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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Chipsets for building Spread Spectrum devices. Reference data
Encyclopedia of radio electronics and electrical engineering / Reference materials Broadband data transmission systems, or Spread Spectrum, produced by various foreign companies, differ from each other primarily in the method and speed of data transmission, modulation type, transmission range, service capabilities, and so on. The author considers chipsets for Spread Spectrum depending on their application. Abbreviations Used ASK - pulse amplitude modulation BPSK - phase modulation CDMA - code division multiple access DPSK - Differential Pulse Phase Modulation DSP - digital signal processor DSSS (Direct Sequence Spread Spectrum) - broadband signals obtained by the direct sequence method FHSS (Frequency Hopping Spread Spectrum) - frequency hopping method FSK (Frequency Shift Keying) - frequency shift keying GMSK - Gaussian frequency modulation MBOK - M-ary bi-orthogonal modulation QPSK - quadrature phase modulation RSSI (Received Signal Strength Indication) - indication of the level of the received signal SOIC,TQFP - surface mount package types More than 20 companies are involved in the development and manufacture of chipsets (Chipset) for Spread Spectrum devices. The range of application of chipsets is quite wide. Depending on this, Spread Spectrum devices can be roughly divided into three categories: • radio modems for building wireless local networks; • office radiotelephones (radio tubes); • various low-speed devices for telemetry, burglar alarms, etc. CDMA code division systems and GPS global positioning systems should be added to this classification, but consideration of their element base is beyond the scope of this review. When describing the sets of microcircuits used, the authors do not pretend to be a complete review, since the manufacturers of the final equipment, for obvious reasons, do not advertise the components used in their devices. The information of some chip manufacturers is difficult to access even now, in the age of the Internet. Chipsets for building radio modems Let's start the review with the STEL-2000A chip, developed by Stanford Telecom and now licensed by Zilog under the trade name Z87200. The chip is a programmable spread spectrum transceiver using direct sequences. The Z87200 supports noise-like code lengths from 2 to 64 chips per bit over a wide range of data rates and spread spectrum parameters. The maximum transceiver speed is 2 Mbps. The Z87200 is available in two versions (25 MHz and 40 MHz) and performs all the digital processing required to encode and distribute transmitted data and receive and decode it. This transceiver uses differentially coded BPSK and QPSK modulations as modulation, in addition, the receiver section can work with differentially coded pi / 4 QPSK. The Z87200 is used in some Aironet Wireless Communications modems. In addition, Zilog has partnered with Utilicom Inc., which produces RF sections that are compatible with the Z87200. The cost of the Z87200 in Russia is approximately $25. The FHSS technology kit is offered by Mitel. The beginning of the development of the kit ideology and its first samples belong to the achievements of GEC Plessey Semiconductors, which was subsequently acquired by Mitel. Mitel carried out further development of the project independently. The new set of chips consists of three devices: • WL102B - noise-like controller; • WL600C - RF chip; • WL800 - frequency synthesizer. These chips belong to the third generation of the DE6000 family of GEC Plessey Semiconductors and are collectively called DE6038. The entire set is currently available for less than $25. (for 1000 pieces). Let's take a closer look at this kit. WL102B - CMOS SPS-microcontroller with internal architecture 8051 and external flash-memory, which performs the entire procedure of converting the information symbols of the PCMCIA interface into a "jumping" frequency signal. The maximum information speed is 2 Mbps. WL600C is a 2,4-2,5 GHz RF transceiver operating at 2,7-3,6 V. It includes a low-noise amplifier, a mixer with unwanted spectral components filtering, an IF limiter amplifier, a quadrature demodulator, an amplifier power with control circuit, RSSI circuit in the receiver. Two-level FSK modulation is used. WL800 is a low-power frequency synthesizer operating at 2,7-3,6 V with a maximum frequency of 2,5 GHz and programmable via a classic 3-wire bus. The features include a built-in spurious modulation suppression circuit. A faster Spread Spectrum kit, tradenamed PRISMTM, is available from Harris Semiconductor. The set consists of HFA3860 NPS processor, HFA3724 quadrature modulator-demodulator, HFA3524 dual-frequency synthesizer, HFA3624 receiver and transmitter mixer unit, HFA3424 low-noise amplifier, HFA3925 antenna switch with final power amplifier for transmitter. The kit is interesting in that Harris Semiconductor offers both parts of the project - both the processor and the radio frequency. By the way, the company produces a variety of microcircuits of the radio frequency path, which makes it possible, depending on their application, to choose the most optimal solutions. The DSSS-enabled HFA3860 BPA processor contains all the features required for full or half duplex operation at 11 Mbps. The NPS processor includes two ADCs /open abbreviation/ for analog I- and Q-inputs. The type of modulation used is differential BPSK and QPSK, as well as MBOK. A feature of the processor is the input signal level control function (through the RSSI scheme), which allows you to more accurately determine the presence of a useful signal, avoid conflicts and thereby improve network performance as a whole. The processor is available in a 48-pin TQFP package and is capable of operating in the temperature range from -45 to +850 C. The remaining microcircuits of the set are built classically and do not need a detailed description. Kits for building office radiotelephones Zilog offers