Simulation of RF Systems with Antenna Blocks
Use the Antenna block to incorporate the effect of an antenna into an RF simulation. In this model, a single tone is fed to the transmitter and the power of the received signal at the output of the receiver is calculated.
Set the Antenna_TX and Antenna_RX blocks to be isotropic radiators with the following parameters:
The following values are set upon loading the model:
56.2947 - 4.2629i[Ohm]
where the antenna gains and impedances were calculated beforehand from dipoles backed by circular reflectors.
With Antenna Toolbox™, it is possible to design the antenna using the Antenna Designer app invoked directly from the block. To do so, change the choice of Source of the antenna model to Antenna Designer and press the Create antenna button. Within the
Antenna Designer app, create a new antenna, choose Dipole from the Antenna Gallery , Circular from the
Backing Structure Gallery in the app toolstrip and select Accept. Note that the design frequency was prepopulated with the RF system frequency of 5 GHz.
Select the Impedance button in the app toolstrip to analyze the structure and select the Update Block button to update the block with the chosen antenna. Note that the Antenna block requires that the designed antenna be analyzed for at least one frequency in the Antenna Designer app before updating and using it in the block.
In the Antenna_TX block mask parameter dialog box, change the default Direction of departure to
0 degrees in azimuth and
90 degrees in elevation:
Repeat the above steps to design Antenna_RX. However, the receiving antenna needs to be rotated to face the transmitting antenna. To do so, in the Antenna Properties panel of the Antenna Designer app, set Tilt to
180 degrees. Again, select the Impedance button and then press the Update Block button to update the block. In the Antenna_RX block mask parameter dialog box, change the Direction of arrival to
180 degrees in azimuth and
-90 degrees in elevation. – 90-degree elevation is chosen since the radiated signal that was transmitted in the positive z direction in the coordinate system of the transmitter, is now arriving from the negative z direction in the coordinate system of the receiver. Azimuth is set to 180 degrees to align vector fields of the transmitter and receiver antennas.
Run the model again, and note that the output power remained almost exactly the same. This is since the original gain and impedance values used for the isotropically radiating antenna in the beginning were calculated from the same antennas and spatial settings. However, it is now possible to change the antenna properties and observe the effect on the output power in the model. For example: Select the 'Edit Antenna' button in the Antenna_TX block mask parameter dialog box to reopen the Antenna Designer app. In the Antenna Properties panel of the Antenna Designer app, change Tilt to
30 degrees and the TiltAxis to
[0 1 0]. Select the Impedance button and then press the Update Block button to update the block. Rerun the model to observe reduction of 2.5 dB in the output received power due to the mismatch in antenna orientation.