W-CDMA Upconverter Chip for 3G Wireless Basestations
The GC4116 provides four summed digital transmitter channels. The soon-to-be released GC4117 provides separate outputs ideal for beamform applications. Each channel digitally upconverts and filters signals of interest from baseband sources at sample rates up to 106 MSPS. The GC4116 channel output typically drives a D/A converter. A 16-channel basestation transmitter system can be implemented with four GC4116 chips and a single D/A converter.
Sensitive to the thermal constraints of cellular basestations, power dissipation is only 107 milliwatts per channel when clocked at 70 MHz and configured for GSM.
Each GC4116 transmitter channel features a digital resampler, filter channel, digital mixer, and digital oscillator. The digital resampler function permits input sample rates to be precisely specified independent of the clock rate. This simplifies the design of multiple air interface standard basestations. In addition to providing four narrowband channels, the GC4116 can also generate two wideband 5 MHz bandwidth channels for 3G wireless systems.
The GC4116's channel performance is outstanding and provides 115 dB of spurious free dynamic range. The GC4116 filter chain consists of two FIR filters followed by a five-stage CIC filter. The overall interpolation range can be set from 16 to 5,792. Output data is parallel in format and can drive most D/A chips.
The GC4116's configuration parameters are programmed through an 8-bit microprocessor interface. Built-in circuitry permits synchronization of multiple GC4116 chips. The GC4116 operates from a 2.5-volt core, 3.3-volt I/O supply. The chip is housed in a space-saving 160 ball plastic BGA.