Patent Expiration - Tayloe Mixer / Quadrature Sampling Detector

[SeoulBigChris]

Not to nit-pick but AFAIK patents cannot be used to stifle experimenters in any case.  The whole point of a patent is to give the inventor an incentive to fully describe their invention to the public, thereby spurring further innovation.  In exchange they get exclusive rights in the commercial sphere, but they can't stop experimenters from using the patent, discussing it, sharing implementations of it, blogging about it, etc.  Otherwise I'd be in trouble... I'm using a patented idea right now in my field-mill project, and I fully intend to write it up afterwards, with some minor critiques.

I personally ran into this years ago, and to my shock, it is indeed true that a patent DOES grant the holder the right to stifle experiments. Technically speaking, a patent holder can block ANY usage of his patent, even in labs, school classrooms, etc.  Unlike copyright, there is no such thing as "fair use".  Practically speaking, many inventors do allow such benign usage. (Disclaimer, this is what my client's lawyers, Sony's lawyers, and a lawyer friend of mine from college told me maybe 15 years ago - they maybe lied to me or things have changed).

What brought this to my attention was a client who had an unusual idea that was going to be very difficult (expensive) to develop and build. Furthermore it seemed quite likely that somebody had already done it before.  I searched around for any existing products, and ran into a patent assigned to Sony that was exactly what we needed. I contacted the inventor and said we were interested in his technology for a client, and asked if there were any products already on the market which we could purchase.  A week later we received a really nasty letter from Sony telling us to quit doing any lab experiments with this technology or face a big lawsuit.

[Yansi]

Interesting. I have seen this SDR radio on youtube, but did not notice it has all resources available in such a nice form.

Somebody really wants me to have a go with SDR, uh?    (if I had the damn free time to spend here, I would...)

What I do not understand, is what is the reason for the FFT? Aren't there a more efficient ways to filter the baseband signal?

[ogden]

What I do not understand, is what is the reason for the FFT? Aren't there a more efficient ways to filter the baseband signal?

It depends. If you want very sharp filter that would require many FIR taps (>= 64), then FFT convolution filter is more efficient (than FIR). Obviously particular SDR is the case.

[Yansi]

Maybe a stupid question I did not found the answer for, but why can't you use a non-linear phase filter for the baseband filtering?  With a couple of biquads (IIR) you could get a very steep rolloff with a little computational complexity.

[coppice]

Maybe a stupid question I did not found the answer for, but why can't you use a non-linear phase filter for the baseband filtering?  With a couple of biquads (IIR) you could get a very steep rolloff with a little computational complexity.

Once you have scrambled the phase of the signal, what will be you next step in the signal chain?

[Yansi]

Then I have to ask obvious: There are many receiver constructions out there utilizing I and Q signal paths, but processing them in analog domain. There is none linear phase filter in the analog world, is it? How possible, that in analog world one can do with non-linear phase and in digital world, this does not work?

[rhb]

Okay, so no realtime SDR, just raw data recorder. Got it.

The STM32F4 ADCs, especially F42x are really poor (same as F40x and F20x - those are mostly the same). They are extremely noise susceptible. There is a built-in problem in those chips, that noise gets coupled in to the ADC from the digital circuitry. 

For noise free signal capture, I'd suggest using either different  MCU type (maybe try the newer ones like F446?) where the issue should be solved (should!) or just use a dedicated clean external ADC, which would be I think a correct way to go.

Unfortunately can't afford almost any test equipment, even used. I have to work with what I got, or try building things myself. Good on ya you have money well spent.

I was in the same boat over the cost of test gear for so long and was so used to it, that it was only watching my brother in-law rapidly deteriorate from Parkinson's and having another friend diagnosed with cancer after a couple of others died from it and two more died of heart attacks out of the blue that loosened my purse strings.  I was almost obsessively frugal during my working career saving for my old age.  I decided that 65 was old enough to start spending some.  Almost all my gear is 20 years old, but service data is available and most parts as well.  I managed after a *lot* of searching to get the 8560A for under $1500 with shipping.  I had bought a Siglent SSA3021X, but returned it because it was so buggy.

 But I did learn quite a lot struggling, though much nicer not to have to struggle. It also left me with a strong obsession with designing and building low cost test gear.

I've been very impressed by your projects.  Very nice work.

I found the ST documents about the ADC noise issues and their suggested mitigation strategies.  Thanks for the heads up on that.  I had no idea it was such a mess.  It makes me wonder if it's actually possible to do what I want.  By the time I stop doing anything to sample at full capacity, I may not be able to handle the processing.

I have the STM32F429 board that Alberto used and that's been my candidate for prototyping.  But for actually building the gadget I was planning to just use bare MCUs for the sampling.  So I'll make a point of looking at all the available chips and the ADC implementations to pick one that is not too bad.

I have found searching for ADCs by specification a huge pain both using Digikey and AD.

[Leo Bodnar]

Google patents https://patents.google.com/patent/US6230000B1/en now list this as properly expired
 

Application US09/173,030 events
1998-10-15  Application filed by Motorola Solutions Inc
1998-10-15  Priority to US09/173,030
2001-05-08  Application granted
2001-05-08  Publication of US6230000B1
2018-10-15  Anticipated expiration
2020-01-01  Application status is Expired - Lifetime

[German_EE]

Until Verizon killed it off Dan Tayloe was a regular contributor to the Experimental Methods of RF Design Yahoo Group. He always seemed to have something useful to say.

