Pulse or digital communications – Receivers – Automatic gain control
Reexamination Certificate
2000-12-08
2004-05-04
Phu, Phoung (Department: 2631)
Pulse or digital communications
Receivers
Automatic gain control
C455S234100
Reexamination Certificate
active
06731703
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims benefit of Japanese Patent Application No. 11-348264 filed on Dec. 8, 1999, the contents of which are incorporated by the reference.
The present invention relates to reception power level calculating circuits and receivers using the same and, more particularly, to reception power level calculating circuits and receivers using the same, which can be suitably used for CDMA communication system mobile stations.
FIG. 3
schematically shows the construction of a receiver having an AGC (Automatic Gain Control) function. Referring to the Figure, received signal is fed from an antenna
1
to a front terminal circuit
2
. The front terminal circuit
2
comprises a duplexer, an amplifier, a band-pass filter, a down-converter, etc., and serves to remove the received signal components outside a desired frequency band and also amplify and frequency convert the received signal. The output of the front terminal circuit
2
is fed to an AGC amplifier
3
. The AGC amplifier
3
controls the gain for the received signal on the basis of a control voltage corresponding to the reception power level, and feeds out its output to a demodulating circuit
4
. The demodulating circuit
4
demodulates the received signal, and feeds out the demodulated signal to an A/D (analog-to-digital) converter
5
. The A/D converter
5
digitally converts the analog demodulated signal, and feeds out the digital demodulated signal to a channel filter
6
.
The channel filter
6
attenuates the frequency components outside the desired frequency band in the neighborhood of a desired frequency, and feeds out the attenuated signal to a succeeding base-band circuit
7
. The base-band circuit
7
executes a base-band processing on the received signal, and also calculates the ratio (SIR: Signal to Interference Ratio) of the power level of desired wave in the received signal to interference frequency power level. A power level calculating circuit
10
calculates the power level of received signal from the output of the A/D converter
5
, and feeds out the difference of the received signal power level from a preset reference power level. This difference corresponds to the difference between the actual level of power fed to the A/D converter
5
and a reference power level to be received. An integrating circuit
9
integrates the power level difference.
The integrating circuit
9
feeds out gain control data thus obtained for controlling the gain of the ACG amplifier
3
corresponding to the antenna terminal reception power level. A D/A converter
8
converts the gain control data to an analog control voltage for controlling the gain of the amplifier
3
. It is adapted that the integrating circuit
9
reports or supplies the obtained integration data as antenna terminal reception power level to the band-pass circuit
7
.
In CDMA communication system which is used for mobile communication, spread codes such as PN (Pseudo Random Noise) codes are used for the spread spectrum of communication signal, and the communication signal is recognized on the basis of such spread codes. The CDMA system features that simultaneous communication among a plurality of radio terminals or via a plurality of channels is possible at the same frequency. The CDMA system also features that the received signal can not be demodulated unless the signal is multiplied by the same spread code as spread code used on the transmitting side at the same timing as thereon, and that the received signals with different spread codes or different spread timings, i.e., communication signals from other radio units or other channel signals, are all introduced as noise into the received signal band.
A case will now be considered, in which a plurality of CDMA system mobile stations, found near and remote from the base station of mobile communication, are in communication therewith. When the mobile stations near and remote from the base station are in communication therewith at the same frequency and the same transmission power level, a problem arises, from a view of the base station receiving terminal, that the transmission power levels of the communicating mobile stations near the base station are higher than the transmission power levels of remote communicating mobile stations so that the signals transmitted from the remote mobile stations are just like buried in the signals transmitted from the near mobile stations. This problem is known as near-remote problem. In view of the above features of the CDMA system, the base station cannot correctly demodulate the transmitted signals from the remote mobile stations because of the fact that the transmitted signals contain near mobile base station signals introduced in the reception band frequency.
In the CDMA system, such near-remote problem is solved by relatively frequent, stringent and highly accurate transmission power level control. Specifically, the transmission power level control is executed to make the near mobile station transmission power level lower and the remote mobile station transmission power level higher. The same control is executed as for the transmission power level from the base station to the mobile stations. For the transmission power level control, the base-band circuit in the receiver, i.e., mobile station side, should have correct antenna terminal reception power level. Accordingly, as shown in
FIG. 3
, the output of the integrating circuit
9
in the AGC circuit is reported as the antenna terminal reception power level to the base-band circuit
7
.
As described above, the base-band circuit
7
computes the power level of the desired frequency for transmission power level control as well as computing the received signal SIR. The computation of the desired frequency power level requires a calculation given as:
(antenna terminal reception power level)×(desired wave power level)/(full reception power level).
The antenna terminal reception power level is the full reception power level. The ratio (desired frequency power level)/(full reception power level) is obtained and known in the base-band circuit
7
, and the base-band circuit
7
is thus adapted to compute the required desired frequency power level by using the antenna terminal reception power level corresponding to the AGC circuit output, which power level is reported from the integrating circuit
9
.
The prior art technique shown in
FIG. 3
, however, has a problem that the antenna terminal reception power level reported to the base-band circuit
7
does not actually correspond to the received signal fed thereto. Therefore, the base-band circuit
7
feeds out erroneously calculated power levels of desired frequency and interference frequency as its output, and also it is impossible to obtain right transmission power level control.
The reason for this resides in that the antenna terminal reception power level reported to the base-band circuit
7
corresponds to the received signal input to the A/D converter
5
while the received signal input to the base-band circuit
7
has been reduced in power level by the power level attenuation outside the desired frequency band in the passing of the output of the A/D converter
6
through the channel filter
6
. This means that the received signal inputs to the A/D converter
5
and the base-band circuit
7
, respectively, are different in power level. This leads to a difference of the corresponding antenna terminal reception power level.
Another prior art technique will now be described with reference to FIG.
4
. In
FIG. 4
, parts like those in
FIG. 3
are designated by like reference numerals. In the prior art technique shown in
FIG. 4
, unlike the prior art technique of
FIG. 3
, a power level calculating circuit
11
for power level calculation to control the gain of AGC amplifier, is provided not on the input terminal side but on the output terminal side of channel filter
6
.
This circuit construction, however, poses a problem of saturation of the A/D converter
5
. Saturation of the converter
5
results in power level increase or swelling
NEC Corporation
Phu Phoung
Whitham Curtis & Christofferson, PC
LandOfFree
Reception power level calculating circuit and receiver using... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reception power level calculating circuit and receiver using..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reception power level calculating circuit and receiver using... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3190952