Communications: directive radio wave systems and devices (e.g. – Directive – Utilizing correlation techniques
Reexamination Certificate
2001-08-29
2003-01-21
Blum, Theodore M. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Utilizing correlation techniques
C342S380000
Reexamination Certificate
active
06509872
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an adaptive antenna receiving apparatus, and more particularly to an adaptive antenna receiving apparatus which is capable of rapidly carrying out adaptive convergence by virtue of an initial weight close to a convergent value of adaptive weight.
2. Description of the Related Art
A CDMA (Code Division Multiple Access) adaptive antenna receiving apparatus has been conventionally used for removal of interference caused by antenna directivity, as suggested in the following documents:
(A) Oh, Kohno and Imai, “TDL Adaptive Array Antenna using diffusion gain for accomplishing spectrum diffusion multiple access”, Electronic Information Communication Academy, Vol. J75-BII, No. 11, pp. 815-825, 1992; and
(B) Tanaka, Miki and Sawahashi, “Characteristics of Judgment Feedback type Coherent Adaptive Diversity in DS-CDMA”, Electronic Information Communication Academy, Radio Communication System Team Technical Report RC96-102, November 1996.
FIG. 1
is a block diagram of a conventional CDMA adaptive antenna receiving apparatus.
It is assumed that the illustrated CDMA adaptive antenna receiving apparatus includes N antennas wherein N is an integer equal to or greater than 2, and M multi-paths wherein M is an integer equal to or greater than 1, and is directed to a K-th user wherein K is an integer equal to or greater than 1.
With reference to
FIG. 1
, signals received at first to N-th antennas
110
-
1
to
110
-N are divided to first to M-th paths in accordance with delay time, and input into both second to M-th delay units
120
-
2
to
120
-M and first to M-th adaptive receivers
130
-
1
to
130
-M. The delay units
120
-
2
to
120
-M delay the input signals for synchronizing the input signals with the first path with respect to a timing. Thus, since the first delay unit
120
-
1
causes zero (0) delay, the first delay unit
120
-
1
is not illustrated in FIG.
1
.
Output signals transmitted from the first to M-th adaptive receivers
130
-
1
to
130
-M are added to one another in an adder
140
, and the thus added output signals are inputted to a judge or evaluation circuit
150
. The judge
150
transmits its output signal as a receipt symbol for the K-th user, which output signal is transmitted also to the first to M-th adaptive receivers
130
-
1
to
130
-M.
Since the first to M-th adaptive receivers
130
-
1
to
130
-M are designed to have the same structure, only the adaptive receiver for a m-th path (1≦m≦M) is illustrated in FIG.
2
.
The received signals are diffused and demodulated in first to N-th reverse diffusion units
161
-
1
to
161
-N, and thereafter, transmitted to both first to N-th multipliers
162
-
1
to
162
-N and a delay unit
163
. The received signals are multiplied with receipt weight in first to N-th multipliers
162
-
1
to
162
-N. The signals having been multiplied with receipt weight are added to one another in an adder
164
. Thus, the received signals are weighted.
The thus weighted signals are transmitted to a multiplier
165
, a communication path estimating unit
166
and an adder
169
. The communication path estimating unit
166
estimates deformation in communication paths. The deformation estimated by the communication path estimating unit
166
is transmitted to the multiplier
165
through a complex conjugate generating unit
167
, and is multiplied with the weighted signals in the multiplier
165
.
An output signal transmitted from the multiplier
165
defines a demodulated signal for the m-th path, and is transmitted to the adder
140
illustrated in FIG.
1
.
The adder
140
adds output signals transmitted from the first to M-th adaptive receivers
130
-
1
to
130
-M, to one another in RAKE synthesis, and transmits an output signal to the judge
150
, which judges the signals with respect to data symbol.
In the adaptive receiver, an output signal transmitted from the judge
150
is multiplied with an output signal transmitted from the communication path estimating unit
166
, in a multiplier
168
, and then, input into the adder
169
. The adder
169
calculates an error by subtracting an output transmitted from the adder
164
, from an output transmitted from the multiplier
168
, and transmits the thus calculated error to an adaptively updating unit
170
.
The adaptively updating unit
170
updates receipt weight, based on the error transmitted from the adder
169
and a signal received at the antenna which signal is delayed by the delay unit
163
by a period of time necessary for demodulating the signal. Herein, there may be used a known algorithm such as least mean square algorithm, as an algorithm for adaptively updating receipt weight.
In the above-mentioned conventional adaptive antenna receiving apparatus, adaptive control is usually carried out by selecting a weight by which signals can be received regardless of signal-receipt conditions, as initial receipt weight, in order to make it possible to receive signals in any conditions, taking into consideration that signals come in different directions in dependence on signal-receipt conditions. For instance, a weight by which antenna directivity is non-directional is selected as such a weight. However, this causes a problem that it would take much time for receipt weight to converge to optimal receipt weight after receipt weight has been started to be adaptively updated.
Japanese Patent No. 2914445 (Japanese Unexamined Patent Publication No. 11-55216) has suggested the CDMA adaptive receiving apparatus including a weighting and synthesizing unit and a weight controller for one user. The weighting and synthesizing unit carries out weighting and synthesis for each of CDMA signals received in N antennas. The CDMA adaptive receiving apparatus further includes an error generator which (a) generates M error signals associated with each of paths for a desired wave signal, based on a communication path estimate and M demodulated signals which are demodulated at timings associated with M paths constituting a multi-path, based on signals transmitted from the weighting and synthesizing unit, and (b) synthesizes the error signals into one signal, which is to be transmitted to the weight controller.
Japanese Unexamined Patent Publication No. 10-341200 has suggested an adaptive array antenna receiving apparatus including a complex multiplying unit which multiplies received signals with a complex weight coefficient, an adder which adds output signals transmitted from the complex multiplying unit, to one another, a modulator which modulates known symbols, a subtracter which calculates a difference between an output signal transmitted from the adder and an output signal transmitted from the modulator, and a weight coefficient calculator which calculates the complex weight coefficient, based on the received signals and an output signal transmitted from the subtracter, only when known signal patterns in a desired station and an interference station are different from each other.
Japanese Unexamined Patent Publication No. 11-298388 has suggested an adaptive receiving apparatus including N antennas which receive signals multiplexed by a plurality of user signals, K adaptive receiving blocks associated with K users, which K adaptive receiving blocks form a directional pattern having a gain in any direction relative to the signals received at the antennas, and receive desired wave signals through a plurality of paths to thereby suppress interference wave signals, and a synthesizer which synthesizes a plurality of weight control errors with a user by means of path combination to thereby transmit a synthesized weight control error signal. Herein, N and K are integers both equal to or greater than 1. The adaptive receiving blocks form the directional pattern, based on the synthesized weight control error signal.
Japanese Unexamined Patent Publication No. 2000-22612 has suggested a CDMA type adaptive transceiver including a path searcher which extracts path level information and path delay time information out of signals re
Ishii Naoto
Ushirokawa Akihisa
Yoshida Shousei
Blum Theodore M.
Whitham Curtis & Christofferson, P.C.
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