Search

This paper presents four compact lumped-element Wilkinson power combiners (WPC) operating at 5 GHz in 28-nm bulk CMOS. To minimize the chip area, the inductances in the designs are implemented using mutually coupled coils. Two designs use star inverting coupled coils (SICC), while the other two employ delta noninverting coupled coils (DNICC). One of the two SICC-based designs (and similarly for the DNICC-based designs) incorporates a second harmonic (2f0) trap to lower the total harmonic distortion and reduce the required inductances by 25%, further reducing the circuits footprint. A design methodology for effectively exploiting the mutual coupling and nullifying the coupling parasitics is presented. The coupling parasitic in the DNICC-based design is exploited to provide the WPC isolation resistance, resulting in a lumped-element WPC requiring only three components: a coupled coil and two capacitors. The measurement and simulation results are presented to confirm the theory validity. The SICC-based WPC with an area of 0.13 mm2 achieved input return losses (RL) >17.5 dB, output RL > 11.8 dB, isolation >11.2 dB, and insertion losses (IL) <1.5 dB across 3.5–5.4-GHz frequency range. Its variant with a 2f0 trap achieved, from 3.5–5.35 GHz, input RL >18.2 dB, output RL >11.6 dB, isolation >11 dB, IL <1.4 dB, and peak 2f0 rejection of 18 dB at 10.2 GHz in an area of 0.13 mm2.The DNICC-based WPC with an area of 0.11 mm2 achieved input RL and isolation >10 dB, output RL >15.3 dB, and IL <1.2 dB across 4.1–5.45-GHz frequency range. Its variant with a 2f0 trap achieved, from 4.3–5.3 GHz, input RL and isolation >10.1 dB, output RL >14.6, IL <1.2 dB, and peak 2f0 rejection of 23 dB at 10.4 GHz in an area of 0.09 mm2. [ABSTRACT FROM AUTHOR]

This paper presents, to the best of the authors’ knowledge, the first realizations of the Gysel-type power combiner/divider in ridge waveguide technology with two different configurations. Gysel combiners exhibit wider bandwidths than traditional combiners, while offering compact designs when implemented in ridge waveguide, compared with traditional waveguide combiners. In addition, Gysel combiners provide relaxed requirements on the power handling capability of the terminating loads in the case of fault conditions, which may result from imbalance between different inputs. The ridge waveguide designs offer better power handling capabilities, especially in comparison with planar designs. These advantages are shown with two different realizations, in top–bottom and side-by-side configurations, exhibiting very wide bandwidths while occupying very compact volumes. These two designs have been simulated, fabricated, and tested. Excellent test results have been obtained, confirming the validity of the concept. [ABSTRACT FROM AUTHOR]

Abstract Power combustion systems have the potential for thermoacoustic instabilities, with many possible detrimental results. The present study experimentally investigates effects of the distribution of various heat sources on a Rijke tube. An electrical heater was designed to realize different tangential distributions of heat release by changing the spacing of the heating element. The experimental results showed that an optimum spacing exists to minimize the starting power of thermoacoustic oscillation and growth rate, and to maximize FFT amplitude. The oscillation frequency changed slightly with a different tangential distribution of heat release for different air flows. Numerical simulation was performed using the CFD method to obtain temperature and flow field distribution of the Rijke tube with different spacing of the heating element. The numerical results showed that a large high temperature and high speed region, forming immediately and simultaneously behind the heater, are conducive to thermoacoustic oscillation. [ABSTRACT FROM AUTHOR]

A new kind of multiport power-combining patch antenna in multiple polarization states is proposed in this paper. The proposed antenna consists of a ground, a stacked patch, and a driven patch fed by four centrally symmetric ports. Based on the S-parameter analysis of the multiport antenna, six polarization states (0°, 90°, 45° linear polarization, and left-handed and right-handed circular polarization) with stable reflection coefficients and radiation pattern can be realized by controlling the input phases of four ports. In this way, it is not necessary to use extra feeding network to realize the multiple polarization states. Moreover, in addition to radiating electromagnetic energy just like conventional antennas, the proposed multiport antenna can also realize on-antenna power combining without the need of power combiner. As a result, the losses and size caused by extra power combiner and feeding network can be avoided. For verification, the four-port patch antennas in different polarization states are designed and compared. Moreover, a four-port antenna integrated with four power amplifiers is fabricated and measured. The results show that both on-antenna power-combining and multiple polarization states can be realized without the need of power combiner and polarization feeding network. [ABSTRACT FROM AUTHOR]

A microwave power combining system based on four 20-kW hybrid injection-locked magnetrons in the S-band was proposed and presented. A high-power-capacity power combiner was designed, and the behaviors of the hybrid injection-locking magnetrons were qualitatively explained. An excellent output amplitude stability of 0.01 dB (peak-to-peak), a phase stability of ±0.9° (peak-to-peak), and a spur suppression ratio of −65.0 dBc at 500 kHz were achieved when the injection ratio was 0.07. The proposed four-way 20-kW magnetron coherent power combining system exhibits a total output power of over 60.6 kW and a combining efficiency of 91.5%. Simultaneously, neither real-time automatic phase tuning processes nor high-isolation circulators are required in the system. The results show that a high-efficiency magnetron power combining system has the potential to be applied as a cost-effective high-power microwave source for industrial applications. To the best of the authors’ knowledge, a microwave power combining system featuring four 20-kW S-band continuous wave magnetrons has been successfully testified for the first time. The power output of over 60.0 kW and combining efficiency of 91.5% set a new performance record for S-band magnetron power combining systems and represent the best phase noise performance reported for any injection-locked magnetron with an output power of over 15 kW. [ABSTRACT FROM AUTHOR]

