CGCS Mixer Input Stage for High-Gain RF Downconversion
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Solution Overview
Problem
The existing common-gate only (CGO) input stage in wireless device receiver chains requires a high Q matching network for high gain, making it sensitive to input Q matching factor and costly to implement.
Innovation Solution
A common-gate common-source (CGCS) input stage is introduced, which includes a pair of NMOS transistors and a pair of PMOS transistors with a current source, decoupling transconductance gain from the high Q matching network by adding a common-source stage through the PMOS differential-pair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a common-gate only (CGO) input stage is used to achieve high gain, then the transconductance gain is improved, but the sensitivity to the high Q matching network increases and the device complexity increases
Solution Approach 1:
The patent combines a common-gate stage (NMOS transistors) and a common-source stage (PMOS transistors) into a single CGCS input stage. This merging of two different circuit configurations allows the transconductance gain to be provided by both stages working together, reducing the dependency on the matching network Q factor while maintaining high gain performance.
Solution Approach 2:
The input stage is segmented into two functional parts: a common-gate stage for initial signal processing and a common-source stage for additional gain. This segmentation allows each stage to contribute differently to the overall transconductance gain, with the common-source stage compensating for losses without requiring high Q matching.
2Power
If a common-gate only (CGO) input stage is used to achieve high gain, then the transconductance gain is improved, but the sensitivity to input Q matching factor increases
Solution Approach 1:
By merging the common-gate and common-source stages, the patent creates a hybrid configuration where the common-source stage provides additional transconductance gain that is less sensitive to Q matching variations. This combination reduces the overall sensitivity to input Q matching factor while maintaining high gain.
Solution Approach 2:
The patent changes the circuit configuration parameters by introducing PMOS transistors in a common-source configuration alongside the NMOS common-gate stage. This parameter change fundamentally alters the transconductance characteristics, making the system less sensitive to Q matching factor variations.
3Reliability
If a common-gate common-source (CGCS) input stage is used to reduce sensitivity to matching network, then the sensitivity to high Q matching network is reduced, but the device complexity increases
Solution Approach 1:
The patent merges the common-gate and common-source stages into a unified CGCS input stage that processes differential signals. This merging achieves the dual benefit of reduced sensitivity to matching network Q factor while maintaining a relatively compact and integrated structure suitable for implementation.
Data Source
AI summary
In an embodiment, a wireless device receiver chain includes a mixer with a common-gate common-source (CGCS) input stage. Differential signals from an off-chip matching network may be input to the CGCS input stage of the mixer, which downconverts the signals to baseband or some intermediate frequency. The input stage includes a pair of NMOS transistors in a common-gate configuration and a pair of PMOS transistors in a common-source configuration. A potential advantage of the CGCS input stage over the existing CGO transconductance stage configuration is that by adding a common-source stage through the PMOS differential-pair, the transconductance gain is decoupled from the high Q matching network.