Envelope-Tracking Bias Circuit with Offset Cancellation
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Solution Overview
Problem
Existing envelope-tracking bias circuits suffer from deviations in bias current values due to process deviations in rectifying diodes, leading to inconsistencies in turn-on voltage, which affect the accuracy of envelope detection in power amplifying systems.
Innovation Solution
The proposed envelope-tracking current bias circuit employs two rectifying circuits with similar structures and an arithmetic circuit to detect and subtract DC offset voltages, ensuring accurate envelope signal detection by canceling out deviations and maintaining a constant average bias current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rectifying circuit with rectifying diodes is used to detect envelope signal, then envelope detection function is achieved, but deviation in bias current value occurs due to process deviation in diodes
Solution Approach 1:
The patent changes the operating parameters of the rectifying diodes by applying different DC offset voltages to compensate for process deviations. By adjusting the bias conditions and using arithmetic operations to subtract offset voltages, the system maintains consistent envelope detection accuracy despite variations in diode characteristics due to manufacturing process deviations.
2Ease of manufacture
If multiple passive elements and rectifying diodes are used in rectifying circuit, then rectification function is achieved, but turn-on voltage deviation occurs due to process deviation
Solution Approach 1:
The patent implements a feedback mechanism where the DC offset voltage generated by the rectifying circuit is detected and then subtracted through arithmetic operations. This feedback loop compensates for turn-on voltage deviations caused by process variations, maintaining precise envelope signal detection while using standard rectification components.
3Productivity
If DC offset voltage is present in envelope detection signal, then detection signal is generated, but detection accuracy is reduced due to offset
Solution Approach 1:
The patent extracts and removes the DC offset voltage component from the envelope detection signal through arithmetic subtraction operations. By separating the offset voltage from the actual envelope signal and subtracting it, the system maintains high detection accuracy while preserving the productivity of envelope signal generation.
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 approach reduces DC offset and variation in detection signals, enhancing the accuracy of envelope detection and maintaining consistent output power and efficiency in power amplifying systems.
Implementation Method 1
a first rectifying diode having an anode connected to the other end of the first capacitor, and configured to rectify the input signal
Implementation Method 2
a second capacitor connected to the second resistor in parallel, configured to smoothen the rectified signal and provide the envelope signal
Implementation Method 3
a second rectifying diode having an anode connected to the other end of the third capacitor
Implementation Method 4
The first arithmetic circuit is configured to provide an envelope signal in which the first DC offset voltage is reduced through subtraction between the envelope detection signal and the second DC offset voltage
Data Source
AI summary
An envelope-tracking current bias circuit includes a first rectifying circuit, a second rectifying circuit, and a first arithmetic circuit. The first rectifying circuit is configured to detect an envelope of an input signal, and provide an envelope detection signal comprising a first direct current (DC) offset voltage. The second rectifying circuit is configured to provide a second DC offset voltage corresponding to the first DC offset voltage. The first arithmetic circuit is configured to provide an envelope signal in which the first DC offset voltage is reduced through subtraction between the envelope detection signal and the second DC offset voltage.