[time-nuts] GPS Filter

[jimlux]

On 3/7/11 10:27 PM, Chris Albertson wrote:
> On Mon, Mar 7, 2011 at 7:34 PM, Bob Camp<lists at rtty.us>  wrote:
>> Hi
>>
>> Since you are after timing off of the sat's, having antennas that move, either physically or electrically seems like a problem. Any shift in the effective antenna location as you tracked the satellite would be "exciting" to compensate for. There was an early paper published based on doing this (early 80's).
>
> I don't think anyone would build a phased array GPS antenna but if
> they did the elements of the array would only move within a 1/2
> wavelength range.  For GPS I think this less than 2 centimeters.   but
> the effective center of the antenna would not have to move.
>


GPS Wavelength is (for L1) is about 20 cm.. longer for L2 and L5, of course.

It's not too tough to make sure that the apparent phase center of a 
phased array doesn't move, and a lot of precision GPS processing already 
deals with the phase center moving as a function of look angle.