JP4498934B2 - High frequency device - Google Patents

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 the 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 in which an opening is formed on an upper surface and a high-frequency circuit is accommodated, and the upper surface opening of the casing body. A box-shaped metal lid that covers the casing body, and the upper surface of the side wall portion of the side wall portion of the casing body that is composed of a plurality of sides is opposed to the upper plate of the lid body. In order not to contact the inside of the part, a notch is formed over the entire side or the two opposite sides.

  According to the present invention, with respect to one side of the side walls formed of a plurality of sides of the casing main body or two side walls facing each other, the upper surface of the side wall is not in contact with the inside of the upper plate of the lid. Since notches are formed over one side or the entire two opposite sides, when one side or two opposite sides of these side wall portions are attached to the casing body, the upper plate portion of the lid body Since the inner side is not contacted even in a normal state, the resonance frequency is determined by the inner dimensions of the lid of the lid. Therefore, even when the attachment state of the lid to the casing body is changed to an abnormal state such as an inclined state due to heat or vibration, the internal dimensions of the case that defines the resonance frequency are not greatly changed as in the conventional case. .

  According to the present invention, with respect to one side of the side walls formed of a plurality of sides of the casing main body or two side walls facing each other, the upper surface of the side wall is not in contact with the inside of the upper plate of the lid. Since the notch is formed over one side or the entire two opposite sides, the inner dimensions of the case that define the resonance frequency in the case even if the mounting state of the lid to the casing body changes due to heat, vibration, etc. As a result, it hardly changes, and even when the mounting state of the lid changes, the influence on the resonance frequency can be suppressed. Thereby, in this invention, since the impedance of the space seen from the high frequency circuit incorporated in the case does not change, there exists an effect that the transmission characteristic of the built-in high frequency circuit is stabilized.

  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 casing 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.

Embodiment 1 FIG.
A first embodiment 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 the first embodiment of the shield case 3 in which the above-described high-frequency circuits such as the oscillator 7 and the amplifier 8 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 Embodiment 1 is demonstrated. In the first embodiment, of the two opposing side wall portions 1a and 1c among the plurality of side wall portions 1a to 1d, the upper surfaces of the side wall portions 1a and 1c are the upper plate portion 2e of the lid body 2. A cutout portion 30 is formed on the upper side of the side wall portions 1a and 1c so as not to contact the inner side (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 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 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 the first embodiment, 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 portion. Since a space is formed above 1 a and 1 c, 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 the first embodiment, 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.

  Thus, according to the first embodiment, even when the lid 2 is normally mounted, the upper plate portion 2e of the lid 2 is not in contact with the upper surface of the casing body 1, so that the resonance frequency is within the lid 2. Since the inner dimension that defines the resonance frequency does not change even when the lid 2 fluctuates due to heat or vibration, changes 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 Embodiment 1, the notch part 30 can be formed only in the maximum two sides of the four side wall parts 1a to 1d of the casing body 1. 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 invention of the first embodiment 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 embodiment. 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.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. The shield case 43 of the second embodiment shown in FIG. 10 is the same as the cover 42 of the cover 2 of the first embodiment and the opposite of the side walls of the four sides, like the casing body 1 of the first embodiment. The casing main body 41 is formed with a notch 30 formed on two sides.

  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, the cutout portions 30 are formed on two opposing sides of the four side wall portions of the casing body 41, so that the same effect as in the first embodiment is obtained. be able to.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIGS. 11 is a cross-sectional view showing the shield case 50 of the third embodiment, FIG. 12 is a plan view of the lid body 52 in the shield case 50, and FIG. 13 is a shield case with the lid body 52 being tilted. 50 is shown.

  The shield case 50 according to the third embodiment includes a box-shaped metal casing body 51 that is disposed on the dielectric substrate 5 and accommodates the high-frequency circuit 4 therein, and the box-shaped metal lid body 2. 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 embodiment, the casing main body 51 has the same configuration as the conventional casing 100 shown in FIG. 14 without the notch 30 formed in the side walls 51a and 51c. Adopted.

