JPH07297636A - Voltage control oscillator - Google Patents

Abstract

PURPOSE:To provide a voltage control oscillator which can easily suppress the variance of sensitivity of the control voltage and also the variance of sensitivity of modulation without adding any circuit to control the variance of modulation, for example. CONSTITUTION:A voltage control oscillator consists of a resonance circuit part X which includes a variable capacity diode Cv and a microstrip line serving as an inductance generating conductor which are connected together via a capacitor C3, and a negative resistance circuit part Y which includes an active element Q1. The resonance frequency of the part X is varied by varying the voltage supplied to one of both ends of the diode Cv. Meanwhile a variable capacity part C30 is connected to the capacitor C3 in parallel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention controls the oscillation frequency by controlling the applied voltage of a variable capacitance diode, and
The present invention relates to a voltage controlled oscillator having a voice FM modulation function.

[0002]

2. Description of the Related Art A conventional voltage controlled oscillator (VC) for transmission.
O) mainly includes a resonance circuit section, a negative resistance circuit section, an amplification circuit section, and a modulation signal superposition circuit section. FIG. 4 is a circuit diagram showing the resonance circuit section and the modulation signal superposition circuit section.

The resonance circuit section X is composed of microstrip lines MSL ₁ and MSL ₂ , a variable capacitance diode Cv, capacitors C _{1 to} C ₅ and resistors R ₁ and R ₂ . The capacitor C ₅ is a coupling capacitance for coupling the negative resistance circuit section and the resonance circuit section X.

The resonance circuit section X constitutes an LC resonance circuit with the inductance component of the microstrip line MSL ₁ and the combined capacitance of the variable capacitance diode Cv and the capacitors C _{2 to} C ₄ constituting the resonance circuit.

For example, when a predetermined voltage (hereinafter referred to as control voltage Vt) is applied from the control terminal Vt, the voltage across the variable capacitance diode Cv changes. As a result, the combined capacitance of the resonance circuit changes and the resonance frequency becomes a predetermined value. The signal of the predetermined frequency is supplied to the negative resistance circuit section and the amplification section via the capacitor C ₅ , and is output at the predetermined oscillation frequency. This oscillation frequency increases as the control voltage Vt increases, as shown in FIG. 5, for example.

In such a voltage-controlled oscillator, although it usually changes with a constant slope, if the capacitances of the capacitors constituting the resonant circuit section, especially the capacitors C _{2 to} C ₄ , are varied, the control voltage and the oscillation frequency are changed. The slope of the relationship with and varies depending on the product.

Particularly, in the VCO for transmission, a modulation signal superposition circuit section W for superimposing a modulation signal on the resonance frequency is added to a part of the resonance circuit section X, and the frequency of the modulation signal superposition circuit section W is increased. When a frequency-changing signal such as an audio signal is applied from the modulation input terminal Mod, the resistances R ₁ and R
The voltage is divided into _two, and the voltage at the anode terminal of the variable capacitance diode Cv changes based on this voltage division, and modulated oscillation output is performed.

The relationship between the control voltage Vt and the oscillation frequency and the relationship between the frequency modulation input and its output are as shown in FIG. That is, the amplitude of the frequency modulation output depends on the frequency change width per unit control voltage (hereinafter, referred to as control voltage sensitivity), and the characteristics of the control voltage and the oscillation frequency are directly reflected in the modulation sensitivity.

[0009]

Therefore, the modulation sensitivity is
Although it is preferable if the control voltage and the oscillation frequency change with a constant slope, for example, the line A in FIG. 6, the control voltage and the oscillation frequency have a constant slope (control voltage sensitivity) variation, for example, FIG. When it becomes like the line B, the frequency sensitivity varies. In this way, when the variation of the modulation feeling due to the variation of the control voltage sensitivity is large, for example, the sound volume becomes loud.

Therefore, in the transmission circuit including the VCO, a circuit for adjusting the modulation sensitivity is added. For this reason, the number of design circuit constants increases, the number of adjustment processes increases, and as a result, the manufacturing cost increases.

The present invention has been devised in view of the above-mentioned problems, and an object thereof is to add a voltage for easily suppressing variation in modulation impression without adding a circuit for adjusting modulation sensitivity. It is to provide a controlled oscillator.

[0012]

The present invention comprises a resonant circuit section including a variable capacitance diode and an inductance generating conductor connected to each other via a capacitor, and a negative resistance circuit section having an active element. A voltage-controlled oscillator in which a resonance frequency of a resonance circuit unit is changed by changing a voltage supplied to one end of a capacitance diode, wherein the capacitor is a voltage-controlled oscillator in which a variable capacitance unit is connected in parallel. .

[0013]

According to the present invention, the variable capacitance section is arranged in parallel with the capacitor connecting the variable capacitance diode and the resonance means.

Therefore, by adjusting the capacitance of the variable capacitance section, it is possible to suppress variations in control voltage sensitivity.

For example, even when the modulation signal is supplied to one end of the variable capacitance diode, variations in the control voltage sensitivity are suppressed, so that the modulation sensitivity can be stabilized.

Therefore, as the voltage controlled oscillator, it is possible to output a high quality oscillation signal with a very small variation in the control voltage, and the modulation sensitivity is stable without the need for adding a complicated adjusting circuit in the transmitting circuit. In addition, high quality voice can be transmitted.

