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I made a new kind of lock in amplifier

Started by ChesterW April 14, 2018
I made a new kind of lock in amplifier. I used it to multiplex multiple 
on-off modulated LED sources using spread spectrum codes. I drove the 
LEDs using current sources and switched each on and off using separate 
codes. This allows the receiver to determine the contribution to signal 
intensity from each LED.

The link shows a pic of received intensity when using only two LEDs. The 
max intensity corresponds to both LEDs on, the min is for both LEDs off.

https://tinyurl.com/ycmbr55h

The spread spectrum coding comes with a lot of processing gain, so 
signals well below the noise floor can be recovered. The application I 
used this for was an optical brain scanner.

The scanner works similarly to a pulse-ox meter, where the ratio of 
absorption of two colors of LEDs shows blood oxygenation. If you take a 
grid of LED transmitters and optical receivers and lay it over your 
head, then the changing pattern of blood oxygenation gives a picture of 
which areas of the brain are working. For example you can wiggle your 
finger and see the signal change in your motor cortex.

I took the trouble to patent the basic signal processing method. If 
anyone is interested in the details, you can see it at this link:

https://tinyurl.com/y8vce8dd

The method could offer advantages in applications where multiple 
simultaneous probes are needed and is especially good when the probe 
energy phase is hard or impossible to manipulate. Also whenever it is 
necessary or convenient to use envelope demodulation at the receiver.

I’m looking to sell or license the patent. If anyone has contacts at 
companies that might be interested that they are willing to share, it 
would be much appreciated.

ChesterW

Email: type the third letter of alphabet next to this string and replace 
_att_ with the appropriate character: rwildey_att_gmail.com
Is that not just FHSS, DSSS, CDMA or the like? Or do you mean you've 
patented it in a "novel" application (medical imaging)?

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: https://www.seventransistorlabs.com/

"ChesterW" <iamsnoozin@yahoo.com> wrote in message 
news:j6tAC.11694$nk2.11465@fx31.iad...
> > I made a new kind of lock in amplifier. I used it to multiplex multiple > on-off modulated LED sources using spread spectrum codes. I drove the LEDs > using current sources and switched each on and off using separate codes. > This allows the receiver to determine the contribution to signal intensity > from each LED. > > The link shows a pic of received intensity when using only two LEDs. The > max intensity corresponds to both LEDs on, the min is for both LEDs off. > > https://tinyurl.com/ycmbr55h > > The spread spectrum coding comes with a lot of processing gain, so signals > well below the noise floor can be recovered. The application I used this > for was an optical brain scanner. > > The scanner works similarly to a pulse-ox meter, where the ratio of > absorption of two colors of LEDs shows blood oxygenation. If you take a > grid of LED transmitters and optical receivers and lay it over your head, > then the changing pattern of blood oxygenation gives a picture of which > areas of the brain are working. For example you can wiggle your finger and > see the signal change in your motor cortex. > > I took the trouble to patent the basic signal processing method. If anyone > is interested in the details, you can see it at this link: > > https://tinyurl.com/y8vce8dd > > The method could offer advantages in applications where multiple > simultaneous probes are needed and is especially good when the probe > energy phase is hard or impossible to manipulate. Also whenever it is > necessary or convenient to use envelope demodulation at the receiver. > > I&rsquo;m looking to sell or license the patent. If anyone has contacts at > companies that might be interested that they are willing to share, it > would be much appreciated. > > ChesterW > > Email: type the third letter of alphabet next to this string and replace > _att_ with the appropriate character: rwildey_att_gmail.com
On Saturday, April 14, 2018 at 4:36:41 PM UTC-4, Tim Williams wrote:
> Is that not just FHSS, DSSS, CDMA or the like? Or do you mean you've > patented it in a "novel" application (medical imaging)?
Seems like it to me. He makes a big distinction between encoding "bipolar" signals vs. "unipolar" signals. In the way he describes it, aren't all digital transmissions "unipolar", i.e. zeros and ones? I considered using something like this in photoacoustic spectroscopy some 40 years ago. But at the time I don't know the technology would have allowed it and I didn't have the background in electronics to invent the needed equipment. We were using a xenon light source which was then swept by a monochromator and chopped by a rotating disk, yes, a rotating disk. The resulting vibrations were picked up by the microphone and interfered with the signal. So the source had to be decoupled from the sample. I wanted to use a disk with many small holes with varied spacing and width so the signal could be decoupled at least from the harmonics. But we were getting good enough results by using two lab benches. If we had been able to modulate the light source at will this would have worked much better and been able to include in a single instrument. This was actually my first class in any electronics in college. I was in the chemistry department at U of Md and the professor was big on working the technology. He gave me a small 8 bit computer one of his grad students couldn't get to work. It was based on the 8008 CPU, yes, the 8008! I got it to work when I found the clock circuit which used a pair of monostables was crap, but would work with more decoupling. Rick C.
Hi Tim,

It is a new kind of DSSS, and the patent covers the general signal processing method. I only used optical medical imaging as an example. The first claim of the patent starts out:

1. A method of transmission from at least one transmitter to at least one receiver and subsequent recovery of a transmitted signal, the method comprising the steps of:

...


