JP5356200B2 - High frequency device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high-frequency device, which is free from fluctuation of the resonance frequency of a case even if a cover fluctuates due to heat and vibrations, and which stabilizes the transmission characteristic of a high-frequency circuit. <P>SOLUTION: The high-frequency device includes a metallic casing body 51 wherein an opening is formed in its upper surface and a high-frequency circuit is housed inside, and a box-like metallic cover 52 to cover the opening in the upper surface of the casing body 51, and an insulating body 53 is provided at a position where the upper surface of a sidewall comprised of a plurality of sides of the casing body 51 and the inside of a upper plate part of the cover come into contact with each other. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a high-frequency device including a casing main body in which a high-frequency circuit is accommodated and a box-shaped lid that covers an upper surface opening of the casing main body.

  For high-frequency devices with built-in high-frequency circuits that operate in high-frequency bands such as the microwave band or the millimeter-wave band, in order not to be affected by the external environment, and to satisfy EMI standards of various radio wave laws Usually, it is housed in a high-frequency shield case.

  There exists patent document 1 as a prior art regarding such a high frequency shield case. In Patent Document 1, a high-frequency shield case is constituted by a box-shaped housing having an upper surface opened and a high-frequency circuit built therein and a shield cover covering the box, and a side plate portion of the shield cover is provided. Bends so that elastic force is applied, and protrusions for forming contact points are formed at equal intervals of 1 / n (n is an integer of 1 or more) of the wavelength of the high frequency at the protruding end portion of the bent side plate portion. It is formed to improve the shielding effect.

Japanese Utility Model Publication No. 61-190197

  However, the technique disclosed in Patent Document 1 is configured such that the upper surface of the frame body constituting the housing is brought into contact with the inner side of the upper plate portion of the shield cover, and the clearance between the upper surface of the frame body and the inner side of the upper plate portion of the shield cover is defined. It has not been. For this reason, in the prior art, when vibration or temperature change occurs, there is a possibility that the upper surface of the frame body and the inside of the upper plate portion of the shield cover may come into contact with or separate from each other. Since the resonance frequency of the shield case is determined by the inner dimensions of the shield case consisting of the housing and the shield cover, in the above conventional technology, the upper surface of the frame body and the inner side of the upper plate of the shield cover are not contacted. When contact is made from non-contact, the inner dimensions of the shield case will change greatly, the resonance frequency of the shield case will change, and the impedance of the space seen from the built-in high-frequency circuit will change. There is a problem that the transmission characteristics of the circuit change.

  The present invention has been made in view of the above, and even if the lid is displaced from the case main body due to vibration or temperature change, the resonance frequency of the case does not change, and the transmission characteristics of the high-frequency circuit are stabilized. An object is to obtain a high-frequency device that can be realized.

In order to solve the above-described problems and achieve the object, the present invention includes a metal casing body having a plurality of side walls , an opening formed on the upper surface, and a high-frequency circuit accommodated therein, A box-shaped metal lid having a top plate covering the upper surface opening of the casing body and a plurality of side plates covering the plurality of side walls and contacting the plurality of side walls. provided, wherein the the upper surface of the plurality of side walls of the casing body, a top plate portion inside of the lid is to provide an insulating body portion abuts.

  As described above, according to the present invention, since the insulator is interposed between the lid and the casing body, and the lid does not contact the upper surface of the casing body, the resonance frequency is the inner dimension of the lid. Even if the lid body fluctuates due to heat or vibration, the inner dimension that defines the resonance frequency does not change, so that the change in the resonance frequency can be suppressed. Thereby, the impedance of the space seen from the high frequency circuit built in the casing body does not change, and the transmission characteristics of the built-in high frequency circuit are stabilized. Moreover, since an insulator can be arrange | positioned in the two-dimensional direction of x and y, the change of a resonant frequency can be suppressed more.

