Low-Voltage Active RF Mixer With Parallel Commutator Cells
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Solution Overview
Problem
Conventional RF mixers, such as the Gilbert cell mixer, suffer from noise issues, lower power gain, and impedance mismatch problems, particularly at high frequencies, limiting their performance and dynamic range.
Innovation Solution
The proposed RF mixer employs a generalized impedance matched low-voltage active mixer circuit with commutator cells and transformers, utilizing a series-shunt feedback amplifier for variable gain and image rejection filtering, and splits the total DC current equally among multiple commutator cells to achieve improved impedance matching and power handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Gilbert cell mixer is used, then frequency conversion is achieved, but noise figure increases and power gain decreases
Solution Approach 1:
The mixer is divided into multiple independent commutator cells (first commutator cell, second commutator cell, etc.) that operate in parallel. Each cell processes a portion of the input signal, and their outputs are combined. This segmentation allows the total DC current to be distributed across multiple cells, reducing the current burden on each individual cell and thereby reducing noise while maintaining or improving power gain through parallel operation.
Solution Approach 2:
Multiple commutator cells are combined in parallel configuration, with their outputs summed together. The DC currents from multiple cells are merged to provide the total mixer current, while the RF signals are processed independently and then combined. This merging approach provides noise diversification while maintaining signal coherence, improving the overall noise figure and power gain characteristics.
2Reliability
If DC current is increased to improve linearity, then IIP3 and P1dB increase, but power consumption increases
Solution Approach 1:
The total DC current requirement is segmented across multiple commutator cells. Each cell operates at a lower individual current level but with optimized impedance matching, achieving the same or better linearity performance (IIP3 and P1dB) without requiring proportionally higher total power consumption. The parallel architecture allows current to be distributed efficiently.
Solution Approach 2:
The invention changes the impedance parameters of the commutator cells through optimized design, allowing each cell to operate more efficiently at lower current levels. By adjusting the impedance matching and operating parameters of each cell, the system achieves high linearity performance without linearly increasing the total DC current and power consumption.
3Power
If impedance matching is improved, then power transfer efficiency increases, but device complexity increases
Solution Approach 1:
The invention optimizes the impedance parameters of the commutator cells through design calculations and adjustments. By changing the impedance values and matching networks within each cell, power transfer efficiency is maximized without requiring complex external matching circuits. The impedance parameters are tailored to achieve optimal power transfer while maintaining simplicity in the overall architecture.
Data Source
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AI summary
Embodiments of power efficient radio mixers are provided. A generalized impedance matched low-voltage active mixer circuit technique, which utilizes a plurality of commutator cells and transformers, is disclosed. The low voltage active mixer function is coupled to an impedance matched amplifier allowing for insertion of image rejection filtering between the amplifier and the mixing function. The commutator cells can be driven in parallel by common local oscillator (LO) and intermediate frequency (IF) ports combined in parallel to yield highly linear mixers. A multi-channel receiver with a common impedance matched radio frequency (RF) amplifier driving a plurality of commutator cells with multiple LOs and IFs is also disclosed.