Diplexers, triplexers and duplexers for RF measurement technology

How are diplexers and triplexers used?

A diplexer is a three-port component that separates or combines signals based on their frequency, so that, for example, two different frequency bands (such as 2.4GHz and 5GHz Wi-Fi) can be used simultaneously via a single antenna. A triplexer performs this function for three frequency ranges.

Diplexers and triplexers are crossover networks for RF and microwave applications. They separate or combine multiple frequency ranges via a common RF connector. These passive components consist of tuned filter paths and process the various frequency bands simultaneously.

Typical areas of application include:

• Antenna and communication systems

• Radar and satellite technology

• RF transmission and reception systems

• Harmonic and load-pull measurements

What is the difference between a diplexer and a duplexer?

Diplexers and duplexers enable the use of a shared antenna, but differ in their function.

• Diplexer (frequency separation): It separates or combines different frequency bands, usually employing filter structures such as low-pass and high-pass filters. It is used in the same way as a crossover when different frequency ranges are to be routed via a single antenna.
• Duplexer (directional separation): It separates the transmission and reception paths when the transmission and reception signals operate at different frequencies. It protects the sensitive receiver from high transmission power and enables simultaneous transmission and reception, for example in repeaters or radar systems. Duplexers are primarily used to route transmission and reception signals via a single antenna and to reliably isolate both signal paths from one another.

In harmonic load-pull measurements, a diplexer enables the separate tuning of the fundamental frequency F0 and its second harmonic 2F0. The common port is connected to the DUT. The two frequency-selective outputs lead to separate tuners, so that the impedances for the fundamental and the harmonic waves can be set independently. Mutual interference between the two measurement frequencies is now determined solely by the isolation provided by the diplexer. Therefore, very high-quality diplexers with the lowest possible losses should be used for such measurements.

A similar setup using a triplexer and three tuners allows independent tuning of F0, 2F0 and 3F0.