JPH05251262A - High frequency capacitor - Google Patents

Abstract

PURPOSE:To enable a high frequency capacitor to increase in a self-resonant frequency, be controlled in resonance by building a damper in a resistor so as to be less affected by resonance, and be expanded in an operating frequency range by a method wherein an electrode is lessened in inductance, and the electrode inside the terminal of a capacitor is shortened in length. CONSTITUTION:A ground conductor, a dielectric body, an inner conductor, and a dielectric body are successively formed in this order to form a multilayer unit, one or more multilayer units are stacked up to form a capacitive element, and a ground conductor and a dielectric body are successively formed on the capacitive element to form a high frequency capacitor of multilayer tri-plate strip line structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mounting circuit (S
Corresponding to MD (S urface M ount D evice )), capacitors used in high frequency, in particular to high-frequency capacitor suitable for decoupling capacitors.

[0002]

2. Description of the Related Art In a conventional high frequency amplification unit,
A method of inserting an element called a decoupling capacitor (decoupling capacitor) as shown in FIG. 8 into the circuit of the power supply line has been considered in order to prevent oscillation due to coupling between circuits. When the impedance of a normal capacitor becomes higher than the characteristic impedance of the line, the capacitor resonates and is equivalently disconnected from the circuit and does not operate as a decoupling capacitor.

Therefore, conventional high frequency decoupling
A capacitor having a structure called a feedthrough type capacitor as shown in FIG. 9 or a super pass type capacitor as shown in FIG. 10 is used as the capacitor. The feed-through capacitor or the ultra-pass capacitor has the input terminal and output terminal separated, and since the signal always passes through the capacitor, it is not separated from the circuit, and the decoupling capacitor
The frequency range that operates as a capacitor is quite wide.

[0004]

However, in these capacitors, since the wavelength inside the dielectric substrate is shortened to 1 / √ε due to the dielectric constant in the high frequency band, the electrode of the capacitor cannot be ignored compared to the wavelength. Becomes larger,
It operates as a distributed constant type line. When the line length becomes an integral multiple of 1/4 wavelength inside the substrate, the capacitor becomes a resonator, and especially when it is an even multiple of 1/4 wavelength, the input / output terminals are electrically short-circuited and do not operate as a capacitor. In order to further widen the operating range of the super-pass type capacitor, it is necessary to raise the self-resonant frequency and reduce the Q value when it becomes a resonator.

The present invention has been made to solve these problems and is intended to increase the self-resonant frequency by reducing the inductance of the electrodes and the length of the electrodes in the terminals of the capacitor, and An object of the present invention is to provide a high-frequency capacitor that incorporates a damper of a resistor to dampen resonance and reduce the influence from resonance to expand the usable frequency range.

[0006]

In order to solve the above-mentioned problems, the present invention defines a multilayer body in which a ground conductor, a dielectric, an inner conductor and a dielectric are stacked in this order as one unit, and the multilayer body of the one unit. It is characterized by comprising a multilayer triplate / stripline structure in which a ground conductor and a dielectric are further stacked in this order on a capacitor element in which at least one unit is stacked.

Further, one end of the inner conductor is used as an input terminal and the other end is used as an output terminal. Furthermore, the length of the inner conductor in the signal propagation direction is made wider than the length of the ground conductor. The terminals of the ground conductor are arranged so as to be orthogonal to the direction of the inner conductor, and the width of the take-out terminal is made narrower than that of the inner conductor. The ground conductor terminals are connected to each other by ground conductor electrodes outside the capacitor element. Further, instead of the ground conductor, a ground conductor, a dielectric, a resistor, a dielectric, a ground conductor, an element composed of a dielectric in this order, and instead of the inner conductor, an inner conductor, a dielectric, a resistor, a dielectric, An element composed of an inner conductor and a dielectric is inserted in this order.

[0008]

According to the present invention having the above-mentioned structure, the self-resonance frequency is increased by reducing the inductance of the electrode and shortening the length of the electrode in the terminal of the capacitor, and the resistor is The damper can be incorporated to dampen the resonance to reduce the influence from the resonance and expand the frequency range used.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the basic structure of the present invention. As shown in the figure, it is a structure of a multi-layer triplate strip line capable of lowering the impedance, and at least one unit or more is defined as an A unit in which a ground conductor, a dielectric, an inner conductor, and a dielectric are stacked in this order. On the stacked capacitor elements, a ground conductor to be a B unit and a dielectric are sequentially stacked. Here, in the high frequency capacitor of the present invention, the length in the signal propagation direction must be shortened in order to raise the self-resonant frequency.

Next, assuming that a part of the strip line with both ends open is used as a capacitor, the relationship between the characteristic impedance and the self-resonant frequency will be investigated. If the characteristic impedance of the strip line is Z ₀ , it becomes as shown in the following equation (1).

[0011]

[Equation 1] Where c: speed of light in vacuum, C ₀ : line capacitance per unit length,

[Equation 2] : Line length, λ: Wavelength

[0012]

[Equation 3] Then, Eq. (1) is simplified to Eq. (2) below.

[Equation 4]

As is clear from this result, the strip line with open ends, which is sufficiently shorter than the wavelength, exhibits the property of capacitance.

