Hybrid RF VGA Topology for Fine Gain Steps and Low Phase Variation
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Solution Overview
Problem
Existing RF phase shifters face challenges in achieving high resolution and low phase variation due to limitations in VGA architectures, with current steering VGAs providing fine gain steps but high output capacitance variation, and current cancelling VGAs offering larger gain steps with lower capacitance variation but limited resolution.
Innovation Solution
A combined current steering and current cancelling VGA architecture is introduced, comprising a flexible bit configuration for both portions, allowing for high gain step resolution and low phase variation by seamlessly transitioning between fine and coarse gain adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current steering VGA architecture is used, then gain step resolution is improved, but output capacitance variation increases causing phase variation
Solution Approach 1:
The patent combines current steering and current cancelling VGA architectures into a hybrid structure. The current steering portion (M3P, M3N) provides fine gain resolution through binary-weighted slices, while the current cancelling portion (M2P, M2N, M4P, M4N) compensates for output capacitance variation. This merging allows simultaneous achievement of high gain resolution and low phase variation by leveraging complementary strengths of both architectures.
Solution Approach 2:
The patent creates a composite VGA architecture that integrates two different VGA topologies (current steering and current cancelling) into a unified structure. This composite approach allows the system to exhibit properties of both architectures: the fine resolution capability of current steering and the low capacitance variation of current cancelling, achieving performance superior to either individual architecture.
2Stability of the object's composition
If current cancelling VGA architecture is used, then output capacitance variation is reduced, but gain step resolution is limited
Solution Approach 1:
The patent merges current steering and current cancelling VGA architectures into a hybrid structure. The current steering portion (M3P, M3N) provides fine gain resolution through binary-weighted slices, while the current cancelling portion (M2P, M2N, M4P, M4N) compensates for output capacitance variation. This merging allows simultaneous achievement of high gain resolution and low phase variation by leveraging complementary strengths of both architectures.
3Measurement precision
If binary weighted slices are increased for finer gain control, then gain resolution is improved, but device width and area increase
Solution Approach 1:
The patent segments the VGA into multiple binary-weighted slices that can be independently controlled. By dividing the current control into discrete slices (M2P, M2N, M3P, M3N, M4P, M4N) with binary weights, the architecture achieves fine gain resolution through combinatorial control of slices rather than requiring a single large variable-width device. This segmentation reduces the maximum device width needed while maintaining high resolution.
Solution Approach 2:
The patent transitions from controlling gain through a single dimension (device width) to controlling it through multiple dimensions (combinatorial activation of binary-weighted slices). This dimensional change allows achieving the same or better gain resolution with reduced maximum device width by utilizing the exponential resolution capability of binary-weighted multi-bit control.
Data Source
AI summary
A system and a method are disclosed for RF variable gain amplification using a combination of current steering and current cancellation techniques. An active radio frequency (RF) variable gain amplifier (VGA) architecture is disclosed that combines current steering and current cancelling techniques to achieve fine gain resolution, low phase variation, and improved attenuation for high-resolution RF phase shifters. The disclosed VGA integrates an m-bit current steering portion with an n-bit current cancelling portion, each comprising binary weighted slices with a flexible bit architecture to configure for resolution and accuracy. Embodiments include a phase shifting electronic circuit employing such VGAs for in-phase and quadrature signal paths, enabling 360° phase coverage, low error beamforming, and adaptability for applications such as radar and satellite communications.