Digital RF Amplifier Source Switching for Low-Leakage Modulation
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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, especially for signals close to the origin.
Innovation Solution
A digitally controlled amplifier with a common-source amplifying unit cell topology, utilizing switching circuitry to activate or deactivate amplifying cells based on digital control signals, and a dynamic driver circuitry that toggles off driver components for lower digital control signal values to minimize leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional drain or gate switched amplifier topologies are used, then the amplifier can be activated or deactivated, but leakage occurs resulting in excess output voltage for low digital modulating signals
Solution Approach 1:
The patent changes the switching parameter from drain or gate voltage control to source node voltage control. By switching the source node between a first voltage level (activating the amplifier) and a second voltage level (deactivating the amplifier), the invention achieves complete cutoff of the amplifying transistor when deactivated, eliminating leakage and excess output voltage while maintaining low error vector magnitude.
Solution Approach 2:
The patent segments the amplifier into multiple common-source amplifying unit cells that can be independently activated or deactivated. Each unit cell has its own switching circuitry controlled by digital control signals, allowing selective activation based on the digital modulating signal amplitude. This segmentation enables precise control of gain while minimizing leakage from inactive cells.
2Productivity
If amplifying unit cells are activated or deactivated to achieve gain control, then digital gain modulation is achieved, but switching speed may be compromised
Solution Approach 1:
The patent changes the switching mechanism to control the source node voltage rather than drain or gate voltage. This parameter change enables faster switching because the source node switching directly controls the transistor's on/off state with minimal delay, achieving both fast gain control response and high switching speed suitable for digital modulating signals.
3Reliability
If source node switching is used to activate or deactivate amplifying unit cells, then leakage is reduced and linearity is improved, but device complexity increases
Solution Approach 1:
The patent implements a universal switching circuitry design that can be replicated for multiple common-source amplifying unit cells. Each unit cell uses the same switching topology with first and second switching elements controlling the source node, allowing modular expansion while maintaining consistent performance. This universal design approach manages complexity through standardization and replication.
Data Source
AI summary
A digital radio-frequency (RF) circuitry is disclosed. In one aspect, the circuitry includes a digitally controlled amplifier configured to receive an RF input signal and a digital control signal, and to output an amplitude controlled output signal. The digitally controlled amplifier includes one or more common-source amplifying unit cells. A respective common-source amplifying unit cell includes a sources node connected to a switching circuitry controllable by the digital control signal so as to activate or deactivate the common-source amplifying unit cell. The switching circuitry comprises a first switch configured to connect the source node with a first power supply node and a second switch configured to connect the source node with a second power supply node when activating and deactivating, respectively, the common-source amplifying unit cell.