JPH0673929U - Frequency synthesizer - Google Patents

Abstract

(57) [Summary] [Objective] In the conventional frequency synthesizer, since the voltage supplied to the charge pump is supplied at a low voltage, the control voltage range of the voltage controlled oscillator circuit is narrowed, so that the frequency band is widened. Not suitable. The object of the present invention is to eliminate these drawbacks, to realize a wider frequency band without degrading the performance of the voltage controlled oscillator circuit, and to realize a compact and high-speed frequency synthesizer. [Composition] In the frequency synthesizer, the regulator output voltage adjusted by the regulator from the power supply is applied to the DC-D.
The voltage is boosted by the C converter and supplied as the power source for the charge pump, and the changeover switch connected between the regulator input and the DC-DC converter output is turned on for several milliseconds when the frequency synthesizer is changed over.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a frequency synthesizer used in a radio device.

[0002]

[Prior art]

 A conventional technique is shown in FIG. In this frequency synthesizer, the output of the reference oscillator 1 is input to the frequency divider 2, and the output of the frequency divider 2 is added as the reference input of the phase comparator 3. The phase difference output of the phase comparator 3 is input to the charge pump 4, converted from a digital signal to an analog signal, and input to the voltage controlled oscillator circuit 6 via the low pass filter 5. The output of the voltage controlled oscillator circuit 6 is used as the output 7 and at the same time input to the frequency divider 8. The output of the frequency divider 8 is input to the comparison input of the phase comparator 3. The voltage of the power source 9 is adjusted by the regulator 10 and supplied as the power source of the charge pump 4. For example, in the case of an in-vehicle wireless device, the power supply voltage of 13.6V is adjusted to 9V by the 9V regulator, and in the case of a portable wireless device, the power supply voltage of 7.5V is adjusted to 5V by the 5V regulator and supplied to the charge pump 4.

[0003]

[Problems to be solved by the device]

 Since the low voltage regulated by the regulator is supplied to the charge pump in the above-mentioned conventional technique, the control voltage range of the voltage controlled oscillator circuit is narrowed and is not suitable for widening the frequency band. However, there is a drawback that the performance such as S / N and C / N is deteriorated, and the low voltage adjusted by the regulator is boosted by the DC-DC converter and the charge is increased. By supplying it to the pump, the control voltage range of the voltage controlled oscillator can be expanded and a wider band can be realized. However, since a large amount of current is required when switching the frequency synthesizer (high-speed switching), the current capacity is large. It is necessary to use a different DC-DC converter. However, since the DC-DC converter with large current capacity has a large outer shape, it has a drawback that it is not suitable for downsizing of equipment. The purpose of the present invention is to eliminate these drawbacks and to realize a wide-band, compact, high-speed frequency synthesizer without degrading the performance of the voltage-controlled oscillator circuit.

[0004]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention boosts a voltage regulated by a regulator from a power source by a DC-DC converter and supplies it as a power source for a charge pump. When the frequency synthesizer is switched, the regulator and the DC are fed for several milliseconds. -A large amount of current can be supplied by turning on the changeover switch connected in parallel with the DC converter.

[0005]

[Action]

 As a result, the voltage supplied to the charge pump can be supplied as a boosted voltage, so that the control voltage range of the voltage-controlled oscillator can be widened, and the wider frequency band does not increase the modulation sensitivity of the voltage-controlled oscillator. Can be realized (without degrading the performance of the voltage controlled oscillator circuit). Also, by turning on the selector switch and supplying a large amount of current, it is possible to speed up the frequency synthesizer and to use a DC-DC converter with a small current capacity, thus making the device compact. it can.

[0006]

【Example】

 An embodiment of the present invention will be described below with reference to FIG. In this frequency synthesizer, the output of the reference oscillator 1 is input to the frequency divider 2 and the output of the frequency divider 2 is added as the reference input of the phase comparator 3. The phase difference output of the phase comparator 3 is input to the charge pump 4, converted from a digital signal to an analog signal, and input to the voltage controlled oscillator circuit 6 via the low pass filter 5. The output of the voltage controlled oscillator circuit 6 is used as the output 7 and at the same time input to the frequency divider 8. The output of the frequency divider 8 is input to the comparison input of the phase comparator 3. The voltage of the power source 9 is adjusted by the regulator 10, and the output voltage of the regulator 10 is boosted by the small DC-DC converter 11 having a small current capacity and supplied as the power source of the charge pump 4.

As a result, the control voltage range of the voltage controlled oscillator circuit 6 is widened, and a wide frequency band can be realized without degrading the performance of the voltage controlled oscillator circuit 6. At the time of switching the frequency synthesizer, the switching switch 12 connected in parallel with the regulator 10 and the DC-DC converter 11 is turned on for several milliseconds by the switching signal 13, and a large amount of current is supplied to the charge pump 4 to supply the frequency. It is possible to speed up the synthesizer.

[0008]

[Effect of device]

 According to the present invention, it is possible to widen the frequency band without degrading the performance of the voltage controlled oscillator circuit, and it is possible to use a DC-DC converter with a small current capacity. A frequency synthesizer can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of the present invention.

FIG. 2 is a block diagram showing a conventional example of the present invention.

FIG. 3 is a block diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 Reference Oscillator 2 Divider 3 Phase Comparator 4 Charge Pump 5 Low Pass Filter 6 Voltage Controlled Oscillator 7 Output 8 Divider 9 Power Supply 10 Regulator 11 DC-DC Converter 12 Changeover Switch 13 Changeover Signal

Claims (1)

[Scope of utility model registration request] 1. An output of a voltage controlled oscillator circuit is divided by a divider controlled by a division ratio designating signal, the divided signal and a reference frequency are phase-compared by a phase comparator, and the comparison result is The output of a charge pump that converts a digital signal into an analog signal is subjected to cycle control of a voltage controlled oscillation circuit via a loop filter, and the charge pump is supplied with a voltage boosted as a power supply voltage via a DC-DC converter. The frequency synthesizer is characterized in that a changeover switch is provided between the regulator input and the DC-DC converter output so as to supply a large current from the power supply to the charge pump for a predetermined period.