This letter reports electromagnetic transmission measurements through cloth samples from eight types of fabrics common in garments and baggage. The transmission at millimeter-wave and terahertz frequencies was measured with a custom ErAs:GaAs tunable photomixing spectrometer. The IR transmission between 3 and 8μm was measured with a Fourier-transform infrared spectrometer. All samples were usefully transparent at millimeter-wave frequencies (up to 300GHz) based on a 3dB criterion, but became progressively opaque at higher frequencies in a highly sample-dependent manner. This is explained by the samples becoming “optically dense” in the THz region, so that the transmission becomes exponentially dependent on sample thickness. The attenuation in the IR region is very high (⩾25dB) except in two samples (rayon and nylon), whose exceptional transparency (e.g., −12dB in nylon) is attributed to pores intrinsic to the material.
This letter reports the fabrication and demonstration of an ErAs:GaAs interdigitated photomixer as a tunable THz source ranging from ∼20GHzto∼2THz, with 12μW maximum power typically around ∼90GHz. Each photomixer is coupled to a composite dipole-spiral planar antenna that emits a Gaussian-type beam into free space. The beam switches from dipole to spiral antenna behavior as the frequency increases. A distributed Bragg reflector is embedded in the device beneath the photomixer to increase its external quantum efficiency. The photomixer has a 900Å thick silicon nitride coating which serves as an antireflection and passivation layer, and also improves the reliability and heat tolerance of the device.
NRZ data and the clock are synchronized with each other by adjusting the ODL, NRZ-to-RZ format conversion will be realized. Figure 12 shows the experimental results of NRZ-to-RZ format conversion. Figure 12(a) shows the waveform of the original NRZ data, the recovered clock, TOAD's switching window, and the converted RZ data. As can be seen from this figure, there is no evident pattern effect in the converted RZ data and its extinction ratio is about 10 dB. Figure 12(b) shows the optical spectrum of the original NRZ data, the recovered clock, and the converted RZ data, respectively. In this figure, the original NRZ data has no split spectrum line, whereas in the converted RZ data, evident spectrum lines are generated, spaced 10-GHz apart (the spectrum interval is 0.08 nm). The experimental results clearly demonstrate the applicability of the scheme. CONCLUSIONSThis paper has proposed an NRZ-to-PRZ converter consisting of an SOA and an AWG. Through numerical simulation, the effects of the parameters (including the power, wavelength, bit rate of the NRZ data, and the bandwidth of AWG and SOA current) on clock component extraction are investigated, which is a useful guide for the performance optimization. In the experiments, the clock-tomodulation ratio of the NRZ data at 10 Gb/s was enhanced more than 15 dB using the proposed converter, which is beneficial for further clock recovery. All-optical clock recovery from NRZ data at 10 Gb/s was successfully demonstrated with this converter and a mode-locked SOA fiber laser. Furthermore, using the recovered clock as the control light of TOAD, NRZ-to-RZ format conversion at 10 Gb/s with extinction ratio of 10 dB was further realized, emphasizing the practical applicability of the proposed clockrecovery scheme for NRZ data. This scheme is a promising method for high-speed clock recovery from NRZ data in future communication networks. ACKNOWLEDGMENT ABSTRACT: The compact microstrip monopole antenna (CMMA) is a novel antenna design that combines a microstrip patch antenna with a 3D structure to attain a highly directive, broadband, compact antenna. A tri-lobed patch (TLP) is designed to minimize the patch's area while reducing the antenna's operating frequency. A grounding wall (GW) connects the patch to the ground plane and a vertical-enclosure wall (VEW) extends up, away from portions of the patch's perimeter. This Figure 1Design technique used for laying out the TLP in the CMMA: (a) a depiction of the equilateral hexagon used to determine the location of the six uniform circles with 2.3-mm radius; (b) the darker region depicts the area used to define the TLP from part a; (c) the TLP design used in the CMMA (this patch was fabricated on 1. NASA's vision for space exploration calls for extending the human presence throughout the solar system through both human and robotic missions [1]. This vision will be realized with a return to the moon by 2020 in preparation for future human missions to Mars and beyond. As NASA begins exploring these destinations a flexible, reliable,...
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