RF Pulse Amplifier Supply Regulation to Prevent Power Droop
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Solution Overview
Problem
Existing RF pulse amplifiers face challenges in maintaining stable RF output power due to voltage droop during peak power delivery, particularly with LDMOS and GaN transistor technologies, leading to increased cost and volume requirements for energy storage devices.
Innovation Solution
A switched DC/DC converter is used to continuously control the supply voltage to a predetermined value by stepping down the DC bus voltage, operating independently of DC link variations, thereby preventing RF power droop and allowing for smaller energy storage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large energy buffer is used to deliver peak power, then the peak power delivery capability is improved, but the voltage droop during pulse generation worsens
Solution Approach 1:
A DC/DC converter is introduced as an intermediary between the energy buffer and the RF amplifier. This converter actively regulates the supply voltage to the amplifier, decoupling the voltage stability from the energy buffer's depletion rate. The converter acts as a mediator that transforms the unstable voltage from the discharging capacitor into a stable regulated voltage for the amplifier.
Solution Approach 2:
The system changes the operating parameters by using a DC/DC converter to dynamically adjust and maintain the supply voltage at a predetermined level despite changes in the energy buffer voltage. This parameter regulation ensures that the amplifier receives constant voltage while the energy buffer depletes during pulse generation.
2Device complexity
If the energy buffer is simply attached to the amplifier, then the device complexity is reduced, but the RF power droop increases
Solution Approach 1:
The DC/DC converter serves as an intermediary component that, while adding to device complexity, prevents RF power droop by actively regulating the supply voltage. This intermediary ensures reliable and stable RF power output during pulse generation, justifying the additional complexity.
3Temperature
If LDMOS transistor technology is used, then the supply voltage is reduced to 50V, but the supply current increases significantly
Solution Approach 1:
The energy buffer is pre-charged to a high voltage (e.g., 400V) before pulse generation. During the pulse, the buffer depletes, and the DC/DC converter maintains the amplifier supply voltage. This preliminary charging allows the system to deliver high peak power with reduced supply current from the mains during operation.
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
The solution maintains stable RF output power while reducing the size and cost of the energy storage device, achieving high performance with minimal volume and cost.
Implementation Method 1
The DC/DC converter is configured to step down the DC bus voltage (supplied at the converter input) to the supply voltage (applied to the converter output)
Data Source
AI summary
An RF pulse amplifying device includes an amplifier configured to amplify a pulsed RF signal, a DC link configured to supply a DC bus voltage, and an energy storage device connected to the DC link. The amplifier has an input for receiving a supply voltage. The input of the amplifier is connected to the DC link through a switched DC/DC converter, which is configured to step down the DC bus voltage, supplied at the converter input, to the supply voltage, applied to the converter output. A control unit is configured to operate the switched DC/DC converter during amplification of the RF pulse to control the supply voltage at a predetermined value.