using proposed reflective phase-shifting surface, OAM wave with mode 1 is achieved and its phase and magnitude distributions of E-fleld in far field are analyzed. The results show that the OAM beam purity of the reflective beam with mode 1 can reach around 96%, and the maximum gain is 22.0 dBi at 6 GHz.

A high gain W-band air-filled H-plane horn antenna is designed and fabricated using low-cost PCB technology. The antenna consists of 4 substrate layers. A portion of the dielectric substrate is removed from the middle two layers to form a hollow horn. A rectangular-slotted dielectric load is added at the end of the antenna providing 4 dB gain enhancement, as well as better impedance matching. Measured results show that the impedance bandwidth is wider than 18 GHz(85–103 GHz) and a peak gain of 15.5 dBi at 97.5 GHz is achieved.

A 4×4 low temperature co-fired ceramic (LTCC) antenna array working at 140ghz is proposed, with a high gain of 19.2 dBi at 140 GHz and a bandwidth of 8.7 GHz from 136.9 GHz to 145.6 GHz for S11 less than −10dB, which has a small antenna dimension of 6.5×12 mm2. The antenna element is a ring-loaded patch antenna with a SIW cavity backed. It can achieve a high gain of 9.5 dBi at 140 GHz. A substrate integrated wave-guide (SIW) power-divider and a transition from SIW to waveport are designed to form the 4×4 array.

This paper proposes two low-profile and high-gain array antennas with broad bandwith at 140GHz. The two antennas compose of the same subarray unit. 32 × 32-element array shows more than 38.7dBi gain with 92% efficency at center frequency and 21.5GHz bandwith(129.3–150.8GHz) and 64 × 64-element array shows more than 43.9dBi gain with 74.6% efficiency at center frequency and 20GHz bandwith(130.0–150.0GHz), respectively. The antennas will be divided into 3 layers for fabrication using milling technology.

In this paper, a high gain orbital angular momentum (OAM) antenna operating at C band is presented. High gain OAM antenna consists of Chebyshev synthesis antenna array loading with Fabry-Perot cavity which is designed to enhance gain and decrease side-lobe, and the splitting spiral phase plate (SPP) aiming to generate an OAM beam with mode l=±2. The OAM antenna achieves a directivity of 16.4 dBi in E planes, and an impedance bandwidth of 44.2% with SWR≤2 from 5.9GHz to 8.1GHz. The side-lobe level of antenna is −19dB. Compared with other multimode SPP antenna, the demonstrated antenna not only has higher gain and wider bandwidth but also possesses the lower side-lobe level characteristics.