Radio device

Details Radio device Radio device

2001-12-18

2003-07-08

Tarcza, Thomas H. (Department: 3662)

Communications: directive radio wave systems and devices (e.g.,

Directive

Utilizing correlation techniques

C342S372000, C455S276100, C455S277100

Reexamination Certificate

active

06590532

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a configuration of a radio equipment capable of changing antenna directivity on real time basis, and particularly to a configuration of a radio equipment used in an adaptive array radio base station.
BACKGROUND ART
Recently, various methods of transmission channel allocation have been proposed to realize effective use of frequency, in a mobile communication system, of which some have been practically implemented.
FIG. 30
shows an arrangement of channels in various communication systems including frequency division multiple access (FDMA), time division multiple access (TDMA) and path division multiple access (PDMA).
Referring to
FIG. 30
, FDMA, TDMA and PDMA will be briefly described. FIG.
30
(
a
) represents FDMA in which analog signals of users
1
to
4
are subjected to frequency division and transmitted over radio waves of different frequencies f
1
to f
4
, and the signals of respective users
1
to
4
are separated by frequency filters.
In TDMA shown in FIG.
30
(
b
), digitized signals of respective users are transmitted over the radio waves having different frequencies f
1
to f
4
and time-divided time slot by time slot (time slot: a prescribed time period), and the signals of respective users are separated by the frequency filters and time-synchronization between a base station and mobile terminals of respective users.
Recently, PDMA method has been proposed to improve efficiency of use of radio frequency, as portable telephones have come to be widely used. In the PDMA method, one time slot of one frequency is spatially divided to enable transmission of data of a plurality of users, as shown in FIG.
30
(
c
). In the PDMA, signals of respective users are separated by the frequency filters, the time synchronization between the base station and the mobile terminals of respective users, and a mutual interference eliminating apparatus such as an adaptive array.
The operation principle of such an adaptive array radio base station is described in the following literature, for example:
B. Widrow, et al.: “Adaptive Antenna Systems”, Proc. IEEE, vol.55, No.12, pp.2143-2159 (December 1967).
S. P. Applebaum: “Adaptive Arrays”, IEEE Trans. Antennas & Propag., vol.AP-24, No.5, pp.585-598 (September 1976).
O. L. Frost, III: “Adaptive Least Squares Optimization Subject to Linear Equality Constraints”, SEL-70-055, Technical Report, No.6796-2, Information System Lab., Stanford Univ. (August 1970).
B. Widrow and S. D. Stearns: “Adaptive Signal Processing”, Prentice-Hall, Englewood Cliffs (1985).
R. A. Monzingo and T. W. Miller: “Introduction to Adaptive Arrays”, John Wiley & Sons, New York (1980).
J. E. Hudson: “Adaptive Array Principles”, Peter Peregrinus Ltd., London (1981).
R. T. Compton, Jr.: “Adaptive Antennas—Concepts and Performance”, Prentice-Hall, Englewood Cliffs (1988).
E. Nicolau and D. Zaharia: “Adaptive Arrays”, Elsevier, Amsterdam (1989).
FIG. 31
is a model diagram conceptually showing the operation principle of such an adaptive array radio base station. Referring to
FIG. 31
, an adaptive array radio base station
1
includes an array antenna
2
formed by n antennas #
1
, #
2
, #
3
, . . . , #n, and a first hatched area
3
shows a range in which radio waves from the array antenna
2
can be received. A second hatched area
7
shows a range in which radio waves from adjacent another radio base station
6
can be received.
In the area
3
, the adaptive array radio base station
1
transmits/receives a radio signal to/from a portable telephone
4
forming a terminal of a user A (arrow
5
). In the area
7
, the radio base station
6
transmits/receives a radio signal to/from a portable telephone
8
forming a terminal of another user B (arrow
9
).
