No comment
 

http://www.theregister.co.uk/2011/02...radio_signals/

tom
K0TAR

No comment
 

On Feb 17, 4:26*am, tom wrote:
http://www.theregister.co.uk/2011/02...radio_signals/

tom
K0TAR

perfectly logical and will probably result in a great patent... the
success in implementing it outside a well controlled lab environment
may be a problem though.

No comment three antennas - duplex
 

K1TTT has nailed it! Effecting a null that is deep enough to produce
something useful is difficult. In any case, the patent examiners will find
that the telephone people did something like this a long time ago. 73, Mac
N8TT

"K1TTT" wrote in message
...

On Feb 17, 4:26 am, tom wrote:
http://www.theregister.co.uk/2011/02...radio_signals/

tom
K0TAR

perfectly logical and will probably result in a great patent... the
success in implementing it outside a well controlled lab environment
may be a problem though.


J. C. Mc Laughlin
Michigan U.S.A.
Home:

No comment three antennas - duplex
 

On 2/17/2011 6:22 PM, J. C. Mc Laughlin wrote:
K1TTT has nailed it! Effecting a null that is deep enough to produce
something useful is difficult. In any case, the patent examiners will
find that the telephone people did something like this a long time ago.
73, Mac N8TT

J. C. Mc Laughlin
Michigan U.S.A.
Home:

One big difference is that the hybrid in a POTS phone doesn't want a
deep null. They want enough left of what is called "side tone" to give
feedback to the ear with receiver on it. If you don't they are
uncomfortable and also think the call has been dropped. It would be in
the -10 to -30dB range I'd guess.

On the other hand the null for this antenna array would need to be maybe
90dB or better to be really useful. Maybe with processing it could be
done with less, but I'd have to say, I don't know.

tom
K0TAR

No comment three antennas - duplex
 

On Thu, 17 Feb 2011 19:39:19 -0600, tom wrote:

On the other hand the null for this antenna array would need to be maybe
90dB or better to be really useful.

Here we have three (3) antennas, and as we all know they are not in
isolation.

Somewhere, there's a nearby (or near enough) overlooked reflective
surface that disrupts that oh-so-absolutely-necessary symmetry.

73's
Richard Clark, KB7QHC

No comment three antennas - duplex
 

On Feb 17, 7:01*pm, Richard Clark wrote:
On Thu, 17 Feb 2011 19:39:19 -0600, tom wrote:
On the other hand the null for this antenna array would need to be maybe
90dB or better to be really useful.

Here we have three (3) antennas, and as we all know they are not in
isolation.

Somewhere, there's a nearby (or near enough) overlooked reflective
surface that disrupts that oh-so-absolutely-necessary symmetry.

73's
Richard Clark, KB7QHC

About 25 years ago, I attended a conference on design methodologies
for blanking continuous (or high duty factor) signals in a military
environment. The benefit is to eliminate interference by your own
transmit signals to receivers, especially wideband EW/ECM receivers.
No discussion of twinned transmit antennas, though, but sample-and-
cancel techniques were prominent. Big problem: maintaining phase
linearity.

No comment three antennas - duplex
 

On Sat, 19 Feb 2011 23:33:03 -0800 (PST), "Sal M. Onella"
wrote:

Big problem: maintaining phase
linearity.

I was on duty aboard the USS Holland (my job, heading up the standards
lab) when one of the submariners rousted me out of my rack to make a
measurement - the last one before the captain could go out to sea.

I tumbled down the ladder (sometime in the early AM) to find a group
of techs huddled around a meg-Ohmmeter in the main passageway just aft
of Sherwood forest.

Now I add that significant detail because, as you mention about
maintaining phase linearity, every time a sailor shimmied past the
group to go forward, his movement would peg the meter in one direction
or the other. The guys were trying to measure a gigohm load in the
nuclear reactor. The disturbance of the local electric field was
enough to drive the resistance bridge wild. Any movement in its
vicinity was enough to do that. There was barely enough patience
among that group to let anything settle.

The sub couldn't move until they got at least 1 Billion Ohms, and when
I asked what the problem was (I was the pro from Dover there to rescue
their butts or the captain would keelhaul them), they said they were
several magnitudes of order off - too little resistance.