It is a functional block diagram of the FMCW radar apparatus which can apply this invention. It is a block diagram which shows the internal structure of the oscillator of a FMCW radar apparatus. It is a block diagram which shows the internal structure of the amplifier of a FMCW radar apparatus. 6 is a perspective view showing a high-frequency device of Comparative Example 1. FIG. It is sectional drawing which shows the latching structure of a cover body and a casing main body. It is sectional drawing which shows the shield case at the time of lid | cover normal mounting | wearing. It is sectional drawing which shows the shield case at the time of lid | cover abnormal mounting | wearing. It is a graph which shows the simulation result which shows the change of the resonant frequency when the mounting | wearing state of a cover body is variously changed in the shield case of the comparative example 1 . It is a perspective view which shows the structure of the shield case for creating the simulation result of FIG. It is a perspective view which shows the modification of the high frequency device of the comparative example 1 . 10 is a cross-sectional view showing a high-frequency device of Comparative Example 2. FIG. It is a sectional view showing a high-frequency device in the form status of implementation. Is a plan view showing a high-frequency device in the form status of implementation. It is a sectional view showing a high-frequency device in the form status of implementation at the lid abnormal wearing. It is a perspective view which shows a prior art. It is sectional drawing which shows the conventional shield case at the time of shield cover normal mounting | wearing. It is sectional drawing which shows the conventional shield case at the time of shield cover abnormal mounting | wearing. It is a graph which shows the simulation result which shows the change of the resonant frequency when the mounting state of a shield cover is changed variously in the conventional shield case. It is a perspective view which shows the structure of the shield case for producing the simulation result of FIG.

  Embodiments of a high-frequency device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

First, in order to facilitate understanding of the present invention, the prior art disclosed in Patent Document 1 described above will be described with reference to FIGS. FIG. 14 shows a shield case disclosed in Patent Document 1, and this shield case includes a casing 100 and a shield cover 101. FIG. 15A is a cross-sectional view taken along the line BB ′ of FIG. 14 in a state where the shield cover 101 is normally attached to the housing 2. In the case of the conventional shield case shown in FIG. 14, when the shield cover 101 is attached to the housing 100, a structure in which the upper plate surface of the shield cover 101 is supported by all four side walls constituting the housing 100. Therefore, the resonance frequency of the shield case is determined by the inner dimensions of the shield case constituted by the casing 100 and the shield cover 101, and as shown in FIG. If the dimensions are a, b, c,
Resonance frequency≈ [C × {(L / a) ² + (M / b) ² + (N / c) ² } ^1/2 ] / 2
... (1)
C: speed of light
L, M, N: An integer of 1 or more. However, the above equation (1) is for the case where the inside of the shield case is air.

  As shown in FIG. 15A, when the shield cover 101 is normally attached to the housing 2, the inner dimension of the shield case in the x direction that defines the resonance frequency is the distance between the side walls of the housing 100. a. On the other hand, FIG. 15-2 shows a BB ′ cross section of FIG. 14 when the shield cover 101 is inclined obliquely to the housing 2. As shown in FIG. 15-2, when the shield cover 101 fluctuates due to heat or vibration and is not normally attached to the housing 2, the inner dimension of the shield case in the x direction that defines the resonance frequency is, for example, Thus, the distance a ′ between the side plates of the shield cover 101 is obtained.

  As described above, in the conventional configuration, the resonance frequency of the shield case is defined when the upper plate of the shield cover 101 changes from contact to non-contact with the side wall portion of the housing 100 or from non-contact to contact. Since the internal dimensions change greatly, there is a problem that the resonance frequency of the case changes greatly, the impedance of the space seen from the built-in high frequency circuit changes, and the transmission characteristics of the high frequency circuit change.

  FIG. 16 shows a state in which the upper plate of the shield cover 101 is in contact with the housing 100 as shown in FIG. 15A and the shield cover 101 is attached to the housing 100 as shown in FIG. 6 shows simulation results showing changes in the resonance frequency when gaps of various dimensions are generated between the upper plate of the shield cover 101 and the housing 100, which are arranged obliquely. The gap described in FIG. 16 refers to the interval between the side wall of the housing 100 and the upper plate of the shield cover 101, as shown in FIG. 15-2. The simulation results shown in FIG. 16 show the transmission characteristics (pass characteristics) between both ends 102a-102b of the line 102 formed in the conventional shield case as shown in FIG.

