Pulse or digital communications – Receivers – Interference or noise reduction
Reexamination Certificate
1998-04-01
2001-05-29
Chin, Stephen (Department: 2734)
Pulse or digital communications
Receivers
Interference or noise reduction
C375S136000, C375S148000, C375S233000, C342S372000, C342S380000
Reexamination Certificate
active
06240149
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmission diversity technique for spread spectrum communication, and, more particularly, to an adaptive transmission diversity apparatus capable of determining a transmission radiation pattern in accordance with a reception radiation pattern.
2. Description of the Related Art
A transmission diversity technique for use in a conventional time division multiplex system and a frequency multiplex system will be described below with reference to
FIGS. 1 and 2
.
FIG. 1
presents a block diagram showing the structure of a conventional adaptive transmission diversity apparatus, and
FIG. 2
is a diagram illustrating the relationship between the incoming directions of radio waves and a reception radiation pattern.
Referring to
FIG. 1
, S
1
(t), S
2
(t), S
3
(t) and S
4
(t) denote complex signals, which have respectively been received at reception antennas
1
,
2
,
3
and
4
at time t and have then undergone A/D conversion and quasi-coherent detection. The outputs W
1
(t), W
2
(t), W
3
(t) and W
4
(t) of a reception radiation pattern controller
13
are respectively sent to multipliers
9
,
10
,
11
and
12
which in turn multiply the associated complex signals by the respective outputs. The multiplication outputs are then composed by an adder
14
. The output, S(t), of the adder
14
then is given by the following formula (1).
S
(
t
)
=
∑
1
4
W
i
(
t
)
S
i
(
t
)
(
1
)
The above process of multiplying signals, received at a plurality of antennas, by the proper complex numbers and then adding the resultant values allows the antennas as a whole to acquire radiation pattern on a plane. When a desired signal is coming from the direction of an arrow
31
in FIG.
2
and an interference signal from the direction of an arrow
32
, for example, the reception radiation pattern controller
13
in
FIG. 1
controls the radiation pattern as indicated by reference numeral “
33
” in
FIG. 2
, so that the desired signal can be received at a strong level and the interference signal at a weak level. This control can enhance the reception performance.
A determination section
16
outputs a result D(t) of determining the composed signal S(t). An error detector
15
outputs a difference S(t)−D(t) between the composed signal S(t) and the determination result D(t). The reception radiation pattern controller
13
renew its output complex number weights W
1
(t), W
2
(t), W
3
(t) and W
4
(t) based on the output of the error detector
15
and the complex signals S
1
(t), S
2
(t), S
3
(t) and S
4
(t).
Given that the reception signal vector is given by Sig(t)=(S
1
(t), S
2
(t), S
3
(t), S
4
(t))
T
, the outputs of the reception radiation pattern controller, W(t)=(W
1
(t), W
2
(t), W
3
(t), W
4
(t))
T
, can be expressed by the following formula (2). And &mgr; is coefficient of step.
W
(
t+
1)=
W
(
t
)+&mgr;(
S
(
t
)−
D
(
t
))
T
Sig(
t
) (2)
A transmission radiation pattern controller
17
computes weight outputs for transmission in consideration of a frequency difference between transmission and reception, etc. based on the outputs of the reception radiation pattern controller
13
. Multipliers
22
,
21
,
20
and
19
multiply the outputs of the transmission radiation pattern controller
17
by a signal from a transmission signal generator
18
. Antennas
23
,
24
,
25
and
26
convert the signals from those multipliers to RF (Radio Frequency) band signals, and transmit the resultant signals.
The above-described conventional time division and frequency division transmission diversity apparatuses have difficulty in detecting a directly arriving reception wave and an indirectly arriving reception wave reflected by buildings, mountains or the like and separating them from each other taking time shift into consideration. This makes it difficult to form a radiation pattern for each incoming wave, which results in a difficulty in controlling the transmission power with the radiation pattern that corresponds to the received wave.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an adaptive transmission diversity apparatus which can detect radiation patterns of direct and indirect waves arriving in a time-shifted manner, and determine a proper transmission radiation pattern in accordance with the radiation patterns. It is another object of this invention to provide a specific reference for selecting a proper transmission radiation pattern.
To achieve those objects, this invention provides an adaptive transmission diversity apparatus which employs a spread spectrum system, detects radiation patterns of direct and indirect waves having arrived in a time-shifted manner, by means of reception radiation controllers, and operates a transmission radiation controller in accordance with a transmission radiation pattern which is determined by selecting a proper one of the radiation patterns obtained by the reception radiation pattern controllers or combining those radiation patterns. This can ensure a higher transmission performance.
REFERENCES:
patent: 5164964 (1992-11-01), Kubo
patent: 5260968 (1993-11-01), Gardner et al.
patent: 5351274 (1994-09-01), Chennakeshu et al.
patent: 5689528 (1997-11-01), Tsujimoto
patent: 5748683 (1998-05-01), Smith et al.
patent: 5752173 (1998-05-01), Tsujimoto
patent: 5757845 (1998-05-01), Fukawa et al.
patent: 5953366 (1999-09-01), Naruse et al.
patent: 6047019 (2000-04-01), Ishii
patent: 0595247 (1994-05-01), None
patent: 0837523 (1998-04-01), None
patent: 6196921 (1994-07-01), None
patent: 8316772 (1996-11-01), None
patent: 97/00543 (1997-01-01), None
patent: 97/09793 (1997-03-01), None
An article by N. Kuroiwa et al., entitled “Design of a Directional Diversity Receiver Using an Adaptive Array Antenna,” published inElectronics&Communication In Japan, Part I-Communications, vol. 74, No. 7, Jul. 1, 1991, pp. 87-97 (XP000270249).
An article by D. Torrieri et al., entitled “Blind Adaptation Using Maximin Algorithm,” published in Proceedings of the Asilomar Conference On Signals, Systems, and Computers, Pacific Grove, Nov. 1-3, 1993, vol. 1, No. CONF. 27, Nov. 1, 1993, pp. 638-642, (XP000463774).
An article by T. Ohgane, entitled “Spectral Efficiency Improvement By Base Station Antenna Pattern Control For Land Mobile Cellular Systems,” published in IEICE Transactions On Communicaton, Vol. E77-B, No. 5, May 1995, pp. 598-605, (XP000540889).
An English Language Abstract of JP 6-196921.
An English Language Abstract of JP 8-316772.
Hiramatsu Katsuhiko
Yukitomo Hideki
Chin Stephen
Greenblum & Bernstein P.L.C.
Liu Shuwang
Matsushita Electric - Industrial Co., Ltd.
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