Help me with Dopple demonstrator project

[Vicountboo]

I'm lost with Doppler

Hey

I've doing a project which i've started to build.
The title of my project is Doppler Demostrator for a physics class.
The outcome is to build a small battery powered transmitter embedded in a sponge ball. An audio receiver will receive this signal, measure its frequency and display the result on a digital display.

I've gone about doing it this way but i think i'm totally on the wrong path. Can anyone pls offer any insight or wat they might do.

Thanks

 

[flatulent]

Re: I'm lost with Doppler

Here are some pointers.

1. You do not need the AGC. Use limiters like in FM receivers.

2. At RF, frequency shift is 1ppm/mach number so you are not going to get much of a frequency shift unless you propel the sponge ball from a cannon.

3. From 2 above, you might want to operate at ultrasonic frequencies and have sound waves.

 

[metal]

Re: I'm lost with Doppler

Hi

You may take short paths by using a frequency to voltage converter and CA3162/CA3160 to make measurements.

 

[batdin]

Re: I'm lost with Doppler

I think you need a narrow-band filter at the input of the receiver to prevent all the audio noise from entering the circuit.
Besides,I don't know why you need a reference oscillator and a mixer given the fact that you use a relatively low frequency.Just measure the frequency and if you need to measure the deviation you can do this by subtraction at a digital level.

 

[Mike zhang]

I'm lost with Doppler

best whishes