5361B 20GHz Pulse/CW Microwave Counter

The 5361B is a 20GHz microwave frequency counter that has pulse measurement capability. That is, it can lock onto a pulsed microwave signal, establish a gate time within the pulses, and count the frequency of the pulsed signal.

The instrument has an interesting and handy feature: The Scope-View output on the front panel, which is intended to be connected to an oscilloscope. When in pulse mode, the counter will generate a signal on the Scope-View output that represents the input pulse in the positive, and the 5361B's gate window in the negative. This is demonstrated in the oscillscope photo below. In this example, the carrier frequency is 1GHz, and the pulsed modulating signal has a period of 1ms, and an “on” time of 250us. The modulating signal is seen directly as the top trace, and the Scope-View output is at the bottom. You can clearly see the correlation of the aggregate positive- and negative-going waveform with the modulating pulses, and the small negative-going portion of the pulse is the window in which the 5361B is sampling the input signal and measuring its frequency. Refer to the diagram next to the front panel Scope-View output connector. The accurately-measured 1GHz carrier frequency is also pictured below.