title: Reduced transposed flicker noise in microwave oscillators using gaas-based feedforward amplifiers.
abstract: Transposed flicker noise reduction and removal is demonstrated in 7.6 GHz microwave oscillators for offsets greater than 10 kHz. This is achieved by using a GaAs-based feedforward power amplifier as the oscillation-sustaining stage and incorporating a limiter and resonator elsewhere in the loop. 20 dB noise suppression is demonstrated at 12.5 kHz offset when the error correcting amplifier is switched on. Three oscillator pairs have been built. A transmission line feedback oscillator with a Qo of 180 and two sapphire-based, dielectric resonator oscillators (DROs) with a Qo of 44,500. The difference between the two DROs is a change in the limiter threshold power level of 10 dB. The phase noise rolls-off at (1/f)(2) for offsets greater than 10 kHz for the transmission line oscillator and is set by the thermal noise to within 0-1 dB of the theoretical minimum. The noise performance of the DROs is within 6-12 dB of the theory. Possible reasons for this discrepancy are presented.
authors.affiliation: Department of Electronics, The University of York, Heslington, York, Y010 5DD, UK. jkae@ohm.york.ac.uk
authors.forename: Jeremy K A
authors.initials: JK
authors.lastname: Everard
authors.forename: Carl D
authors.initials: CD
authors.lastname: Broomfield
mesh_terms: D000669:Amplifiers, Electronic; D001152:Arsenicals; D016477:Artifacts; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005708:Gallium; D008872:Microwaves; D009991:Oscillometry / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D001152:Arsenicals; C043055:gallium arsenide; D005708:Gallium