Continuous-wave surface-acoustic-wave delay-difference device.
A novel surface-acoustic-wave (SAW) device for continuous-wave (CW) delay-difference measurement or wideband interference-rejection at VHF frequencies is described and test results are given. The delay-difference device (DDD) operates at a center frequency of 160 MHz with a 31-MHz bandwidth over which root-mean-square amplitude ripple is 0.13 dB and need not be operated in a gated mode. A pair of input signals to the CW DDD may be at any frequency within the bandwidth of the DDD, modulated in any form, and even amplitude unbalanced to some degree by system amplifiers and still the CW DDD and its associated electronics will accurately measure the relative delay of the signals and interpret that as direction of arrival or phase as desired. Used in an interference cancelling mode the device tested shows an average 25-dB signal rejection over its 31-MHz bandwidth.
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Lockheed Res. Lab., Palo Alto, CA.