JPH09252219A - Voltage controlled oscillator and frequency synthesizer using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frequency synthesizer using a voltage controlled oscillator able to make phase synchronization even when a frequency difference between a present frequency and a frequency to be set succeedingly is large when changing the frequency channel. SOLUTION: A 2nd diode 11 is connected between an existing resonator 2 of a voltage controlled oscillator 4 of the frequency synthesize, a 1st diode 3 via a capacitor 10 and ground and a frequency channel adjustment circuit is connected between the capacitor 10 and the 2nd diode 11 to apply a DC amplifier signal after a prescribed frequency channel setting. Thus, the 2nd diode 11 is controlled by the frequency channel adjustment circuit to set a resonance frequency at a high speed to correct a frequency fluctuation due to the temperature change of the 1st diode 3 controlled by a phase locked loop filter 8 and the deviation between a desired frequency and the resonance frequency set by the 2nd diode 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillator mainly applied to a microwave band communication device and a frequency synthesizer using the same.

[0002]

2. Description of the Related Art Conventionally, a frequency synthesizer of this type has, for example, a configuration as shown in FIG. In this frequency synthesizer, a resonator 2 is connected between an output and an input of a high frequency amplifier 1 for amplifying a high frequency signal via a pair of capacitors 5 and 6 for removing direct current, and the resonator 2 has a varactor diode 3 grounded. The phase-locked loop filter 8 is connected between the resonator 2 and the varactor diode 3 and the output side of the high-frequency amplifier 1 with respect to the voltage-controlled oscillator 16 which is connected. Specifically, the phase-locked loop filter 8 having one end connected to the output terminal 9 and the direct-current removing capacitor 7 are connected to the output terminal 9, and the other end of the phase-locked loop filter 8 is the resonator 2 and the varactor diode 3.
Meanwhile, the other end of the DC removing capacitor 7 is connected to the DC removing capacitor 5.

In this frequency synthesizer, the amplified output of the high frequency signal amplified by the high frequency amplifier 1 in the voltage controlled oscillator 16 is passed through the direct current removing capacitor 5 to the resonator 2
Is input to the output of the resonator 2 and the DC removing capacitor 6
Is input to the amplifier 1 via. The oscillation output of the voltage controlled oscillator 16 is connected to the output terminal 9 from the connection point of the DC removing capacitor 5 and the resonator 2 via the DC removing capacitor 7, and is also input to the phase-locked loop filter 8 for phase locking. The output of the loop filter 8 is fed back to the connection point of the resonator 2 and the varactor diode 3.

FIG. 4 shows the oscillation frequency f (GH) with respect to the phase control voltage Vφ (V) in this frequency synthesizer.
It shows the relationship of z). Here, the frequency f ₁
In the required band ΔB corresponding to the range from to f _n, the oscillation frequency increases in proportion to the change in the phase control voltage on the frequency f ₁ side where the voltage is low, at a substantially constant slope, and becomes a high frequency f _n . It can be seen that the attenuation gradually increases with a low gradient as it approaches.

Incidentally, as a known technique related to the conventional frequency synthesizer described here, for example, Japanese Patent Laid-Open No.
The voltage control oscillator etc. which were disclosed by the 3-248204 publication are mentioned.

[0006]

In the case of the frequency synthesizer described above, since the frequency is variable by the single varactor diode in the voltage controlled oscillator connected to the phase locked loop filter, it is set next when the frequency channel is changed. When the frequency difference with the frequency channel is large, there is a problem that it takes a long time for phase synchronization. Therefore, improvements are required in both the configuration of the voltage controlled oscillator itself and the configurations of its peripheral devices.

The present invention has been made to solve such a problem, and its technical problem is to achieve a phase in a short time even when a frequency difference with a frequency channel set next when the frequency channel is changed is large. It is to provide a voltage controlled oscillator that can be synchronized and a frequency synthesizer using the same.

[0008]

According to the present invention, a resonator is connected between an output and an input of a high frequency amplifier for amplifying a high frequency signal through a pair of DC removing capacitors, and the resonator is grounded. In a voltage controlled oscillator in which a phase-locked loop filter is connected between the resonator and the first varactor diode and between the resonator and the first varactor diode and the output side of the high frequency amplifier. A voltage controlled oscillator is obtained in which a second varactor diode is connected between the capacitor and the first varactor diode and the ground side via a capacitor.

Further, according to the present invention, in the frequency synthesizer including the voltage controlled oscillator and the phase locked loop filter, the DC amplified signal set in the predetermined frequency channel is applied between the capacitor and the second varactor diode. There is obtained a frequency synthesizer to which a frequency channel adjusting circuit for connecting is connected.

