Abstract: A radar transponder for a stable and reliable response transmission upon reception of a weak radar signal having a reflection-conscious circuitry free from damage by a transmit effect, including a reception damage by the leakage of a powerful transmit wave signal and a transmission damage by the reflection of the powerful transmit wave signal. The reflection-conscious circuitry may include a circulator coupled to the transmit/receive antenna for selecting the powerful transmit wave signal or the weak radar signal, a receiving circuit provided after the circulator for receiving the weak radar signal, and an SPDT switch provided between the circulator and the receiving circuit for passing an input of the weak radar signal to the receiving circuit in a receiving period with its ground function dormant and for leading an input of the powerful transmit wave signal to a ground using the ground function in a transmitting period.

Abstract: A control circuit of a rader transponder produces pulses when the radar transponder detects a radio wave from a search radar. The pulses are sent to a sweep signal generator in which sawtooth waves are obtained through a first constant current circuit for linearizing the voltage-to-time characteristic in a falling portion of a sawtooth. The sweep signal generator further has a second constant current circuit for linearizing the voltage-to-time characteristic in a rising portion of a sawtooth.