JP2006295670A - Rf probe substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decrease a problem of mounting a short circuit plate cap in an existing structure, and to prevent impairment of convention efficiency. <P>SOLUTION: A ground 13 is formed on a lower surface side of a first layer alumina substrate 11. A waveguide mouth 14 is formed on both alumina substrates 11 and 12 almost concentrically to an earth pattern comprised of circular through holes. The waveguide tube antenna is mounted from a lower surface side of the first alumina substrate 11. A microstrip line 16 is mounted between both of the alumina substrates 11 and 12. The short-circuit plate cap 15 is fixed on an upper surface of the second layer alumina substrate 12 in accordance with a cap adhering pattern. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an RF probe substrate that couples a communication module circuit and an antenna, and more particularly to an RF probe substrate that couples a high-frequency signal circuit and a waveguide antenna in a microwave or millimeter wave transceiver.

  More particularly, the present invention relates to an RF probe substrate that efficiently converts a microstrip line, which is an input / output of a high-frequency element, to a waveguide line, and in particular, mounting of a short-circuit plate cap possessed by an existing structure. The present invention relates to an RF probe substrate that minimizes the above problem and does not impair the conversion efficiency.

  2. Description of the Related Art In recent years, with the development of information transmission technology including wireless LAN (Local Area Network), development of semiconductor elements that operate in the millimeter wave band or microwave band, that is, high-frequency semiconductor element technology, has become active.

  In this type of circuit mounting technology, it is positioned as an important elemental technology to connect a circuit board or package containing a high-frequency element and a waveguide provided in an external electric circuit with a simple and small structure. It has been. In particular, how to connect an external electric circuit in which a waveguide with the smallest transmission loss is formed and a circuit board or package on which a high-frequency element is mounted is a big problem.

  In a microwave or millimeter wave transmission / reception apparatus, the coupling between a module circuit and an antenna is an important matter related to the efficiency and SN ratio of the entire apparatus. This is because the efficient coupling allows the modules to maximize their capabilities and be linked to a desired communication distance and band, and also has an effect of reducing power consumption.

  Usually, since input / output of the high-frequency element is formed by a microstrip line, transmission / reception of a high-frequency signal between the high-frequency signal circuit module and the waveguide antenna requires conversion to a waveguide line.

  FIG. 6 shows a configuration example (conventional example) of an RF probe substrate for transmitting and receiving a high-frequency signal between the high-frequency signal circuit and the waveguide antenna. FIG. 7 shows the cross-sectional configuration. On a dielectric substrate made of alumina or the like, for example, a large number of through holes having a diameter of 200 μm are formed on a circular ring having a diameter of 3.2 mm, and a ground is formed on the lower surface side of the substrate. In addition, a metal short-circuit plate cap is formed on the top surface of the substrate in order to block external radio waves and reflect the radio waves generated inside to guide the inside of the waveguide.・ It can be attached according to the pattern (ground pattern).

  However, in the illustrated configuration, the microstrip line penetrates from the outside to the inside of the ground pattern, so that a portion where the microstrip line and the short-circuit plate cap intersect is generated. For this reason, a cutting portion for separating the pattern is provided at a location where the microstrip line and the through-hole pattern intersect. In addition, a part of the short-circuit plate cap is processed to provide a notch for preventing contact with the microstrip line, and this notch is annular when fixed on an alumina substrate with an adhesive such as Ag paste. It must be precisely aligned with the ground pattern cut.

  Such an operation of attaching the short-circuit plate cap is very inefficient. When confirming with the eyes, the operator should constantly monitor the position information in the lateral direction, or engrave a mark on the cap surface and match the mark reference, and finally confirm from the lateral direction. There is a need for. In any case, the workability is remarkably poor and requires skill.

  For example, a circuit module having a transition portion from a waveguide to a microstrip in an integrated circuit package that can be easily manufactured (see, for example, Patent Document 1) or a wiring board surface such as a high-frequency package. A proposal has been made on a wiring board that provides a connection structure between a waveguide board and a wiring board that can be connected with low signal loss and low reflection between the formed signal transmission line and the waveguide ( For example, see Patent Document 2).

