JRC X-band limiter and directional coupler assembly, tuned to 9.489GHz 

I tested all three combinations of signal paths with an HP 8720B VNA. Each VNA trace is preceded by a photo showing the test setup. The coax cable with the orange band indicates the VNA-driven port for S21 measurements.

The first pair of plots shows the through-path response. The second pair shows the limiter-side waveguide port to SMA coupled-port response with the coupled side port terminated. The third pair shows the coupler-side waveguide port to SMA response with the limiter port terminated.

The through path operates with 1-2 dB insertion loss between 9.28 and 10.23 GHz. Some portion of the measured loss is attributable to the waveguide-to-coax adapters used during testing.

The coupled port shows 2.5 dB insertion loss from the limiter side and more than 20 dB isolation in the reverse direction (blue trace).

Driving the coupler waveguide with the limiter port terminated shows excellent correlation between the minimum insertion loss at 9.4892 GHz (Marker 2, yellow trace) and the maximum reverse attenuation at the same frequency (22.5 dB, blue trace).

Markings on the assembly include:

• JRC NJS6918
• 3602871-0001
• 80006-433370
• S/N 536