The single-chip MAX9947 fully integrated AISG-compliant transceiver from Maxim Integrated Products packs a transmitter, receiver, and active filters into a 3- by 3-mm thin quad flat no-lead (TQFN) package that is one-hundredth the size of discrete solutions. Its autodirection output facilitates RS-485 bus arbitration in tower-mounted equipment without requiring a microcontroller. Also, its high integration greatly simplifies the implementation of AISG-compliant basestations and tower-mounted equipment. 

Third-generation (3G) wireless networks were developed to provide the high-speed data services required by data-intensive smart-phone 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. Telecom companies quickly adopted this open standard because it frees them from proprietary solutions while protecting their infrastructural investments. In turn, basestation 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 on-off keying (OOK) modulation and demodulation, logic for bus arbitration, amplifiers, and, in some cases, analog-to-digital converters (ADCs). Since each transceiver implementation can use a different architecture to achieve AISG compliance, antenna and basestation OEMs must maintain multiple board layouts to accommodate various transceiver designs.

The fact that a transceiver sits in the basestation 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 basestation 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 the hassle and expense of working with discrete solutions. As a result, the MAX9947 drastically reduces the time needed to implement the AISG protocol.

The transmitter includes an OOK modulator, a bandpass filter that complies with the AISG spectrum-emission profile, and an output amplifier. The receiver’s bandpass filter operates around the 2.176-MHz center frequency with a narrow 200-kHz 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.

The MAX9947’s receiver boasts a wide input dynamic range of –15 to +5 dBm in 50 Ω. The chip’s resistor-adjustable output power (+7 to +12 dBm) allows compensation for losses in external circuitry and cabling. Also, its output emission profile complies with AISG. And, its autodirection output handles bus arbitration in tower-mounted equipment without requiring a microcontroller.

Furthermore, the MAX9947 supports all AISG data rates of 9.6, 38.4, and 115.2 kbits/s. Its bandpass filter complies with the AISG protocol centered around 2.176 MHz. The chip operates from a 3.0- to 5.5-V supply voltage. And, the MAX9947 is fully specified for operation from –40°C to 85°C.

Prices start at $4.25 in quantities of 1000 and up. An evaluation kit is available to speed design. For more information, go to www.maxim-ic.com/AISG-Transceiver. For more on AISG and the standard, go to www.asig.org.uk.

Maxim Integrated Products