scholarly journals A New 21-cm Line Survey of the LMC

1984 ◽  
Vol 108 ◽  
pp. 395-396
Author(s):  
K. Rohlfs ◽  
J. Kreitschmann ◽  
J. V. Feitzinger
Keyword(s):  
Noise Temperature ◽  
Beam Width ◽  
Main Beam ◽  
Corrugated Waveguide ◽  
Line Survey ◽  
Single Polarization ◽  
Switching Mode ◽  
Half Power ◽  
Channel Separation ◽  
Made In

The measurements were made in Feb. 1982 with the Parkes 64 m telescope using a corrugated waveguide horn with total half-power beam width of 15′, the first sidelobes being 19 dB down, resulting in an aperture efficiency ηA=0.53±0.007, a main beam efficiency of ηmb=0.80±0.005 and a ratio of source flux to antenna temperature of Γ=0.62±0.1 K/Jy (Murray, priv. comm.). A cooled two channel FET frontend used in the frequency switching mode with Δν = 2 MHz resulted in a system noise temperature at zenith of Tsyst = 40 K for one channel and Tsyst = 50 K for the other. Each frontend channel received a single polarization mode, and this radiation was then further analysed in a 2 × 512 channel autocorrelation spectrometer set at a channel separation of 3.906 KHz corresponding to a velocity resolution of V = 0.824 km s−1. Hanning smoothed this resulted in a σT = 0.05 K for the average of both polarization.

scholarly journals High Spatial Resolution Studies of H13CN, H12CN and HCO+ J = 1-0 Emissions in Orion A

1980 ◽  
Vol 87 ◽  
pp. 39-40 ◽  
Author(s):  
O.E.H. Rydbeck ◽  
Å. Hjalmarson ◽  
G. Rydbeck ◽  
J. Elldér ◽  
A. Sume ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
Spatial Resolution ◽  
Molecular Cloud ◽  
Room Temperature ◽  
High Spatial Resolution ◽  
Beam Width ◽  
Main Beam ◽  
Pointing Accuracy ◽  
Half Power ◽  
Better Than

The distributions of the H13CN, H12CN and H12CO+ J =1-0 lines have been mapped with 20″ spacing towards the Orion A molecular cloud using the new Onsala 20 m millimeter wave telescope equipped with a room temperature mixer. The aperture and main beam efficiencies are about 49 and 65% and the half power beam width is ∼ 43″. The absolute pointing accuracy is estimated to be better than 5″ rms in the Orion elevation range.

A Comparison of Swarm-Based Optimization Algorithms in Linear Antenna Array Synthesis

2021 ◽  
Author(s):  
Ali Durmus ◽  
Rifat KURBAN ◽  
Ercan KARAKOSE
Keyword(s):  
Antenna Array ◽  
Radiation Pattern ◽  
Antenna Arrays ◽  
Heuristic Algorithms ◽  
Beam Width ◽  
Side Lobe ◽  
Side Lobe Level ◽  
Linear Antenna ◽  
Half Power ◽  
Antenna Array Synthesis

Abstract Today, the design of antenna arrays is very important in providing effective and efficient wireless communication. The purpose of antenna array synthesis is to obtain a radiation pattern with low side lobe level (SLL) at a desired half power beam width (HPBW) in far-field. The amplitude and position values ​​of the array elements can be optimized to obtain a radiation pattern with suppressed SLLs. In this paper swarm-based meta-heuristic algorithms such as Particle Swarm Optimization (PSO), Artificial Bee Colony (ABC), Mayfly algorithm (MA) and Jellyfish Search (JS) algorithms are compared to realize optimal design of linear antenna arrays. Extensive experiments are conducted on designing 10, 16, 24 and 32-element linear arrays by determining the amplitude and positions. Experiments are repeated 30 times due to the random nature of swarm-based optimizers and statistical results show that performance of the novel algorithms, MA and JS, are better than well-known methods PSO and ABC.

scholarly journals Dynamics of Gaussian spikes on Gaussian laser beam in relativistic plasma

2009 ◽  
Vol 27 (4) ◽  
pp. 587-593 ◽  
Author(s):  
A. Singh ◽  
M. Aggarwal ◽  
T.S. Gill
Keyword(s):  
Differential Equations ◽  
Laser Beam ◽  
Nonlinear Differential Equations ◽  
Beam Width ◽  
Main Beam ◽  
Gaussian Laser Beam ◽  
Runge Kutta Method ◽  
Self Focusing ◽  
Gaussian Perturbation ◽  
Paraxial Ray

AbstractIn the present paper, we have investigated the growth of a Gaussian perturbation superimposed on a Gaussian laser beam. The nonlinearity we have considered is of relativistic type. We have setup the nonlinear differential equations for beam width parameter of the main beam, growth and width of the laser spike by using the WKB and paraxial ray approximation. These are coupled ordinary differential equations and therefore these are simultaneously solved numerically using the Runge Kutta method. It has been observed from the analysis that self-focusing/defocusing of the main beam and the spike determine the growth dynamic of the spike.

scholarly journals Triple-Band Dual-Polarized Dipole Antenna for 5G Sub-6 GHz Communications

