Oscillators – With frequency adjusting means – Step-frequency change
Reexamination Certificate
2002-03-01
2003-07-08
Nuton, My-Trang (Department: 2816)
Oscillators
With frequency adjusting means
Step-frequency change
Reexamination Certificate
active
06590465
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to dual-band oscillators which contain two oscillation circuits and which oscillate in different frequency bands.
2. Description of the Related Art
FIG. 3
is a circuit diagram of a known dual-band oscillator which oscillates in two frequency bands. A first oscillation circuit
41
contains a first common-collector oscillation transistor
42
. The emitter is grounded through a bias resistor
43
. A bias voltage is applied to the base by a first switching transistor
44
. A parallel resonance circuit formed by a first inductor
45
and a first varactor diode
46
for resonance is connected between the base and the ground. A feedback capacitor
47
is connected between the base and the emitter, and a feedback capacitor
48
is connected between the emitter and the ground. The emitter outputs an oscillation signal.
A second oscillation circuit
51
contains a second common-collector oscillation transistor
52
. The emitter is grounded through a bias resistor
53
. A bias voltage is applied to the base by a second switching transistor
54
. A parallel resonance circuit formed by a second inductor
55
and a second varactor diode
56
for resonance is connected between the base and the ground. A feedback capacitor
57
is connected between the base and the emitter, and a feedback capacitor
58
is connected between the emitter and the ground. The emitter outputs an oscillation signal.
A switching voltage for turning ON one of the first switching transistor
44
and the second switching transistor
55
and turning OFF the other is applied to the base of each of the first switching transistor
44
and the second switching transistor
54
. Thus, one of the first oscillation circuit
41
and the second oscillation circuit
51
oscillates. The oscillation frequency can be changed by changing a control voltage applied to the cathode of each of the first and second varactor diodes
46
and
56
.
In the known oscillator, the bias resistors
43
and
53
w connected to the emitters are connected in parallel to the feedback capacitors
48
and
58
, respectively. An oscillation signal current is directed to flow through the bias resistors
43
and
53
. As a result, the oscillation power is reduced, and the phase noise increases.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to easily prevent a reduction in oscillation power, which is caused by an emitter bias resistor in an oscillation transistor, without adding a special circuit or component.
In order to achieve the foregoing objects, a dual-band oscillator according to the present invention is provided including a first oscillation circuit; a second oscillation circuit; and a switching device for alternatively operating the first oscillation circuit and the second oscillation circuit. The first oscillation circuit includes a first oscillation transistor; a first inductance element having one end grounded and the other end coupled to the base of the first oscillation transistor; and a first emitter bias resistor for setting the emitter current of the first oscillation transistor. The second oscillation circuit includes a second oscillation transistor; a second inductance element having one end grounded and the other end coupled to the base of the second oscillation transistor; and a second emitter bias resistor for setting the emitter current of the second oscillation transistor. The first emitter bias resistor is provided between the emitter of the first oscillation transistor and the second inductance element. The second emitter bias resistor is provided between the emitter of the second oscillation transistor and the first inductance element. Accordingly, a loss of oscillation signal of the operative oscillation circuit can be reduced by utilizing the inductance element in the inoperative oscillation circuit.
The switching device may include a first switching transistor and a second switching transistor. The first switching transistor and the second switching transistor may be turned ON/OFF in such a manner that one is ON while the other is OFF. A bias voltage may be applied to the base of the first oscillation transistor by the first switching transistor. A bias voltage may applied to the base of the second oscillation transistor by the second switching transistor. Accordingly, the two oscillation circuits can be switched between operative and inoperative states.
The switching device may include a first switching transistor and a second switching transistor. The first switching transistor and the second switching transistor may be turned ON/OFF in such a manner that that one is ON while the other is OFF. The first switching transistor may be provided in series to the first emitter bias resistor. The second switching transistor may be provided in series to the second emitter bias resistor. Accordingly, the emitter current of each oscillation transistor flowing into each inductance element can be interrupted by each switching transistor.
The first switching transistor may be turned ON/OFF by the second switching transistor. Accordingly, it is only necessary to apply the switching voltage for switching between ON and OFF states to the second switching transistor.
The first inductance element may be provided with a first center tap for dividing the first inductance element into two. The second inductance element may be provided with a second center tap for dividing the second inductance element into two. The first center tap may be grounded through a first capacitor. The second center tap may be grounded through a second capacitor. Accordingly, the high frequency current flowing from the emitter of each oscillation transistor to the ground can be reduced.
A parallel resonance circuit formed by one portion of the divided first inductance element and the first capacitor may be caused to resonate with the oscillation frequency of the second oscillation circuit. A parallel resonance circuit formed by one portion of the divided second inductance element and the second capacitor may be caused to resonate with the oscillation frequency of the first oscillation circuit. Accordingly, the high frequency current flowing from the emitter of each oscillation circuit to the ground can be reduced furthermore.
REFERENCES:
patent: 5852384 (1998-12-01), Sakakura et al.
patent: 5999061 (1999-12-01), Pope et al.
patent: 6008702 (1999-12-01), Yamamoto
patent: 6188295 (2001-02-01), Tsai
patent: 6411168 (2002-06-01), Yoshida
patent: 2001-111342 (2001-04-01), None
patent: 2001-127544 (2001-05-01), None
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Nuton My-Trang
LandOfFree
Dual-band oscillator for preventing reduction in oscillation... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dual-band oscillator for preventing reduction in oscillation..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dual-band oscillator for preventing reduction in oscillation... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3061397