Site and path errors in short-wave direction-finding

1947 ◽  
Vol 94 (77) ◽  
pp. 235-235
Author(s):  
W. Ross
Keyword(s):  
Direction Finding ◽  
Short Wave ◽  
Wave Direction

scholarly journals Indicators of accuracy for determining the coordinates of radio emission sources in the short wave direction finding network

2021 ◽  
Vol 5 (1) ◽  
pp. 75-81
Author(s):  
Anatolij Kobziev ◽  
Mykhailo Murzin
Keyword(s):  
Radio Emission ◽  
Spherical Surface ◽  
Direction Finding ◽  
Short Wave ◽  
Emission Sources ◽  
Passive Radar ◽  
Wave Direction ◽  
Spherical Form ◽  
Radar Systems ◽  
Wave Range

Direction finding networks have found application in radio monitoring, radio intelligence and passive radar systems. The operation of the direction-finding network in the short-wave range has a number of distinctive features, namely, long range of direction finders (up to several thousand km) due to ionospheric propagation of radio waves and high sensitivity of narrow-band signal receivers. In addition, the distance between direction finders can be hundreds or thousands of kilometers. Therefore the calculations should be carried out due to the location of the direction finders and radio sources on a spherical surface. In this work, analytical relationships are obtained for calculating the accuracy indicators of the estimation of coordinate information (latitude and longitude) at the output of the direction finding network in a rather general form in relation to the features of the short-wave range. The problem is solved in a geographic coordinate system for an arbitrary number of direction finders (two at least) and with their arbitrary location on the surface of Earth. To carry out a comparative analysis and assess the quality of coordinate information for various options for placing direction finders, it is proposed to display accuracy indicators using working zones (for example, round). The use of working areas allows a visual assessment on the map overall spatial pattern for accuracy indicators direction-finding network. The results of the calculation of working areas direction-finding network shortwave when placing it on the territory of Ukraine in the case of the smallest real errors direction-finding, and a mutual separation distance finders maximum permissible selected. The calculation results reflect the limiting possibilities for the accuracy of determining the coordinates of radio emission sources for such a direction finding network with a minimum number of direction finders (3 or 4). The given method of calculating working zones allows for the implementation of the best accuracy indicators to choose a specific option for placing direction finders on the territory of the country, taking into account the influence of all factors (approach of positions, availability of access roads, conditions for accommodating service personnel, etc.). As an example, the work considers 3 options for the location of direction finders with the maximum separation on the territory of Ukraine. The developed technique can also be used for other passive radar systems with direction finding coordinates, when it is necessary to take into account the spherical form of the Earth. Such a system can include two or more aerial reconnaissance aircraft with direction finders on board, as well as one aircraft or unmanned vehicle that determines coordinates by the method of multiple direction finding on the flight route.

scholarly journals Response of plant reflectance spectrum to simulated dust deposition and its estimation model

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jiyou Zhu ◽  
Xinna Zhang ◽  
Weijun He ◽  
Xuemei Yan ◽  
Qiang Yu ◽  
...  
Keyword(s):  
Prediction Model ◽  
Spectral Reflectance ◽  
Coal Dust ◽  
Short Wave ◽  
Soil Dust ◽  
Wave Direction ◽  
Dust Deposition ◽  
Cement Dust ◽  
Blue Edge ◽  
Red Edge

Abstract To quantitatively reflect the relationship between dust and plant spectral reflectance. Dust from different sources in the city were selected to simulate the spectral characteristics of leaf dust. Taking Euonymus japonicus as the research object. Prediction model of leaf dust deposition was established based on spectral parameters. Results showed that among the three different dust pollutants, the reflection spectrum has 6 main reflection peaks and 7 main absorption valleys in 350–2500 nm. A steep reflection platform appears in the 692–763 nm band. In 760–1400 nm, the spectral reflectance gradually decreases with the increase of leaf dust coverage, and the variation range was coal dust > cement dust > pure soil dust. The spectral reflectance in 680–740 nm gradually decreases with the increase of leaf dust coverage. In the near infrared band, the fluctuation amplitude and slope of its first derivative spectrum gradually decrease with the increase of leaf dust. The biggest amplitude of variation was cement dust. With the increase of dust retention, the red edge position generally moves towards short wave direction, and the red edge slope generally decreases. The blue edge position moved to the short wave direction first and then to the long side direction, while the blue edge slope generally shows a decreasing trend. The yellow edge position moved to the long wave direction first and then to the short wave direction (coal dust, cement dust), and generally moved to the long side direction (pure soil dust). The yellow edge slope increases first and then decreases. The R2 values of the determination coefficients of the dust deposition prediction model have reached significant levels, which indicated that there was a relatively stable correlation between the spectral reflectance and dust deposition. The best prediction model of leaf dust deposition was leaf water content index model (y = 1.5019x − 1.4791, R2 = 0.7091, RMSE = 0.9725).

scholarly journals Spectral Reflectance Characteristics and Chlorophyll Content Estimation Model of Quercus aquifolioides Leaves at Different Altitudes in Sejila Mountain

2020 ◽  
Vol 10 (10) ◽  
pp. 3636 ◽  
Author(s):  
Jiyou Zhu ◽  
Weijun He ◽  
Jiangming Yao ◽  
Qiang Yu ◽  
Chengyang Xu ◽  
...  
Keyword(s):  
Chlorophyll Content ◽  
Spectral Reflectance ◽  
Spectral Response ◽  
Ecological Status ◽  
Short Wave ◽  
Relative Content ◽  
Tibet Plateau ◽  
Wave Direction ◽  
Estimation Model ◽  
Different Altitudes

