JP2007243455A - Compact mobile terminal device for radio reception - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact mobile terminal device for radio reception which is optimal for mobile reception by lowering a correlation between antennas to attain a diversity effect. <P>SOLUTION: As a correlation changing mechanism 25 for changing the correlation between a plurality of antenna elements 11A and 11B installed at the ends of a plurality of projecting pieces 15a and 15b which are formed by cutting out the edge of an upper grounding conductor 15A, a variable reactance element 22 and a switch 23 are installed. The correlation changing mechanism 25 lowers the correlation between the antenna elements 11A and 11B by changing the phase of a high-frequency current flowing in the upper grounding conductor 15A. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a small-sized portable terminal device for wireless reception that is optimal for mobile reception.

  2. Description of the Related Art Conventionally, suppression of interference waves generated by reflection and diffraction has been essential for mobile reception in a small mobile terminal device for wireless reception such as a mobile phone, a mobile TV, and a wireless communication card. As one of the interference wave suppression techniques, diversity reception is known.

  For diversity reception, an antenna selective reception method using a switch shown in FIG. 20, a high frequency signal level combined reception method shown in FIG. 21, a data level combined reception method shown in FIG. 22, and the like have been proposed. The lower the value, the greater the diversity effect.

  In the antenna selective reception method using the switch shown in FIG. 20, a plurality of antennas 111A and 111B are arranged, the reception signal is switched at high speed using the antenna switch 112, and the one with the higher electric field level is selected. The received signal received via the antenna selected by the antenna switch 112 is frequency-converted by the frequency converter 113 and demodulated by the demodulator 114.

  In the high frequency signal level composite reception system shown in FIG. 21, the received signals received by the plurality of antennas 211A and 211B are frequency-converted by frequency converters 212A and 212B, respectively, and digitally converted by analog to digital converters 213A and 213B. The signal is converted into a signal, and the weight calculation processing unit 214 weights the difference in level of each received signal, and the demodulator 215 demodulates the received signal.

  Further, in the data level combined reception system shown in FIG. 22, the received signals received by the plurality of antennas 311A and 311B are frequency-converted by the frequency converters 312A and 312B, respectively, and the digital signals are converted by the analog / digital converters 313A and 313B. And demodulated by the demodulators 314A and 314B and synthesized by the weight calculation processing unit 315.

  As an antenna arrangement method for diversity reception, as shown in FIG. 23, the antennas 411A and 411B are separated from each other by being separated from each other and the direction of the antennas 511A and 511B arranged as shown in FIG. 24 is changed. Polarization diversity is common.

  In space diversity, as the distance between the antennas 411A and 411B increases, the correlation between the antennas decreases and the diversity effect increases. However, depending on the use state and installation environment, it is not always possible to separate the antennas. Absent.

  Therefore, in the antenna device using space diversity in Patent Document 1, coupling between the antennas is prevented by making a slit in the ground conductor of the device formed from the antenna and the ground conductor, and the correlation is lowered.

  Moreover, in patent document 2, the same effect is acquired by putting a groove | channel between antennas.

  On the other hand, in Patent Document 3, a low-correlation state is created by a parasitic antenna that does not directly feed a signal and a variable reactance element connected thereto.

  Furthermore, it has been theoretically clarified that when power is supplied with the phase difference between the antennas being 90 °, a cardioid type directivity with a null point in one direction is obtained.

JP 09-238020 A JP-T-2004-519148 JP 2005-295002 A

  However, when a plurality of antennas are arranged in a small mobile terminal as compared with the electrical length of the frequency used, the correlation between the antennas is high, and the coupling between the antennas does not decrease by slitting the ground conductor. . Further, even if a parasitic antenna and a variable reactance element connected thereto are used, it is difficult to realize a low correlation, and there are many space restrictions.

  Therefore, in view of the conventional problems as described above, the object of the present invention is to provide a correlation between antennas even in a configuration such as a portable terminal in which the size of the ground conductor is small compared to the electrical length of the frequency to be used. An object of the present invention is to provide a small portable terminal device for radio reception that is low and that is optimal for mobile reception so as to obtain a diversity effect.

  Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the description of embodiments described below.

  A small-sized portable terminal device for wireless reception according to the present invention includes a ground conductor, a plurality of antenna elements provided at tip portions of a plurality of projecting pieces formed by notching edges of the ground conductor, and the ground conductor. And a correlation changing mechanism that changes the correlation between the antenna elements. The correlation changing mechanism changes the phase of the high-frequency current flowing through the ground conductor, thereby changing the correlation between the antenna elements. The correlation between elements is reduced.

  In the small wireless portable terminal device for radio reception according to the present invention, the correlation changing mechanism may change the phase of the high-frequency current flowing through the ground conductor to change the phase difference between the antennas to 90 °, for example. Reduce the correlation between.

  Further, in the small wireless portable terminal device for wireless reception according to the present invention, the correlation changing mechanism is composed of an element that changes the reactance of each protruding piece portion provided with each antenna element, for example.

