Single Chip Receiver for LPD Apps from Lexiwave

By: http://www.lexiwave.com/datasheet/LW103%20datasheet%20v08.pdf
(Top News, 8 Sep 2006)

The LW103 is a regenerative amplitude-shift-keying (ASK) modulation (or On-Off keying, OOK) single chip receiver. It is designed to operate for low power device (LPD) applications. Industry commonly uses 315 MHz and 433 MHz for US and European market respectively. By changing a few external components, energy saving LW103 can support both bands at low cost.

The heart of the chip is an oscillator operating in super-regenerative mode. The demodulated baseband signal is filtered by a low pass filter. The filtered signal is then amplified by an operational amplifier. Since on-off eying is used, the amplifier signal will be compared with voltage reference at a data comparator. It will then recover the transmitted “0” and “1” sequence. A bandgap reference is implemented inside the chip for stable operating conditions over temperature and supply voltage. In addition, our patent pending approach allows the chip operate normally from 2.5V to 3.3V and overcomes component variations. The chip is thus very suitable for mass production applications where no tight tolerance components are required.An internal Low Noise Amplifier (LNA), as shown in application circuit A, can be used to achieve higher sensitivity and isolation to meet emission requirements. The signal isolation offered by the LNA also minimizes receiving sensitivity degradation when the oscillation frequency of the super-regenerative oscillator will be affected by a close object (hand-effect). In normal-sensitivity applications where hand-effect would not occur, the loop antenna (application circuit B) can be used as a resonator in the super-regenerative oscillator to save external components and current consumption as the LNA is not needed. Similarly, for applications that require only medium sensitivity, application circuit C would be suitable to eliminate the hand-effect with low current consumption.

Click here for more information