Leveraging the Right Combination of Test Systems for Microwave and Millimeter-Wave Automated Testing

Part 1: Scaling Up — Or Down — Programmable RF Devices

One of the most significant benefits of building a bench made up of low cost, programmable automated test systems is their versatility — individual RF devices can be can be scaled up or scaled down for specific test scenarios. In practice, it means an engineer can customize multiple input signals in accordance with their specifications by utilizing an array of low cost attenuators, RF switches and phase shifters.

They also can — due to software programmability — be ideated and developed remotely, before any physical construction takes place. Prototyping smaller systems to scale up is a relatively straightforward process; once the base configuration is established, the larger system can be easily generated, upgraded, and adjusted accordingly.

In a recently released tech brief, we take a closer look at the specific considerations around the buildout of programmable RF systems. Read more about the advantages of systems that leverage programmable RF components in this blog post.

The Building Blocks Of Automated Test Systems

Automated test systems are the cornerstone of high-frequency testing for 5G, next-generation Wi-Fi, and satellite communications systems. The systems, in turn, rely on programmable RF devices such as digital step attenuators, phase shifters, and signal generators.

RF network simulation is necessary in the test and measurement of 5G and Wi-Fi 6/6e systems where MIMO, handover, and various wireless systems testing enable engineers to test next-generation wireless systems in a lab environment.

A Matrix Of Programmable RF Components

The following systems often leverage a matrix of programmable RF components in order to recreate the complexities of any propagation environment with conductive test equipment:

• RF network simulators
• handover test systems
• fading simulators
• MIMO test systems
• Handover Test Systems

Customized handover test systems are often designed for fast-moving platforms such as a high speed train or aircraft that moves in the range of multiple base stations during transit. In these scenarios, the test system will have to utilize particular attenuation ramps based upon the speed of the train's (or plane) onboard transceiver and the location of the device relative to the base station covering that particular area. The test system can simulate a downlink from multiple base stations via the inputs of the matrix attenuation unit where the outputs would be the ultimate signal arriving at the transceiver.

Fading Simulators

Fading simulators must effectively mimic the multipath and fading that occurs when a transmitted signal is attenuated and dispersed through the various propagation obstacles in the environment. In multipath fading, the final signals arriving at the receiver will be the original shifted in phase, at varying amplitudes, and with different delays. The doppler effect, or a shift in frequency will also occur according to the relative speed between the transmitter and receiver. The combination of all these effects can be seen in mathematical models such as Rayleigh distribution or Rician distribution where the signal amplitude varies in time.

MIMO Systems

This effect is also critical to test in MIMO systems that take advantage of multipath in spatial diversity for a more reliable link. These effects can be simulated with programmable attenuator and phase shifter matrices in order to reduce both the signal strength and shift it in phase. The test setup illustrates this in a spatial fading emulator setup where the RF signal from the base station is fed into a power divider to split the signal into multiple signals that are equal to the number of probe antennas in the anechoic chamber. These signals are phase shifted by individual phase shifters and then attenuated by programmable RF attenuators. The phase and amplitude adjusted signal is sent off the probe antennas where the device under test measures the signals from each antenna probe and outputs the data to a computer for further analysis.

Leveraging programmable phase shifters and digital attenuators is much more cost-effective over a channel simulator. MIMO test systems for Wi-Fi and cellular systems might require a pulsed test signal to be sent to a MIMO device to transmit multiple signals to a number of test antennas in order to test the integrity of the transmitted data. A similar setup can be performed to measure received data to a MIMO device under test (DUT) where the test antennas are configured to transmit uplink signals and the MIMO DUT receives the combined downlink signals.

In these test setups fading profiles, or more basic signal attenuation are often performed with RF switch matrices. A multipath emulator can be added for additional realism in order to gauge how these devices perform in various RF environments.

Final Word

Again, as we pointed out initially, the beauty of these test systems is that the basic programmable RF devices within them can be scaled up or down. In many cases, scaling up a programmable RF test system from individual programmable attenuators, phase shifters, switches, and power combiners/splitters is also manageable and often desirable in order to tailor the various aspects of a programmable RF test system.

Download the tech brief here: tech brief

Contact our expert team at Vaunix for more information.