CDMA (code division multiple access) uses DSSS (direct sequence spread spectrum). It's probably clearer in instrumentation to call the method code division multiplexing. Lots of people have used DSSS for measurement systems. The high processing gain of the method is very attractive, and gives basically the same advantages as a lock in amplifier, but is also pretty immune to narrow band interference. Mine is different in being useful for uni-polar signals or in systems where you can't get the phase information. It's got to do with the code signal having all 1's and 0's, while normal DSSS uses 1's and -1's. The -1's are needed to get the different codes to cancel each other so that there is no inter-channel interference.

I manufactured the optical scanners using the method for a few years. It works.

ChesterW
DSSS signals use 1 and -1. The -1 represents a phase shift. 

ChesterW
On Apr 14, 2018, ChesterW wrote
(in article <j6tAC.11694$nk2.11465@fx31.iad>):

> > I made a new kind of lock in amplifier. I used it to multiplex multiple > on-off modulated LED sources using spread spectrum codes. I drove the > LEDs using current sources and switched each on and off using separate > codes. This allows the receiver to determine the contribution to signal > intensity from each LED. > > The link shows a pic of received intensity when using only two LEDs. The > max intensity corresponds to both LEDs on, the min is for both LEDs off. > > https://tinyurl.com/ycmbr55h > > The spread spectrum coding comes with a lot of processing gain, so > signals well below the noise floor can be recovered. The application I > used this for was an optical brain scanner. > > The scanner works similarly to a pulse-ox meter, where the ratio of > absorption of two colors of LEDs shows blood oxygenation. If you take a > grid of LED transmitters and optical receivers and lay it over your > head, then the changing pattern of blood oxygenation gives a picture of > which areas of the brain are working. For example you can wiggle your > finger and see the signal change in your motor cortex. > > I took the trouble to patent the basic signal processing method. If > anyone is interested in the details, you can see it at this link: > > https://tinyurl.com/y8vce8dd <US 8,693,526> > > The method could offer advantages in applications where multiple > simultaneous probes are needed and is especially good when the probe > energy phase is hard or impossible to manipulate. Also whenever it is > necessary or convenient to use envelope demodulation at the receiver. > > I&rsquo;m looking to sell or license the patent. If anyone has contacts at > companies that might be interested that they are willing to share, it > would be much appreciated.
I&rsquo;m sure it works, but I&rsquo;m also surprised that the patent was granted. People have been doing these kinds of things in radar for decades, and the approach has been extended to many unrelated fields since. For instance, for interplanetary radar:<https://books.google.com/books?id=ILdKDwAAQBAJ&pg=PA200&lpg=PA200&dq=pl anetary+radar+gold+code&source=bl&ots=VYA6REVwVZ&sig=pkhlFjAEoofSG1Wek7b_5fSix Xo&hl=en&sa=X&ved=2ahUKEwiO4YS177raAhVBnuAKHa9kDt0Q6AEwBHoECAAQSg#v=onepage&q= planetary%20radar%20gold%20code&f=false> Ref: Antennas and Radar for Environmental Scientists and Engineers, By David Hysell, Cambridge U Press, 2018. People also use linear FM chirps a lot. Both signal types depend on correlation gain using a wideband signal. For a general background, start with &ldquo;Radar Principles&rdquo; by Clayton Z Peebles. Hmm. It&rsquo;s now out of print, and getting expensive. This was a widely used textboopk. There may be pdfs available on the internet. Joe Gwinn
On Apr 14, 2018, crwildey@gmail.com wrote
(in article<3c7d5f40-f923-45bc-8b22-74b5c60a262e@googlegroups.com>):

