How to simulate multipath signals?

[Nate Duong]

First you must understand the instrumentation and the antenna array.But are the antennas connected toether, or is each antenna connected to a different receiver ?Without some idea of your system configuration I cannot help you.First you must understand the configuration of the instrumentation and the antenna array.
We still have absolutely no idea what your antenna array looks like. We are not able to read your mind or examine your equipment, so we can only give you help when you are able to communicate that information.

If you cannot identify the instrument configuration then you could use one antenna only with one receiver channel to record a time series of the down-converted signal. Then you could compute the autocorrelation of that data (with itself) to identify the repetition due to multi-path. The autocorrelation is quickly computed by using the FFT of the data, square that, then reverse the transform to get the time delays.
https://en.wikipedia.org/wiki/Autocorrelation

I uploaded wrong code, here the one with updating.

 

[Nate Duong]

Is that 6" whip antenna vertical and mounted on a groundplane ?

@ Baluncore : I can say :"yes, this is"

 

[Baluncore]

@ Baluncore : I can say :"yes, this is"

If the short whip antenna is vertical on a ground plane, then it is a vertical dipole antenna.

3. Is it vertical or horizontal polarization?
ans:horizontal polarization

How do you justify using a vertically polarised antenna to receive a horizontally polarised signal ?

 

[Nate Duong]

If the short whip antenna is vertical on a ground plane, then it is a vertical dipole antenna.
How do you justify using a vertically polarised antenna to receive a horizontally polarised signal ?

@Baluncore : yes, you are right, this is a vertical dipole antenna.

We need to know 3 things: angle (alpha), delay(delta), amplitude(a) for any station.

The equation: mul = sum( an * exp(j(k*(x*cos(alpha) + y*sin(alpha)) - w*(t-delta)) which is justifed using a vertically polarised antenna to receive a horizontally polarised signal.

Since:
1. x is a center between 2 rx antennas, ( distance of 2 Rx is 10cm => x = 0.1/2 = 0.05 )
2. y : horizontal plane
3. z : vertical direction . For simple case z = 0 .

Mention: the equation is proved by derivation.

 

[Baluncore]

How do you justify using a vertically polarised antenna to receive a horizontally polarised signal ?

The equation: mul = sum( an * exp(j(k*(x*cos(alpha) + y*sin(alpha)) - w*(t-delta)) which is justifed using a vertically polarised antenna to receive a horizontally polarised signal.

I have done my time designing, building and operating radio surveillance equipment and antennas. I have been up to my elbows in radio astronomy and communications monitoring stations.

But I must admit, the justification you present here is a new one to me.
Maybe it is time for you to go back to your professor and ask for some help understanding signal polarisation.

 

[Nate Duong]

I have done my time designing, building and operating radio surveillance equipment and antennas. I have been up to my elbows in radio astronomy and communications monitoring stations.

But I must admit, the justification you present here is a new one to me.
Maybe it is time for you to go back to your professor and ask for some help understanding signal polarisation.

@Baluncore : so may ask you what is the the justification did you use?

I believe, they somehow will have similar theoretical. So I can understand what meaning of them.

 

[Baluncore]

http://www.air-stream.org.au/technical-references/antenna-polarisation

 

[sophiecentaur]

Could a reason for (apparently) cross polar reception be that many scattering / reflecting surfaces will re radiate a cross polar component. Signals received from the 'wrong' antenna could indicate the level of multipath signals. (Novel approach??)
A great multipath detection system that I have used it to look for AM on an FM carrier. (broadcast sound FM) Depth of AM tells you the level of the interfering signal. Displaying the carrier amplitude and frequency output from the demod on X and Y plates of a CRO gives you a diagonal line with a slope proportional to the proportion of multipath signal. It's a clever method but it only works for one particular mod system. (Though it could be used on the sound carrier of an analogue TV system too.

 

[Nate Duong]

http://www.air-stream.org.au/technical-references/antenna-polarisation

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