Superhetrodyne Receiver Integrates AGC And Image Rejection

Introduced as the market's first 300 MHz to 450 MHz superheterodyne ASK receiver with an integrated AGC and on-chip image rejection, the MAX1473 operates from either a 3V or 5V supply. The receiver has a sensitivity of -114 dBm and a user-selectable center frequency image rejection of greater than 50 dB. Center frequency can be selected at 315MHz, 375MHz, or 433MHz. Also on-board, a one-step AGC circuit drops the LNA gain by 35 dB when the RF input signal is greater than -57 dBm. Other integrated features include a 10.7MHz IF filter with a received signal strength indicator, PLL with VCO, and analog baseband data recovery circuitry. The device draws less than 1.5 µA in shutdown and 5.2 mA in receive mode. Depending on external components, receive rates are up to 100 Kb/s and transition time from shutdown to valid-data out is less than 250 µs. The PLL requires no external components and contains a phase detector, charge pump and loop filter, VCO, asynchronous 32x or 64x clock divider, and a crystal oscillator. With an input frequency of 315 MHz, the quadrature VCO is centered at 304.3 MHz. A reference frequency of 9.5194 MHz or 4.7547 MHz is required for a 10.7 MHz IF. Available in a 28-pin SSOP, prices start at $2.75 each/1,000. MAXIM INTEGRATED PRODUCTS, Sunnyvale, CA. (800) 998-8800.