Volume 60, Nº 11 (2017)

The splitting of magneto-dielectric modes frequency in disk ferrite resonators in a magnetic field is considered.Asimplified formula is obtained for estimation of the splitting magnitude. Theoretical and experimental results of the frequency splitting effect in magneto-dielectric modes in the millimeter wave range are compared. The use of the splitting of the magneto-dielectric modes frequencies as an alternative to ferromagnetic resonance in devices with magnetic frequency tuning is suggested, with values of the magnetization fields being an order of magnitude lower than for ferromagnetic resonance. The features of the splitting modes effect in different ferrite classes are investigated and it is shown that it occurs in both microwave and optical ranges. The estimated magnitude of the mode frequency splitting in the iron-yttrium garnet (YIG) transparency window can reach 9 GHz, which is comparable to the 5 GHz splitting in the millimeter range. The frequency ranges where frequency splitting effect is of practical interest are discussed. In particular, the effect in barium hexaferrite can be used both in post-resonance and pre-resonance regions, which is almost impossible for ferrogarnates and ferrospinels.

Multi Carrier Code Division Multiple Access (MC-CDMA) is attractive technique for high speed data transmission in multipath fading channel. MC-CDMA system cannot handle the sudden time variations of the channel which cause the subcarriers to lose their orthogonality. The loss of orthogonality between the subcarriers of a user or unwanted correlation between the spreading codes of different user can lead to increase in Multiple Access Interference (MAI). Space Time Block Code (STBC) based MC-CDMA system is chosen to achieve full diversity and transmission rate without the knowledge of Channel State Information (CSI) at the transmitter. Thus, in the paper STBC is introduced at the transmitter to improve the quality of the receiver. Space Time Block Code-Parallel Interference Cancellation (STBC-PIC) receiver has been proposed for MC-CDMA system. In the proposed STBC-PIC receiver, at each interference cancellation stage, weighted signal of the other user is subtracted from signal of the desired user, thereby reducing the MAI and improving the BER performance. From the simulation results, it is observed that the proposed receiver outperforms STBC-Orthogonal Complete Complementary Code (STBC-OCCC), STBC-Minimum Mean Square Error (STBC-MMSE) and STBC-Zero Forcing (STBC-ZF) receivers for MAI reduction.

Interleaving is one of the most common methods known to eradicate the effects of multiple user interference. Removal of different interferences is one of the major challenges for advanced communication system designers. Several methods of interleaving have been proposed in literature and their performances have been analyzed on different communication systems to prove their worthiness in multiple user interference removal. One of such interleavers is power interleaver, which can be employed in communication systems as a means to control burst errors and reduce the multiple user interference. In this paper, performances of two different integrated interleave division multiple access (IIDMA) techniques i.e. SCFDM-IDMA and OFDM-IDMA have been analyzed. Novelty of this work is in the sense that the entire analysis has been performed in the presence of power interleavers for the above two IIDMA techniques as the conventional IDMA fails to mitigate the problems of inter-carrier and inter-symbol interferences. Hence, the two techniques in presence of power interleavers empower the idea of quality communication without any interference for future generation communication systems.