  FIG. 8 illustrates a configuration example of these RF probe substrates. FIG. 9 shows the cross-sectional configuration. As in FIG. 6, the dielectric substrate has a large number of through-holes formed on the ring, and the microstrip line penetrates from the outside to the inside of the ground pattern. The other end of the microstrip line is connected to an input / output terminal of an MMIC (monolithic millimeter wave integrated circuit) on the same substrate through an Au wire or the like. The short-circuit plate has a cap structure that covers the entire module, but has a wide opening at the portion that intersects the microstrip line, so the notch of the short-circuit plate cap as shown in FIG. This frees you from the task of precise alignment with the pattern cut.

  As shown in the figure, the cap is arranged on the microstrip so as to function as a short-circuit plate. In this case, it is difficult to arrange the cap at an appropriate height (H) due to restrictions from the whole. The process of cap deformation processing is inevitably increased. In addition, since the cap opening is wide, the injected RF power leaks from the RF probe into the module, and the transmission efficiency deteriorates. Further, mutual radio wave interference in the lateral direction can be considered for each block forming the module. For this reason, the present inventors think that it cannot be said that it is a preferable mounting method.

JP-A-11-243307 JP 2002-185222 A

  An object of the present invention is to provide an excellent RF probe substrate capable of suitably coupling a high-frequency signal circuit and a waveguide antenna in a microwave or millimeter-wave transceiver device.

  It is a further object of the present invention to provide an excellent RF probe substrate capable of efficiently performing conversion from a microstrip line, which is an input / output of a high-frequency element, to a waveguide line.

  A further object of the present invention is to provide an excellent RF probe substrate capable of minimizing the mounting problem of the short-circuit plate cap of the existing structure and not impairing the conversion efficiency.

The present invention has been made in consideration of the above problems, and is an RF probe substrate that performs conversion from a microstrip line to a waveguide line,
A substrate body comprising a first dielectric layer and a second dielectric layer;
A ground formed on a lower surface of the first dielectric layer and having a waveguide opening;
A cap bonding pattern formed along the outer periphery of the waveguide opening on the upper surface of the second dielectric layer;
An annular ground pattern comprising a plurality of through-holes annularly formed on the cap bonding pattern;
A microstrip line formed between the first dielectric layer and the second dielectric layer and having one end inserted into the waveguide;
A short-circuit plate cap attached to the cap adhesive pattern;
An RF probe substrate characterized by comprising:

  In a microwave or millimeter wave transmission / reception apparatus, the coupling between a module circuit and an antenna is an important matter related to the efficiency and SN ratio of the entire apparatus. This is because the coupling is efficiently performed, so that the module capability can be maximized and linked to a desired communication distance and band, and power consumption can be reduced.

  The conventional coupling method is directly converted to a waveguide antenna because the input and output of the high-frequency signal circuit module are wired in a microstrip line system. In this case, there is a problem that the notch portion of the short-circuit plate cap must be accurately positioned at the location where the microstrip line and the short-circuit plate cap intersect (see FIG. 6). Alternatively, to avoid contact at the intersection of the microstrip line and the annular ground pattern, a portion of the annular pattern is cut and a space is provided to insert the microstrip line into the waveguide. However (see FIG. 8), if the opening of the short-circuit plate cap is widened on the microstrip, leakage of RF power injected into the RF probe becomes large and transmission efficiency deteriorates.

  Therefore, in the present invention, when the high-frequency signal circuit module and the waveguide antenna are coupled, the RF probe has a multi-layer substrate structure, and the mounting of the short-circuit plate cap installed on the RF probe is facilitated. In addition, the efficiency of microstrip-waveguide conversion is improved, and radio wave interference in the module is minimized.

  The RF probe substrate according to the present invention is composed of a multilayer substrate including a first dielectric layer and a second dielectric layer. A ground having a waveguide opening is formed on the lower surface of the first dielectric layer, and a cap bonding pattern is formed on the upper surface of the second dielectric layer along the outer periphery of the waveguide opening. A large number of through-holes are formed in an annular shape on the cap bonding pattern to form an annular ground pattern. One end of the microstrip line is inserted in the waveguide between the first dielectric layer and the second dielectric layer.

