This paper presents a circular polarization reconfigurable antenna for 5G applications, which is compact in size and has good axial ratio and frequency response. The proposed microstrip antenna is designed on a FR-4 substrate with a relative dielectric constant of 4.3 and has a maximum size of 30×30 mm 2 with 50 Ω coaxial probe feeding. This design has two PIN diode switches controlling reconfiguration between right hand circular polarization (RHCP) and left hand circular polarization (LHCP). To achieve reconfigurability, a C-slot rectangular patch antenna with truncated corner techniques is employed by cutting off two corners on the radiating patch. The proposed antenna has been simulated using CST microwave studio software: it has 3.35-3.77 GHz and 3.4-3.72 GHz bands for both states of reconfiguration, and each is suitable for 5G applications with a good axial ratio of less than 1.8 dB and good gain of 4.8 dB for both modes of operation.

No abstract

Cyclic Prefix (CP) is one of the key OFDM parameters. It is used to completely eliminate both Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) as long as the CP length is greater than the channel delay spread. By eliminating the ISI and ICI, the CP compensates for the effect of the multi-path dispersion; but it consumes a considerable amount of the scarce spectrum and the power. Contemporary OFDM systems usually use a fixed and large CP length to tolerate worst case channel condition. This technique, however, causes a loss in bandwidth efficiency as well as consumes relatively more transmitter energy. Therefore, there is a need to adopt the CP length based on the channel parameters. This paper investigates the effect of varying the CP length on the OFDM system over different wireless channel models, where the variable CP length is estimated based on the Maximum Excess Delay Spread (MEDS) of the channel. According to this method, the estimated CP length optimizes the system capacity and improves the overall system performance.

A Cyclic Prefix (CP) is a significant feature of an OFDM waveform. It is used to completely eliminate both Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) as long as the CP length is greater than the channel delay spread. By eliminating both ISI and ICI, the CP compensates for the effect of the multipath dispersion; but it consumes a considerable amount of the scarce spectrum and the power. Conventional OFDM uses a fixed and large CP length to overcome the ISI caused by channel delay spread under wireless mobile environment. This approach may degrade the overall spectral efficiency as well as consumes relatively more transmitter energy. Therefore, there is a need to adopt the CP length according to instantaneous channel parameters. In this paper, we presented a method for investigating the effect of varying the CP length on OFDM system performance over different multipath channel models. We estimated the variable CP length based on the RMS delay spread of the channels' power delay profile (PDP). According to this method, the estimated CP length optimizes the system capacity and improves the overall system performance. We showed that this approach could lead to a mathematical formula presenting the relationship between the CP length and the RMS delay spread of the channels.

No abstract