Re: How to get more bandwidth?

On 30 Aug 2006 03:05:54 -0700, "Adam" <razdani2@xxxxxxxxx> wrote:


Don Foreman ????? ???:
On Wed, 30 Aug 2006 09:21:08 +1000, "Phil Allison"
<philallison@xxxxxxxxxx> wrote:


"John Woodgate"

It isn't in fact so very difficult to make a 90 degree phase shifter with
20 kHz bandwidth, but the OP has pre-emptively ruled that out.


** So easy in fact, even I managed to design one.

See ABSE for "20kHz Outphaser Schem ".

( Shame Adam the Google Groper will not be able)


U1 and U2 = TL074

Rs and Cs = 1% tolerance ( excepting C1)

Phase offset ( R68 -R69) = 90 degrees +/- 2 degrees, 18 Hz to 21 kHz.




...... Phil

What is ABSE, please? I would like a look at this schematic if
that's possible.

"Don Foreman ""

could you find the circuit?

I did, thanks.

The widest band Hilbert I have seen( using Op amps as a Hilber filter)
is 5kHz, so I am too eager to see the new circuit Phil is talking about

It's straightforward. This approach was first documented in a paper
many years ago. It was by a guy at Sanders but I can't recall his
name just now. I built one back when the 741 was the best opamp
available. I think it was within 5 degrees over a decade or so, which
was all I needed. I was discriminating between USB and LSB in a
Doppler radar intrusion detector to discriminate between approaching
targets and receding targets. Got a patent on that, but it was prior
to 1976 so it no longer appears in a USPTO search unless one knows
the number -- which of course I've long since forgotten. I could
probably find it if anyone is interested.

Historic note: the first Heathkit (tube type) FM stereo tuner (early
'60s) used a phasing approach. It wasn't very good. The
contemporary Dynakit was much better.




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