ANALYSIS OF 2-PORT MAGNETOELASTIC DELAY LINES AS PULSE-COMPRESSION FILTERS

A Critical review is given of the properties of magnetoanstic delay lines, employing yttrinm iron garnet (YIG) and having physically distinct input and and output prots. Attention is directed to two coafigurations in volving the materials YIG and yttrium aluminum garnet (YAG), namely the YAG (nλg/4)-YIG-YAG(nλg/4) emplying YAG quarter-were plates λg/4, and the YIG-YAG-YIG structures. These offer the highest isolation between input and output ports cupled with the lowest insertion loss for magnetoelastie waves, under specified conditions of microwave frequency and delay. The transfer function through the YAG material are derived in each configuration for the cases of 1) imperfect matching between the asoustic characteriptie impedances of YIG and YAG, with perfect optical bonding, and 2) imperfect optical bonding. Conventional matched filter theory is used to evaluate the time response of each magnetoelastic delay line, assuming linear variation of delay with frequency, to a linearly frequency-modulated palse. It is established that the configuration employing quarter-wave plates gives desirable weighting of the main pulse. However, a spurious echo of unacceptable level exists, which is delayed approximately by an acoustic round trip in the nλb/4 plate, when a reasonable bandwidth is employed. Analysis shows that this difficulty does not arise for the YIG-YAG-YIG configuration. However, an external weighting network is required for range sidelobe redaction. Copyright © 1968 by The Institute of Electrical and Electronics Engineers, Inc.