Non-linear spread spectrum transmitter/receiver for a homing system

In a detection, track and homing system including a spread spectrum transmitter adapted to transmit signals to a remotely located target and a spread spectrum receiver adapted to receive signals reflected from the target in response to the transmitted signals impinging thereon where the velocities between the transmitter/receiver and the target are relatively high, surface acoustic wave apparatus providing doppler invariant pulse compression/expansion comprising:

• a. a piezoelectric base;
• b. a plurality of spaced apart interdigitated fingers formed on a surface of said base and interconnected to provide an input transducer and an acoustically coupled output transducer;
• and
• c. the fingers forming the output transducer having spacings therebetween which vary nonlinearly in a generally hyperbolic function for reducing frequency shift errors due to doppler effects.