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A good example of what you can get today is the Micrel MICRF receiver family, which comprises 418- to 433-MHz- and 900-MHz-band devices. The lower band, 16-pin MICRF002 and eight-pin MICRF022 and higher band, but otherwise similar, 16-pin MICRF003 and eight-pin MICRF033 use an architecture that eliminates the need for manual tuning of each unit (Figure 1). These superhet receivers, which target on/off keying, or amplitude shift keying (ASK), require few external components: a 47-nF capacitor, a 4.7-μF capacitor, and an inexpensive, 6- to 7-MHz ceramic resonator. These ICs need no filters or inductors. The higher frequency, $4.50 (1000) MICRF003/033 supports data rates as fast as 20 kbps, and you provide the data from a CMOS-logic interface. The IC consumes 4 mA from a 5V supply in normal operation and one-hundredth of that value in shutdown mode. You can set the receiver to periodically wake up and check for incoming signals; this duty-cycle-oriented operation results in an overall dissipation that is near the shutdown value. Texas Instruments recently introduced its TRF6900 transceiver for 850- to 950-MHz operation and the associated MSP430 ultra-low-power, 16-bit μC for burst-mode operation and low power consumption. The fairly complex 48-pin transceiver supports FM, FSK, on/off keying, and ASK operation and produces as much as 6-dBm output power from a 2.2 to 3.6V supply. Within this IC is a channel-hopping, 24-bit, direct-digital synthesizer with an 11-bit DAC and 230-Hz resolution; a reference oscillator and a VCO; a received-signal-strength-indicator (RSSI) block; and a serial interface to the μC. The IC lets you send data as fast as 200 kbps, and you can selectively turn its internal blocks on and off to minimize power consumption. To facilitate this technique, the blocks within the IC turn on and off within 500 msec, and you can get standby power consumption as low as microamps. Along with the detailed data sheet, TI offers application notes, μC- and PC-based software, a reference design, a bill of materials, and RF-layout files. To complete your RF portion of the design, you need a UHF filter, an IF filter, and a crystal, plus a few resistors, capacitors, and inductors, which cost $1 to $5, depending on the application. Mitel is extending its transmitter and receiver line with ICs such as the KESRX05, a PLL-controlled receiver upgrade of its older KESRX04 unit, which locks to a reference crystal via an internal divide-by-64 prescaler. This 260- to 470-MHz receiver uses ASK modulation and allows data rates as fast as 100 kbps, although the typical data rate is less than 5 kbps. Sensitivity of the receiver is -106 to -109 dBm at 433 MHz at a 2-kbps data rate and 50% duty cycle. Mitel has also redesigned the receiver with an antijamming circuit that rejects adjacent-channel interference at 433.92 MHz, such as that from nearby amateur-radio repeater signals. This feature lets you use a low-cost LC front-end filter instead of a slightly more costly SAW filter. The redesigned receiver also extends the operating temperature from 85°C for its predecessor to 105°C; this extension is an important factor in many practical installations in which ambient temperature plus impinging sunlight can push the IC temperature quite high. Infineon Technologies (formerly, Siemens Components) is also extending its 400-MHz products to the higher bands. The company offers the TDA5100 ASK/FSK transmitter for both the 868- to 870-MHz and the 433- to 435-MHz bands and the complementary TDA5200 ASK superhet receiver for European markets. Infineon also offers the similar TDA5101 and TDA5251, which target the US market, for the 315- to 345-MHz band. The transmitter is a 16-pin TSSOP IC that costs $1.50 (50,000) and operates from a 2.1 to 4V supply. It integrates a VCO, PLL, crystal oscillator, supply-rail regulator, and power amplifier. You use the transmitter with a μC operating from the same clock crystal as the transmitter. The receiver uses a 5V supply and includes a VCO, a PLL, a limiter, filters, and a data comparator; the receiver's sensitivity is 1 μV. The 85-cent (50,000) IC comes in a 28-pin TSSOP. Motorola offers some wideband ICs that you can use, along with a baseband signal processor, for your RF channel. The company's MC13146 dc to 1.8-GHz transmitter pumps 10-dBm output at a 1-dB compression point. It includes a linear mixer, VCO, dual-modulus prescaler, and power amplifier. Operating voltage is 2.7 to 6.5V, with current drain of less than 25 mA at 1.8 GHz; in power-down mode, consumption drops to 60 μA. The matching MC13145 receiver has a low-noise amplifier, two mixers, a VCO, a dual-modulus prescaler, an IF amplifier and limiter, an RSSI circuit, and an inductorless FM/FSK demodulator. The transmitter is available as a 24-pin LQFP device; the receiver is a 48-pin LQFP IC. A transceiver IC from Chipcon Components AS is noteworthy because of its relatively