Selecting the Right RF Attenuator for Your Environment

Posted by Blaise Yen on April 25, 2017

In RF testing, precision is everything. That’s why any engineer will emphasize how essential it is to have the right tools for the job. Using the wrong kind of equipment makes about as much sense—and promises as much accuracy—as using pliers to drive in a screw.

Although RF attenuators are slightly more complex than that, the “right tools” principle still applies. These electrical components are basically designed to do the opposite of an amplifier, a device that probably needs very little explanation. That is to say, attenuators reduce the power level, or amplitude, of an RF signal without significantly altering its waveform or causing reflection. A poor-quality attenuator or the wrong kind of attenuator will not necessarily meet that crucial second criteria, thereby causing the integrity of the RF signal to degrade. And thorough, reliable RF testing depends on signal integrity.

To select the right RF attenuator for your environment or application, let’s look at four general attenuator categories.

  • Fixed: As the name suggests, this type of passive device provides an unchanging value of attenuation (e.g., 1 dB, 10 dB, 20 dB). Depending on the design of the fixed attenuator, the output signal power, or gain, will be reduced relative to the input signal power by a set and constant amount.
  • Step: This kind of passive attenuator straddles the divide between fixed and variable. It can provide different values of attenuation over a particular range, but these values can only be selected at a pre-determined increment—for example, 0.5dB—by means of an analog controller.
  • Continuously variable: These attenuators offer slightly more fine-grained control over the testing scenario. The applied attenuation can be any value within a given range. Unlike passive fixed and step attenuators, these can be active devices that use more sophisticated solid-state components and therefore allow more complex manual or electronic voltage control mechanisms that engineers can use to impose a precise degree of signal attenuation.
  • Programmable: Sometimes called digitally controlled or digital programmable attenuators, these devices apply signal attenuation that is determined by an external voltage, which in turn is regulated by means of computer software. An important point on which they differ from their continuously variable cousins is that a single programmable device can respond to multiple input controls. Programmable attenuators sometimes feature a USB port to better interface with most computers, and they are usually paired with software.

Within those attenuator categories, you’ll need to evaluate your device based on four parameters: attenuation, accuracy, frequency and impedance. If, for example, you only want to apply a particular, unchanging amount of signal attenuation as part of your RF testing, then a fixed attenuator might be the right choice. But if your testing would benefit from automation and requires more flexibility, then a programmable attenuator will be better suited to your environment. The last two parameters—frequency and impedance—will be determined largely by the equipment or system that you are testing.

Keep in mind that, as with everything else, price tends to increase along with the complexity of the device as well as the quality of its engineering. Yet it’s important not to compromise in the search for an affordable RF testing solution and to carefully weigh all factors. A high-end digitally programmable attenuator can be hobbled by buggy or limited controller software. An inexpensive attenuator might mean sacrificing accuracy or build quality. Multiple step attenuators could end up costing more—or requiring more testing time—than a single variable attenuator.

Fortunately, there are attenuators for RF testing that meet high quality standards and provide a full range of features at an incredibly attractive price point.

The Adaura Technologies AD-USB2A and AD-USB4A series of compact digital programmable attenuators provide you with the flexibility of controlling two or four channels via a single USB port while delivering unparalleled performance, accuracy and ease of use in your RF testing environment. They’re based on the Hittite HMC642 broadband GaAs digital IC, which makes it possible for a single device to accommodate high input, low insertion loss and ultra-precise step size.

The intuitive software GUI makes for easy setup and configuration using any Windows, Mac or Linux computer, and it can be used to program a fixed insertion loss along with customizable ramp functions with almost zero learning curve. And the same goes for integration. Whether you’re conducting cellular, microwave radio, IoT or MIMO testing, the AD-USB2A and AD-USB4A can easily slot into any new or existing test environment.

In the past, choosing the right tools in RF testing environments has sometimes meant exchanging flexibility for accuracy or features for price. With Adaura Technologies’ AD-USB2A and AD-USB4A digital programmable attenuators, the selection process just got a lot easier.

Posted in Blog, RF Test Engineering.