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Radar Duplexer basics

This page covers Radar Duplexer basics.It mentions Radar Duplexer application note and Radar Duplexer vendors or manufacturers. It mentions difference between Branched duplexer, Balanced Duplexer and Ferrite Circulator types.

Most of the radar systems use single antenna in order to transmit as well as receive. As most of the radars use very high power transmitters and very sensitive receivers, radar with single antenna needs a front end which can take care of connect and disconnect functionalities. This is required to be perform on pulse to pulse basis. This is the main function of radar duplexer.

Duplexer acts as fast self actuating SPDT switch or Transmit/Receive Switch.

Signal in radar flows in both transmitting and receiving path as follows:

(Transmitting Path:)
Transmitter → Duplexer → Antenna → radio frequency wave → Target

(Receiving Path:)
Display ← receiver ← Duplexer ← Antenna ← Echo ← Target

Radar Duplexer Application Note

radar duplexer

As shown in the figure-1, the radar duplexer performs following functions:

• Connect the transmitter to the antenna (& disconnect the receiver) during the sending period.

• Connect the receiver to the antenna (& disconnect the transmitter) during the receiving period.

• Provide sufficient isolation between transmitter and receiver at all the times.

Refer Diplexer vs duplexer functions➤➤

There are three main types of radar duplexers viz. Branched duplexer, Balanced Duplexer and Ferrite Circulator. Following section mentions difference between them.

Branched Duplexer

Branched Duplexer

Figure-2 depicts branched duplexer. It is very old design but still in use in low cost radars used in small boats. It employs one or more ATR and a receiver protector. ATR is the short form of Anti Transmit Receive Tubes.

The main advantage of branched duplexer is simple in design, compact in size and its low cost. The main disadvantage of this duplexer is limited operational bandwidth.

Balanced Duplexer

Balanced Duplexer

Figure-3 depicts balanced duplexer. It uses features of two 3dB short slot type hybrid couplers in addition to switching element. It is used to control direction of power flow.

The advantages of balanced duplexer type is its power handling capability and operational bandwidth. The main disadvantages are physical size and relative port locations.

Circulator Duplexer

circulator duplexer

Figure-4 depicts circulator duplexer of ferrite type. It is most commonly used in modern radar systems. This 3-port circulator type duplexer directs power from port to port in only one direction. Refer 3 port circulator➤➤.

Radar Duplexer Manufacturers or Vendors USA

Following are the manufacturers or vendors of Radar Duplexer.

Manufacturers or vendors of Radar duplexer
Amplitronix, CA, USA
Anatech Electronics, NJ, USA
ClearComm Technologies, MD
CMT Filters
CTS Corporation
KR Electronics, NJ, USA
LUXCONN Technology, Korea
Maxim Integrated, CA, USA
Microwave Filters, Italy
Murata Electronics, GA
Panasonic, NJ
RTx Technology Co. Ltd, South Korea
Triquint Semiconductor, FL, United States
TELSA, Italy

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