Copper Mountain White Paper: External Triggering the VNA

Press Release Archives:

2026 | 2025 | 2024 | 2023
| 2022 | 2021

Content is copyright of company represented. Page format, custom text and images are RF Cafe copyright - do not distribute. Note: Posting of press releases costs $100 each for non-advertisers.

Indianapolis, Indiana, May 5, 2025 - Copper Mountain Technologies' (CMT) Brian Walker, Sr. RF Engineer, SME, has published a new white paper titled "Hardware Triggering a Vector Network Analyzer." In it, he details the use of hardware triggering in VNAs to synchronize measurements with external test equipment, such as programmable power supplies or pulsed RF signals. It explains how external triggering - either "On Sweep" or "On Point" - enables precise control over VNA operations, reducing power dissipation in devices like RF power amplifiers. The paper outlines SCPI commands for automation, including triggering, polling data, and checking VNA status, with examples in Python-like syntax. It also covers trigger voltage levels, polarity settings, and timing modes, including programmable delays for pulsed RF measurements. The document highlights Copper Mountain Technologies' VNAs, which support these features alongside advanced analytical functions like time-domain processing.

CMT has a growing list of Technical Resources (white papers and videos) to assist you in getting the most out of your test equipment, including exploiting some features you might not be aware of.

Hardware Triggering a Vector Network Analyzer

Brian Walker, Sr. RF Engineer, SME

Figure 1 - Trigger on Point with Delay.

CMT Cobalt Series Vector Network Analyzer Direct Receiver Access Power Amplifier Measurements.

Introduction

External triggering, or hardware triggering is a useful feature for a Vector Network Analyzer (VNA). It allows synchronization of the VNA to other test equipment in a test system. For instance, an RF power amplifier might need to be measured with various bias voltages and drain currents. A programmable power supply might step through a voltage range, triggering a VNA sweep at each step. An RF power amplifier (PA) can be tested with pulsed RF instead of a continuous signal, with the VNA triggered at each pulse to perform a measurement. This greatly reduces the average power dissipation of the PA so that it can be measured without active cooling measures.

SCPI Commands for Automating VNA

If a Vector Network Analyzer is externally triggered, an automation script will likely also be used to capture the data. With the socket server enabled, the VNA will listen on the default port 5025 for SCPI commands, which are sent as readable ASCII characters and defined in the instrument's operating manual. The manual describes SCPI commands for setting all measurement parameters and retrieving measured data. Many scripting platforms can be used: Python, C++, C#, Matlab, and LabView among others.

External Triggering Using SCPI Commands

External triggering can be "On Sweep" or "On Point." In On Sweep mode, the Vector Network Analyzer performs one entire sweep from start to stop frequencies, then returns to the start frequency and holds, waiting for the next trigger. Completed sweep data can be polled from the VNA using SCPI commands. Those commands are as follows:

query("TRIG:WAIT MEAS;*OPC?") * Wait for measurement to start query("TRIG:WAIT WAIT;*OPC?") * Wait for it to complete

Alternatively, the state of the VNA, actively sweeping or paused, may be determined by inspecting the status register.

query("STAT:OPER:COND?")

A reply of 32 means paused and waiting for trigger, and 16 means the VNA is still measuring/sweeping.

Then, getting the frequency array:

query("SENS1:FREQ:DATA?")

And getting the data:

query('CALC1:TRAC1:DATA:SDAT?') * Assuming trace 1 data from channel 1

These are just the SCPI commands relevant to triggering and getting the measurement. A great deal of additional functionality is possible.

Trigger Levels

The external trigger may be +3.3V or +5V. A logic "high" is higher than +2.6V, and a logic "low" is less than +1.1V. The external trigger's polarity may be positive or negative. Triggering will occur on a positive trigger's low-to-high transition and a negative trigger's high-to-low transition, depending on the "Positive" or "Negative" trigger setting.

Trigger on Sweep vs Trigger on Point

For the "Trigger on Sweep" mode, each external trigger causes a new sweep. "Trigger on Point" causes only a single frequency point to be measured. If a sweep contains 1001 points, there must be 1001 triggers to measure each point and complete the sweep.

Other trigger settings are "Before Sampling" and "Before Setup". If "Before Setup" mode is set, the trigger will cause the VNA to move from the last frequency to the new frequency, settle in, and then make the measurement. If "Before Sampling" mode is set, the VNA will have already moved to the new frequency and settled, and the measurement will begin immediately.

A delay after the external trigger may also be programmed. In the "Before Setup" mode, the programmed delay will occur before the new frequency step begins. In the "Before Sampling" mode, the measurement will not start until this delay is complete. This is convenient for measuring the S-parameters of a pulsed RF signal. The vector network analyzer measurement can be delayed until the stimulus signal has settled after the rising edge.

Copper Mountain Technologies offers many Vector Network Analyzers. Nearly all of them may be triggered externally and come with advanced analytical features such as time domain processing, time domain gating, and frequency offset measurement. Visit the Copper Mountain Technologies website to see the full line of products.

About Copper Mountain Technologies

Copper Mountain Technologies develops innovative RF test and measurement solutions for engineers all over the world. It is based in Indianapolis with sales offices in Singapore, London, and Miami. The company pioneered metrology-grade USB VNAs in 2011 and continues to push for innovation and change in the industry, offering a broad range of USB vector network analyzers, calibration kits, and accessories for 50 Ohm and 75 Ohm impedance from 9 kHz to 110 GHz. The VNAs use software for Windows® or Linux® operating system on an external computer, PC, or tablet. CMT VNAs are used by engineers in defense, automotive, materials measurement, medical, broadcasting, telecommunications and other industries. All CMT VNAs include application and automation support, and years of our engineering expertise at your disposal.

Contact Info

Copper Mountain Technologies
631 East New York Street
Indianapolis, IN  46202 | USA

Phone: 1-317-222-5400

Web: www.coppermountaintech.com