  As can be seen from FIG. 16, the resonance frequency of the shield case changes greatly at the moment when the shield cover 101 changes from the contact state to the non-contact state with respect to the housing 100, and thereafter, resonance occurs even if the gap distance changes. The frequency has not changed much. This is because, as described above, when the shield cover 101 is separated, the dimension in the x direction, which has been determined only by the inner dimension of the casing 100 until then, changes to the inner dimension of the shield cover 101. As described above, in the related art, when the mounting state of the shield cover 101 with respect to the housing 100 is changed from contact to non-contact due to heat, vibration, or the like, the resonance frequency of the shield case is greatly changed and viewed from the built-in high frequency circuit. Since the impedance of the space changes, there is a problem that the impedance of the transmission line changes and the high frequency characteristics change greatly.

Comparative Example 1
A first comparative example of the present invention will be described with reference to FIGS. FIG. 1 is a functional block diagram of an FMCW radar apparatus to which the present invention is applied. In FIG. 1, an oscillator 7 oscillates a high frequency signal. Part of the high-frequency signal output from the oscillator 7 is input to the amplifier 8. The amplifier 8 amplifies the input high frequency signal and obtains a transmission signal. This transmission signal is applied to the target via an antenna (not shown). A signal reflected from the target, that is, a received signal is input via the antenna. This received signal is frequency-converted by the mixer 9 and output from the mixer 9 as a video signal including information on the distance to the target and information on the relative speed. The video signal is input to a signal processing unit (not shown), and a distance to the target and a relative speed are obtained by applying processing such as A / D conversion and Fourier transform.

  FIG. 2 shows the internal configuration of the oscillator 7. In this oscillator 7, a resonant circuit 11 is provided on the input side of an active circuit 10 such as an FET, and a matching circuit 12 is provided on the output side thereof, and generates a high-frequency signal having a desired frequency.

  FIG. 3 shows the internal configuration of the amplifier 8. In this amplifier 8, matching circuits 14 and 15 are provided on the input / output side of the active circuit 13 such as an FET, and the output of the oscillator 7 is amplified so as to obtain a transmission output at a desired frequency (output frequency of the oscillator 7).

  Radars with such a configuration are generally installed at airports for use in control operations, installed in automobiles to detect obstacles ahead of the automobile, or installed on the side of expressways for obstacles on the road. Used for purposes such as detecting objects.

FIG. 4 shows the configuration of Comparative Example 1 for the shield case 3 in which the high-frequency circuits such as the oscillator 7 and the amplifier 8 described above are accommodated. As shown in FIG. 4, the shield case 3 includes a rectangular metal casing body 1 in which the high-frequency circuit 4 is accommodated, and a rectangular box-shaped metal lid 2. The casing main body 1 has an upper surface portion and a lower surface portion that are open, and is composed of four side wall portions 1a to 1d. The casing body 1 composed of these four side wall portions 1 a to 1 d is fixed on the dielectric substrate 5 by a connection method such as soldering, and the high-frequency circuit 4 is mounted on the dielectric substrate 5. The substantially box-shaped lid 2 includes four side plate portions 2a to 2d and an upper plate portion 2e, and is attached to the casing body so as to cover the upper surface opening of the casing body 1.

  The side plate portions 2a to 2d of the lid body 2 are bent so that elastic force is applied. In addition, two small hole portions 6a are formed in the two opposing side plate portions 2a and 2c as shown in FIG. The interval between the two holes 6 a is set to be less than ½ of the effective wavelength λ of the high frequency signal used in the high frequency circuit 4. On the other hand, as shown in FIG. 5, two projections 6b that fit into the hole 6a are formed on the side walls 1a and 1c of the casing body 1, respectively. Therefore, when the lid body 2 is attached to the casing body 1, the side plate portion of the lid body 2 can be obtained by the action of the side plate portions 2a to 2d of the bent lid body 2 and the fitting of the projections 6b to the hole portions 6a. Is locked while being in contact with the side wall of the casing body.

