SE2D CMOS Transconductance Amplifier Without RF Transformers
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Solution Overview
Problem
Modern radio receivers face challenges in integrating single-ended RF transceivers on system-on-chips due to interference from digital and power management circuits, requiring effective single-ended-to-differential (SE2D) conversion while minimizing cost and silicon area, and avoiding interference from clock harmonics and spurious signals.
Innovation Solution
The implementation of SE2D transconductance amplifiers using CMOS or BJT active devices, which include common-source transistors and cross-coupled cascode stages, to perform simultaneous single-ended-to-differential conversion, reducing the need for passive transformers and minimizing silicon area and interference sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a transformer is employed to perform SE2D conversion, then the conversion function is achieved, but the cost and bills-of-material (BOM) increase due to additional components
Solution Approach 1:
The patent extracts the SE2D conversion function from the traditional transformer-based approach and implements it using active devices (transistors) within the LNA circuit itself. This eliminates the need for separate passive transformers, directly reducing component quantity while maintaining conversion capability
Solution Approach 2:
The patent merges the SE2D conversion function with the LNA amplification function by using the same active devices for both purposes. The common-source and cross-coupled cascode transistors simultaneously perform signal amplification and single-ended-to-differential conversion, reducing overall component count
2Ease of manufacture
If a transformer is employed to perform SE2D conversion, then the conversion function is achieved, but the receiver noise figure (NF) increases due to finite loss
Solution Approach 1:
The patent replaces the passive mechanical transformer system with an active electronic circuit implementation using transistors. This substitution eliminates the inherent losses associated with transformer windings and magnetic core materials, achieving SE2D conversion with minimal signal loss and improved noise figure
3Adaptability or versatility
If multiple RF preselection filters and transformers are needed for multiband receivers, then frequency band coverage is achieved, but the cost and BOM increase further
Solution Approach 1:
The patent implements a universal SE2D conversion topology using active devices that can be configured for multiple frequency bands. The same basic circuit structure with common-source and cross-coupled cascode transistors serves all frequency bands, eliminating the need for separate transformers for each band and reducing overall component quantity in multiband receivers
Solution Approach 2:
The patent merges multiple SE2D conversion functions for different frequency bands into a single unified active device implementation. By using the same transistors and circuit topology for all bands, the design reduces the total number of components while maintaining multiband operational capability
4Ease of manufacture
If differential LNA input pins are required, then the SE2D transformation can be performed, but the total number of LNA input pins and RFIC cost increase
Solution Approach 1:
The patent merges the SE2D conversion function directly into the LNA input stage, allowing the LNA to accept a single-ended input signal while internally generating the differential signals needed for subsequent processing. This integration reduces the number of external input pins required on the RFIC
Solution Approach 2:
The patent extracts the differential signal generation function from the external transformer and relocates it to the internal active device circuitry of the LNA. This extraction eliminates the need for external differential input pins, simplifying the RFIC interface and reducing pin count
Data Source
AI summary
According to an aspect, there is provided a single-ended-to-differential complementary metal-oxide-semiconductor, SE2D CMOS, transconductance amplifier for a radio receiver. The SE2D CMOS transconductance amplifier comprises an input for receiving a radio frequency signal, first common-source n-type metal-oxide-semiconductor. CS NMOS (M1), and common-source p-type metal-oxide-semiconductor, CS PMOS, transistors (M5), second CS NMOS (M2) and CS PMOS (M6) transistors, a cross-coupled cascode stage for adjusting balance of the radio frequency currents outputted by the first (M1) and second (M2) CS NMOS transistors and a differential output. The first (M1) and second (M2) CS NMOS transistors have substantially equal transconductances and the first (M5) and second (M6) CS PMOS transistors have substantially equal transconductances. The first and second cross-coupled cascode NMOS transistors have substantially equal transconductances.