On Mar 1, 11:58 am, Ian White GM3SEK wrote:




"the magic box in the center of the array" is more the former model,
and while simple conceptually, in the long run probably isn't the best
way to solve the problem in a system context.

That is very true. Unfortunately, the ham market is divided up into
physically separate compartments of transceivers, power amplifiers and
antennas. That is a severe restriction which makes all the technical
challenges much more difficult.

Dare I say that what is needed is that much overworked phrase
"paradigm shift"? It used to be that a "transceiver" was a radical
new thing, because everyone knew that you needed a separate Tx and
Rx. Oddly, with phased arrays, perhaps the transceiver becomes passe.

However, we can try to pare the problem down a little.

Another important point is that the concept of 'market demand' is
beginning to break down in ham radio. The big manufacturers are
increasingly challenged by new products that pay no attention to the
market - they spring directly from some individual or small team
deciding they're going to do it.

I think this has actually been the case for decades. I doubt, for
instance, that the KWM-1 was motivated by some massive pentup demand
for an integrated SSB transceiver.

Then maybe the design is produced as a kit, or manufacturing is taken up
by some lower-tier company that is faster on its feet. Seems good to
me...

This would be true of many things.. the SDR1000 might be an example. A
variety of TAPR kits might be another.



For instance, a multi
channel receiver, which can do all the phasing, very precisely, at low
levels, either with analog or digital processing, can give you the
nice deep nulls and adaptation.For TX, though, null depth isn't as
important as maximizing the power squirted in the right direction.

That seems a good place to cut the problem down to size. By all means
continue to use the existing phasing networks for TX, with 4 or 8
switchable directions and fixed phasing; but switch the antennas over to
a totally separate network for RX.

In fact, for HF, you can probably get away with smaller active
antennas for receive. There's no particular reason why the Tx
antennas and the Rx antennas have to be the same, since you're not
typically receiver noise figure limited. There IS a strong signal IM
problem..so maybe active receive antennas aren't the right solution.
But, there's a lot of convenience possible if your receive antennas
are all something like 6 foot whips.

At the lower power levels, the RX network could be much more complex and
versatile, combining the signals from the four (say) antennas with
amplitudes and phasing that could be varied on the fly.

You can use nifty things like the 4 quadrant vector multipliers from
Maxim, for instance.


Another way to scale down the problem is not to be too ambitious about
automatic null steering. In ham operating it is often difficult for a
computer to identify which is the wanted signal and which is the QRM, so
maybe let's not try. Semi-automatic null steering definitely would be
within reach, where the user has a control to steer the null direction
manually for the best audible results, and the computer does the math to
select the required network parameters.

That would be where I would start. Adaptive nulling is a bit weird to
work with as a user, especially if you expect to control it. And, for
hams, they want a bit more control. What would be cool is to have a
3D panoramic display that somehow indicates not only the frequency
spectrum, but the angle of arrival.
So.. not today, but I'd figure that in 10 years, you'll start to see
real broadband phased arrays (not just 4-8 switched beams in a single
band like a 4 square).

Yes, I think maybe so. We already have most of the technology for an
advanced manually steerable RX array, so it's mainly a matter of
integrating the separate parts of it to make a practical design. Someone
just has to decide to do it... and maybe they already have.

I've got most of both halves (steerable Tx array and steerable Rx
array) in pieces, but there's a lot of practical usability and
integration issues. Sure would be nice to have a wealthy patron and
have lots of free time and a big budget to work on itgrin. I
developed the in-situ calibration algorithms as part of a R&D effort
at JPL, but the resources eventually ran out. Too many projects and
too little time.

Jim, W6RMK