As mmWave tech matures, so do T&M units and methods

The introduction of 5G has also led to a market boom for new, specialized test and measurement equipment (T&M).

In the past, millimeter wave test systems relied on software leveling techniques that were unstable and sometimes damaged equipment. In today’s marketplace, mmWave T&M has real-time leveling techniques that provide power level control and power sweep control to protect sensitive equipment. This provides test engineers with optimal performance accuracy and stability during the test phases.

In the past we have discussed how a new era of improved T&M device designers is helping designers overcome 5G challenges. However, the discussion of burgeoning T&M devices for mmWave applications has many dimensions beyond 5G that warrant discussion – including the testing challenges of mmWave technology and the standout features of today’s new products.

Common challenges in mmWave testing

One of the challenges of testing radio frequency electronics with mmWave is that these devices often experience high propagation losses and inconsistent measurements while transmitting data. This means that, according to Anritsu, test equipment often needs higher performance or better sensitivity to take accurate measurements.

Representation of the propagation loss versus frequency. Image courtesy of Anritsu

At mmWave frequencies, using a spectrum analyzer and long cables to measure the path loss of a wireless connection can become a problem. Variable temperatures only make the problem of loss more difficult.

Clean and tighten connectors

There are a few simple ways test engineers can overcome these mmWave challenges.

Primarily, Keysight Technologies suggests sensitive male connectors or short custom connectors for the test equipment faceplate.

Engineers also need to service connector interfaces, which are approximately 1/2 mm in size and can easily collect dust particles and scratches. At mmWave frequencies, engineers may need a microscope to spot and clean up these defects that can damage the impedance matching. Strong millimeter wave connections also require a strong plug torque, so users should also be familiar with an appropriate torque wrench.

Try to avoid overuse or stress from wrenches using the techniques above. Image courtesy Keysight Technologies

Another possibility is to reduce the total number of connections in a test system and to reduce the number of faults and measurement errors directly.

Create a remote test head

Portable spectrum analyzers and external mixers can be connected directly to an antenna, allowing the user to create a remote test head and measure as close as possible to the device under test.

For millimeter tests, a direct connection to a device under test can provide more accurate measurements than a cable connection. Image courtesy of Anritsu

Note that while these devices do not have the intermediate frequency bandwidth of a signal analyzer with direct and continuous coverage, a low frequency signal analyzer can easily cover these frequencies.

mmWave test equipment: SAs, VNAs, and VSGs

In addition to standard spectrum analyzers, vector network analyzers, and more recently even vector signal generators can be used for millimeter wave tests.

Vector Network Analyzers (VNAs) are instruments that measure the network parameters of electronic devices. To select the appropriate VNA, engineers should evaluate the design specifications of their project, especially those that require precise power control, large power sweeps, and optimal noise range.

Keysight claims that a VNA is only effective and accurate when it is equipped with strong calibration capabilities. A critical VNA feature is vector error correction, a mathematical technique that looks for systematic errors while monitoring output power and receiver noise.

While vector signal generators (VSGs) are typically not equipped for mmWave testing, the first VSG with mmWave testing capabilities became available in late 2020 and early this year. With the R & S SMM100A, Rohde & Schwarz presented a new vector signal generator that is supposed to take on mmWave test functions.

According to R&S, the SMM100A VSG is a real-time signal generator that works with mmWave frequencies of 44 GHz. Image courtesy of Rohde & Schwarz

According to Rohde & Schwarz, the VSG can generate up to 44 GHz and reach almost 7 GHz in Wi-Fi 6E networks.

A growing market from mmWave T & M.

MmWave technology dates back to the early 1900s. As a result, there are numerous models of mmWave T&M devices on the market. Even the latest technology can overlook potential errors that occur during the test systems because the wavelengths are smaller than standard microwave frequencies.

Therefore, it is important for test engineers to be aware of the many techniques – such as proper calibration, connector maintenance, and portable instrumentation – to address the challenges associated with mmWave technology.

As long as T&M equipment operates at frequencies above 50 GHz, test engineers have many options to choose from.

What other tips do you have for testing mmWave technology? Share your ideas in the comments below.

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