Abstract This work presents an analytical and experimental study of LINC power amplifier where an unmatched Wilkinson combiner is used at the output of two class-B amplifiers. This combiner is called unmatched because of the elimination of the one hundred ohms resistor from its input. This resistor is used to guaranty a good impedance matching between the combiner and the amplifier outputs. An amount of reflection coefficient can be presented at the input of the combiner depending on the signals phase different of the two LINC branches which that may damage the linearity of the amplified signals. Our Analytical study in this paper presents equations for the power efficiency and the signal linearity showing that despite of reflection between the combiner and the amplifiers, very good efficiency and linearity will be obtained. An ADS simulation and experimental work of the LINC system is performed shows an excellent agreement with the analytical study. [ABSTRACT FROM AUTHOR]

The design of a two-dimensional spatial beam-combining network employing a parallel-plate superconducting waveguide filled with a monocrystalline silicon dielectric substrate is presented. This component uses arrays of magnetically coupled antenna elements to achieve high coupling efficiency and full sampling of the intensity distribution while avoiding diffractive losses in the multimode waveguide region. These attributes enable the structure’s use in realizing compact far-infrared spectrometers for astrophysical and instrumentation applications. If unterminated, reflections within a finite-sized spatial beam combiner can potentially lead to spurious couplings between elements. A planar meta-material electromagnetic absorber is implemented to control this response within the device. This broadband termination absorbs greater than 0.99 of the power over the 1.7:1 operational band at angles ranging from normal to near-parallel incidence. The design approach, simulations and applications of the spatial power combiner and meta-material termination structure are presented. [ABSTRACT FROM AUTHOR]

A compact broadband quasi-planar rectangular ring cavity (RRC) power-combining amplifier is presented. To realize the broadband impedance matching, high assembly precision, and the strong coupling between the RRC and the output ports, the novel inserted ground waveguide probe structure was proposed. The measured insertion loss of the passive power combiner is increased from 0.6 to 1.7 dB at the bandwidth 6.5-14.2 GHz. The measured small-signal gain of the four-device power-combining amplifier is 22.2-26.7 dB over a broadband from 8 to 14 GHz. The measured maximum output power at 1-dB compression is 37.7 dBm at 11.4 GHz, with a power-combining efficiency of about 89%. The measured results of the passive power combiner agree with the simulated ones closely. [ABSTRACT FROM AUTHOR]

Abstract: In this article, a modified two‐way Gysel power combiner, which has second harmonic control and internal matching characteristic, is implemented to reduce the overall circuit size. Further, we proposed a generalized mathematical method for N‐way design, as an extension. The modified two‐way Gysel power combiner is implemented to have fundamental input impedance of 33.1 + j13.4 at 2.1 GHz and second harmonic of 4.5–j23.7 at 4.2 GHz to achieve the return loss of −41dB. To verify the mathematical method of the modified N‐way power combiner, it is applied to a four‐way Gysel power combiner, and the simulated return loss of −41.67 dB and isolation of −50.43 dB validated the proposed design method. [ABSTRACT FROM AUTHOR]

Design, fabrication, and measurement of a metal-contact radiofrequency (RF) microelectromechanical systems switch with a power divider/combiner structure for high power applications are presented in this work. The multi-contact switch with parallel cantilever beams is implemented in a Y-junction power divider/combiner, which suppresses the uneven current distribution through each contact and results in higher power handling capability at high frequency. The measurement results indicate the excellent RF performance of the switch fabricated on the Borofloat glass substrate with insertion loss and isolation of 0.22 dB and 29 dB@10 GHz, respectively. A lumpedelement model is developed and it fits well with the measured S-parameters with the contact resistance of 0.6 Ω and up-state capacitance of 1 fF for each contact. The switch can handle power up to 2 W@10 GHz under prolonged hold-down conditions for 2 h. The reliability measurement shows that the packaged switch can operate for over 1 million cycles at 200 mA under cold-switching conditions. [ABSTRACT FROM AUTHOR]

In this study, the authors investigate the issue of pilot power allocation in multi-cell multi-user massive multiple-inputmultiple-output (MIMO) systems to maximize the sum rate. In contrast to conventional scheme that assigns equal pilot power for all users in the system, they assume that different users can be assigned different pilot powers while the total pilot power per cell is fixed. They show that when the number of BS antennas goes to infinity, the signal-to-interference-and-noise ratio of a user only depends on the large-scale fading and pilot power of users who have the same pilot sequence. From that they derive an optimization problem to maximize the total uplink achievable rate of a target cell and prove that this problem is convex, which can be solved by the well-known Lagrange multiplier method. They also propose an extended optimization problem that solves the issue of zero-pilot power in the original problem. Eventually, two algorithms corresponding to the original and extended optimization problems are proposed to obtain the optimized pilot power set for all users in the systems. Numerical results show that the proposed algorithms outperform the existing methods relating to pilot power allocation problem as well as conventional scheme. [ABSTRACT FROM AUTHOR]

