Multiple carrier adaptive notch filter

Details Multiple carrier adaptive notch filter Multiple carrier adaptive notch filter

2002-05-17

2004-04-06

Vo, Nguyen T. (Department: 2685)

Telecommunications

Receiver or analog modulated signal frequency converter

Noise or interference elimination

C455S063100, C455S067110, C455S296000

Reexamination Certificate

active

06718166

ABSTRACT:

TECHNICAL FIELD
The present invention is directed to communication systems and, more particularly, to a technique for adaptive notch filtering a multiple carrier signal.
BACKGROUND ART
As shown in
FIG. 1
, an exemplary telecommunication system
10
may include mobile units
12
,
13
A,
13
B,
13
C, and
13
D, a number of base stations, two of which are shown in
FIG. 1
at reference numerals
14
and
16
, and a switching station
18
to which each of the base stations
14
,
16
may be interfaced. The base stations
14
,
16
and the switching station
18
may be collectively referred to as network infrastructure.
During operation, the mobile units
12
,
13
A,
13
B,
13
C, and
13
D exchange voice, data or other information with one of the base stations
14
,
16
, each of which is connected to a conventional land line telephone network. For example, information, such as voice information, transferred from the mobile unit
12
to one of the base stations
14
,
16
is coupled from the base station to the telephone network to thereby connect the mobile unit
12
with a land line telephone so that the land line telephone may receive the voice information. Conversely, information, such as voice information may be transferred from a land line telephone to one of the base stations
14
,
16
, which in turn transfers the information to the mobile unit
12
.
The mobile units
12
,
13
A,
13
B,
13
C, and
13
D and the base stations
14
,
16
may exchange information in either analog or digital format. For the purposes of this description, it is assumed that the mobile unit
12
is a narrowband analog unit and that the mobile units
13
A,
13
B,
13
C, and
131
) are wideband digital units. Additionally, it is assumed that the base station
14
is a narrowband analog base station that communicates with the mobile unit
12
and that the base station
16
is a wideband digital base station that communicates with the mobile units
13
A,
13
B,
13
C, and
13
D.
Analog format communication takes place using, for example, narrowband 30 kilohertz (KHz) channels. The advanced mobile phone systems (AMPS) is one example of an analog communication system in which the mobile unit
12
communicates with the base station
14
using narrowband channels. Alternatively, the mobile units
13
A,
13
B,
13
C, and
13
D communicate with the base stations
16
using a form of digital communications such as, for example, code-division multiple access (CDMA) or time-division multiple access (TDMA). CDMA digital communication takes place using spread spectrum techniques that broadcast signals having wide bandwidths, such as, for example, 1.2288 megahertz (MHz) bandwidths.
The switching station
18
is generally responsible for coordinating the activities of the base stations
14
,
16
to ensure that the mobile units
12
,
13
A,
13
B,
13
C, and
13
D are constantly in communication with the base station
14
,
16
or with some other base stations that are geographically dispersed. For example, the switching station
18
may coordinate communication handoffs of the mobile unit
12
between the base stations
14
and another analog base station as the mobile unit
12
roams between geographical areas that are covered by the two base stations.
One particular problem that may arise in the telecommunication system
10
is when the mobile unit
12
or the base station
14
, each of which communicates using narrowband channels, interfere with the ability of the base station
16
to receive and process wideband digital signals from the digital mobile units
13
A,
13
B,
13
C, and
13
D. In such a situation, the narrowband signal transmitted from the mobile unit
12
or the base station
14
may interfere with the ability of the base station
16
to properly receive wideband communication signals.
As will be readily appreciated, the base station
16
may receive and process wideband digital signals from more than one of the digital mobile units
13
A,
13
B,
13
C, and
13
D. For example, the base station
16
may be adapted to receive and process four CDMA carriers
40
A-
40
D that fall within a multi-carrier CDMA signal
40
, as shown in FIG.
2
. In such a situation, narrowband signals transmitted from more than one mobile units, such as, the mobile unit
12
, may interfere with the ability of the base station
16
to properly receive wideband communication signals on any of the four CDMA carriers
40
A-
40
D. For example,
FIG. 3
shows a multi-carrier CDMA signal
42
containing four CDMA carriers
42
A,
42
B,
42
C and
42
D adjacent to each other wherein one of the CDMA carriers
42
C has a narrowband interferer
46
therein. As shown in
FIG. 3
, it is quite often the case that the signal strengths of the CDMA carrier signals
42
A-
42
D are not equal.


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