Oscillators – Solid state active element oscillator – Transistors
Reexamination Certificate
1999-07-23
2001-02-27
Lee, Benny (Department: 2817)
Oscillators
Solid state active element oscillator
Transistors
C331S179000
Reexamination Certificate
active
06194974
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a voltage controlled oscillator and, in particular, to a voltage controlled oscillator operable over a wide range of frequencies.
A band switching voltage controlled oscillator is described in U.S. Pat. No. 5,739,730 given to Rotzoll. The band switching of Rotzoll relies on diodes such as varactor diodes being added selectively to a tuning circuit by switches.
In the above-mentioned voltage controlled oscillator, switching is carried out of the components in and out of the tuning circuit operating at radio frequency. This results in the introduction of unwelcome circuit parasitics. Also in applications for which it is important to minimize equipment volume and the number of components used, improvements over the prior art are necessary.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a voltage controlled oscillator of smaller volume and with fewer components, capable of operating within a number of different frequency bands.
It is another object of this invention to avoid the unnecessary circuit parasitics introduced by band switching in the radio frequency circuit.
According to this invention, there is provided voltage controlled oscillator which comprising a valve control element having a control terminal, a resonance circuit having an inductance element connected to the control terminal, and a tuning terminal for applying a tuning voltage to the resonance circuit. In the voltage controlled oscillator, the resonance circuit comprises a first band selection terminal to be applied with a selection voltage for selecting a frequency band, a zeroth varactor diode having a cathode connected to the inductance element, and a first varactor diode having an anode connected to the first band selection terminal and a cathode connected to the inductance element.
According to this invention, there is also provided a voltage controlled oscillator comprising an active circuit including a transistor or the like and a tuning circuit. The tuning circuit has inductance and capacitance comprising a plurality of varactor diodes in parallel. At least one of the varactor diodes remains in the high capacitance, “on” state. Further varactor diodes remain in circuit and are changed selectively from a high capacitance “on” state to a low capacitance “off” state to alter the frequency tuning range of the voltage controlled oscillator.
REFERENCES:
patent: 4494081 (1985-01-01), Lea et al.
patent: 4593255 (1986-06-01), Matsuura
patent: 5144264 (1992-09-01), Chong et al.
patent: 5231361 (1993-07-01), Smith et al.
patent: 5739730 (1998-04-01), Rotzoll
patent: 5982243 (1999-11-01), Pope
Craig Allen
Rostbakken Olaf
Choe Henry
Lee Benny
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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