Interview

Abstract

Dr Saeid Karamzadeh at Istanbul Aydin University, Turkey, talks to Electronics Letters about the work behind his Letter ‘Millimeter-Wave High-Gain Circularly polarised SIW End-Fire Bow-tie Antenna by utilising Semi Planar Helix Unit Cell’, page 411. Saeid Karamzadeh Years ago, during the design of a system to rescue living people left under earthquake rubble, we found that the antenna is one of the most important parts of the system and should be studied in more detail. The next step was designing an antenna for satellite communication. Size reduction, designing a compact antenna, bandwidth improvement, gain increment and getting circularly polarisation were our goals. In the meantime, I finished my PHD degree and I won the most successful PHD thesis award of Istanbul Technical University. Recently, as mm-wave circularly polarised antennas have many benefits, we focused on designing novel works on this subject. One of the important issues is generation of circular polarisation from a linearly polarised antenna. Identifying linearly polarised antennas that have the ability to change to antennas with circularly polarised features and realising the methods for this is a challenge for antenna designers. Circularly polarised antennas have several important advantages compared to antennas using linear polarisation and are becoming a key technology for various wireless systems. Circularly polarised antennas are very effective in combating multi-path interferences or fading. The reflected radio signal from the ground or other objects will result in a reversal of polarisation, that is, right-hand circular polarisation (RHCP) reflections show left-hand circular polarisation (LHCP). An RHCP antenna will have a rejection of a reflected signal which is LHCP, thus reducing the multi-path interferences from the reflected signals. The second advantage is that a circularly polarised antenna is able to reduce the ‘Faraday rotation’ effect due to the ionosphere. The Faraday rotation effect causes a significant signal loss (about 3 dB or more) if linearly polarised signals are employed. Another advantage of using CP antennas is that no strict orientation between transmitting and receiving antennas is required. This is different from linearly polarised antennas, which are subject to polarisation mismatch losses if arbitrary polarisation misalignment occurs between transmitting and receiving antennas. We managed to create a circularly polarised antenna on a mm-wave linear polarisation antenna by employing several spiral unit cells. This is helpful because linear polarisation antennas have few limitation parameters, therefore designing them is relatively simple compared with circularly polarised antennas and by this method we can convert linearly polarised to circularly polarised antennas. The importance of CP antennas and consequently the advantage of this antenna is shown in this Letter. Undoubtedly, to report a work with a novel technique you must conquer many issues. In this work, finding a co-planer cell which enables a linearly polarised antenna to circularly polarise was a big challenge; in addition to issues such as selecting an antenna to radiate directionally. We are working on increasing the bandwidth and 3-dB axial ratio of this antenna and also concentrating on mm-wave antennas to improve their characteristics. In further steps, we would like to work on applying this to mm-wave CP array antennas. Over those years, many works about mm-wave antennas have been reported. We are hoping that as this continues over the next ten years, mm-wave antennas can be released in most countries, in order to use high data transfer in this frequency band. This could be so helpful for real-time communication as well as helping to save many lives through use in automotive radar. Additionally, this frequency band, which can achieve high accuracy in microwave imaging systems, can be used in biomedical systems for so many applications like tumour detection and prediction. By increasing the data transfer rate to allow 3-D vision, it will have an impact in the entertainment sector too.