IFR / Aeroflex GPS-101-2

GENERAL

The GPS-101-2 Global Positioning Simulator provides for installation and functional bench testing of global positioning system (GPS) receivers. The GPS-101-2 simulates one of many specific global positioning satellites. Selected specific satellite vehicle (SV) signals transmitted with selected navigation (NAV) data test patterns are used to verify the operational integrity of GPS receivers.

SYSTEM OPERATION

Most GPS receivers operate by receiving the coarse acquisition (C/A) encoded signals on the L1 (1575.42 MHz) channel. The receiver uses the C/A encoded signal to calculate the distance from each specific satellite. The combined 50 Hz NAV data and C/A encoded satellite signals contain satellite position and information accuracy. The full navigation message contains 25 data frames, each having 1500 bits of information and includes an almanac for the receiver data base. The full navigation message takes about 12.5 minutes to transmit. The almanac data base in the GPS receiver maintains position information on all the satellites for any given time. From the last acquired position and using the almanac data base, the GPS receiver selects three (two dimensional positioning) or four (three dimensional positioning) of the best satellites known to be in view at the current time. After the receiver starts tracking the three or four selected satellites, position is calculated using the received information.

FUNCTIONAL CAPABILITIES

The GPS-101-2 has the following functional capabilities:

• Generates GPS signals on the L1 channel (1575.42 MHz) frequency.
• Provides adjustable RF output level from -85 to -145 dBm in 1 dB steps (to verify system and/or receiver sensitivity).
• Offsets Doppler frequency as selected (no shift, -4 or +4 kHz).
• Simulates one of 32 global positioning satellites or one of five ground stations by transmitting the selected phase modulated C/A code (Gold Code) signal identifying the particular satellite or ground station.
• Provides selectable preset 50 Hz NAV data test patterns. O Allows uploading and downloading of almanac data. Refer to Appendix B.
• Provides adjustable date and time. (The GPS-101-2 has the current date and time [UTC] loaded initially at the factory.)
• Operates on battery power for approximately six hours.