Information
-
Patent Grant
-
6480708
-
Patent Number
6,480,708
-
Date Filed
Thursday, March 9, 200024 years ago
-
Date Issued
Tuesday, November 12, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Maung; Nay
- Vuong; Quochien B.
Agents
- Ostrolenk, Faber, Gerb & Soffen, LLP
-
CPC
-
US Classifications
Field of Search
US
- 455 671
- 455 2261
- 455 230
- 455 2491
- 455 254
- 333 81 R
- 333 81 A
- 333 138
- 333 139
- 327 308
-
International Classifications
-
Abstract
A compact variable attenuator, composite variable attenuator, and mobile communication apparatus capable of variably controlling attenuation continuously. The variable attenuator includes a first comb line comprising first and second lines which are electromagnetically coupled with a coupling coefficient M, a second comb line comprising third and fourth lines which are electromagnetically coupled with a coupling coefficient M, and first and second diodes connected to the third and fourth lines of the second comb line. A first terminal is connected to one end of the first line and a second terminal is connected to one end of the second line. The first and second diodes are connected between one end of each of the third and fourth lines and a ground with their anodes connected to one end of each of the third and fourth lines, respectively. First and second control terminals for turning the first and second diodes on and off are connected at the junction of other end of the first line and the other end of the third line and at the junction of the other end of the second line and the other end of the fourth line via resistors.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a variable attenuator, a composite variable attenuator and mobile communication apparatus.
2. Description of the Related Art
Generally, in mobile communication apparatus such as mobile telephones, variable attenuators have been used to variably attenuate high frequency signals by using switches to select among a plurality of attenuators having different attenuation values.
FIG. 8
shows a prior art variable attenuator for use in a microwave band. A variable attenuator
70
includes an input terminal
71
, an output terminal
72
, field effect transistors (FET)
731
to
733
and
741
to
743
for switching conduction and cutoff between input and output, and T-type resistance attenuators
751
to
753
, each having losses of A (dB), B (dB) and C (dB), respectively. In this configuration, each of the drain electrodes D of the FETs
731
to
733
, which work as switches at the input end, is connected to the input terminal
71
via a capacitor C
71
, while each of the drain electrodes D of the FETs
741
to
743
, which work as switches at the output end, is connected to the output terminal
72
via a capacitor C
72
. Also, the source electrodes S of the FETs
731
to
733
are connected to one end of respective resistors R
71
to R
73
of the T-type resistance attenuators
751
to
753
via capacitors C
73
to C
75
, respectively; while the source electrodes S of the FETs
741
to
743
are connected to one end of respective resistors R
74
to R
76
of the T-type resistance attenuators
751
to
753
via capacitors C
76
to C
78
, respectively. Further, the other ends of the resistors R
71
to R
73
of the T-type resistance attenuators
751
to
753
, respectively, are connected to the other ends of the resistors R
74
to R
76
, respectively, to connect their nodes to a ground via resistors R
77
to R
79
, respectively. Further, the gate electrodes G of the FETs
731
to
733
and
741
to
743
are connected to the ground via capacitors C
79
to C
81
and C
82
to C
84
, respectively, and are connected to control terminals Vc
71
to Vc
73
and Vc
74
to Vc
76
, respectively, via inductors L
71
to L
73
and L
74
to L
76
, respectively, for cutting-off high frequencies.
A negative voltage at the same level as the pinch-off voltage of the respective FET to be controlled or 0 V is selectively applied to each of the control terminals Vc
71
to Vc
76
: If 0 V is applied to the control terminals Vc
71
and Vc
74
in the first route and a negative voltage at the same level as the pinch-off voltage of the FETs
732
,
742
,
733
and
743
to be controlled is applied to the control terminals Vc
72
, Vc
75
, Vc
73
, and Vc
76
in the second and third routes, respectively, the channel resistance between the drain and the source of the FETs
731
and
741
becomes sufficiently lower than the characteristic impedance of the T-type resistance attenuator
751
. On the other hand, the channel resistances between the drains and the sources of the FETs
732
,
742
,
733
and
743
becomes extremely high due to expansion of depletion layers within the channels. As a result, microwaves input from the input terminal
71
pass through only the first route including the T-type resistance attenuator
751
, while the second and third routes including the T-type resistance attenuators
752
and
753
, respectively, are disabled. Accordingly, attenuation between the input terminal
71
and the output terminal
72
becomes A (dB).