high output power and consequent range. The CC400 FSK for 300- to 500-MHz ISM applications provides 9.6-kbps, half-duplex operation to 2000m (Figure 2). The output-power range spans -5 to +14 dBm, which you can program in 1-dB steps; receiver sensitivity is -112 dBm at 1.2 kbps and a 10-3 BER. The 28-pin SSOP IC operates from a 2.7 to 3.3V supply with current requirements of 18 mA with the receiver on full-time and 180-μA average operating current using receiver polling. The vendor also supplies a development kit that includes PC-configurable radio modules, cables and connectors, and PC-based software. RF Micro Devices recently introduced a spread-spectrum transmitter- and receiver-IC pair for the 902- to 928-MHz ISM band. The RF2908 includes a double-conversion receiver, a quadrature modulator, dual IF amplifiers, filters, data comparators, and a PLL synthesizer. This 68-pin LQFP IC costs $5.25 (10,000). The matching RF2909 supports direct modulation control, and you can set the output-power level of this 24-pin SSOP from 1 to 80 mW; it costs $2.35 (10,000). Also for 900-MHz use, Level One has the LXT 810, a 32-ksps spread-spectrum transceiver with 100m range (1 to 100 mW output), and which needs no tuning, adjustments, or filters. A complete design with this IC uses under 30 discrete components. If you can consider hybrids instead of just ICs, you'll find that vendors such as RF Monolithics offer some devices that are only slightly larger than a packaged IC yet reduce your design challenge to absolute simplicity. The product line includes transmitters, receivers, and transceivers for 433- and 916-MHz operation and is certified for use in different regions of the world, depending on the model. For example, the company's $15.20 (1000) 3V RX6000 amplifier-sequenced-hybrid (ASH) receiver supports data rates to 115.2 kbps using an architecture with a wide-dynamic-range logarithmic detector, a data slicer, digital AGC, two stages of SAW filtering for out-of-band rejection, and stability with almost any antenna impedance (Figure 3). This stability factor is especially important in many RF-link applications, because the actual impedance of an antenna changes as its orientation and proximity to nearby conducting surfaces vary. The ASH-receiver design maximizes the channel-capture effect, whereby the strongest signal in the RF field dominates and fully captures the receiver. Meanwhile, the receiver ignores undesirable, weaker signals, which thereby do not degrade demodulation BER performance. (Although these characteristics may seem Darwinian-reflecting the laws of the RF jungle-they make for a good link!) The material in Reference 1 provides an informative discussion of the unique ASH architecture and its features as well as the many critical design and application issues beyond the vendor's parts. You can soon expect a full-duplex transceiver IC, which operates from 220 to 928 MHz, from Philsar Electronics. This multipurpose RF device in a 32-pin SSOP supports data rates to 10 kbps and includes a PLL, VCO, and crystal oscillator, among other key functions. It requires approximately 10 noncritical external passive components and uses an active-filter tuning design for maximum performance. The 3V IC requires 2.5 mA in receiving mode (1 μA in standby) and 6 mA in transmitting mode and produces an RF-output level of -12 dBm with -115-dBm sensitivity at 1k sample/sec. Moving to the 2.4-GHz ISM band, National Semiconductor has the LMX3162 transceiver, which gives you an entry point for home and small-office LANs (Figure 4). The receiver within has -93-dBm RF sensitivity and RSSI sensitivity to -100 dBm. An 85-db-gain IF strip follows this front end; the front end's system-noise figure is 6.5 dB. You can operate this 48-pin IC from an unregulated 3 to 5.5V supply. Within the $5.60 (1000) single-conversion transceiver are a 1.3-GHz PLL that both the transmitting and the receiving functions share, a 2.4-GHz frequency doubler, a low-noise amplifier, buffers, a mixer, the associated receiving-channel functions, and the basic transmitting-signal path. Working with a system-integrator partner, RTX Telecom A/S, National Semiconductor also provides you with reference designs that include schematics, layouts, software, and documentation. Also for 2.4 GHz, Digital Wireless has a complete modem with 100-mW output power that comes on a 9-mm-thick housing that measures less than 46X80 cm (Figure 5). The WIT2410 3.3V modem supports data rates to 115 kbps as a frequency-hopping, spread-spectrum unit. Whichever vendors you look at, be sure to assess how complete their ICs are, because completeness, like beauty, is in the eye of the beholder. Now, vendors with devices that are "even more complete" are replacing some RF ICs that manufacturers last year touted as "complete"-something of a contradiction! Completeness really indicates how many and what type of passive and active components you need to add to the IC to finish the design.