JP2006086808A - Antenna module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna module which reduces an influence over the generation of an unnecessary emission in the antenna module, which has excellent antenna characteristics and which reduces an interference during wiring and the malfunction of a circuit. <P>SOLUTION: The antenna module includes an antenna substrate 3 which has a single or a plurality of antenna elements 6 provided on one surface or in the interior of an insulating substrate, and which carries a semiconductor element 7 connected with the antenna element 6 in the other surface of the insulating substrate 3; and a module substrate 4 which mounts the antenna substrate 4. The signal radiated or received by the antenna element 6 is an analog signal. A signal exchanged between the antenna substrate 3 and the module substrate 4 is a digital signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna module including a high-frequency circuit that transmits and receives a high-frequency signal such as a microwave band and a millimeter-wave band and processes the signal.

  In recent years, microwaves have been used extensively as a carrier wave for wireless devices such as mobile phones. Currently, however, they are not limited to mobile phones, but as a means for high-capacity data communication such as wireless LAN and wireless USB. R & D is underway. Also, research and development such as ultra-high-speed wireless LAN and inter-vehicle radar are being actively promoted and put into practical use in satellite communications and point-to-point in the quasi-millimeter wave band, which is a higher frequency band than microwaves, and in the millimeter-wave region above 30 GHz. .

In order to transmit and receive these high-frequency signals, an antenna is required for impedance matching between the transmission line on the module substrate and space. In general, the antenna is often required to have a high gain or a narrow beam when communicating with a long distance, when it is desired to reduce communication power, or when it is desired to improve the angular resolution of the radar. As a method for obtaining such a high gain and narrow beam, an antenna element having an antenna element is mounted on the surface of the module substrate, and a dielectric lens is provided on the radiation side of the antenna element, thereby providing an antenna element. Patent Document 1 and Patent Document 2 propose to reduce the area of the substrate while reducing the size of the substrate.
JP 10-341108 A WO00 / 48269

  However, in an antenna module equipped with a conventional antenna board, it is unnecessary from the module board to the antenna board and the module board due to inconsistency in connection, unnecessary radiation due to circuit malfunction or interference, or from the semiconductor elements mounted on the antenna board. Radiation is likely to occur, and as a result, the unnecessary radiation may affect the gain and side lobe of the antenna element. In particular, when a dielectric lens is provided on the radiation side of the antenna element, the radiation pattern on the antenna substrate as the primary radiator has a great influence on the final radiation pattern via the lens, Measures against unnecessary radiation were necessary.

  Accordingly, an object of the present invention is to provide an antenna module that reduces the influence on the occurrence of unnecessary radiation in such an antenna module, has excellent antenna characteristics, and reduces interference between wires and circuit malfunction. To do.

  The antenna module of the present invention is an antenna in which a single or a plurality of antenna elements are provided on one surface or inside of an insulating substrate, and a semiconductor element connected to the antenna element is mounted on the other surface of the insulating substrate. An antenna module comprising a board and a module board on which the antenna board is mounted, wherein a signal radiated or received by the antenna element is an analog signal, and is exchanged between the antenna board and the module board The signal is a digital signal.

  Further, it is desirable that a conductor layer is formed in the antenna substrate at a position separating the antenna element and the semiconductor element. Particularly, the area of the conductor layer is 60% or more of the area of the antenna board. Is desirable.

  The present invention is particularly advantageous when a dielectric lens is provided on the radiation side of the antenna element.

  According to the antenna module of the present invention, the above-described configuration suppresses the influence of unnecessary radiation caused by circuit malfunction or interference on the secondary mounting board, that is, the module board, stabilizes the antenna input resistance, and provides the semiconductor element provided in the antenna board. The high frequency circuit such as can be operated normally.

  That is, by providing a single or a plurality of antenna elements on one surface or inside of the insulating substrate and mounting a semiconductor element connected to the antenna element on the other surface, the antenna substrate can be reduced in size, Since the antenna and the semiconductor element are not on the same plane, unnecessary radiation from the semiconductor element does not affect the antenna radiation pattern, and it is possible to prevent deterioration of the radiation pattern shape and interference, and conversely, the antenna element. The radiation from the semiconductor device does not cause malfunction of the semiconductor element.