As a result, the entire apparatus using the voltage controlled oscillator can be downsized, and the design does not become complicated.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A voltage controlled oscillator according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a voltage controlled oscillator (VC) of the present invention.
It is a figure which shows the voltage control oscillation circuit used for O). In the figure, X is a resonance circuit section including microstrip lines MSL ₁ and MSL ₂ which are inductance generating parts, a variable capacitance diode Cv, capacitors C _{1 to} C ₅ and voltage dividing resistors R ₁ and R ₂ , and Y is a transistor. A negative resistance circuit unit composed of Q ₁ , resistors R _{5 to} R ₇ , and capacitors C _{6 to} C ₇ , and Z is a transistor Q ₂ , a microstrip line MSL ₃ , resistors R _{3 to} R ₄ , and capacitors C ₈ to C.
It is an amplifier circuit section consisting of ₁₂ .

In the resonant circuit section X of the VCO described above, the control terminal Vt has a microstrip line MSL ₂
Is connected to the cathode terminal of the variable capacitance diode Cv. A frequency modulation input terminal Mod to which a modulation signal is input is connected to the voltage dividing resistors R ₁ and R ₂ .

The anode terminal of the variable capacitance diode Cv is simultaneously connected to the connection point of the resistors R ₁ and R ₂ which are voltage dividing circuits, and the bypass capacitor C ₂
Are connected. The other end of the voltage dividing resistor R ₂ is also connected to the ground.

The microstrip line MSL ₁ which is the center of the resonance means and the variable capacitance diode Cv are connected via a capacitor C ₃ , and this capacitor C ₃ is connected.
_A variable capacitance section C ₃₀ is connected to ₃ .

FIG. 2 is an equivalent circuit diagram of the resonance circuit section X,
The resonance frequency is determined by the inductance component of the microstrip line MSL ₁ and the combined capacitance of the capacitors C ₃ , C ₄ , Cv connected in parallel with the inductance component. In particular, variations in the capacitor C ₃ , which constitutes the resonant circuit section X, cause variations in the control voltage, which are reflected in changes in the modulation sensitivity. Therefore, in the present invention, to adjust the variation of the capacitor C _3, so that it can adjust the variation of the control voltage, are added in parallel to the variable capacitance section C ₃₀ to the capacitor C _3.

That is, when the slope of the change in the oscillation frequency due to the control voltage is larger than the predetermined slope, the variable capacitor C ₃₀
By decreasing the capacitance of the, and when the slope of the change in the oscillation frequency due to the control voltage is smaller than the predetermined slope,
By increasing the capacitance of the variable capacitance section C ₃₀ , the slope of the change in the oscillation frequency due to the control voltage can be set to a predetermined slope, and the variation can be adjusted by the variable capacitance section C.

The oscillation frequency can be increased or decreased by providing a plurality of circumferential stubs on a part of the conventional microstrip line MSL ₁ and selectively removing the stubs. The increase and decrease of can be eliminated.

FIG. 3A is an external perspective view showing an embodiment of the variable capacitance section C ₃₀ , and FIG. 3B is a variable capacitance section C _30.
2 is a plan view showing the configuration of FIG. In the figure, 1 is a dielectric substrate, 2 is a chip capacitor corresponding to the capacitor C ₃ , and 3 is a capacitance pattern group corresponding to the variable capacitance section C ₃₀ . A resonant circuit section X and the like are provided on the dielectric substrate 1 or so as to be connected to the dielectric substrate 1.

The capacitance pattern group 3 is composed of a pair of comb-teeth electrode patterns 31, ..., 32.
The capacitance generated between the comb-teeth electrode patterns 31 and 32 is
This is combined with the capacitance of the chip capacitor (capacitor C ₃ ) connected in parallel with this.

Then, the comb-teeth electrode patterns 31, 3 are formed so that the control voltage and the oscillation frequency have a constant inclination.
Adjust by removing part of 2. Specifically, the base of one of the comb-teeth electrode patterns 31 is trimmed in the directions C to D in the drawing using a laser or the like. With this configuration, the capacitance of the variable capacitance section C ₃₀ can be reduced by a predetermined amount, and variation in the oscillation frequency with respect to the control voltage can be suppressed.

[0029]

As described above, according to the present invention, the variation in the control voltage sensitivity is corrected, and as a result, the variation in the modulation sensitivity can be suppressed. The voltage controlled oscillator can also simplify the adjustment process.

[Brief description of drawings]

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

FIG. 2 is an equivalent circuit diagram of a resonance circuit section of the voltage controlled oscillator of the present invention.

3A is an external perspective view of a substrate including a variable capacitance section C ₃₀ used in the voltage controlled oscillator of the present invention, and FIG. 3B is a plan view showing a configuration of the variable capacitance section C ₃₀ .

FIG. 4 is a circuit diagram of a resonance circuit unit of a typical voltage controlled oscillator.

FIG. 5 is a characteristic diagram showing a relationship between a control voltage and an oscillation frequency in an oscillation circuit of a conventional voltage controlled oscillator.

FIG. 6 is a characteristic diagram showing a relationship between sensitivity of a control voltage and a modulation signal in an oscillation circuit of a conventional voltage controlled oscillator.

[Explanation of symbols]

X ... ・ Resonance circuit section Y ・ ・ ・ ・ ・ ・ Negative resistance circuit section Z ・ ・ ・ ・ Amplification circuit section MSL ₁ , MSL ₂ , MSL ₂・ ・ Microstrip line Cv・ Variable capacitance diodes C _{1 to} C ₁₁ ... Capacitors R ₁ and R ₂ ... Dividing resistors R _{3 to} R ₇ ... Resistors

Claims (1)

[Claims] 1. A resonance circuit section including a variable capacitance diode and an inductance generating conductor, which are connected to each other via a capacitor, and a negative resistance circuit section having an active element, which is supplied to one end of the variable capacitance diode. A voltage-controlled oscillator in which a resonance frequency of a resonance circuit section is changed by changing a voltage, wherein a variable capacitance section is connected in parallel to the capacitor.