JPH06237121A - Voltage controlled oscillator and its oscillating frequency adjustment method - Google Patents

Abstract

PURPOSE:To provide a voltage controlled oscillator capable of adjusting an oscillating frequency and its oscillating frequency adjustment method without deteriorating the Q of a resonance element, that is, without deteriorating the C/N characteristic of the voltage controlled oscillator. CONSTITUTION:Between a control voltage application terminal Vc and a varactor diode VD, a control voltage adjustment circuit VR is connected, which is made up of a 1st resistor R4 connected between the control voltage application terminal Vc and the varactor diode VD and up of a 2nd resistor R5 connected between ground and the 1st resistor R4 at a side of the varactor diode VD respectively, a control voltage is divided by a resistance ratio of both resistors R4, R5 to adjust the oscillating frequency to an adjustment object frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes a resonance circuit in an oscillation stage, the resonance circuit including a variable capacitance element to which a control voltage is applied from a control voltage application terminal, and its oscillation frequency adjustment. Regarding the method.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram of a conventional voltage controlled oscillator. The voltage-controlled oscillator shown in this figure prevents an oscillation stage OS whose oscillation frequency is changed by a control voltage applied to a control voltage application terminal Vc and an oscillation frequency of the oscillation stage OS from being changed by a load change. Output matching stage OM for matching between the buffer stage BF and the next stage circuit connected to the output terminal OUT and suppressing harmonics
And are deployed and configured. In this figure, the internal circuit is shown only for the oscillation stage OS, and the oscillation stage O
The coupling relation in the circuit to the buffer stage BF with respect to the concrete internal circuit of S is not shown because it is not particularly necessary. Further, such a circuit is arranged with necessary parts on a substrate (not shown).

The oscillation stage OS is of the Colpitts type, and its internal circuit configuration will be described. A high frequency bypass capacitor C is provided between the control voltage application terminal Vc and the ground portion.
₁ is provided. Similarly, between the control voltage application terminal Vc and the ground portion, an impedance element L ₁ formed on the substrate by patterning so as to have a function of a choke coil and a response to the control voltage from the control voltage application terminal Vc. A variable capacitance diode VD whose capacitance changes is connected in series.

One end of _two coupling capacitors C ₂ and C ₃ connected in series with each other is connected to a common connection portion of the impedance element L ₁ and the variable capacitance diode VD. Both coupling capacitors C ₂ , C ₃
Between the common connection portion and the ground portion, the resonant elements L ₂ and C _{4 of the} L component and the C component, respectively, which are formed into strip lines on the substrate, are connected in parallel with each other.

The bases of the oscillating transistors Tr are connected to the other ends of the coupling capacitors C ₂ and C ₃ , and the bases 2 connected in series between the power source + B and the ground portion are connected to each other. The common connection of the _two bias resistors R ₁ and R ₂ is connected.

A bias resistor R ₃ and a capacitor C ₅ as Colpitts capacitance are connected in parallel between the emitter of the oscillating transistor Tr and the grounded portion. A capacitor C ₆ as Colpitts capacitance is also connected between the collector of the oscillating transistor Tr and the ground portion.

In the oscillation stage OS, the impedance element L ₁ , the variable capacitance diode VD, 2
A stripline type resonance circuit RC is constituted by _two coupling capacitors C ₂ and C ₃ and two resonance elements L ₂ and C ₄ .

In the above voltage controlled oscillator, the capacitance of the variable capacitance diode VD is changed by the control voltage applied from the control voltage application terminal Vc in the oscillation stage OS, which changes the resonance frequency of the resonance circuit RC. As a result, the oscillation frequency of the oscillation stage OS changes, and the oscillation frequency output is output from the output terminal OUT to the next-stage circuit side via the buffer stage BF and the output matching stage OM.

