RF Modulator Current-Mirror Architecture for High Linearity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing RF modulators face challenges in achieving high linearity without the complexity and increased current consumption associated with using an 8-phase mixer.
Innovation Solution
A novel RF modulator design that incorporates a baseband stage, a mixer stage, and a radio-frequency stage, utilizing a current mirror architecture with a diode-connected transistor in the baseband stage and a mirroring output transistor in the RF stage, allowing for analog pre-distortion and high linearity even with a simple passive mixer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an 8-phase mixer is used to reduce 3rd and 5th order RF harmonics and counter intermodulation products, then linearity is improved, but device complexity increases significantly
Solution Approach 1:
The invention divides the modulator into three distinct functional stages: baseband stage, mixer stage, and radio-frequency stage. Each stage performs a specific function with simplified circuitry, avoiding the need for a complex 8-phase mixer while maintaining high linearity through the distributed architecture
Solution Approach 2:
The invention changes the operating parameters and configuration of the mixer stage, using a simple passive mixer with specific switching arrangements that achieve high linearity when combined with the baseband and RF stages, replacing the need for complex 8-phase mixer configurations
2Reliability
If an 8-phase mixer is used to reduce harmonics and intermodulation products, then linearity is improved, but current consumption increases
Solution Approach 1:
By segmenting the modulator into three stages with simplified circuitry in each stage, the total current consumption is reduced compared to a single complex 8-phase mixer, as each stage can be optimized for low power operation
Solution Approach 2:
The invention uses a simple passive mixer instead of an expensive and power-consuming 8-phase mixer, accepting that the passive mixer has limitations but compensating through the overall three-stage architecture to achieve the desired linearity at lower power cost
3Reliability
If an 8-phase mixer is used to reduce harmonics and intermodulation products, then linearity is improved, but die area increases
Solution Approach 1:
The three-stage architecture distributes the linearity-function across separate baseband, mixer, and RF stages, each occupying smaller die area compared to a single large 8-phase mixer, thus reducing total die area while maintaining high linearity
Solution Approach 2:
The invention changes the mixer configuration from a complex 8-phase design to a simple passive mixer with fewer components, significantly reducing the die area required for the mixer stage while achieving equivalent or better linearity through the overall system design
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
The design achieves highly linear behavior with reduced complexity and lower current consumption, making it suitable for integration as an IC without the need for large die area, and supports a wide gain control range.
Implementation Method 1
The mixing process is intentionally non-linear, so that it generates sum and difference components at radio frequencies that depend on the input signal
Implementation Method 2
a baseband transistor arranged to pass some or all of the input current between a first terminal and a second terminal of the baseband transistor
Implementation Method 3
configured to apply the radio-frequency mixed signal to a control terminal of the radio-frequency transistor so as to cause the radio-frequency transistor to pass a radio-frequency output current between a first terminal and a second terminal
Data Source
AI summary
A radio-frequency modulator apparatus comprises a baseband stage, a mixer stage and a radio-frequency stage. The baseband stage comprises: an input line for receiving an input current representative of a baseband input signal, a baseband transistor that passes some or all of the input current between a first and a second terminal thereof, an electrical connection between the input line and a control terminal of the baseband transistor, and an output line connected to said control terminal. The mixer stage receives a signal from the baseband stage and mixes it with a radio-frequency local-oscillator signal to generate a radio-frequency mixed signal. The radio-frequency stage receives the radio-frequency mixed signal, applies the radio-frequency mixed signal to a control terminal of a radio-frequency transistor causing it to pass a radio-frequency output current between a first and a second terminal thereof, and outputs the radio-frequency output current as an output signal.