| Communications

Tunable, High-Isolation RF/Microwave Circulator

This device improves both detection range and reception.

A new high-isolation RF circulator provides enhanced detection ranges (radar) and improved reception (communications) by reducing signal leakage and undesirable internal reflections between ports at a tuned frequency (or frequency range) of interest. Isolation values exceeding 70 dB have been demonstrated, which far exceeds the 20 dB typical to conventional three-port circulators.

An isolation comparison between the traditional circulator (red) and the new invention (blue). Values are experimentally determined.

The new circulator was invented to address shortcomings in monostatic radars, which have traditionally been restricted to pulse mode operation due to false target detection caused by internal leakage and reflections in conventional circulators. The invention eliminates these internal artifacts and allows monostatic systems to operate in continuous mode, improving long-range detection and overall signal purity. The benefits offered by this system for radar can be extended to other applications that use RF circulators, including communications, spectrum management, and e-warfare.

The tunable, high-isolation circulator relies on destructive interference between two conventional circulators connected in a parallel configuration to cancel the internal reflections and signal leakage between ports. First, a power splitter is utilized to divide the incoming signal into two identical channels. By matching the load on each circulator, nearly identical internal reflections and leakage are generated in each circulator. Each circulator is further connected to a phase trimmer so that the phase offset between the two circulators may be adjusted to cancel the internal leakage and reflections that occur once the two channels are recombined in a power combiner. The resulting signal purification occurs solely in the analog regime, providing increased effectiveness relative to known isolation methods that require digital conversion and subsequent post-processing.

The circulator reduces leakage signals and internal reflections, resulting in improved noise floor and reduced false alarms. It allows for continuous mode operations, translating to more time on target. It enables much weaker signals to be detected at longer ranges, and offers extensive system flexibility. The circulator is scalable to different frequency ranges and power levels, and is compatible with both new builds and retrofits.

For more information, contact Joan Wu-Singel, Senior Technology Manager, at This email address is being protected from spambots. You need JavaScript enabled to view it.; 406-994-7705.