Amplifiers – Combined with automatic amplifier disabling switch means
Reexamination Certificate
1999-11-10
2001-03-13
Pascal, Robert (Department: 2817)
Amplifiers
Combined with automatic amplifier disabling switch means
C330S136000
Reexamination Certificate
active
06201441
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a semiconductor circuit which amplifies and damps a high frequency band signal such as UHF, a microwave or a millimeter wave.
BACKGROUND TO THE INVENTION
FIG. 1
shows a conventional semiconductor circuit as disclosed for example in JP-A-62-23629. In the figure, reference numeral
1
denotes an input terminal which inputs a high frequency signal,
2
is a bias control circuit which supplies a bias current to a variable damper
3
when a signal level of a high frequency signal is higher than a reference level,
3
is a variable damper which damps a high frequency signal when a bias current is received from the bias control circuit
2
,
4
is an amplifier which amplifies a high frequency signal damped by the variable damper
3
and
5
is an output terminal which outputs a high frequency signal amplified by the amplifier
4
.
The operation of the invention will be outlined below.
Firstly, when a semiconductor circuit is used for signal reception, reception characteristics can deteriorate as a result of the variable damper
3
damping high frequency signals when the signal level of the high frequency signal input from the input terminal
1
is low.
On the other hand, if however damping of the high frequency signal by the variable damper
3
is terminated, the amplifier
4
may be saturated as the signal level of the high frequency signal is high.
In the above conventional example, when a high frequency signal is input from the input terminal
1
, the bias control circuit
2
compares the signal level of the high frequency signal with a reference level. When the signal level of the high frequency signal is lower than the reference level, supply of the bias current to the variable damper
3
is terminated and the attenuation of the variable damper
3
is set to 0 dB.
In this way, reception characteristics may be improved by amplifying the signal level of the high frequency signal since a high frequency signal is output to the amplifier
4
without being damped by the damper
3
.
Furthermore the bias control circuit
2
supplies a bias current to the variable damper
3
when the signal level of the high frequency signal is higher than the reference level and the attenuation of the variable damper
3
is set to XdB.
In this way, saturation of the amplifier
4
may be avoided because a high frequency signal is output to the amplifier
4
after the signal level of the high frequency signal is damped by the variable damper
3
with an attenuation of XdB. However in this case, although the S/N ratio by which the variable damper
4
damps the high frequency signal deteriorates to some degree, a S/N ratio required for reception is maintained since the signal level is high enough to saturate the amplifier
4
.
When the attenuation of the variable damper
3
is set to 0 dB, as stated above, the variable damper
3
does not damp high frequency signals and a high frequency signal is output to the amplifier
4
. When a high frequency signal is output to the variable amplifier
3
, reception characteristics deteriorate and the amplifier
4
increases reception noise due to a certain degree of insertion loss.
In such a case, as shown in
FIG. 2
, it is possible to eliminate deterioration of reception characteristics by disposing the variable damper
3
on the output side of the amplifier
4
. However such an arrangement will not allow saturation of the amplifier
4
to be avoided.
Since a conventional semiconductor circuit is constructed as above, when the variable damper
3
is disposed on the input side of the amplifier
4
, it is possible to prevent saturation of the amplifier
4
. However when the signal level of the high frequency signal is lower than a reference level, reception characteristics deteriorate due to insertion loss. When the variable damper
3
is disposed on the output side of the amplifier
4
, it is possible to prevent deterioration of reception characteristics. However in this case, saturation of the amplifier
4
can not be avoided.
The present invention is proposed to solve the above problems and has the object of providing a semiconductor circuit which can prevent deterioration of reception characteristics and which can prevent saturation of an amplifier.
DISCLOSURE OF THE INVENTION
The semiconductor circuit of the present invention is adapted to generate an operation permission command to one of an amplifying means or a damping means in response to the signal level of an input signal.
In this way, when the signal level of the input signal is high, it is possible to prevent saturation of the amplifying means and when the signal level of the input signal is low, it is possible to prevent deterioration of reception characteristics by avoiding increases in reception noise.
When used for transmission, a power source of the amplifying means can be cut off when the output transmission is reduced. Thus it is possible to reduce power consumption.
The semiconductor circuit of the present invention is adapted to connect in direct series an amplifier which amplifies an input signal with a switch. The switch is placed in a short circuit state when receiving an operation permission command and is placed in an open state when not receiving an operation permission command.
In such a way, when the signal level of an input signal is higher than a reference level, it is possible to isolate the amplifier from the circuit.
The semiconductor circuit of the present invention is adapted to connect in series a damper which damps an input signal with a switch. The switch is placed in a short circuit state when receiving an operation permission command and is placed in an open state when not receiving an operation permission command.
In such a way, when the signal level of an input signal is lower than a reference level, it is possible to isolate the damper from the circuit.
The semiconductor circuit of the present invention is adapted to connect a switching semiconductor terminal to the output and input sides of the damper.
In such a way, when the signal level of an input signal is lower than a reference level, it is possible to isolate the damper from the circuit.
The semiconductor circuit of the present invention is adapted so that the switching semiconductor terminal makes a transition to an open state when a transistor which comprises the amplifying means makes the transition to a short circuit state. When the transistor makes the transition to an open state, the switching semiconductor terminal makes the transition to the short circuit state.
In such a way, when the signal level of an input signal is high, it is possible to prevent saturation of the transistor and when the when the signal level of an input signal is low, it is possible to prevent deterioration of the reception characteristics while avoiding increases in reception noise.
The semiconductor circuit of the present invention is adapted to connect a matching circuit between the damper and the input side of the switching semiconductor terminal and to connect a matching circuit between the damper and the output side of the switching semiconductor terminal.
In this way, it is possible to reduce input/output reflection loss when operating the damper.
The semiconductor circuit of the present invention comprises a damping means using a variable damper adapted to regulate attenuation.
In this way, it is possible to regulate a signal level of a high frequency signal output from the amplifier and as a result, it is possible to prevent saturation of the amplifier while maintaining reception characteristics of the receiver even when the dynamic range of the receiver connected to the output terminal is narrow.
The semiconductor circuit of the present invention comprises a damping means using a series circuit of a circuit terminal and a switching semiconductor terminal.
In this way, when the signal level of the input signal is lower than a reference level, damping of the high frequency signal is terminated. When the signal level of the input signal is higher than a reference level, dam
Iyama Yoshitada
Kitabayashi Fumimasa
Nakajima Kensuke
Suematsu Noriharu
Sugiyama Shigeru
Choe Henry
Mitsubishi Denki & Kabushiki Kaisha
Pascal Robert
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