Current-Mixing I/Q Modulator for Low-Power Direct Conversion
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Solution Overview
Problem
Conventional direct conversion wireless communication systems face issues with high power consumption and linearity due to signal attenuation in the I/Q modulator, requiring large current consumption to achieve high voltage gain.
Innovation Solution
An I/Q modulator using current-mixing method, where a D/A converted signal is converted to a current level and subjected to frequency modulation, eliminating the need for signal attenuation and incorporating voltage-to-current converters, current sources, and frequency mixing units to improve EVM, linearity, and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If signal attenuation is applied to reduce the voltage level of D/A converted signal, then linearity is improved, but power consumption increases due to large current consumption required for high voltage gain
Solution Approach 1:
The patent changes the operating parameter from voltage domain to current domain by introducing voltage-to-current converters. The D/A converted signal is converted to current level before frequency modulation, and the I/Q modulator operates with current signals instead of voltage signals, eliminating the need for signal attenuation and reducing power consumption while maintaining linearity
Solution Approach 2:
The patent introduces voltage-to-current converters as intermediary components between the D/A converter and the frequency mixing units. These converters transform the voltage signal from D/A converter into current signal, which then feeds into the frequency mixing units, serving as a mediator that resolves the contradiction between linearity and power consumption
2Manufacturing precision
If high voltage gain is achieved in I/Q modulator design, then signal quality is improved, but current consumption increases significantly
Solution Approach 1:
The patent changes the fundamental operating parameter from voltage to current throughout the I/Q modulator. The frequency mixing units operate with current signals, and the output is taken from current domain, eliminating the need for high voltage gain stages that consume large current, thereby improving signal quality while reducing current consumption
3Device complexity
If direct conversion architecture is used to reduce power consumption and complexity, then device complexity is reduced, but linearity deteriorates due to signal attenuation requirements
Solution Approach 1:
The patent applies parameter change from voltage domain to current domain in the direct conversion architecture. By converting D/A output to current and operating the entire I/Q modulator in current domain, the system maintains the simplicity of direct conversion while eliminating the linearity degradation caused by voltage signal attenuation requirements
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 enhances the EVM, linearity, and reduces power consumption by eliminating the need for signal attenuation, facilitating a more efficient and compact design of the I/Q modulator.
Implementation Method 1
one or more voltage-to-current converters for receiving a digitally modulated and D/A converted signal of a voltage level and for converting the signal of the voltage level to a signal of a current level
Implementation Method 2
one or more frequency mixing units for mixing a signal to be modulated and the local signal having the one or more phases
Data Source
AI summary
The present invention relates to an I/Q modulator using a current-mixing method used for a direct conversion wireless communication transmitter. In accordance with the present invention, an EVM of a wireless communication system, a linearity and a power consumption are improved by converting a D/A converted signal to a current level and then performing a frequency modulation.