  According to such an RF probe substrate configuration, the annular ground pattern and the RF probe pattern can be formed independently, and the microstrip line and the short-circuit plate cap do not cross each other. Therefore, it is no longer necessary to cut the annular ground pattern at the intersection with the microstrip line, and the short-circuit plate cap does not require a notch for avoiding contact with the microstrip line that has been provided in the past, thus simplifying the structure. can do.

  The waveguide coupling hole of the module / package is kept airtight even by the conventional RF probe substrate (see FIG. 6), but the thickness of the member is thin and the mechanical strength is weak, so there is a problem in terms of reliability. is there. On the other hand, according to the RF probe substrate according to the present invention, the thickness of the member is doubled from a single layer to a double layer alumina substrate, so that the mechanical strength is increased and the reliability is improved.

  Further, according to the RF probe substrate according to the present invention, since the microstrip line and the cap are not in direct contact with each other, workability during mounting such as pattern alignment is greatly improved.

  Further, according to the RF probe substrate according to the present invention, since there is no gap between the surface layer alumina substrate and the short-circuit plate cap over the entire circumference, conventionally, the radio wave leakage generated at the notch portion of the short-circuit plate cap is improved, and the micro wave The conversion efficiency between the strip line and the waveguide is improved.

  In addition, according to the RF probe substrate of the present invention, it is possible to completely shield the other functional blocks in the module spatially, so that unstable operation of the circuit module such as abnormal oscillation can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the outstanding RF probe board | substrate which can perform efficiently conversion from the microstrip line which is the input / output of a high frequency element to a waveguide line can be provided.

  In addition, according to the present invention, it is possible to provide an excellent RF probe substrate that can minimize the mounting problem of the short-circuit plate cap of the existing structure and can maintain the conversion efficiency. .

  According to the structure of the RF probe substrate according to the present invention, since the peripheral portion of a simple circular cap is simply adhered to the annular through-hole connection pattern of the RF probe, it is possible to work by visually observing the upper surface under a microscope. Because it can, it does not require skill and is a simple task.

  As a result of simplifying the work in this way, there is an effect that multi-purpose work can be achieved and the number of work can be shortened, processing man-hours can be shortened and processing costs can be reduced, and automation can be performed with an inexpensive apparatus. .

  Further, according to the structure of the RF probe substrate according to the present invention, since the RF probe is completely shielded by the metal cap, the high frequency power to the RF probe is efficiently lost to the adjacent block such as the MMIC or the waveguide antenna. Well communicated.

  In addition, according to the structure of the RF probe substrate according to the present invention, the RF probe is completely shielded by the metal cap, so that it is independent in the module, has no radio wave interference with each functional block of the module, and does not cause abnormal oscillation. The phenomenon does not occur and stable operation can be expected.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In a microwave or millimeter wave transmission / reception apparatus, the coupling between a module circuit and an antenna is an important matter related to the efficiency and SN ratio of the entire apparatus. This is because the coupling is efficiently performed to maximize the capability of the module and connect it to a desired communication distance and band, and also has an effect of reducing power consumption.

  In the conventional coupling method, the high-frequency signal circuit module is directly converted into a waveguide antenna because the input and output of the high-frequency signal circuit module are wired in a microstrip line system (for example, FIG. 6). checking). On the other hand, in the present invention, when the high-frequency signal circuit module and the waveguide antenna are coupled, the structure of the RF probe is multi-layered, and the short-circuit plate cap installed on the RF probe is easily mounted. In addition, the efficiency of microstrip-waveguide conversion is improved, and radio wave interference in the module is minimized.

  FIG. 1 shows a structure (top view) of an RF probe substrate 10 according to an embodiment of the present invention. FIG. 2 shows the cross-sectional structure.

  As shown in FIG. 1, on a dielectric substrate made of alumina or the like, a large number of through-holes with a diameter of φ200 μm are disposed on a ring with a diameter of φ3.2 mm, for example, at intervals of 1/4 or less of the signal wavelength λ. Has been.

