In this letter, the second source harmonic in continuous-mode class GF (CCGF) is optimized to flatten the power amplifier’s (PA) frequency response over a wideband. A new design space is explored by considering the effects of controlling the input nonlinearity of the gate–source capacitance ( $C_{\mathrm {gs}}$ ) on the drain current waveforms under continuous-mode drain voltage waveforms. A wideband CCGF PA is designed and fabricated using a commercial 10-W gallium nitride (GaN) device and low-temperature co-fired ceramic (LTCC) technology. Results of the measurement show a flat frequency response from 3.3 to 4.3 GHz with variations less than ±0.4 dB for 40 dBm output power, and 17 dB large signal gain at 3-dB compression point. A drain efficiency of 66 ± 2% is achieved over the entire bandwidth.
In this letter, two basis function multiplexing-based behavioral modeling methods for digital predistortion (DPD) of RF power amplifiers (PAs) are proposed to reduce the running complexity of DPD. The proposed full basis-propagating selection (FBPS) model and reduced-complexity FBPS (RC-FBPS) model give two reasonable ways to multiplex even-order basis functions, extending the basis-propagating selection (BAPS) model which only uses basis function delay and odd-order basis functions. The experimental results confirm that both the proposed FBPS and RC-FBPS models can achieve a good tradeoff between running complexity and performance.
This letter presents a low-resolution multiband transmitter architecture using direct digital synthesis (DDS) with dithering. Modern modulated signals constructed by a low-resolution digital-to-analog converter (DAC) suffer from quantization errors and distortions. The proposed technique reduces the quantization problems with the use of a proper oversampling ratio (OSR) and the dithering technique. This technique has lower cost and lower complexity compared to conventional transmitters while maintaining linearity performance. A 50-MHz 5G NR 256-quadratic-amplitude modulation (QAM) signal is used for concept validation at bands n1, n40, and n50. The proposed work achieved the adjacent channel leakage ratio (ACLR) and error vector magnitude (EVM) requirements of under −30 dBc and 3.5%, respectively. A single 3-bit 10-GS/s radio frequency (RF) DAC is used where the performance is similar to a conventional transmitter using a pair of 5-bit baseband in-phase and quadrature (IQ) DACs.
A wideband common-gate (CG) cascode low-noise amplifier (LNA) is demonstrated with a 28-nm fully depleted silicon on insulator (FDSOI) CMOS process. Wide bandwidth is achieved with a CG structure in the first stage and tightly coupled ( $k=0.86$ ) transmission line transformer (TLT) matching networks. A gm-boosting technique with cross-coupled capacitors improves the gain and noise figure (NF) of the CG amplifier. A high-input 1-dB gain compression point (IP1 dB) can be achieved by introducing an inter-stage inductor at the second-stage cascode amplifier. The LNA shows 19.3 dB gain, 3.1 dB NF, 19.8 GHz (63%) of 3 dB bandwidth, and −15.7 dBm IP1 dB at 28 GHz.
This letter proposes a modeling approach to handle nonuniform transient electromagnetic field coupling to transmission lines (TLs). In this approach, the matrix pencil method is applied to express the complex-valued external electric field at the horizontal direction along the TL by the first order of the exponential function in the frequency domain. The fitting procedure of the MPM only contains several matrix computation steps and does not need the initial value or any searching process, which leads to a significantly higher fitting efficiency. Moreover, the fitted results are formed with the first order of the exponential function, which ensures that the analytical solution of the TL equation can be formulated and thus has a high calculation efficiency. The proposed method was validated experimentally using a large scale of radiated wave simulator.
A novel behavioral modeling approach called adaptive model tree (AMT) is proposed for digital predistortion (DPD) of RF power amplifiers (PAs) in fixed and time-varying configurations. The AMT model is piecewise based on the decision tree and the reduced-complexity full basis-propagating selection (RC-FBPS) model. A novel two-step joint iterative algorithm is proposed to achieve a good match between the decision tree and the submodels obtained from the RC-FBPS model. The AMT model inherits and enhances the respective advantages of the decision tree and RC-FBPS model to have a powerful adaptive capability potentially. The experimental tests on a Doherty PA confirm that the AMT model can achieve a better trade-off between linearization performance and complexity than the state-of-the-art model in the fixed configuration. Furthermore, to characterize and compensate for the complex dynamic nonlinear distortions of PAs in time-varying configurations, the piecewise modeling technique in time-varying configurations is proposed and applied to the AMT model in this article. The experimental results confirm that the AMT model achieves excellent linearization performance with very low complexity in time-varying configurations and good generalization performance for new configuration combinations that are not used for training.
