Transformer Matching Network With Tunable Notch for LO Spur Rejection
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Solution Overview
Problem
Millimeter-wave communication systems face challenges in minimizing spurious emissions from local oscillator frequencies, which can detrimentally affect communication signals, particularly in stringent radio frequency energy emission standards for 5G systems.
Innovation Solution
A matching network with a tunable notch filter is implemented, utilizing a transformer with interwinding capacitance to create a notch filter response, allowing for adjustable rejection of spurious signal energy near communication bands of interest, thereby minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a matching network is implemented in mmW communication systems, then impedance matching is achieved, but spurious emissions at LO and harmonic frequencies are generated that interfere with communication signals
Solution Approach 1:
The patent converts the harmful spurious emissions generated by the matching network into a beneficial filtering mechanism. By introducing a notch filter tuned to the LO and harmonic frequencies, the circuit that originally generated interference now actively rejects these unwanted frequencies, transforming the harmful spurious emissions into a design feature that eliminates the interference problem while maintaining impedance matching performance
Solution Approach 2:
The patent introduces a notch filter as an intermediary element between the matching network and the communication signal path. This intermediary component specifically targets and removes spurious emissions at LO and harmonic frequencies without affecting the desired communication signals, thereby mediating between the impedance matching function and the spurious emission problem
2Object-affected harmful factors
If fixed filtering is used to reject spurious emissions, then LO and harmonic frequencies are suppressed, but the filter cannot adapt to different communication bands and frequencies
Solution Approach 1:
The patent implements a tunable notch filter with variable capacitance that can dynamically adjust its center frequency and rejection characteristics. This dynamic adjustment capability allows the filter to adapt to different communication bands and frequencies by changing the capacitance value, thereby maintaining effective spurious emission rejection across multiple frequency ranges while preserving adaptability to various communication standards
Solution Approach 2:
The patent changes the electrical parameters of the notch filter, specifically the capacitance value, to adjust the filter's center frequency and rejection characteristics. By varying the capacitance parameter, the filter can be tuned to different frequencies to match different communication bands, enabling the system to adapt to various operating conditions while maintaining effective suppression of spurious emissions
3Object-affected harmful factors
If additional filtering components are added to reduce spurious emissions, then emission standards are met, but device complexity and circuit size increase
Solution Approach 1:
The patent merges the notch filter functionality with the existing matching network by integrating the filter components directly into the matching circuit topology. This consolidation allows the circuit to perform both impedance matching and spurious emission rejection simultaneously, reducing overall device complexity and minimizing additional circuit elements while still meeting stringent emission standards
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 effectively reduces spurious emissions, meeting stringent emission standards while maintaining communication signal integrity, and is applicable in both transmit and receive chains of mmW communication devices.
Implementation Method 1
conveying a signal through a transformer having an interwinding capacitance across an input of a primary side of a transformer and a non-inverting output of a secondary side of the transformer
Implementation Method 2
a transformer having at least one interwinding capacitance coupled from an input on the primary side to a non-inverting output on the secondary side
Implementation Method 3
adjusting a value of the interwinding capacitance to determine a notch filter response
Data Source
AI summary
A filter circuit includes a matching network having resistive and capacitive elements, and a transformer in the matching network. The transformer includes a primary side and a secondary side, and has at least one interwinding capacitance coupled from an input on the primary side to a non-inverting output on the secondary side.