Navigation Laboratories has tightly integrated its Tapestry controlling software with a flexible and powerful hardware platform. This integration achieves a synergism unparalleled in GPS Constellation Simulator performance.  The digital and RF hardware are combined within a 4U all-steel chassis. It is relatively light weight and easy to move around.

Simulation Chassis Assembly

Main Hardware Components

Digital Signal Processing Module - X14-DSPM-(L1L2)

The essence of our GPS signal is constructed digitally using state-of-the-art components. Our signal is highly stable with a very low noise floor as a highly stable ovenized oscillator serves as the time reference. This design, when combined with our base band to RF implementation, is free from interchannel bias errors. The only variable component is the power output level and attenuator linearity. Both are calibrated at the factory. Our included calibration software application allows your to repeat the calibration at your facility without returning the unit to us.  The system is warranted for 1 year parts and labor and can be extended for a nominal cost.

Power can be adjusted on the channels in two steps. Overall - that is, all channels move together - we have 30 dB in step sizes of 0.5 dB. On a per channel basis - that is, one channel moves relative to the others - 36 dB of dynamic range is provided. Power adjustment can be made manually, based upon a programmable script, or dynamically based upon the attitude of simulated host vehicle.  

Our hardware is controlled by the Tapestry computer system at 1/2 kHz update intervals. Polynomials for range, range-rate, range-acceleration, and range-jerk are used to provide a seamless dynamic output.  The unit can run unattended for extended periods exceeding 24 hours. 

Our range accuracy is better than 0.003 m one sigma (limited by the phase noise on the test receiver we used to measure these values) and our dynamics are in excess of 15,000 m/sec line-of-sight velocity, acceleration of 100 G's and jerk of 500 G/sec.  

Two serial ports are built in. These can be used to interface to the receiver unit under test. Using the supplied serial interface, the Tapestry software can display the measured position and velocity errors by comparing receiver data to truth data.  This data is plotted real-time and logged in ASCII to the hard drive. 

Multi Function Input Output (MFIO) expansion module.

We have developed a PCI plug in card to complement the X14-DSPM. With the MFIO card, the Tapestry system can dynamically control the voltage levels on eight 5VDC analog outputs, eight discrete I/O lines (can be pulsed) and one channel of differential data output. There is an on board SDLC protocol chip.  The user can use the internal clock on the board or it can lock to an external reference. It can be addressed and controlled by the Tapestry software in a myriad of intriguing possibilities.  

We use the MFIO to generate analog outputs that simulate turn-rate gyros and accelerometers like those found in automotive navigation systems. Four - independent - wheel tick outputs can be generated. We can simulate the electrical and data interface of strapdown Inertial Measurement Unit (IMU/IRU) with or without SDLC protocol. We have even used one channel to control a turn-table and temperature chamber.  This board can be used as a master timing card if slaved to the 1-PPS output of the DSPM.

Expansion Capability

In addition to the main GPS and MFIO capabilities, our simulator can also be combined with additional plug-in expansion boards to further enhance the capabilities of the system. These include GPIB / Ethernet  / ScramNet - allowing for remote or closed loop control. Additionally we support the Ballard 1553 PCI expansion card - allowing for GPS-059 INS outputs and G-message data extraction. The Ballard ARINC-429 card is also supported.  We have driven the TRIO-TECH S323B Turn Table with ± 10 Volt control.  

Y-Code / SA/AS

Currently our DSPM is not approved to generate AS/AS,  SASM, or Y code. We are planning a daughter card security module. In the interim, we have a classified Tapestry link the uses the Rockwell Collins PCSG with YCB daughter card. The hardware generates the Y code signals based upon the Rockwell Collins AOC.  The Selective Availability is implemented in our software with a KYK-13 interface. 

Navigation Laboratories Inc. (949) 766-0444, (949) 495-9551, Fax (949) 713-2479