Radar systems – Branched duplexer components required In radar transmit–receive switching, what gas-discharge protection tubes are required for a branched duplexer so that a single antenna can be shared safely by the transmitter and receiver?

Introduction:
Radar front ends must use the same antenna for high-power transmission pulses and for receiving extremely weak echoes. A duplexer performs this switching and isolation. In classic pulse radars, the branched duplexer architecture relies on gas-discharge devices that become conductive only during transmit, thus protecting the sensitive receiver while minimally degrading receive performance.

Given Data / Assumptions:

• Single radar antenna shared between transmitter and receiver.
• Pulse radar with high peak power during transmit and very low-level signals during receive.
• Need fast, reliable isolation and low insertion loss on receive.

Concept / Approach:

The branched duplexer uses two special tubes: the TR (Transmit-Receive) tube placed in the receiver branch and the ATR (Anti-Transmit-Receive) tube placed in the transmitter or antenna branch as required by the topology. During the transmit pulse, strong RF triggers ionization within these gas tubes, forcing them into a low-impedance state that reflects or shunts energy away from the receiver. Between pulses, the gas de-ionizes, returning the path to high impedance and permitting low-loss reception.

Step-by-Step Solution:

Verification / Alternative check:

Historical radar designs and training manuals specify the combination of TR and ATR tubes in branched duplexers for adequate isolation and low receive loss.

Why Other Options Are Wrong:

TR only or ATR only provide insufficient isolation in a branched network. No special tubes would expose the receiver to damage. A ferrite isolator alone is not adequate for the extremely high peak powers and the switching function required.

Common Pitfalls:

Confusing circulators/isolators with gas-tube duplexers; assuming one tube can cover all isolation needs; overlooking ionization recovery time in pulse design.

Final Answer:

Both TR and ATR tubes.