Range Reduccion caused by high-frequency modulated signal

[alcatraz1972]

I would like to try this:

I want to use 433 MHz transmitter and receiver electronics used for digital transmition upto 150 Kbps. At the transmitter circuit I would like to introduce a RF switch which could be modulated at 21 MHz (between antena and RF amplifier).

The idea is to send 12-bit at 150Kbps and afterward few pulse at 21Mhz. I know I need to modified my receiver or even design one because those receiver will filter the signal at 21 MHz.

My question is:

Is it posible to read-out the RF signal at 20 m if the original range was 100 m? or the signal will be so weak that is not posible to recover any more?

Please, could someone give any idea. I am new in this field and any feedback even if you think it is imposible to implement it

Thanks in advance

 

[flatulent]

Re: Range Reduccion caused by high-frequency modulated signa

you may have trouble finding a TR switch that can be switched this fast. The other problem is bit synchronization at the receiver.

What is the purpose of this scheme? There are probably other ways to perform your desired system function that work better.

 

[alcatraz1972]

Re: Range Reduccion caused by high-frequency modulated signa

I found some switches on the analog devices web. It seems I will lose 9.4ns between to switch on/off. However, I guess still there are 10 times faster.

The idea is to have on the same hardware a channel for digital comunnication plus an aditional signal for position tracking. I have the algorithm already working in ultrasounds technology.

The syncroniztion is not a problem. I found a posible solution.

Have you and idea how much the range could be reduced?

Best Regards

 

[flatulent]

Re: Range Reduccion caused by high-frequency modulated signa

The range will be reduced by the square root of the receiver bandwidth ratios of the two systems. I suspect that with a 43+ MHz bandwidth compared to the present 0.3 MHz bandwidth this will be about 10 times.

Another ranging method is to use a pseudorandom digital transmission. At the receiver you can get the correlation peak located to within 0.1 bit time or better.

 

[alcatraz1972]

Re: Range Reduccion caused by high-frequency modulated signa

Another ranging method is to use a pseudorandom digital transmission. At the receiver you can get the correlation peak located to within 0.1 bit time or better.

I know about the correlation peak technique. However, for this technique you need to sample a large amount of data in order to decrease the variation in the final estimation. The method I would like to try can achieve a resolution within 1/148 bit time using no more of 10 bits.

The idea is to use a slot time very short with extra data that the normal receiver circuit will filter out, so the digital data is not corrupted. However, in parallel a analog circuit will be trigger to sample this few bit.

Thanks for the range information. Now, I will study if I can amplify the RF signal only for the ranging information and still pass the RF regulation of European Union.