Polyphase Super Harmonic Filter for IC Harmonic Suppression
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Solution Overview
Problem
The integration of filters in wireless transmitters and receivers is hindered by the need for large capacitors and inductors, which prevents effective filtering of unwanted frequency components, particularly harmonics, within integrated circuits, leading to attenuation of fundamental frequencies and insufficient harmonic suppression.
Innovation Solution
A super harmonic filter comprising a phase shifter and a series of polyphase filter networks that generate in-phase and quadrature-phase signals, allowing for the filtering of specific frequency components, including odd harmonics, by configuring each polyphase filter network to target specific harmonics and using signal reversals to act as stop-band filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional filters are integrated into IC, then miniaturization and functional integration are improved, but filtering performance deteriorates due to insufficient harmonic suppression
Solution Approach 1:
The filter is divided into multiple cascaded stages, each targeting specific harmonic frequencies. The first stage filters odd harmonics using a series capacitor and shunt inductor configuration, while the second stage filters even harmonics and the fundamental frequency. This segmentation allows each stage to specialize in removing particular frequency components, achieving comprehensive harmonic suppression in a compact IC-friendly design.
Solution Approach 2:
The patent employs different capacitor and inductor values in each filter stage to target specific frequency ranges. The first stage uses L1 and C1 values optimized for odd harmonic rejection, while the second stage uses L2 and C2 values optimized for even harmonic and fundamental frequency rejection. This parameter optimization enables effective harmonic filtering despite the compact IC implementation constraints.
2Reliability
If filter order is increased to improve harmonic suppression, then filtering performance is improved, but circuit complexity and power consumption increase
Solution Approach 1:
Rather than using a single high-order filter section, the patent segments the filtering function into two distinct first-order or second-order stages. Each stage handles specific harmonic components (odd vs. even), achieving high-order equivalent filtering performance through cascaded simple sections. This reduces the complexity of individual sections while maintaining overall high harmonic suppression capability.
Solution Approach 2:
The patent converts the typically harmful harmonic frequencies into beneficial design parameters by creating resonant circuits at specific harmonic frequencies. The inductors and capacitors are tuned to create anti-resonance at odd harmonics in the first stage and at even harmonics in the second stage, effectively suppressing these frequencies through resonant cancellation rather than brute-force high-order filtering.
3Reliability
If traditional filtering methods are used, then harmonic suppression is improved, but fundamental frequency attenuation increases
Solution Approach 1:
The patent applies different filtering characteristics to different frequency ranges. The first filter stage is locally optimized for odd harmonic suppression with minimal impact on the fundamental frequency, while the second stage is locally optimized for even harmonic and fundamental frequency control. This localized optimization ensures that each stage performs its specific function without unnecessarily attenuating frequencies outside its target range.
Solution Approach 2:
By carefully selecting L1, C1, L2, and C2 values, the patent creates filter responses that sharply reject specific harmonic frequencies while maintaining passband characteristics for the fundamental frequency. The parameter optimization ensures that the cutoff frequencies and resonant frequencies are positioned to maximize harmonic rejection while minimizing fundamental frequency attenuation, achieving high Q-factor selective filtering.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The super harmonic filter effectively removes unwanted frequency components, including odd harmonics, while minimizing the attenuation of fundamental frequencies, enabling the integration of wireless transmitters and receivers as single ICs and improving ergonomic design without increasing power consumption or circuit complexity.
Implementation Method 1
a phase shifter for generating an in-phase signal and a quadrature-phase signal according to the input signal
Implementation Method 2
each polyphase filter network being for filtering a corresponding one of the N frequency components from the input signal
Data Source
AI summary
A harmonic filter for filtering a plurality of frequency components from an input signal comprises a phase shifter for generating an in-phase signal and a quadrature-phase signal according to the input signal; and a plurality of polyphase filter networks coupled in series. The first polyphase filter network in the series is coupled to the phase shifter for receiving the in-phase and quadrature-phase signals. Each polyphase filter network is for filtering a corresponding one of the frequency components from the input signal.