Telecommunications – Receiver or analog modulated signal frequency converter – With wave collector
Patent
1990-06-28
1993-04-20
Eisenzopf, Reinhard J.
Telecommunications
Receiver or analog modulated signal frequency converter
With wave collector
455139, 4552772, 455304, 455337, H04B 708
Patent
active
052049795
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a receiving method comprising a plurality of individual receiving antennas in which a phase modulation is superimposed on an antenna output signal, the antenna signals are summated and the summation signal amplitude demodulated. The invention also relates to a receiving antenna system for carrying out the method comprising a plurality of individual receiving antennas, a phase modulator, a summation circuit and an amplitude demodulator.
2. Description of the Related Technology
In mobile reception, for example reception of radio and/or television transmissions in motor vehicles, reception disturbances occur which considerably impair the reception. Such reception disturbances are due to the incidence of the radio or television waves on the antenna from more than one direction. This so called multipath reception occurs because the radio or television waves do not only reach the antenna directly from the transmitter but for example are reflected at buildings and also reach the receiving antennas along other paths. The reception paths for the plurality of signals received by the receiving antenna have different lengths so that in the radio and television signal, in particular with frequency-modulated carrier, interference disturbances occur, the resultant carrier thereby undergoing both an amplitude demodulation and a phase demodulation. The latter then given the annoying reception disturbances which considerably impair the reception and which due to the physical factors occur irrespective of the type of antennas employed, whether they are telescopic antennas, electronic short-rod antennas or electronic wind screen antennas.
In an article by R. Heidester & K. Vogt in NTZ 1958, No. 6, pages 315-319, a receiving antenna system is for example described which for reducing this interference occurring due to multipath reception comprises a plurality of individual receiving antennas for mobile reception. Associated with each individual antenna in this known arrangement is a receiver with which the amplitude of each individual signal of the respective individual antenna is continuously determined and monitored. The amplitudes determined are compared and the respective strongest signal of an individual antenna is used as reception signal. This type of diversity system, also referred to as parallel or receiver diversity system, is however very extensive and complicated in circuit technology because each antenna must be provided with a receiver. In addition, it is not certain that the individual antenna which furnishes the strongest antenna signal and is connected to the radio receiver in accordance with the aforementioned criterion necessarily furnishes the best signal, this being true in particular of frequency-modulated signals.
EP 0 201 977 A2, DE 3,334,735 A2 and the journal "Funkschau", 1986, pages 42-45, disclose for example a further receiving antenna system of the type mentioned at the beginning in which switching from one antenna to the other or from one linear combination of antenna voltages to other linear combinations is carried out when the reception quality drops below a predetermined threshold. This method, also known as scanning diversity or antenna selection diversity system, has however the substantial disadvantage that this switching operation is initiated only when interference has occurred. To achieve a transition between the antennas or linear combinations of antenna voltages which is satisfactory for the user and cannot be heard by him the switching over must take place extremely quickly and from the circuit technology point of view this is difficult, very complicated and then nevertheless only possible to a restricted extent. A further substantial disadvantage of this receiving system also resides in that an antenna furnishing a relatively poor reception signal which is however just beneath the switching threshold is kept in operation although other antennas furnish better reception signals with less interference. Furth
REFERENCES:
patent: 4079318 (1978-03-01), Kinoshita
patent: 4334316 (1982-06-01), Tanaka
patent: 4397036 (1983-08-01), Hirade et al.
patent: 4512034 (1985-04-01), Greenstein et al.
patent: 4710975 (1987-12-01), Okamoto et al.
Review of the Electrical Communication Laboratories, vol. 25, No. 1, 2, Jan./Feb. 1977, Tokyo, Japan, "Space diversity reception for ocean microwave communication system", pp. 149-162 by Y. Okamoto.
Buck Walter
Schenkyr Dieter
Eisenzopf Reinhard J.
Koch Robert J.
Pham Chi H.
Richard Hirschmann GmbH & Co.
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