Array antenna

Details Array antenna Array antenna

2001-03-08

2002-06-18

Ho, Tan (Department: 2821)

Communications: radio wave antennas

Antennas

Plural antennas

C343S817000, C343S750000

Reexamination Certificate

active

06407719

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an array antenna apparatus which comprises a plurality of antenna elements and is capable of changing the directivity thereof.
BACKGROUND ART
FIG. 12
is a block diagram showing a configuration of a phased array antenna apparatus of the prior art. Referring to
FIG. 12
, for example, radio signals received by a plurality of n antenna elements
1
-
1
to
1
-N aligned in a linear array
100
are inputted to a combiner
4
through low-noise amplifiers (LNAs)
2
-
1
to
2
-N and variable phase shifters
3
-
1
to
3
-N, respectively. The combiner
4
combines the N phase-shifted radio signals inputted to the combiner
4
, and outputs a combined radio signal after combining the same to a radio receiver
5
. The radio receiver
5
subjects the combined radio signal to processing such as frequency conversion into lower frequencies (down conversion) and data demodulation, and then, extracts and outputs a data signal.
The phased array antenna apparatus is an advanced antenna for obtaining a desired radiation pattern by exciting a plurality of radiating elements in a predetermined relative relationship among the phases thereof. As shown in
FIG. 12
, a plurality of variable phase shifters
3
-
1
to
3
-N is used as means for setting a desired relative relationship among the exciting phases thereof.
As shown in
FIG. 12
, in the phased array antenna apparatus of the prior art, for example, a receiver side has to comprise a plurality of low-noise amplifiers
2
-
1
to
2
-N, a plurality of variable phase shifters
3
-
1
to
3
-N and the combiner
4
, and thus, the apparatus is complicated in configuration, and therefore, the cost of manufacturing the apparatus becomes greatly higher. Then this drawback becomes more serious, in particular, when the number of antenna elements
1
-
1
to
1
-N becomes larger.
It is an essential object of the present invention to provide an array antenna apparatus, having a simple configuration as compared to that of the prior art, and capable of remarkably reducing the manufacturing cost thereof, and also facilitating controlling the directivity thereof.
DISCLOSURE OF THE INVENTION
According to one aspect of the present invention, there is provided an array antenna apparatus comprising:
a radiating element for transmitting and receiving a radio signal therethrough;
at least one parasitic element incapable of transmitting and receiving any radio signal, said parasitic element arranged at a predetermined distance from the radiating element;
a variable-reactance element connected to the parasitic element; and
controlling means for changing directivity of the array antenna apparatus by changing a reactance of the variable-reactance element.
Also, in the above-mentioned array antenna, the variable-reactance element is preferably a varactor diode, and the controlling means changes capacitance of the varactor diode by changing a backward bias voltage applied to the varactor diode, thereby changing the directivity of the array antenna apparatus.
Further, the above-mentioned array antenna preferably further comprises:
a plurality of the parasitic elements, arranged on a circumference of a predetermined circle around the radiating element.
Therefore, according to the present invention, the array antenna apparatus according to the present invention has a very simple structure as compared to that of the array antenna apparatus of the prior art shown in
FIG. 12
, and, for example, the use of the variable-reactance element such as a varactor diode makes it possible to realize the array antenna apparatus capable of electronically controlling the directivity at a direct-current voltage. The array antenna apparatus is easily mounted to electronic equipment such as a notebook type personal computer or a PDA so as to serve as an antenna for a mobile communication terminal, for example. Moreover, even when the main beam is scanned in any direction on a horizontal plane, all parasitic variable-reactance elements effectively function as wave directors or reflectors and also greatly facilitate the control of the directivity.


REFERENCES:
patent: 3560978 (1971-02-01), Himmel et al.
patent: 3742513 (1973-06-01), Ehrenspeck
patent: 4700197 (1987-10-01), Milne
patent: 5235343 (1993-08-01), Audren et al.
patent: 5767807 (1998-06-01), Pritchett
patent: 6288682 (2001-09-01), Thiel et al.
patent: 4932239 (1974-08-01), None
patent: 5991707 (1984-05-01), None
patent: 6125304 (1986-02-01), None
patent: 5206717 (1993-08-01), None
patent: 10154911 (1998-06-01), None

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