  As shown in FIG. 2, the dielectric substrate has a laminated structure of a first layer alumina substrate 11 and a second layer alumina substrate 12, and each through hole penetrates both the alumina substrates 11 to 12 from the upper surface to the lower surface. It is inserted.

  A ground 13 is formed on the lower surface side of the first layer alumina substrate 11. Further, the first layer alumina substrate 11 and the second layer alumina substrate 12 are formed with the ground pattern 18 composed of the above-described through holes arranged in a ring shape, and a waveguide opening 14 formed substantially concentrically therewith, A waveguide antenna (not shown) is attached from the lower surface side of the first layer alumina substrate 11.

  On the upper surface of the second layer alumina substrate 12, the short-circuit plate cap 15 is aligned with the cap adhesive pattern 17 embedded in the ground pattern 18 and fixed with an adhesive such as an Ag paste. The microstrip line 16 runs between the first layer alumina substrate 11 and the second layer alumina substrate 12 from the outside to the inside of the ground pattern. The short plate cap 15 is set to an appropriate height H with respect to the microstrip line 16. A wire bonding pad is formed at the other end of the microstrip line 16 and is used for connection with an input / output terminal of a neighboring IC chip (MMIC).

  Since the alumina substrate has a multi-layer structure as described above, the annular ground pattern 18 and the RF probe pattern can be formed independently. Therefore, it is necessary to provide a cutting portion for separating the pattern in the ground pattern 18. There is no. Further, since the short-circuit plate cap 15 and the microstrip line 16 do not come into contact with each other, a notch is not necessary, and there is no problem of alignment between the notch and the cut portion of the annular ground pattern 18.

  Since the conventional short-circuit plate cap needs to avoid contact with the strip line, it has a structure having a notch at the corresponding portion of the annular ground pattern cutting portion (see FIG. 6). For this reason, the manufacturing cost of the cap is also required, and it is necessary to accurately match the notch portion of the cap with the adhesive pattern in the assembly mounting process. This work needs to be placed at the center of the pattern while rotating the cap, and since an adhesive such as Ag paste is used, the paste does not protrude from the pattern while taking a three-dimensional view under a microscope. It was necessary to do it and it was very skillful. On the other hand, in the RF probe substrate shown in FIG. 1, the annular through hole in which the cap adhesion pattern 17 is embedded is continuously connected to the second layer alumina substrate 12 as the surface layer. Therefore, when the ground pattern 18 and the short-circuit plate cap 15 are bonded, it is not necessary to consider the direction of rotation, so that the working efficiency is remarkably improved.

  Here, the transmission operation will be considered with reference to FIG.

  The RF power injected into the RF probe reaches the tip of the microstrip line 16 through gaps between a plurality of through holes formed in an annular shape, and then is dispersedly radiated in the vertical direction. Of these, the RF power directed upward is reflected by the metal short-circuit plate cap 15 set to an appropriate height H, and all of the RF power is directed downward and merges with the original lower portion to open the opening 14 of the waveguide. To reach.

  The interval between the annular through holes in the ceramic is designed to be ¼ or less of the signal wavelength λ to be used, and the waveguide wall is almost perfect. For this reason, the RF power reflected by the short-circuit plate cap 15 from above reaches the waveguide opening surface 14 efficiently.

  In the conventional substrate structure shown in FIGS. 6 and 8, when the injected RF power is directed upward, leakage occurs from the notch portion of the cap each time it is reflected back, which causes a decrease in efficiency. End up. In addition, this leakage power may cause abnormal oscillation and the like by interacting with the MMIC circuit on the supply side.

  On the other hand, the structure of the RF probe substrate shown in FIGS. 1 and 2 excludes the disadvantages of the conventional structure, including modifications described later, and ensures a stable transmission path between the RF probe and the waveguide. can do.

  FIG. 3 shows a modification (top view) of the RF probe substrate 10 shown in FIG. FIG. 4 shows a cross-sectional structure thereof.

