JP2010096500A - High frequency module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in the prior art wherein, in a structure in which a dielectric substrate constituting a high frequency circuit is connected to a metal plate, two elements having each different thermal expansion coefficient are connected, so that there is a risk that the dielectric substrate constituting the high frequency circuit may be broken because of a temperature change or impact by vibration in a severe environment when being manufactured or loaded on a vehicle. <P>SOLUTION: A high frequency module includes: a high frequency circuit board wherein a high frequency circuit for transmitting and receiving a high frequency signal is formed on one surface of the dielectric substrate, and a first terminal for transmitting and receiving a high frequency signal is provided on the same surface; and a metal base wherein a second terminal connected to the first terminal is formed on one surface of a metal plate, and a third terminal connected to a high frequency antenna is formed on the other surface, and a waveguide connected to the second and third terminals and allowing the high frequency signal to pass is provided. The metal base is constituted by superposing one or more metal plates, and the metal base includes each protrusion on four sides. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a high-frequency module for millimeter wave radar.

  With the recent ITS (Intelligent Road Information System), millimeter wave radars have been developed as sensors for safe driving systems of automobiles. The millimeter wave is a radio wave with a frequency of 30 GHz to 300 GHz (wavelength in vacuum is about 1 mm to 10 mm), and the in-vehicle millimeter wave radar mainly uses 76 GHz to 77 GHz, and technical conditions are specified as a low power millimeter wave radar. Has been.

  As a technique similar to the millimeter wave radar, there is an infrared radar having a shorter wavelength, and the detection principle is the same. Infrared radars are less expensive than millimeter wave radars, but infrared radars are absorbed and diffused under weather conditions such as heavy rain and fog.

  On the other hand, the millimeter-wave radar is expected to help the driver's vision and help prevent collision accidents because the performance degradation due to the weather is very small and can detect the preceding vehicle running ahead. An inexpensive and highly reliable high-frequency module for an in-vehicle millimeter-wave radar is desired.

  As a high-frequency module suitable for this in-vehicle millimeter-wave radar, a high-frequency module in which a plurality of high-frequency components forming a high-frequency signal and transmitting / receiving circuits are mounted on a multilayer dielectric substrate and a metal plate having a waveguide are connected. A high-frequency module taking a form is disclosed (see Patent Document 1).

Japanese Patent No. 34285755

  According to Patent Document 1, the structure of the high-frequency module includes an antenna, a metal plate, a high-frequency circuit board, and a filter (see FIG. 8).

  In the structure in which the dielectric substrate constituting the high-frequency circuit is connected to the metal plate, two substrates having different linear expansion coefficients are connected, which is a severe condition during manufacturing or in-vehicle mounting. There is a problem that the dielectric substrate constituting the high-frequency circuit may be damaged by an impact caused by temperature change or vibration in the environment.

  In addition, when a large number of functional elements are provided in one housing, the radio wave energy radiated in the housing from a monolithic microwave integrated circuit (hereinafter referred to as MMIC) that constitutes the functional elements in the housing is There is a problem in that it easily propagates in the case and is coupled to a functional element in the same case, thereby causing various functional failures and degrading the quality of the high-frequency signal.

  Therefore, an object of the present invention is to provide an inexpensive and highly reliable high-frequency module having a highly productive mounting structure while maintaining sufficient mechanical strength even when mounted in a harsh environment such as an automobile. There is.

  In order to solve the above problems, one of the desirable embodiments of the present invention is as follows.

  In the high frequency module, a high frequency circuit for transmitting and receiving a high frequency signal is formed on one surface of a dielectric substrate, and one of a metal plate and a high frequency circuit substrate having a first terminal for transmitting and receiving a high frequency signal on the same surface. A second terminal connected to the first terminal is formed on the first surface, a third terminal connected to the high-frequency antenna is formed on the other surface, and the high-frequency signal is connected to the second and third terminals. A metal base having a waveguide through which the metal base passes, and the metal base is formed by stacking one or more metal plates, and has protruding portions on four sides of the metal base.

  According to the present invention, it is possible to provide an inexpensive and highly reliable high-frequency module having a highly productive mounting structure while maintaining sufficient mechanical strength even when mounted in a harsh environment such as an automobile. it can.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a diagram showing a system including a vehicle equipped with a millimeter wave radar.

