Research On Low Phase Noise Microwave Oscillator Based On Novel Bandpass Network

As communication technologies become more and more complex,there is a high requirement on the quality of microwave signal.Microwave oscillator is an important source for generating microwave signal,and its performance will directly affect the performance of a comunicaion system.The main goal of this thesis is how to effectively improve the phase noise performance of microstrip oscillator.We started from the theoretical phase noise model,explored novel oscillator topologies,and finally succesffully developed seveal microstrip oscillators.The main research work of the thesis include the following three parts:1.A single-ended oscillator based on a source/load coupled frequency selection network is proposed.By introducing the source/load coupling between the two quarter-wavelength stepped-impedance resonators(SIR),a narrow-band frequency selection network with general Chebyshev response is designed,whose second and third harmonics are deeply suppressed.The two transmission zeros near to the passband leads to a steep group delay,which improves the loaded quality factor QL and helps to reduce the phase noise of the oscillator.Based on this frequency selection network,a low phase noise microwave oscillator operating in the S-band was designed,with the working frequency of 1.989 GHz and the output power of 8.35 dBm.The phase noise at 100 k Hz offset the oscillation frequency of is-127.76 dBc/Hz,which is the best performance among S-band microstrip oscillators reported in domestic and foreign literature.In addition,and the second harmonic suppression is 46.03 dBc.2.A differential low phase noise oscillator is proposed.A balanced frequency selection network is developed on the previously-proposed frequency selection network based on source/load coupling.The balanced frequency selection network has high common-mode rejection within the entire frequency band.Then,a differential low phase noise microwave oscillator operating in the S-band is designed,with the working frequency of 2.025 GHz and the output power of 6.43 dBm.The phase noise at 100 k Hz offset the oscillation frequency of is-129.48 dBc/Hz,and the second harmonic suppression is 26.49 dBc.Compared with similar oscillators published at home and abroad,the phase noise of this design has obvious advantages.3.Two concurrent dual-frequency low phase noise microwave oscillators are proposed.Concurrent dual-frequency oscillator A utilizes a cross-coupled third-order duplexer as the frequency selection network of each channel,connected in a back-to-back form to output the oscillation signal.Firstly,we uses two low-noise amplifiers working in different operating frequency bands to design the sub-oscillator loop.The measurement results show that the dual-frequency operating frequencies are2.061 GHz and 3.427 GHz,the corresponding output powers are 1.06 dBm and-4.27 dBm,respectively.The phase noise at 100 k Hz offset the oscillation frequency of is-113.94 dBc/Hz and-120.88 dBc/Hz,the harmonic suppression near the oscillation frequency is greater than 23.02 dBc.The concurrent dual-frequency oscillator B uses a second-order duplexer based on a dual-mode resonator as the frequency selection network of each channel.The measurement results show that the oscillation frequencies of the dual-frequency are 2.016 GHz and 3.305 GHz,and the corresponding output power is 7.10 dBm and-3.22 dBm,respectively.The phase noise at 100 k Hz offset the oscillation frequency of is-114.98 dBc/Hz and-120.01 dBc/Hz,respectively.The harmonic suppression near the oscillation frequencie is greater than 32.42 dBc.