Current-Canceling CMOS VGA for Linear Transmitter Power Control
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Solution Overview
Problem
Conventional wireless transmitters face issues due to undesirable nonlinearities and increased power consumption caused by voltage-to-current and current-to-voltage conversions, and they struggle to provide a linear relationship between power output and control voltage, especially when not using bipolar transistors.
Innovation Solution
A CMOS transmitter design that operates in the current mode, eliminating voltage-to-current and current-to-voltage conversions, and employs current canceling variable gain amplifiers to achieve a linear power output curve similar to the desired exponential relationship.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage-to-current and current-to-voltage conversions are used in conventional CMOS transmitters, then signal transmission is achieved, but nonlinearities increase and power consumption increases
Solution Approach 1:
The patent extracts and eliminates the voltage-to-current and current-to-voltage conversion stages from the CMOS transmitter signal path. By operating entirely in the current mode from DAC through VGA to PA, the harmful conversion nonlinearities are removed while maintaining signal transmission functionality.
Solution Approach 2:
The patent substitutes the conventional voltage-mode signal processing mechanism with a current-mode mechanism. Instead of using voltage signals that require conversion, the system uses current signals throughout, replacing the mechanical conversion process with a direct current-mode operation that inherently avoids the nonlinearities.
2Reliability
If voltage-to-current and current-to-voltage conversions are used in conventional CMOS transmitters, then signal transmission is achieved, but power consumption increases
Solution Approach 1:
The patent extracts and eliminates the power-consuming voltage-to-current and current-to-voltage conversion stages from the transmitter. By operating entirely in current mode, the unnecessary power consumption associated with these conversions is removed while maintaining signal transmission quality.
3Power
If conventional VGA gain control is used in non-bipolar technologies, then amplification is achieved, but linear relationship between power output and control voltage cannot be maintained
Solution Approach 1:
The patent changes the operating parameters of the VGA by implementing it in current mode rather than voltage mode. This parameter change enables the use of exponential-to-linear conversion circuits that can achieve the desired linear relationship between control voltage and power output, which is difficult to achieve in conventional voltage-mode non-bipolar implementations.
4Ease of manufacture
If conventional CMOS transmitter design is used, then integration is achieved, but the number of devices increases due to conversion requirements
Solution Approach 1:
The patent extracts and removes the additional conversion devices (voltage-to-current and current-to-voltage converters) from the conventional CMOS transmitter design. By operating entirely in current mode, the signal path requires fewer devices while maintaining integration and manufacturability.
Data Source
AI summary
A current canceling CMOS variable gain amplifier includes a first leg and a second leg. The first leg has a first input line, a first output line, a first ON transistor, a first control transistor and a first subtracting transistor. The second leg has a second input line, a second output line, a second ON transistor, a second control transistor and a second subtracting transistor. The second input line can provide a second input current. The second output line can provide a second output current. The first input line is arranged to provide a first input current to each of the first ON transistor, the first control transistor and the first subtracting transistor. The second input line is arranged to provide a second input current to each of the second ON transistor, the second control transistor and the second subtracting transistor. The first output line is in electrical connection with each of the first ON transistor, the first control transistor and the second subtracting transistor. The second output line is in electrical connection with each of the second ON transistor, the second control transistor and the first subtracting transistor.