JP2007049280A - Oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillator preventing characteristics from fluctuating sharply even if confirming or adjusting circuit operation while a shield case has been removed. <P>SOLUTION: The oscillator comprises an electronic circuit including inductance formed on the surface of a substrate; a ground pattern formed on the rear surface of the substrate; and upper and lower shield cases formed on both surfaces of the substrate at a prescribed distance. In this case, the rear-side ground pattern is removed partially in which the inductance is formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an oscillator in which a resonance circuit constituted by a pattern inductor on a substrate is affected by an electromagnetic field by a shield case and the oscillation frequency of the oscillator is suppressed from fluctuating.

  For example, the following patent documents are known as techniques relating to frequency adjustment of an oscillator having a shield case such as a VCO (voltage controlled oscillator).

JP 2000-295035 A

FIG. 8 is a sectional view showing a conventional oscillator described in the above-mentioned patent document.
In the figure, the oscillator 200 includes a shield case 201 and a multilayer substrate 210 having a plurality of layers, and components such as chip components and surface mount components are mounted on the multilayer substrate 210.

  Here, ground electrodes 207 and 208 and a strip line 206 are formed in the inner layer of the multilayer substrate 210. The electrode 203 connected to one end of the strip line 206 via the through hole 204 and the ground side electrode 202 connected to the ground electrode 208 constitute a multilayer capacitor. This multilayer capacitor is a frequency adjusting capacitor.

  Then, as shown in FIG. 8, by providing the hole 209 in the multilayer substrate 210 from the bottom surface side of the substrate 210 toward the component mounting surface (in the direction of the arrow T), the electrode in the hole 209 portion becomes the electrode 203 and The electrode 202 is deleted. That is, in the multilayer capacitor including the electrode 203 and the electrode 202, a part of the electrode 203 and the electrode 202 is deleted, the capacitance of the multilayer capacitor is changed, and as a result, the resonance frequency is changed. Therefore, by providing the hole 209 in the substrate 210, the oscillation frequency of the oscillator can be adjusted.

  FIG. 9 is a layer configuration diagram of a substrate of a high-frequency oscillator showing another conventional example. The resonator is composed of an LC resonance circuit (not shown), and the inductor is composed of a pattern inductor 104. Usually, the transmission line on the substrate is generally constituted by a microstrip line, but in this resonant circuit substrate, the ground plane on the back surface is omitted in order to increase the Q value. Upper and lower shield cases 101 and 102 for preventing external electromagnetic fields are attached to the substrate.

  FIG. 10 shows the electric field distribution between the pattern inductor 104 and the shield cases 101 and 102. When the oscillator is operating, an electric field 204 as shown is generated between the pattern inductor 104 formed on the dielectric substrate 103 and the shield cases 101 and 102.

  FIG. 11 shows a primary constant of the transmission line of the pattern inductor. As shown in the figure, the primary constant of the transmission line is determined by the distance between the pattern inductor 104 and the shield cases 101 and 102, and the oscillation frequency of the oscillator is determined. The Q value is also determined by the conductor loss of the pattern inductor 104. Note that 104aL1 is an inductive component of the pattern inductor, 104b is a resistance component, 104c is a stray capacitance formed between the pattern inductor and the shield case, and 104d is a resistor formed between the pattern inductor and the shield case.

  The oscillation frequency of the oscillator is designed in consideration of the electromagnetic coupling between the shield cases 101 and 102 and the pattern inductor 104, but actual circuit operation confirmation and adjustment are often performed with the shield case removed. This changes the electromagnetic field distribution between the shield case and the pattern.

  FIG. 12 shows the relationship between the distance from the substrate surface to the shield case and the oscillation frequency in the case of a broadband VCO of 1 GHz band having a thickness of the dielectric 103 of t = 0.7 mm and a dielectric constant of 3.4 in FIG. Is. As shown in the figure, the fluctuation of the frequency is shifted by 30% toward the low frequency side when the case is away from the case when the case is close to the substrate.

