Oscillators – Solid state active element oscillator – Transistors
Reexamination Certificate
1999-11-22
2001-04-10
Kinkead, Arnold (Department: 2817)
Oscillators
Solid state active element oscillator
Transistors
C331S144000, C331S176000, C331S17700V, C331S11300A
Reexamination Certificate
active
06215369
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a controllable oscillator, in particular a current controlled oscillator.
BACKGROUND ART
Controllable oscillators are a type of component which are very common in modem electronics. Such oscillators can either be voltage controlled, so-called VCOs (Voltage Controlled Oscillator), or current controlled, CCOs (Current Controlled Oscillator). What is controlled in a CCO/VCO is the output frequency of the oscillator.
It is of course important that the frequency of a controllable oscillator can be controlled over a wide range without the amplitude of the signal varying too much, that the noise level of the signal is low, and that the frequency can be high. Taking into account trends in modem electronics, it is also important that a controllable oscillator takes up as little space as possible, and of course that it is as cheap as possible.
DESCRIPTION OF THE INVENTION
The problem to be solved by the present invention is thus to produce a controllable oscillator which can have a high output frequency with a low noise level, is compact, cheap to produce, and has a broad modulation range with retained amplitude.
This problem is solved using a controllable oscillator which comprises a first and a second amplifier which are provided with inputs for supply voltage and at least one controllable current source for controlling the output frequency of the oscillator. Each amplifier comprises a first and a second branch, where both the first and the second branch have an input and an output for electrical signals.
The output of the first branch of the first amplifier is connected to the input of the second branch of the second amplifier, and the output of the second branch of the first amplifier is connected to the input of the first branch of the second amplifier. In addition, the output of the first branch of the second amplifier is connected to the input of the first branch of the first amplifier, and the output of the second branch of the second amplifier is connected to the input of the second branch of the first amplifier.
In a variant of the invention, the controllable oscillator also comprises a third and a fourth amplifier, which amplifiers each have an input and an output for electrical signals, and a controllable current source for controlling the output frequency of the oscillator. In this embodiment, the output of the first branch of the first amplifier is connected to the input of the fourth amplifier, and the output of the second branch of the first amplifier is connected to the input of the third amplifier. The output of the third amplifier is connected to the input of the first branch of the second amplifier, and the output of the fourth amplifier is connected to the input of the second branch of the second amplifier.
In both these variants of the invention, the first and second branches of the first and the second amplifier each preferably comprise a resistance connected in series with a transistor. This design of the amplifiers make the oscillator according to the invention compact and cheap to produce.
In both the abovementioned variants of the invention, the output of the first branch of the first amplifier is fed back to the input of the first branch of the first amplifier, and the output of the second branch of the first amplifier is fed back to the input of the second branch of the first amplifier. Both of these feedbacks are suitably done via means for reducing the DC level of the signals from the outputs and for matching the impedances between the first and the second amplifier.
In addition, in both the abovementioned variants of the invention, the outputs of the first amplifier are also suitably connected to the respective next amplifier via means for reducing the DC level of the signal from the outputs of the first amplifier and for matching the impedances between the first amplifier and the next amplifier.
If the feed-back in the first amplifier comprises means for connecting the outputs of the first amplifier to the respective next amplifiers, and these means comprise a transistor, the compact and cheap design of the oscillator is retained.
In addition, in an oscillator according to the invention there is preferably a phase shift between the signals at the outputs of the first and second branches of the respective amplifiers, which suitably amounts to 180 degrees.
In addition to the advantages mentioned above, an oscillator according to the invention has a low power consumption, is relatively unaffected by temperature and is relatively unaffected by interference. As an oscillator according to the invention can be constructed without external components, it can in addition be integrated in a single chip.
REFERENCES:
patent: 5357220 (1994-10-01), Francis
patent: 39 38 760 A1 (1991-05-01), None
patent: 0 685 928 A1 (1995-12-01), None
patent: 97/43828 (1997-11-01), None
Jacobsson Harald
Mokhtari Mehran
Kinkead Arnold
Nixon & Vanderhye P.C.
Telefonaktiebolaget LM Ericsson (publ)
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