By the way, in such a conventional voltage controlled oscillator, the stripline electrodes of the resonance elements L ₂ and C ₄ formed by stripline formation on the substrate are removed, or the resonance elements L ₂ and C ₄ are removed. Put solder on the stripline electrode of C ₄ and set L of the resonant element itself.
The resonance frequency of the resonance circuit is changed by changing the component or the C component, and the oscillation frequency is adjusted accordingly.

[0010]

However, in the conventional voltage controlled oscillator, as described above, the resonant element L ₂ ,
Since the method of changing the resonance frequency by physically removing C ₄ or by soldering or the like to adjust the L component or the C component of the resonance element itself, the Q value of the resonance elements L ₂ and C ₄ is deteriorated. That is, the Q value of the voltage controlled oscillator itself is deteriorated, and the C / N characteristics that influence the performance of the voltage controlled oscillator are deteriorated.

Therefore, according to the present invention, the Q value of the resonant element is not deteriorated, that is, the C /
An object of the present invention is to provide a voltage-controlled oscillator that can adjust the oscillation frequency without degrading the N characteristic and a method for adjusting the oscillation frequency thereof.

[0012]

In a voltage controlled oscillator according to a first aspect of the present invention, a control voltage adjusting circuit is provided between a control voltage applying terminal and a variable capacitance element, and the control voltage adjusting circuit comprises: It is characterized in that the control voltage applied to the variable capacitance element can be adjusted according to the adjustment target value of the oscillation frequency.

In the voltage controlled oscillator according to claim 2 of the present invention, the control voltage adjustment circuit includes a resistance element connected between the control voltage application terminal and the capacitance variable element, and the resistance element. At least a resistance element connected between the variable capacitance element side and the ground portion is included, and the control voltage can be divided by the resistance ratio of the resistance elements.

In the oscillation frequency adjusting method of the voltage controlled oscillator according to the third aspect of the present invention, the oscillation frequency is targeted by adjusting the control voltage input from the control voltage applying terminal and applying it to the variable capacitance element. It is characterized by adjusting the value.

[0015]

In the voltage controlled oscillator according to the first aspect of the present invention, even if the control voltage applied to the control voltage applying terminal is constant, if the control voltage is adjusted by the control voltage adjusting circuit, the capacitance variable element is obtained. Is applied with the adjusted control voltage, and as a result, the oscillation frequency is adjusted.

In the voltage controlled oscillator according to the second aspect of the present invention, the control voltage applied to the variable capacitance element can be adjusted by adjusting the resistance ratio of the both resistance elements.

In the oscillation frequency adjusting method for the voltage controlled oscillator according to the third aspect of the present invention, the oscillation frequency is targeted by adjusting the control voltage input from the control voltage applying terminal and applying it to the variable capacitance element. The value can be adjusted.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a circuit diagram of a voltage-controlled oscillator according to an embodiment of the present invention. The voltage-controlled oscillator of FIG. 2 according to the conventional example is similar to the oscillation stage except for a main portion, and a buffer is used. Since the stage BF and the output matching stage OM are exactly the same, only the oscillation stage OS is shown, but as the voltage controlled oscillator, this embodiment is similar to the conventional example in the oscillation stage OS.
Not only is it provided with a buffer stage BF and an output matching stage OM. Further, the same or corresponding portions as those of FIG. 2 of the conventional example are denoted by the same reference numerals, and detailed description of the portions having the same reference numerals is omitted.

In the voltage controlled oscillator according to this embodiment, the control voltage adjusting circuit VR is provided between the control voltage applying terminal Vc and the capacitance variable diode VD. The control voltage adjusting circuit VR includes a first resistor R ₄ connected between a control voltage applying terminal Vc and a capacitance variable diode VD, and a capacitance variable diode VD side of the first resistor R ₄ and a ground portion. And a second resistor R ₅ connected to the two resistors R ₄ and R ₅
The control voltage can be divided by the resistance ratio. Then, both resistors R ₄ and R ₅ can be laser-trimmed as printing resistors printed on a substrate, and the control voltage applied to the variable capacitance diode VD is adjusted by this trimming to adjust the oscillation frequency. Can be adjusted to the target value.

