audio phase shift
- Thread starter malti
- Start date
You say audio, but is it a single frequency, or a wide frequency band? 90 degrees correspond to very different delays in time depending on the frequency.
If it is a single frequency (sine wave) that does not change, that can be done with a few discrete components and an opamp. The Picaxe will not be fast enough.
If it is a broadband signal and you want to shift each frequency component by 90 degress, you probably need to do an FFT, then add 90 degrees to each frequency bin's phase, and then do an inverse FFT. No chance whatsoever to do this with a Picaxe or even a PIC16F series chip. At least a dsPIC required.
What is your application? That will help narrowing down suitable choices.
Wolfgang
If it is a single frequency (sine wave) that does not change, that can be done with a few discrete components and an opamp. The Picaxe will not be fast enough.
If it is a broadband signal and you want to shift each frequency component by 90 degress, you probably need to do an FFT, then add 90 degrees to each frequency bin's phase, and then do an inverse FFT. No chance whatsoever to do this with a Picaxe or even a PIC16F series chip. At least a dsPIC required.
What is your application? That will help narrowing down suitable choices.
Wolfgang
fernando_g
Senior Member
I once did something similar project using Bucket-Brigade chips (MN3007) from Panasonic. These are charge-sampled devices, and fairly useful though a little noisy.
Unfortunately these have been discontinued.
A Picaxe isn't fast enough for DSP work. You could use a dsPIC, but they're rather power hungry, and writing good audio phase shift DSP software would be a task having a steep learning curve. You might check back issues of QEX magazine, though, to see if there's a solution that is inexpensive in both hardware and power consumption, and has pre-written software.
Alternatively, if you can keep a PC near your rig, you could use something like SDRadio.
Would a passive polyphase network, such as this one, work in your application?
73,
Tom
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Jeremy Leach
Senior Member
I still don't understand what you really need to do - probably because I've got no experience of radio projects ! Could you possibly explain a little more?
For instance, as has been said, to phase shift a range of frequencies by 90degrees will need FFT etc and is a complete extreme to just adding a fixed delay (with bucket-brigade etc).
The answers going to be 'no' for picaxes anyway, but it's still interesting !
It seems impossible with PIC's.
There are various ways to create a single sideband RF signal. One of them is to mix an RF 90 deg shifted carrier, with an audio frequency, similarly 90 deg phase shifted- mix them in a balanced modulator and you have a suppressed carrier SSB modulation. I wish I can do the whole process with picaxe, but it seems impossible.
Thanks all guys
There are various ways to create a single sideband RF signal. One of them is to mix an RF 90 deg shifted carrier, with an audio frequency, similarly 90 deg phase shifted- mix them in a balanced modulator and you have a suppressed carrier SSB modulation. I wish I can do the whole process with picaxe, but it seems impossible.
Thanks all guys
He needs an accurate 90 degree phase shift across the entire speech frequency spectrum. Doing this simply and thereby generating a Single SideBand (SSB) signal has been the holy grail of ham radio enthusiasts for more than 40 years to my personal knowledge.
premelec
Senior Member
I think this is possible with high speed DSP - look at the signal and 'instantly' shift it 90 deg - however I don't know if that's being done - considering the networks that have been designed it seems overly complicated and beyond the realm of PICAXE's for sure... Time to find another fun use for the 18X!