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Multiple-Input Multiple-Output (MIMO) systems offer high capacity to wireless systems over a SISO system and the capacity increases linearly with the number of transmitting antennas as long as the number of receiving antenna s is greater than or equal to the number of transmitting antenna s. OFDM based Ultra Wideband (UWB) system combines OFDM modulation technique with a multi banding approach, which divides the spectrum into several sub-bands, whose bandwidth is approximately 528 MHz. It is a popular method for h igh data rate wireless communications. MIMO techniques promi se a significant boost in the performance of OFDM system s as compared to SISO systems. In this paper, a novel de sign UWB MIMO OFDM system using a compact double-sided print ed antenna having ultra-wideband and band-notched char acteristic is proposed and its capacity enhancement over the c onventional SISO system is shown. The UWB antennas are designed on CST Microwave studio simulation software with return lo ss less than -10dB, and further using the results from CST, the d ata throughput for both single and multiple antenna sys tem is compared for performance analysis. The MIMO UWB ant ennas are designed using polarization diversity of the in dividual antennas. The performance curves of both the system s are analyzed for capacity enhancement. The transmitting bandwidth is UWB (i.e. 3.1-10.6 GHz) and the receiving bandwi dth is notch UWB (notch bandwidth 5-5.9 GHz) are chosen to reduc e the interference at the receiver side for both the syst ems. Furthermore, the systems are designed at a frequenc y of 9.4 GHz that is used for micro power radar application in t he ultra wideband removing the interference from WLAN band. Keywords-Band-notched, Bit Error Rate (BER); Doubl e-sided Printed; Multiple Input Multiple Output (MIMO); Ort hogonal Frequency Division Multiplexing (OFDM); Single Inpu t Single Output (SISO).

Abstract-OFDM based Ultra Wideband (UWB) system combines OFDM modulation technique with a multi banding approach, which divides the spectrum into several sub-bands, whose bandwidth is approximately 528MHz. It is a popular method for high data rate wireless communications. MIMO techniques promise a significant boost in the performance of OFDM systems. In this paper, a novel design UWB MIMO OFDM system using a compact double-sided printed antenna having ultra-wideband and band-notched characteristic is proposed. The UWB antennas are designed on CST Microwave studio simulation software with return loss less than -10dB, and further using the results from CST, OFDM transmission and reception on a MIMO system is done on MATLAB software. The MIMO UWB antennas are designed using polarization diversity of the individual antennas. The performance of this system is studied using BPSK modulation and finally bit error rate and operating range is obtained. The transmitting bandwidth is UWB (i.e. 3.1-10.6GHz) and the receiving bandwidth is notch UWB (notch bandwidth 5-5.9GHz) are chosen to reduce the interference at the receiver side. Furthermore, a MIMO UWB system is designed at a frequency of 9.4GHz that is used for micro power radar application in the ultra wideband removing the interference from WLAN band.

The paper presents a novel and compact antenna array design fed through a 3 dB BLC for producing phase shift in the array. Beam steering is an attractive design feature for avoiding obstacles in the path of the beam. It is achieved by switching the beam to another path by simply varying the phase shift between elements. The proposed structure exhibits resonance in the frequency having range of 27.6 GHz -29.6 GHz with a minimal return loss value of -45 dB for frequency applications of 28 GHz, which can be further employed for 5G frequency applications, there are two multiple beams observed, with main beam at theta equal to -35 degrees, the main beam shifts to +28 degrees by changing the feed port of the coupler. A stable gain of around 11.5 dB is obtained for the entire frequency range. The input phase has been varied for different elements in the array, and best results were obtained for a 90 degree phase difference, which required the use of a 3 dB BLC. Rogers RT Duroid 5880, having a dielectric of 2.2 and a 0.51 mm dielectric height, was used as a substrate for antenna fabrication. The simulations were performed on the CST Microwave studio and the measurements were done on VNA (Agilent N5247A).