Evaluating Programmable RF Attenuators

Posted by Blaise Yen on May 23, 2017

Programmable attenuators are a vital piece of equipment in almost every advanced RF testing environment, whether it’s a full-blown lab or a simple cube. They differ from fixed attenuators in that they’re able to produce different values of RF signal attenuation on demand, and they differ from basic variable or step attenuators because that value is generally computer-controlled, not analog. For those reasons, they can offer two distinct advantages: flexibility and programmability.

Digital programmable attenuators tend to be driven by transistor–transistor logic (TTL) inputs and, depending on their design, can produce attenuation across a wide range. To give one example, Adaura Technologies’ AD-USB2A series of two-channel programmable RF attenuators is capable of an attenuation range between 0 to 63dB over discrete 0.5dB or 1.0dB steps, and these variables are determined by means of easy-to-use software than can run on any Windows, Mac or Linux PC. The attenuator itself is connected to the PC through a single USB cable.

When you’re faced with a variety of potential programmable attenuators for your RF testing, there are a few points on the data sheet that are worth noting.

  • Attenuation: Clearly, the attenuation range (max. versus min., measured in dB) is going to be very important. Given that you’re probably selecting a digital programmable attenuator for its flexibility of operation, a fairly broad range is desirable. It’s also worth noting the attenuation accuracy, as any significant deviation will not be indicative of actual behavior.
  • Insertion loss: This translates to the loss in signal power (measured in dB) that comes from integrating the device into the testing system. The Adaura AD-USB4A series of digital programmable attenuators has a minimum insertion loss of just 2.5 dB in the 05–3GHz frequency range and 7dB in the 3–6GHz range, which typically allows for a more accurate measurement of the maximum input signal.
  • Step size: It doesn’t apply in every situation, but engineers usually prefer smaller step sizes because they allow the attenuation to be controlled with that much more accuracy. Adaura’s line of programmable attenuators gives you the choice of 5 and 1dB step sizes depending on frequency so you can select the model that best suits your RF testing scenarios.
  • Price: Should other parameters be more or less comparable, price can often be the deciding factor. But this comparison might not always be as straightforward as it appears. When one programmable attenuator features multiple channels, this can make the testing environment much more efficient and reduce the amount of individual devices required for each setup. For eexample, just three Adaura AD-USB4A four-channel attenuators could replace twelve single-channel attenuators.

There are some other factors that might not appear as dedicated figures on the spec sheet but are no less important.

  • Integration: How quickly and easily can you drop the device into your existing setup? Will it require a lot more cabling and additional specialized equipment such as a powered USB hub? Adaura Technologies’ line of digital programmable attenuators are not only compact; they can be powered and controlled with a single USB cable.
  • Software: There’s nothing worse than a well-built, capable attenuator being restricted by buggy or complex software. As part of your evaluation, you’ll want to ensure that the bundled software is easy to use, customizable and full-featured right out of the box, and that it will be fully compatible with your preferred OS. Some other questions to ask might be: How much programming and development time will it take to integrate the attenuator into your testing setup? Are there enough interface options to make custom coding easy? Can the attenuator be programmed to work reliably in an automated testing environment?

Adaura Technologies’ AD-USB2A and AD-USB4A digital programmable attenuators have won praise for all of the above, making them ideal for the entire spectrum of RF testing applications, including the development and manufacture of cellular, microwave radio, WiFi/MU-MIMO and IoT devices. They provide your testing environment with all the flexibility of a high-quality programmable attenuator, outstanding programmability, and at a price point that should appeal to small-scale startups as well as larger manufacturers looking for mass RF testing solutions.

Posted in RF Test Engineering.