  In addition, according to the present invention, by making the signal exchanged between the antenna substrate 3 and the module substrate 4 into a digital signal, a signal mainly composed of a frequency different from the electromagnetic wave radiated from the antenna element 6 can be obtained. As a result of the exchange between the board 3 and the module board 4, the error rate can be lowered. Note that the analog signal radiated or received from the antenna element 6 means a signal other than a signal represented by a string of numbers such as a digital signal, such as FSK (frequency shift keying) or PSK (phase shift keying). In this case, the digital signal is also included in the analog signal.

  Further, by providing a conductor layer provided inside the antenna substrate so as to separate the antenna element and the semiconductor element, the influence of unnecessary radiation generated from the semiconductor element on the antenna element, and conversely, radiation from the antenna element is achieved. The influence on the semiconductor element can be suppressed, interference and malfunction can be reduced, and the error rate can be lowered. In particular, when the area of the conductor layer is 60% or more of the area of the antenna substrate, the effect becomes remarkable.

  Hereinafter, the configuration of the antenna module of the present invention will be described with reference to the drawings. FIG. 1 shows a side view of an antenna module 1 which is an example of an embodiment of the present invention. The antenna module of the present invention includes a dielectric lens 2, an antenna substrate 3, and a module substrate 4, and the dielectric lens 2 is fixed to the module substrate 4 with a support 5.

  An antenna element 6 made of a microstrip antenna is formed on one surface of the antenna substrate 3, and a semiconductor element 7 for processing a signal radiated or received from the antenna element is mounted on the other surface. A conductor layer 9 serving as a ground is formed inside the substrate, and the semiconductor element 7 is connected to the antenna element 6 through a via conductor 10. The semiconductor element 7 is housed in a cavity provided on the other surface of the antenna substrate 3 and sealed with a cap 8 to prevent moisture and dust from entering. The semiconductor element may be sealed not only in the cavity but also embedded in the sealing resin.

  When the antenna element 6 and the semiconductor element 7 for controlling the antenna element 6 are provided on one antenna substrate, a signal radiated from the antenna element 6 affects the semiconductor element and causes a malfunction of the semiconductor element. On the contrary, unnecessary radiation from the semiconductor element affects the radiation pattern of the antenna element, resulting in a collapse of the radiation pattern, an increase in side lobe, and a decrease in gain. Further, when the antenna element and the semiconductor element are on the same surface, there is a disadvantage that the area of the substrate becomes large. Therefore, according to the present invention, by forming the semiconductor element 7 on the surface opposite to the surface on which the antenna element 3 is formed, the antenna radiation pattern such as malfunction of the semiconductor element, an increase in side lobe, and a decrease in gain is obtained. Deterioration can be prevented and the antenna substrate can be miniaturized.

  In FIG. 1, only one semiconductor element 7 is mounted. However, there is a problem even if a plurality of semiconductor elements such as an amplifier, a filter, a modem, a signal processing element, and a multiplier are mounted as this semiconductor element. There is no. In this case, among these elements, a semiconductor element having a large influence on the antenna element may be formed on the surface opposite to the surface on which the antenna element 6 is formed. It is most desirable to form on the surface.

  According to the present invention, the error rate can be reduced by converting the signal exchanged between the antenna substrate 3 and the module substrate 4 into a digital signal. As shown in FIG. 2, the digital signal is exchanged by the analog-digital converter 16 for down-converting the high-frequency signal received from the antenna element 6 by the local oscillator 15 and the frequency converter 14 to obtain a baseband signal. This can be done by converting it to a digital signal.

  Conversely, when a digital signal is received from the module substrate 4, the signal is processed and analog converted by the semiconductor element 7 mounted on the antenna substrate 3, and converted to an analog signal oscillated by the antenna element 6 by the frequency converter. It is possible.

  The digital signal is preferably a bit rate that is ¼ or less of the frequency of the carrier wave of the signal radiated or received from the antenna element 6. When the bit rate is larger than 1/4 of the carrier wave of the signal radiated or received from the antenna element 6, the harmonic component of the digital signal has the same frequency as the carrier wave of the signal radiated or received from the antenna element. This is because components may appear, causing interference and increasing the error rate.

  In addition, according to the present invention, it is desirable to provide the conductor layer 9 formed inside the antenna substrate 3 and separating the antenna element 6 and the semiconductor element 7, and the formation of the conductor layer 9 resulted from the semiconductor element. The influence of unnecessary radiation on the antenna element, and conversely, the influence of radiation from the antenna element on the semiconductor element can be suppressed, and interference and malfunctions can be reduced and the error rate can be lowered. The area of the conductor layer preferably occupies 60% or more, particularly 70% or more of the area of the antenna substrate. The “area of the antenna substrate” means the total area of the plane when the antenna substrate is viewed from above.

