Polyphase Filter RC-LR Topology for Lower Insertion Loss
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Solution Overview
Problem
Cascaded polyphase filter (PPF) topologies, such as RC-PPF and LR-PPF, suffer from significant insertion loss and gain mismatch issues when used alone, leading to signal amplitude reduction and phase mismatch problems in wide frequency ranges.
Innovation Solution
The solution involves cascading alternating sections of RC-PPF and LR-PPF in an electronic circuit, where RC-PPF sections include resistive and capacitive elements and LR-PPF sections include inductive and resistive elements, to reduce total insertion loss and improve phase-shifted signal representation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If cascaded RC-PPF sections are used to achieve desired bandwidth, then bandwidth is improved, but insertion loss increases significantly
Solution Approach 1:
The patent combines RC-PPF sections and LR-PPF sections in an alternating cascaded configuration. This merging of two different filter topologies allows the system to achieve the bandwidth benefits of cascaded sections while the complementary characteristics of LR sections compensate for the insertion loss accumulated in RC sections, thereby resolving the contradiction between bandwidth expansion and insertion loss reduction.
Solution Approach 2:
The filter circuit uses a composite structure combining two distinct PPF topology types (RC-PPF and LR-PPF) rather than using a single topology throughout. This composite approach leverages the strengths of each topology: RC sections provide bandwidth extension while LR sections provide lower insertion loss characteristics, achieving both wide bandwidth and acceptable loss performance simultaneously.
2Speed
If cascaded RC-PPF sections are used to achieve desired bandwidth, then bandwidth is improved, but gain mismatch increases
Solution Approach 1:
By merging RC-PPF and LR-PPF sections in alternating sequence, the patent creates a balanced cascaded structure where the gain characteristics of LR sections compensate for gain variations introduced by RC sections. This alternating combination maintains better gain matching between in-phase and quadrature outputs across the bandwidth, resolving the contradiction between bandwidth expansion and gain mismatch control.
3Speed
If cascaded LR-PPF sections are used to achieve desired bandwidth, then bandwidth is improved, but insertion loss increases and inductance requirements consume significant area
Solution Approach 1:
Instead of using LR-PPF sections throughout the entire cascaded structure, the patent applies LR topology only in alternating sections with RC-PPF sections. This local application of LR topology provides the necessary bandwidth extension and area efficiency only where needed, while RC sections handle other frequency ranges, optimizing the overall area utilization on the integrated circuit.
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
This approach reduces insertion loss and minimizes gain mismatch between in-phase and quadrature output signals, enhancing the bandwidth and performance of the filter circuit by distributing the -3 dB loss across alternating sections, thereby improving signal processing efficiency.
Implementation Method 1
a first polyphase filter section type including resistive elements and first reactive elements comprising a first type of reactive device
Implementation Method 2
a second polyphase filter type including resistive elements and second reactive elements comprising a different second type of reactive device
Implementation Method 3
a first polyphase filter section type including resistive elements and second polyphase filter type including resistive elements
Data Source
AI summary
Polyphase filters (PPFs) can be used to generate quadrature or other phase-shifted representations of an input signal provided to the PPF. In one approach, a “passive” polyphase filter can include a combination of resistive and capacitive elements. Such a topology can be referred to as an RC-PPF topology. Another passive circuit topology can be used to provide a PPF, by replacing the resistive elements with inductive elements, and by replacing the capacitive elements with resistive elements. A filter circuit can include cascaded RC-PPF and LR-PPF sections, such as in an alternating manner (e.g., an “RC-LR” topology). In this approach, a total insertion loss of cascaded LR-PPF and RC-PPF sections can be reduced as compared to using LR-PPF or RC-PPF sections, alone.