Oscillators – With distributed parameter resonator
Reexamination Certificate
2000-12-22
2002-09-24
Mis, David (Department: 2817)
Oscillators
With distributed parameter resonator
C331S10800D, C331S1170FE, C331S1170FE, C331S175000, C331S17700V, C331S179000
Reexamination Certificate
active
06456169
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a voltage-controlled oscillator and an electronic device incorporating a voltage-controlled oscillator, or more particularly, the present invention relates to a voltage-controlled oscillator adaptable to communication devices and an electronic device incorporating the voltage-controlled oscillator.
2. Description of the Related Art
In recent years, a voltage-controlled oscillator having a frequency of oscillation that can be varied diversely has been demanded for use with various electronic devices including a portable telephone. For providing the voltage-controlled oscillator having a frequency of oscillation that can be varied diversely, a new printed-circuit board may be designed for each frequency of oscillation. However, this approach has enormous costs. According to an alternative approach, an inductive component to be included in a resonant circuit is realized with a strip line, the stripline is scraped in order to vary the inductance of the inductive component, and thus, the frequency of oscillation of a voltage-controlled oscillator is varied.
Moreover, for designing a voltage-controlled oscillator, simulation is often carried out using a computer. However, there is an error between a theoretical value determined via simulation and a measured value obtained using a prototype. A generally adopted procedure for correcting the error is to scrape a strip line included in the resonant circuit so as to change the inductance of the inductive component.
Moreover, the work for adjusting electrical characteristics such as a carrier-to-noise ratio includes scraping of the strip line included in the resonant circuit.
FIG. 6
shows a conventional voltage-controlled oscillator. Referring to
FIG. 6
, a voltage-controlled oscillator
3
consists mainly of a resonant circuit
31
and an amplification circuit
12
. The resonant circuit
31
has one terminal of an inductor L
1
, which is a strip line, connected to the amplification circuit
12
via a capacitor C
2
. The other terminal of the inductor L
1
is connected to the cathode of a variable-capacitance diode VD
1
. The cathode of the variable-capacitance diode VD
1
is connected to a control voltage terminal a
2
via an inductor L
3
that is a choke coil. The anode of the variable-capacitance diode VD
1
is grounded. The capacitor C
2
is a coupling capacitor.
The resonant circuit
31
is connected to the base of a transistor Tr
1
which functions as an amplification element in the amplification circuit
12
. The emitter of the transistor Tr
1
is connected to an output terminal a
3
via a capacitor C
7
. The collector of the transistor Tr
1
is grounded via a capacitor C
4
. A power terminal a
4
is grounded via a capacitor C
5
, and connected to the collector of the transistor Tr
1
via an inductor L
4
that is a choke coil. The base and emitter of the transistor Tr
1
are biased by resistors R
1
, R
2
, and R
3
. A capacitor C
3
is connected between the base and emitter of the transistor Tr
1
.
In the thus-configured voltage-controlled oscillator
3
, the inductance of the inductor L
1
is adjusted in order to vary the frequency of oscillation of the voltage-controlled oscillator or improve the electrical characteristics thereof such as a carrier-to-noise ratio. The inductor L
1
is a circuit element enabling variation of the frequency of oscillation and greatly contributing to the electric characteristic such as the carrier-to-noise ratio.
Moreover, in the thus-configured voltage-controlled oscillator
3
, the variable-capacitance diode VD
1
and inductor L
1
are connected in series with each other to thus realize a series resonant circuit suitable for expanding a frequency band within which the frequency of oscillation can be varied. The series resonant circuit has a property that when the frequency band within which the frequency of oscillation is variable is larger than 10% of the frequency of oscillation, a loss caused by the resonant circuit
31
hardly depends on the frequency of oscillation.
In the voltage-controlled oscillator
3
, the inductor L
1
included in the resonant circuit
31
having the series resonant circuit and realized with a strip line is scraped using a laser in order to vary the frequency of oscillation of the voltage-controlled oscillator and to improve the electrical characteristics thereof such as a carrier-to-noise ratio.
However, since a major signal passes through the inductor L
1
, when the inductor L
1
must be adjusted, quite delicate and very accurate adjustment is required. This poses a problem in that manufacturing efficiency is degraded. Moreover, since the major signal passes through the inductor L
1
, when the inductor L
1
is adjusted, the electrical characteristics of the voltage-controlled oscillator
3
is likely to be degraded or the frequency of oscillation thereof is likely to be unstable. Moreover, the step of scraping the inductor L
1
is needed for every product. This degrades the manufacturing efficiency. These problems become more serious when the frequency band within which the frequency of oscillation is variable is wider.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a voltage-controlled oscillator having a frequency of oscillation that is readily varied and an electrical characteristic thereof such as a carrier-to-noise ratio readily improved even when a frequency band within which the frequency of oscillation is variable is wide.
Other preferred embodiments of the present invention provide a voltage-controlled oscillator having a frequency of oscillation can be varied greatly without the necessity of scraping a strip line.
Further preferred embodiments of the present invention provide a voltage-controlled oscillator having an electric characteristic thereof that is not degraded and a frequency of oscillation thereof that is stable even when a strip line is scraped in order to adjust part of a resonant circuit for the purpose of varying the frequency of oscillation or improving the electrical characteristics thereof such as a carrier-to-noise ratio.
According to one preferred embodiment of the present invention, a voltage-controlled oscillator includes a resonant circuit and an amplification circuit. The resonant circuit includes an inductor having one terminal that is connected to the amplification circuit and another terminal that is grounded via a variable-capacitance diode, and a land to which a capacitor can be mounted. The first land has one terminal thereof connected to one terminal of the inductor and the other terminal thereof connected to the other terminal of the inductor.
Moreover, according to other preferred embodiments of the present invention, a voltage-controlled oscillator includes a resonant circuit and an amplification circuit. The resonant circuit includes an inductor having one terminal that is connected to the amplification circuit and another terminal that is grounded via a variable-capacitance diode, and a land to which a capacitor can be mounted. The land has one terminal thereof connected to one terminal of the inductor and the other terminal thereof grounded.
Moreover, according to other preferred embodiments of the present invention, a voltage-controlled oscillator includes a resonant circuit and an amplification circuit. The resonant circuit includes an inductor having one terminal that is connected to the amplification circuit and another terminal that is grounded via a variable-capacitance diode, and first and second lands to which a capacitor can be mounted. The first land has one terminal thereof connected to one terminal of the inductor and the other terminal thereof connected to the other terminal of the inductor. The second land has one terminal thereof connected to one terminal of the inductor and the other terminal thereof grounded.
Moreover, according to other preferred embodiments of the present invention, a voltage-controlled oscillator has a transmission l
Goma Shinji
Oshita Teruaki
Keating & Bennett LLP
Mis David
Murata Manufacturing Co. Ltd.
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