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Synthesizer ICs tout 1GSps operation

Posted: 07 Dec 2006 ?? ?Print Version ?Bookmark and Share

Keywords:DAC? Analog Devices? ADI? direct digital synthesizer IC? direct digital synthesizer chip?

Analog Devices Inc. (ADI) announced that it has more than doubled the clock speed of the industry's fastest direct digital synthesizer (DDS) ICs that use 14-bit DACs.

As such, the AD9910 and AD9957, for frequency agile applications such as wireless base stations, military and commercial radar, test equipment, and secure communications systems, are touted as the first DDS devices to achieve speeds of 1GSps, while lowering power consumption by more than 50 percent.

The 1GSps operating speed and the 14bit DAC in the AD9910 DDS, which is suited to communications and instrumentation applications, facilitates an improvement in dynamic performance for output frequencies to 400MHz. The second device, the AD9957 DDS modulator (or quadrature digital upconverter, QDUC) simplifies data transmission for wired and wireless systems by offering real outputs up to intermediate frequencies of 400MHz.

"Increasing clock speeds to 1GSps on high-resolution DDS ICs allows our customers to generate higher output frequencies with improved dynamic performance," said Kevin Kattmann, product line director, High Speed Signal Processing Group, ADI. "The new DDS products represent a significant step forward, providing 8 to 12dB better spurious free dynamic range when compared to previous generations."

The AD9910 and AD9957 are the company's first devices developed on a new, low-power DDS core that consumes only one-tenth the power of previous generation cores. It's based on technology licensed from Pentomics, a California-based company that specializes in circuit design and signal processing for digital communications. Featuring a 16bit parallel port with update rates to 250MHz, the AD9910 digital synthesizer allows designers to update a 32bit frequency tuning word every 8ns. Thus it's suited for high-speed waveform generators, frequency hopping synthesizers, secure communications, and a variety of radar and scanning systems.

In addition, the AD9910 offers a 70 percent reduction in power dissipation when compared to existing solutions, consuming just 700mW at full operating speed. The enhanced on-chip reference clock multiplier reduces system cost by generating the internal 1GSps clock from a low frequency external source. Additional features added to the DDS core include a secondary accumulator for linear sweeping of frequency, phase or amplitude; RAM for user-defined non-linear sweeping; and ease of synchronization for multiple DDS devices in the same system. The AD9910 may be combined with the company's ADCMP60x comparators or AD951x clock dividers to generate programmable high-speed, low-jitter clock solutions.

The AD9957 QDUC integrates a high-speed DDS, a 14bit DAC, clock multiplier circuitry and digital filters on a single chip, enabling uncomplicated, cost-effective baseband up-conversion for data transmission in wired or wireless communications infrastructure systems, including WiMAX applications. The QDUC achieves greater than 50 percent power reduction over existing QDUCs.

The chip receives an interleaved I/Q data stream, interpolates it, and synthesizes the desired signal for transmission. The 1GSps numerically controlled oscillator and DAC allow the AD9957 to provide direct outputs up to 400MHz, thus eliminating some up-conversion stages and reducing filter requirements.

The chip's low-noise, on-chip reference clock multiplier allows the use of low-cost, low-frequency sources for the system clock while still delivering excellent dynamic performance. The AD9957 also supports test vectors and amplitude ramping capability. The user interface to the control functions of the AD9957 includes a serial port easily configured to work with ADI's Blackfin processors.

The AD9910 and AD9957, in 100-lead quad flat packs, are sampling now with full-production quantities available in February. The AD9910 is priced at $35 per unit, and the AD9957 is available for $21.

- Vince Biancomano

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