Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For high frequency device
Reexamination Certificate
2001-04-25
2003-01-14
Zarabian, Amir (Department: 2824)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For high frequency device
C257S503000, C257S691000, C257S723000
Reexamination Certificate
active
06507111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication apparatus or device such as an optical communication apparatus/device (e.g., a light source or an optical transmitter) and a radio communication apparatus/device (e.g., a portable phone), and more particularly, to a High-Frequency (HF) circuit to be mounted on a communication apparatus/device of this type that prevents its HF characteristic from degrading, and a module equipped therewith.
2. Description of the Related Art
With optical communications systems, signal light is generated by direct or indirect modulation method of the output light of a semiconductor laser as a light source according to a signal to be transmitted in the transmission side. Then, the signal light thus generated is sent to an optical detector in the reception side by way of a medium.
In the direct modulation method of light, a semiconductor laser itself is driven with an intensity- or frequency-modulated current according to a signal to be transmitted, thereby generating the signal light. On the other hand, in the indirect modulation method of light, a semiconductor laser is driven with a dc current to generate output light with a constant intensity and then, the output light thus generated is modulated by an intensity-, frequency-, or phase-modulation method with an external modulator according to a signal to be transmitted, thereby generating the signal light.
As known well, when the bit rate of information is in the order of gigabits per second (i.e., Gb/sec) or higher, the transmittable distance is limited due to wavelength chirping occurring in the direct modulation method. Therefore, the indirect modulation method of light is used for transmission at such the high bit rate as above.
It is usual that an external modulator is formed in the form of module. For example, only an external modulator is formed as a module. Alternately, an external modulator and a light source (e.g., a semiconductor laser) are combined together to form a module, which is termed the “modulator-integrated light source” module.
In recent years, the bit rate of information or data to be transmitted has been becoming higher (e.g., Gb/sec or higher). Therefore, to transmit the information from the transmission side to the reception side without any errors, there is the increasing need to improve the high-frequency characteristics of the external modulator. To meet this need, various improved modules of this type have been developed and disclosed.
FIGS. 1 and 2
show the configuration of an example of the prior-art modulator-integrated light source modules. As seen from these figures, on a conductive base
101
, a dielectric substrate
102
and a heat sink
103
are formed to be apart from each other at a small distance. The dielectric substrate
102
is, for example, made of alumina (Al
2
O
3
). The sink
103
is made of material with high thermal conductivity.
A modulator-integrated light source chip
120
is mounted on the sink
103
, where the chip
120
comprises a semiconductor laser
109
and an external modulator
110
. The sink
103
serves to cool the chip
120
, i.e., to dissipate the heat generated by the chip
120
. The sink
103
is mechanically and electrically connected to the base
101
by way of a conductive via hole
111
b.
On the surface of the dielectric substrate
102
, a patterned conductive layer is deposited, forming a strip-shaped signal line
107
and two ground lines
108
a
and
108
b
at each side of the signal line
107
. The surface of the substrate
102
is exposed from the lines
107
,
108
a
and
108
b
through two elongated windows. The signal line
107
and the ground lines
108
a
and
108
b
constitute a coplanar-type transmission line. The ground lines
108
a
and
108
b
are mechanically and electrically connected to the base
101
by way of conductive via holes
111
a
. The signal line
107
is not electrically connected to the base
101
.
A matching resistor
104
, which serves as a terminator for impedance matching, is formed on the exposed surface of the dielectric layer
102
between the signal line
107
and the ground line
108
b
. The resistor
104
is located near the end of the signal line
107
, which is in the vicinity of the heat sink
103
. The two ends of the resistor
104
are mechanically and electrically connected to the lines
107
and
108
b
, respectively. The resistor
104
is of the chip type or thin-film type.
The signal line
107
is electrically connected to the heat sink
103
by way of a conductive bonding wire
105
. One end of the wire
105
is bonded to the nearer end of the line
107
to the sink
103
. The other end of the wire
105
is bonded to the sink
103
at its nearest edge to the line
107
. The heat sink
103
is electrically connected to the external modulator
110
of the chip
120
by way of a conductive bonding wire
106
. One end of the wire
106
is bonded to the sink
103
at its nearest edge to the line
107
. The other end of the wire
106
is bonded to the pad of the modulator
110
of the chip
120
. The laser
109
is supplied with an electric, driving current by way of a conductive bonding wire
112
.
A high-frequency electrical input signal S
IN
to be transmitted is applied to the signal line
107
from its furthest end from the heat sink
103
. The signal S
IN
is then sent to the external modulator
110
of the modulator-integrated light source chip
120
by way of the signal line
107
, the bonding wires
105
and
106
, and the sink
103
. The modulator
110
modulates the output light of the laser
109
according to the signal S
IN
thus inputted, generating the signal light. The signal light thus generated is emitted from the chip
120
and the modulator-integrated light source module.
With the prior-art module shown in
FIGS. 1 and 2
, as described above, the external modulator
110
of the modulator-integrated light source chip
120
and the dielectric substrate
102
are located to be apart from each other at a specific small distance, thereby decreasing the lengths of the bonding wires
105
and
106
. Thus, the inductance components of the wires
105
and
106
are restricted, suppressing the degradation of the high-frequency characteristic of the modulator
110
.
However, it is often that the distance between the dielectric substrate
102
and the modulator-integrated light source chip
120
is unable or difficult to be short as desired due to requirements in designing the module of this type. In other words, the bonding wires
105
and
106
are often unable to be short as desired. As a result, there is a limit in the method of preventing degradation of the high-frequency characteristic of the module by decreasing the lengths of the bonding wires. It is preferred that this problem is solved by a different method if possible.
In addition, the Japanese Non-Examined Patent Publication No. 10-275957 published in 1998 discloses an optical semiconductor chip carrier. This carrier comprises the same technique as described above while a microstrip line is used as the transmission line for the input signal S
IN
into the external modulator
110
.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a high-frequency circuit that makes it possible to prevent degradation of its high-frequency characteristic by a different method from the above-described method of decreasing the lengths of bonding wires used.
Another object of the present invention is to provide a high-frequency circuit module that makes it possible to prevent degradation of its high-frequency characteristic by a different method from the above-described method of decreasing the lengths of bonding wires used.
The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description.
According to a first aspect of she present invention, a high-frequency circuit is provided, which comprises:
(a) an electronic element having a capacitance;
(b) a signal line for tr
Katten Muchin Zavis & Rosenman
Menz Douglas
Zarabian Amir
LandOfFree
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