Current Issue : October - December Volume : 2017 Issue Number : 4 Articles : 5 Articles
Low-loss waveguides are required for quantum communication at distances beyond\nthe chip-scale for any low-temperature solid-state implementation of quantum\ninformation processors. We measure and analyze the attenuation constant of\ncommercially available microwave-frequency waveguides down to millikelvin\ntemperatures and single photon levels. More specifically, we characterize the\nfrequency-dependent loss of a range of coaxial and rectangular microwave\nwaveguides down to 0.005 dB/m using a resonant-cavity technique. We study the\nloss tangent and relative permittivity of commonly used dielectric waveguide\nmaterials by measurements of the internal quality factors and their comparison with\nestablished loss models. The results of our characterization are relevant for accurately\npredicting the signal levels at the input of cryogenic devices, for reducing the loss in\nany detection chain, and for estimating the heat load induced by signal dissipation in\ncryogenic systems....
A digital breast cancer detection system using 65 nm technology complementary metal oxide semiconductor (CMOS) integrated\ncircuits with rotating 4 Ã?â?? 4 antenna array is presented. Gaussian monocycle pulses are generated by CMOS logic circuits and\ntransmitted by a 4 Ã?â?? 4 matrix antenna array via two CMOS single-pole-eight-throw (SP8T) switching matrices. Radar signals are\nreceived and converted to digital signals by CMOS equivalent time sampling circuits. By rotating the 4 Ã?â?? 4 antenna array, the\nreference signal is obtained by averaging the waveforms from various positions to extract the breast phantom target response. A\nsignal alignment algorithm is proposed to compensate the phase shift of the signals caused by the system jitter. After extracting the\nscattered signal from the target, a bandpass filter is applied to reduce the noise caused by imperfect subtraction between original\nand the reference signals. The confocal imaging algorithm for rotating antennas is utilized to reconstruct the breast image. A 1 cm3\nbacon block as a cancer phantom target in a rubber substrate as a breast fat phantom can be detected with reduced artifacts....
Plane harmonic wave propagation along an interface between vacuum and a semi-infinite uniaxial anisotropic medium is\nconsidered. It is shown that there is a bulk wave within an anisotropic medium in this case. It is also proved for the first time\nthat a reflected wave must propagate perpendicularly to an interface. Moreover, a reflected wave is absent in the case of ordinary\nwave propagation....
The complex temporal-spatial variation of raindrop size distribution will affect the precision of precipitation quantitative estimates\n(QPE) produced from radar data, making it difficult to correct echo attenuation. Given the fact that microwave links can obtain\nthe total path attenuation accurately, we introduce the concept of regional attenuation correction using amultiple-microwave-links\nnetwork based on the tomographic reconstruction of attenuation coefficients. Derived from the radar-based equation, the effect\nof rainfall distribution on the propagation of radar and microwave link signals was analyzed. This article focuses on modeling of\nthe tomographic reconstruction of attenuation coefficients and regional attenuation correction algorithms. Finally, a numerical\nsimulation of regional attenuation correction was performed to verify the algorithms employed here. The results demonstrate that\nthe correction coefficient (0.9175) falls between the corrected and initial field of radar reflectivity factor (root mean square error,\n2.3476 dBz; average deviation, 0.0113 dBz). Compared with uncorrected data, the accuracy of the corrected radar reflectivity factor\nwas improved by 26.12%, and the corrected rainfall intensity distribution was improved by 51.85% validating the region attenuation\ncorrection algorithm. This method can correct the regional attenuation of weather radar echo effectively and efficiently; it can be\nwidely used for the radar attenuation correction and the promotion of quantitative precipitation estimation by weather radar....
method of Standard Site Method (SSM) in the American National Standards\nInstitute�s ANSI C63.5 is de-scribed in the frequency ranges from 30\nMHz to 1000 MHz. And a measurement system is set up for determining antenna\nfactors (AF) of antennas on an Open Area Test Sites (OATS). AF of antennas\nincluding log-periodic antenna and biconical antenna is measured with\nSSM method by Shanghai Institute of Measurement and Testing Technology\n(SIMT), which shows good agreement to data measured by National Institute\nof Metrology (NIM). In the end, it analyzes the measurement uncertainty of\nSIMT in the 30 MHz to 1000 MHz frequency band and does comparison to\nthat of NIM....
Loading....