Telecommunications – Transmitter and receiver at same station
Reexamination Certificate
1998-12-09
2001-08-07
Kincaid, Lester G. (Department: 2745)
Telecommunications
Transmitter and receiver at same station
C455S084000, C455S245100, C455S251100, C330S284000
Reexamination Certificate
active
06272323
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an automatic gain control amplifier control circuit which in particular implements level adjustment with a step attenuator in a transmitter or a receiver. Hereinafter automatic gain control is referred to as AGC.
DESCRIPTION OF THE RELATED ART
In a transmitter or a receiver, for example the conventional AGC amplifier control circuit is used to adjust the transmitting or receiving power with a step attenuator disposed at near an antenna.
FIG. 1
is a block diagram showing an example of the conventional AGC amplifier control circuit. In
FIG. 1
, a transmitting attenuator TX ATT
121
and a receiving attenuator RX ATT
110
are step attenuators providing a selective function which makes radio frequency RF signals pass as they are (off state) or makes only a certain quantity of the signals attenuate (on state).
A TX ATT controller
140
and a RX ATT controller
130
control to be that the attenuation characteristic of the transmitting attenuator TX ATT
121
and the receiving attenuator RX ATT
110
is hysteresis characteristic for a transmitting or received level at a terminal of an antenna respectively. A transmitting AGC amplifier TX AGC
124
and a receiving AGC amplifier RX AGC
113
adjust the gain of the transmitting or receiving IF (intermediate frequency) signal power. A TX memory
127
or a RX memory
116
memorizes the control voltage data of the transmitting AGC amplifier TX AGC
124
or the receiving AGC amplifier RX AGC
113
corresponding to the transmitting or receiving level about respective state of on/off of the transmitting or receiving attenuator. A transmitting digital to analog converter TX D/A
126
or a receiving digital to analog converter RX D/A
115
converts the control voltage of the transmitting AGC amplifier TX AGC
124
or the receiving AGC amplifier RX AGC
113
digital to analog and outputs the voltage, and controls the gain of the transmitting AGC amplifier TX AGC
124
or the receiving AGC amplifier RX AGC
113
.
At the case of the characteristic between the gain and the control voltage V
cnt
of the AGC amplifier is not linear as shown in
FIG. 2
, for desired transmitting level or receiving level at a terminal of an antenna, the gain of the AGC amplifier is controlled to be linear as shown in
FIGS. 3 and 4
. To achieve this, the characteristic between the transmitting level and the transmitting control voltage V
tx
shown in
FIG. 5
, and the characteristic between the receiving level and the receiving control voltage V
rx
shown in
FIG. 6
are needed. In the TX memory
127
, the control voltage data shown in
FIG. 5
are memorized and in the RX memory
116
, the control voltage data shown in
FIG. 6
are memorized. At the time when the data expressing transmitting or receiving level are inputted as addresses, designated transmitting or receiving control voltage data are outputted. In this, the unit of the transmitting level, the receiving level and the gain of the transmitting and receiving AGC amplifier is “dB”.
Next, the operation of an example of the conventional AGC amplifier control circuit is explained.
FIG. 7
is a diagram showing data conversion of the transmitter and
FIG. 8
is a diagram showing data conversion of the receiver of the present invention. However, in this explanation,
FIGS. 7 and 8
of the present invention are also used.
First, the transmitter is explained. The TX ATT controller
140
controls the transmitting attenuator TX ATT
121
in hysteresis for the transmitting level as shown in
FIG. 7
(
a
). The reason why the transmitting attenuator TX ATT
121
is controlled in hysteresis is not to make the turning of on/off occur continuously, that is, to prevent the chattering from occurring, at the case that the transmitting level is stayed at near level of the turning on/off of the TX ATT
121
. At the time that transmitting level is small, to improve a noise figure NF the TX ATT
121
is turned on and the attenuation is implemented. In
FIG. 7
(
a
), the TX ATT
121
is in the state of “off” and the transmitting level becomes smaller than the point “A”, the TX ATT
121
is turned “on” and from this state the transmitting level becomes bigger than the point “B”, the TX ATT
121
is again turned “off” and the RF signals are passed without attenuation.
At the points “A” and “B” which the TX ATT
121
turns on/off, not to make the transmitting level at the terminal of the antenna change discontinuously, the TX AGC
124
must change the gain by the same quantity of the attenuation of the TX ATT
121
to the reverse direction. In
FIG. 7
(
b
) shows the relation between the transmitting level and the gain of the TX AGC
124
. The TX AGC
124
has the gains corresponding to the “on” and “off” state of the TX ATT
121
for the transmitting level respectively and has two kinds of gains between the points “A” and “B” of the transmitting level. Therefore, the TX memory
127
has the memory of the control voltage data for the respective “on” and “off” state of the TX ATT
121
at the transmitting level is between the points “A” and “B”.
Next, the receiver is explained. The RX ATT controller
130
controls the RX ATT
110
in hysteresis for the receiving level as shown in
FIG. 8
(
a
). At the case that the receiving level is large, for an intermodulation IM measure and so forth, the attenuation is implemented by turning on the RX ATT
110
, and at the case that the receiving level is small, the RF signals are passed through as they are, not to make the attenuation implement. In
FIG. 8
(
a
), the RX ATT
110
is in the state of“off” and the receiving level becomes larger than the point “B”, the RX ATT
110
turns on. From this state, by the receiving level becomes smaller than the point “A”, the RX ATT
110
turns again off and the RF signals are not attenuated and passed through.
At the points “A” and “B” which the RX ATT
110
turns “off” and “on”, not to make an input level of a demodulator DEM
114
change discontinuously, the RX AGC
113
must change the gain by the same attenuation quantity of the RX ATT
110
to the reverse direction.
FIG. 8
(
b
) shows the relation between the receiving level and the gain of the RX AGC
113
. The unit of the receiving level and the gain of the RX AGC
113
is “dB” and to make the input level of the demodulator DEM
114
a fixed level, the control voltage data are generated to make the gradient “−1”.
The RX AGC
113
has the gains corresponding to the state of “on” and “off” of the RX ATT
110
respectively for the receiving level and has two kinds of gains between the point “A” and “B” of the receiving level. Therefore the RX memory
116
has the memory of the control voltage data for the respective state of “on” and “off” of the RX ATT
110
at the receiving level between the point “A” and“B”.
The Japanese Patent Laid-Open Publication No. SHO 60-227574 discloses the amplifier for the community television. This amplifier for the community television makes the operational level of the AGC circuit change in step wise and also displays whether the AGC function is operating or not.
The attenuation circuit of the Japanese Utility Model Laid-Open Publication No. HEI 7-33024 is capable of changing by 1 dB steps and controlling without noise. However, the first problem of the conventional type is that the quantity of the data to be memorized in the memory becomes large. The reason why this problem exists is that the gain control voltage data of the AGC amplifier for the transmitting or receiving level must to be memorized for the respective state of on/off of the attenuator.
The second problem is that the bit numbers of the address designating the data memorized in the memory increases and the address designating operation becomes complicated. The reason of the complication is that the construction of the address is constituted of not only the transmitting level or the receiving level but also the additional information expressing the state of “on” and “off” of the attenuator.
SUMMARY OF THE INVENTION
It is therefore
Kincaid Lester G.
NEC Corporation
Scully Scott Murphy & Presser
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