  The millimeter wave radar 2 is attached to the head of the own vehicle 1 and the radio wave reflected from the preceding vehicle 3 is received by emitting the millimeter wave from the front surface of the own vehicle 1, and the frequency difference caused by the propagation time and the Doppler effect is received. Based on this, the position of the preceding vehicle 3 and the relative speed with the own vehicle 1 are measured.

  FIG. 2 is a sectional view of the millimeter wave radar 2.

  The inside of the millimeter wave radar 2 is roughly divided into three components. The high-frequency module 13 includes a portion that handles a high-frequency signal, a portion that processes an intermediate frequency, and a power supply unit.

  The configuration of the high-frequency module 13 includes a high-frequency antenna 12 that receives a high-frequency signal and receives a reflected wave in a planar shape, a thin metal plate punched out by pressing, and a press-molded metal to form a periodic filter. A power supply circuit board 8 that includes a metal base 11 that forms a waveguide for transmitting and receiving a high-frequency signal, and a high-frequency circuit board 10 in which a high-frequency circuit is formed on a dielectric substrate, and generates a power supply for use in the millimeter wave radar 2. The signal processing board 9 for processing a signal obtained by frequency-converting a high-frequency signal into an intermediate frequency signal constitutes the entire configuration of the millimeter wave radar 2.

  The external parts include a connector 4, which is an interface with the outside, a rear cover 5 in which the power circuit board 8 and the signal processing board 9 are accommodated, a housing 6 in which the high frequency circuit board 10 and the metal base 11 are accommodated, and a front surface which protects the antenna surface of the high frequency antenna 12. It consists of a cover 7.

  The reflected signal received by the high-frequency antenna 12 is frequency-converted to an intermediate frequency by the high-frequency circuit board 10, AD-converted by the signal processing board 9, frequency analysis is performed by the DSP circuit, and distance, relative speed, and angle information are calculated. To calculate the target position. The calculation result is output to the control computer on the vehicle side via the connector 4 which is an interface with the outside.

  FIG. 3 shows a cross-sectional view of the high-frequency module 13.

  The high-frequency circuit board 10 having a transmission / reception circuit and mounting a plurality of high-frequency IC chips of various functions used in the high-frequency module 13 will be described.

  The high-frequency circuit board 10 is mounted with a high-frequency IC chip having various functions on a laminated dielectric substrate. The high-frequency IC chip uses an MMIC, and includes a transmitter, a power amplifier, a signal mixer, and the like. A high-frequency transmission line such as a microstrip line, a triplate line, or a coplanar line for connecting each high-frequency IC chip is provided. On the high-frequency circuit board 10, a cavity matching the thickness of the IC chip is formed on one surface, and a high-frequency IC chip composed of a microstrip line with the back-side bonding surface being GND is mounted therein. Each high-frequency IC chip is arranged so as to be able to achieve isolation that sufficiently satisfies the required performance.

  Also, each high frequency IC chip is connected by a metal wire or a metal ribbon if it is placed in the same cavity, and if it is placed in a different cavity due to the necessity of isolation, adjacent cavities Further, the high frequency IC chips arranged respectively are connected by a high frequency transmission line.

  A bonding agent such as a conductive Ag paste or solder paste is used for mounting the IC chip in order to electrically connect the back surface, which is the GND of the high frequency IC chip, and the GND of the dielectric substrate. The high frequency circuit board 10 mounted as described above is mounted on the surface of the metal base window 21 provided on the metal base 11 with a bonding material such as conductive Ag paste or solder paste applied by a dispenser or the like. The connection with 12 is joined by a fastening member such as a screw.

  Electrically, a high-frequency signal output from the output circuit of the high-frequency circuit board 10 in the high-frequency module passes through a waveguide 14 having a waveguide structure provided on the metal base 11 and outputs a high-frequency signal from the high-frequency antenna 12. To do. On the other hand, a high-frequency signal reflected from an object is input from the high-frequency antenna 12, passes through a waveguide 14 having a waveguide structure provided on the metal base 11, and is input to the receiving circuit of the high-frequency circuit board 10.

  Next, an embodiment of the high-frequency module will be described in detail with reference to FIGS. FIG. 4 is a top view of the metal base 11 before the high-frequency circuit board 10 is mounted.