Nonlinear transmission lines (NLTLs) are one of the most prominent solid-state sources of high-power RF pulses. However, there is no integrated mathematical basis, which predicts adequately the generated waveforms on an NLTL and those delivered to the load. This analysis is required for designing and optimizing these transmission lines. Most works in this area are related to experimental studies and results. In this paper, we have developed a theoretical basis, which predicts all the required characteristics of the generated RF pulses on a lossy NLTL. The RF amplitude, the maximum voltage, and the central frequency of the generated pulses at each node of an NLTL are formulated. All the obtained formulas were verified by SPICE simulations and experimental measurements. The comparisons made with the data obtained from the reported experimental studies of the other researchers in this field reinforce these analytical results as well. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate a three-stage all-fiber master oscillator power amplifier (MOPA) system emitting over 40 W of continuous-wave (CW) output power at ~1.5 µm. The setup utilizes three self-fabricated high-power passive fiber components: a mode-field adaptor (MFA) and two types of pump and signal power combiners. Their development allowed us to become independent from commercially available components, which are often incompatible with fibers used in the experimental setups, resulting in additional losses. A power combiner with single-mode (SM) signal fibers in a configuration (5 + 1) × 1 was used in the second stage of the MOPA system, which was based on an SM Er–Yb co-doped double-clad (DC) fiber. The fabricated MFA was used to connect the second amplifier stage based on SM fibers with the third amplifier stage based on large-mode-area (LMA) fibers. In the third stage of MOPA system, based on Er–Yb LMA DC fibers, we used the fabricated power combiner based on LMA-type signal fibers in a configuration (6 + 1) × 1. The presented three-stage MOPA system, utilizing self-fabricated high-power passive fiber components, enables amplification of an input signal of 10 mW up to 44 W of the CW power at the wavelengths of 1555 nm and 1563 nm, corresponding to a gain level of approximately 36.4 dB. [ABSTRACT FROM AUTHOR]

A compact single-stage 8-1 Gysel Combiner in planar technology for operation with 352-MHz pulses with peak output power of 10 kW has been designed, manufactured, and tested. The module has 0.2-dB insertion loss when operated at nominal power, and the return loss of all ports is 20 dB or better. The module was operated using 3.3-ms pulses at 14-Hz repetition rate without any signs of degradation, thermal heating, or arcing. The new design makes use of inclusions of weakly coupled lines in the common point section of the Gysel combiner. It is possible to adjust port imbalances caused by parasitic line coupling in the system for optimum performance at a given frequency by adjusting the coupling. [ABSTRACT FROM PUBLISHER]

In this paper, the design methods for four-way power combiners based on eight-port and nine-port mode networks are proposed. The eight-port mode network is fundamentally a two-stage binary four-way power combiner composed of three magic-Ts: two compact H-plane magic-Ts and one magic-T with coplanar arms. The two compact H-plane magic-Ts and the magic-T with coplanar arms function as the first and second stages, respectively. Thus, four-way coaxial-to-coaxial power combiners can be designed. A one-stage four-way power combiner based on a nine-port mode network is also proposed. Two matched coaxial ports and two matched rectangular ports are used to provide high isolation along the E-plane and the H-plane, respectively. The simulations agree well with the measured results. The designed four-way power combiners are superior in terms of their compact cross-sectional areas, a high degree of isolation, low insertion loss, low output-amplitude imbalance, and low phase imbalance, which make them well suited for solid-state power combination. [ABSTRACT FROM PUBLISHER]

An iterative procedure of distribution of power division coefficients in two-channel partial Wilkinson power combiners-dividers forming a multichannel beamforming network (BFN) of antenna arrays (AAs) is proposed. Examples of implementation of 24- and 32-channel BFNs for an AA with cosecant shape of the radiation pattern are presented. [ABSTRACT FROM AUTHOR]

Demand response cannot only be used as a power supply resource to produce a negawatt in high power prices or when the reliability of the grid is threatened, but can also be applied to resolve a transmission expansion planning problem instead of implementing a costly and complex transmission upgrade solution. Essentially, the demand response resources (DRRs) can relieve the capacity requirement for a load area, and thereby relieve the import transmission requirement. This paper explores the role of DRRs as an alternative solution to the required transmission upgrades in the context of a proposed capacity market modeled based on Pennsylvania–New Jersey–Maryland (PJM) capacity market model. Numerical results show that the DRRs can indeed replace the needed transmission upgrades. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a novel architecture of power combiner based on a distributed amplifier topology is proposed for 60 GHz phased‐array antenna systems. A multi‐input single‐output power combiner is constructed by removing the input transmission lines of a distributed amplifier, the input signal delays are equalized by adding input delay/matching networks so that the amplified input signals are added constructively at the combiner's output. Fabricated in 65 nm CMOS process, measured results show a maximum insertion loss of 1 dB, and input/output reflections losses of better than 12 dB over the entire band of 57 GHz to 64 GHz while consuming 67 mW (56 mA) from a 1.2V DC supply. [ABSTRACT FROM AUTHOR]

