The choice of GPS hardware architecture

　　The hardware system of vehicle GPS is mainly composed of antenna, RF, baseband, processor, memory, bus interface and other modules. In the system architecture, these modules can be integrated or independent. The former integrates multiple units into a system-on- chip (SoC), single-package (SiP) or module to reduce the difficulty and cost of design; the latter uses independent architectures to achieve high design flexibility. When systems engineers design, they must balance performance, cost, and flexibility.

　　Position accuracy, Sensitivity, Time to First Fix (TTFF) and Channel Number are important indicators of GPS receiver performance. Achieving the requirements of these four aspects at the same time will inevitably put forward extremely high requirements on processor performance, number of correlator channels, memory capacity and interface speed, which will greatly increase the product cost. Therefore, it is wise to choose between the four in order to meet the multi-faceted requirements of the market for performance and price.

　　ST's STA2056 provides excellent cost-effectiveness with a highly integrated solution. The STA2056 integrates the RF and baseband in the GPS receiver architecture, allowing developers to save the effort and time required for tuning, enabling faster time-to-market. STA2056 uses ARM7 TDMI as the core in the baseband part, and the frequency is up to 66MHz; the radio frequency part is an active antenna system, and also includes an interface for connecting with a passive antenna. In addition to the advantages of low power consumption, STA2056 has built-in ROM and SRAM memory, so only a few external components are needed. The STA2056 adopts a small QFN-68 package, which can effectively reduce the overall bill of materials (BOM) cost and product size, making related product designs more affordable , thin and short.

　　If the RF and baseband are separated, the design difficulty will increase, but the flexibility will also increase. The baseband module can also be embedded in Flash memory and support a richer bus interface. ST's STA2058 uses this architecture and is ideal for vehicle applications. It integrates a 32-bit MCU (ARM7TDMI) and an embedded flash memory module, and supports GPS systems such as RTCA-SC159/WAAS/EGNOS. STA2058EX also widely supports CAN, SPI, UART, I2C, USB and other interfaces, has an external memory interface, can be used as a telematics service platform, allows glueless logic (Glueless) and external devices (such as: GSM/GPRS modules, chips card, audio function DSP) connected.

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