Investigation of HBT oscillator noise through 1/f noise and noise upconversion studies

It was shown that the L/(f) characteristics of a heterojunction bipolar transistor (HBT) dielectric resonator oscillator can be approximated by using the HBT´s low-frequency noise spectra and the oscillator upconversion factor´ K´/sub FM/. Experimental studies have been used for this purpose and the measured L(f) ranged from -89 dBc/Hz to -101 dBc/Hz at a 10-kHz offset frequency. It was shown that the upconversion of the low-frequency noise is the primary cause of L(f) in the oscillator and its frequency dependence is directly affected by the low-frequency noise spectrum rather than by K´/sub FM/ itself. dL(f)/df deviates from the -30-dB/decade rate, expected for upconversion of ideal 1/f noise, due to traps in the device.<>