In this study, a four-way power combiner using four equally designed 2-way power combiners is introduced. The physical structure of the combiner is such that the components and connections are symmetrically arranged. In the final section of the power combiner, two 2-way combiners are connected in parallel, which helps for easier circuit alignment and better electrical properties. The 2-way power combiner is the building block of the 4-way power combiner. The 2-way power combiner is analysed by even and odd method and its performance is verified by measurements. The analysis method can be extended to 4-way or N-way power combiners. The proposed 4-way power combiner is fabricated and its performance is measured. The amplitude imbalance of the 4-way power combiner is <0.2 dB in the path between the input ports and the summing port. The attenuation above the theoretical 6 dB insertion loss is 0.5 dB from 30 to 500 MHz. The 4-way power combiner has the same performance as the 2-way power combiner, regarding the added insertion loss above the theoretical ideal value. Ease of fabrication, simple circuit connections and use of equally constructed 2-way power combiners result in repeatability and reduce electrical mismatch. [ABSTRACT FROM AUTHOR]

Power combiners are in general complex to manufacture and do not show a compact structure when more than two output ports are needed. To overcome these problems, the design of a five-way Bagley polygon in rectangular waveguide is presented. The proposed geometry is simple, suitable for an efficient optimization, and allows its fabrication by milling. A five-way Ku-band $E$ -plane rectangular waveguide Bagley polygon for a 17% fractional bandwidth is designed, manufactured, and measured. The measured results show return loss better than 28 dB and amplitude and phase imbalances below ±0.2 dB and ±5°, respectively, which, along with the waveguide low losses, leads to a 98% efficiency as power combiner. [ABSTRACT FROM PUBLISHER]

This paper revises the efficiency optimization equations for magnetic-transformer-based power combiner/ divider impedance transformation networks (e.g., distributed active transformer). It evaluates their usability for high millimeter-wave frequencies, where the distributed behavior of a transformer and its loss become relevant. As is demonstrated, the standard optimization equations do not lead to an optimum result. To enable the optimization of distributed transformers, an extended lumped equivalent circuit model is proposed and used for the derivation of new optimization equations. The novel equations enable the design of magnetic transformers with maximum efficiency. To demonstrate the performance that can be achieved with optimized distributed magnetic transformer networks at millimeter-wave frequencies, measurement results of an R-band (i.e., 170–260 GHz)/H-band (i.e., 220–325 GHz) power amplifier (PA) are presented. With an output power of approximately 6.2 dBm at 260 GHz, the amplifier is among the state of the art for mHEMT PAs operating in this frequency range. With its relative 3-dB bandwidth of 29%, however, it surpasses all those reported mHEMT PAs to date. [ABSTRACT FROM AUTHOR]

This paper describes a terahertz spatial power combiner based on a periodic hole-shaped hologram for a two-dimensional (2D) horn antenna array. The combiner consists of a 2D array of rectangular horns, a dielectric hole-shaped hologram, a focusing reflector, and a receiving horn antenna. The hologram is realized as 2D periodic holes, which transforms the beams of the antenna array into a pseudoplane wave. The transformed wave is coupled into a rectangular output horn antenna by a parabolic reflector with a shaped surface relief. The field distribution on the receiving plane can be obtained by using a nongradient optimization method to optimize the reflector surface. An example operating at 300 GHz is described. The theoretical power combining efficiency is about 63.1%. The computed field distribution agrees well with the result obtained using the commercial software FEKO Suite. [ABSTRACT FROM AUTHOR]

Multi-way, radio frequency (RF) and microwave power combiners and dividers (splitters) are important components of rapidly developing high power RF and microwave systems used in radars, communication, directed energy, air traffic control, and scientific facilities such as particle accelerators. Several 21-way L-band combiner configurations of a reactive-radial type with enlarged bandwidth, reduced dimensions for high power applications are analyzed numerically: with smooth air gap, solid dielectric filling, and air gap with wiggling radial walls. The last example employs slow waves enabling size reduction and offers significant increase of bandwidth up to an octave and above at low insertion losses. [ABSTRACT FROM AUTHOR]

This study describes a new low-profile broadband circularly polarised (CP) antenna. The antenna comprises a directly fed CP patch of new configuration that excites four square parasitic patches in an upper layer and an L-shaped parasite alongside the excited patch. This arrangement provides an improvement in axial ratio (AR) bandwidth over existing configurations, having an impedance bandwidth of 38% (return loss > 10 dB), with an AR bandwidth of 28.1% (AR < 3 dB) and a peak gain of 8.4 dBic. [ABSTRACT FROM AUTHOR]

This study presents a broadband four-way power combiner/divider for very high frequency (VHF) to ultra-high frequency (UHF) bands using 0° hybrids and impedance transformers based on transmission lines. The 0° hybrids were used as in-phase power combiners or dividers, and 1 : 4 impedance transformers were adopted to transform the impedance so that all input and output ports had a 50 Ω impedance. Each component was analysed using equivalent circuits. The overall size of the implemented four-way power combiner/divider module was 110 × 163 mm2. Based on the measured S-parameters, an ultrabroad bandwidth from 8.0 to 600 MHz was achieved with an insertion loss <1.0 dB, reflection coefficients below -10.0 dB, isolation among the ports less than -15.0 dB, and magnitude and phase imbalances less than ±0.1 dB and 0.5°, respectively. [ABSTRACT FROM AUTHOR]

