Motorola M12 Oncore User's Guide download pdf (Page 5)

Chapter 3 – Receiver Description

Motorola GPS Products - Oncore User’s Guide

Simplified Block

Diagram Description

OVERVIEW (CONTINUED)

The Oncore Receiver has an eight channel design (12-channel design for the

M12+) capable of tracking eight (twelve for M12+) satellites simultaneously. The

module receives the Ll GPS signal (1575.42 MHz) from the antenna and operates off

the coarse/acquisition (C/A) code tracking. The code tracking is carrier aided. The

Oncore receiver must be powered with regulated +5 V (Nominal 3V for M12+) power.

Time recovery capability is inherent in the architecture. The UT Oncore is designed

specifically for precise timing applications.

The Ll band signals transmitted from GPS satellites are collected by a low-profile,

microstrip patch antenna, passed through a narrow-band bandpass filter, and then

amplified by a signal preamplifier contained within the antenna module. Filtered and

amplified Ll band signals from the antenna module are then routed to the RF signal

processing section of the receiver module via a single coaxial interconnecting cable.

This interconnecting cable also provides the +5 V (Nominal 3V for M12+) power

required for signal pre-amplification in the antenna module.

The RF signal processing section of the Oncore receiver printed circuit board (PCB)

contains the required circuitry for down-converting the GPS signals received from

the antenna module. The resulting intermediate frequency (IF) signal is then passed

to the eight channel code and carrier correlator section of the Oncore receiver PCB

where a single, high speed analog-to-digital (AD) converter converts the IF signal to a

digital sequence prior to channel separation. This digitized IF signal is then routed to

the digital signal processor (also contained within the eight channel code and carrier

correlator section) where the signal is split into eight parallel channels for signal

detection, code correlation, carrier tracking, and filtering.

The processed signals are synchronously routed to the position microprocessor

(MPU) section. This section controls the GPS receiver operating modes and decodes

and processes satellite data and the pseudorange and delta range measurements

used to compute position, velocity, and time. In addition, the position processor

section contains the inverted TTL serial interface.

Warning

Keep-alive random access memory (RAM) is provided for the retention of satellite

ephemeris data, custom operating parameters, almanac information, and other

information, as specified in Chapter 5. To prevent loss of this information when the

Oncore receiver is powered off, an external +5 V (Nominal 3V for M12+) BATT

voltage is required. Retention of the real-time-clock (RTC) value also requires the

external +5 V (Nominal 3V for M12+) BATT signal when the Oncore receiver is

powered off.

Revision 5.0 08/30/02

3.5

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Motorola M12 Oncore User's Guide Page 5

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