JPH10173439A - Voltage controlled oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage controlled oscillator providing a strip line resonator in the inside layer of a multilayer substrate and less in the dispersion of oscillation frequency by humidity. SOLUTION: Polytetrafluoroethylene is used as the core material of the multilayer substrate. Since the polytetrafluoroethylene has smaller water absorptivity than glass epoxy, the change of dielectricity to the change of humidity. As a result, also the change of the resonant frequency of the strip line resonator formed in the inside layer of the multilayer substrate is small, as a result, also the change of oscillation frequency becomes small. Then, since the change of the oscillation frequency is small, control voltage sensitivity can be reduced, and thus, C/N characteristics is improved. Then, since also the property of the polytetrafluoroethylene material itself is small in dielectric loss comparing with the glass epoxy and also specific dielectricity is small, the Q of resonant system is improved, and thereby, the C/N characteristics is improved too.

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, and more particularly to a modular voltage controlled oscillator constructed on a dielectric substrate.

[0002]

2. Description of the Related Art In a conventional voltage controlled oscillator, glass epoxy or ceramic is used as a dielectric material of a multilayer substrate constituting a module, a resonator having a strip line structure is formed in an inner layer thereof, and a circuit pattern is formed thereon. The active element, the varactor diode, the capacitor and the like are mounted to form a voltage controlled oscillation circuit.

[0003]

However, when glass epoxy is used as a dielectric material, the water absorption of glass epoxy is relatively large, which causes expansion of the substrate and changes in the dielectric constant. However, there is a problem that the resonance frequency of the strip line resonator formed in the inner layer greatly varies depending on the humidity, and as a result, the oscillation frequency of the voltage controlled oscillator greatly varies.

In order to compensate for the variation in the oscillation frequency, a measure is taken to increase the control voltage sensitivity of the oscillation frequency (the ratio of the change in the oscillation frequency to the change in the control voltage). There is a problem that the C / N characteristics of the oscillator deteriorate.

On the other hand, when ceramic is used as a dielectric material, there is no problem of variation in oscillation frequency due to humidity unlike glass epoxy, but on the contrary, processing cost and material cost are relatively high, and processing accuracy is relatively high. However, there is a problem that the yield of the multilayer substrate is poor due to the poor quality, and the price of the voltage controlled oscillator is high.

SUMMARY OF THE INVENTION An object of the present invention is to provide a voltage controlled oscillator which is low in cost, has good processing accuracy, and has little variation in oscillation frequency due to humidity.

[0007]

In order to achieve the above object, a voltage controlled oscillator according to the present invention uses a multilayer substrate having polytetrafluoroethylene as a core material, and has a stripline structure in its inner layer. A resonator is formed, and components are mounted on the resonator.

[0008]

FIG. 1 shows an embodiment of a voltage controlled oscillator according to the present invention. FIG. 1 is a partial cross-sectional view of a voltage-controlled oscillator based on a multilayer substrate having polytetrafluoroethylene as a core material as viewed from the side.

In FIG. 1, a voltage controlled oscillator 1 is a poly-
It comprises a multilayer substrate 2 having three dielectric layers each having tetrafluoroethylene as a core material, and electronic components 3 mounted thereon, such as transistors, varactor diodes, and capacitors. The multilayer substrate 2 has three dielectric layers 2a, 2
b and 2c, and four conductor layers 2d, 2e, 2f and 2g. Of these, the conductor layers 2e and 2g are ground layers, a strip line resonator is formed on the conductor layer 2f, and the conductor layer 2d forms a circuit pattern on which the component 3 is mounted. The strip line resonator formed in the conductor layer 2f is connected to a circuit formed on the conductor layer 2d by a through hole or a via hole.

In the voltage controlled oscillator 1 configured as described above, the resonance frequency of the resonator formed on the conductor layer 2f depends on the permittivity and the thickness of the upper and lower dielectric layers 2b and 2c. However, since the dielectric layers 2b and 2c are made of polytetrafluoroethylene, the water absorption is small and the change in the dielectric constant is small. As a result, it is possible to reduce a change in the resonance frequency of the strip line resonator with respect to the humidity and a change in the oscillation frequency of the voltage controlled oscillator 1.

FIG. 2 shows the results of a humidity resistance test of the oscillation frequency of the voltage controlled oscillator of the present invention and a conventional voltage controlled oscillator using glass epoxy as a substrate material. The conditions of the humidity resistance test were 80 degrees Celsius, 85% relative humidity, and 100%.
0 hours. As can be clearly seen from FIG. 2, the change of the oscillation frequency in the moisture-resistant storage is about 1/6 when polytetrafluoroethylene is used as the substrate material compared to when glass epoxy is used as the substrate material. .

