Hilbert transformer

[Nigel Goodwin]

Presumably he's still wanting to do as he always has?, high quality audio transmitted over an ultrasonic link?. Even though he's been told repeatedly (by everyone here!) that it's not possible.

 

[epilot]

Presumably he's still wanting to do as he always has?, high quality audio transmitted over an ultrasonic link?. Even though he's been told repeatedly (by everyone here!) that it's not possible.

Hi Nigel,

I have made the circuit with 1496 chip and it works just fine on DSB but the problem is that DSB needs twice bandwidth than SSB so the voice is not so clear for higher Frequencies (while my ultrasonic sensors about 9kHz bandwidth) so I have to generate a SSB for the device.

I have read somewhere that filtering method can not provide the 15 or 20kHz bandwidth too
So any alternative?

 

[audioguru]

So any alternative?

1) FM.
2) High frequency radio transmit and receive.
or 3) Infrared.

 

[Hero999]

He wants to use SSB to save bandwidth.

FSK and use a good compression algorithm.

 

[epilot]

1) FM.
2) High frequency radio transmit and receive.
or 3) Infrared.

FM for an ultrasonic sensor?!

Wont you think a VSB can be used as an alternative?


By the way I am interested to see your voice scrambling system specialy the filter part.

 

[audioguru]

FM for an ultrasonic sensor?!

Wont you think a VSB can be used as an alternative?

No. Your ultrasonic transducers don't have enough bandwidth.

By the way I am interested to see your voice scrambling system specialy the filter part.

It is not on my computer but maybe I can take a photo of its schematic.
The filter was the easiest part. I used two cascaded 4th-order Butterworth switched capacitor lowpass filter ICs. National Semi had them, now Maxim have them. The unwanted sideband is completely removed. The modulator and demodulator are exactly the same circuit and use a cheap crystal from a colour TV.

 

[epilot]

An audio range phase shifter

 

[epilot]

Can some one says me what will happen if I use a Hilber for audiowith lower bandwidth (4000Hz) for instance.
Don't you think I'll have part of unwanted sideband at higher frequencies?
I mean the SSB will be converted into VSB at higher freq(more than 4000kHz for example).
Correct?

Is this correct:
If we make a Hilbert with 70 degree phase shift at the audio part(but 90 degree for the carrier)then we will have a VSB signal on the output?