Web page in progress - perhaps I should introduce these sub web pages
Let me start with radar - this is a time domain measurement that uses a short pulse of energy and measures distance relative to this time delay based on the speed of propagation assumed in a medium.
Radar methods are suitable for audio, as well as RF into the high microwaves. The short pulse needed for time delay resolution requires high processing bandwidth and therefore high integrated receiver noise power. This may require high transmitter power to overcome this or the need for short operational range.
An alternative approach is to look at envelope phase. This is the phase shift caused to the magnitude of an Amplitude Modulated (AM) signal by propagation time delay. This has advantages
|The receiver is inherently narrow band for example 1 Hz compared to 1 GHz|
|Little transmit power is needed as narrow bandwidth receivers have improved sensitivity|
|Simple scalar receivers can be used (e.g. TRF like a "crystal set") as sensitivity offsets are met by reduced bandwidth|
The disadvantage is that only one reflected signal is resolvable (I think I can solve this though). Time domain radar, in contrast can resolve many signals reflected from objects and put these on a display. Envelope phase techniques require a singlr source (or reflector) such as in distance measurement so if you can set an experiment up to suit this physical configuration then envelope phase may be for you
I'll fill this in more detail soon, please visit the links below to see scanned documents
Well, early days TBD
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