Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Patent
1991-11-08
1993-08-17
Voeltz, Emanuel T.
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
323222, 363 21, 363 97, 330270, 330290, G05F 156, H02M 3155
Patent
active
052372618
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a voltage step up regulator for producing a frequency control voltage for a frequency synthesizer in a radio transmitter from a low operating voltage.
2. Description of the Related Art
In a traditional frequency synthesizer formed by a phase-locked loop, frequency is usually produced by oscillators controlled by capacitance diodes. Conventional circuits include the Collpits and its various modifications. To save space and costs, the oscillator is operated at a so-called final frequency while the transmitter oscillator is frequency-modulated through a control voltage. It is desirable that this kind of oscillator can be adjusted within a frequency range as wide as possible with one and the same control voltage.
To widen the adjustable frequency range without increasing the control voltage range, the ratio of the change of frequency to the change of the control voltage has to be increased.
The problem is that noise occurring in the control voltage also modulates the carrier wave to a relatively greater degree than previously. This, in turn, results in a reduction in the signal-to-noise ratio of the radio transmission. Noise occurring in the control voltage may be caused by several different sources and it is difficult to filter. With low-frequency noise, the filtration is especially difficult to carry out.
Another way of widening the adjustable frequency range of the frequency synthesizer is to increase the control voltage range. However, portable radio devices have to use accumulators as a source of power, the typical accumulator voltage being about 12 V. Losses caused by various filter and regulator circuits further decrease the applicable dc voltage. However, a control voltage of about 12 V is insufficient for the control of the frequency synthesizer within a wide frequency range.
In prior art solutions, attempts have been made to increase such low operating voltages by circuits realized by conventional switched mode power supplies. A switched mode circuit usually operates at a frequency between 10 to 100 kHz. False signals, i.e. low-frequency noise, occuring in non-linear switched mode circuits are easily propagated in the circuits of the radio device, being summed to the intermediate and low-frequency signals.
Noise also occurs in the frequency control voltage of the frequency synthesizer, which further impairs the signal-to-noise ratio of the system. In an attempt to reduce the noise caused by the switched more circuit, the circuit has been realized by a separate hybrid, it has been positioned in a metallic casing, and the operating frequency of the circuit has been selected suitably with a frequency range between the radio channels such that it has not been taken into account in the specifications of the system.
Accordingly, the prior art switched mode circuits impair the properties of the radio device and take quite a lot a space, which is more and more inconvenient with ever decreasing device sizes.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a voltage step up regulator which avoids the problems of the prior art. This as well as the other objects of the invention are achieved by means of a voltage step up regulator.
The basic idea of the invention is to amplify a high-frequency signal by means of an amplifier operating linearly in class A, to raise the dc level of the amplified signal by a level lock or a similar dc level shifting circuit, and to adjust the control voltage of the regulator to a desired value. The output voltage is preferably adjusted by means of a feedback using as a reference voltage a stabilized lower voltage existing in the frequency synthesizer. The invention avoids the problems of the prior art, because it does not produce harmonic or other low-frequency noise components in the frequency synthesizer or in the adjacent circuits.
As the amplifier is controlled by a sinusoidal signal, a single high-frequency component is formed which is easy to filter out of the output
REFERENCES:
patent: 3944908 (1976-03-01), Oki
patent: 4237425 (1980-12-01), Spiegel
patent: 4336504 (1982-06-01), Seki et al.
Berhane Adolf
Telenokia OY
Voeltz Emanuel T.
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