CST系統級RS模擬（二）—— RS模擬場地較準（掃頻模式）

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根據IEC61000-4-3標準，RS測量時，要確保在距離天線3m處形成一個場強相對均勻的區域，如下圖所示。

The image is a diagram labeled "Figure 3 – Calibration of field." It illustrates the setup for calibrating an electromagnetic field in a chamber. Here are the key components depicted: Field generation antenna: Positioned on the left side, mounted on a stand. Isotropic field probe: Located on the right side, also mounted on a stand. Optional anechoic material: Placed in the center, used to reduce floor reflections in a semi-anechoic chamber. Uniform field area: Indicated by a dashed line, showing where the field is uniform. Chamber wall: Represented by solid lines, indicating the chamber boundaries. Fibre optic or filtered signal link: A cable connecting the isotropic field probe to an external device. Dimensions: The distance between the field generation antenna and the isotropic field probe is 3 meters, and the height of the isotropic field probe from the floor is 0.8 meters. This setup is crucial for ensuring accurate measurements in various scientific and engineering applications by calibrating the electromagnetic field.

較準時會選擇16個點，逐一進行測量。以10V/m的目標場強為例，只要其中12個點的場強達到10V/m以上，該場地即滿足要求。實際過程中，考慮調製後的訊號電壓伏值會變大1.8倍左右，擴大機有可能會出現過載現象。因此，場地較準時會使用更大的更大激勵訊號，模擬不用考慮這一點，這也是模擬的優勢。

The image is a diagram labeled "Figure 4 – Calibration of field, dimensions of the uniform field area." It shows a square area with sensor positions marked by black dots, which are equally spaced. The dimensions of the square are 1.5 meters by 1.5 meters. The sensors are positioned 0.5 meters apart along the edges and within the square. The distance from the floor to the bottom edge of the square is 0.8 meters. The diagram is used to illustrate the calibration of a field and the dimensions of the uniform field area. The text "IEC 032/06" is present at the bottom right corner of the image.

接下來我們透過CST建構一個RS測量場地，分別由天線、桌子、以及16個電場probe構成。RS場地較準模擬的目的，是確保目標區域的場強符合標準要求，我們需要得到連接埠激勵電壓和場強之間的關係，也就是天線係數－Antenna Factor。

The image shows a 3D simulation or model, likely related to computational electromagnetics or antenna design. The scene includes a coordinate system with grid lines, a structure resembling a table with four legs, and an array of arrows above the table, which could represent electromagnetic field vectors or radiation patterns. There is also a triangular element with a red tip and a blue base, connected by lines, which might represent an antenna or a similar device. The text 'element 1' is visible near the triangular element.

首先，利用CST時域求解器進行3D模擬，此處省略掉網格、求解器、邊界條件等重要設置，模擬後可得到天線的S參數、遠場方向圖、增益等常用結果。

The image is a graph showing the S-parameters (magnitude) of a system, specifically the S11 parameter. The x-axis represents the frequency in GHz, ranging from 0 to 1.2 GHz. The y-axis represents the magnitude in dB, ranging from -60 dB to 0 dB. The red line plot shows the variation of the S11 parameter with frequency. The graph indicates how the reflection coefficient (S11) changes across the frequency spectrum, which is relevant in analyzing the performance of RF and microwave components. The plot shows multiple peaks and dips, indicating the frequencies at which the system has significant reflections or minimal reflections.

RS測量有掃頻和單頻點干擾兩種模式，首先我們用CST來模擬掃頻的測量方式。進入CST的電路工作室，創建AC task，連接埠激勵電壓為1V，設定Combine Results。

