Application of SAW Chirp Transform Filter in Spread Spectrum Communication Systems

Narrowband jamming of a spread spectrum signal can be filtered out in the frequency domain using acoustic surface wave convolvers as real time Fourier transformers. This is accomplished by employing modulated chirp signals as inputs. The particular frequency range in which the jammer occurs can be removed from the Fourier transformed signal by using a d.c. pulse and a balanced mixer. These concepts are discussed and experimental results demonstrating the use of the device as a Fourier transformer (with 110 MHz center frequency, 25 MHz bandwidth, and 14 μsec interaction range and 220 MHz center frequency, 50 MHz bandwidth and 14 μsec interaction range) are presented. The performance of the spread spectrum receiver using either pseudonoise or Barker codes and different jammers is discussed.