Tv Radar
Overview
Making a discone antenna
Finding correlation's with FPGA custom hardware
Finding correlation's with TvCard approach
Final image and tracking
 



Overview

Tv Radar is a passive radar system that uses the RF emissions of television transmitters.

This project is actually a side effect of the code I am writing for my robot "rackbot"

The simplest system uses a PC with a Tv tuner card along with a vertical antenna.

A vertical antenna will maximize ghosting and thus will improve detection.
A discone antenna is used due to the large wavelength difference between VHF and UHF.

The PC would scan between multiple channels and take samples. Since television is AM modulated any reflections would be in the video as ghosts. These ghosts represent the distance between the signal path and the distance that the reflection took.

The signals go from towers 1,2 and 3 directly to the X in the center, however the reflections travel to the plane and then to the antenna. The result from each signal places the plane on a ellipse. Three towers are used to work out exactly where the plane is at.



Discone Antenna

The discone is a wide bandwidth vertical polarized antenna.

The main difference between this one and the one at radio shack is that this one is designed to work down to 50Mhz without a whip antenna and it has a output impedance of 75 ohms to make it easy to connect to tv amps and tuner's.



Finding correlation's FPGA hardware approach

Once you have a video signal you need to find correlation's between the main signal and refection's.
The corelation approach works by multiplying each sample with a delayed version and the averaging.

X is which filter is beeing procesed
As you can see this approach is very processing intensive since for each output slot you need to do a multiply for each sample.
 



Finding correlation's Tv Card software approach
Using a Tv card is easier than using custom hardware, however it does have some limitations.
 
 



Making the final Image