distance measurement using rf

Discussion in 'Wireless & RF Design' started by neeladrinath, Apr 29, 2017.

  1. neeladrinath

    Thread Starter Member

    Apr 5, 2017
    37
    1
    I have to measure distance of an machine from 2 different locations around 1-2 km range. in previous threads I came to know that using rf waves it ca be done. General concept is the time taking between transmitting and receiving the signal.
    According to my application I have to keep two transmitters and two receivers on my machine and respective transmitters and receivers on my both locations and start the operation.
    But I am not understanding how to identify the frequencies. Because i need 4 different frequency ranges for this. so please help me.
     
  2. BR-549

    AAC Fanatic!

    Sep 22, 2013
    4,858
    1,321
    How about a GPS tracker?
     
  3. neeladrinath

    Thread Starter Member

    Apr 5, 2017
    37
    1
    How about a GPS tracker?

    I am taking about rf signals.
     
  4. BR-549

    AAC Fanatic!

    Sep 22, 2013
    4,858
    1,321
    GPS uses rf signals. Only, you don't receive them....a satellite does. All both of the locations do....is look at a map on the internet. It tracks your machine/machines from above. While you sit back and watch dots move on a map.

    Edit: This is how parents track their kids now. They hide one of these on the car. Google.....gps trackers.
     
    Last edited: Apr 29, 2017
  5. neeladrinath

    Thread Starter Member

    Apr 5, 2017
    37
    1
    Yes it does but i don't want to use that. i want to use simple transmitter and receiver modules for this. how it can be
     
  6. BR-549

    AAC Fanatic!

    Sep 22, 2013
    4,858
    1,321
    Sorry my friend.......it will not be simple nor easy.
     
  7. neeladrinath

    Thread Starter Member

    Apr 5, 2017
    37
    1
  8. BR-549

    AAC Fanatic!

    Sep 22, 2013
    4,858
    1,321
    Well alright then. Seems like you have it all worked out. You could set up both locations to use the same frequencies....just have location A take the measurement on the odd minutes and location B take the measurement on the even minutes.

    The machine only needs one unit and a 450 RX ant and a 860 TX ant.

    Of course you can change the measurement period.
     
  9. BR-549

    AAC Fanatic!

    Sep 22, 2013
    4,858
    1,321
    And of course don't forget to fudge in switching time. And be aware of reflections/echos/multi-phasing.

    Edit: and all you need on the machine is an echo box....You don't need the counters and such....just TX 860 when it RX 450. Or whatever your frequencies are. Measure the switching time.
     
    Last edited: Apr 29, 2017
  10. neeladrinath

    Thread Starter Member

    Apr 5, 2017
    37
    1
    In this link it uses 2 different frequencies for single distance measurement(434 MHz and 868 MHz ).Now my doubt is that for measuring two distances i have to use four different frequencies or any other way is there. If 4 frequencies are required then give me some values.
     
  11. BR-549

    AAC Fanatic!

    Sep 22, 2013
    4,858
    1,321
    By scheduling polling times(for locations) and receiver active times(on multiple machines).......One can use those two frequencies for multiple locations and multiple machines.

    Do you get what I'm saying?
     
  12. neeladrinath

    Thread Starter Member

    Apr 5, 2017
    37
    1
    I am not getting.
     
  13. BR-549

    AAC Fanatic!

    Sep 22, 2013
    4,858
    1,321
    ok........at time zero.....location A (TXA) sends out a short 450 carrier and starts a counter. Machine one RXs the 450 carrier and after a short switching time.....transmits a 860 carrier.

    TXA receives the 860 carrier and stops the counter. The count on the counter is proportional to the distance of machine one.

    I have no idea of how often you want to know the distance. But an hour has 60 min. So out of every hour....TXA can only transmit on the odd minutes. TXB, location B, is not allowed to transmit on the odd minutes.......it can only transmit on the even minutes.
    OR.....TXA can only transmit on the first 5 minutes out of ten. OR....TXA can only transmit on the first 30 minutes out of an hour.
    TXB..... transmits on the last 5 minutes of the ten and so on.

    WE do the same for the echo box on machine.......if there is more than one machine. We only let machine A receive at certain time. Machine B receives the other times.

    Do you see now?
     
  14. neeladrinath

    Thread Starter Member

    Apr 5, 2017
    37
    1
    yes sir. I got now
     
    BR-549 likes this.
  15. BR-549

    AAC Fanatic!

    Sep 22, 2013
    4,858
    1,321
    If you compare the two separate location times/distances......you may acquire two bearings along with the distance.

    It's the MH360 problem. I hope that didn't confuse you.
     
Loading...