two chips for the Spread Spectrum radiotelephone: Z87000 - controller, Z87010 - audio encoder / decoder. The Z87000 is a Frequency Hopping transceiver/controller designed specifically for 900MHz cordless phones. The Z87000 contains a 16-bit digital signal processor (DSP) and a controller to control the RF section. This transceiver uses FSK modulation and transmit-receive time division. The transceiver is produced in two versions, designed for use in the temperature range from -20 to +700C: • Z87000 - with supply voltage 5 V; • Z87L00 - with a supply voltage of 3 V. The Z87010 is a 16-bit DSP designed to encode voice into a digital signal and then transfer it to the Z87000 processor, as well as to convert the digital signal coming from the Z87000. A finished radiotelephone, both a wearable handset and a base station, should consist of three parts: the Z87000 and Z87010 already described above and the 900 MHz RF section. The latter appeared as a result of close cooperation between Zilog and Analog Devices in the form of a single-chip AD6190 transceiver. It contains all the necessary components, namely: - low noise amplifier; - receiver mixer; - transmitter mixer; - transmitter power pre-amplifier; - VCO; - frequency divider; - Limiting amplifier with RSSI circuit; - Voltage regulator. The AD6190 transceiver is specifically designed to interface with a Zilog kit, but can also operate independently as the RF section of a cordless phone or Spread Spectrum radio. A similar kit for building a cordless telephone in the 900 MHz range was proposed in 1998 by AMD. Considering the requirements of customers of the final equipment, AMD has developed a kit that, with a minimum chipset, has great design flexibility. The kit consists of a DSSS Am79C440 spread spectrum transceiver and an Am79RF440 RF transceiver. The Am79C440 controller is a high-tech microcircuit that supports the telephone protocol and performs data formatting, sound processing, and RF transceiver control. Its core is an 8-bit microcontroller compatible with the 8051 family. In addition, the controller has a number of service functions that have become quite familiar to modern equipment: low battery indication, the ability to switch to low power consumption modes, and others. The Am79RF440 combines all the functions required to receive and transmit signals in the 902-928 MHz range, using GMSK - Gaussian frequency modulation as modulation. Serial production of the kit was scheduled for August 1998. The cost of Am79C440 and Am79RF440 (for 100 thousand pieces) is 5,95 and 3,95 dollars. respectively. Low-speed devices for telemetry, burglar alarms Micron Communications, Inc. offers the MSEM256X105G chip designed for remote access systems. The chip is housed in a 20-pin SOIC package and is a complete transceiver based on DSSS technology. The principle of its operation is interesting: the transmitter signal is emitted at a frequency of 2,44175 GHz (it uses amplitude-pulse modulation - ASK), and a signal at the second carrier frequency of 596,1 kHz modulated already by differential pulse-phase modulation (DPSK) is received at the receiver input. The code length is unchanged and is 31 chips. With a supply voltage of 3 or 5 V, the average current consumption is only 5 mA. The range of such a transceiver is small - 15 feet, the sensitivity of the receiving device is 17 dBm, the transmitter power is not indicated. The maximum information rate is 189,3 kbps. The device is designed specifically to identify moving objects, for example, when a vehicle passes through a checkpoint. Along with the chip, the manufacturer offers a base station, a microantenna, as well as its own physical interaction protocol - MicroStamp EngineTM, and guarantees at least 4 billion user units of a single system. Another distributed spectrum method - Frequency Hopping - underlies the microcircuit of the Norwegian company Gran Jansen AS. The GJRF400 chip is also a complete transceiver that performs all the digital processing of data symbols, their conversion to a noise-like signal, and then to an RF signal in the 300-500 MHz range. The type of modulation used is FSK. The microcircuit has a transmitter output power of 5 mW, a receiver sensitivity of 110 dBm, a maximum information rate of 19 bps, and at a supply voltage of 200 V, the current consumption is about 3 mA. It is produced in a 40-pin TQFP package and can operate in a temperature range from -44 to + 40C. The cost of the GJRF850 is approximately $400. (for 13 pieces). The microcircuit is applicable in wireless local networks, remote access devices, alarm and security systems. Conclusion In addition to the above, chips for Spread Spectrum technology are produced by the following companies: Alfa Inc., The American Microsystems Inc., Atmel, Axxon, Cylink, Diablo Research Corporation, Digital Ocean, FreeWave Technologies, Intellon, Motorola, OKI Semiconductor, Proxim, Pulse Engineering, Rockwell WCD, Lucent Technologies, Texas Instruments, Mitsubishi, Samsung, Sony and others. Of the companies producing microcircuits for the radio frequency part, the most famous are Hewlett Packard, Motorola, Philips, RF Micro Devices, TriQuint Semiconductor and others. It should be noted that the tendency of manufacturers of such microcircuits is to increasingly integrate composite components on a single chip. However, modern technology so far allows only the simplest systems with a limited set of functions, low speed, etc. to be combined on a single chip. The matter is complicated by the fact that the harmonic components of the signal that occur during digital processing often do not get along well with the radio frequency part, which also has enough problems with today's spectrum frequency requirements. But still, in the near future, we should expect the appearance of not sets of chips, but individual microcircuits that perform the described functions with the speeds required by modern standards. Literature
Author: Malygin Ivan Vladimirovich; Publication: library.espec.ws
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