Research On Novel Frequency Selection Networks And Their Application In Microstrip Low Phase Noise Oscillators

As the core component of microwave signal source,the performance of oscillator directly affects the performance of communication systems.The rapid development of radar and wireless communication technology,especially 5G,makes the requirement on microwave oscillators more and more stringent.Oscillators are required to have good performance on low phase noise,high output power,excellent harmonic suppression,miniaturization and low cost.One of the most important performance indicators is phase noise.Therefore,this thesis is dedicated to the development of ultra-low phase noise microstrip oscillators based on the study of new frequency selective network(FSN).The main research work is as follows:1.A low phase noise single-ended parallel feedback oscillator based on a quasibandpass FSN with multiple transmission zeros is proposed.By introducing source/load coupling between two coupled quarter-wavelength resonators,the FSN can theoretically realize a canonical second-order general Chebyshev bandpass response with two transmission zeros.In addition,the feedlines with short-circuited ends are specifically designed to generate more transmission zeros.Therefore,this FSN has a quasi-bandpass response with multiple transmission zeros so that high group delay and good out-of-band performance are achieved.Such feature plays a vital role in oscillator performance.Experimentally,the single-ended oscillator based on this FSN achieves an output power of up to 9.61 d Bm at the operating frequency of 1.976 GHz,a second harmonic suppression of 48.21 d Bc and a phase noise as low as-129.85 d Bc/Hz@100 k Hz.The phase noise performance of the oscillator in the L to S band is better than those of similar components reported at home and abroad.2.A single-ended parallel feedback oscillator with low phase noise is proposed based on a dual-mode stepped impedance FSN.The FSN is miniaturized by using interdigital capacitors and stepped impedance resonator.Based on mixed electromagnetic coupling,the FSN has higher group delay and better frequency selectivity.In order to reveal the intrinsic physical mechanism,an equivalent circuit model is established for analysis.The equivalent relation between lumped equivalent circuit and microstrip structure is established to simplify the design.Based on this FSN,a single-ended parallel feedback oscillator is designed.The experimental results show that at the oscillation frequency of 2.047 GHz,the phase noise of this oscillator is as low as-129.91 d Bc/Hz@100 k Hz,while the second and third harmonic suppression is high at 40.23 d Bc and 19.35 d Bc respectively.This oscillator demonstrates better phase noise performance and harmonic suppression.3.A differential parallel feedback oscillator with low phase noise based on a source/load coupling balanced FSN is proposed.The source/load coupling is introduced into the FSN to obtain better frequency selectivity and higher group delay.Furthermore,a pair of non-resonant resonators is embedded between the two resonators to enhance the performance of the FSN.To highlight the performance benefits of the differential oscillator,a single-ended oscillator is designed based on a two-port FSN with the same topology.Finally,the two oscillators are processed and tested respectively.The singleended oscillator achieves an output power of 8.88 d Bm and a phase noise of-132.01 d Bc/Hz@100 k Hz at the oscillation frequency of 1.953 GHz,the second and third harmonic suppression reaches 32.32 d Bc and 19.29 d Bc,respectively.The differential oscillator has an output power of 8.84 d Bm and a phase noise of-134.99 d Bc/Hz@100k Hz at the oscillation frequency of 1.97 GHz,the second and third harmonic suppression reaches 30.84 d Bc and 17.82 d Bc,respectively.