Pulsed RF Amplifier Peak Power Control Without Switch Losses
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Solution Overview
Problem
Existing power control methods for pulsed RF transmitters face challenges such as power switch losses, overpowered amplifiers, difficulty in maintaining identical gain for multiple power levels, especially in broadband amplifiers, and limited power variation dynamics.
Innovation Solution
A device and method that utilize a pre-modulation stage with a first amplifier controlled by a digital signal and a second amplifier with variable gain, along with a power-slaved stage for precise control of peak power levels, ensuring stable performance across frequencies and temperatures, and reducing dimensions and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power switch is added at the output of the transmitter to control power levels, then power reduction is achieved, but power switch losses increase and the power amplifier must operate at maximum power continuously
Solution Approach 1:
The invention applies preliminary action by controlling the power amplifier's operating state before signal transmission. The microcontroller adjusts the bias voltage and supply voltage to the power amplifier in advance, setting it to operate at the appropriate power level (normal or reduced) before the actual signal is amplified, thereby avoiding the need for power switches and their associated losses.
Solution Approach 2:
The invention replaces the mechanical/electrical power switch system with an electronic control system. Instead of using a power switch to physically interrupt or attenuate the signal path, the system uses a microcontroller to electronically adjust the power amplifier's operating parameters (bias voltage, supply voltage), substituting a control electronics approach for a switching approach.
2Power
If the power amplifier is designed to operate at maximum power continuously, then power reduction can be achieved via switching, but the amplifier is overpowered and losses increase
Solution Approach 1:
The invention applies dynamics by making the power amplifier's operating state variable rather than fixed. The microcontroller dynamically adjusts the bias voltage and supply voltage to the power amplifier based on the required power level, allowing the amplifier to adapt its operating point between normal power and reduced power modes, optimizing efficiency across different power requirements.
Solution Approach 2:
The invention changes the operating parameters of the power amplifier (bias voltage, supply voltage, operating point) based on the required power level. By adjusting these parameters, the amplifier can operate efficiently at either normal power or reduced power without being overpowered, thereby minimizing energy losses while maintaining the capability to deliver maximum power when needed.
3Power
If discrete control signals are used to switch between power levels, then power variation is achieved, but the layout must accommodate attenuators and the gain consistency across stages becomes difficult to guarantee
Solution Approach 1:
The invention extracts and removes the attenuator components from the signal path. Instead of using discrete attenuators to achieve power reduction, the system controls the power amplifier's operating state directly through voltage control, eliminating the need for separate attenuator stages and their associated layout complexity and gain consistency issues.
Solution Approach 2:
The microcontroller serves multiple functions: it generates the modulation signal, controls the bias voltage, adjusts the supply voltage, and manages the power amplifier's operating state. This multi-functional approach consolidates what would otherwise require separate discrete control circuits and attenuators, simplifying the overall device architecture while maintaining power variation capability.
Data Source
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AI summary
The invention concerns a device for controlling at least 2 peak power levels for an amplifier operating in pulsed mode characterized in that it comprises at least the following elements: a pre-modulation stage including at least: a first amplifier stage, comprising at least one amplifier (1) and a processing device (6) adapted to supply a square signal to the amplifier (1), a second amplifier stage, comprising at least one amplifier (7) and a processing device (9) adapted to supply a signal having a shape substantially identical to the applied modulation, a power-dependent stage comprising at least one coupler and detector (11) to sample at least part of the signal output from the amplifying chain and transmit same to a video amplifier (22), a peak detector (24) and a level discriminator (25) adapted to generate a modulation signal to an amplifier (20), means for powering (21, 22, 23) the amplifiers.