A 100‐GHz‐band quadruple power combined monolithic HBT oscillator

In this paper we discuss a design methodology we used to fabricate a 100-GHz-band monolithic oscillator that power-combines four heterojunction bipolar transistor (HBT) based suboscillators, and the experimental results we obtained. We analyzed the oscillation condition by considering the loop gain when feedback is present, and adjusted the design parameters so as to combine the output powers of four suboscillators by making them oscillate in phase. The active elements we used for the suboscillators were InGaP/InGaAs HBTs with emitter dimensions 1.0 µm × 5.0 µm, for which fT and fmax were 190 and 240 GHz, respectively. The signal frequency of the completed oscillator was 97. 4 GHz, its output power +3.0 dBm. The biases on the HBTs were IC = 10 mA and VCE = 2.0 V. In order to discuss the power combining efficiency, we fabricated test oscillators with only one and dual power combined oscillators, which were investigated under the same measurement conditions. These circuits oscillated at 100.5 and 100.4 GHz, respectively, with −3.2 and −0.4 dBm output powers. These results confirm that the output power increases with the number of suboscillators. As far as we know, our article is the first to report a monolithic oscillator that power-combines four suboscillators. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(6): 13–22, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10003