When we check “Radiation Pattern File” in the Simulation Setup dialog, MGRID will invoke IE3D engine to simulate the structure and perform pattern calculation automatically. The pattern data will be saved into the .mpa and .pat files. The data saved into the .pat file is the pattern with the specified excitation. The data saved into the .mpa file is the general pattern. You are able to create the pattern file (.pat) for a specific excitation from a general pattern file.
Traditionally, pattern data is processed and visualized on PATTERNVIEW before version 14. If you have chosen Invoke MODUA in Post-Processing in the Simulation Setup dialog on IE3D 14, PATTERNVIEW will still be invoked to process the radiation pattern data.
On PATTERNVIEW, you are able to add a list of pattern files into the Pattern List window. Then, you can visualize and compare the data. In PATTERNVIEW 14, you can add either a general pattern file (.mpa) or a specific pattern file (.pat) into the list. If it is a specific pattern file (.pat), you will not be able to change the excitation. If it is a general pattern file (.mpa), you are allowed to change the excitation anytime you want.
In fact, all the functionalities of PATTERNVIEW are implemented into MGRID on IE3D 14. You are able to post-process and visualize radiation patterns on MGRID 14 completely. On both MGRID 14 and PATTERNVIEW 14, the primary pattern files are the general pattern files (*.mpa). You can add a number of pattern files into the Pattern List. If a pattern file is a general pattern, you can even change its excitation anytime you want. We may define excitations on ports for a particular structure. It is also possible we define plane wave excitation on the structure. The radiation properties of a structure can be quite different depending upon whether it is excited by ports or by plane waves. When we add a number of files into the Pattern List for comparison, we will need to make sure all of the files are excited by either ports or plane wave simultaneously. In the Pattern List of MGRID 14 and PATTERNVIEW 14, we will list the excitations of the patterns on the Pattern List.
Step 1 While you are opening the geometry file on MGRID, please select Windows->3D Radiation Pattern Display. The 3D Pattern Selection dialog comes up (see Figure 5.19). The rpatch2m.mpa file is automatically added into the list. In case you want to add more pattern files into the list, you can select Pattern List button to add more pattern files into the list. You can also access the pattern’s properties inside Pattern List.
Step 2 For this example, we just want to display the 3D pattern, please select the only file in the list.
Then, select No.3: 1.88 GHz from the frequency list. You will see the Max(dB) is updated to 4.7903 (see Figure 5.19). This is the maximum dB value of the selected field item. By default,
5-16 the selected field item is the dBi(Gain) of the E-total field. It means the maximum E-total field for dBi(Gain) is 4.7903 dB. Select OK. The 3D radiation pattern is displayed (see Figure 5.20).
Figure 5.19 The 3D Pattern Selection dialog.
Figure 5.20 The 3D radiation pattern.
5-17 On the 3D pattern display, there are 3 axes. Those are the axis for the three main angles: (Theta, Phi) = (0, 0), (90, 0) and (90, 90).
There are many parameters you can access in the 3D pattern display (see Figure 5.19). You can choose the 3D Pattern Quantity as: 3D Pattern, Axial Ratio, Radar Cross Section (RCS) and Normalized RCS. The RCS and normalized RCS are for plane-wave excitation only. Normalized RCS is defined by the ratio of RCS and the square of wavelength. The display in Figure 5.20 is for the 3D pattern case. In case you choose Axial Ratio, the display quantity will be the axial ratio in 3D form.
For the Polarization, it is E-total. You can choose E-theta for the theta-field, E-phi for the phi-field, E-left for left-hand circularly polarized phi-field, and E-right for right-hand circularly polarized field. The definitions are documented in Table AV.2 in Appendix AV. User can also rotate the theta and phi vectors on the (theta, phi) plane by an angle (see Figure 5.19). For such a case, the E-theta and E-phi are no longer the original theta and phi fields, but the theta and phi-fields after the rotation.