  In the shield case 50 of the third embodiment, insulation having electrical insulation is provided at a position where the upper surfaces of the four side wall portions 51a to 51d constituting the casing body 51 and the inner side of the upper plate portion of the lid body 52 abut. A body 53 is provided. In the third embodiment, the insulator 53 is attached to the inside of the upper plate portion of the lid body 52 (the back side of the upper plate portion), but the insulator 53 is placed on the upper surfaces of the four side wall portions constituting the casing main body 51. You may make it stick.

  In the case of the shield case 50 of the third embodiment, as shown in FIG. 11, when the lid body 52 is normally fitted into the casing body 51, a thin flat insulator 53 is formed on the side wall portions 51a to 51d. 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 the space as in the first embodiment is substantially formed. Since they are equivalent, 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 third embodiment, the insulator 53 is interposed between the lid body 52 and the casing body 51 even when the lid body 52 is normally mounted, and the lid body 52 is the 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 third embodiment, the insulator 53 is provided on all the four side walls 51a to 51d of the casing body 51. However, as in the first embodiment, the insulators 53 are not provided. 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 of the third embodiment in which the insulator 53 is interposed between the casing main body 51 and the lid 52 may be applied to the shield case 43 of the second embodiment shown in FIG. 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.

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. 1 is a perspective view showing a high-frequency device according to a first embodiment of the present invention. 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. 6 is a graph showing simulation results showing changes in resonance frequency when the mounting state of the lid is variously changed in the shield case of the first embodiment. It is a perspective view which shows the structure of the shield case for creating the simulation result of FIG. FIG. 6 is a perspective view showing a modification of the high-frequency device according to the first embodiment. FIG. 6 is a cross-sectional view showing a high-frequency device according to a second embodiment. FIG. 6 is a cross-sectional view showing a high-frequency device according to a third embodiment. 6 is a plan view showing a high-frequency device according to a third embodiment. FIG. It is sectional drawing which shows the high frequency device of Embodiment 3 at the time of lid body abnormal mounting | 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.

Explanation of symbols

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 (6)

A rectangular metal casing body having four side walls, an opening formed on the upper surface, and a high-frequency circuit accommodated therein;
A rectangular box-shaped metal lid having a top plate covering the upper surface opening of the casing body and four side plates covering the four side walls of the casing body;
With
For two opposing side wall portions of the four side wall portions of the casing main body, a notch portion extending from one end to the other end of the side wall portion so that the upper surface of the side wall portion does not contact the top plate of the lid body is provided. Formed in the upper part of the side wall,
The top plate of the lid is not brought into contact with the upper surface of the two side wall portions having a notch, wherein the two side wall portions other opposing having no notch was into contact A high-frequency device characterized by that. A rectangular metal casing body having four side walls, an opening formed on the upper surface, and a high-frequency circuit accommodated therein;
A rectangular box-shaped metal lid having a top plate covering the upper surface opening of the casing body and four side plates covering the four side walls of the casing body;
With
About one side wall part of the four side wall parts of the casing main body, a notch part extending from one end to the other end of the side wall part so that the upper surface of the side wall part does not come into contact with the top plate of the lid body. Formed in the upper part of
The top plate of the lid is not brought into contact with the upper surface of one side wall portion having the notch portion, wherein the other three side wall portions having no notch was into contact A featured high-frequency device.   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 plate portion, and the high-frequency circuit is mounted on a substrate placed on the lower plate of the casing main body.   The high frequency device according to any one of claims 1 to 4, wherein a side wall portion of the casing body is bent so that an elastic force is applied. A plurality of protrusions are respectively formed on the two side wall portions having the cutout portion of the casing body,
The high frequency device according to claim 1, wherein a plurality of holes into which the protrusions are fitted are formed in two opposing side plates of the lid.

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