Radar duplexer – Primary purpose In a radar front end, what is the main function of a duplexer with respect to sharing one antenna between the transmitter and receiver without mutual interference?

Introduction:
Radar systems typically use one antenna to transmit high-power pulses and receive extremely weak echoes. A duplexer is the device that switches and isolates the paths so a single antenna can serve both roles safely and efficiently. This concept is foundational in classic pulsed radars and remains important even where ferrite circulators or solid-state switches are used.

Given Data / Assumptions:

• One antenna shared between transmitter and receiver.
• High peak power during transmit, very low-level signals during receive.
• Need for rapid switching and strong isolation.

Concept / Approach:

A duplexer provides high isolation from the transmitter port to the receiver port during the transmit pulse, protecting sensitive receiver stages. Between pulses, it presents a low-loss path from the antenna to the receiver while isolating the transmitter. Classic implementations include branched duplexers with TR/ATR tubes and ferrite circulator-based duplexers.

Step-by-Step Solution:

Verification / Alternative check:

Receiver survival ratings and measured isolation confirm proper duplexer operation in deployed radars.

Why Other Options Are Wrong:

Options A, B, and C misstate the function. Option E confuses duplexing with power combining; a duplexer does not increase antenna gain.

Common Pitfalls:

Assuming an isolator alone suffices; underestimating the necessary peak power handling and recovery time.

Final Answer:

Allow one antenna to be used for transmission and reception without interference.