Oscillators – Solid state active element oscillator – Transistors
Reexamination Certificate
2001-04-17
2003-06-17
Pascal, Robert (Department: 2817)
Oscillators
Solid state active element oscillator
Transistors
C331S17700V
Reexamination Certificate
active
06580331
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to a voltage controlled oscillator, and more particularly, to a voltage controlled oscillator that oscillates in a high frequency band.
2. Description of the Related Art
FIG. 5
illustrates a conventional voltage controlled oscillator. The collector of an oscillating transistor
21
is coupled to a ground through a capacitor
22
. A feedback capacitor
23
connects the base to the emitter of the oscillating transistor
21
, and a capacitor
24
connects the emitter of the oscillating transistor
21
to ground.
A resonant circuit
25
is connected to the base of the oscillating transistor
21
. The resonant circuit
25
includes a microstrip
25
a,
a first and a second varactor diode
25
b
and
25
c.
The cathodes of the varactor diodes
25
b
and
25
c
are interconnected in series. The anode of the first varactor diode
25
b
is grounded, and the anode of the second varactor diode
25
c
is connected to the microstrip
25
a
through a capacitor
25
d.
The microstrip
25
a
is directly connected to ground and indirectly connected to the base of the oscillating transistor
21
through a capacitor
25
e.
The microstrip
25
a
is a linear conductor. The length of the microstrip
25
a
is slightly shorter than a quarter of the wavelength of an oscillation frequency.
The anode of the second varactor diode
25
c
is grounded through an inductor
26
. A control voltage is applied to the cathode of the first varactor diode
25
b
and the cathode of the second varactor diode
25
c
through an inductor
27
. By varying the control voltage, the oscillation frequency is adjusted.
In the above-described circuit, the internal capacitance of each of the varactor diodes
25
b
and
25
c
is controlled by the inductive and capacitive coupling circuit. To oscillate at a high frequency, the capacitance increases, while the Q factor of the resonant circuit decreases. Hence the carrier-to-noise (C/N) ratio of the oscillation signal decreases.
SUMMARY
According to a first aspect, a voltage controlled oscillator includes an oscillating transistor. The collector of the oscillating transistor is coupled to ground when the oscillating transistor generates a high frequency output. A microstrip is coupled to the base of the oscillating transistor through a first varactor diode and a capacitor. A second varactor diode couples the microstrip to ground. The length of the microstrip is preferably within about ½ to about ¾ of the oscillation frequency of the voltage controlled oscillator.
Preferably, a cathode of the first varactor diode is coupled to a first end of the microstrip and an anode of the first varactor diode is preferably coupled to ground through a first inductor. Preferably, a cathode of the second varactor diode is coupled to a second end of the microstrip and an anode of the second varactor diode is preferably grounded. A control voltage is preferably supplied to the cathodes of the first and second varactor diodes by a power source or a bias circuit.
Preferably, the microstrip is longer than the above-described conventional microstrip, and hence, the Q factor of a resonant circuit increases. As a result, the C/N ratio of an oscillation signal increases, and the deterioration of the Q factor of the resonant circuit, tuned by the control voltage, does not occur or is minimized. Moreover, the second inductor does not require a large inductance, and hence, the second inductor can be replaced by a second microstrip. Preferably, the second microstrip is shorter than the microstrip coupled between the first and second varactor diodes.
REFERENCES:
patent: 4189690 (1980-02-01), Bock et al.
patent: 4684904 (1987-08-01), Watkins et al.
patent: 5859573 (1999-01-01), Kukkonen
patent: 5900788 (1999-05-01), Hagemeyer
patent: 5905414 (1999-05-01), Motoi
patent: 6169461 (2001-01-01), Andoh et al.
patent: 60018024 (1985-01-01), None
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Chang Joseph
Pascal Robert
LandOfFree
Voltage controlled oscillator for oscillating signals with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Voltage controlled oscillator for oscillating signals with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Voltage controlled oscillator for oscillating signals with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3089080