Communications: radio wave antennas – Antennas – Having electric space discharge device
Patent
1990-04-09
1992-12-15
Hille, Rolf
Communications: radio wave antennas
Antennas
Having electric space discharge device
343749, H01Q 126
Patent
active
051721260
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to active antennas, and more particularly to small superhigh sensitivity active antennas usable in a wide range of applications ranging from a VLF band close to DC to a SHF for satellite broadcasting and satellite communications (FM, televisions, radios, amateur radios, ship and airplane radio communications, mobile radio communications in automobiles, etc., BS and CS).
BACKGROUND TECHNIQUES
Various antennas including linear antennas are known conventionally. Any of these reception antennas has an operational impedance R.sub.o, so that a feeder having a characteristic impedance R.sub.o equal to the operational impedance R.sub.o is connected to the antenna to lead received electric waves to a receiver.
However, since the real part of the operational impedance R.sub.o itself is a source of thermal noise, the received signal would be covered with the thermal noise if there is no reception field strength which exceeds the thermal noise. Thus the received signal is available even if it is amplified in the subsequent stages to whatever degree. Namely, there is a minimum limit to the reception field strength.
It is an object of the present invention to provide a small relatively wide-band active antenna which is capable of receiving in principle any small electric waves below the minimum limit to the reception field strength
DISCLOSURE OF THE INVENTION
An active antenna according to the present invention comprises a lumped constant element forming a reception part for electric waves, and a high input impedance voltage amplifier or a low input impedance (current) amplifier having input terminals connected to the corresponding ends of the lumped constant element directly or via leads very short compared to the wavelength of a received frequency and having an output terminal connected with a receiver, said amplifier including parallel connected amplifying elements.
Thus, the active antenna obtained is small and has superhigh sensitivity. When the inventive active antenna was used, the FM broadcasting from FM-Yokohama Broadcasting Station was received satisfactorily in a building at Akasaka, Minato-ku, Tokyo, with an amplification gain, for example of 20 dB, whereas when a conventional tuner having a 1.5 uV reception sensitivity and a 1 m-dipole antenna were used, the FM Broadcasting could not be received. Similarly, the inventive active antenna succeeded in the reception of the television broadcasting from Tama Television Station in the same building whereas a 32-element 16-dB gain UHF reception antenna could not receive it.
Since no reception current flows in the antenna elements of the inventive active antenna when it receives electric waves, no interference of second radiation occurs. In the conventional antenna, an electric current flows through the antenna elements to cause energy loss of spatial electric waves to thereby nullify electric waves in an adjacent room and hence disable the reception of electric waves by the antennas in the room whereas in the inventive active antenna no currents flows through the antenna elements, and no electric waves are led from the space to the receiver, so that the reception of electric waves by the antenna in the adjacent room is not be disabled.
According to the inventive active antenna, no parabolic antenna is required even in the BS reception, etc. If a high noise figure high amplification factor amplifier is developed, it can replace large-diameter parabolic antennas. Of course, if a parabolic antenna is attached to the inventive active antenna, its sensitivity is furthermore improved to thereby allow to reduce the diameter of the parabolic antenna.
The inventive active antenna has a relatively wideband. According to the conventional antenna, a multi-ghost occurs in the TV reception due to reflection of electric waves by buildings, etc., so that there has been a difficulty in enjoying television broadcasting in a city while according to the inventive active antenna, it has been found that there are many ghost-free spots
REFERENCES:
patent: 2977551 (1961-03-01), Gibson et al.
patent: 3386033 (1968-05-01), Copeland et al.
patent: 3703685 (1972-11-01), Simopoulos et al.
patent: 3714659 (1973-01-01), Firman
patent: 3774218 (1973-11-01), Fowler
patent: 4115778 (1978-09-01), Snow
patent: 5019830 (1991-05-01), Harada
Tooley et al.; "Active Receiving Antenna", Practical Wireless, Mar. 1981, vol. 57, No. 3, pp. 52-56.
Hille Rolf
Kabushiki Kaisha ENU ESU
Le Hoang-anh
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