On the other hand, when the change in the oscillation frequency is reduced as described above, the control voltage sensitivity of the voltage-controlled oscillator becomes unnecessarily large, which has conventionally been set slightly larger in consideration of the change in the oscillation frequency. You don't have to.
The control voltage sensitivity indicates the change in the oscillation frequency with respect to the change in the voltage applied to the control terminal of the voltage controlled oscillator. Decreasing the control voltage sensitivity means that the frequency variable circuit and resonance circuit mounted on the voltage controlled oscillator Weakening the bond with

FIG. 3 shows a circuit diagram of a resonance system portion of the voltage controlled oscillator. In FIG. 3, the resonance system 10 includes a resonator 1
1, capacitors 12 and 13, varactor diode 1
4, a choke coil 15 and a control voltage terminal 16. The resonator 11 and the capacitor 12 form a resonance circuit 17 with the capacitor 13 and the varactor diode 1.
4. The choke coil 15 forms the frequency variable circuit 18. The resonator 11 is connected via a capacitor 12 to an oscillation system (not shown). Varactor diode 1
The cathode of 4 is connected to the resonator 11 via the capacitor 13, is connected to the control voltage terminal 16 via the choke coil 15, and the anode is grounded.

In this resonance system 10, the control voltage sensitivity is determined by the contribution ratio of the change in the capacitance of the varactor diode 14 to the resonance system 10 due to the control voltage applied from the control voltage terminal 16, so that the resonance circuit 17 It is determined by the strength of the coupling of the variable circuit 18, that is, the magnitude of the capacitance of the capacitor 13 connecting the two. When the capacitance of the capacitor 13 is large, the control voltage sensitivity increases, and when the capacitance of the capacitor 13 is small, the control voltage sensitivity decreases.

When the capacity of the capacitor 13 is large, the resistance component included in the varactor diode 14 has a large influence on the resonance system 10, and as a result, the Q of the resonance system 10 is deteriorated. Conversely, if the capacitance of the capacitor 13 is small,
The effect of the resistance component of the varactor diode 14 is reduced, and the Q of the resonance system 10 is improved. That is, by reducing the control voltage sensitivity, the Q of the resonance system can be improved.

On the other hand, polytetrafluoroethylene has a small dielectric loss tangent with respect to glass epoxy, and therefore has a small dielectric loss. This is one of the causes for improving the Q of the resonance system.
It is one.

Furthermore, polytetrafluoroethylene has a lower dielectric constant than glass epoxy. When the relative dielectric constant is small, the inductance component of the strip line resonator becomes larger than the capacitance component, which is also one of the causes for improving the Q of the resonator, that is, the Q of the resonance system.
Has become one.

As described above, the Q of the resonance system can be improved due to the fact that the control voltage sensitivity can be reduced and the characteristics of the dielectric material itself. As a result, the C / N characteristic, which is one of the important characteristics of the voltage controlled oscillator and depends on the Q of the whole resonance system, can be improved.

FIG. 4 shows changes in C / N characteristics with respect to control voltage sensitivity of the voltage controlled oscillator of the present invention and a conventional voltage controlled oscillator using glass epoxy as a substrate material.
As can be seen from FIG. 4, according to the voltage controlled oscillator of the present invention, the C / N characteristics could be improved by about 3 dB as compared with the case where a glass epoxy substrate was used.

Further, the property that the dielectric loss of poly-tetra-fluoro-ethylene is small and the property that the relative dielectric constant is small are dared to have the same C / N characteristics as when a glass epoxy substrate is used. Even if Q is degraded, the thickness of the multilayer substrate can be made smaller than when glass epoxy is used as a material. In this case, the thickness of the multilayer substrate can be reduced, and the height and the weight of the voltage controlled oscillator can be reduced.

[0021]

According to the voltage controlled oscillator of the present invention, a stripline resonator is formed in the inner layer, and polytetrafluoroethylene is used as a dielectric material of a dielectric substrate on which components are mounted. By doing so, a change in the oscillation frequency with respect to humidity is reduced. As a result, the control voltage sensitivity can be reduced and the C / N characteristics can be improved. Also, the C / N characteristics can be improved by reducing the dielectric loss of the dielectric material.

Conversely, if the C / N characteristics are the same as in the prior art, the thickness of the dielectric of the multilayer substrate can be reduced so that the height and weight of the voltage controlled oscillator can be reduced.

[Brief description of the drawings]

FIG. 1 is a side view showing one embodiment of a voltage controlled oscillator of the present invention.

FIG. 2 is a diagram showing the results of a humidity resistance test of the oscillation frequency of the present invention and a conventional voltage controlled oscillator.

FIG. 3 is a circuit diagram showing a configuration of a resonance system of the voltage controlled oscillator according to the present invention.

FIG. 4 is a diagram showing the relationship between control voltage sensitivity and C / N characteristics of the present invention and a conventional voltage controlled oscillator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Voltage controlled oscillator 2 ... Multilayer board 2a, 2b, 2c ... Dielectric layer 2d, 2e, 2f, 2g ... Conductor layer 3 ... Parts

Claims (1)

[Claims] 1. A multi-layer substrate having polytetrafluoroethylene as a core material, a resonator having a stripline structure formed in an inner layer thereof, and components mounted thereon. Voltage controlled oscillator.