JPH05152948A - Phase locked loop oscillation circuit - Google Patents

Abstract

PURPOSE:To attain the miniaturization by impressing a required DC voltage to a high frequency escaping terminal of a smoothing filter corresponding to a frequency switching signal. CONSTITUTION:A phase locked loop circuit 1 receiving a comparison input signal and a frequency changeover control signal outputs a DC voltage signal corresponding to an object frequency. The output is fed via a filter 2 operated stably at a low speed response, a VCO 3 forms a carrier of an object frequency and outputs a carrier modulated in response to the modulation input. On the other hand, a same DC voltage signal as that outputted by the circuit 1 is impressed to a high frequency escape terminal of a capacitor C of the filter 2 via a control circuit 4 in response to the frequency switching control signal. Then the capacitor C is charged in a short time and high response is ensured for the filter 2 at frequency changeover and low speed response and high speed response are ensured by the single filter to miniaturize the configuration of the phase locked loop oscillation circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a phase locked oscillator circuit. Particularly, the present invention relates to an improvement aimed at downsizing a phase-locked oscillator circuit used in a communication device such as a mobile phone.

[0002]

2. Description of the Related Art A phase-locked oscillator circuit in this specification receives a comparison input signal having a reference frequency, a frequency switching control signal for selecting a channel frequency, and a modulation input signal such as a voice signal. , A transmission circuit that modulates a carrier wave of a selected frequency channel with a modulation input signal and outputs the modulated carrier wave.

A conventional phase locked oscillator circuit is shown in FIG. In the figure, reference numeral 6 is inputted with a comparison input signal having a reference frequency and a frequency switching control signal for selecting a channel, and based on these input signals, a carrier having a frequency corresponding to the selected frequency channel. Is a first oscillating circuit that oscillates in phase synchronization. Reference numeral 7 is inputted with the above-mentioned comparison input signal and a modulation input signal such as a voice signal, and oscillates a wave having a frequency of a constant multiple of the frequency of the comparison input signal in a phase-locked manner and modulates this with the above-mentioned modulation input signal It is the second oscillating circuit for outputting. Reference numeral 8 is a mixer for mixing the output of the first oscillation circuit 6 and the output of the second oscillation circuit 7. Reference numeral 9 is a bandpass filter corresponding to the sum frequency of the respective frequencies of the both outputs mixed in the mixer 8. The reason why this bandpass filter is necessary is that during the output of the mixer 8, there is no difference in the frequency of the difference between the output frequency of the first oscillation circuit 6 and the output frequency of the second oscillation circuit 7. This is because the desired frequency components are included and these are excluded.

By the way, the phase-locked oscillator circuit requires high-speed response at the time of frequency switching, but at the time of transmission on the same channel, the high-speed response rather deteriorates the stability of control, and thus has a slight delay. Responsiveness is desirable. In response to these contradictory requirements, the phase-locked oscillator circuit according to the prior art is provided with circuits of different corresponding speeds suitable for the respective requirements. That is, the first oscillating circuit 6 having the high-speed response and the second oscillating circuit 7 having the low-speed response are provided, and the outputs of the respective circuits are mixed and output using the mixer 8. System.

[0005]

As described above, in the phase-locked oscillator circuit according to the prior art, the first oscillator circuit and the second oscillator circuit having different response speeds are separately provided and the respective control circuits are controlled. Since the system is configured,
There is a drawback that the circuit becomes large. In addition, since we are using a mixer, we need a bandpass filter,
The circuit is becoming larger.

An object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a miniaturizable phase-locked oscillator circuit used in a communication device such as a mobile phone.

[0007]

The above object is to input a comparison input signal and a frequency switching control signal, set a target frequency based on this, and compare the target frequency with the output carrier frequency. A phase locked loop circuit that outputs a voltage corresponding to the deviation, a filter that smoothes the output voltage of this phase locked loop circuit, and an oscillation frequency is controlled according to the output voltage of this filter to form a carrier wave. A voltage controlled oscillator circuit that modulates and outputs a modulated input signal, and a voltage generator that generates a voltage corresponding to the frequency switching control signal and applies this voltage to the ground side terminal of the capacitor that constitutes the filter. It is achieved by a phase locked oscillator circuit having.

In the above structure, the carrier wave voltage generated by the carrier wave oscillator constituting the voltage controlled oscillator circuit (3) is negatively fed back to the phase locked loop circuit (1), and the frequency of this carrier wave voltage is set to the above target. It is preferable that a circuit for matching the frequency is provided because the accuracy of the carrier voltage is improved.

[0009]

In the phase locked oscillator circuit according to the present invention, the high-speed response required when switching the frequency of the carrier voltage and the low-speed response (stability) required when transmitting in the same frequency channel respectively correspond. In the single circuit, the potential of a specific point (high frequency escape terminal of the filter 2) is changed to a direct current voltage signal (current voltage representative of the target frequency) output from the phase locked loop circuit 1 described above. This is achieved by controlling the same value as the signal).

Explaining in more detail, in the present invention, the circuit constant of the filter 2 itself is set so as to satisfy the low speed response (stability) required at the time of transmission in the same frequency channel, and the high speed response. When frequency switching is required, the voltage (the same voltage as the current-voltage signal representative of the target frequency) is applied to the harmonic wave escape terminal of the capacitor that constitutes the filter 2, and the potential of this terminal is changed to the target frequency. It is said that the voltage rises to the same voltage as the current-voltage signal that is representative. In other words, this voltage is set to be almost the same as the voltage (the input voltage to the filter 2) output from the phase locked loop circuit 1 at the time of switching the frequency, and therefore the filter 2 at the time of switching the frequency.
The charging time to the capacitor of is extremely short, and therefore high-speed response can be secured.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A phase locked oscillator circuit according to an embodiment of the present invention will be described below with reference to the drawings.

