K-band Dielectric Resonator Oscillator Phase-locked Frequency Source

The microwave frequency source which is the basic energy source of the RFsystem is an important part of the RF system. The rapid development of electronictechnology put forward higher requirement on the frequency source. The outputfrequency is higher, the bandwidth is wider, and the phase noise is lower. In this paper,frequency source with low phase noise is studied, and the main task is to produce aK-band low phase noise frequency source. The main research contents are dielectricresonator oscillator (DRO) and sampling phase phase-locked loop. The main contentsare as follows.The general theory of microwave oscillator is studied using complex domainmethod and phasor method. The start-up condition of oscillator is analyzed in detail.The start-up criterion convenient for engineering analysis is summarized. The commonreasons of failing to oscillate in practical engineering are discussed in detail. Thegeneral structures of the DRO, as well as their design methods are listed. Problemsoften encountered and the corresponding solutions are also discussed.Some traditional oscillators as well as a harmonic oscillator with new structureusing parallel feedback DRO are listed. Compared with the traditional push-pushoscillator, the output power of the new structure is significantly increased with the samefundamental rejection. Finally a method taking advantage of the microstrip coplanarwaveguide (CPW) to simplify the design process is proposed.The basic theory of sampling phase detector and phase-locked loop is analyzed.The loop noise and the stability of the feedback loop are studied in detail. Then, anX-band phase-locked loop is designed and tested. The measured results are consistentwith theoretical analysis, and meet the design specifications.The scheme of a K-band low phase noise frequency source is discussed. Afterprogram demonstration, the final scheme is selected. The modules in the system areanalyzed and discussed, and each module indicator is given. Finally, the circuitschematics, the simulation results, processing and testing, and the measured results areproposed. The output frequency is19GHz, and the output power is9.5dBm. The phase noise is-88.11dBc/Hz@1kHz,-92.08dBc/Hz@10kHz and-87.18dBc/Hz@100kHz. Theharmonic suppression is greater than23dB and the spurious suppression is greater than36dB. The measured results are consistent with theoretical analysis, and basically meetthe design specifications. It indicates that the scheme adopted is reasonable and thetheoretical analysis is correct.