The development and current status of microwave ferrite technology is reviewed in this paper. An introduction to the physics and fundamentals of key ferrite devices is provided, followed by a historical account of the development of ferrimagnetic spinel and garnet (YIG) materials. Key ferrite components, i.e., circulators and isolators, phase shifters, tunable filters, and nonlinear devices are also discussed separately.

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A new type of frequency selective signal-to-noise enhancer is described, which shows instantaneous bandwidths of more than 800 MHz at frequencies up to 4.2 GHz. The device consists of an epitaxial YIG film in contact with a narrow microstrip transmission line. Magnetostatic surface waves in the YIG film act as saturable absorbers of power from the microstrip line. Using a 26.6-μm-thick YIG film on a 23-μm-wide microstrip line of 21 mm length, resulted in a small signal (<−6 dBm) attenuation of in excess of 25 dB. The attenuation was reduced by 15 dB when the input power was increased to +10 dBm.

A new broadband frequency selective limiter which provides over 14 dB of limiting across more than an octave bandwidth is described. The limiter is fabricated with epitaxially grown YIG films in a stripline configuration and has a threshold power level of below 0 dBm. Multiple FSLs have been cascaded with amplifiers to allow compression of microwave signals with a power range of 60 dB into a range of less than 5 dB. BACKGROUNDBroadband EW or ESM receiver systems need to intercept signals over wide frequency bands and over a wide dynamic range with a high probability of intercept and with accurate measurement capability. This must be done within a complex signal environment that includes low, medium and high duty cycle and CW signals and other intentional and unintentional interference. The receiver must accurately sense signals in the presence of other signals which may be much stronger. A number of receiver sensor approaches are inherently not compatible with these requirements. Channelized systems, such as the Bragg cell receiver, have the potential to meet these requirements if certain components are developed, and if the system is properly engineered.

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