To switch the attenuation between the input terminal
71
and the output terminal
72
to B (dB), 0 V is applied to the control terminals Vc
72
and Vc
75
in the second route and a negative voltage at the same level as the pinch-off voltage of the FETs
731
,
741
,
733
and
743
to be controlled is applied to the control terminals Vc
71
and Vc
74
in the first route, and Vc
73
and Vc
76
in the third route, to enable only the second route including the T-type resistance attenuator
752
. Switching the attenuation to C (dB) is also achieved by a similar operation to the above. The above operations allow variable control of a plurality of attenuations, but discontinuously.
However, the conventional variable attenuator described above has a problem in that the attenuation can not be variably controlled in a continuous manner due its configuration in which it uses switches to select among a plurality of attenuators having different attenuation values.
Also, it tends to require many component parts because the number of FETs that compose a switch in each channel is a number that is a multiple of the number of attenuation steps to be provided. This results in a more complex construction of switches and, further, a more complex configuration of the variable attenuator itself, making the size of the variable attenuator larger and its production cost higher.
SUMMARY OF THE INVENTION
To overcome the above problems, embodiments of the present invention provide a compact variable attenuator, a composite variable attenuator and mobile communication apparatus capable of variably controlling attenuation continuously in order to solve the problems described above.
One embodiment of the present invention provides a variable attenuator which comprises a first comb line consisting of first and second lines which are electromagnetically coupled, and a second comb line consisting of third and fourth lines which are electromagnetically coupled. First and second diodes are connected to the third and fourth lines of the second comb line, the first diode being connected between the third line and a ground with its anode connected to one end of the third line, the second diode being connected between the fourth line and a ground with its anode connected to one end of the fourth line, and the other ends of the first and third lines being connected and the other ends of the second and fourth lines, respectively, which are connected. A first terminal is connected to one end of the first line, and a second terminal is connected to one end of the second line. A first control terminal for turning the first diode on and off is connected to the junction of the other end of the first line and the other end of the third line and a second control terminal for turning the second diode on and off is connected to the junction of the other end of the second line and the other end of the fourth line.
Also, the variable attenuator of the present invention is characterized by being provided with a laminated ceramic substrate comprising a plurality of sheet layers made of ceramic, the ceramic substrate having strip-electrodes which form the first and second lines of the first comb line and the third and fourth lines of the second comb line, wherein the first and second diodes are mounted on the ceramic substrate.
A composite variable attenuator of the present invention is characterized by comprising a plurality of the above variable attenuators, wherein a plurality of variable attenuators are connected in cascade by connecting one end of the second line of a variable attenuator to one end of the first line of an adjacent variable attenuator.
Mobile communication apparatus of the present invention is characterized by using the above variable attenuator.
Also, it is characterized by using the above composite variable attenuator.
According to the variable attenuator of the present invention, since the first and second diodes are connected between one end of each of the third and fourth lines of the second comb line and the ground, it is possible to variably control the resistance of the first and second diodes by variably controlling the voltage being applied to the first and second diodes from the first and second control terminals. As a result, the loss in the first and second lines of the first comb line and that in the third and fourth lines of the second comb line can be variably controlled.
According to the composite variable attenuator of the present invention it is possible to expand the range of attenuation that can be variably controlled as a plurality of variable attenuators are connected in cascade.