  As shown in FIGS. 6A and 6B, ground conductors 70 are formed on the upper and lower surfaces of the dielectric substrate 5, and these ground conductors 70 are connected by ground vias 71. As shown in FIG. 4, a microstrip line 20 is formed on the upper surface of the dielectric substrate 5 in order to connect the high-frequency circuit 4 in the shield case 3 and other circuits outside the shield case 3. . The microstrip line 20 is formed inside and outside the shield case 3 through a small hole 21 formed in the side wall 1 b of the casing body 1.

Next, the main part of the comparative example 1 is demonstrated. In the first comparative example , of the side walls 1a and 1c on the opposite sides of the side walls 1a to 1d composed of a plurality of sides, the upper surfaces of the side walls 1a and 1c are inside the upper plate 2e of the lid 2. A cutout portion 30 is formed on the upper side of the side wall portions 1a and 1c so as not to come into contact with (the back side). This notch 30 has a whole side notched from one end to the other end. Therefore, when the lid body 2 is fitted, the inner side (back side) of the upper plate portion 2e of the lid body 2 is in contact with only the side wall portions 1b and 1d of the casing body 1, and the side wall portions 1a and 1c are There is no contact with the inside of the upper plate portion 2e of the lid 2 and a space is formed.

  FIG. 6A shows a cross section taken along the line AA ′ of FIG. 4 in a state where the lid 2 is normally attached to the casing body 1. As shown in FIG. 6A, when the lid body 2 is normally fitted into the casing body 1, the side wall portions 1a and 1c are in contact with the inner side (back side) of the upper plate portion 2e of the lid body 2. There is no space. FIG. 6B is a cross-sectional view taken along the line AA ′ of FIG. 4 in a state where the lid body 2 is attached obliquely to the casing body 1, and the side wall portion 1a and the upper plate portion 2e of the lid body 2 are illustrated. Is a gap at the time of normal installation + an additional gap Δq.

As shown in the above formula (1), the resonance frequency in the shield case 3 is determined by the internal dimensions of the shield case 3. In the case of the shield case 3 of Comparative Example 1 , as shown in FIG. 6A, when the lid 2 is normally fitted into the casing body 1, the dimension in the x direction that defines the resonance frequency is the side wall 1a. , 1c, a space is formed, and therefore L is the inner dimension of the lid 2.

  On the other hand, as shown in FIG. 6B, when the lid 2 is disposed obliquely with respect to the casing body 1, the dimension in the x direction that defines the resonance frequency is L ′, which is the inner dimension of the lid 2. Thus, there is no significant change between L ′ and L. Therefore, even if the lid body 2 moves minutely in the direction away from the casing body 1 due to vibration or temperature change, the dimension in the x direction orthogonal to the side wall portions 1a and 1c in which the cutout portions 30 are formed does not change. The resonance frequency of case 3 does not change.

7 shows a state in which the lid 2 is normally attached to the casing body 1 as shown in FIG. 6A and the lid 2 is attached to the casing body 1 as shown in FIG. The simulation result which shows the change of the resonant frequency at the time of arrange | positioning diagonally with respect to is shown. “No gap” in FIG. 7 means a state in which the lid body 2 is normally attached as shown in FIG. 6A. “Gap 20 μm” means the additional gap Δq = 20 μm shown in FIG. The state of. The simulation results shown in FIG. 7 show the transmission characteristics (pass characteristics) between both ends 31a-31b of the line 31 formed in the shield case 3 of Comparative Example 1 , as shown in FIG.

