MAX9947: Single-chip AISG-compliant transceiver is 100x smaller than discrete designs

Third-generation (3G) wireless networks were developed to provide the high-speed data services required by data-intensive smartphone applications. Yet, deployment of this infrastructure has been costly, and coverage has been notably inadequate in some areas.

Addressing both of these concerns, the Antenna Interface Standards Group (AISG) developed an interface protocol to enable intelligent antenna systems. The AISG specification allows digital remote control and monitoring of wireless infrastructure to dynamically optimize the network based on changing coverage requirements.

This open standard has quickly been adopted by telecommunications companies because it frees them from proprietary solutions while protecting their infrastructural investments. In turn, base-station and antenna manufacturers have benefited from a standardized technology roadmap, which has increased efficiency in product planning.

AISG transceivers can be implemented discretely using any number of components and methods. They might use active filters or passive filters, different methods for OOK modulation and demodulation, logic for bus arbitration, amplifiers, and, in some cases, ADCs. Since each transceiver implementation can use a different architecture to achieve AISG compliance, antenna and base-station OEMs must maintain multiple board layouts to accommodate various transceiver designs.

The fact that a transceiver sits in the base station where there will be a microcontroller or processor and the tower, which is not likely to have either, further complicates matters. Any communication between the two sites requires bus arbitration, necessitating a device that can operate under the control of a microcontroller or act independently. Because of this requirement, system designers have had to use different transceiver modules for base-station and tower-mounted equipment.

The MAX9947 is the only single-chip AISG-compliant transceiver on the market. The device integrates a transmitter, receiver, and active filters to save designers from the hassle and expense of working with discrete solutions. The MAX9947, thus, drastically reduces the time needed to implement the AISG protocol.

The transmitter includes an OOK modulator, a bandpass filter that is compliant with the AISG spectrum-emission profile, and an output amplifier. The receiver includes a bandpass filter that operates around the 2.176MHz center frequency with a narrow 200kHz bandwidth; it also includes an OOK demodulator and a comparator for reconstructing the digital signal. An autodirection output is provided to facilitate RS-485 bus arbitration in tower-mounted equipment without requiring a microcontroller.