76-GHz Planar Gunn VCO with Low Oscillation-Frequency Drift of 1.5 MHz/°C

A 76-GHz planar Gunn VCO with a temperature-compensation circuit was developed. The oscillation frequency of the developed Gunn VCO fluctuated over a temperature range of-30 to 85degC. The oscillation-frequency drift was calculated to be -6.7 MHz/degC. Accordingly, a temperature-compensation circuit, which uses the temperature dependence of the Gunn diode´s forward operation current, was fitted to the VCO. This circuit is composed of several resistors and operational amplifiers, and its output is connected to a varactor diode. The oscillation-frequency drift of the VCO is improved to an excellent value of -1.5 MHz/degC when the temperature-compensation circuit is applied. This Gunn VCO with a temperature-compensation demonstrates other good RF performances, namely, measured output power of 6.2 dBm at 76.5 GHz and the phase noise of -103.2 dBc/Hz at an offset frequency of 1 MHz. In the tuning-voltage range from 0 to 3 V, the VCO achieves tuning-frequency range of 238 MHz, output-power variation of 0.22 dB, and tuning-frequency linearity of 1.0 % at room temperature.