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A 232–250-GHz traveling-wave frequency doubler is presented using a 250-nm InP double heterodyne bipolar transistor (DHBT) technology. Compared to the previous traveling-wave structures, the proposed frequency doubler employs physical open at the end of the input feed line, thus minimizing the input signal leakage and avoiding the crossover of the output signal line. In addition, the output power is maximized by load–pull matching at the 2nd harmonic while the fundamental suppression is enhanced by phase compensation of the differential signal. The frequency doubler exhibits peak output power of 5.2 dBm at 240 GHz with a conversion gain of −4.3 dB and overall efficiency of 2.9%. The 3-dB bandwidth for output power is from 232 to 250 GHz. The fundamental suppression is 25 to 33 dB over the bandwidth. The chip size is as small as $443 \times536\,\,\mu \text{m}^{2}$ owing to the traveling-wave structure requiring no balun. [ABSTRACT FROM AUTHOR]

This paper presents a 300-GHz voltage-controlled oscillator (VCO) with a wide frequency tuning range and high output power. To generate fundamental oscillation at 300 GHz, a cascode cross-coupled pair is employed as a VCO core instead of a conventional common-emitter pair. Capacitive emitter degeneration is added to the VCO core to achieve a wide bandwidth of a negative conductance. In addition, the phase of the oscillation feedback loop is analyzed and optimized to further extend the tuning range. The VCO is fabricated in a 0.25- $\mu \text{m}$ InP DHBT technology ($f_{\mathrm {T}}/f_{\mathrm {max}} = 392$ /859 GHz). Measurements show that the VCO frequency is tuned from 272.4 to 310.8 GHz with a peak output power of 1.5 dBm. To the best of authors’ knowledge, this is the widest tuning range of 38.4 GHz (a fractional bandwidth of 13.2%) among the reported fundamental VCOs at the WR-3 band. [ABSTRACT FROM AUTHOR]