Radiometer Error Reduction via Switched Reference Signal
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Solution Overview
Problem
Microwave temperature sensing systems face errors due to signal attenuation and other external factors as the temperature signal is transmitted through cables, leading to unreliable temperature calculations.
Innovation Solution
A temperature sensing system is designed with a switch positioned between the antenna and the cable, where both the temperature signal and a reference signal are conveyed along the same conductive element, allowing signal-altering events to affect both signals equally, thereby eliminating measurement errors through differential processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the antenna is located remotely from the radiometer and connected by a cable, then the system is easier to operate and more flexible in placement, but signal attenuation and cable temperature changes introduce measurement errors
Solution Approach 1:
A switch is introduced as an intermediary component between the antenna and the radiometer. This switch has two inputs: one receiving the temperature signal from the antenna, and another receiving a reference signal from a termination. The switch alternately connects these inputs to the cable, allowing both signals to experience the same cable conditions (temperature, attenuation) at different times, thereby enabling error compensation.
Solution Approach 2:
The switch operates periodically, alternately connecting the temperature signal and the reference signal to the cable at predetermined time intervals. This periodic switching ensures that both signals are subjected to the same cable environment conditions sequentially, allowing the radiometer to measure and compare both signals under identical cable loss and temperature conditions, thus compensating for cable-induced errors.
2Measurement precision
If the termination is located at the switch rather than remotely, then the reference signal experiences the same cable conditions as the temperature signal, but the device complexity increases
Solution Approach 1:
The switch merges the temperature signal path and the reference signal path into a single cable connection. By using one cable to carry both signals sequentially (through periodic switching), the system eliminates the need for separate cable connections for the termination, thereby reducing overall system complexity while still achieving the goal of having both signals experience identical cable conditions.
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
This approach significantly reduces the need for error correction in temperature calculations by ensuring that signal-altering events, such as loss and cable temperature changes, equally impact both the temperature and reference signals, resulting in more accurate temperature measurements.
Implementation Method 1
The antenna receives microwaves of one or more (e.g., a range of, etc.) selected frequencies from a targeted source, which microwaves are indicative of temperature of the source. The antenna then generates a signal—a 'temperature signal'—that corresponds to the intensity of microwaves received by the antenna
Implementation Method 2
One of the factors that may undesirably alter the temperature signal is signal attenuation, which is commonly referred to as 'loss,' which may occur as the temperature signal is transmitted along a conductive element, such the conductive element of a cable
Data Source
AI summary
Apparatuses and systems for determining a temperature of a targeted subject are disclosed. A temperature sensing system may include an antenna for sensing electromagnetic radiation (e.g., microwaves, etc.) emanating from the source. Based on that electromagnetic radiation, the antenna generates a temperature signal. A switch, which is located at or adjacent to an output of the antenna, receives the temperature signal, as well as a reference signal from a termination. The temperature signal and the reference signal are conveyed along a cable to a signal converter. Signal-altering events that affect the temperature signal as it is conveyed also affect the reference signal. Thus, any error caused by a signal-altering event automatically cancels out. The signal converter measures or otherwise processes the temperature signal and, since there is no need to correct for errors in the temperature signal, the reference signal, and accurately calculates the temperature of the source.