Telecommunications – Receiver or analog modulated signal frequency converter – With wave collector
Reexamination Certificate
1999-05-07
2001-08-21
Nguyen, Lee (Department: 2683)
Telecommunications
Receiver or analog modulated signal frequency converter
With wave collector
C455S088000, C455S352000, C340S005630, C340S870030, C340S870030
Reexamination Certificate
active
06278869
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a radio system for remote control operation in a stationary vehicle by transmitting high frequency radio signals in the meter wavelength band with a radio transmitter located outside the vehicle, which transmits radio signals in a predetermined radio channel designed only for a receiver located in the vehicle.
Radio systems of this type are known from every day applications, such as vehicular telemetry devices for operation of the vehicle central lock mechanism, heating and similar remote control functions. A high degree of reliability is required for vehicle central lock mechanisms, in which the vehicle is opened with a coded signal from a hand-held transmitter acting as an electronic key. This type of device has two main problem areas. First, the transmitter power should be kept as small as possible because of the miniature battery provided in the small hand transmitter. Inside of a predetermined maximum operating radius of a few tens of meters around the vehicle it should be reliably opened by initiating a radio signal from the hand transmitter device designed for the receiver in the vehicle. In order to prevent undesired opening of the vehicle by erroneous operation of the hand transmitter outside of this predetermined maximum operating radius, it is desirable that the inner radius of the area, in which response of the receiver can be practically prevented, is not substantially larger than the predetermined maximum operating radius for the transmitter device. This condition can be fulfilled only very poorly with antenna apparatus used in practice with a single antenna because of multi-path propagation and difficulties with polarization dependent and omnidirectional antennas. Furthermore the transmission polarizations are also not well defined or definite because of the indefinite or arbitrary manipulation of the transmitter acting as key, so that in principle omnidirectionality for arbitrary polarization should be provided.
The area within the predetermined maximum operating radius
18
and the inner radius
19
of the area in which erroneous operation can be prevented are illustrated in FIG.
10
.
Integrated vehicle antennas have especially pronounced indentations in their directional characteristic diagram because of the influence of the vehicle chassis. In order to achieve reliable response within the range of this predetermined maximum operating radius in the azimuthal direction at these indentations, it is necessary to select a transmitter power for which the sensitivity attainable in the receiver is sufficiently large, so that an undesirably large range for receiver response is obtained in other azimuthal directions at pronounced maxima in the directional characteristic diagram.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved radio system for remote control operation in a stationary vehicle that does not suffer from the above-described disadvantages.
It is an object of the present invention to provide a radio system for remote control operation in a stationary vehicle of the above-described kind, with which remote operation is more reliable inside an area having a predetermined maximum operating radius as the distance from the vehicle and an inner radius of an area in which undesired response of the receiver because of erroneous commands or because of undesired radio signals for operation of other vehicles can be practically prevented is larger than the maximum operating radius by as small a factor as possible.
These objects and others which will be made more apparent hereinafter are attained in a radio system for remote control operation in a stationary vehicle of the above-described kind by means of a high frequency radio transmission in the meter wavelength range with a radio transmitter located outside of the vehicle for transmitting only certain predetermined radio signals in a predetermined radio channel or band designed to be received only by a receiver located in the vehicle.
According to the invention the radio system comprises a radio receiver located in the vehicle; a radio transmitter located outside of the vehicle for transmitting predetermined radio signals in a predetermined radio channel designed to be received only by the radio receiver located in the vehicle; at least two receiving antennas in the vehicle; means for decoupling the at least two receiving antennas for diversity-type operation in the frequency band of the radio channel; a selection circuit connected with the receiving antennas, the selection circuit including switching means for connecting the respective receiving antennas one at a time to the receiver when the receiver is tuned to the radio channel and put in a ready mode and a clock including means for setting predetermined time intervals and means for controlling the selection circuit according to the time intervals, whereby the respective antennas are sequentially connected with the receiver one after the other for the respective time intervals required for detection of a special radio signal designed for the radio receiver or of a radio signal in the radio channel.
A diversity-type decoupling of the receiving antennas in the vehicle occurs when the received signals differ in regard to the reductions or interruptions of the high frequency gain. With a sufficient number of correspondingly decoupled antennas found in the vehicle the probability is correspondingly large that at least one of the antennas has no pronounced gain reduction in its received signal at the given conditions of the radio field. Antennas with a selection circuit in the sense of the present invention can similarly be provided by an antenna device with a controllable switching circuit, as it is described in German Patent Document DE 196 07 045 in FIGS. 1 to 3 and in FIG. 4. In that reference the antennas are decoupled from each other in a diversity-type manner, among other things, because different antenna properties are desired by switching the complex antenna structures.
The transmitter power can thus be selected small so that a reliable response of the receiver with a given receiver sensitivity is guaranteed with the prerequisite of avoiding pronounced gain reductions at the predetermined maximum effective operating radius. The invention has the advantage that with a larger number of selected antennas, the required transmission power required for the predetermined maximum effective operating radius for reliable response is largely independent of a given radio field, which results from the surroundings of the stationary vehicle and the position of the transmitter.
Preferred embodiments of the invention are described in the following detailed description and in the appended claims.
REFERENCES:
patent: 196 07 045 A1 (1997-08-01), None
Hopf Jochen
Lindenmeier Heinz
Reiter Leopold
FUBA Automotive GmbH
Nguyen Lee
Striker Michael J.
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