In this study, a new technique is introduced for full power combining in distributed amplifiers which contain multiplicative gain stages. Produced powers from middle stages of multiplicative structures are always wasted in terminating resistors. This study shows that an electrical funnel can be used to combine all produced powers from all stages. To do so, two configurations are considered to terminate middle stages with transistors. It is shown how a typical distributed amplifier can be converted to a two-dimensional distributed amplifier (2D-DA). Analytical expressions for gain calculation are also presented. All inductors and connections of 2D-DA are simulated by advanced design system (ADS) electromagnetic simulator with TSMC 0.18 CMOS layout specifications. Post-layout simulation results show the trueness of the presented relations. The designed 2DDA shows 17.4 dB gain along 0.7-25.7 GHz bandwidth by consuming 75.2 mW DC power. More than 3.9 dBm output power at 1 dB output compression point (OP1dB) is achieved and the noise figure of the 2D-DA is between 3.6 and 6.4 dB. Using 2D-DA, produced powers from middle stages participate in the outgoing power. This helps to improve gain bandwidth (GBW), power added efficiency (PAE) and OP1dB by 84.3, 143 and 86%. [ABSTRACT FROM AUTHOR]

In this study, a new technique is introduced for full power combining in distributed amplifiers which contain multiplicative gain stages. Produced powers from middle stages of multiplicative structures are always wasted in terminating resistors. This study shows that an electrical funnel can be used to combine all produced powers from all stages. To do so, two configurations are considered to terminate middle stages with transistors. It is shown how a typical distributed amplifier can be converted to a two-dimensional distributed amplifier (2D-DA). Analytical expressions for gain calculation are also presented. All inductors and connections of 2D-DA are simulated by advanced design system (ADS) electromagnetic simulator with TSMC 0.18 CMOS layout specifications. Post-layout simulation results show the trueness of the presented relations. The designed 2DDA shows 17.4 dB gain along 0.7-25.7 GHz bandwidth by consuming 75.2 mW DC power. More than 3.9 dBm output power at 1 dB output compression point (OP1dB) is achieved and the noise figure of the 2D-DA is between 3.6 and 6.4 dB. Using 2D-DA, produced powers from middle stages participate in the outgoing power. This helps to improve gain bandwidth (GBW), power added efficiency (PAE) and OP1dB by 84.3, 143 and 86%. [ABSTRACT FROM AUTHOR]

This paper presents discrete active combiners and dividers for ultra-wideband (UWB) applications. The proposed solution exploits distributed amplifier techniques to perform the combination and division of signals over the band from 0.5 to 20 GHz. Three circuit boards are demonstrated: a 2-to-1 active combiner with 17-dB gain, a 4-to-1 active combiner with 30-dB gain, and a 2-to-1 active divider with 10-dB gain. Standard S-parameter and large-signal measurements have been performed to characterize the presented circuit. Multi-antenna demonstrators have been setup to validate the device functionality in more complex scenarios. In particular combination of wideband and narrowband communications has been demonstrated, as well as the use of the combiners for UWB antenna arrays. The presented 4-to-1 combiner shows the best values in terms of gain and a number of inputs with respect to the state-of-art (SOA), while the performance of the other presented devices is comparable to the SOA despite using SMA connectors in place of on-chip measurements. [ABSTRACT FROM AUTHOR]

Time modulated array (TMA) suffers from relatively low efficiencies due to the power absorption in switches during off state. In this paper, we present the design of a novel TMA by using a reconfigurable power divider/combiner (RPDC) for improving the array’s efficiency, where the power absorbed during off state can evenly be transferred to other array elements during on state. An improved pulse sequence strategy is developed to control the radiation pattern of the TMA with RPDC. The impact of the RPDC on radiation features of the TMA is further discussed. To experimentally verify the feasibility of the proposed design, a six-element TMA with RPDC is constructed and characterized. Compared with a six-element conventional TMA with single-pole single-throw switches, the TMA with RPDC shows a significant enhancement of gain by 0.98, 1.27, and 1.65 dB when the sidelobe levels are −20, −25, and −30 dB, respectively. [ABSTRACT FROM PUBLISHER]

In this paper we demonstrate our concept and fabrication details of a (5 + 1) × 1 pump power combiner with signal feed-through. The (5 + 1) × 1 configuration is based on a feed-through signal fiber with reduced clad diameter in comparison to multimode fibers (MMFs) used in the combiner. Our idea is to use a 9/80 μm signal fiber and five conventional 105/125 μm MMFs. Using this number of MMFs with 125 μm clad diameter and signal fiber with 80 μm clad diameter allows for easy placement of all fibers in proper position in a capillary tube – the signal fiber is always in the central position, surrounded by the MMFs. It also enables reducing the taper ratio parameter, and thus increase the signal transmission efficiency. Using this approach, signal transmission at the level of 94.3% was achieved, which is better than typical values offered by commercially available singlemode devices. [ABSTRACT FROM AUTHOR]

This paper derives a novel continuum of Doherty power amplifier (PA) solutions with enhanced load modulation over an extended RF bandwidth. It is analytically shown that Doherty PAs with efficiency peaks at maximum power and at an arbitrary back-off level can be achieved with numerous configurations of output power combiner. Generalized governing equations for carrier and peaking transistor current ratios, voltage profiles, and biasing conditions are derived in order to assess the performance of any Doherty amplifier configuration. The generalization demonstrates the impact of the selection of the output combiner on PA performance and highlights the tradeoffs between the different solutions. A wideband Doherty PA was designed based on the proposed methodology and implemented using packaged gallium nitride transistors. Over the frequency band of 0.55–1.10 GHz, the Doherty PA exhibited drain efficiency in excess of 40% and 56% at 6-dB output power back-off (OPBO) and peak power, respectively. The Doherty PA was successfully linearized when driven with modulated stimulus and achieved average drain efficiency above 40% at 7.1-dB OPBO. [ABSTRACT FROM PUBLISHER]

