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Detectors
Published in C. R. Kitchin, Astrophysical Techniques, 2020
In the GHz and higher frequency regions, a horn antenna is normally used to collect the radiation, usually with waveguides for the connection to the rest of the system, though plastic, quartz, metal grid and other lenses may be used at high frequencies. Recent developments in the design of horn antennas have enabled them to have much wider bandwidths than previous designs. These developments include using a corrugated internal surface for the horn and reducing its diameter in a series of steps or a smooth surface with step changes in the cone angle, giving a bandwidth that covers a factor of two in terms of frequency. Bandwidths with factors of nearly eight in frequency are possible with dielectric loaded horns. These are smooth-walled horns filled with an appropriate dielectric except for a small gap between the filling and the walls of the horn through which the wave propagates. At high frequencies, the feed horns may need cooling. The James Clerk Maxwell Telescope’s (JCMT’s) decommissioned SCUBA receiver, for example, operated at 350 and 680 GHz using small arrays of bolometers (Section 1.1.15.2) with conical feed horns (its replacement, SCUBA-2 does not use horns, but SCUBA-2’s replacement, planned for 2022, is expected to use more 3,600 smooth-walled feed horns and MKID detectors – see below). The Brazilian Baryon Acoustic Oscillations in Neutral Gas Observations (BINGO) radio telescope has a crossed-Dragone design with two 40-m fixed dishes. It is currently under construction and will use fifty 1.5-m diameter feed horns for its 960 MHz to 1.26 GHz detectors.
Dosimetry
Published in Jitendra Behari, Radio Frequency and Microwave Effects on Biological Tissues, 2019
The schematic diagram of the experimental setup for measuring the induced electric field in the simulated biological bodies is shown in Figure 3.4 (Guru 1976). For simulated biological bodies, a number of experimental models are constructed with plexiglass and filled with saline solutions of various concentrations. These models were placed inside the anechoic chamber and illuminated by electromagnetic wave with frequencies ranging from 1.0 to 3.0 GHz (with 1 kHz modulation). A horn antenna is used as a radiating source. The anechoic chamber is first probed in the y-and z-directions to find a region where there is no variation in SWR (SWR being inversely proportional to the electric field intensity) under free space conditions. These regions are 4 cm from the center in y-direction and greater than 17 cm away from the central location along z-direction. The central location used as reference here is approximately 3 feet away from the horn antenna. The induced electric field inside the saline solution is measured by small dipole type probe loaded with microwave detector. The output of the detector loaded probe is connected to SWR meter. A vertical dipole probe was used to detect the vertical component of the induced electric field, Ex, and a horizontal probe was used to measure the horizontal components Ey and Ez.
Research on ultra-wideband dual-polarized quadruple-ridged horn antenna
Published in Amir Hussain, Mirjana Ivanovic, Electronics, Communications and Networks IV, 2015
Lijia Chen, Hao Li, Nannan Wang
With the development of electronic technology, the millimeter-wave technology begins to be used in the standard test, electronic warfare and radar systems, and the antennas with good performance covering the millimeter-wave range are needed by more and more people, and the polarization of the antenna is asked to be variable in a lot of situations (Chung et al. 2003). Due to its wide frequency bandwidth, high gain and good directivity, horn antenna has been developed and widely used in these fields, usually as a separate antenna or feed source. To allow horn antenna work in a wide band, the ordinary horn must be improved, and usually loaded with ridges. Quadruple-ridged horn antenna can not only meet the requirements of a wide band but also the requirements of the variable polarization (Chung 2010 ).
Broadband and high gain coupled and cascaded square ring antenna for RADAR applications
Published in Waves in Random and Complex Media, 2023
Subash Chandra Yadav, S. P. Duttagupta
High gain, wideband, low sidelobe antennae with directional radiation patterns are required features for satellite communication, radar communication, and mobile base station applications. The high data rate and high directivity of the antenna beam are also vital. The low profile, economical, low mass, simple coaxial feeding, and easily fabricable antennas are preferred. There are many high-gain antenna configurations such as reflector antenna [1], reflect array antenna [2], and horn antenna [3] that can realize a high gain and wide bandwidth. However, the design of these antennas is complex. Whereas, the microstrip antenna is popular owing to its low fabrication cost and plane structure, it suffers from narrow impedance bandwidth and low gain. Furthermore, a dielectric substrate lessens the power-handling capability in comparison to metallic-type antennas due to a lack of better withstanding for high electric field strengths. So, practically, a high-power handling capacity is always preferable. [4–6]. Moreover, many methods have been introduced to enhance the microstrip antenna's bandwidth and gain, such as the use of dielectric with low dielectric constant, stacked patch configurations, super substrate loading, and array design [7]. However, all these methods are complex in design, and the antenna array required an external feeding network, which absorbs additional power and increases complexity and design cost too. There are many wideband microstrip antennas reported, such as a stacked patch [8,9], and U-shape slot antenna [10] techniques give 30–50% bandwidth, but the gain is below 6.5 dBi.
Compact Pattern Diversity Antenna with 3-D Printed All-dielectric Superstrate for WLAN Access Points
Published in IETE Journal of Research, 2023
S. Swapna, G. S. Karthikeya, Shiban K. Koul, Ananjan Basu
A prototype of the proposed antenna has been fabricated as to validate the simulation results. The antenna is fabricated by the photolithographic process while the all-dielectric block is 3-D printed. The 3-D printing was performed using a Raise 3D RxP2200 3D printer which is used in commercial low budget 3-D printing. Foam like material was used to maintain the height between the 3-D printed dielectric and the four-port antenna. This material did not affect the performance of the antennas during measurement. Anritsu MS2028C VNA was used to measure the reflection coefficient of the antenna and the far-field measurements are conducted inside an anechoic chamber. The ETS-Lindgreen 3115 Model double ridged waveguide horn antenna was used as the standard gain antenna for the measurement. The set up used for the measurement of the antenna is depicted in Figure 16(a) and the fabricated antenna is shown in Figure 16(b). The proposed antenna can be connected to an off-the-shelf SP4T switch to select the preferred antenna.
Flexible and Beam Steerable Planar UWB Quasi-Yagi Antenna for WBAN
Published in IETE Journal of Research, 2022
Veeraselvam Aruna, Mohammed Gulam Nabi Alsath, Savarimuthu Kirubaveni, Marimuthu Maheswari
The proposed antenna is tested in an anechoic chamber with a broadband double ridged waveguide horn antenna. Figure 10 shows the measurement set up of beam steering quasi-Yagi antenna in anechoic chamber. Laboratory made 1:2 power divider that can generate in-phase and out of phase signals are used during the measurement. Figures 11 (a) and (b) show the measured radiation characteristics of the proposed antenna for different relative phase difference at port 1 and port 2 calculated at 7 and 9 GHz, respectively. The pattern shown is normalized by the lowest gain of the dual beam radiation pattern obtained using the in-phase excitation. The measurement results show some side lobes which are attributed to the imperfections in the power divider which are not included in the simulation. However, the desired beam steering functionality can be verifies using the results shown below.