The "Active Impedance" graph will update slightly as each radiator couples to others. The isolation resistor in the Wilkinson feed networks helps mitigate the different impedances seen by each patch as the array is steered. If you change the "Global Definition" Riso to a large number, such as , there is no longer isolation between each path of the Wilkinson and the impedances of the individual patches will vary much more. Note that these are essentially calculated by the closed form formula inserted in the schematic "Module".
Observe that in the array EM structure, the centers of the adjacent array elements are separated by mils along both x and y. Global variables "XPos" and "YPos" are two linear arrays both with a step size of These are used to determine the magnitude and phase of port excitations so as to steer the main lobe.
Exact origin of the coordinate system is not important. Shifting the origin would move the phases of all port signals uniformly by the same amount. Due to symmetry, coupling between ports 1 and 2 should be very close to that between ports 13 and There are some difference between the S-parameters as shown in this graph. Consequently, the active impedances shown in graph 5 also lack the expected symmetry.
Rerunning the simulation would cause the corresponding pair of curves to overlap with each other. The "Manifold" schematic then builds up the single divider into a 4 way divider. The "Module" schematic uses values defined in the "Global Definitions" document as well as patch position row and column passed into the schematic from the higher levels of hierarchy to calculate the phase and attenuation needed to feed each patch element. View the global definitions to see which values are defined there and then view the "Module" schematic to see the equations to calculate the phase and attenuation.
The procedure for requesting AWR support has changed. Please read all about the new AWR product support process. The dielectric substrate is defined to have at least five FDTD cells of thickness using the Poor Conductor minimum feature size setting.
The overall number of cells per wavelength is set to 60 to ensure good results. The input for the element is a voltage source which is initially excited by a broadband signal covering from 26 to 30 GHz for S-parameter results. Following a simulation for computing the S-parameters, the return loss is found to have a weak response due to a poor match. This is corrected by adding a matching circuit consisting of a series inductor and parallel capacitor 0.
The matched input return loss produces a null near 28 GHz Figure 2. The far field gain pattern for the single element Figure 3 indicates a strong central lobe normal to the patches with peak gain of The peak side lobe is seen to be down about 13 dBi from the main lobe as shown in Figure 4.
Figure 2: The Return Loss for the 1x8 element is slightly out of tune when fed with a ohm source. By adding a simple LC matching circuit, the device is tuned to 28 GHz. Figure 3: The far-field gain pattern of the1x8 element has a strong central beam that is focused in one dimension and circular in other.
The peak gain is just under 17 dBi. Figure 4: In the XZ dimension E-plane the antenna pattern has main beam with gain of To create the array, eight of the single 1x8 elements are spaced 5. To generate broadband S-parameter data, a pulse excitation is applied to each of the eight input ports.
A matching circuit similar to that used for the single element is applied to all input ports of the array. The return loss for all eight ports is seen to be very similar as shown in Figure 6, while the isolation between adjacent ports is below dB for each Figure 7. Figure 5: Shown is a CAD representation of the combination of eight of the 1x8 elements into an array.
The elements are spaced 5. Figure 7: The isolation between adjacent ports is shown to be less the dB for all possible combinations. Figure 8: The gain pattern for the array when all inputs are fed in phase results in a strong central beam with gain of 24 dBi. Depending on the phasing of the signals at each of the input ports, a number of different beams may be defined. When all ports are fed in phase, the beam normal to the array plane is formed with the maximum gain of 24 dBi Figure 8.
Due to the nature of this geometry the beams may only be steered in one plane, parallel to the line of input ports. To adjust the phasing, the Butler Matrix equation is used to compute the inter-element phase difference. It is defined as:. In this case, the phasing for beams is The phase shift is applied across the input ports, so the first port will have a shift of 0 deg, the second These phase shifts are applied with a sinusoidal input at 28 GHz. In three dimensions, beams 1 through 4 may be seen in Figures 10 - All eight beams are shown in one three-dimensional image in Figure Figure 9: After applying Butler Matrix phase shifts to each port, a directed beam is formed.
Shown are eight possible beams. Figure The gain pattern formed from the Butler Matrix phasing for beam 1 Figure The gain pattern formed from the Butler Matrix phasing for beam 2 The white arrow indicates the direction of the peak gain.
Figure The gain pattern formed from the Butler Matrix phasing for beam 3 Figure The gain pattern formed from the Butler Matrix phasing for beam 4 Figure Shown is a side view of the eight beams produced by the Butler Matrix phasing equation.
Each beam represents a separate simulation. This array has been shown to form eight beams with the Butler Matrix phasing; however, a further analysis of the total gain over all possible phasing combinations is possible by computing the Cumulative Distribution Function of the Effective Isotropic Radiated Power.
This plot shows the fractional area of the three-dimensional far-field sphere that the array covers for a given amount of input power. The upper hemisphere of the far zone region is scanned by the beams in only one axis due to the design of the array, so therefore the scanned region is relatively limited.
The plot also shows that the peak EIRP is about As an alternative to using the Butler Matrix equations and adjusting the phases in the software, it is also possible to use a true time delay device such as a Rotman Lens in the simulation to form the beams with this array.
0コメント