alternate active all-pass

It works fine, and IMHO, it is better to not feed spikes into the circuit.

Aren't those the 'standard' all passes.

I've used both. (but only ~audio freq.)

Sure, B is the circuit I've always used for that. When I was a grad student I built a 13-bit successive-approximation phase digitizer using a SAR IC (AM2504), a 12-bit DAC, an all-pass phase shifter, a homemade low-offset microvolt comparator, and a couple of flipflops to decide which null to shoot for. Its input frequency was 60 MHz, and it ran at

The phase shifter was two of Circuit B in series, with MV209 varactors with inductors in series and parallel. That linearized it pretty well, at least enough so that a software linearization didn't lose precision.

Having one end of the varactor near ground makes it a lot easier to control.

Cheers

Phil Hobbs

Off topic but...Analog Devices needs a bigger sign over at their Norwood offices. they have like a five acre front lawn and a teeny lil sign about four feet wide can't even read it from the road without 20/20 vision. What's that say...anal...what??

Yeah I realize New England tends to be understated but they could make it a little huger.

Maybe they're worried passers-by will figure it's some kind of sex toy company and complain.

We just had a meeting and decided that we'll dump the big all-pass, which has been a hassle, with oscillations and distortion. We'll use a dumb 90 degree phase shifter that works at one frequency. Our only customer for the I/Q modulator so far works at fixed frequency, around

That will be kinda like this:

We're driving an ADI analog multiplier that has diff inputs, so that works nicely.

This is easier to explain to the customer. One path is 0 degrees and one is 90.

has anyone thought about using an active impedance converter in standard form #2 instead of the capacitor to ground? such as a negative inductor. I think it would still be all-pass transfer function but offer performance advantages in some use-cases. I'm doing the math on it...

We decided to trash PCB rev A, and go for dumb and low risk on B. I don't want a rev C.

There are lots of ways to get 90 degrees at one frequency.

I ran into a situation recently where I was into the process of designing a Revision C of something when the client rang me up and told me that they'd determined Revision B was quite satisfactory enough and insisted on paying me my fee immediately.

The perfectionist-man part of me wanted to continue however the business/family man part of me successfully overruled and I ceased labor immediately and had a relaxing weekend with the girl friend instead.

Well it feels good to do math sometimes so I'll see what this idea looks like out of curiosity. also she's away so I can get away with it. Heh she probably worries I'm gonna go out on the town lol

If you work on it and get her used to the idea that you need a little time for an outside affair, not to worry about it, you'll have plenty of free time for the lab.

I was going to make a rebuttal but I think I see your point

If I need some alone time I can always announce loudly as I walk into the living room "Sweetie, I want to tell you all about the classic, wonderful 807 beam power tetrode"

That works pretty good

Hey, so how about a few sections of RC phase sequence filter? It's got a weird impedance vs. frequency. I've only used it around audio (3 Hz to 3 kHz :^) but I thought I saw things in the RF range. At RF they call it by a different name. (which I can't remember.)

George H.

I'd have to define the phase of a spike!

We have one customer that, if we make a mistake, tries to pay us to fix it!

They must be used to working with lawyers

I've said some unkind things about John Larkin, but I've never accused him of being a lawyer.

Not so much. They really value long-term relationships and think that they should support "small companies" that do good work for them.

I think that we should admit and pay for our own mistakes. EMI sensitivity is a borderline "mistake" but I thought that we should pay to improve our own product.

Reminds me of an old joke.

Three friends, a doctor, a lawyer, and a physicist, were out having a few drinks. The topic came up: would you rather have a wife or a mistress?

The doctor said, "A wife for me, all the way. I get called out at all hours, even during holidays. A mistress would never put up with that."

The lawyer said, "Are you nuts? A wife can take you for all you've got. A mistress for me any day."

The physicist said, "I'd like both."

The others replied, "Both? Why?"

The physicist replied, "Well, with both, if I tell the mistress that I'm with the wife, and I tell the wife that I'm with the mistress, I can spend my time at the lab!"

Boom-tsssh. ;)

Cheers

Phil Hobbs