This paper presents a wideband high-efficiency linear time-domain waveform-complementary distributed power amplifier (TDWC-DPA), with gain cells (GC) composed of deep Class-AB and inverse-Class-C structures. The proposed inverse-Class-C GC consists of N-type devices operating in the saturation region instead of in the cutoff region compared with conventional Class-C amplifiers. This allows the amplifier to conduct near the valleys of the input signal. This unique characteristic enables the inverse-Class-C GC to achieve an opposite conduction state compared to deep Class-AB amplifiers. Furthermore, distributed base-and collector-networks are deployed to combine deep Class-AB and inverse-Class-C GCs and form the standard sinusoidal signals with low harmonic content further through. The amplifier achieves enhanced in-phase superposition of fundamental waves with proper bias of the common base transistor. The fabricated TDWC-DPA achieves 41.8 dBc second harmonic suppression (HS) and 39.1 dBc third harmonic suppression respectively. With integrating 500 V output ESD protection, the single-ended TDWC-DPA achieves a$-$3-dB bandwidth from 2 to 14 GHz and a small signal gain of 20 dB. The maximum power-added efficiency (PAE) is 33.6%, the saturated output power is 19.4 dBm and the output 1 dB compression point (P$_{\mathrm{1dB}})$is 19.2 dBm. The proposed TDWC-DPA achieves significantly enhanced linearity with maintaining a competitive efficiency in a wide frequency range and can support communication systems deploying high-order modulation formats.

A continuously tunable optoelectronic oscillator (OEO) with three frequency tuning mechanisms is proposed to enable frequency locking covering the whole working band. Three frequency-tuning mechanisms are employed simultaneously in the OEO, including a course tuning of microwave photonic filter, a fine tuning of phase shifter and a frequency calibration of direct digital synthesizer (DDS). The introduction of frequency compensation signal achieved by DDS increases the locking range of OEO so that the lock-out problem caused by mode hopping can be effectively solved. In the proof-of-concept experiment, a 3–6 GHz tunable RF oscillating signal has been successfully verified. The locking range of the proposed OEO is extended over 11 times compared to conventional OEO. With a 500 m optical fiber inserted in the loop, the phase noise is measured to be −110 dBc/Hz at 10 kHz offset. The Allan deviation is improved from$1.7\times 10 ^{-8}$to$1.6\times 10 ^{-11}$at 1000 s averaging time. To the best of the authors’ knowledge, this is the first time that a frequency tunable OEO with full locking range has been implemented.

A${V}$-band heterodyne radiometer in SiGe BiCMOS employing a capacitor-reused absorptive inter-stage matching network is firstly proposed, which prevents from employing a circulator, a resistive attenuator or two quadrature couplers in the conventional high-sensitivity cascaded receiver. This radiometer consists of a five-stage low noise amplifier (LNA) with the proposed reflectionless output matching network (RLMN), and a double-balanced Gilbert mixer stage with integrated Marchand baluns. In the RLMN, the capacitor for in-band matching is reused as an impedance inverter in the lossy absorptive network to eliminate reflections. Utilizing the reflectionless LNA, the radiometer eliminates the out-of-band reflected signals round the interfaces of LNA and mixer. Fabricated in a$0.13~\mu \text{m}$SiGe BiCMOS technology, the reflectionless LNA achieves a gain of 31.9 dB@56 GHz, an absolutely stable operation in-band and 11 times larger stability factor out-of-band than conventional LNAs. Moreover, the implemented heterodyne radiometer achieves a noise equivalent temperature difference (NETD) of 0.3 K which is even comparable with wideband direct-detection radiometers.