  As can be seen from FIG. 7, the lid 2 is in the normal mounting state shown in FIG. 6A (corresponding to no gap in FIG. 7) to the abnormal mounting state shown in FIG. Even if it changes to 1000 μm), the resonance frequency hardly changes. Even if the gap interval changes from 40 μm to 1000 μm, the resonance frequency hardly changes.

As described above, according to Comparative Example 1 , the upper plate portion 2e of the lid 2 is not in contact with the upper surface of the casing body 1 even when the lid 2 is normally mounted. Even if the lid 2 fluctuates due to heat or vibration, the inner dimension that defines the resonance frequency does not change, so that the change in the resonance frequency can be suppressed. Thereby, the impedance of the space seen from the high frequency circuit 4 built in the casing body 1 does not change, and the transmission characteristics of the built-in high frequency circuit 4 are stabilized.

By the way, in the case of the comparative example 1, the notch part 30 can be formed only in the maximum two sides among the four side wall parts 1a-1d of the casing main body 1. FIG. In the shield case 3 shown in FIG. 4, the dimension of the casing body in the x direction is x1, the dimension in the y direction is y1, and x1> y1, y1 <λ / 2, and x1> λ / 2. In such a case, the comparative example 1 is effective, and the notch 30 is formed in the side walls 1a and 1c of the four side walls 1a to 1d.

FIG. 9 shows a modification of the first comparative example . In the shield case 3 shown in FIG. 9, the cutout portion 30 is formed only on one side wall portion 1 c of the four side wall portions 1 a to 1 d constituting the casing body 1. Even in such a configuration, there is an effect that a change in the resonance frequency of the shield case 3 due to the fluctuation of the lid 2 can be suppressed as compared with the prior art.

Comparative Example 2
Next, Comparative Example 2 will be described with reference to FIG. Figure shield case 43 of Comparative Example 2 shown in 10, the lid 2 and similarly the lid 42 of Comparative Example 1, similarly to the casing body 1 of Comparative Example 1, two opposing sides of the sidewall portions of the four sides The casing main body 41 is formed with a notch portion 30 formed therein.

  However, the casing body 41 has a lower plate portion 41a in addition to the four side wall portions, and the dielectric substrate 5 is mounted on the lower plate portion 41a, and the high frequency circuit is mounted on the dielectric substrate 5. 4 is installed. The high frequency circuit 4 is electrically connected to the outside through the dielectric substrate 5 and the coaxial connector 45.

Even in the case of the shield case 43 having such a configuration, since the notch portions 30 are formed on two opposing sides of the four side wall portions in the casing body 41, the same effect as in the first comparative example can be obtained. Can do.

Form state of implementation.
Next, a description will be given of the shape condition of the present invention with reference to FIGS. 11 to 13. Figure 11 is a sectional view showing the shield case 50 in the form status of implementation, FIG. 12 is a plan view of the lid 52 in the shield case 50, the shield case in the state 13, which is mounted inclined lid 52 50 is shown.

Shielding case 50 in the form status of the implementation, and a casing body 51 of the box-shaped metal high-frequency circuit 4 therein is disposed on the dielectric substrate 5 is housed, a box-shaped metal lid member 2 which It is configured. The casing main body 51 has an upper surface portion and a lower surface portion that are open, and includes four side wall portions 51a to 51d. Further, unlike the first comparative example , the casing main body 51 does not have the notch portions 30 formed in the side wall portions 51a and 51c, and adopts the same configuration as the conventional casing 100 shown in FIG. doing.

In the shield case 50 in the form status of implementation, with the upper surface of the four side wall portions 51a~51d constituting the casing body 51, the position and the upper plate portion inside of the lid body 52 abuts, electrical insulation insulation A body 53 is provided. Oite the form status of implementation, although attaching the insulator 53 to the upper plate portion inside of the lid 52 (rear surface side of the upper plate portion), of the four side walls of the insulator 53 constituting the casing body 51 You may make it stick on the upper surface.

