GPS receiver, the device will receive from the positioning satellite navigation signals, is a one-way GPS signal receivers. First of all, GPS antenna will first receive GPS satellite signals, and then will be front-end RF high-frequency radio signals to, the low-frequency digital signal is sent to GPS baseband module. The core technology of baseband is Correlator design. Correlator is mainly used to find the right than the number of satellites, then mutatis mutandis, to get the Almanac and BroADCast Ephemeris, and other information. Associated with the more means more access to more quickly find the location of satellites, GPS receivers are generally provide at least 12 channels of relevant, more advanced receiver has a 16 or even 32-channel correlator.

              Figure 1 GPS receiver hardware structure

The end control function of GPS receiver is to achieve by MCU or microprocessor. Processor is an independent unit, and base-band can also be integrated. The current low-end GPS receiver products are usually used as the ARM7 core high-end products are generally for the ARM9. In addition, these components will have the microprocessor support functions, such as UART and real-time clock (RTC), and so on.

Broadcasting ephemeris data to NMEA 0183 or RTCM formats output to the main processor, and further integration of the engine and GIS maps to show the location of the street; can also be sent through a wireless communication interface location information to a remote server can provide further relevant Location services. NMEA 0183 GPS is used as a standard protocol, it used to simplify the serial ASCII protocol to define the format of data transmission.

The United States WAAS or European EGNOS system adopted DGPS auxiliary mode, when using the GPS mode, the output RTCM require the agreement or NTRIP 1.0 format.

In addition, since different receivers provided by the original data format usually different, we must establish a common GPS data exchange format for different types of receivers to collect uniform data processing. The industry generally adopted the format for the RINEX.

The selection of GPS hardware architecture
Car GPS hardware system is mainly made up by the antenna, RF, baseband processor and memory, a bus interface modules. In the system architecture, these modules can be integrated or stand-alone. The former multiple units for an integrated system-on-chip (SoC), single package (SiP) or module, designed to reduce the difficulty and cost of the latter using separate structure designed to achieve the high flexibility. When system engineers design, they must weigh among the three areas importance of performance, cost and flexibility.

Position accuracy, Sensitivity, Time to First Fix (TTFF) and Channel Number are the important indicators of GPS receiver's performance. At the same time achieving the requirements of these four aspects will be in processor performance, the number of channel-related, the memory capacity and speed interfaces, such as by the high demand, substantial increase in cost of the product. Therefore, the sensible approach is to trade-off between four to meet the market's performance and price of various requirements.