In many modern telecommunication systems, band-pass filters represent main devices for multi-band applications. In this paper, a new design approach of the dual-band bandpass microwave filter (DBBPF) is provided for X-and Ku-band applications. The proposed filter is inspired by two symmetrical split ring metamaterial resonators (SSRRs) of the same square shape and different sizes. These resonators which have negative permittivity (  0) are interlinked by a metallic line and etched on the upper face of a Rogers's substrate (RO4003) with physical characteristics r  3.55 and tg  0.0027. The two SSRRs are connected to two microstrip feed lines adapted to 50 Ω impedance. To obtain the frequency responses of this complicated microwave structure, simulations based on the HFSS are launched. The proposed DBBPF which has the dimensions 26.86 mm  19.60 mm  0.8 mm provides good electrical qualities for two bandwidths of 380 MHz and 710 MHz covering X-and Ku-bands, respectively.

A multi-input multi-output (MIMO) antenna is presented in this paper. The proposed antenna is formed by four (04) radiating patch elements of different sizes and shapes (rectangular and circular). These elements are excited by four feed ports, each port is parallel to three other adjacent ports. All elements are etched on the upper face of the FR4_Epoxy dielectric substrate for electrical dimensions 1.260  1.050  0.0190 (0 is calculated at an operating frequency of 3.75 GHz). In order to improve the performance of our MIMO antenna, nine (09) complementary metamaterial resonators (CSRRs) of compact sizes are printed on the ground plane of the overall structure. These symmetrical rectangular and circular CSRRs act as an isolator between the radiating elements which contributes to the reduction of the mutual coupling between these adjacent elements. The obtained results reveal that the proposed sub-6 GHz antenna operates in the 5G band at 3.61 GHz (3.3-4.2 GHz) with high port isolation (lower than 28 dB). In addition, the antenna loaded with CSRRs demonstrates good MIMO performance with an envelope correlation coefficient (ECC) of less than 0.07, more than 1360 MHz bandwidth, negligible mutual coupling, and a gain of 15.79 dB. The suggested MIMO sub-6 GHz antenna is suitable for 5G applications.