A Saw Filter with Improved Frequency and Time Domain Characteristics for the Frequency Measurement of Narrow RF Pulses.

摘要

If contiguous filter banks are to be used in receivers to accurately measure the frequencies of narrow RF pulses, particular care must be taken in selecting the time and frequency domain characteristics of the individual channels. Ideally, filters which are both highly selective in the frequency domain and relatively distortionless in the time domain are sought. Obviously these conflicting requirements can never be fully satisfied. However, by exploiting the design flexibility of SAW devices, a new Flat Exponential Filter (FEF) has been developed which possesses excellent performance in both domains and allows quantitative tradeoffs between the two to be easily made. This linear phase FEF has a flat frequency characteristic in-band and an exponentially decaying out-of-band response; the decay of which can be controlled by varying a single design parameter. In this paper the design and performance of SAW FEF's will be described in detail. Theoretical and experimental results for both a single channel, 330 MHz center frequency, 20 MHz bandwidth FEF plus an eight channel FEF filter-bank multiplexer will be provided. Optimum interconnection techniques using matching networks, distortions resulting from filter interaction, insertion loss and triple transit suppression will be discussed. (Author)