Wideband Colpitts voltage controlled oscillator with nanosecond start-up time for bubble-type motion detector

This paper presents a wideband Colpitts voltage controlled oscillator (VCO) with a center frequency of 8.35GHz and nanosecond start-up time for a new bubble-type motion detector that has a bubble layer of detection zone at the specific distance from itself. Combined with the varactor diode, the shunt microstrip line resonating at 6.8GHz is proposed to compensate the input reactance of the transistor that changes from capacitive values to inductive values at 8.1GHz. The measured VCO shows the tunable bandwidth of 2.3GHz, the output power of 4~7dBm and the start-up time of less than 2nsec. It will be utilized for the novel bubble-type motion detector later.