Microwave Power Amplifier With Lambda/4 Reflection Noise Cutoff
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Solution Overview
Problem
Current microwave power amplifiers for pulsed Electron Paramagnetic Resonance (EPR) systems are expensive, complex, and generate noise due to parasitic elements, leading to reduced sensitivity in measurements.
Innovation Solution
A microwave power amplifier arrangement using at least one transistor amplifier device and one switchable reflection device, where the switchable reflection device comprises a lambda/4 line connected to a PIN diode, allowing for control of microwave power flow to minimize noise by cutting off decaying power after a pulse, thereby reducing noise tails and maintaining high sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transistor amplifiers are used to provide amplified microwave pulses, then the device complexity and cost are reduced, but noise tails are generated that reduce measurement sensitivity
Solution Approach 1:
The harmful noise tail generated by the transistor amplifier is extracted and separated from the useful EPR signal by using a directional coupler to detect it and a delay line to shift its timing, allowing selective cancellation of the noise component while preserving the signal
Solution Approach 2:
An intermediary detection and cancellation system is introduced between the amplifier and the EPR measurement chain. The directional coupler acts as an intermediary to sample the noise tail, and a secondary signal path with delay and inversion acts as an intermediary to generate a canceling signal that neutralizes the noise
2Power
If transistor amplifiers with parasitic elements are used, then high power amplification is achieved, but unwanted noise is generated during the reception phase
Solution Approach 1:
The harmful noise tail generated by parasitic elements is converted into a useful cancellation signal. By detecting the noise tail through a directional coupler, delaying it to match the reception phase timing, and inverting its polarity, the previously harmful noise is transformed into a beneficial signal that actively cancels itself out, thereby reducing the noise floor and improving sensitivity
3Object-affected harmful factors
If longer delay time is used between pulse end and signal acquisition, then noise tail is reduced, but the frequency range that can be investigated is limited
Solution Approach 1:
The useful EPR signal acquisition is made continuous immediately after the microwave pulse ends by actively canceling the noise tail in real-time. Instead of introducing a dead time delay, the system continuously processes and cancels the noise as it occurs, allowing uninterrupted detection of the EPR signal across the full frequency range without gaps
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 provides amplified microwave pulses with reduced noise, enhancing the sensitivity of pulsed EPR measurements by eliminating noise tails and allowing for higher power amplification with faster switching speeds, suitable for high-power EPR experiments.
Implementation Method 1
a lambda/4 line, connected directly or indirectly to the transistor amplifier device output of at least one transistor amplifier device and to a first port of a PIN diode, with lambda being the wavelength of the microwave radiation within the lambda/4 line
Implementation Method 2
the PIN diode, with a second port of the PIN diode connected to ground
Data Source
Figure 1
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AI summary
A microwave power amplifier arrangement (1) for an electron paramagnetic resonance (=EPR) system (50), adapted for providing amplified microwave pulses of a microwave radiation having a microwave frequency MF in the X-band, with the microwave power amplifier arrangement (1) having a microwave input (2) and a microwave output (3), is characterized in that the microwave power amplifier arrangement (1) comprises - at least one transistor amplifier device (7-12; 35-38), and - at least one switchable reflection device (17-19; 39-42), wherein a respective transistor amplifier device (7-12; 35-38) comprises - a transistor amplifier device input (7a, 9a; 35a) directly or indirectly connected to the microwave input (2), - at least one transistor (7b, 9b; 35b), and - a transistor amplifier device output (7c, 9c; 35c) directly or indirectly connected to the microwave output (3), and wherein a respective switchable reflection device (17-19; 39-42) comprises - a lambda/4 line (17b; 39b), connected directly or indirectly to the transistor amplifier device output (7c, 9c; 35c) of at least one transistor amplifier device (7-12; 35-38) and to a first port (17f; 39f) of a PIN diode (17c; 39c), with lambda being the wavelength of the microwave radiation within the lambda/4 line (17b; 39b), and - the PIN diode (17c; 39c), with a second port (17g; 39g) of the PIN diode (17c; 39c) connected to ground (22). The inventive arrangement is simple in design, and can reduce noise.