ELECTRONICALLY TUNABLE YIG FILTERS WITH ELECTRONICALLY VARIABLE BANDWIDTH.

The purpose of this work was to develop a YIG bandpass filter electronically tunable from 2 GHz to 4 GHz, with a bandwidth electronically variable from 5 MHz to 50 MHz. In this report various methods of varying the bandwidth electronically are discussed and a brief theoretical analysis is given for each. The three principal approaches are 1 changing the angle between the DC biasing field and the RF magnetic field 2 double-tuned coupled stages with voltage-variable tuning networks 3 stagger-tuned isolated stages with voltage-variable tuning networks. Stagger-tuned stages was the approach finally selected and this case is analyzed in greater detail. Experimental results bandwidth, insertion loss, VSWR, etc. as measured on the finished unit are presented, followed by a discussion of the results. A discussion of the auxiliary circuits magnet, driver circuits and bias circuits is included and for convenience, a summary of design equations for a two-stage stagger-tuned bandpass filter appears in the Appendix. Author