RF Circulators + RF Isolators

An RF circulator uses a ferrite element biased by a permanent magnet to create non-reciprocal signal routing between its ports. The magnetic properties of the ferrite cause electromagnetic waves to propagate preferentially in one rotational direction. This means a signal entering any port exits the next port in sequence, while being isolated from the remaining port. The quality of the ferrite material directly determines the circulator’s insertion loss, isolation, bandwidth, and power handling.

In a duplexer configuration, the antenna connects to one port, the transmitter to a second, and the receiver to a third. The circulator’s rotational behavior routes the transmit signal to the antenna and the received signal to the receiver, keeping them separated. The isolation between the transmit and receive ports — determined largely by the ferrite material quality — prevents the high-power transmit signal from overwhelming the sensitive receiver.

Isolation is the measure of how well an RF device prevents signal leakage between ports that should be decoupled. In a circulator or isolator, higher isolation means less unwanted signal reaches the protected port. Trans-Tech’s devices achieve industry-leading isolation through our proprietary ferrite materials with the tightest linewidth specifications in the market.

Cascading two isolators will increase total isolation, but not exactly double it in dB terms due to additional insertion loss and impedance interactions between the devices. The practical improvement depends on the specific devices and how they’re integrated. Our applications engineers can help you determine whether cascading isolators or selecting a higher-isolation single device is the better approach for your system.