FIR Filter with Integrated Gain and Compression
Quickfilter Technologies Inc. has developed an audio applications-specific FIR (Finite Impulse Response) filter chip that will enable audio equipment designers to achieve higher audio quality at a low cost. The QF1Da512 SavFIRe™ (Simple and versatile FIR engine) is believed to be the industry's first audio applications-specific FIR filter to contain an integrated gain and compressor stage that directly addresses the issue of dynamic range loss in audio equalization applications.
The Digital Gain and Compression (DGC) feature in the QF1Da512 SavFIRe — also known as the Audio-SavFIRe — combines both gain and compression in one operational block. The compression is performed sample by sample with an instant attack and release. The slope of the compression curve is adjusted as the gain increases. The gain block is configured to provide up to 24 dB of positive digital gain. This combines to yield the maximum in dynamic range without distortion. As a result, the QF1Da512 SavFIRe allows manufacturers to use lower-cost speakers while providing audio quality equivalent to high-end speakers.
"When the original QF1D512 SavFIRe™ chip was announced in September 2006, it was embraced by audio equipment manufacturers as a solution for their audio quality problems," said Tony Valentino, Quickfilter Technologies Chief Operating Officer. "However, one of the limitations was the loss of gain through the filter, which forced designers to add gain stages after the filter. Adding these gain stages not only impacted overall cost, but the gain stages had to be managed in order to prevent distortion and, therefore, increased design complexity. With the Audio-SavFIRe, additional gain stages and the management of gain are now done on-chip via the compression block, thereby not only improving performance, but also reducing complexity and cost."
The original QF1D512 SavFIRe chip continues to be well-suited for various industrial monitoring applications, such as vibration sensing, flow management and leak detection, medical patient monitoring, seismic and sonar diagnostics as well as those audio applications not requiring additional gain stages," Valentino continued.
The QF1Da512 SavFIRe supports up to 512 taps with 32 bit coefficients and user-defined data word width from 12 to 24 bits providing the application with superior audio quality. The QF1Da512 SavFIRe processes the equivalent of 50 million MAC instructions per second and supports sample rates from 1 Hz to 500 kHz, placing it in the class of mid-range digital signal processors and exceeding the performance of most audio processors. When used with an audio processor, the QF1Da512 SavFIRe enables existing sound enhancement or graphic equalization to be more pronounced.
The device also provides a "duplicate" function, which allows the user to copy and insert channel data into successive clock cycles, thereby easing the design of audio crossovers.
The QF1Da512 SavFIRe is now available in sample quantities with full production release scheduled for the mid first quarter of 2009. The device is packaged in a 3 × 3 mm QFN and consumes 2.8 mW of power providing the user with a clear price-performance advantage. Its associated development kit — QF1Da512-DK — will be available at the end of February 2009 for purchase at DigiKey and Mouser.
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