RF testing is difficult. The process involves multiple variables. So mistakes can easily creep in, leading to inaccurate results. As a manufacturer, you cannot afford imprecise RF device testing. Aside from the monetary costs involved, wrong results can invite all sorts of legal troubles for you. Luckily, you can increase the probability of accurate testing with a little vigilance. Here we suggest five questions to ask your testing firm before they proceed with device testing.
Are Your Measurements Reproducible?
Let’s assume that an RF testing lab declares your device standards compliant. But a few weeks or months down the line, a national laboratory discovers that your product does not meet all the standards. What do you do?
You will be asked to show the laboratory test measurements, and if the national laboratory cannot reproduce the results, your RF testing lab found, you can be in trouble. Depending on the product, you may have to pay a fine, or face worse scenarios.
Such a situation can be avoided if your RF testing lab:
- Constraint’s external variables appropriately
- Use updated, Accurate tools for measurements
- Tests each measurement on the time variable
- Measure your connectors and torque correctly.
- Properly anticipates signal noise
How Many Absolute Measurements You Are Making?
In some cases, relative RF measurements are more useful than absolute ones. The latter is more time-consuming. However, with the former, you can avoid characterizing your test set-up. Here is how to ask your RF testing lab to come with relative measurements:
- Connect the device to the measurement system without an amplifier
- Record the system response frequency. Let’s call it, A
- Insert the amplifier, and measure the response frequency again. Let’s call it, B
- Subtract A from B, and you will have relative measurement
NOTE: Keeping the number of adaptors unchanged during both measurements can prevent insertion loss.
Have Your Characterized Pathloss Accurately?
Although RF device testing is possible only through relative measurements, in some cases, you cannot overlook absolute values. If that is the case, you have to be aware of the loss of radio frequency between the signal and the measuring instrument because subsequently the errors will be multiplied. The places to check for path loss are relays, attenuators, adapters, and cables.
Here are three suggestions to share with your RF testing lab:
- Establish an accurate reference if you are using a power meter or a vector signal analyzer. The reference will give you a base on which you can make subsequent calculations.
- Keep things simple. Prefer stimulus path loss measurements over calibrating measurements. The former process takes half as long and has 50 percent fewer chances of error.
- Avoid inserting or removing adaptors during measurements.
What Are You Doing to Counter Crosstalk?
Even faint crosstalk can ruin your readings if you are dealing with a sensitive measurement, such as phase noise. That makes isolation important. Here are some ways your RF testing lab can minimize the impact of noise:
- Use quality RF cables
- Shield the RF cables and note down their effectiveness on a datasheet
- Consider double-shielded cables
- Prefer semi-rigid coaxial cables if you aren’t looking for much flexibility
- Choose an appropriate RF relay
- Don’t overlook the lifetime of your RF switch
- Remember that each RF adapter leaks a little signal
- Keep the connectors through the RF compliance testing system identical.
How Are You Countering Reflection Impediments?
High reflectivity leads to inaccurate measurements, and a frequent cause of their mismatch is primary impedance from adapters, connectors, and other system components. Your RF testing lab can minimize impedance if they:
- Use RF components between 50 ohms and 70 ohms
- Invest in quality components
RF testing is complex and involves many variables. A lot of factors can lead to inaccurate measurements.
Stay in contact with your RF testing lab to ensure they are doing their work correctly.