Passive SAW Sensor Frequency Shift for Signal Isolation
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Solution Overview
Problem
The existing methods for controlling passive sensor elements, such as SAW resonators, face challenges in effectively receiving and evaluating weak response signals due to the shared use of electronic elements for excitation and reception, with the response signal being 60 dB below the excitation signal in power, making it difficult to achieve accurate measurements, especially under demanding conditions.
Innovation Solution
The method involves adjusting the frequency of the transmitter unit during the transition from the transmission to the reception period, utilizing the filter properties of the receiving unit to achieve a predetermined attenuation value, thereby enhancing the reception properties by increasing the damping effect of the switch element, which is more than 40 dB with typical intermediate frequency filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common antenna is shared between transmitter and receiver units, then device complexity is reduced, but the receiver cannot effectively distinguish the weak response signal from the strong excitation signal due to insufficient attenuation
Solution Approach 1:
The patent changes the frequency parameter of the transmitter unit during the transition from transmission to reception mode. By adjusting the transmitter frequency away from the resonant frequency, the excitation signal no longer overlaps with the response signal frequency, enabling the receiver to effectively filter and evaluate the weak response signal even when sharing a common antenna.
2Ease of manufacture
If the response signal level is 60 dB below the excitation signal, then the measurement system can operate with simple components, but accurate measurement becomes difficult due to the weak signal level
Solution Approach 1:
The patent employs frequency parameter adjustment of the transmitter unit to resolve the signal level discrepancy. By shifting the transmitter frequency during reception mode, the system creates a frequency separation between the excitation and response signals, allowing the receiver to selectively amplify and evaluate the weak response signal while rejecting the strong excitation signal through standard filtering techniques.
3Device complexity
If the transmitter and receiver units share common electronic elements, then device complexity is reduced, but the transition from transmission to reception mode creates interference that degrades signal quality
Solution Approach 1:
The patent implements dynamic frequency parameter adjustment of the transmitter unit during mode transition. This frequency shifting creates a temporal and spectral separation between transmission and reception operations, allowing the shared electronic elements to function reliably in both modes without significant interference, thereby maintaining signal reception reliability while preserving device simplicity.
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 improves the reception properties of the measurement system, allowing for accurate temperature and pressure measurements in harsh environments, such as in endless pressed goods, by ensuring effective signal evaluation within the short duration of the response signal.
Implementation Method 1
the limited insulating effect of the switch element can be significantly improved by the filter properties of the receiving unit
Implementation Method 2
When the frequency of the transmitting unit is adjusted by an amount that is greater than half the bandwidth of an intermediate frequency filter of a demodulator unit of the receiving unit, an attenuation value of more than 40 dB is achieved with typical intermediate frequency filters
Implementation Method 3
When used as SAW sensors, the dependency of the surface wave speed on the mechanical stress (deformation), the impact of mass (deposits on the surface) or the temperature (temperature coefficient of the speed of sound) is used
Data Source
Figure 1~2
AI summary
The invention relates to a method for activating passive sensor elements, in particular of surface wave resonators, in which an activating circuit with a transmitting unit for emitting an excitation signal and with a receiving unit for receiving and evaluating the response signal of the sensor is provided, and wherein the transmitting unit and the receiving unit have a common antenna, which is connected by means of a switch element to the transmitting unit during a transmitting time period and to the receiving unit during a receiving time period, characterized in that, during the changeover from the transmitting time period to the receiving time period, there is in addition to the switching over of the antenna also an adjustment of the frequency of the transmitting unit.