According to the mobile communication apparatus of the present invention it is possible to achieve compact mobile communication apparatus, while maintaining receiving balance in the receiving system, because it uses a compact variable attenuator or compact composite variable attenuator.
Other features and advantages of the invention will be understood from the following description of embodiments thereof, with reference to the drawings, in which like references denote like elements and parts.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a circuit diagram of an embodiment of a variable attenuator of the present invention;
FIG. 2
is a perspective view of the variable attenuator shown in
FIG. 1
with some parts thereof shown separately;
FIGS. 3A
to
3
F show plan views illustrating the upper surfaces of a first sheet layer to a sixth sheet layer, of a ceramic substrate of the variable attenuator shown in
FIG. 1
;
FIGS. 4A
to
4
C show plan views illustrating the upper surfaces of a seventh sheet layer to a ninth sheet layer, respectively, and
FIG. 4D
shows the lower surface of the ninth sheet layer of the ceramic substrate of the variable attenuator shown in
FIG. 1
;
FIG. 5
is a graph illustrating the change of attenuation and reflection loss in response to applied voltage in the variable attenuator shown in
FIG. 1
;
FIG. 6
is a circuit diagram of an embodiment of a composite variable attenuator of the present invention;
FIG. 7
is a block diagrams of a mobile telephone that is an example of mobile communication apparatus according to an embodiment of the invention; and
FIG. 8
is a circuit diagram of a conventional variable attenuator.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
An embodiment of the present invention will be described below by referring to the drawings.
FIG. 1
is a circuit diagram of an embodiment of the variable attenuator of the present invention. A variable attenuator
10
includes a first comb line
13
comprising first and second lines
11
and
12
, respectively, which are electromagnetically coupled with a coupling coefficient M, a second comb line
16
comprising the third and fourth lines
14
and
15
, respectively, which are electromagnetically coupled with a coupling coefficient M, and first and second diodes D
1
and D
2
, respectively, which are connected to the third and fourth lines
14
and
15
, respectively, of the second comb line
16
.
A first terminal P
1
is connected to one end of the first line
11
of the first comb line
13
, and a second terminal P
2
is connected to one end of the second line
12
. The first diode D
1
is connected between one end of the third line
14
and a ground with its anode connected to one end of the third line
14
, and the second diode D
2
is connected between one end of the fourth line
15
and the ground with its anode connected to one end of the fourth line
15
.
The other end of the first line
11
of the first comb line
13
, and the other end of the third line
14
of the second comb line
16
are connected. A first control terminal Vc
1
for controlling the first diode D
1
to turn on and off is connected to the junction of two lines via a resistor R
1
.
Also, the other end of the second line
12
of the first comb line
13
, and the other end of the fourth line
15
of the second comb line
16
are connected. A second control terminal Vc
2
for controlling the second diode D
2
to turn on and off is connected to the junction of the two lines via a resistor R
2
.
Next, operation of the variable attenuator
10
with the above circuit configuration is described. If a positive voltage is applied to the first diode D
1
from the first control terminal Vc
1
and to the second diode D
2
from the second control terminal Vc
2
, the resistance of the first diode D
1
and the second diode D
2
is decreased, reducing the coupling coefficient between the first and the second lines
11
and
12
, respectively, of the first comb line
13
and the coupling coefficient between the third and the fourth lines
14
and
15
, respectively, of the second comb line
16
. As a result, if the first terminal P
1
is used for input and the second terminal P
2
for output, the transmission of high frequency signals from the first terminal P
1
to the second terminal P
2
via the first comb line
13
and the second comb line
16
is reduced, that is, the attenuation of the variable attenuator
10
is increased.
More specifically, if a positive voltage applied to the first and the second diodes D
1
and D
2
from the first and the second control terminals Vc
1
and Vc
2
, respectively, is gradually increased from 0 V, the resistance of the first and the second diodes D
1
and D
2
is gradually decreased. As a result, the magnitude of the high frequency signals sent from the first terminal P
1
or the input terminal to the second terminal P
2
or the output terminal via the first comb line
13
and the second comb line
16
is gradually reduced, since the attenuation of the variable attenuator
10
is gradually increased.