For the Scale Style, the default is dBi (Gain). It means we are displaying the gain of the antenna in dBi. dBi means 0 dB reference is the based upon an isotropic antenna pattern. You can choose dBi (Directivity) for displaying directivity in dBi, dB(Custom) for displaying the pattern with use specified dB(Custom) Base, Linear scale with the maximum at 1, Phase for the phase of the field, and dBi (Conj. Match Gain) for the gain based upon conjugate match. The standard gain definition is based upon the port impedance. For RFID applications, designers are not interested in the gain with matching to the port impedance. They are more interested in the antenna gain and efficiency based upon conjugate match. For this reason, we have defined Conjugate Match Efficiency and Conjugate Match Gain.
You may notice we do not use the terminologies of E-plane and H-plane patterns and Linear Gain. You may want to know how you can get those parameters. The answer is that we do not provide those parameters. The reason is due to the fact that IE3D is a general EM simulator.
You have the complete freedom to create any antenna structure you like and simulate it. IE3D does not know what the E-plane and H-plane of the antenna are because the planes are defined by the designers. We cannot provide such information. Instead, we provide the information about Total Field, Theta-Field, Phi-Field, LH Circular Field and RH Circular Field. If your antenna is linear polarized antenna, you can consider the Total Field or the Theta Field pattern as your primary radiation pattern while the Phi Field pattern as the cross-polarization. When it is circular polarized antenna, you should use either LH Circular Field or RH Circular Field as your primary polarization and the other one as the cross-polarization. Please note the following fact:
For a circular polarized antenna, the Total Field does not represent the linearly polarized field.
The pattern data for E-total is assuming all the fields (both E-theta and E-phi) are received completely.
There are many items in the Window menu of MGRID (see Figure 5.21a), allowing you to visualize different parameters of your structure. You can display the 2D patterns of the pattern on specified phi and/or theta angles. You can display the plot with gain vs. frequency etc.
Step 2 Select Window->Radiation Pattern Properties. MGRID will show you the Pattern List (see Figure 5.21b). You can add more files into the list for display and comparison purposes.
Step 3 Select the only pattern file in the list. Select the Properties dialog. The General Pattern Properties dialog will come up (see Figure 5.22a). In the dialog, you are able to change the excitations and terminations of the structure for each frequency point and post-process the
5-18 pattern. In case the selected pattern file in the Pattern List dialog is a pattern with specified excitation (*.pat), you will see the specified pattern properties shown in Figure 5.22b when you select the Properties dialog in the Pattern List.
(a) (b)
Figure 5.21 The Pattern List window.
(a) General Pattern Properties dialog. (b) Pattern Properties for specified excitations.
Figure 5.22The pattern properties dialogs for general pattern and pattern with specified excitations.
Step 4 Select “Display Detailed Pattern Properties” in the combo box (see Figure 5.22a). Select GO button. MGRID will show you the detailed pattern properties of the antenna in Pattern Properties dialog (see Figure 5.22b). Select View in Browser. MGRID will save the pattern properties data into an XML file and open a browser for it. There are many pattern parameters available in the dialog. The meanings of the parameters are documented in the Definitions dialog (see Figure 5.22b). They are also explained in the Appendix AV. We will not provide details here. The selected parameter parameters at selected frequency points are shown in Table 5.3.
The Input Power, Radiated Power, Radiation Efficiency, Directivity, etc. are for general antenna applications. The Antenna Efficiency and Gain have included the mis-match loss to a wave source. They are normally for microwave antenna applications. RFID are widely used nowadays.
For an RFID application, the source impedance is normally a voltage source with complex source impedance. For such applications, we should use the Conjugate Match Factor (CMF) and
5-19 Radiation Efficiency to judge how good the RFID antenna or system is. CMF with maximum value at 1 is a criterion on how good the antenna impedance and the source impedance conjugate matching. The CMF(dB) = 20 log10(CMF) is the measure of how much loss in the delivered power to the antenna due to impedance mis-match between the source and the antenna impedances. Please read Appendix BI for more discussion on RFID designs and CMF.
Table 5.3 The pattern parameters of the optimized antenna (rpatch2m.geo) at selected frequency points.
