Bidirectional VCO Band-Pass ADC for Direct RF Sampling
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Solution Overview
Problem
Conventional VCO-based ADCs face challenges in sampling high-frequency signals due to limited input swing range, insufficient phases, and power consumption issues, making them unsuitable for band-pass signal processing and requiring complex time-interleaving and multiple channels.
Innovation Solution
A band-pass ADC using a bidirectional VCO with a dual converter and multiplexer structure, performing time-interleaving in both directions to directly convert RF or intermediate frequencies without down-conversion, reducing the number of VCOs and channels needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional VCO-based ADC uses a unidirectional time-interleaving structure, then the ADC can process signals, but it requires multiple VCOs and channels which increases device complexity and power consumption
Solution Approach 1:
The patent combines multiple VCO operations into a single bidirectional VCO that can operate in both forward and reverse directions. This merging of functions allows the system to achieve the same time-interleaved sampling capability with fewer physical components, directly reducing device complexity and associated power consumption
Solution Approach 2:
The bidirectional VCO serves multiple functions: it performs both forward and reverse time-interleaved sampling operations that would traditionally require separate unidirectional VCOs. This multi-functionality eliminates the need for multiple dedicated channels, reducing overall system complexity
2Measurement precision
If a conventional VCO limits input swing range to maintain linearity, then linearity is preserved, but the number of phases is insufficient which deteriorates ADC performance
Solution Approach 1:
The patent inverts the conventional approach by using a bidirectional VCO that can swing in both positive and negative directions. This inversion allows the system to generate more phase information (including negative phases) while maintaining linearity through controlled bidirectional operation, rather than being constrained by unidirectional swing limits
Solution Approach 2:
The bidirectional VCO adds a temporal dimension to the phase generation by utilizing both forward and reverse time-interleaved operations. This creates additional phase states beyond the conventional unidirectional approach, increasing the number of detectable phases while preserving linearity through symmetric operation
3Device complexity
If a conventional VCO-based ADC uses down-conversion for RF processing, then signal processing is performed, but the structure becomes complex and is not suitable for direct band-pass sampling
Solution Approach 1:
The patent extracts the essential sampling function from the complex down-conversion process by using bidirectional time-interleaved sampling to directly capture band-pass signals. This removes the need for separate mixer and down-conversion stages, simplifying the overall structure while maintaining band-pass sampling capability
Solution Approach 2:
The patent replaces the mechanical/analog down-conversion mechanism with a time-based digital sampling approach using bidirectional VCO. This substitution eliminates complex analog mixing circuits and enables direct digital processing of RF signals, achieving both simplification and enhanced adaptability
Data Source
AI summary
The present disclosure discloses a band-pass analog-to-digital converter (ADC) using a bidirectional voltage-controlled oscillator (VCO) including a first converter configured to receive an analog input signal and quantize the analog input signal according to a first clock signal to output a first digital signal, a second converter configured to receive the analog input signal and quantize the analog input signal in a time-interleaving manner according to a second clock signal, which has a phase opposite to that of the first clock signal, to output a second digital signal, and a multiplexer configured to receive the first and second digital signals and select one of the two signals in response to the first clock signal to finally output a digital output signal.