Southwest Antennas is pleased to offer broadband coaxial isolators and circulators for use in transmit or receive systems. These devices are used to direct the flow of RF energy through a system and help prevent unwanted damage to sensitive components by reflected RF energy.

Southwest Antennas RF circulators and isolators for UHF, L, S, and C Band applications

We offer isolators and circulators in frequency bands from 698 MHz up to 8 GHz to cover the following applications:

  • Military / DoD radio systems
  • Federal and local law enforcement radio systems
  • Broadcast video systems
  • RF communication systems and wireless infrastructure
  • Aircraft communication systems
  • UAV / UGV communication systems

Contact Southwest Antennas for assistance with selecting the correct isolator or circulator for your application.


Circulators feature three RF ports, with each port directing input RF energy to the next port in sequence, such as from port 1 to 2, and from 2 to 3, and 3 back to 1. Circulators are useful in bi-directional applications, such as MIMO / MANET mesh radio systems where the same equipment may be used to both send and receive. Circulators can help direct the flow of RF energy in both directions through the RF chain.

RF circulator function block diagram example
Diagram 1: Simplified block diagram example of how RF circulators can be used in a bi-directional transmit and receive system to prevent damage to the Power Amplifier and Low Noise Amplifier.


RF circulators can also be used in switchless TX/RX systems. Where the TX power goes from the transmitter directly to the antenna without getting into the RX receive path and the received signal coming from the antenna goes directly to the RX receive path without affecting the TX transmit path. This is particularly useful in full duplex transceivers (transceivers that are transmitting and receiving at the same time on the same channel) and bi-directional amplifiers that are transmitting and amplifying power with a PA and receiving and amplifying power with an LNA at the same time.


Isolators have two RF ports and direct the flow of RF energy in one direction only and prevent it from reflecting back through previous components in the RF chain. Reflected RF energy is directed to a 50 Ohm load inside the isolator and is dissipated as heat. Isolators are useful for transmit-only applications, such as COFDM radios, where RF energy is flowing in one direction.

RF isolator function block diagram example

Diagram 2: Simplified block diagram example of how RF isolators can be used in a transmit-only system to prevent damage to the Power Amplifier by reflected RF energy.


RF isolators are also excellent devices to use to make antenna return loss / VSWR appear to be perfect from the transmitter's perspective. This is particularly useful in high power transmit systems that monitor reflected power levels from the antenna and fold back their Power Amplifier accordingly so as not to damage the PA with reflected power from the antenna when reflected power conditions are high.

RF isolators can also be effectively utilized in concealment applications where antennas are integrated inside enclosures or other devices and hidden from outside view. The concealment antenna tuning can change from use case to use case, and the installed isolator can protect the transmitter’s PA from damage when used in different RF environments.