Explain Sonar Beam-Forming

[Claus Jensen]

Does anyone here have any knowledge of how "sonar beam-forming"
operates? I have read about this recently and it sparked my
curiousity.

As I understand there are two methods, phasing shifting and time
delay. IOW using delay lines, etc. or a frequency dependent phase
shift.

I have heard two FM signals are typically used to achieve this effect,
but what type of signals and bandwidth are involved and how do they
interact to form the beam as advertised?

Claus Jensen

 

[Jon Kirwan]

This sort of tech is hard to find details on (not surprising
considering military uses) but start here:

http://en.wikipedia.org/wiki/Beamforming

Sound propagation underwater and through thermal layers is
especially interesting and _very_ military. Active (pingers)
and passive buoy systems, separate or in various combos,
often used for submarine tracking make this an especially hot
topic in some circles.

Jon

 

[Phil Allison]

"Claus Jensen"

Does anyone here have any knowledge of how "sonar beam-forming"
operates?

** Read the wiki on it yet ??

http://en.wikipedia.org/wiki/Beamforming


..... Phil

 

[Claus Jensen]

** Read the wiki on it yet ??

http://en.wikipedia.org/wiki/Beamforming

Yes, and it points out that cell phone towers also have this
capability.

I heard this from a tech once. He said that if the telco was given the
GPS coordinates of your house, they could improve the reception there
continuously. You don't even need to have your phone switched on for
them to locate you there. Does that sound correct?

I also found some relevant info here:

"Advances in Bistatic Radar"
Nicholas J. Willis, Hugh Griffiths

Parts are available for free reading on Google books.

Claus Jensen

 

[Phil Allison]

"Claus Jensen"

"Phil Allison"



Yes, and it points out that cell phone towers also have this
capability.

** So fucking what ??

YOU asked about sonar ???

I heard this from a tech once. He said that if the telco was given the
GPS coordinates of your house, they could improve the reception there
continuously. You don't even need to have your phone switched on for
them to locate you there. Does that sound correct?

** Sounds like purest bullshit to me.

Yawnnnnnnnnnnnnnn.......


.... Phil

 

[Claus Jensen]

Only if your phone transmits when it is not switched on.

That is adaptive convergence.

However, can you please explain why you believe the phone would need
to be transmitting if the GPS coordinates were known?

Are you saying this is beyond the network's technical capability, or
that it simply has not been implemented?

Claus Jensen

 

[Martin Brown]

Yes, and it points out that cell phone towers also have this
capability.

I heard this from a tech once. He said that if the telco was given the
GPS coordinates of your house, they could improve the reception there
continuously. You don't even need to have your phone switched on for
them to locate you there. Does that sound correct?

I suspect it would work a lot better if the phone was switched on. The
differences between the real world with trees, topography and metal
sheds and the idealised model of wave propagation is important.

I also found some relevant info here:

"Advances in Bistatic Radar"
Nicholas J. Willis, Hugh Griffiths

Parts are available for free reading on Google books.

The largest selection of open literature on beam forming is in the field
of radio astronomy where big phased arrays are used both for massively
increased signal with limited steering capability and higher resolution
via aperture synthesis. The mathematics is essentially the same although
some radar/sonar use chirp or other modulation for disambiguation.

In hardware terms there is an example of a GDBF from Westerbork online at:
http://www.stw.nl/NR/rdonlyres/26AEB3B8-093A-4F43-958F-F89F1BE06D0B/0/wild.pdf

Regards,
Martin Brown