st20-gp6 STMicroelectronics, st20-gp6 Datasheet - Page 11

• Manufacturer Part Number: st20-gp6
• Description: Gps Processor
• Manufacturer: STMicroelectronics

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The ST20-GP6 chip includes 12 channel GPS correlation DSP hardware. It is designed to handle
twelve satellites, two of which can be initialized to support the RTCA-SC159 specification.
The digital signal processing (DSP) module extracts GPS data from the incoming IF (Intermediate
Frequency) data. There are a number of stages of processing involved; these are summarized
below and in Figure 3.1. After the 12 pairs of hardware correlators, the data for all channels are
time division multiplexed onto the appropriate internal buses (i.e. values for each channel are
passed in sequence, for example: I
The main stages of processing are as follows:
Data sampling
This stage removes any meta-stability caused by the asynchronous input data coming from an
analogue source (the radio receiver). The data at this point consists of a carrier of nominally
4.092 MHz with a bandwidth of approximately 1 MHz.
This stage is common to all 12 channels.
4 MHz IF
Digital signal processing module
input
sampler
data
noise sequence
Pseudo random
converter A
frequency
generator
(x 12)
ST20 CPU accessible
Figure 3.1 DSP module block diagram
registers
1
, Q
1
Q correlator
, I
Numerically
I correlator
controlled
oscillator
2
(x 12)
(x 12)
, Q
2
... I
12
, Q
converter B
12
frequency
, I
1
, Q
1
).
accumulator
interface
DMA
ST20-GP6
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