Dual-Mode Supply Modulator for RF Amplifier Bandwidth and Noise
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Solution Overview
Problem
Existing supply modulators for RF power amplifiers are inefficient due to limited bandwidth, low output power, and high switching noise, making them unsuitable for multi-standard communication devices that require different bandwidth, peak-to-average power ratio, and output power, leading to reduced battery life in mobile communication devices.
Innovation Solution
A dual-mode Sigma-Delta controlled supply modulator with an adaptive biasing Class AB amplifier that adjusts its operation mode based on communication standards, using synchronous Sigma-Delta mode for narrowband applications and asynchronous Sigma-Delta mode for wideband applications to optimize power efficiency, bandwidth, and reduce switching noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single supply modulator is used to support multiple communication standards, then device complexity and cost are reduced, but the modulator cannot be optimised for each standard's specific bandwidth, PAPR, and output power requirements
Solution Approach 1:
The supply modulator employs dynamic switching between two operational modes: synchronous Sigma-Delta mode for narrowband applications and asynchronous Sigma-Delta mode for wideband applications. The system dynamically adjusts its operating parameters including switching frequency, quiescent current magnitude, and control circuit configuration based on the detected communication standard, thereby achieving multi-standard optimisation without requiring separate dedicated modulators for each standard.
2Speed
If high switching frequency is used in the supply modulator, then bandwidth and response time are improved, but switching loss increases and power efficiency decreases
Solution Approach 1:
The system dynamically adjusts the switching frequency based on the operational mode and communication standard requirements. In synchronous mode, the switching frequency is tied to the clock signal frequency, optimised for narrowband applications. In asynchronous mode, the switching frequency is independently controlled to optimise for wideband applications while minimising switching losses. This dynamic adjustment allows the system to achieve high bandwidth when needed without incurring excessive switching losses during normal operation.
Solution Approach 2:
The invention changes key operating parameters including switching frequency, quiescent current magnitude, and control circuit configuration based on the detected communication standard and operational requirements. By varying these parameters dynamically, the system optimises the trade-off between switching speed and switching losses for different application scenarios.
3Loss of energy
If the supply modulator is optimised for narrowband applications, then power efficiency is improved, but bandwidth becomes insufficient for wideband communication standards
Solution Approach 1:
The supply modulator implements dynamic mode switching between synchronous Sigma-Delta operation optimised for narrowband applications and asynchronous Sigma-Delta operation optimised for wideband applications. The system automatically detects the communication standard and switches to the appropriate operational mode, thereby achieving both high power efficiency for narrowband standards and sufficient bandwidth for wideband standards without compromise.
4Power
If class AB amplifier quiescent current is increased, then output power capability and bandwidth are improved, but power consumption increases and power efficiency decreases
Solution Approach 1:
The Class AB amplifier's quiescent current is dynamically adjusted based on the operational mode and communication standard requirements. In synchronous mode for narrowband applications, a lower quiescent current is used to maximise power efficiency. In asynchronous mode for wideband applications, the quiescent current is increased to provide sufficient output power capability and bandwidth. The control circuit automatically manages this dynamic adjustment, ensuring optimal power consumption for each operating condition.
Data Source
AI summary
A supply modulator is provided, having a first amplifier circuit configured to generate a first electrical signal, a second amplifier circuit configured to generate a second electrical signal, the first and second electrical signals being for driving an electrical load, and a control circuit electrically coupled to the first and second amplifier circuits wherein the control circuit is configured to generate a pulsed electrical signal and to supply an output control signal to the second amplifier circuit for controlling generation of the second electrical output signal, wherein the supply modulator is configured to operate in two modes of operation, for the first amplifier circuit to generate the first electrical signals in response to quiescent current of the first amplifier circuit, for the control circuit to generate a modulated electrical signal in accordance with a clock signal in one mode, and, for the second amplifier circuit to operate.