2021 ◽  
Author(s):  
Lixia Yang ◽  
Hafiz Usman Tahseen ◽  
Syed Shah Irfan Hussain ◽  
Wang Hongjin
Keyword(s):  
Return Loss ◽  
Beam Width ◽  
High Gain ◽  
Dipole Antenna ◽  
Base Station ◽  
Iot Applications ◽  
Measured Impedance ◽  
Dual Polarized ◽  
Half Power ◽  
Triple Band

Abstract A triple-band ±45° dual-polarized dipole antenna is presented in this paper. The proposed antenna covers two bands from n77 and one from n79 5G NR frequency spectrums. The profile antenna exhibits the measured impedance bandwidths 3.6-3.85 GHz, 4.05-4.2 GHz and 4.8- 5.15 GHz with S11, S22 < - 15dB return loss. Antenna is fabricated with four substrates; one radiator, one reflector and two feeding baluns. Antenna is designed and optimized with HFSS simulator and fabricated for experimental verification. Antenna gives a stable radiation pattern with 8.55dBi high gain and 70° half power beam width (HPBW) that makes it a good candidate for wireless 5G sub-6 GHz and multiband base station applications. Finally, antenna is tested in a realistic application environment to show the utility of the proposed antenna for wireless sub-6 GHz IoT applications.

scholarly journals Design and Development of Circular Polarized Conformal Microstrip patch Antenna

2019 ◽  
Vol 9 (2S3) ◽  
pp. 106-109
Keyword(s):  
Parametric Study ◽  
Patch Antenna ◽  
Beam Width ◽  
Conformal Structure ◽  
Microstrip Patch Antenna ◽  
Design And Development ◽  
Conformal Antenna ◽  
Microstrip Patch ◽  
Half Power ◽  
Microstrip Feed

This paper presents broadband circular polarized conformal antenna with a square patch for on-board applications. The substrate is located in between patch and the ground. A novel Circular polarized square patch with microstrip feed with two truncated corners with conformal structure is designed. Using a parametric study on the effect of the position of feed, the antenna parameters VSWR bandwidth, half power beam width and polarization of antenna are analysed. Finally fabrication of conformal square patch on 2.2 dialectic substrate and measured results are discussed.

scholarly journals Observations of high velocity HI clouds in the Local Group

1978 ◽  
Vol 79 ◽  
pp. 49-49
Author(s):  
W.K. Huchtmeier
Keyword(s):  
Radio Telescope ◽  
High Velocity ◽  
Local Group ◽  
Neutral Hydrogen ◽  
Beam Width ◽  
Late Type ◽  
M 31 ◽  
High Velocity Clouds ◽  
Half Power ◽  
Magellanic Stream

High velocity clouds (HVC) of neutral hydrogen in or around our galaxy and the observations of intergalactic HI in the Local group: Magellanic stream (Mathewson et al., 1974, Astrophys. J. 190, p. 291), M 31 (Davies, R.D., 1975, Mon. Not. R. astr. Soc., 170, p. 45P), and in the Sculptor group of galaxies (Mathewson et al., 1975, Astrophys. J. 195, p. L97) motivated us to search for HVC-phenomena in a number of nearby late-type galaxies with the 100 m Effelsberg radio telescope which has a half power beam width of 8.5′ at the wavelength of 21 cm.

scholarly journals 4. Progress report on 21-cm. research by the Netherlands Foundation for Radio Astronomy and the Leiden Observatory

1957 ◽  
Vol 4 ◽  
pp. 22-28 ◽  
Author(s):  
G. Westerhout
Keyword(s):  
Noise Figure ◽  
Beam Width ◽  
Local Oscillator ◽  
Line Profiles ◽  
Switching System ◽  
Local Oscillators ◽  
Switching Type ◽  
Frequency Calibration ◽  
Continuous Frequency ◽  
Half Power

From November 1953 to August 1955, about 2500 line profiles have been measured with the Kootwijk receiver, under the supervision of Ir C. A. Muller. His receiver is of the well-known frequency-switching type. Two pairs of channels in the second i.f. amplifier, about 5 Mc./s., have band-widths of 36 kc./s. The components of one pair are 1080 kc./s. apart; the second pair is shifted 500 kc./s. with respect to the first. Each pair of channels, combined with the continuously variable second local oscillator and with the fixed, crystal-controlled pair of first local oscillators, which are also 1080 kc./s. apart, gives a switching system. The power at a certain frequency is compared with that at a 1080 kc./s. higher frequency during half the switching period and with that at a 1080 kc./s. lower frequency during the other half by switching between the two first local oscillators. The signals are fed through an integrating network with a time constant of 54 sec. At the outputs of the two pairs are two separate recorders, each giving one-half (or more) of a line profile (see Fig. 1). A continuous frequency calibration of the second local oscillator provides 10 kc./s. markers on the records, accurate to 1 in 106. The limiting sensitivity is 0·7°K., with an overall noise figure of 6·3 (8·0 db.). The 7·5 m. Würzburg aerial has a beam-width between half-power points of 1°·9 × 2°·7.

Sign in / Sign up

Export Citation Format

Share Document