I hunkered down over the instrument, waited a couple of minutes before
the static fields settled and the instrument calmed, and I measured AT
LEAST a gigohm. "So what's the problem?"

"We need a billion ohms before we can certify the reactor is ready to
get underway!"

I looked at my measurement - easily a billion ohms, 1 gigohm (I
thought there wasn't that much resistance between us and the moon, but
I wasn't going to make that observation with the XO hunkered down
watching this, and the Old Man staring over his shoulder.).

"No, No! A BILLION OHMS!" came their plea when I pointed out the
measurement.

"What do you think a billion is?" I asked.

"We looked it up in the dictionary and its a million million."

I stood up and looked forward to crawling back into my rack. "That is
the English definition for billion. What you want is the American
definition for a billion which is a thousand million."

73's
Richard Clark, KB7QHC

No comment three antennas - duplex
 

On Feb 17, 9:39*pm, tom wrote:
On 2/17/2011 6:22 PM, J. C. Mc Laughlin wrote:

K1TTT has nailed it! Effecting a null that is deep enough to produce
something useful is difficult. In any case, the patent examiners will
find that the telephone people did something like this a long time ago.
73, Mac N8TT

J. C. Mc Laughlin
Michigan U.S.A.
Home:

One big difference is that the hybrid in a POTS phone doesn't want a
deep null. *They want enough left of what is called "side tone" to give
feedback to the ear with receiver on it. *If you don't they are
uncomfortable and also think the call has been dropped. *It would be in
the -10 to -30dB range I'd guess.

On the other hand the null for this antenna array would need to be maybe
90dB or better to be really useful. *Maybe with processing it could be
done with less, but I'd have to say, I don't know.

tom
K0TAR

Normal level on a phone is about -25db I think sidetones are about 10
or 12db below that. Take that with a little salt my comm days are long
time past.

Jimmie

No comment
 

tom wrote:

http://www.theregister.co.uk/2011/02...radio_signals/

tom
K0TAR

Been done.
Adaptive cancelers for co-site interference have been around for
decades. A friend of mine used to work for American Nucleonics Corp
(there's a company name from the 50s, eh) in the 80s, when they were
transitioning from totally analog cancelers to digitally controlled
cancelers (with the canceling still done in analog, with a second antenna)
The idea of two transmitting antennas forming an adaptively canceled
null at the receiver has certainly been mentioned in the literature.

No comment three antennas - duplex
 

Richard Clark wrote:
On Thu, 17 Feb 2011 19:39:19 -0600, tom wrote:

On the other hand the null for this antenna array would need to be maybe
90dB or better to be really useful.

Here we have three (3) antennas, and as we all know they are not in
isolation.

Somewhere, there's a nearby (or near enough) overlooked reflective
surface that disrupts that oh-so-absolutely-necessary symmetry.


All practical systems like this use some form of adaptive logic to fix
that. Usually, adaptive canceling is done in the receiver, because the
signal levels are lower, but in the 802.11 kind of world, with 100mW
linear transmitters, there's probably not much cost difference.

A different matter if you're running a kilowatt.

No comment three antennas - duplex
 

On Tue, 22 Feb 2011 09:54:53 -0800, Jim Lux
wrote:

Here we have three (3) antennas, and as we all know they are not in
isolation.

Somewhere, there's a nearby (or near enough) overlooked reflective
surface that disrupts that oh-so-absolutely-necessary symmetry.


All practical systems like this use some form of adaptive logic to fix
that. Usually, adaptive canceling is done in the receiver, because the
signal levels are lower, but in the 802.11 kind of world, with 100mW
linear transmitters, there's probably not much cost difference.

A different matter if you're running a kilowatt.

It only takes a couple of milliWatts (kiloWatts aside) to ruin your
day in competition for listening to microWatt signals. The desired
signal's transmitter antenna would have to be literally within the
near field of the active transmitter (and receiver's) antenna system.
At that point, we may as well use a land-line with hybrid bridges.

Software coming to the rescue for a hardware problem works only in
multi-million dollar projects (fly-by-wire avionics comes to mind).