  Therefore, the circuit operation check and adjustment with the shield case removed are performed in a state different from the design, which is a problem. Further, when the shield case vibrates even in a normal operation state, there is a problem that FM modulation is applied when the distance from the substrate changes, and unnecessary spectrum and noise are generated.

The present invention is a high-frequency oscillator in which a resonant circuit is configured by a pattern inductor, while maintaining a high Q value.
(1) Suppress fluctuations in oscillation frequency due to the presence or absence of a shield case.
(2) Significantly reduce the effects of mechanical vibration.
It is for the purpose.

  The present invention has been made to solve the above problems, and in the oscillator according to claim 1, an electronic circuit including an inductance formed on the surface of the substrate, a ground pattern formed on the back surface of the substrate, The upper and lower shield cases are formed on both sides of the substrate at a predetermined distance, and the ground pattern on the back side where the inductance is formed is partially removed.

In the oscillator according to claim 2, the oscillator according to claim 1,
The partial removal of the ground pattern is performed so that an electric field is generated between the ends of the inductance and the ends of the removed ground pattern.

In the oscillator according to claim 3, in the oscillator according to claim 1 or 2,
The substrate is made of a dielectric material.

In the oscillator according to claim 4, the oscillator according to claims 1 to 3,
The inductance is formed by a pattern.

The present invention has the following effects.
According to invention of Claims 1-4, the electronic circuit containing the inductance formed in the surface of the board | substrate, the ground pattern formed in the back surface of the said board | substrate, and the both sides of the said board | substrate are separated by predetermined distance. Since the ground pattern on the back side where the inductance is formed is partially removed, the characteristics are great even if the circuit operation is confirmed and adjusted with the shield case removed. There is no fluctuation.

Hereinafter, the present invention will be described in detail with reference to the drawings.
1 is a cross-sectional view showing an example of an oscillator according to the present invention, FIG. 2 is a plan view of the dielectric substrate shown in FIG. 1, and FIG. 3 is a back view of the dielectric substrate shown in FIG. In these drawings, the difference from the conventional example shown in FIG. 9 is that the ground plane (GND) provided on the back surface of the dielectric substrate and the GND of the portion where the pattern inductor 104 formed on the surface of the dielectric substrate is formed. It is the point which removed. In the figure, electronic components other than the ground plane constituting the resonator are omitted. Further, as shown in the figure, it is assumed that the pattern inductor has two patterns of the same shape with different widths arranged at a predetermined distance from each other at four locations.

  Here, when the ground plane is provided on the entire back surface of the dielectric substrate 103, a capacitance C1a (larger than the stray capacitance C1 (104c) shown in FIG. 11 is interposed between the pattern inductor 104 and the ground plane 105 as shown in FIG. 104c1) is generated. When the pattern inductance equivalent to that when there is no ground plane is obtained, the wiring length becomes long, and the resistance value per unit minute length is approximately the same between the resistor 104b: R1 shown in FIG. 11 and the resistor 104b: R2 shown in FIG. Therefore, the conductor loss of the pattern inductor 104 is increased.

When the constants of the LCR series resonator are L and R, the Q value is determined as follows when the resonance frequency is fo: Q = 2πf ₀ L / R
That is, as the conductor loss increases, the Q value deteriorates. Therefore, in the present invention, as shown in the cross-sectional view of FIG. 1 and the back view of FIG. 3, in order to prevent the Q value from being lowered as much as possible, the ground plane immediately below the pattern inductor forming the resonator is removed.

  When the ground plane is removed, the electric field concentrates between the edge of the pattern inductor 104 and the edge of the ground plane 105 as shown in FIG. As a result, the primary constant of the pattern inductance is determined, and the influence of coupling between the pattern inductor 104 and the shield cases 101 and 102 is reduced. 10 and 5, it can be seen that the electric field from the pattern inductor 104 toward the shield cases 101 and 102 is smaller in FIG.

