Controllable Input Impedance RF Mixer for High-Q Filtering
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Solution Overview
Problem
RF communications systems face challenges in achieving narrow bandwidth RF bandpass filtering with high quality factor to effectively reject interfering signals, especially in tight channel spacing scenarios, where existing filtering techniques struggle to maintain selectivity and reduce image problems.
Innovation Solution
A controllable input impedance RF mixer with polyphase reactive circuitry, such as capacitive elements, is used to create a high-Q RF bandpass filter upstream of down conversion, which translates the impedance of the polyphase reactive circuitry into the RF input impedance, allowing for non-overlapping local oscillator signals to maximize energy transfer and eliminate signal losses, and can be enhanced with transconductance circuitry to shift the impedance peak and create complex filtering responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional RF bandpass filters are used to achieve narrow bandwidth and high quality factor, then signal selectivity is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent combines the RF mixer and bandpass filter into a single integrated circuit. The mixer's impedance transformation capability is exploited to create a high-Q bandpass filter response at the RF input, eliminating the need for separate filter components and reducing overall device complexity while maintaining high signal selectivity
Solution Approach 2:
The RF mixer is designed to perform multiple functions simultaneously: signal mixing for downconversion and RF bandpass filtering. By configuring the polyphase reactive circuitry with non-overlapping local oscillator signals, the mixer creates a high-Q impedance peak that provides both mixing and filtering capabilities in a single device
2Object-affected harmful factors
If RF filtering is performed before down conversion to reduce image signals, then image rejection is improved, but energy loss and signal degradation increase
Solution Approach 1:
The mixer circuit is designed to be self-tuning, where the polyphase reactive circuitry automatically adjusts its impedance characteristics based on the local oscillator signal phases. This self-adjusting mechanism ensures maximum energy transfer to the filter while maintaining high-Q selectivity, eliminating the need for external tuning mechanisms and reducing energy loss
3Productivity
If tight channel spacing is used to increase spectrum efficiency, then bandwidth utilization is improved, but filtering difficulty and interference increase
Solution Approach 1:
The patent changes the impedance parameters of the mixer circuit by using polyphase reactive circuitry with non-overlapping local oscillator signals. This creates a high-Q impedance peak that provides sharp frequency selectivity, enabling tight channel spacing while maintaining effective filtering through parameter transformation rather than complex filter structures
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 solution provides improved receiver selectivity, low energy loss, and low noise performance by achieving high quality factor filtering, effectively rejecting interfering signals and reducing image issues, while allowing for self-tuning and flexible filtering configurations.
Implementation Method 1
The RF mixer mixes RF input signals with local oscillator signals to translate the impedance of the polyphase reactive circuitry into the RF input impedance of the RF mixer
Implementation Method 2
The present invention uses polyphase reactive circuitry, such as capacitive elements, coupled to the down conversion outputs of an RF mixer
Data Source
AI summary
The present invention is a controllable input impedance RF mixer, which when fed from a high impedance source, such as a current source, provides a high quality factor (Q) impedance response associated with an impedance peak. The high-Q impedance response may be used as a high-Q RF bandpass filter in a receive path upstream of down conversion, which may improve receiver selectivity and replace surface acoustic wave (SAW) or other RF filters. The present invention uses polyphase reactive circuitry, such as capacitive elements, coupled to the down conversion outputs of an RF mixer. The RF mixer mixes RF input signals with local oscillator signals to translate the impedance of the polyphase reactive circuitry into the RF input impedance of the RF mixer. The RF input impedance includes at least one impedance peak. The local oscillator signals are non-overlapping to maximize the energy transferred to the polyphase reactive circuitry.