quadrature oscillator

[dr.power]

Hello guys,

I want to design a SSB modulator using the phasing method.
Can you guys please introduce me a good quadrature 90 degrees oscillator chip or circuit for the carrier osscilator section?

Thanks

 

[JimB]

Several ideas come to mind.

The very simple:
Just use an R-L and an R-C network. One gives a 45 degree phase lead, the other gives a 45 degree phase. Hence 90 degree shift between the two.
However this will be tricky to set up, will probably drift, and will only work over a small frequency range.

A standard approach:
Uses three D-type flip-flops to divide an oscillator which is running at four times the required frequency.
Works over a wide frequency range with an accurate 90 degree phase shift between outputs.

The super-duper fancy and expensive way:
Use two Direct Digital Synthesiser (DDS) chips driven by a common oscillator.
The control words sent to each chip from the microcontroller are the same except for the phase bits.
Set the phase bits to zero for one chip and 90 degrees for the other chip.
Result is two very stable signals phase shifted by 90 degrees.

Your choice.

JimB

 

[carbonzit]

So, for the "standard approach" you described, one would get this, no?

**broken link removed**

But how would you get two signals 90° out of phase out of that? (I have no doubt that it can be done, just couldn't figure out this particular puzzle.)

Hmm, maybe you don't need that bottom wave, since you said 4 times the frequency, but since you're using 3 FFs, I wonder what the third one is doing.

 

[simonbramble]

surely a Wien Bridge Oscillator can set up the in phase and feed this though an integrator to get the Q phase. From my days at school, when differentiating Sine -> Cos and Cos -> negative Sine. This keeps all the waveforms as sine/cos and not square

 

[JimB]

So, for the "standard approach" you described, one would get this, no? ...
... but since you're using 3 FFs, I wonder what the third one is doing.

It is doing this as per the attachment.
Scanned from:
Solid State Design for the Radio Amateur published by the ARRL

JimB

 

[dr.power]

Jim,

I am researching on the modulation & the modulators, So I please I would like to know the reference for this:
https://www.electro-tech-online.com/attachments/quadrature-generator-png.55972/

 

[JimB]

It is in the book:

Solid State Design for the Radio Amateur
Published by the ARRL

I cannot see an ISBN number anywhere on the book.
It was published in 1977 and I think that it is out of print now.

The fragment which I scanned is on page 184.

JimB

 

[dr.power]

It is in the book:

Solid State Design for the Radio Amateur
Published by the ARRL

I cannot see an ISBN number anywhere on the book.
It was published in 1977 and I think that it is out of print now.

The fragment which I scanned is on page 184.

JimB

Thanks Jim,

I was not able to find any download able version for it.
Please are you able to scan the SSB circuit and maybe the explanations for it?

Thank a bunch