Study Of Phase Noise Model In Nonlinear Circuits And Its Application

Oscillators play a key role in communication and radar systems. The performances of whole system are limited by the phase noise of oscillator. With the rapid developments of electronic technique, the requirement of phase noise in oscillator is more stringent. Therefore, it is valuable to investigate the phase noise model of oscillator and low phase noise oscillator design. This dissertation mainly focus on the study of circuit-based oscillator nonlinear phase noise analytic model and low phase noise planar oscillators, including push-push oscillator, active resonator oscillator and feedback-type harmonic oscillator. The main works and innovative achievements of the dissertation are summarized as follows:(1) The neglect of harmonics is a main limitation in conventional Kurokawa analysis. In order to overcome this constraint, an analytic model for oscillator phase noise based on multi-harmonic Kurokawa method is proposed. Using poly-harmonics distortion(PHD) modeling approach, the circuit parameters of nonlinear components in the oscillator are derived by the super-position principle taking into account the influence of harmonics. In addition, two types of noise source: additive noise and frequency converted noise are discussed in detail. The more accurate analytic expressions for amplitude and phase noise spectra of oscillator are obtained, which are verified in a Van der Pol and a nonlinear FET based Colpitts oscillator example. In these two examples, the calculated results of phase noise spectra match well with the simulations results obtained by Harmonic-balance simulator, and the quantitative results from proposed methods are more accurate with respect to single frequency Kurokawa method.(2) In order to obtain low phase noise, the planar push-push oscillators are studied. A differential transmission line loaded with a coupled-pair of multiple split ring resonators(MSRR) is proposed to achieve weak coupling between two sub-oscillators, and the frequency selectivity of common resonator is improved. An X-band push-push oscillator utilizing this structure is designed, and a phase noise optimization method based on active quality factor of oscillator is adopted in the design. Then, In order to miniaturize the size of common resonator, a compact spiral resonator array based on source-load coupling is proposed. The structure can provide high frequency-selectivity and anti-phase current simultaneously, which act as a phase coupling network in Ku-band push-push oscillator. At last, a differential transmission line loaded with circular SIW cavity is proposed. The odd TM110 mode in SIW circular cavity ensures the out-of-phase operation mode of two sub-oscillators, and the reflective-type characteristic of the structure is preferable in negative resistance oscillator. A K-band push-push oscillator based on this structure is designed. The experiments results indicate that the proposed push-push oscillators exhibit low phase noise and good suppression of fundamental frequency component.(3) In order to overcome the quality factor limitation in planar resonator due to the conductor and dielectric loss. The application of active resonator technology in SIW structure is investigated. Firstly, a transmission line(TL) loaded with active SIW resonator is proposed. By compensating the energy loss in SIW cavity using coupling negative resistance method in active resonator, the loaded quality factor has been improved significantly. The proposed TL structures loaded with active and passive SIW resonators are adopted in X-band oscillators. The measured results show that the phase noise of oscillator base on active SIW resonator is 9 dB better than the oscillator based on passive SIW resonator. Then, in order to enhance the group delay of filer, an active SIW dual mode filter is proposed. The active feedback loop structure is adopted to compensate the loss in filter. The circuit parameters have been optimized to minimize the effect of added noise induced by active device. An X-band feedback oscillator is designed based on the active dual-mode SIW filter. The measured phase noise is-118.9 dBc/Hz@100 kHz at the centre frequency of 10.94 GHz, which is 5.3 dB better than the counterpart based on passive SIW dual mode filter.(4) In order to enhance the output frequency and minish the frequency pulling induced by load variation, a type of feedback harmonic oscillator is studied. In order to simplify the oscillation circuit, the frequency-selecting component at fundamental frequency and output-coupling component at second harmonic are replaced by a diplexer. Therefore, a high isolation is realized between feedback-loop oscillation circuit and output load at fundamental frequency. Compared to conventional fundamental frequency oscillator, the impact of reflected signal from load is reduced efficiently. A feedback-type harmonic oscillator and a feedback-type fundmental frequency oscillator are designed based on SIW-CMSRR diplexer and filter, respectively. The simulation and experiment results indicate that the frequency pulling of harmonic oscillator is reduced significantly compared to fundamental frequency oscillator, and the phase noise performance of harmonic oscillator is improved compared to a frequency doubler.