Intrinsically microwave tunable resonator designed on silicon

The potential of an intrinsically microwave tunable resonator consisting in a switchable diode and a stub directly co-designed on the same silicon substrate is presented. Thanks to this substrate, the semiconductors properties can be associated directly to the electromagnetic wave propagation. Compared with the current technology, the absence of soldered components offers a great flexibility in the design of microwave tunable devices. The active element is based on an integrated and distributed N+PP+ junction which allows the tunability of the resonator by simply applying a low bias voltage. It is demonstrated that high doping levels of the diode and resonator can lead to good performances. Two stubs, switchable from open-ended (λ/2 at 4 and 3 GHz) to short-ended (λ/4 at 2.1 GHz) using a low bias voltage, were designed, fabricated and characterised. A good agreement was obtained between simulations and measurements and each resonator presents insertion losses lesser than 2 dB.