> Hi Tim, > > It is a new kind of DSSS, and the patent covers the general signal processing > method. I only used optical medical imaging as an example. The first claim of > the patent starts out: > > 1. A method of transmission from at least one transmitter to at least one > receiver and subsequent recovery of a transmitted signal, the method > comprising the steps of: > > ... > > CDMA (code division multiple access) uses DSSS (direct sequence spread > spectrum). It's probably clearer in instrumentation to call the method code > division multiplexing. Lots of people have used DSSS for measurement systems. > The high processing gain of the method is very attractive, and gives > basically the same advantages as a lock in amplifier, but is also pretty > immune to narrow band interference. Mine is different in being useful for > uni-polar signals or in systems where you can't get the phase information. > It's got to do with the code signal having all 1's and 0's, while normal DSSS > uses 1's and -1's. The -1's are needed to get the different codes to cancel > each other so that there is no inter-channel interference.
The classic remedy is to subtract 0.5 from the unipolar signal and multiply by 2 to obtain +1 and -1. Phase, while useful, is not required. In radar, with and without phase data is called coherent and noncoherent processing respectively. Joe Gwinn
You are correct about the holes changing the frequency spectrum of the light signal. That's excellent intuition for a first year guy. The light signal would still have been harmonically related to the interference from the mechanics though, since the hole pattern repeats every revolution of the wheel, so there would have still been problems. Like you said, a non-mechanical way to flash the light would have fixed the coupling, but it's hard to flash that kind of light quickly, as I'm sure you already know.

Using my system, you could not only replace the chopper wheel, but also the monochromater. The light source can be made of multiple emitters, each emitting a different part of the light spectrum. All of the emitters can flash simultaneously, each using a different code, and then the amplitude of each could be separated mathematically from the received signal. Since the monochrometer only allows one color through at a time, this would dramatically increase the throughput of the spectrometer. In fact, the first test I did to confirm the idea was using RGB LEDs in a reflection spectrometer. I measured paint-chip samples and compared the results to a commercial color reader.

ChesterW
On Sat, 14 Apr 2018 19:17:04 -0400, Joseph Gwinn
<joegwinn@comcast.net> wrote:

>On Apr 14, 2018, ChesterW wrote >(in article <j6tAC.11694$nk2.11465@fx31.iad>): >
[snip]
>> >> I took the trouble to patent the basic signal processing method. If >> anyone is interested in the details, you can see it at this link: >> >> https://tinyurl.com/y8vce8dd <US 8,693,526> >>
[snip]
> >I&#2013266066;m sure it works, but I&#2013266066;m also surprised that the patent was granted. > >People have been doing these kinds of things in radar for decades, and the >approach has been extended to many unrelated fields since. >
[snip] I'm not surprised that a patent was issued. The USPTO has become polluted by Vietnamese bureaucratic toadies who have no clue. I've had a few recent exposures that demonstrate that they are village idiots. What _will_ determine patent validity will be some hard-ball suits when people like Chester try to enforce their "patents" and get their ass handed to them on a shingle. (I really enjoy being an expert witness in patent court ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | To those of us in my age bracket... GREEN means inexperienced and/or incompetent.
On 04/14/2018 08:13 PM, Jim Thompson wrote:
> On Sat, 14 Apr 2018 19:17:04 -0400, Joseph Gwinn > <joegwinn@comcast.net> wrote: > >> On Apr 14, 2018, ChesterW wrote >> (in article <j6tAC.11694$nk2.11465@fx31.iad>): >> > [snip] >>> >>> I took the trouble to patent the basic signal processing method. If >>> anyone is interested in the details, you can see it at this link: >>> >>> https://tinyurl.com/y8vce8dd <US 8,693,526> >>> > [snip] >> >> I&rsquo;m sure it works, but I&rsquo;m also surprised that the patent was granted. >> >> People have been doing these kinds of things in radar for decades, and the >> approach has been extended to many unrelated fields since. >> > [snip] > > I'm not surprised that a patent was issued. The USPTO has become > polluted by Vietnamese bureaucratic toadies who have no clue. I've > had a few recent exposures that demonstrate that they are village > idiots. > > What _will_ determine patent validity will be some hard-ball suits > when people like Chester try to enforce their "patents" and get their > ass handed to them on a shingle. > > (I really enjoy being an expert witness in patent court ;-) > > ...Jim Thompson >
I definitely don't know why it's possible to have a patent granted on a design for a system which intrinsically relies for its function on "prior art" that has itself not been invented yet. as an absurd example e.g "here's a new design for an interplanetary spacecraft which if a space-folding antimatter drive existed would employ it in a novel fashion." But there are definitely patents in that vein that have been granted to large multinational corporations with names like Sony, Apple, etc.