Rockwell Scientific Introduces High Performance Dual Track and Hold Chip for Ultra-wideband Data Acquisition

Device dramatically increases ADC bandwidth

THOUSAND OAKS, CA, DECEMBER 17, 2001 — Rockwell Scientific Company LLC (RSC), a premier developer of high speed mixed signal circuits for commercial and defense applications, has introduced a 10 GHz bandwidth 1 GS/s dual track and hold (T/H) circuit for ultra-wideband data acquisition. Designed for direct sampling of multi-GHz signals, the RTH020 circuit features unprecedented bandwidth and aperture jitter performance.

The bandwidth of the RTH020, 9 GHz for 0.5 Vpp inputs and over 10 GHz for small signals, is more than three times that of any reported T/H and allows sampling of 1 GHz signals with 10 bit precision. The master-slave configuration of this dual T/H device holds the output signal for nearly an entire clock cycle, significantly easing the bandwidth requirements for subsequent circuitry, such as ADCs. With well under 1 mV noise and less than 100 fs aperture jitter, the RTH020 achieves a 56 dB signal-to-noise ratio and a-63 dB total harmonic distortion for a 500 MHz input signal at a full-scale power of 1 Vpp.

Direct conversion of multi-GHz carrier signals becomes a reality with the RTH020. Used in conjunction with existing ADCs, the T/H eliminates mixer and filter functions, lowering system cost by bringing the ADC closer to the antenna. "This device turns a moderate bandwidth commercial ADC into a 10-GHz bandwidth ADC," said Paul van der Wagt, Senior Scientist in RSC's High Speed Mixed Signal ICs department.

The RTH020's differential-in, differential-out dual T/H cascades two single T/H circuits, each of which is optimized for a separate function. The first T/H determines the dynamic performance, such as bandwidth, distortion, and jitter, of the entire part in sampled mode. The second T/H is optimized for low gain loss, distortion, and noise. Both T/H circuits used Schottky diode sampling bridges to yield high linearity and speed at the same time.

RTH020 packaged measurements show a small-signal bandwidth (< 0.1 Vpp input level) extending beyond 10 GHz. Large signal bandwidths are 9 and 6 GHz for 0.5 Vpp and 1 Vpp inputs, respectively. Says van der Wagt: "To detect weak signals, the small signal bandwidth is most relevant. Overall, the bandwidths of the RTH020 represent a 3x to 4x improvement over competing parts for comparable input levels." The part is designed for 10 bit distortion performance over the DC to 1 GHz band. For higher frequencies, performance gradually decreases to over 7.2 bits at 3 GHz (0.5 Vpp) and 6 bits at 5 GHz (0.25 Vpp), before showing gain roll-off.

An evaluation kit, EVRTH020, is available for testing packaged RTH020 performance. Measurements on the evaluation boards show the same performance as on-wafer die measurements. Information about this and other high-speed data conversion products, including ADCs, DACs, and DDSs, can be found at http://www.rockwellscientific.com/highspeed/

Rockwell Scientific is an independent, privately owned high technology enterprise with unique technical strengths in electronics, imaging, optics, materials, and information science. Its broad range of initiatives includes contract research and development as well as commercialization of technologies through licensing, development and sale of high value products, and spin offs.

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