Edge-Rotator Clock Generation for Non-Harmonic RF Frequency Planning
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Solution Overview
Problem
In multi-radio combo-chip products, RF oscillators face challenges in avoiding harmonic interference, leading to complex frequency planning and increased area and current consumption due to the need for good isolation and suppression of side-band spurs in analog circuits.
Innovation Solution
A digital clock generator design utilizing an edge rotator with multiple phases and an autonomous calibration process to create a non-harmonic relationship between input and output clocks through frequency translation, employing a delay-locked loop or all-digital phase-locked loop for flexible frequency planning and spur avoidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional analog blocks such as frequency divider(s) and mixer(s) are employed to generate non-harmonic clocks, then the frequency offset ratio is limited to a rational number, but the circuit complexity and area consumption increase due to the need for LC-tank and side-band spur suppression
Solution Approach 1:
The patent replaces the conventional analog mixing approach with a digital domain implementation. The edge rotator operates in the digital domain to generate non-harmonic clock signals, eliminating the need for analog mixers, LC-tanks, and side-band spur suppression circuits. This substitution of digital for analog mechanisms resolves the contradiction by providing unlimited frequency ratio flexibility while reducing circuit complexity.
Solution Approach 2:
The patent changes the fundamental operating parameters from analog continuous signals to digital discrete edge signals. By operating in the digital domain with programmable edge rotation, the system achieves continuous frequency ratio adjustment capability without the structural complexity of analog frequency synthesis circuits.
2Adaptability or versatility
If analog approach with frequency divider(s) and mixer(s) is used to achieve frequency translation, then the frequency ratio is constrained to rational numbers, but additional analog blocks are required which consume large area and current
Solution Approach 1:
The patent substitutes digital edge rotation mechanisms for analog mixing operations. The digital edge rotator consumes significantly less current than analog mixers and LC-tank circuits while providing superior frequency planning flexibility through programmable operation.
Solution Approach 2:
The patent extracts and removes the unnecessary analog blocks (mixers, LC-tanks, side-band suppression circuits) from the frequency translation process. By keeping only the essential digital edge rotation function, the system achieves the desired frequency translation with minimal area and current consumption.
3Adaptability or versatility
If multiple RF oscillators are integrated in multi-radio combo-chip products, then more functions are supported, but harmonic interference and injection pulling occur between oscillators
Solution Approach 1:
The patent replaces analog oscillator-based frequency generation with digital edge rotation-based frequency synthesis. This substitution eliminates the harmonic interference and injection pulling problems inherent in analog LC-tank oscillators, enabling clean frequency generation for multiple radio functions without mutual interference.
Data Source
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AI summary
One clock generator (100, 200, 400, 600) includes an oscillator block (102, 202, 402, 602), a delay circuit (104, 204, 404, 604), and an output block (106, 206, 406, 606). The oscillator block (102, 202, 402, 602) provides a first clock of multiple phases. The delay circuit (104, 204, 404, 604) delays at least one of said multiple phases of said first clock to generate a second clock of multiple phases. The output block (106, 206, 406, 606) generates a third clock by selecting signals from said multiple phases of said second clock, wherein said third clock has non-harmonic relationship with said first clock.