Further, according to the present invention, in the above frequency synthesizer, the frequency channel adjustment circuit is divided into a plurality of sections in a required band according to the control data and a memory circuit storing control data according to the frequency setting data. A frequency channel setting logic circuit that outputs a frequency channel setting digital signal that represents the channel setting with one of the oscillation frequencies corresponding to the phase control voltage as a predetermined frequency channel, and the frequency channel setting digital signal is converted to a frequency channel setting analog signal. A frequency synthesizer comprising a digital-to-analog converter and a DC amplifier for amplifying a frequency channel setting analog signal to form a DC amplified signal is obtained.

[0011]

In the frequency synthesizer of the present invention, both the structure of the existing voltage-controlled oscillator and the structure of its peripheral equipment are improved, and the voltage-controlled oscillator includes the existing resonator and the first varactor diode and the ground side. A second varactor diode is separately connected to and via a capacitor, and as a peripheral device, a frequency channel adjustment for applying a DC amplified signal that has undergone a predetermined frequency channel setting between this capacitor and the second varactor diode. The circuit is connected.
In such a configuration, since the second varactor diode is controlled by the frequency channel adjustment circuit and the resonance frequency can be set at high speed, the first varactor diode controlled by the phase-locked loop filter causes the frequency fluctuation due to temperature change or the like and the second varactor diode to be controlled. The deviation between the resonance frequency set by the varactor diode and the desired frequency is corrected.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a voltage controlled oscillator of the present invention and a frequency synthesizer using the same will be described in detail with reference to the drawings.

FIG. 1 is a circuit block diagram showing the basic configuration of a frequency synthesizer according to an embodiment of the present invention.

Also in this frequency synthesizer, a resonator 2 is connected between an output and an input of a high frequency amplifier 1 for amplifying a high frequency signal through a pair of direct current removing capacitors 5 and 6,
The resonator 2 is provided with a voltage controlled oscillator 4 to which a grounded first varactor diode 3 is connected, and between the resonator 2 and the first varactor diode 3 in the voltage controlled oscillator 4 and the high frequency amplifier 1. A phase lock loop filter 8 is connected to the output side. However,
In this voltage controlled oscillator 4, a capacitor 10 is provided between the resonator 2 and the first varactor diode 2 and on the ground side.
The second varactor diode 11 is connected via.

Also here, in the frequency synthesizer, the phase-locked loop filter 8 whose one end is connected to the output terminal 9 and another DC removing capacitor 7 are connected to the resonator 2 and the other end of the phase-locked loop filter 8. Between the first varactor diodes 3, the other end of the DC removing capacitor 7 is connected to the DC removing capacitor 5.

Further, in the case of this frequency synthesizer, a frequency channel adjusting circuit for applying a DC amplified signal set to a predetermined frequency channel is connected between the capacitor 10 and the second varactor diode 11. This frequency channel adjusting circuit stores either one of the memory circuit 15 storing control data according to the frequency setting data and the oscillation frequency corresponding to the plurality of divided phase control voltages in the required band ΔB according to the control data. A frequency channel setting logic circuit 14 for outputting a frequency channel setting digital signal representing a channel setting for a predetermined frequency channel, and a digital / analog (D / A) conversion for converting the frequency channel setting digital signal into a frequency channel analog setting signal. And a DC amplifier 12 that amplifies the frequency channel setting analog signal to form a DC amplified signal.

In this frequency synthesizer, the resonator 2,
It oscillates at a resonance frequency determined by the first varactor diode 3, the capacitor 10, and the second varactor diode 11, and a part of the oscillation output is the phase-locked loop filter 8
Is input to the first varactor diode 3 by the error voltage of the internal phase comparator, and the phase is locked.

In general, the change of the resonance frequency with respect to the change of the control voltage of the varactor diodes 3 and 11 is not linear in a wide band. Therefore, the frequency setting data is stored in the memory circuit 15 in advance so that the frequency setting data and the resonance frequency are substantially linear. The control data to be stored is stored as a conversion table.

Further, as the second varactor diode 11, one having a variable required band ΔB width is used, and the first varactor diode 3 is set by the second varactor diode 11 due to frequency fluctuation due to temperature change and the like. A variable frequency band that can correct the deviation between the resonance frequency and the desired frequency is used. Alternatively, since the variable capacitance can be set in combination with the capacitance value of the capacitor 10, the first varactor diode 3 may be the same as the second balactor diode 11.

