ML2721

PRELIMINARY ML2721 Low IF Digital Cordless Transceiver GENERAL DESCRIPTION The ML2721 can be used as a single chip digital cordless telephone transceiver or general purpose Frequency Shift Keying (FSK) radio transceiver. It is designed to work in the 902 to 928MHz ISM band under FCC Part 15 regulations. The device integrates all the frequency generation, receive and transmit functions for data rates up to 1.5Mbps. A complete radio only requires the addition of an antenna switch. Micro Linear’s ML2751 is an integrated 100mW power amplifier and receive LNA with transmit/receive PIN diode drivers, and it can be used with the ML2721 for extended range capability. The ML2721 contains a proprietary low IF receiver with all channel selectivity. An image reject mixer brings the 915MHz RF signal down to a low IF frequency of 1.024MHz. Then all IF filtering, IF gain, and demodulation is performed at 1.024MHz. This provides all the benefits of direct conversion to baseband and minimizes the need for RF filtering. Also, the ML2721 can operate with either a low cost LC filter or a SAW filter. A single 1.83GHz synthesizer is used for both the receiver LO and the transmitter. The ML2721 transmitter modulates the VCO with filtered data, and a driver amplifier provides typically 0dBm at 915MHz. The VCO and PLL incorporate the resonator, the active devices, and the tuning circuitry for a completely integrated function. An internal post detection filter and data slicer are also included. The ML...