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##### From Global Positioning Systems, Inertial Navigation, and Integration

SIGNAL CHARACTERISTICS AND INFORMATION EXTRACTION

Why is the GPS signal so complex? GPS was designed to be readily accessible to millions of military and civilian users. Therefore, it is a receive-only passive system for a user, and the number of users that can simultaneously use the system is unlimited. Because there are many functions that must be performed, the GPS signal has a rather complex structure. As a consequence, there is a correspondingly complex sequence of operations that a GPS receiver must carry out in order to extract desired information from the signal. In this chapter we characterize the signal mathematically, describe the purposes and properties of the important signal components, and discuss generic methods for extracting information from these components.

3.1 MATHEMATICAL SIGNAL WAVEFORM MODELS

Each GPS satellite simultaneously transmits on two L-band frequencies denoted by L1 and L2, which are 1575.42 and 1227.60 MHz, respectively. The carrier of the L1 signal consists of an in-phase and a quadrature-phase component. The inphase component is biphase modulated by a 50-bps (bits per second) data stream and a pseudorandom code called the C/A-code consisting of a 1023-chip sequence that has a period of 1 ms and a...

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##### Products & Services
Accelerometers
Accelerometers are instruments for measuring, displaying, and analyzing acceleration and vibration.
Inertial navigation systems use a combination of accelerometers and angular rate sensors (gyroscopes) to detect altitude, location, and motion. They may also be capable of detecting attitude, position, velocity, temperature, or magnetic field.
Antennas
Antennas are structures or devices used to collect or radiate electromagnetic waves.
Satellite Communications Equipment
Satellite communications equipment is used for the transmission, conditioning, and reception of satellite signals in worldwide telecommunications.
Navigational instruments include products such as distance meters, range finders and mapping systems.

##### Topics of Interest

4.1 RECEIVER ARCHITECTURE Although there are many variations in GPS receiver design, all receivers must perform certain basic functions. We will now discuss these functions in detail, each of which...

GPS radio signal characteristics include frequency, modulation, power level and channel coding. Frequency A frequency band is the difference between the upper and lower frequency boundaries that...

Positioning, or finding the user's location, with GPS requires some understanding of the GPS signal structure and how the measurements can be made. Likewise, as the GPS signal is received through a...

This chapter introduces serial IO in the form of asynchronous serial transfer using the Universal Synchronous Asynchronous Receiver Transmitter (USART) subsystem of the PIC18Fxx2. A serial interface...

One of the most popular and oldest methods of using modulation by digital data is the frequency shift keying (FSK) method. This method has two (or more) tones or carrier frequencies in the audio...

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