  The high-frequency circuit board 10 is mounted on the surface of the metal base window 21 on which the high-frequency circuit board 10 provided on the metal base 11 is applied by applying a bonding material such as conductive Ag paste or solder paste with a dispenser or the like. Thereby, the position of the waveguide 14 which is the transmission / reception terminal of the high-frequency circuit board 10 and the transmission / reception terminal of the metal base 11 is accurately matched and connected.

  At that time, in the case of a combination such as the high frequency circuit board 10 which is a multilayer dielectric substrate and the metal base 11, ones having different linear expansion coefficients are connected, and the high frequency circuit board 10 is expanded or contracted due to a temperature change. In order to prevent damage, slits 17-b are provided on the four sides around the metal base window portion 21 where the high-frequency circuit board 10 is mounted so as to cope with thermal stress. The slit 17-a relaxes mechanical stress caused by vibration such as when the screw hole 16 is used for fixing or when mounted on the vehicle.

  In particular, when ceramic is used as the material of the high-frequency circuit board 10, there is a ceramic characteristic that the hardness is high but it is easy to break. Therefore, the slits on the two sides of the screw hole 16 and the four sides of the high-frequency circuit board 10 are effective. As a result, it is possible to provide a high-frequency module with improved reliability in the millimeter wave radar 2 to be mounted on an automobile that is subjected to particularly severe stress both in terms of temperature and mechanical properties.

  The metal base 11 located in the middle in the structure for connecting the units that transmit and receive the high-frequency signal needs to process the waveguide 14 that is the path of the high-frequency signal passing therethrough.

  As a function of the metal base 11, an effect of protecting from damage is also expected, so that the rigidity is increased in the direction of increasing the plate thickness. However, the thick metal plate has a very high aspect ratio required for high-frequency signals. Narrow diameter drilling is required. The high-frequency signal waveguide 14 has a rectangular waveguide shape and an extremely high aspect ratio, and it is very difficult to perform fine processing with such a high aspect ratio.

  There is a manufacturing problem that press processing is not possible because the processing cost is low. For example, there are restrictions in the thickness direction such as photo etching, and the processing cost is high due to laser processing, etc. It was necessary to adopt.

  As a method of avoiding them, by making a very thin diameter hole necessary for the waveguide 14 through which a high-frequency signal passes through a thin metal plate by inexpensive press processing, the aspect ratio is reduced and the press processing is inexpensive. Drilling is possible. By superimposing the holes after carrying out the hole machining, there is an advantage that the cost problem at the time of machining can be avoided and the production can be made at a low cost.

  Furthermore, in this case, since the metal base 11 has a laminated structure of thin metal plates, there is no restriction in the plate thickness direction, and the degree of freedom in design is improved.

  The metal base 11 according to this embodiment forms a waveguide having an arbitrary line length by superimposing the waveguides 14 made of thin metal plates in the waveguide portion through which the high frequency signal passes. Alignment is required. At that time, the projections 18 are provided on the four sides of the rectangular hole of the waveguide portion and the four sides of the thin metal plate, and the projections and depressions are overlapped when the metal base 11 is manufactured. Superposition at positions is possible, and the rectangular shape of the waveguide 14 is also maintained.

  Moreover, the reliability of the high frequency signal of the waveguide 14 is improved by increasing the adhesion between the thin metal plates by combining the metal plates having convex and concave portions. The unevenness of the projecting process is also reduced by performing the press process.

  Next, the metal base 11 of the high-frequency module will be described with reference to FIGS.

  FIG. 4 is a top view of a single metal base 11 using one or more metal plates, which is a joint surface with the component mounting surface of the high-frequency circuit board 10.

  FIG. 5 shows a metal plate positioned at the lowermost part of the metal base 11 in FIG. 4, and the periodic filter 20 for upper surface provided with periodic protrusions is located at the upper part when viewed from the component mounting surface of the high-frequency circuit board 10. To position.

  FIG. 6 shows a side surface periodic filter 19 which is arranged at a position overlapping the metal plate of FIG. 5 located at the lowermost part of the metal base 11 and periodically provided with protrusions. Located on the side when viewed from the side.