In this letter, a novel wideband microstrip to additively fabricated waveguide transition is presented.The proposed design takes advantage of the flexibility of 3-D printing to realize a highly integrated transition from the microstrip line on a printed circuit board (PCB) to an air-filled waveguide using an additively manufactured radiating probe.The idea is experimentally verified by the realization of an exemplary transition working within the X-band at f 0 = 10.5 GHz.The measured performance of the back-to-back transition proves its usefulness and possibility of utilization in highly integrated PCB-waveguide circuits.A PolyJet printing technology with copper electroplating was used in combination with PCB on microwave grade laminate.A bandwidth of f H / f L = 1.8 was obtained with the impedance match better than 9.5 dB and in-band insertion loss per transition below 1.1 dB.
This letter presents a new passive sensor for temperature measurements based on a harmonic radio-frequency identification (RFID) tag that uses the temperature sensitivity of Schottky diodes as the main component for the generation of harmonics. The design of the harmonic sensor is based on the fact that the diode is a nonlinear device that when excited at one fundamental frequency generates harmonics of that signal. In this case, the generation mechanism is sensitive to temperature due to the diode thermal voltage variation with temperature. Measurements prove the performance of the sensor.
With radar networks, the resolution of critical radar parameters such as Doppler and angle can be improved compared to a single radar sensor. As the network's aperture is considerably larger than that of a single radar, a much higher angular resolution is achieved. However, with a large aperture, range-dependent phase deviations, that is, near-field effects, occur and affect the angle estimation. In this work, these near-field effects are evaluated exemplarily for a coherent network. Furthermore, a new strategy to compensate for those network near-field effects is proposed and demonstrated based on measurements. The benefits of the near-field compensation are emphasized by comparing the network's angle-estimation capabilities with and without compensated near-field effects.
In this letter, a $K$ -band signal generation phase shifter (SGPS) is implemented using a standard 55-nm complementary metal-oxide semiconductor (CMOS). Its phase shifting is achieved by injecting signal of a voltage-controlled oscillator (VCO) to the other through an injection buffer. Besides continuous phase shift, it can offer a signal source, facilitating multi-phase signal generation in phase array transceivers. Measurement results suggest the prototype implemented in 55-nm CMOS is able to provide a frequency tuning range of 22.5 to 24.8 GHz and minimal output power of 5.2 dBm. It demonstrates a maximal tuning phase of 45.5°.
In this letter, a fully packaged dual-mode bandpass filter (BPF) with wide upper stopband is presented. The stripline patch resonator loaded by the shorting slabs is adopted to achieve the dual-mode bandpass performance under operation of TM00 mode and TM01 mode. To remove other harmonic resonances of the stripline patch resonator, a common-mode double-point inset-feeding technique is proposed at the very beginning to prevent the excitation of high-order modes. To verify the design concept, a prototype packaged dual-mode BPF working at 4.0 GHz with the fractional bandwidth (FBW) of 8.2% is designed and fabricated using the multilayer liquid crystal polymer (LCP) circuit technology. Final results theoretically demonstrate and experimentally confirm that a wide stopband rejection up to $4.3f_{0}$ is obtained, well verifying the feeding method.
The IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS (MWCL) is published monthly with the purpose of providing fast publication of original and significant contributions relevant to all aspects of microwave/millimeter-wave technology, with emphasis on devices, components, circuits, guided wave structures, systems and applications covering the frequency spectrum from a few 100 MHz to submillimeter-waves and infrared.
Artificial neural network (ANN) model development for microwave components principally includes two parts of work, i.e., data sampling and model structure adaptation. In existing various ANN modeling methods, the model structure adaptation process mainly focuses on adjusting the number of neurons within each hidden layer of ANN while keeping the number of layers unchanged. To make the ANN modeling process more flexible and efficient, an automated multilayer neural network structure adaptation method with $ {l_{1}}$ regularization is proposed in this letter. We propose a new ANN model structure combining multilayer perceptron (MLP) and additional connections between the output layer and each hidden layer/input layer. A new training scheme with $ {l_{1}}$ regularization is proposed to automatically determine the final model structure with user-desired model accuracy. Using the proposed model structure adaptation method, both the number of layers and the number of neurons within each layer of the final ANN model can be adaptively determined to address different needs for different microwave modeling problems. The proposed method is demonstrated by two microwave filter modeling examples in which the model development process achieves a time saving of at least 40% over existing methods.
In this letter, a new Bayesian optimization (BO) method with dynamic feasible region shrinkage (DFRS) technique for power amplifier (PA) design is proposed. As a powerful optimization tool, it provides a more effective way to optimize the performance of PA than the embedded commercial optimization tools. It also has a better convergence speed than the existing fixed mode acquisition function. Results show that the new technique provides a great optimization for PA design, not only for circuit optimization but also for electromagnetic (EM) optimization.
