In 1999, the industry has set up a Wi-Fi alliance, which is committed to solving the production and equipment compatibility of products that meet the 802.11 standards.
Wi-Fi is not only applied to almost every smartphone currently sold, but also almost all handheld game consoles, tablets, laptops. There is a Wi-Fi chipset in a large number of new applications involving automotive, digital cameras, e-book readers, Bluetic devices, and individual video recorders and each device. Therefore, the market research firm in-stat Prediction will exceed 1 billion sets of annual output of Wi-Fi chipsets in 2012.
At present, the development trend of Wi-Fi chip except the rate of 54Mbps IEEE 802.11b / g baseband chip, there are several trends:
Trend 1: Development of high speed. This type of chip supports supporting 1 x 1 802.11N standard with a rate of 150 Mbps. The 802.11n chip rate of MIMO technology reaches 300 Mbps or more, mainly used for the transmission of HD images; it is worth paying attention to the high-rate chip support standard will transition from IEEE 802.11A to IEEE 802.11ac (6GHz or less). 1Gbps) and IEEE 802.11ad (60GHz operating frequency band, speed up to 7Gbps).
Trend 2: Low power consumption, low rate direction. This type of chip emphasizes low power consumption, low rate requirements, and the rate can be 2Mbps, and only support IEEE 802.11b standard, in industrial applications, Internet applications, there is a large market.
Trend 3: Fusion of other networks, such as 3G and the fusion of 4G networks in the future.
The architecture of the Wi-Fi baseband chip is generally based on whether the processor is used to distinguish it:
The full-hardware type, does not use the processor, the MAC (Medium Access Control, Media Access Control) layer and PHY (Physical Layer, physical layer) of the entire chip, is implemented by hardware logic.
The second is a semi-soft semi-hard type, and the processor is used in the MAC layer, which is generally the MIPS core, and there is a small portion of the ARM core; the physical layer is implemented in hardware logic.
The third is all soft, and this chip uses high-speed DSP, Mac and PHY all by software.
These types have their own advantages and disadvantages, and there are in the market. In general, the full-hardware design is relatively difficult, and the processing speed is relatively fast. And because there is no processor, the cost is relatively low. The third full software type can be flexible and upgraded. With the high speed, small area and low power development of the DSP, the proportion of full-software design will gradually increase.
SCI baseband chip introduction
S901 Chip Structure: The Wi-Fi baseband chip described herein is the first generation Wi-Fi baseband chip of the SCI. The process is 0.18 microns CMOS, the interface is a USB 2.0 interface. It belongs to the previous type of full-hardware type, and the Mac and PHY inside the chip are implemented by hardware. The chip structure is shown in Figure 1: The entire baseband chip is divided into a USB interface portion, MCU, Mac, PHY, ADC / DAC. Built-in MCU performs a USB firmware program.
Development Process: The entire design uses the top-down design method, first designing the chip architecture, divides the chip into three main parts of the drive, Mac, and PHY. The design of the driver is carried out by the design method of software engineering; because the driver is running in the PC side, the hardware (NIC) is interactive, the communication message must first be set. After the design of the MAC section, after the analysis protocol, the hardware and software is divided, and those are completed by hardware, those completed by the software. The physical layer involves more communication algorithms, such as frame synchronization algorithms, frequency synchronization (crude frequency synchronization, fine frequency synchronization), channel estimation, coding decoding, modem, etc., need to perform simulation determination algorithms. The development process of the entire physical layer is shown in Figure 2.
Simulation: During the development process, the algorithm of the physical layer has been strictly simulated. The simulation results begin to perform HDL design after satisfying the design indicators. Figure 3 below is OFDM modulation demodulation results. Standard: Per "10%, SNR" 25 @ 54Mbps.
Technical features: The baseband portion does not use the processor, reduce the chip area and improve processing speed; the in-kind MCU is responsible for performing USB firmware programs and execution of the MAC layer and physical layer; the physical layer algorithm adopts autonomous algorithm; support WAPI, IEEE802. 11i encryption standard, multiple encryption methods seamless integration; Mac real-time requirements are not high by software, easy to upgrade and maintain.
Chip area: The logic unit of the chip is: 863K Gates (Mac + PHY + USB + MCU) Memory size is: 271kbits. DIE Size at 0.18um is: 23mm2 (including an analog part such as ADC / DAC / LDO). S901 chip layout is shown in Figure 4.
Chip power consumption: The entire baseband includes the power consumption of internal ADC / DAs as shown in Table 1.
Table 1: S901 power consumption table
Wireless network card design based on SCI Wi-Fi baseband chip
Structural and main technical indicators of SWM9001 Wi-Fi wireless network card
SWM9001 is based on Suzhou Zhongke Semiconductor Integrated Technology R & D Center Co., Ltd. (spiritual core integration) has independent intellectual property RF chip S103 and a baseband chip S901 Wi-Fi wireless module, which has won Wi September 30, 2011 -Fi alliance products, number is WFA12939. The wireless module is a product that domestic users use independent intellectual property Wi-Fi chip design. The following figure 5 is a structural diagram of a network card, and FIG. 6 is a network card profile.
Figure 5: SWM9001 network card composition
Figure 6: SWM9001 profile
The main indicators of the SWM9001 network card are as follows:
* Compliance with IEEE802.11b / g / E / h / I standard, while supporting WAPI encryption standards;
* Encryption standard: 64/128 / 152bitWep, WPA / WPA2 / WPA-PSK / WPA2-PSK, WAPI
* Interface: USB2.0;
* Transmission rate: 6/9/12/18/24/36/48 / 54Mbps @ 802.11g; 1/2 / 5.5 / 11Mbps @ 802.11b;
* Modulation method: BPSK / QPSK / 16QAM / 64QAM @ 11g;
DQPSK / DBPSK / DSSS /
[email protected];
* Receive sensitivity: -71dBm @ 11g, 54m; -90dBm @ 11b, 11m;
* Drive: Window Me / SE / XP / 2000 / Vista / Win7, Linux 2.6.28and Android 2.1 / 2.2 / 2/3;
* Transmission distance: 100 meters indoors, outdoor: 300 meters.
Application range: The spiritual core set provides a complete solution for this reference design (schematic, PCB, BOM table, driver), product design fully considers power consumption, stability, ease of use, and expandability. Performance is in place in homologous products, and the price has a considerable competitive advantage.
The Wi-Fi wireless module can be applied to PC wireless network card, wireless video transmission, home wireless gateway, industrial data wireless transmission, etc.
SWM9001 wireless network card design techniques and considerations
The circuit of the wireless network card mainly includes a radio frequency front section module (FEM), a radio frequency module (RF), a baseband chip, and a power supply portion. The matters needed in the design are mainly the electromagnetic compatibility and interference issues of RF forerunage module (FEM), RF modules (RF):
1) FEM filter capacitor 100UF; because the PA part of the FEM is large, a large-capacity filter capacitor is required;
2) The power input of the Wi-Fi RF unit needs to be stringed into a magnetic bead to suppress high frequency noise and spike interference on the power cord, improve the emission;
3) Active crystal (40MHz) clock line width should not be less than 8 mils, a bottom layer or the bottom layer; do not walk 40MHz clock in the internal electrical layer, the shorter the clock line, the better, if necessary, The recommended hole size is 30 mils, and the inner diameter is 15mil;
4) The 50OHM impedance line recommended on the four-layer PCB is 12mil; the radio frequency portion must retain a complete level surface;
5) When the PCB layout, the DC-DC is close to the USB interface; the clock line is farther away from the 50OHM impedance line.
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Source: Wiku Electronic Market Network
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