A measurement of the reflection from and/or transmission through a material along with knowledge of its physical dimensions provides the information to characterize the permittivity and permeability of the material. Vector network analyzers such as the PNA family, ENA series and FieldFox make swept high frequency stimulus-response measurements from 9 kHz to 1.1 THz. (Figure 12). A vector network analyzer consists of a signal source, a receiver and a display (Figure 11). The source launches a signal at a single frequency to the material under test. The receiver is tuned to that frequency to detect the reflected and transmitted signals from the material. The measured response produces the magnitude and phase data at that frequency. The source is then stepped to the next frequency and the measurement is repeated to display the reflection and transmission measurement response as a function of frequency. More information on the network analyzer functioning and architecture is available in the application notes 1287-12 and 1287-23.
Simple components and connecting wires that perform well at low frequencies behave differently at high frequencies. At microwave frequencies wavelengths become small compared to the physical dimensions of the devices such that two closely spaced points can have a significant phase difference. Low frequency lumped-circuit element techniques must be replaced by transmission line theory to analyze the behavior of devices at higher frequencies. Additional high frequency effects such as radiation loss, dielectric loss and capacitive coupling make microwave circuits more complex and expensive. It is time consuming and costly to try to design a perfect microwave network analyzer.
Instead, a measurement calibration is used to eliminate the systematic (stable and repeatable) measurement errors caused by the imperfections of the system. Random errors due to noise, drift, or the environment (temperature, humidity, pressure) cannot be removed with a measurement calibration. This makes a microwave measurement susceptible to errors from small changes in the measurement system. These errors can be minimized by adopting good measurement practices, such as visually inspecting all connectors for dirt or damage and by minimizing any physical movement of the test port cables after a calibration. More information on the network analyzer calibration is available in the Application Note 1287-34.
Measurement System
Figure 11. Network analyzer
Receiver/detector
Processor/displayReflected(A)(B)Incident(R)SignalseparationSourceIncidentReflectedTransmittedTransmittedMUTFixture
วัดจากการสะท้อนหรือส่งผ่านวัสดุพร้อมด้วยความรู้ของมิติทางกายภาพให้ข้อมูลการอธิบายลักษณะ permittivity และซึมผ่านของวัสดุ เวกเตอร์วิเคราะห์เครือข่ายเช่นครอบครัว PNA ชุดเอนะ และ FieldFox ทำให้กวาดความถี่สูงตอบสนองกระตุ้นเศรษฐกิจวัดจาก 9 kHz ถึง 1.1 THz (12 รูป) การวิเคราะห์เครือข่ายเวกเตอร์ประกอบด้วยแหล่งสัญญาณ เครื่องรับสัญญาณ และแสดงผล (รูปที่ 11) แหล่งที่มาเปิดตัวสัญญาณที่ความถี่เดียววัสดุภายใต้การทดสอบ ตัวรับสัญญาณจะปรับไปที่ความถี่ในการตรวจสอบสัญญาณสะท้อน และส่งวัสดุ การตอบสนองที่วัดสร้างข้อมูลขนาดและเฟสที่ความถี่ที่ แหล่งที่มาแล้วก้าวเข้าความถี่ถัดไป และการประเมินซ้ำเพื่อแสดงการตอบสนองการวัดการสะท้อนและการส่งเป็นฟังก์ชันของความถี่ ข้อมูลเพิ่มเติมเกี่ยวกับการทำงานวิเคราะห์เครือข่ายและสถาปัตยกรรมมีการใช้งาน 1287 12 และ 1287-23Simple components and connecting wires that perform well at low frequencies behave differently at high frequencies. At microwave frequencies wavelengths become small compared to the physical dimensions of the devices such that two closely spaced points can have a significant phase difference. Low frequency lumped-circuit element techniques must be replaced by transmission line theory to analyze the behavior of devices at higher frequencies. Additional high frequency effects such as radiation loss, dielectric loss and capacitive coupling make microwave circuits more complex and expensive. It is time consuming and costly to try to design a perfect microwave network analyzer.Instead, a measurement calibration is used to eliminate the systematic (stable and repeatable) measurement errors caused by the imperfections of the system. Random errors due to noise, drift, or the environment (temperature, humidity, pressure) cannot be removed with a measurement calibration. This makes a microwave measurement susceptible to errors from small changes in the measurement system. These errors can be minimized by adopting good measurement practices, such as visually inspecting all connectors for dirt or damage and by minimizing any physical movement of the test port cables after a calibration. More information on the network analyzer calibration is available in the Application Note 1287-34.Measurement SystemFigure 11. Network analyzerReceiver/detectorProcessor/displayReflected(A)(B)Incident(R)SignalseparationSourceIncidentReflectedTransmittedTransmittedMUTFixture
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