LONDON Analog Devices' U.K.design centre has developed a single-chip radio transceiver for the EDGE (Enhanced Data Rates for GSM Evolution) cellular standard that combines all the radio and power management functions needed.
The company's Kent Design Centre in West Malling developed the technology which is the basis of the Othello chipset. The latest device, the Othello-E transceiver, integrates virtually all the necessary components, including voltage-controlled oscillators (VCOs), PLL loop filters and power management, for a complete quad-band EDGE radio design.
According to Stewart Palmen, the product manager responsible for the Othello range of Digital Cellular Transceivers at the Kent design centre, the design of the device cuts the number of external components from 100 to 26. A 6mm x 6mm package enables a complete radio layout in 2.1 sq cm footprint including power amplifier and matching regulators. It uses a low cost 2.5mm x 2mm crystal and can be assembled on a low cost 4-Layer PCB.
The Othello-E transceiver combines all the radio and power management functions including separate low-noise amplifiers (LNA) for all four GSM bands (850, 900, 1800 and 1900 MHz) and a fractional-N PLL synthesizer with integrated VCO and loop filter for local oscillator (LO) generation.
To provide the linearity necessary for the signals that support EDGE data rates, Analog Devices Othello-E radio uses a high-performance logarithmic RF power detector to enable a closed-loop polar modulation transmitter design, which also contributes to better manufacturability and reduced design complexity.
Closed-loop polar modulation is an improvement over open-loop polar designs which require close matching of the transceiver and power amplifier. The Othello-E radio complements Analog Devices' Blackfin SoftFone for EDGE baseband chipset.
An on-chip high-accuracy logarithmic power detector enables the closed-loop polar modulation, and ensures compatibility with power amplifiers from multiple suppliers while maintaining loop stability. In addition, the closed-loop architecture maintains stable, reliable, spec-compliant performance regardless of variations in PA characteristics due to manufacturing process variations, component aging, temperature, or frequency.
On-chip voltage regulators enable direct connection to the battery supply, eliminating the external regulators needed by other transceivers and reducing BOM component count and PC board area.