Freq (GHz) 1.7 1.88 2.00
Incident Power (mW) 10.0 10.0 10.0
Input Power (mW) 0.167323 9.99737 0.270496
Radiated Power (mW) 0.0406527 7.19081 0.00623073
Radiation Efficiency 24.296% 71.9269% 23.0344%
Antenna Efficiency 0..406527% 71.9081% 0.623073%
Conjugate Match Efficiency 12.148% 35.9635% 11.5172%
Voltage Source Efficiency 0.215649% 36.1751% 0.197646%
Conjugate Match Factor 0.0167323 0.999737 0.0270496
Total Gain (dBi) -17.9086 4.7903 -15.3823
Total Directivity (dBi) 6.00051 6.22253 6.67236
Conjugate Match Gain (dBi) -3.15445 1.78114 -2.8065
Theta Gain (dBi) -17.9086 4.7903 -15.3823
Theta Directivity (dBi) 6.00051 6.22252 6.67233
LH Circular Gain (dBi) -20.9113 1.77843 -18.3568
LH Circular Directivity (dBi) 2.99776 3.21165 3.69786
Step 5 Select OK twice until you get back to Pattern List dialog.
Step 6 Select “3D Pattern Visualization” at the bottom of Pattern List dialog and select “Go!”. MGRID will show you the 3D Pattern Selection dialog (Figure 5.19). Select the No.3 Freq = 1.88 GHz.
Select Pattern Style as “True 3D”. Select OK. MGRID will open a window and show you the
“True 3D” pattern (see Figure 5.20 and Figure BH.3a).
Step 7 You can select Windows->3D Radiation Pattern Display to access the dialog. Repeat Step 6 while you select the Pattern Style as “Mapped 3D”. MGRID will show you the “Mapped 3D”
pattern (see Figure BH.3b).
Step 8 You can either select Windows->2D Radiation Pattern->Define 2D Pattern Plot or select Windows->Radiation Pattern Properties->2D Pattern Visualization->Go to get into Define 2D Pattern Plots dialog (see Figure 5.23).
Step 9 Select Add Plot to bring up the 2D Pattern Display dialog (see Figure 5.24). You can scroll the list box to pick up any combination of theta and phi angles at any frequency. In case you have multiple files, you can also pick the items belonging to different pattern files. For this example, scroll to f = 1.88 GHz. Check the “E-Total at Phi = 0” and “E-Total at Phi = 90” (see Figure 5.24). The two cuts at Phi = 0 and Phi = 90 are the two major cut planes for the pattern. Select Pattern Style as “Polar Plot”. Select OK to finish defining the plot and it is added into the list of plots.
Step 10 Select Add Plot again. Select the same items “E-Total at Phi =0” and “E-Total at Phi=90” at f = 1.88 GHz. However, please choose the Pattern Style as “Cartesian Plot”. Select OK to add the plot into the list.
5-20 Step 11 Select Continue and the two defined plots will be displayed on MGRID. We will have four windows showing the pattern in the forms of “True 3D” , “Mapped 3D”, “Polar Plot” and
“Cartesian Plot” (see Figure BH.3). They are representing the same data but in different forms to you. For the differences between the four forms, please read Appendix BH.
Figure 5.23 The Define 2D Pattern Plots dialog.
5-21 Figure 5.24 The 2D Pattern Display dialog.
Step 12 Select Windows->Gain Vs. Frequency Display. MGRID will prompt you the Frequency Respond Display dialog. Check the item: Phi = 0 and Theta(1) with Theta = 0 degree (see Figure 5.25). Select OK. MGRID will open a window to display the Gain Vs. Frequency with gain at Theta = 0 and Phi = 0 (see Figure 5.25). There are many other visualization capabilities.
We will not explain all of them here. Please check the Windows menu.
Again, pattern visualization and processing used to be on PATTERNVIEW. For the convenience of users, we have transferred all the functionalities into MGRID. You can do the same procedures on PATTERNVIEW. You only need the general pattern files (.mpa) and/or the specific pattern files (.pat) on PATTERNVIEW.
Figure 5.25 The Total Field Gain Vs. Frequency plot.