Reduced transposed flicker noise in microwave oscillators using GaAs-based feedforward amplifiers

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 54; no. 6; pp. 1108 - 1117
• Main Authors: Everard, J.K.A., Broomfield, C.D.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-06-2007; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: 1f noise; Amplifiers; Amplifiers, Electronic; Applied sciences; Arsenicals; Circuit properties; Control systems; Control theory; Dielectrics; Electric, optical and optoelectronic circuits; Electronics; Equipment Design; Equipment Failure Analysis; Error correction; Exact sciences and technology; Feedback; Feedforward; Gallium; Microwave amplifiers; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwave oscillators; Microwaves; Noise; Noise levels; Offsets; Oscillators; Oscillometry - instrumentation; Oscillometry - methods; Phase noise; Power amplifiers; Power transmission lines; Reproducibility of Results; Sensitivity and Specificity; Time Factors; Transmission line theory; Phase noise; Gallium arsenides; Dielectric resonator; Noise reduction; Sustaining amplifier; 1/f noise; Modeling; Transmission line; Feedback; Sapphire; Thermal noise; Microwave resonator; Power amplifier; Threshold
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2007.365

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 arid 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 Q o of 180 and two sapphire-based, dielectric resonator oscillators (DROs) with a Q o 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 (I/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.