Patent JP-2018142945-A (JP)
Title: Method for using elliptically polarized light to concurrently perform multiplex communication of two signals by one electromagnetic wave
Inventor: UTSUGIDA MASAHITO
IPC: H04J14/06
Filed: 2017-02-28
Abstract: PROBLEM TO BE SOLVED: To perform multiplex communication with one kind of electromagnetic waves in interplanetary communication, satellite communication or the like in a planetary probe, thereby shortening the time for transmission and reception of a large amount of signals, increasing the number of channels of satellite communication, decreasing the number of transponders of a planetary probe or artificial satellite and consequently decreasing the weight of the planetary probe or artificial satellite.SOLUTION: In the present invention, multiplex communication is performed in such a way that a pair of signals are concurrently transmitted and received by one electromagnetic wave and the signals are transmitted and received according to elliptical polarization instead of circular polarization that has been used for interplanetary communication and satellite communication. It makes possible: to shorten a communication time of interplanetary communication; to increase the number of channels of satellite communication; and to decrease the number of transponders of an artificial satellite. Using elliptical polarization, the transmission time and reception time in interplanetary communication can be both shortened to about 1/2. On a reception side in satellite communication, a pair of signal voltages are identified and separated by use of a ratio of a pair of voltages of a received elliptically polarized electromagnetic wave, and the pair of signals are each processed as a signal concerned. The polarization mode offers a technique which can be used in any of analog signal communication and digital signal communication. In elliptical polarization and circular polarization, an electromagnetic wave has a pair of electric fields of which the polarization planes are normal to each other and different by 90°. With elliptical polarization, simple harmonic vibrations of the pair of electric fields different in electric field amplitude are shifted from each other by a quarter of one vibration time temporally. Circular polarization has the same characteristics as those of elliptical polarization except that a pair of electric fields of an electromagnetic wave are identical to each other in simple harmonic vibration amplitude; simple harmonic vibrations of the pair of electric fields are shifted from each other by a quarter of one vibration time temporally. Because of the temporal difference of a quarter of one vibration time between the electric fields, the forefront (maximum amplitude point) of each electric field vector appears to rotate on an electromagnetic wave-receiving plane in terms of location. The electromagnetic wave has right-turning polarized and left-turning polarized electromagnetic wave components because of the pair of electric fields being in such a temporal relation that one electric field is precedent to the other; electric fields of the polarized electromagnetic wave components appear to change according to a circle on the receiving plane in circular polarization, and they appear to change according to an ellipse in elliptical polarization. When an artificial satellite radiating an elliptically polarized electromagnetic wave is rotating, the ellipse appears as if rotating, and the direction of each axis of the ellipse of the electric fields in the receiving plane is not fixed. In the case of using elliptical polarization for satellite communication with a planetary probe or artificial satellite, it will do the business to separate and identify transmitted signals by use of a ratio of voltages in major and minor axis directions of the ellipse in consideration of the attenuation of an electromagnetic wave in the atmosphere, the ionosphere and water vapor on condition that signals at a receiving point of a parabola antenna are used; the forefront of each electric field vector at the receiving point will move along the circumference of the ellipse with time. In a view of its physical phenomenon, the electromotive force caused by each electric field of an elliptically polarized electromagnetic wave at the receiving point of the parabola antenna changes with time. Electromotive forces caused by the electric fields in major and minor axis directions of the ellipse become maximum and minimum respectively. So, it will do the business to detect the electromotive forces at the receiving point at intervals of a signal-transmission time (the number of vibrations at the time of signal transmission) of the smallest unit of a digital or analog signal. The maximum and minimum voltages of the electromotive forces caused by the electric fields of elliptical polarization are detected by: amplifying signals of the minimum and maximum values of the electromotive forces to obtain a pair of signals from the amplified signals; directly detecting a peak voltage from one of the pair of signals; inverting the other signal by a transistor; and superposing a bias voltage of plus or minus polarity on the inverted other signal to detect a peak of the resultant voltage. Performing the above voltage detecting operation at intervals of the minimum unit time of signal transmission, a pair of signals transmitted from the planetary probe or artificial satellite can be concurrently separated and identified by one electromagnetic wave without performing time division in a way that follows the change of maximum and minimum voltages of the peak voltages according to time sequence even if the electromagnetic wave is subjected to FM-modulation. Since the maximum and minimum values of the electromotive forces are detected at intervals of the minimum unit time of signal transmission, the change in electromotive force attributed to the electromagnetic wave fading or the like is absorbed, and what are the pair of signals can be determined by e.g. an identification code that each transmitted signal includes. In addition, an advantage of the invention is that a pair of signals can be concurrently transmitted and received by elliptical polarization without performing time division of an electromagnetic wave of one frequency. If there is no need for concurrently transmitting and receiving a pair of signals, things would go well by transmitting and receiving one signal by one electric field in the same way as in conventional satellite communication by circular polarization. If the other electric field carries no signal, the peak voltage of electromotive force does not change with time on a reception side and as such, the electromagnetic wave can be handled as an electromagnetic wave with no signal. In an electromagnetic wave according to a conventional circularly polarization, electric fields making a pair are identical to each other in amplitude and in the change of peak voltages of electromotive forces caused by the pair of electric fields with time. So, the paired signals to be output are the same. In this case, it is assumed that "a circularly polarized electromagnetic wave has been received," and electromotive forces caused by a pair of electric fields are compared for voltage output in differential amplification. If a voltage of zero (0) is output as a result of the differential amplification, it will do the business to take only one voltage output, as a signal.