Accordingly, it is possible to variably control the resistance of the first diode D
1
and the second diode D
2
by variably controlling the voltage applied from the first control terminal Vc
1
and the second control terminal Vc
2
. This enables the coupling coefficient of the first and second lines
11
and
12
, respectively, of the first comb line
13
and the coupling coefficient of the third and fourth lines
14
and
15
, respectively, of the second comb line
16
to be variably controlled. As a result, the high frequency signals sent from the first terminal P
1
or the input terminal to the second terminal P
2
or the output terminal via the first comb line
13
and the second comb line
16
are variably controlled, since the attenuation of the variable attenuator
10
is variably controlled.
The frequency which can be attenuated by the variable attenuator
10
is one with a wavelength which is the sum of the lengths of the first line
11
and the third line
14
, or the sum of the lengths of the second line
12
and the fourth line
15
. It is noted that the sum of the first line
11
and the third line
14
is equal to the sum of the second line
12
and the fourth line
15
. Accordingly, it is possible to control the frequency which can be attenuated by the variable attenuator
10
by changing the sum of the lengths of the first line
11
and the third line
14
or that of the second line
12
and the fourth line
15
.
FIG. 2
is a perspective view of the composite high frequency component shown in
FIG. 1
, with some parts thereof shown separately. The variable attenuator
10
is provided with a ceramic substrate
17
incorporating strip-line electrodes which comprise the first and the second lines
11
and
12
, respectively, of the first comb line
13
, the third and the fourth lines
14
and
15
, respectively, of the second comb line
16
, and ground electrodes (not shown).
On the upper surface of the ceramic substrate
17
are mounted the first and second diodes D
1
and D
2
, and resistors R
1
and R
2
. Also, external terminals T
1
to T
8
are provided over the sidewalls and the lower surface of the ceramic substrate
17
.
In this example, the external terminals T
1
and T
3
form the first and second terminals P
1
and P
2
, respectively, the external terminals T
5
and T
7
form the first and second control terminals Vc
1
and Vc
2
, respectively, and the external terminals T
2
, T
4
, T
6
and T
8
form ground terminals.
FIGS. 3A
to
3
F and
FIGS. 4A
to
4
D are drawings illustrating upper and lower surfaces of dielectric layers comprising the ceramic substrate of the variable attenuator of FIG.
2
. The ceramic substrate is formed by laminating and firing the first to the ninth sheet layers a to i in that order. The sheet layers consist of low-firing-temperature ceramics whose main constituents are, for example, barium oxide, aluminum oxide, and silicon dioxide which can be fired at a temperature of 850° C. to 1000° C.
Lands La for mounting the first and second diodes D
1
and D
2
, and the resistors R
1
and R
2
are formed on the upper surface of the first sheet layer a. Also, a wiring pattern Li is formed on the upper surface of the second sheet layer b.
Further, ground electrodes G
1
to G
3
are formed on the upper surfaces of the third, sixth and ninth sheet layers c, f and i. Also, strip-line electrodes ST
1
to ST
4
are formed on the upper surfaces of the fourth, fifth, seventh and eighth sheet layers d, e, g and h, respectively. Further, external terminals T
1
to T
8
are formed on the lower surface of the ninth sheet layer (referred to as iu in FIG.
4
D). Further, via-hole electrodes Vh are formed on the first to eighth sheet layers a to h so as to allow them to pass through each of the sheet layers a to h.
In this example, the strip-line electrode ST
1
forms the third line
14
of the second comb line
16
, the strip-line electrode ST
2
forms the fourth line
15
of the second comb line
16
, the strip-line electrode ST
3
forms the first line
11
of the first comb line
13
, and the strip-line electrode ST
4
forms the second line
12
of the first comb line
13
.
