Oscillators – Solid state active element oscillator – Transistors
Reexamination Certificate
2003-06-03
2004-09-14
Kinkead, Arnold (Department: 2817)
Oscillators
Solid state active element oscillator
Transistors
C331S17700V, C331S17700V, C331S1070DP, C331S10800D
Reexamination Certificate
active
06791426
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a balanced oscillator and an electronic apparatus including the same, and more specifically to a balanced voltage-controlled oscillator for use as a local oscillator in a cellular telephone, for example, and an electronic apparatus including the balanced voltage-controlled oscillator.
2. Description of the Related Art
In communication devices such as cellular telephones, oscillators such as voltage-controlled oscillators are used as local oscillators. Recently, with the popularity of integrated circuits within communication devices, the adoption of balanced signal processors has increased due to its resistance to common mode noise in its signal paths, and the demands for balanced oscillators capable of obtaining a balanced output have also increased.
FIG. 4
is a circuit diagram of a balanced oscillator
1
of the related art. In
FIG. 4
, the balanced oscillator
1
includes a differential oscillator circuit
2
and a differential amplifier circuit
3
.
The differential oscillator circuit
2
includes transistors Q
1
and Q
2
, resistors R
1
and R
2
, capacitors C
1
, C
2
, and C
3
, inductors L
1
and L
2
, varactor diodes VD
1
and VD
2
, and a constant current source I
1
. The transistor Q
1
has a collector connected with a d.c. power supply Vdc via the inductor L
1
, and a base connected with a bias power supply Vb via the resistor R
1
. The transistor Q
2
has a collector connected with the d.c. power supply Vdc via the inductor L
2
, and a base connected with the bias power supply Vb via the resistor R
2
. The emitters of the transistors Q
1
and Q
2
are connected with each other and are also connected with a ground via the constant current source I
1
. The base of the transistor Q
1
is connected to the collector of the transistor Q
2
via the capacitor C
1
, and the base of the transistor Q
2
is connected to the collector of the transistor Q
1
via the capacitor C
2
. The collectors of the transistors Q
1
and Q
2
are connected with each other via the capacitor C
3
. The collector of the transistor Q
1
is further connected to a control voltage input terminal Vc via the varactor diode VD
1
, and the collector of the transistor Q
2
is also connected to the control voltage input terminal Vc via the varactor diode VD
2
.
In the differential oscillator circuit
2
of such a structure, the transistors Q
1
and Q
2
are cross-connected with each other via the capacitors C
1
and C
2
to perform differential oscillation at a frequency defined by the capacitance of the capacitors C
1
through C
3
, the inductance of the inductors L
1
and L
2
, and the capacitance of the varactor diodes VD
1
and VD
2
. The differential oscillator circuit
2
has two outputs led from the collectors of the transistors Q
1
and Q
2
. As is anticipated from the fact that the differential oscillator circuit
2
includes the varactor diodes VD
1
and VD
2
, the differential oscillator circuit
2
is a voltage-controlled oscillating circuit; however, this is not an essential point to the present invention and a description thereof is thus omitted.
The differential amplifier circuit
3
includes transistors Q
3
and Q
4
, and a constant current source I
2
. The transistor Q
3
has a collector connected with the d.c. power supply Vdc, an emitter connected with an output terminal P
1
, and a base connected with the collector of the transistor Q
1
. The transistor Q
4
has a collector connected with the d.c. power supply Vdc, an emitter connected with an output terminal P
2
, and a base connected with the collector of the transistor Q
2
. The emitters of the transistors Q
3
and Q
4
are connected with each other and are also connected with the ground via the constant current source I
2
.
The differential amplifier circuit
3
of such a structure receives and differentially amplifies the two differential output signals of the differential oscillator circuit
2
. The differential amplifier circuit
3
has two outputs led to the output terminals P
1
and P
2
from the emitters of the two transistors Q
3
and Q
4
, respectively.
In the balanced oscillator
1
of the related art, the differential oscillator circuit
2
and the differential amplifier circuit
3
are connected in parallel to the d.c. power supply Vdc in an independent manner. This requires separate constant current sources for driving the differential oscillator circuit
2
and the differential amplifier circuit
3
, thus making it difficult to achieve low current consumption.
SUMMARY OF THE INVENTION
In order to overcome the foregoing problem, the present invention provides a compact balanced oscillator with low current consumption, and an electronic apparatus including the balanced oscillator.
In an aspect of the present invention, a balanced oscillator includes a differential oscillator circuit having two output terminals, and a differential amplifier circuit having two input terminals each being connected with each of the two output terminals of the differential oscillator circuit. The direct-current path of the differential oscillator circuit is connected in series with the direct-current path of the differential amplifier circuit.
Either one of the differential oscillator circuit and the differential amplifier circuit may be connected so as to operate as a constant current source of the other.
In another aspect of the present invention, an electronic apparatus includes the above-noted balanced oscillator.
Therefore, a balanced oscillator according to the present invention and an electronic apparatus including the balanced oscillator can achieve low current consumption and size reduction.
Other features and advantages of the present invention will become apparent from the following description of embodiments of the invention which refers to the accompanying drawings.
REFERENCES:
patent: 4270102 (1981-05-01), Gawler et al.
patent: 6411170 (2002-06-01), Hino
Kinkead Arnold
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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