There is also one external analog output port on the MS4640A-Series VNA and it is primarily used for sweep synchronization and certain triggering tasks of external instruments or DUTs. The control menu is located under MAIN MENU | SYSTEM | REAR PANEL OUT. and is shown in Figure: REAR PANEL OUT. (REAR PANEL OUTPUT) Menu.

 

The top button is a toggle on/off while the next three buttons select the output mode. Horizontal is a sawtooth wave synchronized with the sweep (resetting to the start voltage at the first point of the sweep). This output really is a sequence of steps (see Figure: Horizontal Output Waveform) whose width is determined by the per point measurement time.

The horizontal output mode waveform for the settings of Figure: EDIT REAR PANEL OUTPUT MODE Dialog Box is shown below. The waveform is actually composed of small steps whose width represents the per-point sweep time.

 

Driven port produces a static voltage level that is different when port 1 is driving versus when port 2 is driving. The TTL output is a either a static logic value or a pulse (high-going or low-going) at the start of a sweep in a given direction. The details of the output are controlled in a dialog launched by the Edit Output Mode button (see Figure: EDIT REAR PANEL OUTPUT MODE Dialog Box).

For the first two modes, the allowed voltage range is +/- 10V with an accuracy of about 20 mV + 2%. For TTL output, the selections are high, low, high pulse, and low pulse. The pulse will occur at the start of the sweep for the given driving port and the pulse width is adjustable. Although 0 pulse width may be entered, the actual minimum pulse width is about 0.5 μs. The maximum pulse width can exceed 10 s but note that if the pulse width becomes large relative to the time to complete the sweep, the instrument will wait for the pulse cycle to complete to avoid pulse collisions on subsequent sweeps.