Also, the first to fourth lines
11
,
12
,
14
and
15
, respectively, the first and second diodes D
1
and D
2
, respectively, and the resistors R
1
and R
2
are connected within the ceramic substrate
17
by the wiring pattern Li and the via-hole electrodes Vh.
FIG. 5
is a graph illustrating changes in the reflection loss, when the VSWR (voltage standing-wave ratio) is not more than 1.5, and the attenuation, in response to applied voltage, in the variable attenuator shown in FIG.
1
.
The horizontal axis of
FIG. 5
shows the voltage applied to the first and second diodes D
1
and D
2
. In this example, the voltage applied to the first and second diodes D
1
and D
2
from the first and the second control terminals Vc
1
and Vc
2
, respectively, is varied within a range from 0 to 4.5 V to vary the resistance of the diodes D
1
and D
2
.
FIG. 5
demonstrates that by controlling the voltage applied to the first and second diodes D
1
and D
2
from the first and second control terminals Vc
1
and Vc
2
within a range from 0 to 4.5 V to control the resistance of the diodes D
1
and D
2
, it is possible to control the attenuation of the variable attenuator
10
within a range from −1.5 to −21.1 dB and to make the reflection loss less than −13 dB when the VSWR is less than 1.5.
According to the variable attenuator of the above embodiment, since the first and second diodes D
1
and D
2
are connected between one end of each of the third and fourth lines
14
and
15
, respectively, of the second comb line
16
and the ground, it is possible to variably control the resistance of the first and second diodes D
1
and D
2
, respectively, by variably controlling the voltage applied thereto. As a result, this enables to the coupling coefficient M of the first and second lines
11
and
12
, respectively, of the first comb line
13
and the coupling coefficient M of the third and fourth lines
14
and
15
, respectively, of the second comb line
16
to be variably controlled. Accordingly, it is possible to variably control the magnitude of high frequency signals sent from the first terminal or input terminal to the second terminal or output terminal via the first and the second comb lines
13
and
16
, respectively, allowing the attenuation of the variable attenuator to be variably controlled, while making the reflection loss not more than −13 dB when the VSWR is not more than 1.5.
The performance of a variable attenuator is conventionally evaluated with a VSWR of not more than 1.5. The acceptable standard performance with that VSWR is a reflection loss of not more than −13 dB.
Since the first and second terminals P
1
and P
2
are connected to one end of each of the first and second lines
11
and
12
, respectively, of the first comb line
13
and the first and second diodes D
1
and D
2
are connected between one end of each of the third and fourth lines
14
and
15
, respectively, of the second comb line
16
and the ground, the first and second terminals P
1
and P
2
and the first and second diodes D
1
and D
2
are connected to different comb lines. Accordingly, this makes it possible to easily match the impedance of the first comb line
13
and the second comb line
16
seen from the first and second terminals P
1
and P
2
to the characteristic impedance of the high frequency circuit of the mobile communication apparatus on which this variable attenuator is mounted during both the on and off periods of the first and second diodes D
1
and D
2
.
Furthermore, as the variable attenuator is constructed from the first and the second comb lines
13
and
16
, respectively, and the first and second diodes D
1
and D
2
, respectively, the configuration of the variable attenuator becomes simple, enabling a compact variable attenuator to be made and its production costs to be reduced.
Since the variable attenuator is provided with a laminated ceramic substrate comprising a plurality of sheet layers made of ceramic and the ceramic substrate incorporates strip-electrodes made of copper which form the first and second lines
11
and
12
, respectively, of the first comb line
13
and the third and fourth lines
14
and
15
, respectively, of the second comb line, it is possible to handle a high frequency band higher than 1 GHz by a wavelength-shortening effect of the ceramic substrate and losses are reduced by the use of copper.
It is also possible to reduce the mounting area of the variable attenuator as the first and second comb lines
13
and
16
are arranged so as to be laminated in the vertical direction of the ceramic substrate. In fact, the mounting area for the present embodiment is 4.5×3.2 mm
2
.
