Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Modulating 2.4GHz and 3MHz signals

  1. Oct 27, 2009 #1
    I'm looking to create a radar in the public band (2.4GHz) to detect oncoming cars from a relatively short distance (around 9 meters). I have access to a signal generator which can generate the 2.4 GHz signal, as well as another generator to create a pulse train of around 3MHz. I also have all the necessary equipment to send and receive a signal in this frequency band. The problem is that I would like to modulate the 3MHz pulse train with the 2.4GHz signal, but the box that I have will only modulate the 2.4GHz signal with another signal of up to 1MHz. Obviously, I need to go beyond this. Does anyone have any ideas about a relatively cheap way to do this? Unfortunately, I only have a budget of 300 dollars to do this, so buying a new box is out of the question. Any tips would be greatly appreciated! Thanks.
  2. jcsd
  3. Oct 28, 2009 #2
    here is a design walk-through of a 20 GHz bandwidth pulse modulator:


    Cool project though, but for a radar project there are simpler solutions. If you sweep the frequency of a transmitter, say from 2.4 to 2.5 GHz per unit time, then a returned echo will be of a different frequency. Then if you compare the received frequency to the transmitted frequency, you can deduce the distance to the object. There was link of someone actually doing this but can't find it.

    and I'm sure you have a license to play around with project once completed outside of an anechoic chamber?
    Last edited: Oct 28, 2009
  4. Oct 28, 2009 #3
    Thanks for the link! The modulator design will definitely help. And I like the sweeping frequency idea a lot. The only potential problems is that we may be dealing with approaching cars which would introduce a slight doppler shift. If you are sweeping the frequency, the returned shifted frequency might create some error. We'll keep it in mind though. Thanks again!
  5. Oct 28, 2009 #4
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Modulating 2.4GHz and 3MHz signals
  1. Modulation and signals (Replies: 7)

  2. Generating 3MHz signal (Replies: 4)