Broadband RF Pulse Control with Gaussian Envelope Feedback
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Solution Overview
Problem
Existing high-power RF transmitters face efficiency losses due to control elements in series with the power supply, requiring significant cooling and limiting airborne applications above 500 W peak, and struggle to maintain RF pulse shape integrity across wide frequency bands and temperature ranges.
Innovation Solution
A device comprising an emitted pulse detector, analog and digital processing units to generate control signals for a Gaussian and square-shaped signal adder, utilizing digital potentiometers and LDMOS transistors to improve efficiency and maintain pulse integrity, with a servo-system for class C power stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If control elements are placed in series in the power supply of class C bipolar transistors to control peak power, then peak power control is achieved, but efficiency is reduced and excessive heating occurs
Solution Approach 1:
The invention divides the control function into separate segments: a modulation signal generator creates the Gaussian pulse envelope, while the power amplifier stage operates independently. This segmentation removes the series control elements that caused efficiency losses, allowing the amplifier to operate in its efficient class C mode while still achieving precise peak power control through the modulated input signal.
Solution Approach 2:
The invention applies preliminary action by pre-shaping the modulation signal to the desired Gaussian pulse envelope before it reaches the power amplifier. The modulation signal is prepared in advance with the correct amplitude and temporal characteristics, allowing the amplifier to simply follow this predetermined envelope without requiring series control elements that would reduce efficiency.
2Power
If series control elements are used for peak power control, then power regulation is achieved, but significant cooling means are required
Solution Approach 1:
By segmenting the control function from the power amplification function, the invention eliminates the series control elements that generated excessive heat. The modulation signal generator operates at low power and generates minimal heat, while the class C amplifier operates efficiently without series control losses, significantly reducing overall cooling requirements.
3Power
If class C bipolar transistor stages are used for high peak power, then peak power levels above 500W are achieved, but the charge rate must be kept below 1%
Solution Approach 1:
The invention changes the operating parameters by using a modulated input signal with Gaussian envelope shaping. This allows the class C amplifier to operate at higher charge rates (above 1%) because the modulation signal prepares the amplifier in advance, reducing the instantaneous power stress and allowing faster recharge cycles without compromising peak power output capability.
4Power
If conventional amplifiers are used, then amplification is achieved, but RF pulse shape integrity is difficult to control over wide frequency band and temperature range
Solution Approach 1:
The invention implements feedback by continuously monitoring the actual pulse envelope at the amplifier output and comparing it with the desired Gaussian reference envelope. The error signal is fed back to adjust the modulation signal, automatically compensating for frequency-dependent and temperature-dependent variations. This closed-loop control ensures pulse shape integrity is maintained across wide frequency bands and temperature ranges.
Solution Approach 2:
The invention dynamically adjusts operating parameters through the feedback loop, modifying the modulation signal characteristics in real-time to compensate for environmental variations. This allows the system to maintain consistent pulse shape integrity despite changes in frequency, temperature, or other operating conditions.
Data Source
Figure 1
Figure 2A~2B
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AI summary
The invention concerns a device for controlling parameters of a pulse of a high power RF pulse transmitter comprising at least one amplifier characterized in that it includes at least the following components: a transmitted pulse detector (4), a video amplifier (5), an analog processing device (6) adapted to supply data concerning the parameters of width and power of the transmitted pulse, a digital processing device (7) receiving the data concerning parameters of the transmitted pulse and adapted to generate the control signals to a device (8) adapted to generate a variable amplitude substantially Gaussian signal synchronized with the synchro transmission and to generate signals for controlling a device (9) adapted to generate a variable amplitude substantially square signal synchronized with the synchro transmission.