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This paper demonstrates the analysis of a long-distance high-power microwave wireless power transmission (MWPT) system based on asymmetrical resonant magnetron and cyclotron-wave rectifier. In the system, the novel magnetron with the asymmetrical resonant cavity, the straps, and the output loop coupling circuit can effectively promote the beam–wave interaction, suppress the mode competition, and enhance the output coupling, which results in a 400 kW output microwave power with a conversion efficiency of 45%. The transceiver Cassegrain antenna system with its simple structure, high conversion efficiency, and high power capacity can attain an integral power transmission efficiency of 2.6% at 10 km distance. The cyclotron-wave rectifier with high efficiency and single-tube high power capacity can achieve 85% microwave to DC conversion efficiency. Finally, the long-distance high-power MWPT system can achieve 8.5 kW DC power with about 1% DC–DC transmission efficiency at the operating 2.45 GHz frequency and for the 10 km distance. Such a system is likely a potential and attracting solution to remotely power the fuel-free aerial vehicle from the ground, can also provide electrical power to an isolated mountain top or an island, and even an alternative to transmit the power from space solar power satellite in geostationary orbit to the ground.

A design scheme is presented for an all‐pass coupled‐line (APCL)‐based dual‐band impedance‐matching network. Salient features include a highly flexible frequency ratio (r) (high of 15 and low of 1.2) and impedance transformation ratio (k) (high of 9 and low of 0.2) simultaneously at two arbitrary, uncorrelated frequencies of interest. The design strategy consists of two APCL sections and a stub that prove to be simple and easy to prototype. Detailed mathematical modelling and graphical interpretations have been presented. Closed‐form design equations have been developed and backed up with design examples. Two dual‐band T‐junction power dividers (TPDs) have been designed to demonstrate the application of the proposed impedance transformer at two widely separated frequencies. RO4350 B‐ and RO5880‐based prototypes have been fabricated for both the matching network and the TPD to validate the proposed theory. The measurement results demonstrate an achievable frequency ratio of 15 and an impedance transformation ratio of 9 in simultaneous operation mode.

In this article, we propose a new robust and highly efficient digital predistortion (DPD) concept for the linearization of wideband RF power amplifiers (PAs). The proposed approach is based on the combination of a parallelized delta-sigma modulator (DSM) and a forward model of the PA. This concept applies multi-rate techniques on a DSM that incorporates the forward PA model in its feedback loop to perform the required signal predistortion. Such a technique eliminates the need of reverse modeling and its associated problems. The multi-rate approach relaxes enormously the clock speed requirement of the DPD, which allows handling high signal bandwidths at feasible sampling rates. Moreover, enhanced performance can be achieved without the need of increasing the order of the modulator which reduces the sensitivity of the system to gain variations and phase distortions caused by the nonlinear PA characteristics. Three time-interleaved parallel DPD (P-DPD) variants are described and introduced, all of them have been shown to offer increased accuracy, and consequently better linearization performance compared to the DSM-based DPD state-of-the-art. The proposed architectures are tested and assessed using extensive real-world RF measurements at the 3.6 GHz band utilizing wideband 100 MHz 5G New Radio (NR) transmit waveforms, evidencing excellent transmit signal quality. publishedVersion

Conventional digital predistortion (DPD) techniques are facing the challenge of complexity in the fifth generation (5G) and beyond concurrent dual-band terminal transmitters. This article proposes novel low-complexity behavior models for the DPD of terminal power amplifiers (PAs). Derived from the conventional memory polynomial (MP) model, the new models utilize magnitude-selective affine (MSA) functions as nonlinear basis functions to greatly decrease the model complexity. The proposed paralleled envelope indexed 2-D MSA (PI-2-D-MSA) model and combined envelope indexed 2-D MSA (CI-2-D-MSA) model take both the in-band intermodulation and cross-band modulation into account and can well compensate for nonlinear distortion in dual-band terminal PAs. Moreover, the proposed models are extended to nonuniform sampling rate (NSR) scenarios, where the aliasing effect for the low sampling rate band is analyzed. Simulations and experimental measurements under the uniform sampling rate and the NSR scenarios were carried out on a 1.7–2.8-GHz wideband Doherty PA and a 4.4–5.0-GHz class-AB terminal PA and demonstrated the linearization performances of the proposed models. The total numbers of floating-point operations (FLOPs) of the PI-2-D-MSA and the CI-2-D-MSA models were 11% and 8% of that of the prior 2-D-MP model, respectively. Even though their linearization accuracy deteriorated, the relaxed linearization standard for terminal transmitters can still be achieved.

Neural network (NN)-based models are perceived as being accurate models for power amplifier (PA) behavioral modeling and digital predistortion (DPD) applications. However, the complexity of NN’s models in terms of the number of coefficients increases with the memory depth, nonlinearity order, signal bandwidth, and the number of carriers. In this article, a novel augmented convolutional neural network (ACNN)-based DPD is proposed to linearize the concurrent multiband PAs. In the ACNN model, the convolution layer with a fully connected layer serves to model the intermodulation distortion (IMD), cross-modulation distortion (CMD), and nonlinearities of the concurrent multiband PA. The pooling layer in the ACNN reduces the model’s complexity. The measurement results show that the proposed DPD requires significantly fewer coefficients and floating-point operations (FLOPs) than the state-of-the-art DPDs. This model’s complexity reduction arises with the number of carriers in the multiband aggregated signal. The measurement results also show that the proposed DPD has a better linearization performance in terms of metrics, such as normalized mean square error (NMSE), adjacent channel power ratio (ACPR), and error vector magnitude (EVM).

