TABLE OF CONTENTS 'The gods help those who help themselves.'
Aesop
Chapter 7 showed the radar cross section of a passive object to be inherently associated with its physical size, because no dumb object can reflect more power than it intercepts from the interrogating radar. A metallic reflector may be considered as a receiving antenna directly feeding the selfsame antenna in transmit mode. Insertion of an amplifier (taking power from a battery) between these antennas would clearly boost the reflection or response. An active reflector or radar target enhancer (RTE) is such an antenna/amplifier/antenna device. The poor performance associated with physically small passive reflectors or antennas is augmented by the amplifier, so RCS is no longer tied to size. It is not possible to modulate the response of an active reflector of this kind with any form of identification code. The response is merely an amplified replica of the interrogation, with the same frequency and pulselength, appearing indistinguishable from an ordinary passive echo.
Replacing the amplifier with a miniature radar transmitter, triggered to deliver a pulse or coded group of pulses when the received interrogation pulse exceeds an amplitude threshold, turns the device into a racon (radar responder beacon) or search and rescue transponder (SART), which, although operationally distinct, conceptually differ from one another only in their response identification codes. Radars can determine range and bearing of stations carrying RTEs or racons in the usual way. Range of SARTs is subject to some uncertainty because of...