  FIG. 6 shows an example of the relationship between the distance between the edge of the pattern inductor 104 and the edge of the ground plane 105, the frequency variation depending on the presence or absence of the shield case, and the Q value. As the distance from the edge to the edge increases, the Q value increases, but the influence of the ground plane disappears and approaches the Q value when there is no ground plane. Moreover, although the frequency fluctuation increases, the influence of the ground plane gradually disappears and becomes a constant value. From this relationship, it is possible to set an optimum value that prevents a decrease in the Q value within a range in which the frequency fluctuation can be suppressed.

As an example, a 1 GHz VCO having a configuration in which the dielectric thickness is 0.7 mm, and the horizontal distance between the pattern edge and the ground plane shown in FIG. 3 is f = 2.75 mm, g = 1.45 mm, and h = 7.9 mm. In the case of the experiment, the distance between the dielectric substrate 103 and the shield cases 101 and 102 shown in FIG. 1 is H1 = 8 mm and H2 = 5 mm. As a result, the frequency error due to the presence or absence of the shield case is 1 as shown in FIG. It was possible to suppress it to 5%. The dimensions of the substrate and pattern inductor were as follows.
For the substrate, a = 40mm, b = 30mm
C = 25 mm, c ′ = 15 mm for the removed portion of the ground plane
About pattern inductors
d = 3mm, e = 3mm, j = 8mm, i = 10mm

  Further, the Q value does not vary greatly depending on the presence or absence of the shield case, and is kept at the optimum value. Therefore, even if the circuit operation is confirmed and adjusted with the shield case removed, the characteristics are not greatly changed.

  The foregoing description of the present invention has only shown certain preferred embodiments for purposes of illustration and illustration. For example, the shape of the pattern inductor is not limited to the illustrated example and can be changed as appropriate. Accordingly, it will be apparent to those skilled in the art that the present invention can be modified and modified in many ways without departing from the essence thereof. The scope of the present invention defined by the description in the appended claims is intended to include modifications and variations within the scope.

It is a block diagram of the principal part which shows one Example of the oscillator which concerns on this invention. It is a top view of the dielectric substrate which comprises the oscillator which concerns on this invention. It is a back view of the dielectric substrate which comprises the oscillator which concerns on this invention. It is a figure which shows the stray capacitance at the time of providing a ground plane (GND). It is a figure which shows the state of the electric field at the time of providing a ground plane (GND). It is a figure which shows the relationship between the horizontal distance from a pattern edge to a ground plane, and a frequency fluctuation. It is a figure which shows the relationship between a VOC adjustment voltage and an oscillation frequency. It is a cross-sectional block diagram which shows an example of the conventional oscillator. It is a cross-sectional block diagram which shows another example of the conventional oscillator. It is sectional drawing which shows the state of the electric field of the prior art example shown in FIG. It is a figure which shows the stray capacitance of the conventional oscillator. It is a figure which shows the relationship between the distance from a dielectric substrate to a shield case, and an oscillation frequency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Upper shield case 102 Lower shield case 103 Dielectric board 104 Electric field 105 Ground plane 200 Oscillator 201 Shield case 202,203 Electrode 204 Through hole 206 Strip line 207,208 Ground electrode 209 Hole 210 Multilayer board

Claims (4)

  An electronic circuit including an inductance formed on the surface of the substrate, a ground pattern formed on the back surface of the substrate, and upper and lower shield cases formed on both surfaces of the substrate with a predetermined distance therebetween, An oscillator, wherein a ground pattern on the back side where the inductance is formed is partially removed.   2. The oscillator according to claim 1, wherein the ground pattern is partially removed to such an extent that an electric field is generated between the ends of the inductance and the ends of the removed ground pattern.   The oscillator according to claim 1, wherein the substrate is made of a dielectric. 4. The oscillator according to claim 1, wherein the inductance is formed by a pattern.

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