In the figure, reference numeral 1 is input with a comparison input signal having a reference frequency and a frequency switching control signal for selecting a channel frequency, and based on these, a frequency divider for generating a target frequency is selected. .. And
The target frequency generated by the selected frequency divider is compared with the carrier frequency generated by the carrier wave oscillator forming the voltage controlled oscillator circuit 3 described later, and the target frequency generated by the selected frequency divider is compared. Is a phase locked loop circuit that generates a DC voltage signal that represents

2 is an inverse L having a resistor R and a capacitor C.
Shaped filters (eg lag lead filters)
This is to impart desired responsiveness by reducing the harmonics contained in the DC output voltage signal of the phase locked loop circuit 1 described above.

Reference numeral 3 denotes a carrier wave oscillator for generating a carrier wave voltage having the same frequency as the frequency generated by the selected frequency divider based on the DC output voltage signal of the filter 2, and this carrier wave oscillator. A voltage controlled oscillator circuit having a transformer that modulates a carrier wave by a modulation input signal such as voice and outputs the modulated carrier wave.

Reference numeral 4 is a voltage generating means for receiving the frequency switching control signal, generating an analog voltage corresponding to this signal, and applying this voltage to the high frequency escape terminal of the capacitor of the filter 2. The voltage generating means 4 raises the potential of the high frequency escape terminal of the capacitor of the filter 2 to the same potential as the DC voltage signal representing the target frequency when switching the frequency channel.
The voltage generating means 4 comprises, for example, a control circuit 41 for outputting a digital code of a voltage corresponding to the frequency switching control signal and a digital / analog converting means 42 for converting the output of the control circuit 41 into an analog potential. can do.

In the phase locked oscillator circuit according to the present invention, since the frequency switching control signal is not input to the voltage generating means 4 during continuous transmission in the same frequency channel, the output voltage of the voltage generating means 4 is zero in terms of AC. Therefore, the potential of the high frequency escape terminal of the capacitor of the filter 2 becomes the ground potential in terms of alternating current, and the low speed response determined by the circuit constant of the filter 2 is secured.

On the other hand, at the time of frequency switching, the frequency switching control signal is input to the voltage generating means 4, so that the voltage generating means 4 generates a voltage substantially the same as the DC voltage signal representing the target frequency, and the voltage of the filter 2 is changed. It is applied to the high frequency escape terminal of the capacitor to increase the potential of this high frequency escape terminal. As a result, the charging time for the capacitor is shortened and high-speed response is ensured.

[0018]

As described above, the phase locked oscillator circuit according to the present invention is a phase locked loop circuit for generating a DC voltage signal representative of a target frequency generated by a frequency divider selected based on a frequency switching control signal. A filter provided on the output side of this phase locked loop, an oscillator that generates a carrier wave based on the output voltage of this filter, and a voltage controlled oscillator circuit that has a modulator that modulates this carrier wave with a modulation input signal, Based on the frequency switching control signal, generate a DC voltage signal representative of the target frequency and apply this DC voltage signal to the harmonic wave escape terminal of the filter,
It has a voltage generating means for raising the voltage of this terminal when switching frequency channels, and the circuit constants of the above filters are set so as to satisfy the low-speed response required for continuous transmission in the same frequency channel. ,
At the time of frequency switching that requires high-speed response, it is said that the potential of the harmonic escape terminal of the capacitor that constitutes the above filter is increased, so the charging time to the capacitor at the time of frequency channel switching becomes extremely short, Therefore, high-speed response can be secured.

As a result, the phase-locked oscillator circuit according to the present invention provides the means for achieving the high-speed response required for frequency switching and the low-speed response (stability) required for continuous transmission on the same channel. It is not necessary to provide it, and the volume can be reduced to about 40% compared to the conventional technology.

Therefore, the present invention can provide a miniaturizable phase locked oscillator circuit used in a communication device such as a mobile phone.

[Brief description of drawings]

FIG. 1 is a block diagram of a phase locked oscillator circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a phase locked oscillator circuit according to a conventional technique.

[Explanation of symbols]

 1 Phase Locking Circuit 2 Filter 3 Voltage Controlled Oscillation Circuit 4 Control Circuit 5 Digital / Analog Converter 6 First Oscillation Circuit 7 Second Oscillation Circuit 8 Mixer 9 Bandpass Filter

Claims (2)

[Claims] 1. A comparison input signal composed of a reference high-frequency voltage signal and a frequency switching control signal representing a plurality of frequency division coefficients for dividing the comparison input signal are inputted, and based on the frequency switching control signal. And a frequency-voltage converter for generating a target frequency signal composed of a DC voltage signal representative of the target frequency generated by the frequency divider. Based on the synchronizing circuit (1), the filter (2) for smoothing the target frequency signal generated by the phase synchronizing circuit (1), and the target frequency signal smoothed by the filter (2), the frequency division is performed. An oscillator that generates a carrier voltage composed of a high-frequency voltage signal having a specified frequency, and a modulator that modulates the carrier voltage generated by the oscillator with a modulation input signal Pressure control oscillation circuit (3)
When the frequency switching control signal is input, a DC voltage signal that is almost the same as the target frequency signal is generated slightly ahead of the target frequency signal, and harmonics of the filter (2) are released. A phase-locked oscillator circuit, comprising: a voltage generating circuit (4) applied to a working terminal. 2. The phase locked loop circuit (1) negatively feeds back the output signal of the voltage controlled oscillator circuit (3) to match the frequency of the output signal of the voltage controlled oscillator circuit (3) with the target frequency. The phase-locked oscillator circuit according to claim 1, further comprising a circuit.