Three-Transformer Analog Front End for Phase and Gain Imbalance
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Solution Overview
Problem
Impedance mismatches in front-end signal chains of analog to digital converters (ADCs) lead to amplitude and phase imbalance, particularly in multi-band ADCs, causing non-linearities and degrading signal quality due to second harmonics, which existing transformer and balun transformer configurations struggle to balance effectively.
Innovation Solution
A configuration comprising three transformers, including two balun transformers with matched capacitances and impedance ratios, which cancels out first-order common mode current and reduces second-order common mode current, thereby improving signal balance and reducing non-linearities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impedance matching is improved, then signal quality improves, but device complexity increases
Solution Approach 1:
The three-transformer configuration serves multiple functions simultaneously: impedance transformation, differential signal generation, common mode rejection, and amplitude/phase balancing. By making the system multi-functional, the increased complexity is justified by the comprehensive signal quality improvement and the ability to address multiple issues (impedance matching, balance, harmonic rejection) with a single integrated solution
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 configuration achieves a significant reduction in second harmonic distortion and improves signal quality by balancing phase and amplitude imbalances, providing a 14 decibel improvement in second harmonic distortion over traditional configurations.
Implementation Method 1
The first transformer comprises a first primary winding coupled to ground and a first secondary winding coupled to a first node and a second node. The first primary winding is configured to receive an input signal at an input node.
Implementation Method 2
a first capacitance between the second primary winding and the first output of the second secondary winding and a second capacitance between the third primary winding and the third output of the third secondary winding are substantially the same
Data Source
AI summary
An analog front end device comprises three transformers. A first transformer has a first input configured to receive an input signal and first and second outputs. The second and third transformers comprise a secondary stage coupled to the first and second outputs. The second transformer has a second input coupled to the first output, a third output coupled to a first device output, and a fourth output coupled to a second device output. The third transformer has a third input coupled to the second output, a fifth output coupled to the second device output, and a sixth output coupled to the first device output. The phase imbalances of the second and third transformers are substantially the same, and the amplitude imbalances of the second and third transformers are substantially the same.