Design And Research Of The High Performance X-Band Oscillator

The exponential growth in wireless communication, military radar, electronic countermeasures, bio-medical, space remote sensing and other related fields has increased demands for the source of microwave signals. Oscillator is a key device in these fields to provide high spectral signal source. We expect oscillator has advantages of low phase noise, high output power, high stability, compact size, and low cost, etc.The researching and designing of the resonators that can be realized by the PCB process with high Q factor is particularly significant because of the X-band oscillator design requirements for low phase noise, high spectral purity, and low cost. Since SIW has these above excellent advantages, this paper will focus on its studying, modeling and simulating. And the designed substrate integrated waveguide(SIW) resonators will be frequency selective elements for both negative-resistance oscillator and feedback oscillators. The modeling and simulating for SIW resonators and oscillation circuits will obtain low phase noise, high output power and compact size.This paper has designed three projects:By employing quarter-mode substrate integrated waveguide(QMSIW) resonator(nearly 25% size of SIW) for negative-resistance oscillator with compact size and high Q factor in first project, the measured oscillation frequency is 9.03GHz; the output power is 5.04 dBm with 20 mW power consumption; the phase noise is-98.8dBc/Hz@100kHz and-120.4dBc/Hz@1MHz. Finally-184.9d Bc/Hz. can be obtained for the figure of merit(FOM).By employing high Q factor TE102 mode SIW resonator with differential outputs for feedback oscillator, the measured oscillation frequency is 9.01GHz; the output power is 1.8dBm with 20 mW power consumption; the phase difference between the two output ports is approximate 180o, the phase noise is-104.3d Bc/Hz@100kHz and-133dBc/Hz@1MHz. Based on above,-190.4dBc/Hz can be obtained for the FOM. In this project, the phase difference can be realized 180 ° without using of one microwave balun or two active devices in the output ports of oscillator, as a result, the size and cost of the oscillator circuit are saved.Two high Q factor diplexers are cascaded back-to-back to realize two loop sub-oscillators in third project. The isolation of the two sub-oscillators is provided by diplexers, which can suppress the interactions between the two oscillation signals. The diplexer is composed of two dual-mode SIW filters by T-junction. By employing the diplexers as the frequency selective element, it can realize low phase noise. The simulated results show the concurrent dual-band oscillator can output two oscillation signals of 9GHz and 10.06 GHz simultaneously. The output power of the two oscillation signals are 4.982 dBm and 5.090 dBm, respectively. The phase noise of the two oscillation signals are-134.7dBc/Hz@100kHz,-155.0dBc/Hz@1MHz and 134.1dBc/Hz@100kHz,-154.1dBc/Hz@1MHz, respectively.