A design for a small and tunable loop antenna is presented. This design enables the higher-order mode resonant frequency to become low while keeping the radiation pattern in good shape. The use of a tunable circuit to utilise higher-order mode for bandwidth enhancement has been investigated. The measured and simulated radiation patterns and voltage standing wave ratio are given.Introduction: For portable reception of digital broadcasting services in the UHF band (470-770 MHz), mobile terminals should have sufficient gain to receive signals; however, the space for a built-in antenna is very small compared to the wavelength in the UHF band. Loop antennas [1] are suitable for a built-in antenna; however, the size of a loop antenna for the UHF band is larger than the size of the mobile terminals. Meander line antennas [2] can have a longer electric length to resonate in the lower UHF band. However, a large number of folds is needed to resonate in the UHF band and a meander line antenna with a low number of folds has a low antenna gain in the lower frequency of the UHF band.This Letter proposes a folded rectangular loop antenna (FRLA) in which the antenna element consists of a long copper wire that is bent and folded a few times at each corner of a rectangular loop. The configuration of the FRLA where the number of folds on the long side of the FRLA is larger than that on the short side is such that the higherorder mode resonant frequency becomes low while keeping the radiation pattern in good shape. In addition, we investigated the use of a tunable circuit with the FRLA to utilise higher-order modes for bandwidth enhancement.

We propose an equalization technique that uses the characteristics of the satellite transponder to compensate for its non-linear distortion. In our previous study, the effects of this technique for 16APSK and 32APSK were assessed in simulations. In this study, we revised the configuration of the equalization system and developed a receiver based on this revision. We examined the reception performance of 16APSK and 32APSK in transmission experiments.

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