When the radio signal for the portable telephone
4
of the user A happens to be equal in frequency to the radio signal for the portable telephone
8
of the user B, it follows that the radio signal from the portable telephone
8
of the user B serves as an unnecessary interference signal in the area
3
depending on the position of the user B, to disadvantageously mix into the radio signal transmitted between the portable telephone
4
of the user A and the adaptive array radio base station
1
.
In this case, it follows that the adaptive array radio base station
1
receiving the mixed radio signals from both users A and B in the aforementioned manner outputs the signals from the users A and B in a mixed state unless some necessary processing is performed, to disadvantageously hinder communication with the regular user A.
[Configuration and Operation of Conventional Adaptive Array Antenna]
In order to eliminate the signal from the user B from the output signal, the adaptive array radio base station
1
performs the following processing.
FIG. 32
is a schematic block diagram showing the configuration of the adaptive array radio base station
1
.
Assuming that A(t) represents the signal from the user A and B(t) represents the signal from the user B, a signal x
1
(t) received in the first antenna #
1
forming the array antenna
2
shown in
FIG. 31
is expressed as follows:
x
1
(
t
)=
a
1
×
A
(
t
)+
b
1
×
B
(
t
)
where a
1
and b
1
represent coefficients changing in real time, as described later.
A signal x
2
(t) received in the second antenna #
2
is expressed as follows:
x
2
(
t
)=
a
2
×
A
(
t
)+
b
2
×
B
(
t
)
where a
2
and b
2
also represent coefficients changing in real time.
A signal x
3
(t) received in the third antenna #
3
is expressed as follows:
x
3
(
t
)=
a
3
×
A
(
t
)+
b
3
×
B
(
t
)
where a
3
and b
3
also represent coefficients changing in real time.
Similarly, a signal xn(t) received in the n-th antenna #n is expressed as follows:
xn
(
t
)=
an×A
(
t
)+
bn×B
(
t
)
where an and bn also represent coefficients changing in real time.
The above coefficients a
1
, a
2
, a
3
, . . . , an show that the antennas #
1
, #
2
, #
3
, . . . , #n forming the array antenna
2
are different in receiving strength from each other with respect to the radio signal from the user A since the relative positions of the antennas #
1
, #
2
, #
3
, . . . , #n are different from each other (the antennas #
1
, #
2
, #
3
, . . . , #n are arranged at intervals about five times the wavelength of the radio signal, i.e., about 1 m, from each other).
The above coefficients b
1
, b
2
, b
3
, . . . , bn also show that the antennas #
1
, #
2
, #
3
, . . . , #n are different in receiving strength from each other with respect to the radio signal from the user B. The users A and B are moving and hence these coefficients a
1
, a
2
, a
3
, an and b
1
, b
2
, b
3
, . . . , bn change in real time.
The signals x
1
(t), x
2
(t), x
3
(t), . . . , xn(t) received in the respective antennas #
1
, #
2
, #
3
, . . . , #n are input to a receiving unit
1
R forming the adaptive array radio base station
1
through corresponding switches
10
-
1
,
10
-
2
,
10
-
3
, . . . ,
10
-n respectively so that the received signals are supplied to a weight vector control unit
11
and to one input of each of the corresponding multipliers
12
-
1
,
12
-
2
,
12
-
3
, . . . ,
12
-n respectively.
Weights w
1
, w
2
, w
3
, . . . , wn for the signals x
1
(t), x
2
(t), x
3
(t), . . . , xn(t) received in the antennas #
1
, #
2
, #
3
, . . . , #n are applied from the weight vector control unit
11
to other inputs of these multipliers
12
-
1
,
12
-
2
,
12
-
3
, . . . ,
12
-n respectively. The weight vector control unit
11
calculates these weights w
1
, w
2
, w
3
, . . . , wn in real time, as described later.
Therefore, the signal x
1
(t) received in the antenna #
1
is converted to w
1
×(a
1
A(t)+b
1
B(t)) through the multiplier
12
-
1
, the signal x
2
(t) received in the antenna #
2
is converted to w
2
×(a
2
A(t)+b
2
B(t)) through the multiplier
12
-
2
, th

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