This letter presents a broad dual-band rectifier with a wide input power range that employs a dual-band matched voltage doubler (DMVD). The DMVD is composed of a voltage doubler and $L$ -type matching networks connected with each diode; it transforms the input reactance of each diode independently over wide input power and broad dual-band ranges, thereby widening the dynamic input power range. The proposed rectifier was implemented with the dimensions of 40 mm $\times15$ mm. Measurements reveal that the power conversion efficiency (PCE) was maintained at over 50% in the wide input power ranges of 10.3–32 dBm and 13.5–31.5 dBm at 0.915 and 2.45 GHz, respectively. PCEs exceeding 50% were measured over frequency ranges of 0.3–1.1 GHz and 1.5–2.6 GHz.

This study presents a compact rectifier array with an adaptive power distribution network (APDN). The rectifier array comprises rectifier cell 1 for both high-power mode and high-frequency band; rectifier cell 2 for both low-power mode and low-frequency band; and a power distribution network, which adaptively distributes power according to the input power and frequency. The proposed APDN is merged with input matching networks of the subrectifiers to achieve low insertion loss and high compactness with wideband characteristics. For validation, the proposed rectifier array was designed, implemented, and measured. The measurement results show that the power conversion efficiency (PCE) is over 50% within an input power range of 9.9-30.8 dBm. A peak PCE of over 50% is realized at a frequency range of 0.1-2.7 GHz.

This study presents a highly efficient power amplifier (PA) based on a compact harmonic-controlled matching network (HCMN). The proposed HCMN with three-stage band-stop matching network (BMN) can simultaneously match to the optimum power matching impedance at fundamental and second harmonic frequencies and suppress second harmonic signals caused by nonlinearity without an additional filter. For verification, the proposed PA was designed, fabricated, and measured. The implemented PA was a compact size of 53.3 mm $\times$ 40 mm. The measurement results show that the output power is 36–38.6 dBm, and the drain efficiency (DE) is 68.2%–74.3% in the frequency range of 2.9–3.3 GHz. The proposed PA also achieves the low second harmonic level of $-$ 44.1 to $-$ 67.1 dBc in the frequency range of 2.9–3.3 GHz.

A W-band differential frequency doubler using a current-reuse configuration in a 65 nm CMOS process is presented in this letter. The differential current-reuse circuit with a second harmonic coupling transformer is introduced to improve conversion gain at small input powers minimizing the effect of the RF bypass capacitor. The proposed circuit achieves a conversion gain of 0.8 ~ -4.2 dB and a fundamental rejection above 19 dB in the input frequency range of 36.5~44 GHz with -4 dBm input power. It has conversion gain variation below 1 dB when the input power varies from -7.4 to 0.1 dBm at 77 GHz. The dc power consumption is 14 mW. It has the highest conversion gain with the smallest chip size of 0.22 mm ² among all V-/W-band CMOS frequency doublers.

A miniaturized continuous-wave Doppler radar sensor operating at 915 MHz to remotely detect both respiration and heart rate (beats per minute) is presented. The proposed radar sensor comprises a front-end module including an implemented complementary metal-oxide semiconductor low-noise amplifier (LNA) and fractal-slot patch antennas, whose area was reduced by 15.2%. The two-stage inverter-based LNA was designed with an interstage capacitor and a feedback resistor to acquire ultrawide bandwidth. Two operating frequencies, 915 MHz and 2.45 GHz, were analyzed with regard to path loss for efficient operation because frequency affects detection sensitivity, reflected signal power from the human body, and measurement distance in a far-field condition. Path-loss calculation based on the simplified layer model indicates that the reflected power of the 915 MHz radar could be higher than that of the 2.45 GHz radar. The implemented radar front-end module excluding the LNA occupies 35 × 55 mm². Vital signs were obtained via a fast Fourier transform and digital filtering using raw signals. In an experiment with six subjects, the respiration and heart rate obtained at 0.8 m using the proposed radar sensor exhibited mean accuracies of 99.4% and 97.6% with respect to commercialized reference sensors, respectively.

In this study, a highly efficient harmonic suppressed dual-band power amplifier (PA) for harmonic radar systems is proposed. The proposed PA incorporates a harmonic-controlled dual-band matching network (HCDMN) comprising $\lambda $ /4 open stubs at the second-harmonic frequencies and series transmission lines. The HCDMN can effectively suppress unwanted second-harmonic signals and control the fundamental and second harmonic impedances to operate in continuous class-F1 mode at two operating frequencies. The implemented PA has dimensions of 75.3 mm $\times 54.9$ mm. Measurement results demonstrate that the PA achieves an exceptional performance, with peak drain efficiencies (DEs) of 81.5 and 71.8 %, saturated output powers of 40.3 and 41.9 dBm, and second harmonic levels of −75.6 and −49.4 dBc at 2.3 and 3.35 GHz, respectively. Furthermore, the DEs remain above 65 % in the two frequency bands of 2.2–2.5 and 3.3–3.45 GHz.