When the shield case 50 in the form status of the embodiment, as shown in FIG. 11, when the lid 52 is fitted to the normal to the casing body 51, a thin plate-like insulator 53 is formed on the side wall portion 51a~51d is The upper surfaces of the side wall portions 51a to 51d and the inner side of the upper plate portion of the lid 52 are not in electrical contact with each other, and are substantially equivalent to a space as in Comparative Example 1. Therefore, the dimension in the x direction that defines the resonance frequency is t, which is the inner dimension of the lid 52.

  On the other hand, as shown in FIG. 13, when the lid body 52 is disposed obliquely with respect to the casing body 51, only a gap is further formed between the insulator 53 and the side wall portions 51 a to 51 d. Therefore, the dimension in the x direction that defines the resonance frequency is t ′, which is the inner dimension of the lid 2, and there is no significant change between t ′ and t.

Thus, according to the shape condition of the embodiment, even while wearing the lid 52 normally, between the lid 52 and the casing main body 51 is interposed insulator 53, the cover 52 is a casing body 51, since the resonance frequency is determined by the inner dimension of the lid 52, and the inner dimension that defines the resonance frequency does not change even if the lid 52 fluctuates due to heat or vibration. Change can be suppressed. Thereby, the impedance of the space seen from the high frequency circuit 4 built in the casing main body 51 does not change, and the transmission characteristics of the built high frequency circuit 4 are stabilized. In addition, since the insulator 53 can be disposed in the two-dimensional direction of x and y, changes in the resonance frequency can be further suppressed.

In the form status of the above-described, has been to provide an insulating body 53 on all of the side wall portions 51a~51d of four sides of the casing body 51, of the side wall portions of the four sides as in Comparative Example 1 Insulators 53 may be provided on two opposite sides, and further, as shown in FIG. 9, an insulator 53 may be provided on one side. Further, the invention in the form status of implementation of interposing an insulator 53 between the casing body 51 and the lid 52 may be applied to the shield case 43 of Comparative Example 2 shown in earlier FIG. 10. In the above description, the insulator 53 having electrical insulation is provided between the lid 52 and the casing body 51. However, a dielectric having a dielectric constant close to air (for example, Teflon (registered trademark)). Even if a material: dielectric constant≈2 or the like is used as the insulator 53, the same effect as described above is obtained.

  As described above, the high-frequency device according to the present invention is useful for a high-frequency device including a casing body in which a high-frequency circuit is accommodated and a box-shaped lid that covers an upper surface opening of the casing body.

DESCRIPTION OF SYMBOLS 1 Casing main body 1a-1d Side wall part (casing main body)
2 Lid 2e Upper plate (lid)
2a-2d Side plate (lid)
DESCRIPTION OF SYMBOLS 3 Shield case 4 High frequency circuit 5 Dielectric board | substrate 6a Hole 6b Protrusion 7 Oscillator 8 Amplifier 9 Mixer 20 Microstrip line 30 Notch part 41 Casing main body 42 Cover body 43 Shield case 45 Coaxial connector 50 Shield case 51 Casing body 52 Cover body 53 Insulator 70 Grounding conductor 71 Ground via

Claims (4)

A metal casing body having a plurality of side walls , an opening formed on the upper surface, and a high-frequency circuit accommodated therein;
A box-shaped metal lid having a top plate portion covering the upper surface opening of the casing body, and a plurality of side plate portions covering the plurality of side wall portions of the casing body and contacting the plurality of side wall portions ; ,
With
High-frequency device is characterized in that the upper surface of the plurality of side walls of the casing body, a top plate portion inside of the lid is to provide an insulating body portion abuts. The high-frequency device according to claim 1, wherein the insulator is provided on an inner side of a top plate portion of the lid body or an upper surface of a side wall portion of the casing body.   The high-frequency device according to claim 1 or 2, wherein the casing body is mounted on a substrate with a lower surface opened, and the high-frequency circuit is mounted on the substrate.   The high frequency device according to claim 1, wherein the casing main body has a lower surface portion, and the high frequency circuit is mounted on a substrate placed on a lower surface of the casing main body.

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