World's leading GPS chip introduction
GPS (Global Positioning System) is the abbreviation of Global Positioning System. It can provide all-weather positioning, timing, and speed measurement functions. GPS has been widely used in aerospace, aviation, navigation, transportation, surveying, exploration and many other fields. With the development of digital large-scale integrated circuits and the need for positioning functions, GPS has begun to be more embedded in mobile handsets and consumer electronics. The US Federal Communications Commission’s e911 (enhanced 911) security clause stipulates that before the end of 2005, all new mobile phones must be equipped with a simple positioning function to facilitate the rescue unit to find the caller's location in time. The Japanese government announced in 2004 that the gps reception function was listed as a basic specification for 3G handsets and said that handsets that will be available after April 2007 will all be equipped with gps reception. Although mobile phones that integrate gps functions have not yet entered the mainstream market, the high-end models of 3G mobile phones will generally integrate gps functions in the future.
The core chip is one of the key parts of the gps system. The pros and cons of the core chip largely determine the performance differences of different gps products. The chip technology directly relates to the technical indicators and future development trend of the gps products. The huge attraction of gps' future market capacity has enabled the chip industry to develop rapidly. Currently, more than ten companies have introduced gps chips. In July 2005, Xi'an Huaxun Company launched the first gps chip in China. In 2006, the Institute of Microelectronics of the Chinese Academy of Sciences also successfully developed two gps baseband soc chips. However, the gps chips of domestic companies and research institutes have a large gap between their performance and foreign products. The existing chip market is basically dominated by several major foreign manufacturers. Among these, sirf, garmin, u-blox, and Motorola have a greater impact. Sony, Fujitsu, nxp, nemerix, unav, and other vendors, sirf, u-blox are particularly eye-catching. This article will introduce sirf and u-blox chips in detail and explain the development trend of gps chip design.
The sirf company was established in February 1995 and provides gps chip sets and corresponding software products. Its output accounts for 70% of global gps chip shipments. The sirf chip consists of a radio frequency integrated circuit, a digital signal processing circuit, and standard embedded gps software. RF ICs are used to detect and process gps RF signals. Digital signal processing circuits are used to process IF signals. Standard embedded gps software is used to search and track gps satellite signals and to solve user coordinates and speeds based on these signals. Its flagship market is Wireless handheld devices, cars, portable computing devices, and some gps professional users. In 1996, Sirf developed the first-generation gps chip structure called sirfstari architecture; in 1999 Sirf developed the second-generation chip structure sirfstarii; in 2004 sirf launched the third-generation chip structure sirfstariii. The common features of these three generations of systems are shown in Table 1.
Common features of three generations of systems
In late 1997, sirf launched a low-power sirfstari/lx chipset (low power extension for lx) based on the sirfstari architecture, which is mainly used for car navigation. The fast recapture time of the sirfstari/lx chipset is only 0.1 s, which is very important for car navigation, because in the city, the satellite signal is temporarily lost when the car runs through a tunnel or a road in a tall building. According to statistics, when a car is driving on a high-rise street, there is a good chance that it will be lost after about 4 to 5 seconds after the satellite signal is restored. The shorter the recapture time, the more positioning data will be given in a limited time. . The sirfstari/lx chipset can track satellite signals down to -180dbw, so it can also be used in areas such as trees that block satellite signals.
In 1999, sirf company developed the second-generation chip structure sirfstarii, introduced the first chip product sirfstariie in this structure, and launched sirfstariie/lp and sirfstariit chip products in 2002. Sirfstariie/lp is a low-power version of sirfstariie. The maximum current of sirfstariie/lp is only 60ma. In tricklepower mode, the current is only 20ma. Sirfstariit provides an embedded solution for integrating gps functions on some processor-based systems. The sirfstariit needs to share the processor and memory of the system before it can be used. The system processor runs sirfnav software. Sirfstarii has 1920 parallel correlators, improving the capture sensitivity, shortening the first positioning time (ttff), and cold-switching sensitivity of -142dbm.
In February 2004, sirf launched the third-generation chip architecture sirfstariii. In February 2005, sirf introduced gsc3f and gsc3 based on sirfstariii, the former including a flash memory. In November 2006, sirf introduced 90nm sirfstariii-based products gsc3lt and gsc3lti, which contains a flash memory. Sirfstariii technology is used to meet the needs of wireless and handheld lbs applications. With the corresponding software, sirfstariii can receive auxiliary data from 2g, 2.5g, and 3g networks and can locate them indoors. Sirfstariii has a hardware structure equivalent to more than 200,000 correlators, which further shortens the first positioning time.
While developing the hardware structure, sirf company also developed a series of software, making its products easy to integrate into different systems. The software includes sirfloc, sirfxtrac, sirfdrive, and sirfnav. The functional description of these softwares is shown in Table 2.
Founded in 1997, u-blox Switzerland is a well-known gps system professional manufacturing company. With its excellent navigation performance and excellent quality of gps module, u-blox has the highest market share in the global gps module market. U-blox is itself a member of the European gps Committee and Galileo's Formulation Committee. It participates in the European gps project and the formulation of G&A products and product research and development. It is currently the largest gps supplier in Europe. U-blox initially used sirf's gps chip to produce modules and used sirfstari/lx and sirfstariie chipsets. From the third generation of products, u-blox started using its own chips. U-blox's third-generation and fourth-generation chips are designed by u-blox, including chips, ip cores, and hardware and software architectures, and atmel's foundry produces chipsets. However, from the fifth generation ubx-g5 and later gps chipsets, no longer produced by atmel company OEM.
U-blox officially announced on September 25, 2006 at the US gps industry electronics show that the ubx-g5 chipset has been developed. This series of chips adopts a new design architecture, and its performance is close to the limit of gps theoretical design (gps The chipset theoretical design has a limit sensitivity of -162dbm and a cold start of 27s). The u-blox g5 is different from the u-blox gps series chips and still uses the same package as the fourth generation, but the hardware and software architecture has completely changed. U-blox g5 has the following five significant features.
There are parallel channels equivalent to more than 1 000 000 correlators, the sensitivity of which has been raised from the original -158dbm to no less than -160dbm;
Power consumption is less than 50mw;
Supports both GPS and Galileo positioning platforms.
The cold start time is shortened from the original 34s to the cold start 29s, plus aggs-assisted positioning technology, outdoor cold start can be within 1s;
The number of gps channels has increased from the fourth generation of 16 channels to the fifth generation of 50 channels;
Ubx-g5 can be applied to mobile products such as mobile phones and pdas, which greatly expands the mobile market.
See Table 3 for a comparison of the performance of u-blox and sirf's several chips.
U-blox and sirf's performance comparison of several chips
Through the history of product development of the above-mentioned gps chip manufacturers, it can be seen that the gps chip is developing in the direction of high sensitivity, low power consumption, multi-mode (galileo-compatible or other navigation systems), and a-gps.
When other manufacturers develop gps products, they should focus on the future of integrated gps in a variety of it equipment, such as mobile phones, digital cameras, pda, notebook computers, do embedded solutions, do not develop and sirf and u-blox company Competing independent gps chip. Secondly, we must solve the problem of high sensitivity and low power consumption. We should align with the most advanced u-blox g5 chips and develop algorithms and hardware for weak signal acquisition and tracking.
Before 2010, the galileo system will be commercially available worldwide, so the development of gps/galileo dual-mode receivers has a broader perspective. On this basis, if we can make gps/galileo/BeiDou three-mode GPS receivers will be more competitive. The development of pure software gps receivers, through the software to complete the gps chip functions, thereby further reducing costs, prompting more portable handheld devices to use gps features.