Transciever Troubleshooting

Discussion in 'Wireless & RF Design' started by egloss25, Jun 4, 2014.

  1. egloss25

    Thread Starter New Member

    May 28, 2014
    I am wanting to learn a bit about transceiver's and am wondering if you can help.

    I need to know what typically kills them when its in circuit?

    Do i test it in circuit or out of circuit?

    how to test them based off this datasheet? (

    What should i use to test it? (DMM, O-scope, etc...)

    My circuit board is having data issues where it does not allow itself to fully attach to the network and i am trying to see if this could be the culprit due to how much data this transceiver has flowing through it when the board is working.

    I am thinking that if i can find a way to test it, and hopefully see that it failed or burned out, that i could solve some of the issues my company has!

    Any ideas or brainstorming helps!!!!!!!
  2. dougc314


    Dec 20, 2013
    The chances are there is more to this than the chip you reference. Is this a product you bought that doesn't work, something you built, or an evaluation board, or some school project that you were given?

    The type of equipment that you will need is RF test equipment, and the most important will be a spectrum analyzer. The spectrum analyzer is the RF engineers oscilloscope. If you have no idea of what a spectrum analyzer is, and have no access to one then you are probably biting off too hard a problem.

    If this part is part of a bigger circuit in a commercial product, I would be inclined to say that a failure is in the external circuity. If it is on a evaluation board or experimenter circuit, then whats wrong is anybody's guess, and I would guess first at a over (or reverse) power supply voltage being applied at some time. - In which case it's toast.

    Testing this device with test equipment may be difficult because it is possibly under software control, and making it TX may involve it wanting to join a net, which may involve it receiving something first....etc. Assuming that you can get your hands on a spectrum analyzer and a thing called a directional coupler; assuming that you can detach the antenna and connect the directional coupler in line between the device and the antenna than you can use the spectrum analyzer to measure the TX power, and observe the spectral shape. If you know what you are doing then you should be able to tell if the TX path works correctly. If you are less experienced then if you can put a known good device in place of the broken one, and observe what a good one does and compare it to the bad one. However if you don't have control of its TX state (and data) then you can't be certain whats wrong.

    As far as in circuit/out of circuit goes, I doubt that its practical to remove the device from where it is and install it into a test circuit. If you have that capability then that's an option, but I don't think you'd be asking questions here.

    Another thing you can try involves only the use of an oscilloscope. The data sheet you reference is very thin, but assuming you can find the TX and RX signals and you know how to use a oscilloscope (or can get help), then you can observe the TX and RX paths for activity. By comparing the bad one to a good one you can can some insight into what may be happening. If you have direct control of the device and can TX at will then with both a oscilloscope and a spectrum analyzer you should be able to test the TX path fairly well.

    Lastly, if you have complete control of the device, and can connect two of them up to form a network, then you should be able to connect two together by coax (with at least 60 -80 dB RF attenuation in between them) and have a controlled way of testing the TX and RX paths. One thing I have done with a spectrum analyzer when I can't use RF connectors is to build a rudimentary probe out of a PC board SMA (or similar) connector and a chip cap (for blocking DC). With such a probe you can poke around and make reasonable relative measurements. For example you can look at the input and output of a gain stage ans see if you get gain. This is especially useful if you have notes from previous measurements made on a known good unit, or have one for comparisons. These probes aren't calibrated, and care must be taken when using them, The ground path of the probe can damage the circuit it it accidentally touches the wrong node.