FIG. 6
is a circuit diagram of an embodiment of a composite variable attenuator of the present invention. A composite variable attenuator
20
has two variable attenuators (each being the same as the variable attenuator
10
in
FIG. 1
) connected in cascade: variable attenuators
101
and
102
are connected in cascade by connecting one end of a second line
12
of a first comb line
13
of the variable attenuator
101
to one end of a first line
11
of the first comb line
13
of the variable attenuator
102
.
A first terminal P
1
is connected to one end of the first line
11
of the first comb line
13
of the variable attenuator
101
and a second terminal P
2
is connected to one end of the second line
12
of the first comb line
13
of the variable attenuator
102
.
According to the above-described composite variable attenuator
20
, it is possible to expand the range of attenuation that can be variably controlled, since a plurality of variable attenuators are connected in cascade. Accordingly, the number of components in the mobile communication apparatus in which this composite variable attenuator is mounted can be reduced and as a result, it is possible to achieve compact mobile communication apparatus.
FIG. 7
is a block diagram of a mobile telephone for W-CDMA (Wideband Code Division Multiple Access) that is one example of mobile communication apparatus. A mobile telephone
30
is provided with a receive-only antenna
31
, a first receiving system
32
responding to the antenna
31
, a transmit-only antenna
33
, a duplexer
34
connected to the antenna
33
, a transmitting system
35
and a second receiving system
36
, both responding to the antenna
33
.
The first and the second receiving systems
32
and
36
include low-noise amplifiers LNA
1
and LNA
2
, band-pass filters BPF
1
and BPF
2
, attenuators Att
1
and Att
2
, and mixers MIX
1
and MIX
2
, respectively, while the transmitting system
35
includes a high power amplifier PA, a band-pass filter BPF
3
and a mixer MIX
3
. In this example, attenuators Att
1
and Att
2
are used to keep the receiving balance constant.
In the above construction, if the compact variable attenuator
10
shown in
FIG. 1
or the compact composite variable attenuator
20
shown in
FIG. 6
is used for attenuators Att
1
and Att
2
included in the first and the second receiving systems
32
and
36
, it is possible to achieve a mobile telephone which is compact in size while maintaining a constant receiving balance in the receiving system.
In the above embodiments of the variable attenuator and composite variable attenuator, examples are described in which one end of the first line and one end of second line comprising the first comb line are directly connected to the first and second terminals, respectively, but alternatively they may be connected via capacitors.
In the above description, the first terminal is set as an input terminal and the second terminal as an output terminal but the same effect will be achieved by setting the first terminal as an output terminal and the second terminal as an input terminal.
Further, in the above example, an embodiment of a composite variable attenuator with two variable attenuators connected in cascade is described, but three or more variable attenuators may be connected in cascade. In such an arrangement the greater the number of the variable attenuators the wider the range of attenuation available for variable control.
According to the variable attenuator of the present invention, since the first and second diodes are connected between respective ends of the third and fourth lines of the second comb line and the ground, it is possible to variably control the resistance of the first and second diodes by variably controlling the voltage applied to the first and second diodes. As a result, this enables the coupling coefficient M of the first and second lines of the first comb line and the coupling coefficient M of the third and fourth lines of the second comb line to be variably controlled. Accordingly, it is possible to variably control the amount of high frequency signals sent from the first terminal to the second terminal via the first and the second comb lines or the amount of high frequency signals sent from the second terminal to the first terminal via the second and the first comb lines, allowing the attenuation of the variable attenuator to be variably controlled, while making the reflection loss less than −13 dB when the VSWR is less than 1.5.