The behavior model based on the artificial neural network has been widely used in the broadband power amplifier (PA). Although the deep neural network (DNN) performs well in the PA modeling with high-dimensional inputs, the training time of the DNN model is still long. This letter proposes a PA modeling method based on transfer learning to reduce training time without sacrificing modeling performance. In the proposed method, the model can be divided into two parts. The first part is defined as a predesigned filter that can extract the features of PA, and the second part is defined as adaptation layers that can be used to fit the real PA output. Experimental results show that the proposed method can effectively reduce the training time and ensure good modeling performance compared with the traditional DNN model.

In this paper, a novel multi-stream spatial digital predistortion (DPD) technique is proposed to model and linearize the fully-connected (FC) hybrid beamforming (HBF) transmitters. The proposed scheme solves the DPD implementation issue in the FC HBF array by estimating and linearizing the beam signals instead of the individual PAs. In FC HBF systems, significant intermodulation (IMD) between different transmit signals will be generated due to the analog beamforming and combining network upstream of the power amplifiers (PAs). The IMD beams will end up being radiated in different directions and some of them might fall in the linear beam directions. Therefore, multi-input DPD blocks using a practical multi-variable model are constructed for each RF chain to eliminate the complicated inner- and cross-channel IMDs of the beam signals. Simulations on a 4-stream 64-element FC HBF array and experimental tests on a 2-stream 4-element system are carried out to benchmark the proposed DPD technique against the conventional techniques. Better than 13 dB adjacent channel power ratio (ACPR) improvement and 12 dB normalized mean square error (NMSE) improvement have been achieved by the proposed DPD technique.

In this article, a novel broadband millimeter-wave (mm-wave) front end (FE) based on the asymmetric switch network structure is proposed for multistandard fifth-generation (5G) applications. The asymmetric switch network consists of a bidirectional impedance transformation network and a T-type topology single-pole single-throw (SPST) switch. In the TX-mode, the bidirectional impedance transformation network serves as an output matching network to achieve a continuous-mode Class-F−1 power amplifier (PA) to expand the bandwidth. In the RX-mode, the OFF impedance of the PA can be transformed into a high-impedance region by the bidirectional impedance transformation network. Based on the proposed structure, a broadband mm-wave front end is implemented in the 0.13- $\mu \text{m}$ SiGe BiCMOS process, which occupies $906\,\,\mu \text{m}\,\,\times 997\,\,\mu \text{m}$ including pads. In the TX-mode, the −1-dB $P_{\mathrm {sat}}$ bandwidth of the FE covers 21–44 GHz with the maximum output power of 18.1–19 dBm and the peak power added efficiency (PAE) of 20.2%–26.8%. In the RX-mode, the FE achieves an 84.6% and −3-dB small-signal gain fractional bandwidth from 20.2 to 49.8 GHz with 38-mW power consumption. It achieves a measured noise figure (NF) of 7.62–11.64 dB over the frequency range of 24–48 GHz. To the best of our knowledge, this is the first FE that covers all the present 5G mm-wave bands without reconfiguration.

In this brief, a 24–29.5 GHz millimeter-wave (mm-wave) voltage-combined Doherty power amplifier (DPA) based on compact low-loss combiner is proposed for the fifth-generation (5G) applications. By maximizing the use of parasitic parameters in the circuit, a compact low-loss combiner is proposed to achieve the required impedance transformation with only one additional series capacitor. A detailed design procedure is also introduced in the brief. Based on the proposed combiner, a fully integrated Doherty PA is implemented in 0.13- ${\mu }\text{m}$ SiGe BiCMOS process with a core area of only 0.29 mm2. The DPA achieves a 27% −3-dB small-signal gain fractional bandwidth and a 15.9 dB small signal gain at the center frequency of 27 GHz. The −1-dB Psat bandwidth covers 24–29.5 GHz (20% fractional bandwidth), and the maximum output power is 20.8 dBm ± 0.4 dB. From 24 to 29.5 GHz, the designed DPA provides 23.2% to 28.4% power-added efficiency (PAE) at saturated output power, and 18.3% to 21.9% PAE at 6 dB of output power back-off (OPBO).

In this paper, we proposed a novel radio over fiber (RoF) transmitter architecture to achieve high dynamic range (DR) suitable for millimeter wave (mm-wave) applications, supported by simulation and experimental validations. The designed test benches achieved more than-41 dBc adjacent carrier leakage ratio (ACLR) for a fifth generation/new radio (5G/NR) signal of 100 MHz bandwidth, transmitted in the upper frequency range (FR2) at 28 GHz. The key for this achievement is the utilization of the electrical mixing with proper phase shift before optical modulation. The mixing of the local oscillator (LO) and the intermediate frequency (IF) signals in the electrical domain, reduces the unwanted beating between optical bands prior to the photo-detection stage, hence preventing photodetector saturation, which leads to higher optical-to-electrical conversion.