Oscillators – Solid state active element oscillator – Transistors
Reexamination Certificate
2000-08-30
2002-03-19
Kinkead, Arnold (Department: 2817)
Oscillators
Solid state active element oscillator
Transistors
C331S1170FE, C331S1070SL, C331S10800D
Reexamination Certificate
active
06359522
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a voltage-controlled oscillator and particularly to a voltage-controlled oscillator in which an oscillating transistor and an amplifying transistor are connected in series in a DC manner and a resonance circuit is connected to the collector of oscillating transistor in view of preventing generation of irregular oscillation and enabling output level adjustment of the oscillation signal.
2. Description of the Related Art
There has been provided a voltage-controlled oscillator wherein an oscillating transistor and an amplifying transistor are connected in a DC manner and a resonance circuit is connected to the collector of the oscillating transistor. This voltage-controlled oscillator supplies an oscillation signal output from the emitter of an oscillating transistor to the base of an amplifying transistor, and outputs the oscillation signal from the collector of an amplifying transistor. Moreover, in this voltage-controlled oscillator, an irregular oscillation signal is sometimes generated in the frequency considerably lower than the frequency of oscillation signal with the influence of inductance connected in series to the collector of the oscillating transistor, and thereby generation of the irregular oscillation signal interferes with the intrinsic oscillation signal. Therefore, the irregular oscillation control circuit to control generation of irregular oscillation signal is, in more practical terms, an irregular oscillation control circuit connecting in series an inductor and a resistor connected to a series circuit between the collector of the oscillating transistor and the emitter of amplifying transistor.
Here,
FIG. 4
is a circuit diagram illustrating an example of the structure of the well-known voltage controlled oscillator explained above.
As illustrated in
FIG. 4
, the typical voltage-controlled oscillator is composed of an oscillating active circuit portion
41
, a resonance circuit portion
42
, an oscillation signal output terminal
43
, a power supply terminal
44
, a frequency setting voltage supply terminal
45
and an irregular oscillation control circuit
46
.
In this case, the oscillating active circuit portion
41
comprises a first transistor (oscillating transistor)
41
1
, a second transistor (amplifying transistor)
41
2
, a first coupling capacitor
41
3
, a first feedback capacitor
41
4
, a second feedback capacitor
41
5
, an emitter resistor
41
6
, a second coupling capacitor
41
7
, a first base bias setting resistor
41
8
, a second base bias setting resistor
41
9
, a third base bias setting resistor
41
10
, a first bypass capacitor
41
11
, a second bypass capacitor
41
12
, a third coupling capacitor
41
13
, a load inductor
14
14
, a smoothing capacitor
41
15
, and also an irregular oscillation control circuit
46
. The resonance circuit portion
42
comprises a resonance inductor
42
1
, a varactor diode
42
2
, a DC cut-off capacitor
42
3
, a buffer inductor
42
4
, and a smoothing capacitor
42
5
. The resonance circuit portion
42
forms a resonance circuit mainly with the resonance inductor
42
1
, and the varactor diode
42
2
. The irregular oscillation control circuit
46
comprises an inductor
46
1
, and a resistor
46
2.
Each structural element
41
1
to
41
15
forming the oscillating active circuit portion
41
and each structural element
42
1
to
42
5
forming the resonance circuit portion
42
are connected as illustrated in FIG.
4
.
The well-known voltage controlled oscillator of the structure explained above operates as will be explained below.
When a frequency setting voltage is applied to a frequency setting voltage supply terminal
45
, this frequency setting voltage is impressed to a cathode of the varactor diode
42
2
through the buffer inductor
42
4
to set a capacitance value of the varactor diode
42
2
corresponding to the frequency setting voltage. In this case, a resonance circuit consisting of the resonance inductor
42
1
and varactor diode
42
2
resonates at the frequency determined by the inductance value of resonance inductor
42
1
and capacitance value of varactor diode
42
2
. During resonance of the resonance circuit, the oscillating active circuit portion
41
shows a negative resistance when the oscillation active circuit portion
41
is viewed from the resonance circuit portion
42
. Therefore, a signal in the frequency identical to the resonance frequency is generated in the resonance circuit
42
. When the frequency setting voltage to be supplied to the frequency setting voltage supply terminal
45
is changed, the capacitance value of the varactor diode
42
2
changes depending on such change and thereby the frequency of the frequency signal generated in the resonance circuit
42
also changes.
The oscillating active circuit portion
41
outputs, when the signal in the frequency identical to the resonance frequency is generated in the resonance circuit, such frequency signal from the emitter of the first transistor
41
1
as the oscillation signal and supplies this oscillation signal to the base of the second transistor
41
2
via the second coupling capacitor
41
7
. The second transistor
41
2
amplifies the supplied oscillation signal under the grounded-emitter system and supplies the oscillation signal to the oscillation signal output terminal
43
from its collector via the third coupling capacitor
41
13
.
The oscillating active circuit portion
41
inserts an irregular oscillation control circuit
46
connecting in series the inductor
46
1
and the resistor
46
2
within the DC circuit between the collector of the first transistor
41
1
and the emitter of the second transistor
41
2
. This irregular oscillation control circuit
46
impedes the irregular oscillation signal which is generated in the frequency considerably lower than the oscillation frequency signal supplied to the emitter of the second transistor
41
2
from the collector of first transistor
41
1
and also prevents, with connection of the irregular oscillation control circuit
46
, that the irregular oscillation signal is supplied to the oscillation signal output terminal via the third coupling capacitor
41
13
from the collector of the second transistor
41
2
.
In this case, a resistor
46
2
used in the irregular oscillation control circuit
46
preferably has a resistance value as small as possible because it is connected to a DC circuit and generally it has the resistance value of 10 to 50 &OHgr;.
The well-known voltage controlled oscillator described above has a merit that it can output the oscillation signal of the predetermined frequency band without generation of irregular oscillation; but it requires, on the other hand, insertion of the irregular oscillation control circuit
46
connecting in series the inductor
46
1
and resistor
46
2
within the oscillating active circuit portion
41
in order to control the irregular oscillation signal. Therefore, the number of parts increases and manufacturing cost rises as much in comparison with the voltage-controlled oscillator of this type where the irregular oscillation control circuit
46
is not inserted.
Moreover, the voltage-controlled oscillator of the related art includes an inductor
46
1
which is a large size electronic part requiring a large physical volume within the irregular oscillation control circuit
46
inserted to the oscillating active circuit portion
41
and therefore it is considerably difficult to reduce the size of total structure of the voltage-controlled oscillator.
Moreover, the voltage-controlled oscillator of the related art does not include an oscillation signal output level adjusting member. Accordingly, when it is requested to adjust the oscillation signal output level, the second transistor
41
2
must be replaced with one having a different amplification degree and the second coupling capacitor
41
7
must be replaced with one having a different capacitance value. Namely, many adjusting processes are required for output level adjustment
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Kinkead Arnold
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