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.