Archives

  • 2018-07
  • 2018-10
  • 2018-11
  • 2019-04
  • 2019-05
  • 2019-06
  • 2019-07
  • 2019-08
  • 2019-09
  • 2019-10
  • 2019-11
  • 2019-12
  • 2020-01
  • 2020-02
  • 2020-03
  • 2020-04
  • 2020-05
  • 2020-06
  • 2020-07
  • 2020-08
  • 2020-09
  • 2020-10
  • 2020-11
  • 2020-12
  • 2021-01
  • 2021-02
  • 2021-03
  • 2021-04
  • 2021-05
  • 2021-06
  • 2021-07
  • 2021-08
  • 2021-09
  • 2021-10
  • 2021-11
  • 2021-12
  • 2022-01
  • 2022-02
  • 2022-03
  • 2022-04
  • 2022-05
  • 2022-06
  • 2022-07
  • 2022-08
  • 2022-09
  • 2022-10
  • 2022-11
  • 2022-12
  • 2023-01
  • 2023-02
  • 2023-03
  • 2023-04
  • 2023-05
  • 2023-06
  • 2023-08
  • 2023-09
  • 2023-10
  • 2023-11
  • 2023-12
  • 2024-01
  • 2024-02
  • 2024-03
  • 2024-04
  • 2024-05
  • and limiting the field variations

    2018-11-02

    and limiting the field variations, in the region of oscillations. If the angle θ is equal to the Brewster\'s angle , the two curves coincide. When vertically polarized waves fall on the surface of an ideal dielectric (, is real) at this angle, the reflection coefficient  → 0, and its phase is equal to π and θ<θ0, and is equal to zero at θ>θ0. The difference between H- and V-dipoles described above explains significantly less amplitudes of oscillations in the case of V-dipole. For very long radio control links, the ratio of the received and the transmitted power is given by the Vvedenskiy transmission equation and is independent of polarization and dielectric permittivity [8]. If R≈d is small compared to R2 then Pdir trans≫Pref trans, and the limits of change of the interference factor are significantly reduced. With further decrease of R, the field of the reflected wave can be neglected. In this case the interference factor is close to unity and the Friis transmission equation can be used. It is important to note that all equations derived for an electrically small dipole are applicable to a half-wavelength dipole [8]. The radio control link\'s range is determined by an equality of the total received power and the receiver sensitivity. In Fig. 2, the radio link\'s range complies with the first (from the origin) intersection of the receiver sensitivity corresponding to horizontal lines (in decibels above 1mW) and the received power depending on the distance. Fig. 2 shows (for illustration) a case when the respective receiver sensitivity is of –80dBm. For a long unobstructed path (line-of-sight link), the first Fresnel zone breakpoint may occur. Fig. 2 shows that communication would be lost (in the case of the receiver\'s sensitivity being of –80dBm), as a rule, at about the distance Rmin1= 21m for the H-dipole in the minimum of the first Fresnel\'s zone, while it TW-37 is obvious that the potential range is longer. For the C- and V-dipoles, a decrease in the signal strength due to diffraction is significantly smaller. If the value of the dielectric permittivity is about 1 to 2 then a decrease in the signal strength is again significantly smaller and is practically the same for any polarization. According to the recommendations given in Ref. [7] in line-of-sight channels, directional C-polarization antennas offer an effective means of reducing the delay spread. When the C-polarization signal is incident on a reflecting surface at an incidence angle larger than the Brewster\'s one, the handedness of the reflected C-polarization signal is reversed. The reversal of the C-polarization signal at each reflection means that multipath components arriving after one reflection are orthogonally polarized to the line-of-sight component and proteinoids eliminates a significant proportion of the multipath interference. Since all existing building materials exhibit Brewster angle less than 45° (= 7.0, 2.0, 1.2↔θ0= 8.13°, 26.15°, 39.8°) multipath propagation due to a single reflection (that is the main source of multipath components) is effectively suppressed in most environments irrespective of the interior structure and materials in the room.
    Summary Light emitting diode lighting technologies drastically change the possibilities of control of the light quality. Smart light can be created by changing spectral content, color and intensity of lighting in time. Energy efficient dynamically controlled light sources find application in lighting systems of medical institutions, in museums and art exhibitions providing the best color reproduction of paintings, in industrial lighting for improving working conditions and increasing attentiveness of personnel. This paper discusses two variants of design and construction of wireless networks of dynamically controlled polychromatic light sources: using ISM/SRD and ZigBee (IEEE 802.15.4) technologies. Optical lighting modules are built using AlInGaN and AlGaInP structures, have luminous efficiency of 85–120lm/W and varying light temperatures from relaxing (= 1700K) to activating (= 10,000K). Such controlled LED light sources can be used to correct the psychophysiological state of people.