jimlux wrote:
On 3/8/11 4:24 AM, Pieter ten Pierick wrote:
Hi,
GPS phased arrays aren't new, nor is it necessary to physically steer
the antennae within the aray:
http://www.navsys.com/papers/0005004.pdf
But would such a system help with the LNA overload due to a local
transmitter?
I would expect that using separately steered antennas with good
directivity could prevent this out-of-band LNA overload?
As long as your phasing is done before the one-bit ADC, you can place
a null on the offending interference source. This has been used for
adaptive interference cancellers for decades (for cosited transmitters
and receivers). A friend worked for American Nucleonics back in the
80s when they were starting to implement digital control loops (but
the cancellation was still done with analog techniques) for this
application.
You *might* be able to do it even after the sampler, if the
interfering signal isn't too strong. At a guess, if the total noise
power at the input to the sampler were within about 10dB of the
interfering signal, you'd probably be ok. When the interfering signal
gets up to 10-20 dB over the noise power, it starts to really dominate.
Replacing the 1 or 2 bit ADC typically used with a higher resolution ADC
may be necessary if the interfering signal is very strong.
This approach is likely to be adopted for the SKA to mitigate
interference over the very wide bandwidth this telescope system is
intended to cover.
Bruce
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