  FIG. 7 shows a metal plate positioned at the uppermost portion of the metal base 11 in FIG. 4, and the high frequency circuit board 10 is mounted on the metal base window portion 21 for placing the high frequency circuit board 10 provided on the metal base 11. Thereby, the position of the waveguide 14 which is the transmission / reception terminal of the high-frequency circuit board 10 and the transmission / reception terminal of the metal base 11 is accurately matched and connected.

  In addition, the position of the periodic protrusions of the transmission / reception functional elements mounted on the high-frequency circuit board 10 and the periodic filter 20 for the upper surface and the periodic filter 19 for the side surface located on the upper surface and the side surface are also accurate. It is arranged almost on the whole surface in dimension.

  In addition to the metal surface on which the transmitter / receiver circuit is mounted, which is covered with a metal with periodic irregularities configured in this way, the wave impedance is periodically applied to the high frequency waves that are about to propagate through the space in the housing between them. A varied filter structure is formed and exhibits characteristics having alternating propagation and non-propagation frequency bands as a function of frequency.

  Therefore, by designing the metal base 11 having a filter function so that the operating frequency band of the transmission / reception circuit falls within the non-propagation frequency band, unnecessary radiation from the transmission side of the transmission / reception circuit to the inside of the housing reaches the reception side. Can be prevented, and interference between transmission and reception can be reduced.

  In addition, once the energy is radiated unnecessarily in the housing, it tends to be radiated unnecessarily outside the housing using the housing as an antenna, or conversely, it is easily affected by radio wave energy from the outside of the housing. Magnetic Interference) and EMC (Electro Magnetic Compliance) problems are reduced.

  The shape in Example 3 is the same as in Example 2, and the second shape is a molded body obtained by shaping a resin material whose surface is coated with a metal material.

  This has the merit that it can be manufactured at low cost because it is made of a resin material, compared with the case where the same shape is made of metal. Electrically, it is possible to obtain the same performance as when made of metal by coating the surface of the resin with metal.

  According to the above embodiment, the problem of interference due to unnecessary radiated radio wave energy, EMI, and EMC can be greatly reduced by simply adding a simple periodic structure to a part of the high-frequency housing structure. This makes it possible to realize the multifunctional high-frequency module at low cost without degrading the overall characteristics. Furthermore, the filter characteristics due to the periodic structure can almost always be designed so that it does not depend on reliable metal contact. Therefore, the mass production variation and secular change of the housing structure for a high-frequency module such as a millimeter wave radar can be reduced. Can be reduced.

The figure which shows the system containing the vehicle carrying a millimeter wave radar. Sectional drawing of a millimeter wave radar. Sectional drawing of a high frequency module. The top view of superposition of a metal base. The top view of the metal base single-piece | unit which has a waveguide and the periodic filter of an upper surface. The top view of the metal base single-piece | unit which has a waveguide and the periodic filter of a side surface. The figure which shows the metal plate located in the uppermost part of a metal base. Sectional drawing of the conventional high frequency module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Own vehicle 2 Millimeter wave radar 3 Leading vehicle 4 Connector 5 Rear cover 6 Housing 7 Front cover 8 Power supply circuit board 9 Signal processing board 10 High frequency circuit board 11 Metal base 12 High frequency antenna
13 High Frequency Module 14 Waveguide 15 Filter 16 Screw Holes 17-a, 17-b Slit 18 Projection 19 Side Periodic Filter 20 Top Surface Periodic Filter 21 Metal Base Window

Claims (4)

Forming a high-frequency circuit for transmitting and receiving a high-frequency signal on one surface of the dielectric substrate, and having a first terminal for transmitting and receiving a high-frequency signal on the same surface;
A second terminal connected to the first terminal is formed on one surface of the metal plate, and a third terminal connected to the high-frequency antenna is formed on the other surface, and the second and third terminals A metal base having a waveguide connected to a terminal and allowing a high-frequency signal to pass through,
The metal base is a high-frequency module configured by stacking one or more metal plates and having protrusions on four sides of the metal base.   The metal base has rectangular or oval elongated holes at the four sides and four corners of the mounting position of the waveguide and the high-frequency circuit board in the same metal plate, and at least a part thereof is provided with protrusions periodically. The high-frequency module according to claim 1, having a periodic structure.   The high-frequency module according to claim 2, wherein the metal base is a molded body obtained by shaping a resin material whose surface is coated with a metal material.   The high frequency module according to claim 1, wherein the metal base has a filter function.

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