DC Amplifier Negative Feedback for High-Frequency Measurement
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Solution Overview
Problem
Existing measuring devices for high-frequency signals face complexity due to parallel measurement branches, difficulty in synchronizing choppers and analog/digital converters, and significant temperature dependence of transfer characteristics, particularly at high video bandwidths like 30 MHz, which affects noise and dynamic range compression.
Innovation Solution
A DC voltage amplifier with negative feedback paths using detector elements to create a symmetrical feedback loop, where detector diodes in anti-parallel configurations reduce thermal drift and 1/f noise, and a differential amplifier design with chopper switching to invert signal inputs for each chop phase, ensuring balanced feedback and reduced temperature dependence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If parallel measuring branches are used to cover large dynamic range, then measurement capability is improved, but device complexity increases significantly
Solution Approach 1:
The patent combines multiple measuring branches into a single measuring path by using a switching mechanism that sequentially connects different detector elements to the same amplifier and evaluation unit. This merging approach maintains the ability to measure across a large dynamic range while significantly reducing the complexity of having multiple parallel branches simultaneously active.
Solution Approach 2:
The patent introduces dynamic switching between different detector elements based on the signal level being measured. The switching mechanism dynamically selects appropriate detector elements for the current measurement range, allowing the system to adapt to different dynamic ranges without requiring all branches to be permanently connected and synchronized.
2Adaptability or versatility
If multiple synchronized choppers and analog/digital converters are used in parallel branches, then measurement capability is improved, but synchronization difficulty increases
Solution Approach 1:
The patent merges the functions of multiple choppers and analog/digital converters into a single shared evaluation unit. By using one converter that processes signals from different detector elements sequentially through switching, the system eliminates the need for multiple synchronized converters and their associated synchronization complexity.
Solution Approach 2:
The evaluation unit is designed to be universal, handling signals from different detector elements through the switching mechanism. This single multi-functional unit replaces multiple specialized components, reducing synchronization requirements while maintaining full measurement capability across different signal ranges.
3Measurement precision
If detector diodes are used for detection, then detection capability is improved, but temperature dependence of transfer characteristic increases
Solution Approach 1:
The patent uses anti-parallel detector diodes where one diode is forward-biased while the other is reverse-biased during each half-cycle. The reverse-biased diode experiences similar temperature effects but in opposite polarity, allowing the differential amplifier to reject temperature-induced drifts as common-mode signals, thereby compensating for temperature dependence.
Solution Approach 2:
The differential amplifier configuration provides inherent feedback where the output is influenced by the difference between the two detector diode outputs. This feedback mechanism automatically compensates for temperature drift by maintaining the difference signal while rejecting common temperature effects on both diodes.
4Device complexity
If single-path implementation is used to reduce complexity, then device complexity is reduced, but dynamic range compression becomes insufficient
Solution Approach 1:
The patent implements dynamic range compression capability in a single path by using a switching mechanism that sequentially connects different detector elements with different sensitivity levels to the same amplifier. This dynamic switching allows the system to compress a wide dynamic range through a single measurement path, maintaining adaptability while reducing complexity.
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 results in a measuring device with reduced noise influence and low temperature dependence of the transfer characteristic, enhancing signal-to-noise ratio and dynamic range compression, while simplifying the design by eliminating the need for precise synchronization of measurement branches.
Implementation Method 1
The detector has two detector elements. This is particularly advantageous when using detector diodes, which are arranged in the detector with reversed polarity and then each detect a half-wave of the high-frequency input signal in the sense of a full-wave rectification.
Implementation Method 2
The chopper (chopper) is designed as a changeover switch which connects the first detector element or the first detector diode to the first input of the DC voltage amplifier during a first chop phase and the second detector element or the second detector diode to the first input of the DC voltage amplifier
Implementation Method 3
it is proposed to provide the DC voltage amplifier with negative feedback paths, which each connect an output to an input and in each of which there is a further detector element. In this way a negative feedback is created which has similar characteristics as the detector
Implementation Method 4
The DC voltage amplifier is preferably designed as a differential amplifier and amplifies a differential input voltage between its two inputs to form a differential output voltage between its two outputs.
Data Source
AI summary
The invention relates to a measuring device comprising a detector (2) equipped with at least one detector element (22; 23) and one DC amplifier (24) mounted downstream from the detector, at least one inlet (52; 53) and at least one outlet (54; 55). Said DC amplifier (24) comprises at least one counter-coupling path (56; 57) which extends from its at least one outlet (54; 55) to its at least one inlet (52; 53). At least one additional detector element (45 - 48) is arranged in the counter-coupling path (56; 57).