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June 1997

New pager chipset heralds cheaper, smaller radio-based products

In designing the electronics for a new generation of pagers, Cambridge Consultants Ltd (CCL®) has succeeded for the first time in integrating all the functions of a fully-featured wide area pager on to only two ICs: a small bipolar RF chip and a 0.55 CMOS baseband device incorporating CCL's silicon-efficient, low-power XAP RISC microprocessor. This has resulted in economies in size, power consumption and manufacturing cost.

CCL originally made proposals to Ericsson about the use of advanced IC design to reduce costs of manufacture and production test of RF products. As a result the newly-formed Ericsson Wide-Area Pagers Division in Emmen, Holland asked CCL to design a pager that would meet the new ERMES (European Radio Messaging System) international standard, the first to offer frequency agility and through it the ability to 'roam' and provide other user facilities, such as longer messages and group calls.

The design of the electronics to provide the desired results posed an interesting challenge for CCL's engineers. Rather than work along conventional lines, they recreated the architecture from scratch bearing in mind the requirements of the rest of the product.

The project involved close co-operation between Ericsson and CCL, with engineers often working together at CCL's Cambridge Science Park laboratories and at Ericsson's R&D facility in Emmen. The printed circuit board and software for the microprocessor were developed jointly. While Ericsson undertook the user interface design of the numeric pager, which was developed on CCL's proprietary Macintosh-based simulator, CCL developed the innovative icon-based user interface of the alpha numeric version, the system architecture and the custom chips, together with the operating system and device drivers.

• intermediate frequency filtering for channel selectivity
• digital decoding and message decoding
• dual frequency synthesisers
• switched mode power supply, using a single 1.5V cell
• XAP embedded microprocessor
• semi-alphanumeric LCD driver
• DTMF dialler
• all ROM and RAM for the program and data.

Another objective of the electronic design was to remove the need for specialist, expensive RF testgear to be used in production testing. All that is needed with a product based on the CCL design is a simple fixed-amplitude, signal source. The pager is connected to a PC via CCL's built-in serial interface and can be reconfigured through this link to provide all the measurements needed to make the small number of RF adjustments required.

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