Low-cost frequency modulated ferrite loaded SIW oscillator for high-power microwave transmitter

A low-cost frequency modulated feedback-loop oscillator for high-power microwave transmitter on the basis of a Ferrite Loaded Substrate Integrated Waveguide (FLSIW) cavity is proposed and demonstrated for the first time. The proposed structure is low-cost as its fabrication involves standard PCB process and the integration of high-power handling ferrite allowing the combination of an oscillator and high-power amplifier within a single device. With the application of an external magnetic bias, the resonant frequency of the FLSIW cavity is controlled to adjust the feedback-loop oscillation conditions and tune the oscillator frequency. It is also demonstrated that, by applying an alternating magnetic bias, the output signal of the oscillator can be modulated. The validation of the proposed oscillator consists of a multilayer and single layer X-band prototype. The fabricated multilayer component is based on a four ferrite slab loaded SIW cavity achieving a 16% frequency tuning. The oscillator with a frequency tuning range of 210 MHz centered at 11.91 GHz with a fairly constant output power and a phase noise of 90 dBc/Hz at 100 kHz offset is demonstrated. The single layer prototype is controlled by a double winded electromagnet to achieve both frequency tuning and modulation. A 10 kHz frequency modulation is demonstrated. This type of oscillator is suitable for low-cost highpower microwave transmitter for possible use in FMCW radar.