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A sequenced-gain receiver is shown in Figure 1 111. Operation of the receiver can be understood from the timing diagram of Figure 2. The first RF amplifier is active until signal emerges from the SAW delay line when it is powered down and the second RF amplifier is powered up. Some time later, the cycle is repeated.With adequate pulse repetition frequency (PRF), the modulated data can be recovered completely. If the duty factor is small, the average power supply current is low, since the baseband circuits after the detector require much less current than the RF section. This efficiency comes at the expense of RI? sensitivity, due to noise aliasing caused by switchingthe amplifiers. Performance is intermediate to super-regenerative and superheterodyne receivers.Configured for lkbaud data, sensitivity exceeds -100dBm. The absence of oscillators obviates receiver radiation. Inclusion of the SAW coupled resonator bandpass filter at the input protects the high gain first amplifier from clipping on unwanted signals (Figure 3). The SAW delay line also provides selectivity, which limits the effects of noise aliasing of the first amplifier. The result is a selective, sensitive, RF quiet, low cost, fixed tuned data receiver in a small package [23.The chip contains the switched RF amplifiers, Ah4 detector, baseband lowpass filter and amplifier, comparator, data output driver, and pulse generator. Avariety of end applications for the resulting References 111 "Sequential Amplifier", U.S. Patent # 5,357,206. RFM

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