Specifically, in this voltage controlled oscillator, the control voltage applied to the control voltage application terminal Vc is, for example, 2.0 V, and 1.9 V is applied to the variable capacitance diode VD by the control voltage adjusting circuit VR. It is assumed that the voltage-controlled oscillator is oscillating at an oscillation frequency of 810 MHz at this time. Then, when the adjustment target value of the oscillation frequency is 800 MHz, the resistors R ₄ and R ₅ are laser-trimmed to adjust the resistance ratio of both resistors to lower the control voltage applied to the variable capacitance diode. Then, the oscillation frequency is adjusted to the adjustment target value of 800 MHz.

Although both of the resistors R ₄ and R ₅ are the printing resistors in the embodiment, the resistors are not limited to the printing resistors as long as they can change the resistance value instead of the printing resistors. Further, it is needless to say that it is not necessary to use a normal resistance, but a resistance element that can be replaced therewith may be provided. Further, in the present invention, since a resistor is used, it is preferable to use a resistor having a high resistance so that the current consumption can be suppressed if the current consumption there becomes a problem. Although the variable capacitance diode VD is used in the present invention, the variable capacitance diode VD is not limited to this, and it is essential only that the capacitance be variable according to the control voltage. Further, although the description has been given by using the stripline type as the resonant element, the resonant element is not limited to this and may be a resonant element constituted by a dielectric resonator or LC.

[0023]

As described above, according to the first aspect of the present invention, the control voltage is adjusted by the control voltage adjusting circuit to adjust the control voltage applied to the variable capacitance element so that the oscillation frequency can be adjusted. As a result, it is no longer necessary to grind the resonant element on the substrate or adjust the oscillation frequency by soldering as in the past, and as a result, the Q value is prevented from deteriorating due to the adjustment of the oscillation frequency. As a controlled oscillator, the C / N characteristic is not impaired.

According to the second aspect of the present invention, the control voltage applied to the variable capacitance element can be adjusted by adjusting the resistance ratio of the both resistance elements. Therefore, the oscillation frequency can be easily adjusted. You can

According to a third aspect of the present invention, the control voltage input from the control voltage application terminal is adjusted and applied to the variable capacitance element to adjust the oscillation frequency to the target value. The oscillation frequency can be easily adjusted to the target value without degrading the value.

[Brief description of drawings]

FIG. 1 is a circuit diagram of essential parts of a voltage controlled oscillator according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional voltage-controlled oscillator.

[Explanation of symbols]

OS Oscillation stage VD Variable capacitance diode L ₂ , C ₄ Resonant element VR Control voltage adjustment circuit

Claims (3)

[Claims] 1. A voltage-controlled oscillator including a resonance circuit in an oscillation stage, the resonance circuit including a capacitance variable element to which a control voltage is applied from a control voltage application terminal, wherein the control voltage application terminal and the capacitance variable element are provided. A control voltage adjusting circuit is provided between the control voltage adjusting circuit and the control voltage adjusting circuit, and the control voltage adjusting circuit has a configuration capable of adjusting the control voltage applied to the variable capacitance element according to an adjustment target value of the oscillation frequency. Voltage controlled oscillator. 2. The control voltage adjusting circuit includes a resistance element connected between the control voltage application terminal and the capacitance variable element, and a resistance element connected between the capacitance variable element side of the resistance element and a ground portion. 2. The voltage-controlled oscillator according to claim 1, further comprising at least a resistance element that is controlled, and the control voltage can be divided by a resistance ratio of the resistance elements. 3. A method for adjusting an oscillation frequency of a voltage controlled oscillator, comprising: a resonance circuit in an oscillation stage, wherein the resonance circuit includes a variable capacitance element to which a control voltage is applied from a control voltage application terminal. An oscillation frequency adjusting method for a voltage controlled oscillator, wherein an oscillation frequency is adjusted to a target value by adjusting an input control voltage and applying it to the capacitance variable element.