How-to Install Matching Circuits in the Accel-RF Test Fixture

Watch this video for a quick guide on how to test a wide variety of device types over different test frequencies.

Installing Matching Circuits in the Accel-RF Test Fixture

Accel-RF’s lines of RF and DC test fixtures are uniquely designed to allow the operator to easily reconfigure for testing a number of different devices using the same platform. By changing out the input and output RF circuits that provide RF and DC bias to the device-under-test, an operator can test a wide variety of device types over different test frequencies.

Focusing on the Accel-RF SMART Fixture, there are some basic tools required when replacing your matching circuits:

  • Soldering iron
  • 3/32" and 0.050" Allen wrenches
  • #2 Phillips screwdriver
  • Metal tweezers
  • Digital multimeter

Unscrew and remove upper RF wall and unsolder the wires bring in DC bias

The first step is to unscrew and remove the upper RF wall. This will give you access with your soldering iron to unsolder the four wires bringing in the Bias force and sense lines.

Unscrew and remove lower RF wall

You can now unscrew the lower RF wall and set it off to the side along with the six screws you just removed.

Loosen set screw above RF connector

The last step required to remove the existing circuits is to raise the two RF connectors. These are contacting the circuits through a mechanical press-fit connection so you will just have to raise them up. Start by loosening the set screws that come down from the top of the fixture using the smallest Allen wrench. You can back it out but don’t totally remove the set screw as you just want to give the connector some range of motion to slide up.

Loosen two sidewall connectors screws and slide RF connector up

Using the appropriate Allen wrench, loosen the screws holding on the connectors from the outside of the fixture. You will now be able to slide those up and you can temporarily tighten the screws to hold the connectors in the “up” position.

Remove RF circuits and place replacement circuits in fixture

The circuits are now free to remove and set aside for storage for future testing. You can then place the new circuits into the fixture. Note that if you are changing to a different DUT package, now is also the time to change to a different DUT adapter plate.

Install and loosely screw down bottom RF wall

Start by loosing installing the lower RF wall. You only want to start the screws at this time.

Solder down DC bias wires

Now reattach the bias lines with your soldering iron.

Reinstall and loosely secure top RF wall

Install the top RF wall but leave the screws here loose for now as well. Check to make sure the metal wall isn’t making contact with the wires you just soldered down.

Slide a circuit against outer wall and center under RF connector. Tighten a couple of the screws

The boards will have some play and you can slide them flush against the outer wall under the RF connector. Also, center the RF line so it falls right underneath that RF connector. Once you have it positioned properly, you can tighten down one or two of the RF wall screws. Repeat this with the other circuit and then tighten down all RF wall screws.

Slide down RF connector and apply spring pressure with flat edge of tweezers as you tighten the screws

With the boards held in place, the next step is to lower the RF connectors. You need to apply some pressure but don’t want to overtorque these down into the circuits. Use the flat edge of your tweezers to apply spring pressure to the end launch while you tighten the two mounting screws.

Use DMM to probe resistance across RF connector

This is a good time to check to make sure the RF pin is making contact with the circuit. Measure the resistance from the outer connector center conductor to the circuit trace and make sure it is a short. If not, try reinstalling that RF connector.

Tighten down top set screw

To finish up the assembly, tighten down the top set screws.

Use DMM to probe bias lines for shorts

Use your DMM to probe the Bias Force and Sense lines for shorts. Measure the resistance from the different traces to the fixture housing metal and make sure you measure a high resistance.

Your circuits are now mounted and ready for testing. You can now load a device and try checking out the performance in either an Accel-RF benchtop platform or a reliability test system.

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