Dynamic Variable Attenuator for Magnetic Resonance Signal Waveform Control
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Solution Overview
Problem
Magnetic resonance measurement apparatuses face challenges in achieving a smooth amplitude waveform for transmission signals due to limited bit representation, leading to step-shaped waveforms and underutilization of D/A converter output resolution, with existing solutions failing to provide proper amplitude ratios between multiple transmission signals.
Innovation Solution
A magnetic resonance measurement apparatus incorporating multiple signal generators, a combiner, a digital-to-analog converter, and a dynamic variable attenuator, allowing for adjustable amplitude suppression of the combined analog signal, enabling dynamic control of the attenuation level during measurement to achieve desired amplitude ratios without initial amplitude setting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If amplitude ratio is set from the start in signal generation stage, then signal generation is simplified, but waveform becomes step-shaped and D/A converter output resolution cannot be fully utilized
Solution Approach 1:
The patent applies preliminary action by setting the amplitude ratio from the start in the signal generation stage. Multiple transmission signals are generated with predetermined amplitude ratios assigned, which simplifies the overall signal generation process. Although this initially seems to conflict with waveform smoothness, the patent resolves this by subsequently applying dynamic suppression to fine-tune the analog transmission signal, thereby maintaining both operational simplicity and waveform quality.
2Manufacturing precision
If amplitude ratio is adjusted after signal combination, then D/A converter output resolution is fully utilized, but additional control complexity is introduced
Solution Approach 1:
The patent applies dynamics by introducing a dynamic variable attenuator that can change the suppression level during measurement. This allows the amplitude ratio to be adjusted after signal combination, ensuring that the D/A converter output resolution is fully utilized and smooth waveforms are achieved. The dynamic control capability enables real-time optimization of signal characteristics without requiring complex pre-calculation of amplitude ratios.
3Adaptability or versatility
If dynamic suppression is applied to analog transmission signal, then amplitude ratio flexibility is improved, but frequency characteristic influence increases
Solution Approach 1:
The patent applies the intermediary principle by positioning the dynamic variable attenuator at a specific location in the signal chain - after the D/A converter but before the power amplifier. This intermediary position allows dynamic suppression to be applied to the analog transmission signal, providing amplitude ratio flexibility while minimizing the influence of frequency characteristics. The attenuator acts as a mediator that can adjust signal levels without being affected by the frequency-dependent characteristics of subsequent amplification stages.
Data Source
AI summary
In a magnetic resonance measurement apparatus, a plurality of transmission signals are combined to generate a digital combined signal. The digital combined signal is converted into an analog combined signal by a D/A converter. The signal includes, for example, a first pulse of a rectangular shape and a second pulse of a mountain shape. During measurement, an operation of a dynamic variable attenuator is changed immediately after the first pulse. With this process, the second pulse is suppressed, and a suppressed second pulse is generated.