Coupled-Inductor RF Balun for Wideband On-Chip Impedance Switching
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Solution Overview
Problem
Conventional transmission line based baluns are bulky and not feasible for on-chip design, and existing switchable input impedance solutions occupy large on-chip area, limiting their integration and flexibility in RF integrated systems.
Innovation Solution
A compact balanced RF balun design using coupled inductor coils with differential symmetric band extension circuitry and switchable input/output tuning capacitors, which converts between differential and single-ended signal formats and provides switchable impedance, achieving compact size and wideband operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transmission line based baluns are used to achieve ultra wide bandwidth, then bandwidth is improved, but the device becomes bulky and not feasible for on-chip design
Solution Approach 1:
The patent replaces the mechanical transmission line structure with an electromagnetic field-based coupled inductor design. The coupled inductors utilize magnetic coupling to achieve broadband operation without requiring the physical length of transmission lines, thereby reducing on-chip area while maintaining wide bandwidth performance.
Solution Approach 2:
The patent achieves broadband operation by dynamically adjusting the coupling coefficient between inductors and using variable capacitors to tune the resonant frequency. By changing these parameters across the frequency spectrum, the balun maintains wide bandwidth without requiring a physically large structure.
2Adaptability or versatility
If switchable transformer cores are used to provide switchable input impedance, then impedance flexibility is improved, but the on-chip area occupied increases significantly
Solution Approach 1:
The patent implements dynamic impedance switching by using switches to reconfigure the coupled inductor connections and variable capacitors to adjust capacitance values. This dynamic reconfiguration allows input impedance switching without requiring multiple large transformer cores, achieving impedance flexibility in a compact form factor.
Solution Approach 2:
The coupled inductor structure serves multiple functions simultaneously: it provides both the broadband transformation capability and the switchable impedance functionality. By making the same inductor structure reconfigurable through switches and variable capacitors, the design eliminates the need for separate dedicated structures for each function, reducing overall on-chip area.
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 solution enables easy integration, wideband operation, and flexible impedance switching while maintaining good phase and amplitude balance, occupying significantly less chip area than conventional baluns, with amplitude imbalance less than 1 dB and phase imbalance less than 5 degrees across a wide frequency range.
Implementation Method 1
The second circuit generally comprises coupled inductor coils configured to convert between differential and single-ended signal formats
Data Source
AI summary
An apparatus comprises a first circuit and a second circuit. The first circuit generally comprises differential symmetric band extension circuitry. The second circuit generally comprises coupled inductor coils configured to convert between differential and single-ended signal formats.