Digitally Controlled RF Amplifier Switching to Reduce Leakage
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Solution Overview
Problem
Digital RF circuitry experiences leakage issues due to excess output voltage for low digital modulating signals, leading to high error vector magnitude (EVM) and reduced constellation points, as existing technologies fail to effectively manage switching and gain control.
Innovation Solution
The digital RF circuitry employs a digitally controlled amplifier with common-source amplifying unit cells, utilizing switching circuitry to activate or deactivate cells based on digital control signals, and a dynamic driver to adjust power levels, reducing leakage by ensuring the source node is pulled to a power supply when deactivated, thereby improving linearity and switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a digitally controlled amplifier is used to achieve gain control, then the RF signal amplitude can be modulated digitally, but leakage occurs producing excess output voltage for low digital modulating signal values
Solution Approach 1:
The amplifier is divided into multiple independent unit cells, each with its own switching mechanism. By segmenting the amplifier into discrete controllable units, the patent enables precise digital gain control while allowing individual cells to be completely switched off to eliminate leakage. Each unit cell operates independently and can be activated or deactivated based on the digital control signal, resolving the contradiction between digital control capability and leakage prevention.
2Device complexity
If the source node is left floating when the amplifier is disconnected, then the switching circuitry is simpler, but leakage increases and linearity deteriorates
Solution Approach 1:
The patent introduces a second switch as an intermediary element that actively pulls the source node to a defined voltage level when the amplifier is disconnected. This intermediary component ensures the source node does not float, thereby eliminating leakage and maintaining linearity. The additional switch, while increasing circuit complexity, is necessary to achieve complete amplifier shutdown and prevent the harmful leakage effect.
3Speed
If conventional switching is used without active pulling, then the switching speed is adequate, but the bandwidth of the digital control signal cannot match the required digital RF circuitry performance
Solution Approach 1:
The second switch performs preliminary action by actively pulling the source node to the appropriate voltage level before the amplifier needs to be fully deactivated. This proactive voltage establishment ensures that when switching occurs, the transistor is already in the correct state for rapid transition, thereby increasing switching speed and enabling the circuit to handle higher bandwidth digital control signals.
Data Source
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AI summary
Example embodiments describe a digital radio-frequency, RF, circuitry comprising a digitally controlled amplifier further configured to receive an RF input signal and a digital control signal, and to output an amplitude controlled output signal; the digitally controlled amplifier comprising one or more common-source amplifying unit cells (300); and wherein a respective common-source amplifying unit cell comprises a sources node (342) connected to a switching circuitry (360) controllable (301) by the digital control signal so as to activate or deactivate the common-source amplifying unit cell; and wherein the switching circuitry comprises a first (370) and second (380) switch configured to connect the source node with a first (390) respective second (391) power supply node when activating respectively deactivating the common-source amplifying unit cell.