What are the main lobe and side lobes in Beamforming?
You've probably noticed that in the diagram of beamforming, there are two types of lobes in beamforming patterns. One is the main lobe, while the others are side lobes. We intend to communicate with receivers with a stronger directional path from the transmitter when we produce beams for wireless communication. We can also see side lobes in this scenario. These side lobes, on the other hand, are not necessary for effective communication. As a result, we take various procedures to remove those side lobes or to reduce the number of side lobes as much as feasible; otherwise, inter-symbol interference occurs, and signal quality suffers.
In the case of MIMO antennas, our major goal is to reduce inter-symbol interface (ISI) by minimizing the number of side lobes, therefore we deploy antenna elements at half-wavelength intervals. It's a common practice to increase the power of the main lobe while reducing the power of the side lobes.
How to plot Main Lobes and Side lobes
The plotting of the main lobe and side lobes is not difficult. To begin, measure the received power at the receiver for a specific angle of arrival or departure (AOA/AOD).
For Example
At 28 GHz, UMi - LOS, 372-meter TX-RX Separation, Transmitted Power 30 dBm
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The received power changes with parameters like the angle of arrival at the receiver, as seen in the example above.
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What causes the lobes to form?
Further Reading