This paper proposes an adaptive combiner model that maximizes the performance of multi-rate cooperative relaying transmission in resources aware systems. Users' cooperation is applied to smartly profit from the network resources to reach for efficient multi-rate transmissions. The low rate terminal uses a part of his bandwidth and power to relay the high rate user data side by side with his own data. This results in small performance degradation to the low rate user performance. The combiner model at the high rate terminal is carefully investigated for an optimized system performance and an adaptive combiner is proposed. The model calculates the weights adaptively for each bit based on a dynamic-blind method. The adaptive combiner is evaluated against the maximal-ratio combiner MRC and the equal gain combiner EGC to reach for the best model for the multi-rate relaying framework. Based on half-duplex mode, the probability of error performance is studied and compared for each combiner model under different channel conditions. The results show that the proposed adaptive combiner, characterized by its reliability and simplicity, leads to the best performance compared to the other models. [ABSTRACT FROM AUTHOR]

A power divider/combiner using half-mode substrate integrated waveguide (HMSIW) and microstrip transmission lines with high isolation for high-power applications is presented. The design consists of a planar cavity, two 90° microstrip transmission lines, two matched loads, and one 180° microstrip transmission line. The cavity is fabricated using HMSIW structure and excited the TE101mode at the centre frequency of 4.875 GHz. The external microstrip transmission lines and matched loads are added to improve the isolation between output ports. Moreover, the matched loads prevent the appeared heat loss in the substrate. The circuit behaviour is analysed based on the even and odd mode techniques, and the structure is simulated using a 3D EM simulator. The design is fabricated on a single-layer Rogers RO4003C, and a good agreement between the results of the simulation and measurement is observed. The measured results show that the proposed structure has the insertion loss ofdB, and the isolation and output return loss better than 21.6 and 13.7 dB, respectively, when the return loss of the input port is better than 15 dB (4.8–4.95 GHz). This design has many advantages, such as low cost, low insertion loss, good return loss, good channels isolation, low profile, and compatibility with planar circuits. [ABSTRACT FROM AUTHOR]

This paper presents a compact 60-GHz power amplifier utilizing a four-way on-chip parallel power combiner and splitter. The proposed topology provides the capability of combining the output power of four individual power amplifier cores in a compact die area. Each power amplifier core consists of a three-stage common-source amplifier with transformer-coupled impedance matching networks. Fabricated in 65-nm CMOS process, the measured gain of the 0.19-mm power amplifier at 60 GHz is 18.8 and 15 dB utilizing 1.4 and 1.0 V supply. Three-decibel band width of 4 GHz and P of 16.9 dBm is measured while consuming 424 mW from a 1.4-V supply. A maximum saturated output power of 18.3 dBm is measured with the 15.9% peak power added efficiency at 60 GHz. The measured insertion loss is 1.9 dB at 60 GHz. The proposed power amplifier achieves the highest power density (power/area) compared to the reported 60-GHz CMOS power amplifiers in 65 nm or older CMOS technologies. [ABSTRACT FROM AUTHOR]

The design of wireless power transfer (WPT) and energy harvesting (EH) solutions poses different challenges towards achieving maximum RF-DC conversion efficiency in these systems. This paper covers several selected challenges when developing WPT and electromagnetic EH solutions, such as the design of multiband and broadband rectifiers, the minimization of the effect that load and input power variations may have on the system performance and finally the most optimum power combining mechanisms that can be used when dealing with multielement rectifiers. [ABSTRACT FROM AUTHOR]

In this paper, a novel W-band substrate integrated waveguide (SIW) power combiner/divider is analyzed theoretically and demonstrated experimentally/numerically, based on the antipodal fin-line SIW-rectangular waveguide (SIW-RW) transition and longitudinal slot coupling techniques. This antipodal fin-line SIW-RW transition can work at the frequency band of 86.4GHz-106.1GHz with return loss larger than 15 dB and inserting loss less than 2 dB. By combining the antipodal fin-line SIW-RW into the four-way longitudinal-slot SIW coupling structure, a novel back-to-back power dividing/combining system is achieved, which can operate at the frequency band of 92.8GHz-93.8GHz with return loss more than 10 dB and insertion loss less than 3.9 dB. Such a design can be used in future for spatial power amplifier applications. [ABSTRACT FROM AUTHOR]

By reductio ad absurdum, we show that a perfect power combiner of single-mode waveguides is impossible for incoherent input waves of the same frequency and same polarization as it is against the law of conservation of energy. The inevitable 3 dB loss of a three-port power combiner is explained physically. An incoherent power combiner of nearly 100% efficiency can be realized only if the two input fields have different wavelengths, have different polarizations, or are of orthogonal modes. [ABSTRACT FROM AUTHOR]