Next, the basic operation of this frequency synthesizer will be described. First, the frequency channel setting logic circuit 14
Then, when the frequency channel is set, the memory circuit 1
5, the control data is read from the conversion table 5 and a frequency channel setting digital signal representing the frequency channel is output according to the control data. The digital / analog converter 13 converts the frequency channel setting digital signal into an analog voltage and outputs the frequency channel setting analog signal. The DC amplifier 12 applies a DC amplified signal obtained by amplifying the frequency channel setting analog signal to a predetermined voltage value to the second varactor diode 11.

Here, since the junction capacitance of the second varactor diode 11 is set sufficiently larger than the junction capacitance of the first varactor diode 3 and the combined capacitance value of the capacitors 10, the resonance frequency is set to almost the frequency channel. It moves at high speed to the frequency set by the logic circuit 14 for use. or,
A part of the oscillation output is input to the phase-locked loop filter 8, and the phase-locked loop filter 8 outputs the first phase control voltage according to the deviation between the set frequency and the desired frequency.
And phase lock by applying to the varactor diode 3 of.

FIG. 2 shows the oscillation frequency f (GH) with respect to the phase control voltage Vφ (v) in this frequency synthesizer.
It shows the relationship of z). Here, the frequency channel setting logic circuit 14 determines _{one of} the oscillation frequencies corresponding to a plurality of divided phase control voltages within the frequency range f _{1 to} f _n in the required band ΔB according to the control data. Since it is set as a frequency channel,
Its characteristics are from low voltage frequency f ₁ to high voltage frequency f _n
It can be seen that there is a uniform slope and proportional increase at each frequency up to.

The same effect can be obtained even if the capacitor 10 in the voltage controlled oscillator 4 of the above-mentioned embodiment is a coupling capacitance using a stripline coupling line.

[0024]

As described above, according to the frequency synthesizer of the present invention, the voltage-controlled oscillator and its peripheral devices are improved, and the voltage-controlled oscillator has a ground between the existing resonator and the first varactor diode. A second varactor diode is separately connected to the side through a capacitor, and a frequency channel adjustment circuit for applying a DC amplified signal having a predetermined frequency channel setting is connected between the capacitor and the second varactor diode. , The second varactor diode is controlled by the frequency channel adjustment circuit to set the resonance frequency at high speed, and the first varactor diode controlled by the phase-locked loop filter is Since it is configured to correct the deviation between the set resonance frequency and the desired frequency, It becomes possible to phase lock to a short time when the frequency difference between the frequency channel is then set when the channel change is great.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a basic configuration of a frequency synthesizer according to an embodiment of the present invention.

FIG. 2 shows a relationship between an oscillation frequency and a phase control voltage in the frequency synthesizer shown in FIG.

FIG. 3 is a circuit block diagram showing a basic configuration of a conventional frequency synthesizer.

FIG. 4 shows a relationship between an oscillation frequency and a phase control voltage in the frequency synthesizer shown in FIG.

[Explanation of symbols]

 1 High Frequency Amplifier 2 Resonator 3,11 Varactor Diode 4,16 Voltage Controlled Oscillator 5,6,7 DC Removing Capacitor 8 Phase Lock Loop Filter 9 Output Terminal 10 Capacitor 12 DC Amplifier 13 Digital / Analog (D / A) Converter 14 frequency channel setting logic circuit 15 memory circuit

Claims (3)

[Claims] 1. A resonator is connected between an output and an input of a high-frequency amplifier for amplifying a high-frequency signal via a pair of DC removing capacitors, and the resonator is connected to a grounded first varactor diode. And a phase-locked loop filter is connected between the resonator and the first varactor diode and between the output side of the high-frequency amplifier. A voltage-controlled oscillator characterized in that a second varactor diode is connected to the space and the ground side via a capacitor. 2. A frequency synthesizer including the voltage controlled oscillator according to claim 1 and the phase locked loop filter, wherein a DC amplified signal set in a predetermined frequency channel is provided between the capacitor and the second varactor diode. A frequency synthesizer characterized in that a frequency channel adjusting circuit for applying is connected. 3. The frequency synthesizer according to claim 2, wherein the frequency channel adjusting circuit is divided into a plurality of sections in a required band according to the control data and a memory circuit storing control data according to the frequency setting data. A frequency channel setting logic circuit for outputting a frequency channel setting digital signal representing channel setting with any one of oscillation frequencies corresponding to a phase control voltage as the predetermined frequency channel, and the frequency channel setting digital signal for frequency channel setting analog signal. 2. A frequency synthesizer comprising: a digital / analog converter for converting the frequency channel setting analog signal and a DC amplifier for amplifying the frequency channel setting analog signal to form the DC amplified signal.