  In FIG. 1, a single-element microstrip antenna is shown as an antenna element, but the number of elements may be two or more, or an array antenna in which a plurality of antenna elements are arranged in an array.

  In addition to the microstrip antenna shown in FIG. 1, there is no particular problem with a planar antenna such as a bow tie antenna or a slot antenna, a helical antenna, a dipole antenna, an inverted L antenna, or an inverted F antenna. Further, the antenna element 6 is not necessarily formed on the substrate surface, and may be formed inside the substrate. In particular, from the viewpoint of protection of the antenna element, it is desirable to form an insulating protective layer made of resin or ceramic on the surface of the antenna element 6. In addition, as the antenna element, a dielectric resonator antenna, an antenna using a laminated waveguide as described in JP-A-11-46114, and the like can be used.

  In FIG. 1, the dielectric lens 2 is disposed at a predetermined distance above the antenna element. However, the dielectric lens 2 is not always necessary, but when the dielectric lens 2 is provided, The effect of the minute change in the radiation pattern of the antenna element on the final radiation pattern via the lens is significant, and the action according to the present invention is particularly effective. The dielectric lens 2 is fixed to the module substrate 4 according to FIG. 1, but the fixing destination of the dielectric lens 2 is not limited to this, and is fixed to another housing or the like. There is no problem even if the module substrate 4 is fixed to the housing.

  In the antenna substrate 3, in order to connect the antenna element 6 and the semiconductor element 7, generally known high-frequency lines such as a microstrip line, a strip line, a via, a coplanar line, a slot line, and a laminated waveguide are used. However, it is not particularly necessary to specify the line. Considering the ease of routing the line, a microstrip line and a strip line are preferable, and a laminated waveguide is preferable from the viewpoint of low transmission loss. Further, there is no problem even if signals are transmitted by electromagnetic connection using slots for reducing signal loss instead of VIA.

  In the antenna module of FIG. 1, in order to electrically connect the module substrate 4 and the antenna substrate 3, the antenna substrate 3 is BGA type with respect to the module substrate 4 and is connected to the connection pads 11 on the back surface of the antenna substrate 3. Although mounted on the circuit pattern 13 of the module substrate 1 via a plurality of attached solder balls 12, the mounting form of the antenna substrate 3 is not limited to this. For example, the antenna substrate 3 is not used without using solder balls. The connection pad 11 formed on the bottom surface of the module and the circuit pattern 13 of the module substrate 1 are directly connected to the LGA type by solder, the PGA type using metal pins, or the connection pad formed on the antenna substrate and the module substrate side. The circuit pattern may be connected using a wire. Among these, BGA and LGA are advantageous in that terminals can be formed at high density.

  The antenna substrate 3 is not a surface mount type, but is fixed to the surface of the module substrate 4 with an adhesive, and the electrode formed on the surface of the antenna substrate 3 and the electrode of the module substrate are bonded by a gold ribbon or gold wire bonding. A connected structure may be used. However, since wire bonding has problems such as parasitic inductance and mass productivity, the above-described surface mounting type is preferable because it is low-cost and has excellent characteristic stability.

  As a material constituting the antenna substrate 3, ceramics are preferable in view of mounting reliability of the semiconductor element 7, and a substrate made of an organic material containing at least a resin is preferable from the viewpoint of cost. In the case of using ceramics, examples of suitable materials generally include ceramics mainly composed of alumina, aluminum nitride, magnesia, etc., and low-temperature fired ceramics that can be fired at 1000 ° C. or less, such as glass ceramics. Among these, the loss in the transmission line is large at high frequencies, and it is required to reduce the resistance of the conductor layer in order to suppress the loss. From this point, low-temperature fired ceramics or organic multilayer substrates that can use copper or silver conductors are required. Preferably, low-temperature fired ceramics with low dielectric loss are optimal. In the organic substrate, a fluorine resin is preferable.

  As the material constituting the module substrate 4, similarly to the antenna substrate 3, ceramics mainly composed of alumina, aluminum nitride, magnesia, low-temperature fired ceramics, organic multilayer substrates, etc. can be used. No. However, from the viewpoint of manufacturing cost, an inexpensive organic substrate of glass-epoxy resin such as FR-4 or FR-5 is preferable.

