The Design of Wide-Band Scatter Systems

The modulation bandwidth that a scatter system can handle is mainly determined by the transmitting and receiving antenna beamwidths. A higher carrier frequency, therefore, permits the use of a smaller antenna. The transmitter power may then be chosen to give an adequate carrier-to-noise ratio. A method of reducing the differential delay in diversity receivers which extends the modulation band a given scatter system can handle, has been developed. IF amplifiers in wide-band scatter systems are a particularly difficult compromise between performance and ease of maintenance. To date it has not proved possible to use phase equalizers on these circuits, and between 1 and 2 db of threshold must thereby be sacrificed. IF combining is attractively simple, but even with delay correction, it is doubtful whether the phase can be locked to the required accuracy at low carrier-to-noise ratios. The base-band combiner is more complex but can be made to operate up to modulation frequencies of 5 mc. Its operating range is somewhat restricted, however.