[unitedatoms]

Has the quadrature product/sampling detector appeared in any commercial applications aside from amateur radio products?

I don't believe anyone has integrated the device, meaning integrating the clock, bus switch, integrating capacitors, op amps, etc. into a single device.  I'd be interested in learning otherwise.

One can look at service manual of HP8275A4275A circa 1979 (Yokogawa HP) and see commercial application. Look at phase detector schematics. I am not a patent guru, so in my humble opinion, Motorola's patent is bullsh*t. And b.t.w. mechanical synchronous rectifiers existed for century at that point, so HP is not perfectly original either.

Edit: sorry typo in model name

[Leo Bodnar]

I have a Rubidium oscillator that uses a synchronous detector based on CD4016 CMOS switches driven by CD4013 divided LO.  It has been designed, made and sold in 1974.

It is as if someone patented a novel application of four diodes in the form of a bridge rectifier.

Leo

[ogden]

Why you guys are so cryptic? Any pointers to Rubidium Clock and maybe it's schematics/service.manual? Also - when searching for HP8275A (supposedly it is RF instrument?), search results are automotive brake pads for Mazda 

[unitedatoms]

Nothing cryptic, I assumed that the references to published HP schematics can be accepted by name, and not necessarily by URL.

This service manual
https://doc.xdevs.com/doc/HP_Agilent_Keysight/HP%204275A%20Service.pdf

The figure 8-55. On pdf it is approximately page 283. Part of the diagram labeled "Phase Detector".


The reason I am so aware about this particular detector is that I am trying to reproduce something like this (high end 10MHz LCR Meter) using contemporary parts.

[coppice]

I have a Rubidium oscillator that uses a synchronous detector based on CD4016 CMOS switches driven by CD4013 divided LO.  It has been designed, made and sold in 1974.

It is as if someone patented a novel application of four diodes in the form of a bridge rectifier.

Leo

Try looking back earlier in this thread to what the Tayloe patent is actually about.

[ogden]

Nothing cryptic, I assumed that the references to published HP schematics can be accepted by name

When you provide correct name then yes indeed. Seems you noticed typo & fixed 

[ogden]

I have a Rubidium oscillator that uses a synchronous detector based on CD4016 CMOS switches driven by CD4013 divided LO.  It has been designed, made and sold in 1974.

It is as if someone patented a novel application of four diodes in the form of a bridge rectifier.

Leo

Try looking back earlier in this thread to what the Tayloe patent is actually about.

Isn't it about "synchronous detector based on CMOS switches"? Please elaborate

[coppice]

I have a Rubidium oscillator that uses a synchronous detector based on CD4016 CMOS switches driven by CD4013 divided LO.  It has been designed, made and sold in 1974.

It is as if someone patented a novel application of four diodes in the form of a bridge rectifier.

Leo

Try looking back earlier in this thread to what the Tayloe patent is actually about.

Isn't it about "synchronous detector based on CMOS switches"? Please elaborate

To repeat what I said earlier in this thread:

The Tayloe patent is specifically about the use of 4 synchronously excited single pole LPFs, used to create medium term averages at the I and Q points of the carrier. For a system where the bandwidth of the baseband is a small fraction of the carrier frequency this cheap simple scheme works well.

[Leo Bodnar]

http://bama.edebris.com/manuals/efratom/frk

[Leo Bodnar]

We probably have to agree to disagree but this is such an obvious use of components in a way they were intended to be used.
I read the patent several times and still don't understand what makes it patentable.
Peace!
Leo

The Tayloe patent is specifically about the use of 4 synchronously excited single pole LPFs, used to create medium term averages at the I and Q points of the carrier. For a system where the bandwidth of the baseband is a small fraction of the carrier frequency this cheap simple scheme works well.

[chris_leyson]

In the paper "Single sideband modulation using sequence asymmetric polyphase networks"
M.J. Gingell, January 1973. I'm sure there was a diagram of a four way commutator followed by a polyphase filter or it might have been the other way around, polyphase filter followed by commutator. It's not obvious from his US patent US3559042

Of course this could be false memory and there was no commutator in the paper cited above.  Then again it could have been another paper by M.J. Gingell and D.R. Barber published either '73 or '74.
I think STC published the paper in one of their magazines so it wouldn't have been widely circulated.
Gingle and Barber have a patent for "N-Path Frequency Translation System" US3562556.

I might still have a copy of the Gingell, Barber paper somewhere. From a polyphase filter point of view you can trace this back to the early 1970's. My Google-Fu isn't working today so N-Path polyphase or asymetric sequence filters might be a better search term.

[coppice]

In the paper "Single sideband modulation using sequence asymmetric polyphase networks"
M.J. Gingell, January 1973. I'm sure there was a diagram of a four way commutator followed by a polyphase filter or it might have been the other way around, polyphase filter followed by commutator. It's not obvious from his US patent US3559042

That patent was filed in 1969, so it was 4 years before the paper you cited. He might have taken his ideas a lot further in 4 years. However, nothing in US3559042 is like the Tayloe configuration, although its not that far away. It has the 4 single pole filters, but they are sampling in a different way. Looking at those patent diagrams it seems strange that he didn't add one with the very simple and symmetric configuration Tayloe used. but then most things seems obvious once someone has pointed them out.