Navman 11 User Manual

6

MN002000A © 2004 Navman NZ Ltd. All rights reserved. Proprietary information and specifications subject to change without notice.

Navman’s Jupiter series of Global Positioning 

System (GPS) receivers are single-board, 

12 parallel-channel receiver engines. Each 

board is intended as a component for an Original 

Equipment Manufacturer (OEM) product. 

GPS satellites, in various orbits around the Earth, 

broadcast Radio Frequency (RF) ranging codes 

and navigational data messages. The Navman 

Jupiter series GPS receivers continuously track all 

‘visible’ satellites and decode all available signals 

from them, producing a highly accurate and robust 

navigation solution.

The Jupiter series receivers are designed for high 

performance and maximum flexibility in a wide 

range of OEM applications including handhelds, 

panel mounts, sensors, and in-vehicle automotive 

products. These highly integrated digital receivers 

incorporate two custom SiRF devices that have the 

SiRF Jupiter chip set: the RF1A and the Scorpio 

Digital Signal Processor (DSP). The combination 

of custom devices minimises the receivers’ size 

and satisfies harsh industrial requirements.

1.1.1 Description
The receivers require DC power and a GPS signal 

from a passive or active antenna. To provide 

the lowest total system cost with minimal power 

consumption, each of the receivers provides 

only those components that are required for the 

majority of applications (e.g. if a passive antenna 

can be used with a short cable, no pre-amplifier is 

required).

The all-in-view tracking of Jupiter series receivers 

provides robust performance in applications that 

require high vehicle dynamics or that operate 

in areas of high signal blockage, such as dense 

urban centres. By continuously tracking all visible 

GPS satellites and using all of the measurements 

to produce an ‘over-determined’ and ‘smoothed’ 

navigation solution, the Jupiter receiver provides 

a solution that is relatively immune to blockage 

induced position jumps that can occur in other 

receivers with fewer channels.

The 12-channel architecture provides rapid Time-

To First Fix (TTFF) under all start-up conditions. 

The best TTFF performance is normally achieved 

when time of day and current position estimates 

are provided to the receiver. However, the flexible 

Jupiter signal acquisition system takes advantage 

of all available information to provide a rapid TTFF. 

Acquisition is guaranteed under all initialisation 

conditions as long as available satellites are not 

obscured. 

To minimise TTFF following a power interruption, 

each of the Jupiter receivers can accept external 

voltage to maintain power to the Static Random 

Access Memory (SRAM) and Real-Time Clock 

(RTC) for periods following the loss of primary 

power. The use of external voltage assures the 

shortest possible TTFF following a short power 

interruption. The OEM may extend the operation 

of the RTC by providing stand-by power on a 

connector pin, in which case a short TTFF is 

achieved by using the RTC time data and prior 

position data from the receiver’s Electrical 

Eraseable Programmable Read-Only Memory 

(EEPROM).

The Jupiter series supports two dimensional 

(2D) operation when less than four satellites are 

available or when required by operating conditions. 

Altitude information required for 2D operation is 

determined by the receiver or may be provided by 

the OEM. 

The Jupiter receivers contain two independent 

serial ports, one of which is configured for primary 

input and output data flow using the National 

Marine Electronics Association (NMEA) 0183 

format or Navman binary message format. The 

second port is used to receive Differential GPS 

(DGPS) corrections in the Radio Technical 

Commission For Maritime Services (RTCM) 

SC-104 format. The receivers support DGPS 

operations for improved accuracies over standard 

GPS.

A complete description of the serial data interface 

for the entire Jupiter series of GPS receivers is 

contained in this document.

For applications that require timing synchronisation 

to GPS accuracies, the Jupiter receivers provide 

an output timing pulse that is synchronised to 

one second Universal Time Coordinated (UTC) 

boundaries.

1.1.2 Receiver architecture
Figure 1-2 illustrates the internal architecture of 

the Jupiter receivers. Each receiver is designed 

around two custom SiRF devices that contain most 

of the required GPS functionality. 

1. The RF1A, which contains all the RF down-

conversion and amplification circuitry, and 

which presents sampled data to the Scorpio 

device.