A power divider/combiner circuit, which simultaneously achieves wide bandwidth, flat gain characteristics, and bidirectional operation, is proposed for multichannel broadband system applications. The proposed circuit utilizes cascode-based bidirectional amplifier cores, which steer the operation modes between a divider and a combiner depending on the control input, and a two-stage distributed-amplifier topology with artificial transmission lines. Implemented in a 130-nm silicon–germanium BiCMOS technology platform, the proposed divider/combiner provides the advantage of seamless integration with digital control blocks. The power divider/combiner exhibits the flat in-band gain of 9 dB and the operational bandwidth of 2–22 GHz, which covers $S$ -, $C$ -, $X$ -, and $Ku$ -bands. In addition, it shows the amplitude imbalance of 0.8 dB, the phase imbalance of 3.5°, the port-to-port isolation of 22 dB, the output 1-dB compression point of 3 dBm, and good impedance matching under 100-mW dc power consumption. [ABSTRACT FROM PUBLISHER]

This paper presents a V -band 1.2-V wideband power amplifier (PA) with a compact four-way radial power combiner in a 90-nm CMOS process. A transformer-based radial power combiner with a 1-dB insertion loss at 60 GHz and a 0.043-mm ^{\mathrm { {2}}} compact size is designed for high-output-power combining and wideband load-pull matching. This PA achieves the saturated output power ( P_{\mathrm { {SAT}}}) of 20.6 dBm, the maximum power-added efficiency ( \textit PAE\mathrm { {max}}) of 20.3%, and a 20.1-dB small-signal gain ( S\mathrm { {21}}) at 60 GHz. The PA maintains a flat 20-dBm P\mathrm { {SAT}} with \textit PAE\mathrm { {max}} better than 17.3% within 50–64 GHz, and it has a 3-dB bandwidth (BW) of 24.5 GHz (41.8–66.3 GHz). The chip area without pads is 0.432 mm ^\mathrm 2 . To the best of the author’s knowledge, this $V$ -band PA with a flat frequency response of 20-dBm P\mathrm { {SAT}} presents the widest large-signal BW (50–64 GHz) compared with the reported 60-GHz CMOS high-output PAs. [ABSTRACT FROM AUTHOR]

This paper presents a general coaxial-conical-coaxial transmission line transition with a built-in impedance taper that can explicitly be chosen or optimized. The presented transition has a smooth profile, which is advantageous for peak power handling, and provides more degrees of freedom and greater flexibility to optimize devices compared with other transitions between conical and coaxial lines or coaxial lines of different sizes. The method is validated by designing and fabricating an eight-way coaxial line combiner, 0.55 $\lambda $ long and $0.26~\lambda $ in diameter, with a measured reflection coefficient of better than −22 dB over a 115% bandwidth (BW), and better than −12 dB over a 130% BW. [ABSTRACT FROM AUTHOR]

A new 2 × 1 power combiner scheme based on two-dimensional photonic crystal has been designed using hexangular waveguides. These waveguides are created by reducing the radius of inner rods in alternate manner which subsequently leads to coupled resonator optical waveguide structure. In this design, the outer hexagon has two input ports and the output port is embedded in the inner hexagonal. Due to geometrical and metallurgical engineering, the photonic bandgap locates in the THz region. Three different radii of coupled resonator optical waveguide rods have been studied. It has been shown that the structure with largest inner rods provides better power output. [ABSTRACT FROM AUTHOR]

In this article, a two-way power amplifier based on waveguide spatial power-combining technique in Ka-band is proposed. Based on the theoretical analysis and simulation results, the improved T-junction and probe transitions have been employed for the power-combining network. The final measurement results show that the saturated output power is over 29 dB with the power-combining efficiency above 78.9% at the operating frequency band from 30.2 GHz to 30.7 GHz. The proposed power amplifier can be applied in modern millimeter-wave circuits and communication systems. [ABSTRACT FROM PUBLISHER]

This paper presents the first active power combiner designed for ultrawideband applications covering a bandwidth of operation from 1 to 220 GHz. The circuit is implemented in a high-performance 0.13- \mu \textm SiGe BiCMOS technology ( f\mathrm { {max}} = 450 GHz) and based on an innovative dual-stage distributed architecture. The input stage realizes the power combination with a traveling-wave architecture. The output stage is a cascaded single-stage distributed amplifier, and it is employed to increase the overall gain. The circuit analysis necessary for circuit design is given, and its predictions are compared with the measurements in the time and frequency domains. The system requires 203 mW of dc power to provide a signal amplification of 20 dB from 1 to 170 GHz, which decreases to 15 dB at 220 GHz. Independent bias networks for the combining paths also enable a gain tuning range of 20 dB. The presented circuit improves by a factor 16 the state of the art for frequency of operation of distributed power combiners implemented in silicon and by a factor 20 the bandwidth. Compared with III–V implementations, the improvement factors are 4.5 and 5.5, respectively. [ABSTRACT FROM PUBLISHER]

