This paper presents a design methodology for a broadband high-efficiency power amplifier (PA). The large available impedance space of the extended continuous Class-GF mode is employed. A novel output matching network of the PA consisting of a rectangular double transmission line structure is proposed to meet impedance requirements. To validate the effectiveness of this structure, a high-efficiency PA operating in 0.8–3.0 GHz is designed using a CGH40010F GaN transistor. The measured results demonstrate that the drain efficiency falls within the range of 63.2%–71.9%, the output power varies from 40.2 to 42.2 dBm, and the gain ranges from 9.4 to 11.3 dB within the frequency band of 0.8–3 GHz. The realized PA exhibits an extremely competitive relative bandwidth of 115.8%.

A systematic design approach is presented for the design of broadband high-efficiency power amplifiers (PAs) by combining an improved ring-resonant filter matching network with a series of continuous modes. The improved ring-resonant matching network presented can effectively enhance out-of-band attenuation and sharp roll-off characteristics by adding a compensation structure with parallel stub. To verify the proposed design theory, a 10-W GaN HEMT device is designed and fabricated. The test results indicate that from the operating frequency band of 0.55−3.3 GHz with a relative bandwidth of 142.9%, a saturated output power of 38.5−42 dBm, drain efficiency of 58.2−70.3%, and a gain of 8.5–12 dB can be achieved under 3 dB gain compression, indicating the rationality of the design theory.

In this paper, a realization method for high-efficiency broadband power amplifier (PA) based on split-ring resonator (SRR) second harmonic output matching network (SHOMN) is presented. The SRR is composed of double rectangular rings, and it can flexibly match the second harmonic components to the high-efficiency impedance region in the Smith chart in a wide frequency band. Besides, the impedance transformation characteristic of SRR is derived, and the optimal output impedance is converted from the transistor drain to the output of SHOMN for accurate fundamental matching. For validation, a PA operating in 1.2–3.0 GHz is designed and fabricated for a 10-W GaN transistor. The measurement results show that the maximum efficiency can reach 78.3%; meanwhile, the average saturated output power is 41.0 dBm.

A compact three-dimensional (3D) circularly polarized (CP) microstrip antenna is presented in this paper. The antenna adopts three low-cost printed circuit boards to form an integrated and closed 3D structure, and the radiation patch and the feed patches are etched on the surface of that. A crossed slot is cut on the radiation patch to miniaturize the antenna, and triangular feed patches are introduced to increase the bandwidths. In addition, because of the utilization of a low-loss series feed line, the antenna has a high efficiency of more than 95%. A prototype of the antenna is measured to validate the method. The dimensions of the antenna is 0.064λ × 0.36λ (λ is the wavelength in free space at 1.2 GHz). The results indicate that the impedance bandwidth for voltage standing wave ratio ≤ 2 reaches 23%, and the bandwidth for axial ratio (AR) ≤ 3 dB reaches 10.1%. In the overlap band, the gains are > 4.5dBic. Additionally, the 3 dB beamwidth is more than 114°, and the beamwidth for AR ≤ 3 dB is more than 131° at 1.2 GHz.

A dual-band high-efficiency coaxial relativistic backward wave oscillator (CRBWO) with asymmetric resonant reflector is designed and presented in this paper. Improved sectioned coaxial slow wave structure (SWS) with stepwise variation of coupling impedance and phase velocity is employed, and the performance of the dual-band CRBWO is investigated by use of a 2.5-D particle-in-cell (PIC) simulation code. When the diode voltage is 510 kV and beam current is 9.03 kA, an average microwave power of 1.0 GW with power conversion efficiency of 21.7% is obtained. Synchronously radiating dual-band frequencies of 8.1 GHz and 9.9 GHz are obtained, corresponding to C-band and X-band, respectively. A more clear and stable beating radiation microwave power with beating frequency of 1.8 GHz is acquired.