The technology of ridged-waveguide filters provides high midband frequencies as well as the suppression of spurious passbands up until very high frequencies. Due to the concept of these filters, broad bandwidths lead to reduced filter dimensions that are very difficult to fabricate. The interdigital arrangement of resonators guarantees a more reliable fabrication of these filters. The research was done in order to supply filters for the different frequency bands in the 5G communication standard.

In near-field in situ measurements the antenna under test may not be accessed to use specifically tailored test signals. Instead there is a need to tackle modulated field signals where short-time measurement approaches offer a way to transform such fields using time-harmonic near- to far-field transformations. Short observation times make such approaches especially useful in measurement scenarios where unmanned aerial vehicles are used to move the field probe.

In the paper we describe how the detection of living objects, such as people and animals, can be significantly improved. It is particularly important to detect people in dangerous environments to protect them. For such a detection task we use a radar system. Radar, because the detection also has to work at night and if it rains or snows, these are the situations when other systems, i.e. cameras, fail. Our experiments showed that many radar applications can benefit from our approach.

In high-frequency technology, devices for filtering signals in the frequency domain are often based on resonant structures. As a result, the physical dimensions of a filter generally increase with decreasing frequency of operation. In this work, bandstop filters are built from special resonant elements with small physical dimensions to reduce the filter size. The small sizes result from the large permittivity of the used ceramic, increasing the electrical length of the resonant elements.

Near-field measurements are commonly performed in anechoic chambers which limits the flexibility and requires high precision equipment to achieve exact results. We investigate a simple near-field measurement setup that does not use a sophisticated positioning system nor does it operate in a controlled environment. Instead, the probe antenna is moved by an operator person while its position is measured by a laser tracker. Measurement results are shown to illustrate the performance of the system.