Four channels at once for basestation convertor

Texas Instruments has a new four-channel wideband digital down convertor and up convertor that is ideal for radios in 3G wireless base transceiver systems.

Texas Instruments has a new four-channel wideband digital down convertor and up convertor that is ideal for radios in 3G wireless base transceiver systems.

The flexible four-channel device is the first chip that provides both digital down conversion and up conversion functions in a single package.

Aimed mainly at CDMA2000 and W-CDMA basestation systems, the new device also offers superior digital radio performance for other applications such as wireless repeaters, cable modem radios, wireless instrumentation and defence-based digital radio systems.

TI's GC5016 enables wireless infrastructure manufacturers to take advantage of the industry's best performance in digital down and up conversion in a single device.

It offers outstanding 3G performance with 150Msample/s clocking, flexible wideband digital filtering, many input-output interfacing options and very low power dissipation.

"We will be combining down-conversion and up-conversion blocks at even higher levels of integration in future devices", said Brad Evans, Systems Engineer for TI's wireless infrastructure radio products group.

"This will give basestation manufacturers a proven low-cost high-performance option over developing expensive in-house custom ASIC-based radio-chain solutions".

The GC5016 can provide either four channels of digital down conversion, four channels of digital up conversion, or two channels of down conversion and two channels of up conversion simultaneously.

Using a single device for down conversion and up conversion for receive and transmit functions, manufacturers can drive costs down for basestations, macrocell, microcell and picocell basestations as well as wireless repeaters.

This also means that basestation radio engineers need to become familiar with only one device for both down-convertor and up-convertor functions.

Each of the GC5016's four down-convertor or up-convertor channels can be independently configured.

Operating mode, tuning frequency, channel filtering, automatic gain control and input-output options can be programmed over a microprocessor bus.

Channel filtering consists of a six-stage CIC filter and a programmable FIR filter.

The FIR filter provides up to 255 taps for UMTS and CDMA2000 modes.

Spurious-free dynamic range is an industry best at better than -115dBC.

Power dissipation is about 600mW when clocking at 100MHz with four channels configured for UMTS operation.

Together, these features provide performance better than any other 3G digital down-convertor or up-convertor device available today.

Applications requiring wider bandwidth such as cable modem head-end systems, wireless instrumentation and defence/aerospace radio systems can benefit from the GC5016's special double-rate input and output mode enabling effective sample rates to 300Msample/s - the fastest in the industry.

In down-conversion mode, the GC5016 accepts signal data from an A/D convertor such as TI's 12bit 80Msample/s ADS5410.

The GC5016 tunes the desired signal to baseband and then isolates the desired signal by applying pulse-shape filtering.

The isolated signal is then decimated and output for subsequent chip-rate and symbol rate processing.

Further signal processing and demodulation is handled with a programmable DSP chip such as TI's TMS320C6416 DSP.

In up-conversion mode, the GC5016 accepts complex digital signal data from a baseband source.

These signal data are then interpolated, pulse-shape filtered, modulated to a programmed intermediate frequency, and then output to an external D/A convertor such as TI's 14bit 125Msample/s DAC2904.

The GC5016 also supports complex outputs for direct I/Q up conversion and power amplifier digital predistortion linearisation processing.

Limited preliminary samples of the GC5016 wideband digital down convertor and up convertor are available today from TI at a price of $65 per 1000 units.

Production devices will be widely available in the third quarter of 2003.

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