FIR Harmonic-Cancellation Sine-Wave Generator With Programmable Notches
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Solution Overview
Problem
Existing sine-wave generators face challenges in achieving high-linearity and area-efficiency while effectively suppressing harmonics, with traditional methods like high-order filters requiring complex circuitry and large hardware overhead.
Innovation Solution
A mixed-signal finite impulse response (FIR) filter-based harmonic cancellation technique is employed to generate sine-waves by producing delayed versions of a square-wave, scaling, and summing them to suppress harmonics, utilizing a programmable FIR filter with adjustable notches to eliminate odd and even harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If high-order low-pass or band-pass filters are used for sine-wave generation, then harmonic attenuation is improved, but device complexity increases
Solution Approach 1:
The patent segments the harmonic cancellation task into multiple parallel FIR filter banks, each handling specific harmonic frequencies. Instead of using a single complex high-order filter, the system divides frequency spectrum management into discrete filter modules that can be independently configured and implemented, reducing overall system complexity while maintaining effective harmonic attenuation.
Solution Approach 2:
The patent introduces FIR filters as intermediary components between the square wave generator and the output. These filters act as mediators that selectively cancel harmonics through zero-placement in the z-plane, providing a middle ground between simple filtering and complex high-order filtering by using digital signal processing techniques to achieve harmonic suppression with reduced complexity.
2Manufacturing precision
If look-up table with high-resolution DAC is used, then sine-wave linearity is improved, but hardware overhead increases
Solution Approach 1:
The patent replaces the mechanical/memory-intensive look-up table approach with a digital filter-based system. Instead of storing precise sine wave values in memory and using high-resolution DACs, the system uses FIR filters with programmable coefficients to generate sine waves mathematically, substituting hardware memory and high-resolution conversion with digital signal processing that achieves similar linearity with reduced hardware overhead.
Solution Approach 2:
The patent changes the fundamental parameter of sine-wave generation from memory-based value retrieval to filter-based mathematical synthesis. By using programmable FIR filter coefficients and zero-placement techniques, the system achieves high linearity through parameter optimization rather than hardware precision, allowing flexible adjustment of linearity characteristics without increasing hardware overhead.
3Object-generated harmful factors
If high-order filters are used for harmonic suppression, then harmonic attenuation is improved, but manufacturing stability becomes difficult
Solution Approach 1:
The patent introduces dynamic programmability to the FIR filter system, allowing filter coefficients and zero-locations to be adjusted after manufacturing. This dynamic capability enables the system to adapt to manufacturing variations and maintain stable performance without requiring extremely tight manufacturing tolerances, as the filters can be programmed to compensate for deviations from ideal characteristics.
Solution Approach 2:
The patent implements self-adjustment mechanisms where the FIR filter system can automatically optimize its performance characteristics. The programmable nature of the filters allows them to self-correct for manufacturing imperfections by adjusting their transfer functions, reducing the stringency of manufacturing requirements while maintaining effective harmonic suppression.
Data Source
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AI summary
Devices and methods may include receiving a square wave having a frequency at an input of a harmonic-cancellation (HC) sine-wave generator; receiving a clock signal having a clock frequency at a clock input of the HC sine-wave generator; generating one or more delayed square waves based on the received square wave and the clock signal using one or more delay components of the HC sine-wave generator; and amplitude-scaling the square wave and the one or more delayed square waves using a plurality of taps of the HC sine-wave generator to produce a plurality of amplitude-scaled square waves. The method may include adding the plurality of amplitude-scaled square waves using summing circuitry of the HC sine-wave generator to produce a sine wave having tone at the frequency with suppressed signal strength at selected harmonics of the frequency of the square wave at an output terminal of the HC sine-wave generator.