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At the recent IEEE International Solid State Circuits Conference (ISSCC'07) in San Francisco, Calif., NXP Semiconductors took a major step forward in broadband communications. Using a cascaded Sigma-Delta (Σ-Δ) modulator with continuous-time (CT) quadrature loop filters, NXP researchers unwrapped a broadband analog-to-digital converter (ADC) for digitizing all FM radio channels simultaneously, rendering a 100 times increase in performance. According to the developers, this cascaded Σ-Δ converter will enable a wide range of in-dash car radio functions and broadband wireless applications, such as software-defined radio (SDR).

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According to the NXP paper, the Σ-Δ ADC has demonstrated specs like dynamic range of 77 dB and 20 MHz bandwidth at an IF of 10.5 MHz. Plus, it offers inherent anti-aliasing filtering, and does not suffer from dc offset or 1/f noise, that are outside the near zero-IF (NZIF) signal band.

As per the NXP release, the Σ-Δ converter eliminates the need for radios to individually filter each FM radio channel. This enables every passenger in the vehicle to listen to a different radio station or source simultaneously with a single in-dash car radio using wired or wireless headsets. The converter also supports applications like frequency diversity, in which the strongest FM signal is detected and selected while broadcasting the chosen channel and radio datastreaming (RDS) to supply the consumers with more information related to their programming.

“NXP is committed to providing consumers with new and exciting ways to enjoy media anytime, anywhere, including in their cars,” said Leo Warmerdam, senior director, research, NXP Semiconductors. “Our ground-breaking research program focused on broadband Σ-Δ converter architectures that will reshape what consumers expect from their car audio experiences and holds the promise of revolutionizing many other wireless applications.”

Implemented in 90 nm CMOS technology, the Σ-Δ ADC converter is based on a CT quadrature cascaded architecture, exploiting the lower oversampling of the converter to boost the signal bandwidth to unprecedented frequencies. NXP researchers expect that this innovative architecture will produce significant performance enhancements in the coming years. When applied to car radio, this converter will enable the complete 20 MHz FM radio band to be digitalized accessing all 101 U.S. radio channels (100 in Europe) simultaneously.

Meanwhile, the developers are planning to push the process technology to 65 nm CMOS later this year. Total power consumption is given at 56 mW, and the chip area is 0.5 mm².

The Σ-Δ converter is an advanced technology development that will become available in future products, NXP said.

For more information, visit www.nxp.com.