Also, since the first and second terminals are connected to respective ends of the first and second lines of the first comb line and the first and second diodes are connected between respective ends of the third and fourth lines of the second comb line and the ground, the first and second terminals and the first and second diodes are connected to different comb lines. Accordingly, this makes it possible to easily match the impedance of the first comb line and the second comb line seen from the first and second terminals to the characteristic impedance of the high frequency circuit of the mobile communication apparatus on which this variable attenuator is mounted during both the on and off periods of the first and second diodes.
Furthermore, as the variable attenuator is constructed from the first and the second comb lines and the first and second diodes, the configuration of the variable attenuator becomes simple, enabling a compact variable attenuator to be made and its production costs to be reduced.
Since the variable attenuator is provided with a laminated ceramic substrate comprising a plurality of sheet layers made of ceramic, and the ceramic substrate incorporates strip-electrodes which form the first and second lines of the first comb line and the third and fourth lines of the second comb line, it is possible to handle a high frequency band by a wavelength-shortening effect of the ceramic substrate.
It is possible to expand the range of attenuation that can be variably controlled by connecting a plurality of variable attenuators in cascade. Accordingly, the number of components in the mobile communication apparatus in which this composite variable attenuator is mounted can be reduced and as a result, it is possible to achieve compact mobile communication apparatus.
Employment of a compact variable attenuator enables mobile communication apparatus which is compact while maintaining a constant receiving balance in the receiving system.
Employment of a compact composite variable attenuator enables mobile communication apparatus which is compact while maintaining a constant receiving balance in the receiving system.
While particular embodiments of the present invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art without departing from the fair spirit and scope of the invention.
Claims
- 1. A variable attenuator comprising:a first comb line comprising first and second lines which are electromagnetically coupled; a second comb line comprising third and fourth lines which are electromagnetically coupled; a first terminal connected to one end of said first line; a second terminal connected to one end of said second line; first and second diodes connected to said third and fourth lines of said second comb line, said first diode being connected between said third line and a ground with an anode of said first diode connected to one end of said third line, the second diode being connected between said fourth line and the ground with an anode of said second diode connected to one end of said fourth line, the other ends of said first and third lines being connected, and the other ends of said second and fourth lines being connected; a first control terminal connected to the junction of said other end of said first line and said other end of said third line for controlling said first diode to turn on and off; and a second control terminal connected to the junction of said other end of said second line and said other end of said fourth line for controlling said second diode to turn on and off.
- 2. The variable attenuator according to claim 1 wherein said variable attenuator is comprised in a laminated ceramic substrate comprising a plurality of sheet layers made of ceramic, the ceramic substrate having strip-electrodes which form said first and second lines of said first comb line and said third and fourth lines of said second comb line, and said first and second diodes are mounted on the ceramic substrate.
- 3. A mobile communication apparatus comprising a transmitting circuit and a receiving circuit, said variable attenuator according to one of claims 1 and 2 being connected to said transmitting and receiving circuits.
- 4. A mobile communication apparatus according to claim 3, wherein said variable attenuator is comprised in said receiving circuit.
- 5. A mobile communication apparatus according to claim 4, wherein said apparatus has a pair of receiving circuits, each said receiving circuit having a respective said variable attenuator arranged for maintaining a receiving balance between said pair of receiving circuits.
- 6. A composite variable attenuator comprising a plurality of variable attenuators according to one of claims 1 and 2, wherein a plurality of said variable attenuators are connected in cascade by connecting said second terminal of one of said variable attenuators to said first terminal of another of said variable attenuators.
- 7. A mobile communication apparatus comprising a transmitting circuit and a receiving circuit, said composite variable attenuator according to claim 6 being connected to said transmitting and receiving circuits.
- 8. A mobile communication apparatus according to claim 7, wherein said composite variable attenuator is comprised in said receiving circuit.
- 9. A mobile communication apparatus according to claim 8, wherein said apparatus has a pair of receiving circuits, each said receiving circuit having a respective said composite variable attenuator arranged for maintaining a receiving balance between said pair of receiving circuits.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 11-061794 |
Mar 1999 |
JP |
|
US Referenced Citations (10)
