Capacitor-Compensated Polyphase Filter for Stable I/Q Matching
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Solution Overview
Problem
Developing a fully reconfigurable analog front-end for low-power adaptive radios that achieves suitable performance in digital-optimized process technology while reducing manufacturing cost and leveraging high-speed process technologies, particularly in implementing rejection filtering and low-noise amplification for digital CMOS processes, is challenging.
Innovation Solution
A capacitor-compensated polyphase filter is introduced, which provides inductive output impedance, negating the need for additional matching networks and is robust against load changes, enabling improved IQ performance and compact design by incorporating capacitive compensation mechanisms within the polyphase network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fully reconfigurable analog front-end is implemented in digital-optimized CMOS process technology, then power savings and adaptability are improved, but manufacturing cost increases and performance suitability deteriorates
Solution Approach 1:
The patent changes the electrical parameters of the polyphase filter by introducing capacitive compensation elements that adjust the impedance characteristics. This allows the filter to achieve inductive output impedance without requiring additional matching networks, thereby maintaining performance suitability in digital-optimized CMOS processes while preserving reconfigurability through the fundamental filter architecture.
2Use of energy by moving object
If rejection filtering and low-noise amplification are implemented for digital CMOS processes, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The patent merges the impedance matching function into the polyphase filter structure itself by using capacitive compensation. The compensated polyphase filter simultaneously performs rejection filtering and provides inductive output impedance, eliminating the need for separate matching networks and thereby reducing device complexity while maintaining low power consumption.
Solution Approach 2:
The compensated polyphase filter is designed to perform multiple functions: rejection filtering, impedance transformation, and power matching. This multi-functional design reduces the overall device complexity by consolidating what would otherwise require separate components, while the digital-optimized CMOS implementation ensures low power consumption.
3Measurement precision
If capacitor compensation mechanism is incorporated in polyphase network, then IQ performance is improved, but device complexity increases
Solution Approach 1:
The capacitive compensation elements are integrated directly into the polyphase filter structure, merging the IQ balance correction function with the filtering function. This integration improves IQ performance by compensating for phase and amplitude imbalances while avoiding the need for separate correction circuits, thereby limiting the increase in device complexity.
Data Source
AI summary
A polyphase filter operates to provide capacitive compensation to drive a multiphase network for generating quadrature signals. The polyphase filter can include a capacitive compensation mechanism at internal nodes. The capacitive compensation mechanism includes a first phase lag circuit between a first internal node and a second internal node and a second phase lag circuit coupled between a third internal node and a fourth internal node. The first internal node is coupled to the second internal node via a first inductor coupled to a first resistor, the second internal node is coupled to the third internal node via a second inductor coupled to a second resistor, the third internal node is coupled to the fourth internal node via a third inductor coupled to a third resistor, and the fourth internal node is coupled to the first internal node via a fourth inductor coupled to a fourth resistor.