Research On Techniques Of Self-oscillating Mixer Based On Substrate Integrate Waveguide

In recent years,with the rapid development of wireless systems such as communication systems and radars,miniaturization and high performance RF microwave devices have become increasingly important.In traditional wireless systems,mixers and oscillators are necessary as modern communication components which usually consumes vast areas.Self-Oscillating Mixer(SOM)can achieve simultaneous oscillation and mixing functions by using a single active device.It is designed for compact,Low-power transceiver system provides a new choices.As a new type of guided wave structure,substrate integrated waveguide has the advantages of low insertion loss,high power capacity and low radiation,and can be processed by ordinary PCB technology.Combining technology of self-oscillation mixing and substrate integrated waveguide can design low-profile,compact,self-oscillating mixer that can be used to design low-power dissipation,miniaturized,planar communication systems.In this paper,the design of the self-oscillating mixer based on substrate integrated waveguide is introduced.Firstly,the structure,characteristics and application scenarios of the integrated waveguide are introduced.Then,the transition structure of waveguide and microstrip line was designed and simulated.On the basis of this,the high-Q substrate integrated waveguide resonator is designed on the feedback loop to stabilize the oscillation signal by using the characteristics of the substrate integrated waveguide high quality factor.Then,the SIW resonator is used to design the parallel feedback oscillation circuit.When the circuit satisfies the oscillation condition,the local oscillation signal will be generated in the loop,and then the RF signal will be coupled into the loop through the coupler to be mixed and passed through the low-pass filter in the transistor of the drain to get the IF signal.In view of the modern communication system such as radar receiving system,when the frequency of the RF signal changes,the local oscillator signal frequency can change to keep the frequency of the IF signal constant.The second part of this paper uses a new type of variable capacitance diode and substrate integrated waveguide coupling structure for design a fixed IF self-oscillating mixer based on substrate integrated waveguide,which can be used to continuously adjust the oscillation frequency of the self-oscillating mixer by adjusting the bias voltage of the varactor diode adjust.The two self-oscillating mixers designed in this paper have been simulated,processed and verified by test.The final test results show that the frequency loss is less than 7d B and the phase noise is better than-85 d Bc/Hz@100k Hz when the frequency range of the input RF signal is in the range of 11.5-12.5GHz.For the fixed IF self-oscillation When the bias voltage of the varactor diode is adjusted between 0-16 V,the local oscillator frequency is continuously adjustable between 9.95 GHz and 10.39 GHz and has a frequency gain better than 4d B over the entire tuning range,and has the best phase noise of 95.9d Bc/Hz@100k Hz when the varactor was bias at the voltage of 14 V.