RF Transmitter Power Control Without Attenuator Loss
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Solution Overview
Problem
Existing RF transmitter systems require external resistors or energy-wasteful attenuators to control power output, which are inefficient and non-linear, especially in battery-powered devices, and lack the ability to adjust power levels dynamically within FCC and ETSI regulations.
Innovation Solution
An RF transmitter circuit with a buffer amplifier, switching-mode power amplifier, and a digital-to-analog converter (DAC) that provides linear-in-dB power control, allowing for digital adjustment of power output without external components, using a series connection of resistors and an inductor to control voltage and power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If attenuators are used to reduce RF power, then power control is achieved, but energy efficiency deteriorates and cost increases
Solution Approach 1:
The patent changes the operating parameters of the power amplifier by dynamically adjusting the supply voltage through a DAC-controlled voltage source. This allows the amplifier to operate at different power levels efficiently without using attenuators, directly resolving the contradiction between power control and energy efficiency.
Solution Approach 2:
The patent extracts and eliminates the attenuator component from the traditional RF power control system. By removing the energy-wasteful attenuator and replacing it with a voltage-controlled power amplifier approach, the system achieves power control without the associated energy losses and cost.
2Stability of the object's composition
If class A amplifiers are used, then linearity is improved, but energy efficiency deteriorates
Solution Approach 1:
The patent transitions from static class A amplifier operation to dynamic switching-mode amplifier operation. The amplifier switches between different operating states based on the required output power level, achieving both linearity through proper switching control and high efficiency by minimizing dissipative losses during switching transitions.
Solution Approach 2:
The patent changes the fundamental operating mode of the amplifier from class A continuous conduction to switching-mode operation. By controlling the switching duty cycle and supply voltage through the DAC, the system achieves linear power control characteristics while maintaining switching-mode efficiency.
3Device complexity
If external resistors are used for power control, then device complexity is reduced, but manufacturing precision and temperature stability deteriorate
Solution Approach 1:
The patent merges the power control functionality into the integrated circuit by incorporating a DAC and voltage control circuitry directly within the RF transmitter chip. This eliminates the need for external precision resistors while maintaining or improving power control accuracy through digital control and temperature-compensated reference voltages.
Solution Approach 2:
The patent replaces the passive resistor-based power control mechanism with an active digital control system. The DAC converts digital control words into precise analog voltage levels, providing superior manufacturing precision and temperature stability compared to passive resistor networks.
4Device complexity
If fixed power output is used, then device complexity is reduced, but adaptability deteriorates
Solution Approach 1:
The patent introduces dynamic power control capability by incorporating a DAC that can be programmed with different control words to set various output power levels. This allows the transmitter to adapt to different FCC regulatory requirements and application scenarios while maintaining a relatively simple control architecture driven by a microcontroller.
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
Enables efficient, accurate, and stable power control over a range of temperatures and frequencies, eliminating the need for attenuators and maintaining maximum permitted transmission power, while maintaining high efficiency and linear power control characteristics.
Implementation Method 1
a switching-mode power amplifier stage having an input coupled to an output of the buffer amplifier and having a power output
Implementation Method 2
a DAC having a digital input and an analog output
Implementation Method 3
an inductor coupling the analog output of the DAC to the switching-mode power amplifier stage
Data Source
AI summary
An integrated circuit device, set forth by way of example and not limitation, includes an IC package provided with a plurality of leads and enclosing: a) a buffer amplifier, b) a switching-mode power amplifier having an input coupled to the output of the buffer amplifier and having an output coupled to at least one of the plurality of leads, and c) a digital controller. A method, set forth by way of example and not limitation, for controlling the power output of a RF transmitter circuit without the need for an attenuator includes developing a signal source, applying the signal source to a buffer amplifier to provide an amplified signal, applying the amplified signal to a switching-mode power amplifier to provide a power output signal, and controlling a gain of the switching-mode power amplifier in response to a digital command.