[time-nuts] GPS down converter question

[Magnus Danielson]

Hi,

This is a side-track to Pauls original question, but maybe a nice little 
point to make now that Peter touched on the subject.

To elaborate a little on C/A and multipath surpression.
The multipath surpression of the receiver depends on code rate, 
bandwidth and correlator spacing. P-code is able to surpress more, and 
the C/A code errors look about the same as the P-code, but scaled 
accordingly. Increasing the bandwidth helps to reduce the C/A errors, 
but taking the next step of using narrow correlators further reduces the 
error. This is shown already in the classical Spiliker book, but further 
readings from Novatel could be nice.

Increasing the bandwidth and narrowing the early and late correlator 
taps both have the effect of reducing the time over which energy goes 
into the E-L difference, and hence reducing the impact of multipath into 
the solution.

Cheers,
Magnus

On 12/01/2015 06:00 AM, Peter Monta wrote:
>>
>> What should the IF pass band bandwidth be?
>>
>
> For GPS C/A with wide correlator, about 2 MHz; if you want Galileo BOC and
> (eventually) GPS L1C, or legacy C/A with narrow correlator, about 8 MHz;
> for GPS P code about 20 MHz.  Books on GNSS software receivers will detail
> the many tradeoffs available---if you're starting out with a
> proof-of-concept lab receiver, go for 8 MHz.
>
> Cheers,
> Peter
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