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TR1004 Datasheet(PDF) 4 Page - Murata Manufacturing Co., Ltd. |
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TR1004 Datasheet(HTML) 4 Page - Murata Manufacturing Co., Ltd. |
4 / 12 page www.RFM.com E-mail: info@rfm.com Page 4 of 12 ©2008 by RF Monolithics, Inc. TR1004 - 4/4/08 ASH Receiver Block Diagram & Timing Cycle Antenna Pulse Generator SAW Delay Line SAW Filter RFA1 RFA2 Data Out Detector & Low-Pass Filter RF Data Pulse P1 P2 RFA1 Out RF Input P1 Delay Line Out P2 t PW2 t PW 1 t PRI t PRC Figure 1 ASH Transceiver Theory of Operation Introduction RFM’s amplifier-sequenced hybrid (ASH) transceiver is specifically designed for short-range wireless data communication applications. The transceiver provides robust operation, very small size, low power consumption and low implementation cost. All critical RF functions are contained in the hybrid, simplifying and speeding design-in. The ASH transceiver can be readily configured to support a wide range of data rates and protocol requirements. The transceiver features excellent suppression of transmitter harmonics and virtually no RF emissions when receiving, making it easy to certify to short- range (unlicensed) radio regulations. Amplifier-Sequenced Receiver Operation The ASH transceiver’s unique feature set is made possible by its system architecture. The heart of the transceiver is the amplifier- sequenced receiver section, which provides more than 100 dB of stable RF and detector gain without any special shielding or decoupling provisions. Stability is achieved by distributing the total RF gain over time. This is in contrast to a superheterodyne receiver, which achieves stability by distributing total RF gain over multiple frequencies. Figure 1 shows the basic block diagram and timing cycle for an amplifier-sequenced receiver. Note that the bias to RF amplifiers RFA1 and RFA2 are independently controlled by a pulse generator, and that the two amplifiers are coupled by a surface acoustic wave (SAW) delay line, which has a typical delay of 0.5 µs. An incoming RF signal is first filtered by a narrow-band SAW filter, and is then applied to RFA1. The pulse generator turns RFA1 ON for 0.5 µs. The amplified signal from RFA1 emerges from the SAW delay line at the input to RFA2. RFA1 is now switched OFF and RFA2 is switched ON for 0.55 µs, amplifying the RF signal further. The ON time for RFA2 is usually set at 1.1 times the ON time for RFA1, as the filtering effect of the SAW delay line stretches the signal pulse from RFA1 somewhat. As shown in the timing diagram, RFA1 and RFA2 are never on at the same time, assuring excellent receiver stability. Note that the narrow-band SAW filter eliminates sampling sideband responses outside of the receiver passband, and the SAW filter and delay line act together to provide very high receiver ultimate rejection. Amplifier-sequenced receiver operation has several interesting characteristics that can be exploited in system design. The RF amplifiers in an amplifier-sequenced receiver can be turned on and off almost instantly, allowing for very quick power-down (sleep) and wake-up times. Also, both RF amplifiers can be off between ON sequences to trade-off receiver noise figure for lower average current consumption. The effect on noise figure can be modeled as if RFA1 is on continuously, with an attenuator placed in front of it with a loss equivalent to 10*log10(RFA1 duty factor), where the duty factor is the average amount of time RFA1 is ON (up to 50%). |
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