Oscillators – L-c type oscillators
Reexamination Certificate
1999-03-29
2001-02-27
Grimm, Siegfried H. (Department: 2817)
Oscillators
L-c type oscillators
C331S179000, C331S181000
Reexamination Certificate
active
06194976
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention is directed generally to an apparatus and method for voltage controlled oscillation and, more particularly, to a multiple band voltage controlled oscillator using impedance scaling, and a method of providing multiple bands for a voltage controlled oscillator.
II. Description of the Background
Mobile telephone receivers typically require the use of a voltage controlled oscillator (VCO) with a specific center frequency in order to process incoming signals. In mobile telephones that are adapted to operate in multiple modes, separate voltage controlled oscillator circuits, each of which has a center frequency associated with one of the modes, are typically required to be present in the telephones in order to process received signals in the multiple modes.
The use of multiple VCO circuits in multiple mode telephones increases the number of components required to implement such devices, and such circuits occupy valuable space on the circuit boards used for implementing the telephone. It would therefore be desirable to eliminate the need for multiple, separate VCO's in multiple mode phones.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed to a multiple band voltage controlled oscillator (VCO) using impedance scaling. In one embodiment of the present invention, the multiple band voltage controlled oscillator includes a tank circuit, which includes diodes, a capacitance, and an inductance, a PIN diode connected across part of the inductance of the tank circuit, a switch connected to selectively enable the PIN diode and correspondingly partially short the inductance of the tank circuit, and an oscillator circuit responsively connected to the PIN diode. Toggling of the switch causes the center frequency associated with the operating frequency range of the VCO to shift between two values, f
1
and f
2
. More particularly, actuation of the switch causes the inductance associated with the VCO to vary, thereby shifting the center frequency of the VCO between the f
1
and f
2
values.
The present invention also includes a method of providing multiple bands for a voltage controlled oscillator. The method includes providing a tank circuit with a radio frequency impedance, adjusting the radio frequency impedance of the tank circuit by selectively shorting a portion of the radio-frequency impedance using a PIN diode activated by a switch, and varying the output of the voltage controlled oscillator based on the radio-frequency impedance present using a base band oscillator.
The present invention solves problems experienced with the prior art. The use of multiple sets of frequency generating circuitry is avoided by the use of the present invention, thus avoiding the corresponding increased materials cost, degradation of performance, and variable sensitivity parameters. Those and other advantages and benefits of the present invention will become apparent from the description of the preferred embodiments hereinbelow.
REFERENCES:
patent: 3889210 (1975-06-01), Matsuura et al.
patent: 4353038 (1982-10-01), Rose et al.
patent: 4598423 (1986-07-01), Hettiger
patent: 5535443 (1996-07-01), Wignot
patent: 0270298 (1988-06-01), None
patent: 2240227 (1991-07-01), None
Cantey, III Patrick S.
Pitta Thomas A.
Saldana Rolando A.
Brown Charles
Grimm Siegfried H.
Qualcomm Incorporated
Streeter Tom
Wadsworth Phillip
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