Oscillators – With frequency adjusting means – Variable inductance device
Reexamination Certificate
2000-03-23
2001-10-23
Kinkead, Arnold (Department: 2817)
Oscillators
With frequency adjusting means
Variable inductance device
C336S123000, C336S135000, C334S029000, C331S03600C, C331S10800D
Reexamination Certificate
active
06307440
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an oscillator circuit, an oscillation frequency adjusting method of the oscillator circuit, a tuner, and an oscillation frequency adjusting method of a local oscillation circuit of the tuner suitable for use in a. digital satellite tuner or the like of a receiving apparatus for receiving a digital satellite broadcasting, for example.
A general digital-satellite-broadcasting receiving apparatus includes a digital satellite antenna, a digital satellites converter, a digital satellite tuner and so on. A digital. satellite broadcasting signal from a broadcasting satellite is received by the digital satellite antenna. The digital satellite converter converts this digital satellite broadcasting signal received by the digital satellite antenna to a low-frequency signal having a frequency, for example, ranging from 950 MHz to 2,150 MHz to amplify the latter, and then supplies a high-frequency reception signal thus obtained to the digital satellite tuner.
The digital satellite tuner selects a desired transponder from the high-frequency reception signal and demodulates analog base-band signals (I, Q). The tuner further carries out an A/D conversion of these I and Q signals and demodulates a digital signal by using a QPSK demodulator, thereby outputting the demodulated digital signal by a unit of 8 bits in parallel.
A digital satellite tuner shown in
FIG. 1
has generally been proposed. The digital satellite tuner shown in
FIG. 1
will be described. In
FIG. 1
, reference numeral
1
represents a high-frequency reception signal input terminal supplied with a high-frequency reception signal having a frequency ranging from 950 MHz to 2,150 MHz, for example from the digital satellite tuner. The high-frequency reception signal from the high-frequency reception signal input terminal
1
is supplied to one input terminal of a mixing circuit
5
for converting a frequency through a serial circuit formed by a high-pass filter
1
a
for removing, for example, an intermediate-frequency signal of 479.5 MHz, a high-frequency amplifier circuit
1
b
, a voltage-control type variable band-pass filter
2
for removing, for example, an image frequency signal, an adjacent transponder signal and so on to thereby allow passing of a desired signal out of signals having frequencies ranging from 950 MHz to 2,150 MHz, an automatic gain control circuit
3
and a high-frequency amplifier circuit
4
.
Reference numeral
6
represents a voltage-control type variable frequency oscillator circuit forming a local oscillator
10
. An oscillator at an output side of the voltage-control type variable frequency oscillator circuit
6
is supplied to one input terminal of a phase comparator circuit
7
forming a PLL circuit (phase locked loop circuit).
Reference numeral
8
represents a central processing unit (CPU) for controlling the receiving apparatus. The central processing unit
8
generates a channel selection signal having a frequency corresponding to a desired channel. This channel selection signal having the frequency corresponding to the desired channel is supplied from the central processing unit
8
to the other input terminal of the phase comparator circuit
7
.
The phase comparator circuit
7
compares an oscillations signal from the voltage-control type variable frequency oscillator circuit
6
with the channel selection signal having a frequency corresponding to a desired channel to obtain an error signal at the output side. The phase comparator circuit
7
supplies the error signal obtained at the output side thereof to a control terminal of the voltage-control type variable frequency oscillator circuit
6
through a low-pass filter
9
and also supplies a control voltage corresponding to the channel selection signal obtained at the output side of the low-pass filter
9
, to the variable band-pass filter
2
having a varicap and so on, whose capacitance value changes in response to the control voltage.
This arrangement allows the band-pass filter
2
to remove signals other than a desired signal, e.g., an image frequency signal, a next to adjacent transponder signal and so on.
The voltage-control type variable frequency oscillator circuit
6
controls a frequency of the oscillation signal in response to the error signal obtained at the output side of the low-pass filter
9
. In the voltage-control type variable frequency oscillator circuit
6
, reference numeral
6
a
represents an amplifier circuit unit and reference numeral
6
b
represents a resonator circuit unit.
In this case, the phase comparator circuit
7
, the low-pass filter
9
and voltage-control type variable frequency oscillator circuit
6
form the local oscillator
10
forming the PLL circuit.
A local oscillation signal from the local oscillator
10
is supplied to the other input terminal of the mixing circuit for converting a frequency. The mixing circuit
5
supplies its output signal to an intermediate-frequency output terminal
14
through a serial circuit formed by a surface acoustic wave filter
12
for passing an intermediate-frequency signal and an amplifier circuit
13
. The analog base-band signals (I, Q) are demodulated from the intermediate-frequency signal supplied from the intermediate-frequency output terminal
14
, and A/D conversion of the I and Q signals are carried out to thereby carry out the QPSK demodulation.
In the prior art shown in
FIG. 1
, the mixing circuit
5
, the amplifier circuit unit
6
a
of the voltage-control type variable frequency oscillator circuit
6
, and the intermediate- frequency amplifier circuit
11
form an integrated circuit
15
.
Since the prior art shown in
FIG. 1
employs an upper side heterodyne, if a frequency of the high-frequency reception signal supplied to the one input terminal of the mixing circuit
5
is A, e.g., 950 MHz to 2,150 MHz and a frequency of the intermediate-frequency signal is C, e.g., 479.5 MHz, then a frequency B of the oscillation signal of the local oscillator
10
is
B=A+C.
The frequency B of the oscillation signal of the local oscillator
10
ranges from 1,429 MHz to 2,629.5 MHz, and this range is a very high and wide band.
Since the oscillation signal of the local oscillator
10
of the above digital satellite tuner has a very high frequency and has a very wide band, there are such disadvantages that dispersion in characteristics of an oscillator circuit element, a resonator circuit and so on lead to dispersion in frequencies of the oscillation signal of the local oscillator
10
.
SUMMARY OF THE INVENTION
In view of such aspects, it is an object of the present invention to propose an oscillator circuit and a tuner which can satisfactorily adjust the dispersion in oscillation frequencies.
An oscillator circuit according to the present invention is an oscillator circuit using a pattern coil on a printed-wiring circuit board. The oscillator circuit is arranged such that an air-core coil wound by 0.5 turn or more and less than one turn is connected to the pattern coil in parallel and mounted on the printed-wiring board, and an oscillation frequency is adjusted by adjusting an angle of the air-core coil relative to the printed-wiring board.
According to the present invention, since the air-core coil is connected to the pattern coil in parallel and mounted on the printed-wiring board, a coupling coefficient of induced inductance can be changed by changing the angle of the air-core coil relative to the printed-wiring board. Accordingly, the oscillation frequency can satisfactorily be adjusted without lowering a value Q of the resonator circuit.
According to the present invention, since the air-core coil is wound by 0.5 turn or more and less than one turn and a diameter of the air-core coil is larger than that of the pattern coil, when the air-core coil is mounted on the printed-wiring board, a boundary portion between a leg portion thereof and a coil portion thereof is used for positioning, which facilitates the positioning of the air-core coil.
A tuner according to the present invention is a
Kinkead Arnold
Lerner David Littenberg Krumholz & Mentlik LLP
Sony Corporation
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