The Nyquist optical-time-division-multiplexing (OTDM) scheme is expected to realize high spectral efficiency and ultrafast operation over the bandwidth limitation of electrical devices. We proposed a Nyquist OTDM scheme based on optical correlation detection using an impulse response of balanced photo receivers (BPRs), and subtracters. In this letter, we demonstrate our proposed optical correlation detection using BPRs with various bandwidths. We successfully de-multiplex the multiplexed signal by adjusting a subtraction factor at a baud rate of 187.5 Mbaud with a high Q factor of over 20 dB when the BPR bandwidth is 4 or 45 MHz.
In this paper, a new ultra-wideband (UWB) stop-band frequency selective surface (FSS) is proposed. The frequency band, over which flat stop-band is achieved, covers the entire UWB band. The proposed FSS constitutes with compact size unit cells sandwiched between two dielectric substrates. In addition, the performance of the proposed FSS is stable over wide range of incident angles for TE and TM polarizations. Providing good candidate for UWB applications and an optimized solution for integration with compact broadband circuits and as reflectors for the UWB antennas.
Complex interleaved orthogonal design (CIOD) can offers diversity gain to the part of the source in spatial modulation which has single radio frequency (RF) front-end at the transmitter despite multiple-input multiple-output, but emits the undesired component out-of-band. For the reducing out-of-band emission, we give up indicating the information source by the antenna switching and increase both the interleaver size and the antenna switching interval. The increase reduces the discontinuities in the waveform and out-of-band emission. We propose such a scheme as transmit diversity with single RF front-end using CIOD. The diversity gain of the proposed scheme is equivalent to the case for CIOD. Moreover, we evaluate the increase of out-of-band emission and confirm that of the proposed scheme compared to the ideal case is only 3 dB.
The spaceborne precipitation radar has the capability of monitoring three dimensional rain profiles and it can provide important data for understanding water cycle and climate change on the earth. However, the sampling frequency for the same area on the earth is only once per several days. Therefore, more frequent measurement is required to improve the accuracy of short term weather forecast and to monitor typhoons and severe storms. In this paper, the use of the medium earth orbit satellite is studied to observe the same area with short sampling interval of several hours.
In this letter, a miniaturized six port Multiple-Input Multiple-Output (MIMO) antenna is presented and evaluated based on simulation. The proposed antenna consists of three planar inverted-F antennas (PIFA) and three notch antennas. The combination of these elements yields low mutual couplings among them since electric field directions of them are orthogonal to each other. Furthermore, PIFA and notch antenna are miniaturized by using T-shaped conductor and loading reactance, respectively. From the antenna characteristics results, it is found that all mutual couplings were suppressed less than −10 dB. From the channel capacity characteristics results, the channel capacity was improved by 10.62 Bits/s/Hz compared with six dipole antennas with same aperture width of the proposed antenna.
A compact broadband and tri-band slot antenna is proposed. The antenna is composed of a L-shaped slot embedded in a ground plane, a T-shaped microstrip feed line and two rectangular slits etched in the ground plane. The L-shaped slot fed by the T-shaped microstrip line is introduce to generate broad impedance bandwidth, while the two slits are used to divide the one broad band into three frequency bands. The design step of the antenna is presented. Measured results show that the antenna is successfully designed to cover the frequency band from 1.71 to 2.9 GHz for 2G/3G/LTE systems, 3.3–3.8 GHz for WiMAX system and 5–6 GHz for WLAN system.