Choke ring antenna

It consists of a number of concentric conductive cylinders around a central antenna.

The first choke ring antennas were invented at JPL;[2] since 1989 they have been improved and extended by many companies.

[citation needed] Due to its intricate construction, it is often enclosed in a protective cover or radome when placed outside and exposed to the elements.

[citation needed] Choke ring antennas have excellent phase center stability, polarization purity, suppression of radiation below the horizon and multipath rejection.

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Patent diagram of a choke ring antenna [ 1 ]
Choke ring antenna at a DGPS Reference Station