  In order to evaluate the communication characteristics of the antenna module of the present invention as an antenna module, an error rate was investigated by actually assembling the system.

  The antenna substrate is 40 mm × 40 mm × 3.0 mm thick, 50% by mass of a borosilicate glass having a dielectric constant of 4.9, and 50% by mass of alumina. Then, one microstrip antenna was formed on the surface and used as a primary radiator. All the high-frequency lines, via conductors, and conductor layers in the microstrip antenna and the antenna substrate were formed by co-firing with an insulating substrate at 900 ° C. using copper metallization. The area of the conductor layer was variously changed as shown in Table 1.

  Further, a cavity as shown in FIG. 1 was provided on the surface opposite to the antenna element formation surface of the antenna substrate, and a semiconductor element was flip-chip mounted as a control element in the cavity.

  On the other hand, as the module substrate, an insulating substrate made of a composite insulator made of glass-epoxy resin having a copper conductive pattern formed thereon was prepared, and the antenna substrate was surface-mounted through solder balls. In addition, a dielectric lens formed of ceramics mainly composed of borosilicate glass having a dielectric constant of 5.0 was disposed on the radiation surface of the antenna element.

In measuring the error rate, the frequency (f ₀ ) of the received signal (carrier wave) from the antenna element was 61 GHz. This was converted to a baseband by a frequency converter and a local oscillator, and converted to a digital signal by an analog / digital converter. The bit rate of the digital signal is 500 Mbps. A horn antenna that radiates a signal is installed opposite to the antenna module, the signal radiated from the horn antenna is received and demodulated by the antenna module, and the error rate is evaluated by comparing with the original signal.

  Further, as Comparative Example 1, an antenna substrate in which a semiconductor element was provided on the opposite side of the antenna element formation surface but digital conversion was not performed was manufactured. Moreover, as Comparative Example 2, a control element was prepared on the surface of the antenna substrate together with the antenna element. This is formed by flip-chip mounting a frequency converter for a down converter, a local oscillator, and an analog / digital converter for converting into a digital signal on the same surface as the antenna element formation surface.

  In the same manner as above, these antenna elements are mounted on the surface of the module board via solder balls to produce an antenna module that transmits signals received by the antenna element to the module board as analog signals without frequency conversion. did.

Among the comparative examples, the error rate in the antenna module of comparative example 1 was set to “1” and compared with the error rates of other modules.

  According to the results in Table 1, a semiconductor element is provided on the surface opposite to the surface on which the antenna element is formed, converted into a digital signal, and a frequency and a signal exchanged between the antenna substrate and the module substrate are converted into a digital signal. Therefore, the error rate can be reduced as compared with the case of the analog signal. Also, when the frequency at the antenna element is 61 GHz, there is almost no change in the error rate when the area of the metal layer is smaller than 60%, but the error rate decreases when the area ratio is 60% or more. I can understand that. In particular, by setting it to 70% or more, the error rate can be suppressed to 0.9 or less, which is more preferable.

It is a schematic perspective view for demonstrating an example of invention of the antenna module of this invention. An example of the circuit diagram for converting into the digital signal in the antenna module of this invention is shown.

Explanation of symbols

1 .... Antenna module 2 ... Dielectric lens 3 ... Antenna substrate 4 ... Module substrate 5 ... Support Body 6 ... Antenna element 7 ... Semiconductor element 8 ... Cap 9 ... Conductor layer

Claims (4)

A single or plural antenna elements are provided on one surface or inside of the insulating substrate, and an antenna substrate on which a semiconductor element connected to the antenna element is mounted on the other surface of the insulating substrate, and the antenna substrate An antenna module including a module substrate mounted thereon, wherein the signal radiated or received by the antenna element is an analog signal, and the signal exchanged between the antenna substrate and the module substrate is a digital signal. An antenna module characterized by that. The antenna module according to claim 1, wherein a conductor layer is formed in the antenna substrate at a position separating the antenna element and the semiconductor element. The antenna module according to claim 2, wherein the area of the conductor layer occupies 60% or more of the area of the antenna substrate. The antenna module according to any one of claims 1 to 3, wherein a dielectric lens is provided on a radiation side of the antenna element.

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