The image shows a screenshot of a software interface, likely for circuit simulation or electromagnetic simulation, such as CST Studio Suite. The interface is divided into several sections: 1. Left Panel: Contains a hierarchical list with items such as 'Schematic,' 'Assembly,' 'Blocks,' 'External Ports,' 'Probes,' 'Tasks,' 'AC1,' and 'Results.' 2. Main Workspace: Displays a schematic diagram with a yellow block labeled '1' connected to another component on the right via a blue line. 3. Bottom Panel: Shows the 'Task Parameter List (AC1)' with tabs for 'AC,' 'Excitations,' 'Combine Results,' and 'Results.' The 'AC' tab is selected, displaying various simulation settings: - Circuit simulator: CST - Local units: (checkbox) - Simulation settings: - Maximum frequency range: (checkbox) - Fmin: 0 - Fmax: 1.2 - Samples: 10001 - Logarithmic sweep: (checkbox) 4. Right Panel: Contains the 'Result Navigator' with 'Schematic Run ID' and '0: Current Run.' This image is relevant as it provides a visual representation of setting up and configuring a simulation task in a specialized software environment, which is crucial for tasks such as designing and analyzing circuits or electromagnetic components.
The image shows a dialog box titled 'Define AC-Excitation,' used for setting parameters for an AC excitation source in a simulation or analysis software. The sections and options within the dialog box include: 1. Source: Voltage (selected), Current, Signal. 2. Signal import: Constant (selected), From file, From result. 3. Settings: Magnitude set to 1.0, Phase (Degree) set to 0. The dialog box also features three buttons at the bottom: OK, Cancel, Help.
The image shows a screenshot of a software interface, specifically from CST (Computer Simulation Technology) software. The interface is displaying the 'Task Parameter List' for a task labeled 'AC1'. There are several tabs visible at the top: 'AC', 'Excitations', 'Combine Results', and 'Results'. The 'Combine Results' tab is currently selected. The interface is divided into two main sections: 'Frequency limits' and 'Simulation'. Under 'Frequency limits': - Lower Limit: 0 - Upper Limit: 1.2 Under 'Simulation': - Combine Results: Checked - Block: MWSSCHEM1 - Label: AC1 - Use simulation task's: Checked - Select Monitors: (empty field) The image is relevant as it shows the configuration settings for a simulation task within the CST software, which is used for electromagnetic simulation and design.

透過CST場路協同模擬，我們得到了1V激勵條件下，在3m位置的E-probe上的場強，如下圖所示。整體來看，16個位置的波動在合理範圍內。

The image is a graph showing the magnitude of the electric field (in dBV/m) versus frequency (in GHz). The x-axis represents the frequency ranging from 0 to 2 GHz, and the y-axis represents the electric field magnitude ranging from -70 to 10 dBV/m. Multiple colored lines represent different data sets, each labeled with specific coordinates and values. The legend on the right side of the graph lists these data sets with labels such as 'E...(219.185 -198.166 -23866.1)(Abs) [AC1]' and similar variations with different coordinates and values. The graph is likely used to analyze the behavior of the electric field over a range of frequencies, which is relevant in fields such as electromagnetics and signal processing.

我們選擇其中一個E-probe的場強，作為計算天線係數AF的基準，因為激勵訊號的電壓是1V，因此這條曲線對應的值就是天線係數，單位1/m。

The image consists of two parts: 1. The left part of the image shows a 3D simulation model with several small arrow-like markers arranged in a grid pattern within a cubic space. One of the markers is highlighted with a red circle, and it is green in color. The bottom left corner of this part of the image has the text '3866.126919'. 2. The right part of the image is a graph titled 'Probe Value [Magnitude]'. The graph plots the Electric Field (dBv/m) on the y-axis against Frequency (GHz) on the x-axis. The x-axis ranges from 0 to 1 GHz, and the y-axis ranges from -100 to 0 dBv/m. The plot shows a blue line with several peaks and troughs, indicating the variation of the electric field magnitude with frequency.

接下來，關鍵問題來了，如果想得到10V/m的場強呢，我們該怎麼做呢？根據天線係數的定義：天線係數（ Antenna Factor ）也稱為天線因子，是指天線附近接收的電場強度與天線連接埠產生的電壓比值。我們只需要做一個簡單的數學計算，就能得到連接埠激勵電壓，如下圖所示。

A graph titled 'Port Signal [Magnitude]' that shows the magnitude of a port signal. The x-axis represents the frequency in GHz, ranging from 0 to 1 GHz. The y-axis represents the voltage in volts, ranging from 0 to 200 V. The graph is a plot of voltage versus frequency, with a green line indicating the magnitude of the port signal at different frequencies. The graph shows several peaks at specific frequencies, indicating higher voltage magnitudes at those points.

利用新產生的電壓訊號，設定成激勵源，重新運行AC task，在3m位置的E-probe上的場強變成了10V/m，如下圖所示。

The image consists of two parts: 1. The left part of the image shows a 3D simulation or model with several arrows pointing in different directions, likely representing the electric field vectors. There is a green arrow pointing upwards in the lower left part of the model. The model appears to be enclosed in a transparent box or boundary. 2. The right part of the image shows a graph titled 'Probe Value [Magnitude]'. The y-axis is labeled 'Electric Field / V/m' and ranges from 9.2 to 11. The x-axis is labeled 'Frequency / GHz' and ranges from 0 to 1. There is a blue horizontal line at approximately 10 V/m, indicating the magnitude of the electric field as a function of frequency.

完美！

下期我們將繼續介紹單頻點干擾模式校準，敬請期待。

原文轉載來自: 周明 – CST系统级RS仿真（二）——RS仿真场地较准（扫频模式）

系列文章：

CST系統級RS模擬（一）——天線建模
CST系統級RS模擬（二）—— RS模擬場地較準（掃頻模式）

看更多其他文章：

CST毫米波雷達模擬解決方案介紹（四）
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