Quercus aquifolioides is one of the most representative broad-leaved plants in Qinghai-Tibet Plateau with important ecological status. So far, understanding how to quickly estimate the chlorophyll content of plants in plateau areas is still an urgent problem. Field Spec 3 spectrometer was used to measure hyperspectral reflectance data of Quercus aquifolioides leaves at different altitudes, and CCI (chlorophyll relative content) of corresponding leaves was measured by a chlorophyll meter. The correlation and univariate linear fitting analysis techniques were used to establish their relationship models. The results showed that: (1) Chlorophyll relative content of Quercus aquifolioides, under different altitude gradients, were significantly different. From 2905 m to 3500 m, chlorophyll relative content increased first and then decreased. Altitude 3300 m was the most suitable growth area. (2) In 350~550 nm, the spectral reflectance was 3500 m > 3300 m > 2905 m. In 750~1100 nm, the spectral reflectivity was 2905 m > 3500 m > 3300 m. (3) There were 4 main reflection peaks and 5 main absorption valleys in the leaf surface spectral reflection curve. While, 750~1400 nm was the sensitive range of leaf spectral response of Quercus aquifolioides. (4) The red edge position and red valley position moved to short wave direction with the increase of altitude, while the yellow edge position and green peak position moved to long wave direction first and then to short wave direction. (5) The correlation curve between the original spectrum and the CCI value was the best between the wavelengths 509~650 nm. The correlation between the first derivative spectrum and CCI value was the best and most stable at 450~500 nm. The green peak reflectance was most sensitive to the relative chlorophyll content of Quercus aquifolioides. The estimation model R2 of green peak reflectance was the highest (y = 206.98e−10.85x, R2 = 0.8523), and the prediction accuracy was 95.85%. The research results can provide some technical and theoretical support for the protection of natural Quercus aquifolioides forests in Tibet.

FADING AND SIGNAL-STRENGTH MEASUREMENTS TAKEN DURING THE SOLAR ECLIPSE OF AUGUST 31, 1932

1933 ◽  
Vol 8 (1) ◽  
pp. 29-36 ◽  
Author(s):  
J. T. Henderson ◽  
D. C. Rose
Keyword(s):  
Nova Scotia ◽  
Solar Eclipse ◽  
Signal Strength ◽  
Direction Finding ◽  
Short Wave ◽  
Total Solar Eclipse ◽  
Hudson Bay ◽  
Short Waves ◽  
Electric Company ◽  
Measured Field

This paper contains the results of observations on signal strength and fading, taken during the total solar eclipse of August 31, 1932, by the Canadian Marconi Company, the Northern Electric Company, the Marine Department of the Canadian Government and l'Ecole Polytechnique, Montreal.The Canadian Marconi Company at Yamachiche took signal-strength observations on trans-Atlantic and American short-wave stations. The Northern Electric Company measured field strengths in Montreal from the Ottawa station in the broadcast band (600 Kc.). The stations of the Marine Department in the Hudson Strait and Hudson Bay regions and also in the Newfoundland and Nova Scotia region took notes on short-wave reception from Ottawa and direction-finding bearings on specified nearby stations. L'Ecole Polytechnique had a receiving station at Rigaud, Quebec.The results of observations on short waves indicate no effect at the time of the predicted corpuscular eclipse, but a definite night effect at the time of optical totality. Direction-finding stations and observations on the broadcast band report no effect.

Analysis of electromagnetic wave direction finding performed by spaceborne antennas using singular-value decomposition techniques

Radio Science ◽  
1995 ◽  
Vol 30 (6) ◽  
pp. 1699-1712 ◽  
Author(s):  
H. P. Ladreiter ◽  
P. Zarka ◽  
A. Lecacheux ◽  
W. Macher ◽  
H. O. Rucker ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Singular Value Decomposition ◽  
Direction Finding ◽  
Singular Value ◽  
Decomposition Techniques ◽  
Wave Direction ◽  
Value Decomposition

scholarly journals Ultra-Wideband MM Wave System and RF Modules

2021 ◽  
Author(s):  
Albert Sabban
Keyword(s):  
Communication Systems ◽  
Dynamic Range ◽  
Noise Figure ◽  
Signal To Noise Ratio ◽  
Low Cost ◽  
Direction Finding ◽  
High Gain ◽  
Ultra Wideband ◽  
Wave System ◽  
Wave Direction

Compact wideband RF modules are crucial in mm-wave direction finding systems, radars, seekers, and communication systems. This chapter discusses new integrated wideband mm-wave RF modules. It also discusses the design and development of a compact wideband (18–40 GHz) frontend and a wideband (18–40 GHz) switch bank filter (SBF). The frontend electrical specifications determine the system signal-to-noise ratio and the system dynamic range. This chapter presents a low-cost integrated 18–40 GHz wideband compact frontend with a 47 dBm high power limiter. The frontend consists of two channels: a high gain and low gain channel. Wideband MMIC switches are employed to select the required channel. The gain of the high gain channel is around 27 dB with ±1 dB flatness. The noise figure of the module is around 9 dB. This chapter also presents a low-cost, integrated, 18–40 GHz wideband compact SFB module. The wideband SFB consists of three wideband side-coupled microstrip filters. The SFB MIMIC switches operate in the 18 to 40 GHz frequency range and are used to select the required filter. The insertion loss of each filter section is less than 11.5 dB ±1.5 dB. The novelty of this research is the development of compact, integrated wideband mm-wave RF modules for direction finding and communication systems.

Sign in / Sign up

Export Citation Format

Share Document