This letter presents a low noise amplifier (LNA) with a 3-dB gain bandwidth (3-dB BW) of 18–44 GHz in 65-nm CMOS technology. By deriving an analytical equation of input impedance, a co-design methodology for the first two stages of LNA that can simultaneously achieve broadband input matching and low noise figure (NF) is implemented. Weakly coupled asymmetric transformers that introduce a section of reverse parallel winding in the primary coil are designed to realize broadband interstage matching, optimize the gain flatness and boost the transconductance. The proposed LNA achieves a measured peak gain of 19.5 dB with a fractional 3-dB gain bandwidth (FBW) of 83.8%, covering the whole $K$ -band and $Ka$ -band. The measured NF is 2.6–3.5 dB from 20 to 43 GHz. To the best of our knowledge, the proposed LNA achieves the highest 3-dB BW and FBW with competitive NF. The measured input 1-dB gain compression point ( $\text {IP}_{\mathrm {1\,dB}}$ ) ranges from −23 to −18.5 dBm over the entire 3-dB gain bandwidth.
In this letter, a novel filter with high selectivity is proposed using a hybrid multilayer half-mode substrate-integrated waveguide (HMSIW). First, a rectangular HMSIW is used to realize a third-order cross-coupling topology, which could introduce a transmission zero (TZ) on the left side of the passband. Then a ring microstrip resonator is added to form the new dangling block, which realizes the fourth-order response with an additional TZ located on the right side of the passband. Sharp skirt and high selectivity are then achieved. In addition, since each mode of the HMSIW has different external coupling strengths at the same feeding position, harmonic suppression can be achieved easily by moving the feeding position. Therefore, a good stopband can be obtained with decent out-of-band performance. Size reduction is also achieved through the multilayer HMSIW and hybrid microstrip structures as well.
In this letter, low-phase-nose multicore class-F voltage-controlled oscillators (VCOs) using coupled-lined-based synchronization topology are proposed. Compared to traditional resistance-coupled multicore VCOs, the proposed coupled-line-based topology improves the $Q$ of the small inductors in the millimeter-wave frequency range. Mode ambiguity is eliminated for a robust oscillation startup. Quad-core and oct-core VCO prototypes are designed and implemented in 65-nm CMOS process, which exhibit a measured frequency tuning range of 20.5% centered at 31.32 GHz. The quad-core VCO has a measured phase noise (PN) of −134.33 dBc/Hz and a corresponding FoM of 191.32 dBc/Hz at 10-MHz offset from 28.28 GHz. The oct-core VCO has a measured PN of −137.23 dBc/Hz and a corresponding FoM of 191.08 dBc/Hz at 10-MHz offset from 28.16 GHz.
This paper presents a modified post-distortion (PD) linearization technique for cascode common-gate low noise amplifiers (CG-LNAs) working at high frequencies up to millimeter-wave band. This technique utilizes an auxiliary transistor together with an inter-stage inductor to suppress the third order distortion without degrading gain. The input third order intercept point (IIP3) of the linearized CG-LNA is improved by a factor of up to 12 dB. For demonstration, an mm-wave differential CG-LNA was fabricated based on a 65-nm CMOS process. It achieves 2.4–10.6 dBm IIP3, 9.6–12 dB gain, 5.0–5.45 dB NF over 26–31 GHz and consumes 14.4 mW from a 1.2 V supply.
This letter presents an $X$ / Ku dual-band switchless power amplifier (PA) with frequency reconfigurable operation in a 0.25- $\mu \text{m}$ GaAs pHEMT process. The proposed reconfigurable PA consists of one dual-band drive amplifier and two single-band amplifiers in parallel. The first stage drive amplifier works in dual-band mode of $X$ -band and Ku-band, and the two single-band amplifiers work in $X$ -band and Ku-band, respectively. An interstage coupled line is used to split the dual-band frequencies into high-band (Ku-band) and low-band ( $X$ -band), and the output-stage coupled line acts as a combiner. The operating frequency band of the proposed PA can be changed by turning off drain voltages of unused single-band amplifiers. Measurements results show that the proposed reconfigurable PA features a maximum power-added efficiency (PAE) of 44.4% and a power gain of 19.6 dB while delivering an output power of 29.6 dBm at 8.5–9.5 GHz of the low-band mode. At 15.5–16.5 GHz of the high-band mode, the PA achieves a maximum PAE of 38.4%, a power gain of 18.1 dB with an output power of 30.1 dBm. The chip area of the proposed reconfigurable PA is 2 $\times $ 2 mm2 including all RF and dc pads.
Complex permittivity measurements of irradiated high-resistivity float-zone silicon have been performed in this letter from microwave to millimeter-wave frequencies employing three different resonance techniques. It has been proven that the irradiated silicon exhibits resistivity of the intrinsic silicon at temperatures larger than 295 K and the loss tangent due to phonon absorption reaches about 10 −5 at room temperature. The total loss tangent of the room-temperature irradiated silicon is smaller than $6\times10$ −5 at frequencies larger than 5 GHz. The real part of the complex permittivity of silicon linearly increases with temperature for $T $ > 200 K.
