MPT Inc. – Microwave Products and Technology

Filters in Phased Arrays

When most people think of phased arrays, they normally don’t think about filters until later in the development process. However, filters can be an important part of some phased arrays. This is especially true for arrays used in communication systems or wide band radar systems.

In full duplex communication systems, the transmitter and receiver are transmitting at the same time. If not managed properly, the transmit signal can leak into the receiver input which will result in lower receive sensitivity. Or, worse, the low noise amplifier in the receiver can be permanently damaged resulting in failure of the phased array.

One way to avoid this is to use active cancellation of the transmit signal into the receive path. These approaches can be cost prohibitive for most systems using current technology but may be the best alternative if the transmit and receive frequencies are the same.

An alternative is to use a diplexer (or multiplexer) connected between the antenna and transmit/receive module. It will perform the duplex function. The diplexer is formed with two filters–one for the transmit frequency band and the other for the receive band. Of course this assumes the transmit and receive bands are at different frequencies and separated in frequency enough that a practical implementation of a diplexer can be used. In this example, the function of the diplexer is essential to the phased array meeting its performance requirements.

Filters are also used in other parts of a phased array system. Maybe we will discuss those other uses in another blog post.

If you would like to know more about how MPT can supply your next phased array solution, then reach out to us today: or (951) 252-6336.