 Hey everybody, it's Tossos with RF Elements and today we'll be talking about the frequency dependence of antenna patterns. In the world of RF engineering, the vast majority of parameters are frequency dependent and every RF device has properties that are changing with frequency. This is why very often the answer to RF related question is, it depends. Understanding the simple and sometimes very complicated facts is what RF engineers are paid for. Let's have a look at how frequency influences the properties of an antenna. The gain of an antenna in a data sheet is usually a single number, which is a peak gain at a particular frequency which is rarely disclosed. The truth is, the gain of an antenna changes with frequency and with angle. Describing gain as a single figure is just not enough. Back in time, when computers were weak, scientists displayed gain in two-dimensional polar plots because they are easy to draw on paper. Today, 3D radiation diagrams are easy to produce and should be used because they provide a more complete picture about gain. Radiation diagrams also change with frequency. The shape and size of any antenna are usually fixed, but the wavelength of the feeding signal changes with frequency, which influences the radiation diagram. Some antennas like patch arrays are more prone to these design changes, while others like horn antennas are much more stable. So why is stability of gain and radiation diagrams important? Again, it depends. Some antennas are used in a narrow bandwidth, so the frequency stability is not as important because most common antennas have stable performance over narrow frequency ranges. It is fairly easy to design a narrow-band antenna. To achieve stable performance over a wide bandwidth is a real challenge, especially if you want an antenna that has a stable peak gain and the rest of the radiation diagram simultaneously. In wireless networking, for example, wideband performance, stability of gain, and radiation patterns of sector antennas are really important because the quality of delivered services directly depends on these parameters. For more interesting topics on RF and antennas, check out our future videos. Thank you.