Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Amplitude control
Reexamination Certificate
1998-08-25
2001-05-15
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Amplitude control
C327S561000, C330S011000
Reexamination Certificate
active
06232816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a signal level monitoring circuit for outputting voltage or current corresponding to an input signal level, particularly, a transmitting signal level which is output from a transmitting unit or a received signal level which is input to a receiving unit, in a multiplex communication apparatus used in microwave band (below, microwave multiplex communication apparatus).
2. Description of the Related Art
In general, a microwave multiplex communication apparatus includes a meter and the like, for displaying the transmitting signal level from the transmitting unit and the received signal level in the receiving unit, and has a structure which can monitor the transmitting signal level or the received signal level by converting a value displayed on the meter to a predetermined signal level by using a predetermined conversion table.
Accordingly, the transmitting unit or the receiving unit provided in the microwave multiplex communication apparatus comprises a signal level monitoring circuit consisting of a detector for detecting a transmitting signal or a received signal and an amplifier for amplifying an output signal level from the detector, in order to monitor the transmitting signal level or the received signal level; and a display unit, such as a meter, for displaying an output signal level from the signal level monitoring circuit.
Further, the signal level from the signal level monitoring circuit must be adjusted so that, when an input signal level RFin to the detector is a minimum input level RF
min
, the signal level from the monitoring circuit becomes a predetermined minimum monitor output level V
min
. Further, when the input signal level RFin to the detector is a standard input level RF
typ
the signal level from the monitoring circuit becomes a predetermined standard monitor output level V
typ
.
In order to provide a structure in which the minimum monitor output level Vmin and the standard monitor output level V
typ
of the monitor output signal are the predetermined values and the level of the monitor output signal can be adjusted so as to coincide with these output levels V
min
and V
typ
, a direct current amplifying circuit (below, a DC amplifier) which can determine an optional gain and an offset value, is used as the signal level monitoring circuit.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a signal level monitoring circuit which can adjust precisely and surely the gain and the offset voltage based on simple adjusting steps in a short time and only once.
In accordance with the first aspect of the present invention, there is provided a signal level monitoring circuit for outputting either voltage or current corresponding to an input signal level, including:
a variable gain unit for obtaining a predetermined output level without being dependent on a gain, when the input signal level is a predetermined reference input level; and
an offset adding unit for outputting a predetermined reference output level by adding an offset level to the output level of the variable gain means, when the input signal level is the predetermined reference input level.
In a preferred embodiment, the signal level monitoring circuit further includes;
a first offset adding unit for adding the offset level so that the output level of the variable gain unit becomes zero volt, when the input signal level is the predetermined reference input level;
a second offset adding unit for outputting the predetermined reference output level by adding the offset level to the output level of the variable gain unit, when the input signal level is the predetermined reference input level; and
a gain adjusting unit for adjusting the gain of the variable gain unit.
In another preferred embodiment, the first offset adding unit and the gain adjusting unit are formed by an amplifier using one operational amplifier.
In accordance with a second aspect of the present invention, there is provided a signal level monitoring circuit comprising a first amplifier using a first operational amplifier and a second amplifier using a second operational amplifier and connected to the first amplifier, characterized in that:
an output terminal of a detector (
4
-
1
) is connected to one input terminal of the first operational amplifier (
4
-
21
);
one terminal of a first resistor (R
1
) is connected to a first offset adjusting voltage terminal (Vr) and the other terminal of the first resistor (R
1
) is connected to the other input terminal of the first operational amplifier (
4
-
21
);
one terminal of a second resistor (R
2
) is connected to an output terminal of the first operational amplifier (
4
-
21
) and the other terminal of the second resistor (R
2
) is connected to the other input terminal of the first operational amplifier (
4
-
21
);
one terminal of a third resistor (R
3
) is connected to the output terminal of the first operational amplifier (
4
-
21
), and the other terminal of the third resistor (R
3
) is connected to one input terminal of the second operational amplifier (
4
-
22
);
one terminal of a fourth resistor (R
4
) is connected to an output terminal of the second operational amplifier (
4
-
22
), and the other terminal of the fourth resistor (R
4
) is connected to one terminal of the second amplifier (
4
-
22
);
one terminal of a fifth resistor (R
5
) is connected to a second offset adjusting voltage terminal (Vof), and the other terminal of the fifth resistor (R
5
) is connected to one terminal of the second operational resistor (
4
-
22
);
one terminal of a sixth resistor (R
6
) is connected to the first offset adjusting voltage terminal (Vr), and the other terminal of the sixth resistor (R
6
) is connected to the other input terminal of the second operational amplifier (
4
-
22
); and
one terminal of a seventh resistor (R
7
) is connected to the ground, and the other terminal of the seventh resistor (R
7
) is connected to the sixth resistor (R
6
);
wherein a ratio between resistance values of the sixth and seventh resistors (R
6
, R
7
) is equal to a ratio between a resistance value of the third resistor (R
3
) and a parallel combined resistance value of the fourth and fifth resistors (R
4
, R
5
).
In accordance with a third aspect of the present invention, there is provided a signal level monitoring circuit comprising a first amplifier using a first operational amplifier and a second amplifier adding an offset voltage to the first amplifier, characterized in that:
an output terminal of a detector (
5
-
1
) is connected to one input terminal of the first operational amplifier (
5
-
21
);
one terminal of a first resistor (R
1
) is connected to the other input terminal of the first operational amplifier (
5
-
21
), and the other terminal of the first resistor (R
1
) is connected to a first offset adjusting voltage terminal (Vr);
one input terminal of a second resistor (R
2
) is connected to the other input terminal of the first operational amplifier (
5
-
21
), and the other terminal of the second resistor (R
2
) is connected to an output terminal of the first operational amplifier (
5
-
21
);
one terminal of a second operational amplifier (
5
-
22
) is connected to the first offset adjusting voltage terminal (Vr);
one terminal of a third resistor (R
3
) is connected to the other input terminal of the second operational amplifier (
5
-
22
), and the other terminal of the third resistor (R
3
) is connected to a second offset adjusting voltage terminal (Vof);
one terminal of a fourth resistor (R
4
) is connected to an output terminal of the second operational amplifier (
5
-
22
), and the other terminal of the fourth resistor (R
4
) is connected to the other input terminal of the second operational amplifier (
5
-
22
);
one terminal of a fifth resistor (R
5
) is connected to the output terminal of the second operational amplifier (
5
-
22
), and the output terminal of the second operational amplifier (
5
-
22
) is connected to the other input terminal of the first operational amplifier (
5
-
21
) t
Callahan Timothy P.
Englund Terry L.
Fujitsu Limited
Helfgott & Karas P.C.
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