Frequency Tripler Circuit Using Phase Interpolation and Summing Network
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Solution Overview
Problem
Existing frequency tripler circuits are not highly effective in suppressing the fundamental component of the input signal, resulting in a significant presence of the fundamental frequency in the output signal, even with moderate rejection using high-quality bandpass filters.
Innovation Solution
A frequency tripler circuit incorporating a phase interpolator to generate a six-phase signal from a four-phase signal, followed by a summing network that combines specific phases to generate a two-phase signal, effectively canceling the fundamental component and enhancing the third harmonic component, utilizing weighted sum circuits and differential pairs to achieve this.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a bandpass filter with moderate quality factor is used to extract the third harmonic component, then the circuit complexity is reduced, but the fundamental component cannot be sufficiently suppressed in the output signal
Solution Approach 1:
The invention divides the frequency tripling function into two separate stages: a nonlinear circuit that generates harmonic components and a summing network that selectively combines them. This segmentation allows each stage to be optimized independently, achieving high fundamental suppression without requiring an overly complex filter circuit.
Solution Approach 2:
The invention merges multiple phase-shifted signals (first, third, and fifth phases) through the summing network to generate the final output. By combining these signals with appropriate phase relationships, the fundamental components cancel each other out while the third harmonic components reinforce each other, achieving effective fundamental suppression without complex filtering.
2Productivity
If a nonlinear circuit with high third harmonic content is used, then the frequency tripling efficiency is improved, but the fundamental component remains considerably stronger than the third harmonic component
Solution Approach 1:
The invention introduces asymmetric phase shifting through the summing network, where different phases (0°, 120°, 240°) are combined in a specific asymmetric pattern. This asymmetric combination causes the fundamental components to cancel out while allowing the third harmonic components to add constructively, thereby improving the harmonic component ratio.
Solution Approach 2:
The invention changes the phase parameter of the input signals by introducing specific phase shifts (0°, 120°, 240°) before combining them. This parameter transformation allows the same nonlinear circuit output to produce different results when summed, effectively suppressing the fundamental component while enhancing the third harmonic.
3Manufacturing precision
If a circuit of very high quality factor is used to suppress the fundamental component, then the fundamental suppression is improved, but the device complexity and quality factor requirements increase significantly
Solution Approach 1:
The invention creates multiple copies of the input signal with different phase shifts (first, third, and fifth phases) and processes them through identical summing network paths. By copying and phase-shifting the signals, the fundamental components cancel out through constructive and destructive interference patterns, achieving high suppression without complex filtering.
Solution Approach 2:
The invention converts the harmful fundamental component into a beneficial cancellation effect. By intentionally introducing phase-shifted copies of the fundamental component and summing them, the fundamental frequencies cancel each other out through destructive interference, turning what was originally a harmful artifact into a useful suppression mechanism.
Data Source
AI summary
An apparatus includes a phase interpolator configured to receive a four-phase signal and output a six-phase signal, and a summing network configured to receive the six-phase signal and output a two-phase signal, wherein: a first phase, a third phase, and a fifth phase of the six-phase signal are summed to generate a second phase of the two-phase signal, while a second phase, a fourth phase, and a sixth phase of the six-phase signal are summed to generate a first phase of the two-phase signal.