[time-nuts] GPS Filter

[jimlux]

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.