Driven by high levels of integration in both the transmit and receive functions, the POLARIS transceiver significantly reduces the number of components required to implement a complete GSM/GPRS radio. All VCOs, associated loop filters and many of the power supply bypass capacitors are integrated on silicon, reducing the complete radio component count to fewer than 20 devices.
The POLARIS transceiver includes a commercially available fractional-N-based digital modulator, eliminating the I/Q modulator, phase detector, mixer and loop filters implemented in translational-loop transmitters. This direct digital modulator architecture enables outstanding spectral performance at a fraction of the power consumption of translational-loop transmitters.
The POLARIS transceiver uses a very low intermediate frequency (VLIF) architecture. VLIF enables the elimination of IF SAW filters, thereby contributing to the reduction in overall component count.
To ensure compatibility to all major baseband products, the receiver is designed to output a fully filtered DC signal eliminating any dependence on filtering within the baseband. Programmable analog I/Q baseband inputs and outputs are provided to support historic radio-to-baseband interfaces. Selectable digital baseband interfaces are also provided on both receive and transmit paths, enabling direct interface to emerging digital baseband products.
The POLARIS transceiver exceeds all European Telecommunications Standards Institute (ETSI) specification requirements and features enhanced receiver sensitivity and the ability to handle EDGE modulated signals.
The POLARIS transceiver consists of the following: RF2708, a SiGe BiCMOS receiver with three LNAs, polyphase downconverting mixer, bandpass filter and DC offset correction; RF6001, a CMOS mixed signal processor with digital channel filters, fractional-N frequency synthesizer, digital GMSK modulator and integrated power ramp DAC; RF3133, a GaAs HBT power amplifier module with internal matching components and integrated closed-loop power controller.
RF Micro Devices, Inc., 7628 Thorndike Road, Greensboro, NC 27409; www.rfmd.com