Application Note

PulseView

™

Calibrations

Introduction

The PulseView mode in the MS464XB VNAs allows point-in-pulse, pulse profiling and pulse-to-pulse measurements and

often these are performed in some calibrated sense beyond simple normalization. While these are still S-parameter

measurements and all of the usual algorithms (SOLT, SOLR, SSLT, TRL, LRL, LRM…) and types (full 2-port, 1 path-2 port,

full 1 port, frequency response…) still apply, there can be some setup and configuration differences to be aware of.

The purpose of this note is to discuss these setup and configuration questions in the context of some common pulse

measurement scenarios.

MS4640B Series Vector Network Analyzer

Basic configurations

The calibration implications are heavily dependent on the basic measurements configuration. Is pulsed RF stimulus

being used? If not (e.g., the pulsing is only of the DUT bias or some control signal), then by definition, the calibration

will be performed in a non-pulsed state. When performing pulse measurement calibrations, one must be in the

PulseView application as calibrations cannot be shared between regular Transmission/Reflection and PulseView

since different IF systems are used. While using the PulseView application, the desired mode (Point-In-Pulse (PIP),

Pulse Profiling (PP) or Pulse-to-Pulse (P2P)) must be selected. The latter is an important point since the x-axes are

not the same (frequency vs. time vs. time/number of pulses). Since this calibration is non-pulsed, the Point-In-Pulse

situation is conceptually simple…a frequency sweep (or power sweep) is performed and appropriate error coefficients

generated. Changing the measurement width or position (or IFBW) after calibration will only affect relative levels of

trace noise and dynamic range of the results. The frequency range and point count are constrained as in regular

transmission/reflection mode; although interpolation is allowed. For Pulse Profile and Pulse-to-Pulse, the calibration

is essentially a CW process since the same frequency and power are used for the measurements across an axis of

time…the same error coefficients, within limits of trace noise, will be generated at each point and applied to the

measurement result. Again, measurement widths and positions can be changed after the calibration with only relative

changes in trace noise or dynamic range. The number of points, however, cannot be changed as this would alter

the indexing of the error coefficients.

If stimulus pulsing is needed (using Anritsu pulsed test sets or with external modulators), the situation can be slightly

more complex. The central issue is if and to what extent one wants to calibrate out dynamics associated with the

stimulus modulation process. One aspect to consider is how the reference signals (a1, a2…) are handled. The Anritsu

test sets (SM68XX) have a post-modulator reference coupler that allows pulsed references to be used (in lieu of the

unpulsed reference coupled internally to the VNA). Alternatively, a non-pulsed reference can be used by not connecting

these paths (and both methods can be emulated using external modulators). The methods for connecting the test

set in these two alternative methods are shown in Figure 1. The resulting S-parameters are different in these two

cases as suggested in Figure 2 for a PP example. This is an uncalibrated measurement just to show the behaviors

of the ratio and, since the paths of the reference are different in the two cases, the absolute S21 value changes

slightly. The central point is again the transition behavior.

Figure 1. Setups using the SM68XX pulsed test set with (picture on left) and without (picture on right) pulsed references are shown here

(cable changes circled). Similar cable changes occur on the rear panel for frequencies less than 2.5 GHz.