73's
Richard Clark, KB7QHC

No comment three antennas - duplex
 

Richard Clark wrote:
On Tue, 22 Feb 2011 09:54:53 -0800, Jim Lux
wrote:

Here we have three (3) antennas, and as we all know they are not in
isolation.

Somewhere, there's a nearby (or near enough) overlooked reflective
surface that disrupts that oh-so-absolutely-necessary symmetry.

All practical systems like this use some form of adaptive logic to fix
that. Usually, adaptive canceling is done in the receiver, because the
signal levels are lower, but in the 802.11 kind of world, with 100mW
linear transmitters, there's probably not much cost difference.

A different matter if you're running a kilowatt.

It only takes a couple of milliWatts (kiloWatts aside) to ruin your
day in competition for listening to microWatt signals. The desired
signal's transmitter antenna would have to be literally within the
near field of the active transmitter (and receiver's) antenna system.
At that point, we may as well use a land-line with hybrid bridges.

Software coming to the rescue for a hardware problem works only in
multi-million dollar projects (fly-by-wire avionics comes to mind).


In these sorts of systems (the ones alluded to in the original news
story), all the signals are in one FPGA (in digital form) and the powers
are fairly low so all the RF stuff runs basically linear (DC to RF
efficiency isn't a huge deal on a 50mW transmitter next to a 10 Watt FPGA)

So it *is* a wireline hybrid bridge.. but done with numbers instead of
transformer windings.

The point I was getting at is that in these MIMO systems, there's
already multiple receive and transmit channels with substantial signal
processing going on. So it doesn't really matter much whether you do the
cancellation/null forming in the Tx or Rx side. If you can do some
clever canceling with Tx, and make it possible to use a cheaper Rx (or,
run full duplex without needing huge dynamic range/linearity in the Rx)
then that's probably a net good.

The technique proposed is very, very similar to one used to create
increased stereo separation ("headphone sound") from conventional stereo
speakers. You send a part of the Left channel signal to the right
speaker that just cancels the signal arriving at the right ear from the
left speaker. It's a very, very impressive effect.



73's
Richard Clark, KB7QHC

No comment three antennas - duplex
 

On Wed, 23 Feb 2011 09:29:56 -0800, Jim Lux
wrote:

In these sorts of systems (the ones alluded to in the original news
story), all the signals are in one FPGA (in digital form) and the powers
are fairly low so all the RF stuff runs basically linear (DC to RF
efficiency isn't a huge deal on a 50mW transmitter next to a 10 Watt FPGA)

This seems to be straying from what this is about: an antenna system.
You seem to imply that the 10W FPGA is a source of radiation to
confound things. How that arrived, I don't know.

The presence of uncontrolled reflecting surfaces in proximity to the
antenna system is the objection, and the introduction of unintended
out-of-phase reflection transmission signals combined with intended
receive signals present at the receiving antenna yields the classic
problem of S+N/N degradation.

So it *is* a wireline hybrid bridge.. but done with numbers instead of
transformer windings.

This does not answer the objection. Reality (conventional usage) will
bring these corrupting out-of-phase signals and the best that software
can offer is a regression of retries to obtain error corrected packets
sorted out a the cost of seriously depressed through-put rates.

This "invention" is more about being clever than useful and belongs in
a museum case next to the Babel Fish (whose utility is questionable
when you have to listen to Vogon poetry).

73's
Richard Clark, KB7QHC

No comment three antennas - duplex
 

Richard Clark wrote:
On Wed, 23 Feb 2011 09:29:56 -0800, Jim Lux
wrote:

In these sorts of systems (the ones alluded to in the original news
story), all the signals are in one FPGA (in digital form) and the powers
are fairly low so all the RF stuff runs basically linear (DC to RF
efficiency isn't a huge deal on a 50mW transmitter next to a 10 Watt FPGA)

This seems to be straying from what this is about: an antenna system.
You seem to imply that the 10W FPGA is a source of radiation to
confound things. How that arrived, I don't know.