  In the substrate configuration example shown in FIG. 1, the terminal end side of the microstrip line 16 is exposed to the outside from the second layer alumina substrate 12, and the wire bonding pattern at the terminal end of the microstrip line 16 is used. It is structured to be taken out from the first layer alumina substrate 11. In contrast, in the RF probe substrate shown in FIGS. 3 and 4, the second layer alumina substrate 12 covers the entire microstrip line 16.

  In this modified example, as shown in FIG. 4, a line coupling through hole 19 is formed in a portion corresponding to the terminal portion of the microstrip line 16, and this through hole 19 is made conductive so that the microstrip line 16 is formed. -The end of the line 16 can be taken out and wire bonding can be performed. According to the latter configuration, it is possible to prevent the bonding wire for connecting to a neighboring IC chip from becoming unnecessarily long by selecting the structure of the preceding MMIC so as not to generate a level difference as much as possible. .

  FIG. 5 shows a structural cross section of a module on which the RF probe shown in FIGS. 3 and 4 is mounted.

  In the illustrated module package, a hole having a size corresponding to the waveguide diameter of the RF probe is provided. At the time of mounting, the centers of the cap hole, RF probe pattern, package hole, and circuit board hole are aligned and assembled. Since the tip of the RF probe is completely covered with a dedicated short-circuit plate cap, it is possible to expect a stable operation without leakage of radio waves.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention. That is, the present invention has been disclosed in the form of exemplification, and the contents described in the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a view showing a structure (top view) of an RF probe substrate 10 according to an embodiment of the present invention. FIG. 2 is a view showing a cross-sectional structure of the RF probe substrate 10 shown in FIG. FIG. 3 is a view showing a modification (top view) of the RF probe substrate 10 shown in FIG. FIG. 4 is a diagram showing a cross-sectional structure of the RF probe substrate 10 shown in FIG. FIG. 5 is a diagram showing a structural cross section of a module on which the RF probe shown in FIGS. 3 and 4 is mounted. FIG. 6 is a diagram showing a configuration example (conventional example) of an RF probe substrate for transferring a high-frequency signal between the high-frequency signal circuit and the waveguide antenna. FIG. 7 is a diagram showing a cross-sectional configuration example (conventional example) of the RF probe substrate shown in FIG. FIG. 8 is a diagram showing a configuration example (conventional example) of an RF probe substrate for transmitting and receiving a high-frequency signal between the high-frequency signal circuit and the waveguide antenna. FIG. 9 is a diagram showing a cross-sectional configuration example (conventional example) of the RF probe substrate shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... RF probe board | substrate 11 ... 1st layer alumina substrate 12 ... 2nd layer alumina substrate 13 ... Ground 14 ... Waveguide opening 15 ... Short-circuit board cap 16 ... Microstrip line 17 ... Cap adhesion pattern 18 ... Earth pattern

Claims (5)

A substrate body in which a first dielectric layer and a second dielectric layer are laminated;
A ground formed on a lower surface of the first dielectric layer and having a waveguide opening;
A cap bonding pattern formed along the outer periphery of the waveguide opening on the upper surface of the second dielectric layer;
An annular ground pattern comprising a plurality of through-holes annularly formed on the cap bonding pattern;
A microstrip line formed between the first dielectric layer and the second dielectric layer and having one end inserted into the waveguide;
A short-circuit plate cap attached to the cap adhesive pattern;
An RF probe substrate comprising: The short-circuit plate cap does not have a notch over the entire circumference of the attachment portion with the cap adhesion pattern,
The RF probe substrate according to claim 1. A bonding pattern is formed at the other end of the microstrip line;
The second dielectric layer does not cover the bonding pattern;
The RF probe substrate according to claim 1. The second dielectric layer covers the entire microstrip line, and a through hole for line connection is formed in a portion corresponding to the other end of the microstrip line, and the through hole is conducted to connect the second dielectric layer. The other end of the microstrip line is taken out to the upper surface of the second dielectric layer, and a bonding pattern is disposed.
The RF probe substrate according to claim 1. A circuit module for microwave or millimeter wave communication, wherein the RF probe substrate according to claim 1 is used.

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