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Design, Performance, and Applications of a Coherent UWB Random Noise Radar
Published in James D. Taylor, Ultra-wideband Radar Technology, 2018
Ram M. Narayanan, Yi Xu, Paul D. Hoffmeyer, John O. Curtis
A block diagram of the system is shown in Figure 8.1. The noise signal is generated by OSC1, which provides a wideband noise signal with a Gaussian amplitude distribution and a constant power spectral density in the 1-2 GHz frequency range. The average power output of the noise generator is 0 dBm. This output is split into two in-phase components in power divider PD1, which has a 1 dB insertion loss over the 3 dB power split. Thus, the power divider outputs are at -4 dBm nominal level. One of these outputs is amplified in a power amplifier AMP1, which has a gain of 34 dB and a power output of greater than +40 dBm at its 1 dB gain compression point. Thus, the average power output of AMP1 is +30 dBm (1 W), but the amplifier is capable of faithfully amplifying noise spikes that can be as high as 10 dB above the mean noise power. The output of the amplifier is connected to a dual-polarized broadband (1-2 GHz) log-periodic transmit antenna ANT1. The log-periodic antenna, in addition to being broadband, has desirable features such as a constant gain of 7.5 dB with frequency, superior cross-polar isolation of greater than 20 dB, and main-to-back lobe ratio of better than 30 dB over the operating frequency band. Although our initial design calls for transmission of linearly polarized signals, the dual-polarized
L
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
log periodic antenna broadband antenna designed using physical dimensions (lengths, spacings, diameters, etc.) that vary logarithmically. The result of such designs is an antenna whose performance parameters (e.g., input impedance) is periodic with respect to the logarithm of the frequency. log-likelihood function the likelihood function of y given x is the conditional PDF, p(y|x). The log-likelihood function is the logarithm of the likelihood function, log( p(y|x)). log-normal distribution tion with density f (x) = probability distribu-
Communications
Published in Diego Galar, Uday Kumar, Dammika Seneviratne, Robots, Drones, UAVs and UGVs for Operation and Maintenance, 2020
Diego Galar, Uday Kumar, Dammika Seneviratne
Basically, a log-periodic antenna is a broadband, multielement, tight-pillar, directional narrow beam antenna that works on a wide range of frequencies. Such antennas are used in a wide range of applications where variable bandwidth is required, along with antenna gain and directivity. They are useful for a region which requires greater frequency ranges. (ElProCus, 2016; Wong et al., 2012).
Capacitive Coupled Frequency Independent Dielectric Resonator Antenna Array for X-Band Applications
Published in IETE Journal of Research, 2022
Runa Kumari, Santanu Kumar Behera
In 1960s, Isbel introduced a log periodic antenna design to achieve wide bandwidth with superior performances [11]. By applying log periodic technique to antenna array, an insignificant variation in electrical characteristics (i.e. input impedance, bandwidth, gain, radiation patterns, etc.) of the antenna are obtained over wideband frequency, which is within the design limits of the antenna. Recently, few log periodic antennas with different geometry are reported to attain wideband applications. A coplanar waveguide (CPW) fed log-periodic dumb-bell slot antenna array operating as a frequency independent antenna is presented in [12]. For UWB radio systems, a uniplanar log periodic slot antenna excited by CPW feeding is proposed [13]. A broadband single layer printed log-periodic dipole array antenna fed by substrate integrated waveguide is designed in [14]. Single-layered log periodic array of rectangular microstrip patches has been found to achieve broadband applications [15]. A size reduction technique for the log periodic dipole array antennas has been demonstrated in [16] which employs inductive loads on the elements of an antenna. A printed log-periodic dipole antenna with multiple notched bands is introduced for UWB applications [17]. The dipole or planar log periodic antennas suffer from metallic losses, which may limit their performances. These limitations have prompted a desire for DRs that can minimize the losses up to some extent, instead of metallic elements in log periodic array. Introducing a DRA array design using log periodic technique is an alternative way to achieve multi frequency band with reduced metallic losses. Log periodic DRA (LPDRA) array for different applications are investigated in [18–21]. A LPDRA array with branched microstrip line feeding is proposed for Ku band applications [18]. LPDRA array with branch feeding leads to excitation difficulties and the microstrip feed line can introduce some losses. However, if a series feed is used, these problems can be overcome. In [19,20], the LPDRA arrays are designed with overlaid microstrip line feeding with two layers of substrate. An 9 element LPDRA is designed for X-band applications [19] and a wideband LPDRA with reduced number of elements (7 elements) is presented in [20,21].