No.. the original article was talking about low power 802.11/802.16
systems (which radiate less than a watt).. At that power level, the fact
that a suitably good linear amplifier is going to consume a fair amount
of power (20% efficiency would be doing well) is insignificant next to
the power consumed by the digital processing necessary to implement the
cancellation algorithm.



The presence of uncontrolled reflecting surfaces in proximity to the
antenna system is the objection, and the introduction of unintended
out-of-phase reflection transmission signals combined with intended
receive signals present at the receiving antenna yields the classic
problem of S+N/N degradation.

So it *is* a wireline hybrid bridge.. but done with numbers instead of
transformer windings.

This does not answer the objection. Reality (conventional usage) will
bring these corrupting out-of-phase signals and the best that software
can offer is a regression of retries to obtain error corrected packets
sorted out a the cost of seriously depressed through-put rates.

No.. I would expect that this would actually work fairly well. The idea
is to allow full duplex operation, rather than the current half duplex
used in, e.g., 802.11b/g. That would double the throughput (if traffic
on the network were symmetric).

If you want to run full duplex, you have to have some way to "see" the
received signal in the face of a much larger transmit signal. Since
you're transmitting, you've got a copy of the transmit signal, so it's
really a matter of figuring out what the transfer function is from
transmitter to (self)receiver. If the external environment were fixed,
then one could probably do it with a coupler with adjustable gain and
phase. However, as you point out, the environment isn't constant, so
you need a way to adaptively adjust. You could do it with a single
transmit and single receive antenna, but that puts a tough dynamic range
requirement on the system. Say, -20dB coupling from Tx to Rx antenna,
+30dBm on transmitter, -100dBm received signal.. you need 110dB
instantaneous dynamic range.. that would need a 18-20 bit converter,
which doesn't exist at a reasonable price in the 10-50 MHz sample rates
needed.

The idea of using a pair of transmitters to reduce the dynamic range
requirement on the receiver is clever. I would think you could get 40dB
suppression without too much trouble, which gets your instantaneous
dynamic range requirement down to 70dB, which is starting to be in range
(there are inexpensive fast 14 bit converters, for instance)




This "invention" is more about being clever than useful and belongs in
a museum case next to the Babel Fish (whose utility is questionable
when you have to listen to Vogon poetry).

73's
Richard Clark, KB7QHC

No comment three antennas - duplex
 

On Thu, 24 Feb 2011 17:06:39 -0800, Jim Lux
wrote:

No.. the original article was talking about low power 802.11/802.16
systems (which radiate less than a watt).. At that power level, the fact
that a suitably good linear amplifier is going to consume a fair amount
of power (20% efficiency would be doing well) is insignificant next to
the power consumed by the digital processing necessary to implement the
cancellation algorithm.

As I said, how that finds its way into antenna system consideration
still remains a mystery.

No.. I would expect that this would actually work fairly well. The idea
is to allow full duplex operation, rather than the current half duplex
used in, e.g., 802.11b/g. That would double the throughput (if traffic
on the network were symmetric).

Expectation is not explanation and recital of full duplex vs half
duplex is a duplication of what has been already offered.

If you want to run full duplex, you have to have some way to "see" the
received signal in the face of a much larger transmit signal. Since
you're transmitting, you've got a copy of the transmit signal, so it's
really a matter of figuring out what the transfer function is from
transmitter to (self)receiver. If the external environment were fixed,

And there is the nut of contention. Software will have to accommodate
to variation in environment and throughput suffers. This is old
stuff. The magic of computation still admits of cost galore. More
money for poor transfer doesn't add any sparkle to market
possibilities.

73's
Richard Clark, KB7QHC

No comment three antennas - duplex
 

Richard Clark wrote:
On Thu, 24 Feb 2011 17:06:39 -0800, Jim Lux
wrote:

No.. the original article was talking about low power 802.11/802.16
systems (which radiate less than a watt).. At that power level, the fact
that a suitably good linear amplifier is going to consume a fair amount
of power (20% efficiency would be doing well) is insignificant next to
the power consumed by the digital processing necessary to implement the
cancellation algorithm.

As I said, how that finds its way into antenna system consideration
still remains a mystery.


because the referenced patent is talking about a *system* not just an
antenna. So the *system* implementation is relevant..