Most dangerous explosive materials, both toxic and radioactive, contain nitrogen salts with resonant absorption lines in the frequency range 0.3-10 THz. Therefore, there has been growing interest in remotely detecting such materials by observing the spectrum of reflected signals when the suspicious material is interrogated by THz radiation. Practical portable THz sources available today generate only 20-40 mW output power. This power level is too low to interrogate suspicious material from a safe distance, especially if the material is concealed. Hence, there is a need for sources that can provide greater power in the THz spectrum. Generating and extracting high output power from THz sources is complicated and inefficient. The efficiency of vacuum electronic microwave sources is very low when scaled to the THz range and THz sources based on scaling down semiconductor laser sources have low efficiency as well, resulting in the well known "THz gap." The reason for such low efficiencies for both source types is material losses in the THz band. In this article an efficient power combiner is described that is based on scaling to higher frequencies a microwave combiner that increases the output power in the THz range of interest in simulation studies. The proposed power combiner not only combines the THz power output from several sources, but can also form a Gaussian wavebeam output. A minimum conversion efficiency of 89% with cophased inputs in a lossy copper power combiner and maximum efficiency of 100% in a Perfect Electric Conductor (PEC)-made power combiner were achieved in simulations. Also, it is shown that the TE01 output mode is a reasonable option for THz applications due to the fact that conductive loss decreases for this mode as frequency increases. [ABSTRACT FROM AUTHOR]

High output power multiplier is necessary for local oscillator (LO) source of millimeter-wave and terahertz applications. However, single multiplier chip power-handling capability is limited by understandably low efficiency level and other technical constraints. Conventional in-phase power-combined structures are sensitive to the fabrication and assembly errors. In order to circumvent these limits, we propose a power-combined multiplier architecture at 60 GHz based on fundamental frequency vector modulation at 30 GHz. The fundamental vector modulator adjustment can compensate the phase deviation at the two doubler output ports despite fabrication and assembly tolerances. We can increase the output power by approximately 3 dB compared with single multiplier without sacrificing the bandwidth. [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents a compact power combiner/divider for solid-state amplifier applications inspired by spatial combiner. The proposed 'one-stage' combining structure is realized by a single port tapered to an oversized microstrip connecting to parallel multiport microstrip sections. By adjusting the geometries of the structure, uniform amplitude/phase, and complex impedance matching at the multiport outputs can be achieved. A prototype 1-to-4 divider/combiner is designed and characterized at 5 GHz. Measured and simulated results showed similar trend and decent agreement. The measured combining efficiency of the circuit is 82.44% at 5 GHz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1121-1125, 2016 [ABSTRACT FROM AUTHOR]

A 1-to-25-way uniform amplitude and linear phase power divider, using slotted rectangular waveguides in the traveling-wave mode, is designed to cover the 71–77-GHz band. The design employs the scattering parameters of three-port couplers computed from the method of moments (MoM) solution to the integral equation of the slot aperture field. Subsequent genetic algorithm (GA) optimization is aimed at maximizing the return loss and combining efficiency and flatness of coupling amplitudes in the whole frequency band. GA utilizes the MoM solution to the coupled integral equations of slot apertures in the entire power divider structure. Simulations indicate the optimized power divider yielding better than 26-dB return loss and greater than 86% efficiency in the 71–77-GHz band for the power divider combiner connected back to back. Computed MoM results have been validated by the commercial code HFSS and also by experimentally measured results. The measured insertion loss of two back-to-back divider–combiners is about 2 dB. [ABSTRACT FROM PUBLISHER]

A planar compact contiguous-channel substrate integrated waveguide (SIW) multiplexer (MUX) is proposed in this paper. To reduce the size of the MUX, the output channels are closely aligned to each other through the use of a compact SIW power combiner. To develop the proposed MUX with high efficiency and high accuracy, a systematic design procedure using an aggressive space-mapping (ASM) optimization algorithm is presented. The fine model established in the full-wave simulator HFSS, the coarse model established in the circuit simulator ADS, and the ASM optimization algorithm are combined in the design procedure, and circuit elements are determined through suitable parameter-extraction procedures. As demonstrations, a Ku-band SIW four-channel MUX prototype is designed and verified by experiments. [ABSTRACT FROM PUBLISHER]

The far-infrared and submillimeter portions of the electromagnetic spectrum provide a unique view of the astrophysical processes present in the early universe. Micro-Spec ( μ -Spec), a high-efficiency direct-detection spectrometer concept working in the 450–1000-μm wavelength range, will enable a wide range of spaceflight missions that would otherwise be challenging due to the large size of current instruments and the required spectral resolution and sensitivity. This paper focuses on the μ -Spec two-dimensional multimode region, where the light of different wavelengths diffracts and converges onto a set of detectors. A two-step optimization process is used to generate geometrical configurations given specific requirements on spectrometer size, operating spectral range, and performance. The canonically employed focal-plane constraints for the power combiner were removed to probe the design space in its entirety. A new four-stigmatic-point optical design solution is identified and explored for use in far-infrared and submillimeter spectroscopy. [ABSTRACT FROM AUTHOR]

A novel 1-to-N broadband “i\pi-wave” power divider/combiner with reflection cancellation is presented and demonstrated. The new i\pi-wave structure provides reflection cancellation and output port isolation with 1-to-N (arbitrary N) signal splitting or N-to-1 summing. It has low loss due to its use of low-impedance transmission lines and provides a relative bandwidth of 50%–200%. The concept is studied theoretically and demonstrated experimentally with several 1-to-4 dividers. The divider/combiner pair provides power amplifiers with broadband operation and well-matched input/output impedances. The concept can be implemented in hybrid circuits or monolithic microwave integrated circuits (MMICs). [ABSTRACT FROM PUBLISHER]