This study presents a method to design a wideband signal source based on two voltage‐controlled oscillators (VCOs) with different centre frequencies and a mixer. The principle is to combine three frequency bands to form one wide frequency range. The three bands consist of second harmonic bands from two VCOs and a mixer band that is generated by mixing the two fundamental signals of VCOs to bridge the frequency gap. Apart from the wide tuning range, an additional benefit of a mixer‐based signal source is that the phase‐noise increases ∼3 dB/octave, which is less than the theoretical limit (6 dB/octave) for a fundamental frequency VCO followed by a frequency multiplier or extraction of second harmonic signal from a VCO. A prototype of the proposed signal source implemented in indium gallium phosphide hetero junction bipolar transistor monolithic microwave integrated circuit technology demonstrates both wide frequency tuning range and a very low phase noise. It exhibits a tuning bandwidth extending from 11.8 to 16.7 GHz and the signal's phase noise varies between −91 and −103 dBc/Hz at 100 kHz offset frequency.
This paper reports on a record-low-phase noise D-band signal source with 5 dBm output power, and 1.3 GHz tuning range. The source is based on the unconventional combination of a fundamental frequency 23 GHz oscillator in 150 nm AlGaN/GaN HEMT technology followed by a 130 nm SiGe BiCMOS MMIC including a sixtupler and an amplifier. The amplifier operates in compression mode as power-limiting amplifier, to equalize the source output power so that it is nearly independent of the oscillator's gate and drain bias voltages used for tuning the frequency of the source. The choice of using a GaN HEMT oscillator is motivated by the need for a low oscillator noise floor, which recently has been demonstrated as a bottle-neck for data rates in wideband millimeter-wave communication systems. The phase noise performance of this signal source is −128 dBc/Hz at 10 MHz-offset. To the best of the authors’ knowledge, this result is the lowest reported phase noise of D-band signal source.
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