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Implementation of Transmitter and Receiver for GPR

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  • Implementation of Transmitter and Receiver for GPR

    Hello,
    I am a final year student of BEE Telecom. I chose my Final Year Project to design a Transmitter and Receiver for GPR. GPR has already been developed in my institute. It uses VNA (Vector Network Analyzer) as its source.

    Some features of that project are:
    -> Double-Ridged Horn Antenna
    -> Synthetic Aperture Radar (SAR) with UWB source (VNA) in Mono-synthetic mode
    -> Only s11 (first parameter of s-parameters) was measured by VNA
    -> 2.4 GHz center frequency with 1 GHz Bandwidth---a pulse with 1 ns duration transmitted by a Stepped-freqeuncy transmitter
    -> Tx and Rx are in VNA
    -> Only Return Loss measurements are observed
    -> Data from VNA is processed in Matlab to create a rough image of observed reflections

    I hope the data above is enough for you to get the idea. I have just started working in the project

    Since VNA is a multipurpose device and the already-implemented project used it to find S11 only, I chose this project to introduce portability in GPR. (VNA available in my institute is bulky)

    In short, my goal is to develop a Tx and Rx which function as the VNA does; thus introducing portability.

    The problem is that I have no idea where to begin. I need a head start. I need to develop complete understanding of how the Stepped-Frequency Transmitter (used in already-developed project) and compatible receiver works and I have to develop the whole system without changing other features like antenna, codes etc.

    Please guide me and point me in the right direction.

    Regards.

  • #2
    I'd say that some details matter more than the others, e.g. bandwidth is more relevant than the center frequency.
    Try to become friendly with some really broadband antennas of moderate gain, such as log periodic antenna, which is less bulky than the more common MW antennas. The most important point with low gain is that such antennas are more close to the point source than the high gain antennas, and they achieve far field conditions closer to the antenna than the high gain ones. You may as well consider double the aperture as the absolute minimum distance for sensible radiation pattern to start forming. Placing antenna's near field into ground makes no sense at all, so the obvious solution is low gain antenna, say 10 dBi.
    Good luck

    Comment


    • #3
      As far as I know there are no open source GPR projects. So good luck and keep
      us posted. Attached are some files I collected, that may be helpful?

      Comment


      • #4
        problem uploading
        Attached Files

        Comment


        • #5
          Does any one know how to compress a pdf file? Trying to upload a 2.4mb which exceeds 1mb limit

          Comment


          • #6
            You may try "printing" it in a pdf file with lower dpi.

            Comment


            • #7
              Thank Your Davor and Altra for replying.

              @ Devor

              Sir, my job is to 'replace VNA' i.e., get it out of the equation of the previous project. I don't have to make an antenna, I'll use the already available one.

              @ Altra

              I'll make sure to completely open source my design. Can I get a block diagram of it? It will be helpful

              and I never compressed a pdf.

              Comment


              • #8
                Ali

                I googled "Stepped-Frequency Transmitter" and got a few hits related to microwave.
                One of the results is a patent which has block diagrams. Down load the pdf.


                http://www.google.com/patents/US5406842

                Comment


                • #9
                  Thank you, Altra.

                  Comment


                  • #10
                    Wow I'm glad school is over for me. This is what you are going to design and replace.

                    http://en.wikipedia.org/wiki/Network...er_(electrical)

                    All you need is a 2.4ghz vco or dds. baseband receiver, a fast adc, lots of ram and a doctors degree in dsp.

                    Comment


                    • #11
                      yeah I know, but Only a part of it...

                      I am just doing Bachelors.

                      and I just know the terms. How to design them is the challenge.

                      Comment


                      • #12
                        So you better keep the VNA and replace antenna

                        Comment


                        • #13
                          Is it actually out of my scope?

                          You must have read the post of low-cost GPR by Seeker. It seems legit to me. Can I design it?

                          By the way, I am considering all my options. I still have time to change it. What do you suggest?

                          Comment


                          • #14
                            Also, please suggest an alternative. I can change the antenna for better penetration but resolution will decay as well. Anything from you will be helpful.

                            Comment


                            • #15
                              In the references for the Wiki link above is a home brew vna. Its only for 60mhz but may give you some ideas. I assume in your case the DUT is the ground matrix. The phase and amplitude of each frequency will be combined and analyzed to output an indication of density? This is all beyond me, but really interesting.

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