[0014] Here, the capacitance per unit length (characteristic impedance) is seen as a virtual strip lines such that Z ₀ and Z _0/2, the ratio of the line length to be equal both capacity

[Equation 5] become. A plot of the relationship between impedance and frequency of this line is shown in FIG. In the figure, the horizontal axis is divided by the line length / wavelength ratio (line length / frequency / light speed ∝ frequency) to make it easier to see the impedance divergence due to self-resonance.
As can be seen from FIG. 2, the slope of the impedance locus (two-dot chain line) is -1 in the frequency range where the line shows the property of capacitance, but as the frequency rises, the impedance component of the line becomes constant due to the increase of the inductance component of the line. , And the effective capacity begins to increase. When the frequency at which the characteristic impedance is Z ₀ (solid line) is increased by 30% from the initial capacitance from Fig. 2, it is about 0.
Is 15. Characteristic impedance frequency to 30% increase from the initial capacitance for line (dashed line) is Z _0/2 is seen to be about 0.3 from FIG.

From this result, it is clear that when the capacitance is regarded as a transmission line, the lower the characteristic impedance, the higher the self-resonant frequency (upper limit frequency of use), and the wider the frequency range used as capacitance can be. That is, in order to increase the upper limit frequency of use of the capacitance, the width (D) of the inner conductor is increased to reduce the characteristic impedance of the line, and the line length (length of the ground conductor and the inner conductor (d)) is shortened. The self-resonant frequency should be increased.

Specifically, the lead-out terminal on the ground conductor side is orthogonal to the input / output terminal in order to shorten the length of the ground conductor to shorten the line length and increase the upper limit frequency of use. Further, the ground conductor terminals are connected to each other by the ground conductor electrodes of the A unit.
Figure 3 shows a typical structural example that comprehensively incorporates these measures. An equivalent circuit of the structure shown in FIG. 3 is shown in FIG.

If the resonance is damped by a resistor or the like to reduce the Q value, the impedance of the capacitor is plotted as a dotted line in FIG. 2, and the upper limit frequency of use can be further expanded.

In order to prevent the loss of the capacitor from increasing due to the resistor, the resistor acts as a mode suppressing element,
It must be kept between the ground conductor and the inner conductor. Therefore, as shown in FIG. 6, instead of the ground conductor in FIG. 1, an element constituted by a ground conductor, a dielectric, a resistor, a dielectric, a ground conductor, and a dielectric in this order, and a substitute for the inner conductor in FIG. Inner conductor,
An element composed of a dielectric, a resistor, a dielectric, an inner conductor, and a dielectric is inserted in this order. The ground conductor or the inner conductor and the resistor are connected at the input and output ends so that they act as simple conductors from the outside. An example of the structure is shown in FIG.

Such an element can be used not only as a decoupling capacitor, but also as a capacitor of a circuit whose input and output terminals are separated, for example, as an external capacitor of a lumped constant type circulator as shown in FIG.

[0020]

As described above, according to the present invention, the self-resonance frequency is increased by reducing the inductance of the electrodes and the length of the electrodes in the terminals of the capacitor, and by increasing the resistance. It is possible to provide a high-frequency capacitor that incorporates a body damper to dampen the resonance and reduce the influence of the resonance to expand the usable frequency range.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic structure of the present invention.

FIG. 2 is a diagram showing a relationship between impedance and frequency in the present embodiment.

FIG. 3 is a perspective view showing an appearance of a high frequency capacitor according to the present embodiment.

FIG. 4 is a diagram showing an equivalent circuit of a high frequency capacitor according to the present embodiment.

FIG. 5 is a diagram showing the structure of another embodiment of the present invention.

FIG. 6 is a perspective view showing an appearance of a high frequency capacitor according to another embodiment.

FIG. 7 is a diagram showing an example in which the high frequency capacitor of the present invention is used in a lumped constant type circulator.

FIG. 8 is a circuit diagram showing a usage state of a decoupling capacitor used in a conventional high frequency amplification unit.

FIG. 9 is a diagram showing a feedthrough capacitor.

FIG. 10 is a diagram showing a superpass type capacitor.

Claims (6)

[Claims] 1. A multilayer body in which a ground conductor, a dielectric, an inner conductor, and a dielectric are stacked in this order is defined as one unit, and at least one unit of the multilayer body of the unit is stacked on a capacitor element. , A high frequency capacitor having a structure in which dielectrics are sequentially stacked. 2. The high frequency capacitor according to claim 1, wherein one end of the inner conductor serves as an input terminal and the other end serves as an output terminal. 3. The high frequency capacitor according to claim 1, wherein the length of the inner conductor in the signal propagation direction is made wider than the length of the ground conductor. 4. The high frequency capacitor according to claim 1, wherein the terminal of the ground conductor is arranged so as to be orthogonal to the direction of the inner conductor, and the width of the lead terminal is narrower than the width of the inner conductor. 5. The high frequency capacitor according to claim 1, wherein the terminals of the ground conductor are connected to each other by a ground conductor electrode outside the capacitor element. 6. An element constituted by a ground conductor, a dielectric, a resistor, a dielectric, a ground conductor, and a dielectric in this order instead of the ground conductor,
The high-frequency capacitor according to claim 1, wherein an element composed of an inner conductor, a dielectric, a resistor, a dielectric, an inner conductor, and a dielectric is inserted in place of the inner conductor.