  Furthermore, in the small portable terminal device for wireless reception according to the present invention, the correlation changing mechanism shortens each protruding piece portion by providing an element for changing reactance in each protruding piece portion provided with each antenna element. Even so, the phase difference between the antennas can be 90 °.

  In the present invention, even in a configuration such as a portable terminal in which the size of the ground conductor is small compared to the electrical length of the frequency to be used, the correlation between the antennas is low, and a diversity effect can be obtained. It is possible to provide a small mobile terminal device for wireless reception that is optimal for mobile reception in a wireless communication card or the like.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Needless to say, the present invention is not limited to the following examples, and can be arbitrarily changed without departing from the gist of the present invention.

  The present invention is applied to a small mobile terminal device 10 for wireless reception provided with two antennas 11A and 11B for diversity reception as shown in FIG. 1, for example.

  The wireless reception small portable terminal device 10 is a portable terminal that can be folded, and includes a lower half portion 13 provided with various operation buttons 12 and an upper half portion 15 provided with a display panel 14. The half part 13 and the upper half part 15 are connected via a hinge part 16 so as to be foldable. The lower half portion 13 and the upper half portion 15 are configured by a printed circuit board on which ICs and components such as signal reception, arithmetic processing, and a display device are mounted, and are electrically connected by a connecting line formed of a polyimide resin or the like in the hinge portion 16. Connected to each other. The two antennas 11 </ b> A and 11 </ b> B are provided at the upper end portion of the upper half portion 15.

  Here, in general, the correlation representing the effect of diversity is a factor of how much radio waves received by a plurality of antennas influence each other, and the following equation (1) depends on the directivity of the receiving antenna. ).

In Expression (1), Cr is a correlation coefficient, E ₁ and E ₂ are complex directivities of the antenna, and θ and φ represent coordinate angles of polar coordinates.

  As described above, in the foldable portable terminal in which the lower half portion 13 and the upper half portion 15 are foldably connected via the hinge portion 16, the lower half portion 13 and the upper half portion 15 are high frequency. As shown in FIG. 2, two antennas functioning as ground conductors may be installed parallel to each other, or may be installed orthogonal to each other in FIG. is there. In addition, as a usage type of the folding type portable terminal, there are an open state and a folded closed state. As shown in FIGS. 2A and 3A, two antennas 11A for diversity reception in the open state. 11B, the lower half portion 13 and the upper half portion 15 that are electrically connected to each other by a connecting line 16A made of polyimide resin or the like in the hinge portion 16 function as ground conductors 13A and 15A, respectively. In the folded closed state, as shown in FIGS. 2 (B) and 3 (B), the lower ground conductor 13A that hits the lower half portion 13 and the upper ground conductor 15A that hits the upper half portion 15 face each other. Therefore, the substantial ground conductor area for the two antennas 11A and 11B for diversity reception becomes half of the open state.

  Here, consider the case of a portable terminal in which the size of the ground conductor is small compared to the electrical length of the frequency used. Since the use frequency of the UHF band for television broadcasting is 470 MHz (wavelength 630 mm) or more, when the conductor size 75 × 40 mm of a general portable terminal is converted into an electrical length, it becomes 0.12λ × 0.06λ. Similarly, even in a wireless LAN card using the 2.4 GHz band, there is a case where it is equivalent to 0.12λ × 0.06λ in terms of electrical length. Hereinafter, the case where the size of the conductor is 0.12λ × 0.06λ in terms of electrical length will be considered. However, the size is not necessarily limited to this size, and the size that can be similarly estimated is not limited to this.

  FIG. 4 shows the correlation between the two antennas 11A and 11B for diversity reception in the foldable portable terminal. In FIG. 4, the horizontal axis represents the distance d / λ between antennas in terms of electrical length, and the vertical axis represents the correlation coefficient Cr of the antenna. As is clear from FIG. 4, when the inter-antenna distance d is increased, the correlation decreases, but there is a limit to the decrease in the correlation because of the size restriction of the mobile terminal. The same applies to the configuration of polarization diversity in which antennas are arranged orthogonally.

  Here, FIG. 5 shows the correlation between the antennas 11A and 11B when two antennas 11A and 11B for diversity reception are provided on ground conductors of various sizes and the distance d between the antennas is changed. In FIG. 5, the horizontal axis represents the distance d / λ between antennas in terms of electrical length, and the vertical axis represents the correlation coefficient Cr of the antenna. In FIG. 5, when the characteristic F1 is provided on a ground conductor having a notebook PC size (electrical length converted size (vertical × horizontal) is 0.31λ × 0.47λ), the characteristic F2 is a small notebook PC size (electrical length). When provided in a grounded conductor having a converted size (vertical × horizontal) of 0.17λ × 0.25λ), the characteristic F3 has a PDA size (electrical length converted size (vertical × horizontal) is 0.12λ × 0.17λ). The characteristic F4 indicates a case where it is provided on a grounding conductor having a folding portable size (size converted to electrical length (vertical × horizontal) is 0.12λ × 0.06λ × 2). Characteristic F4 (a) shows a closed state, and (b) shows an open state.

  Next, as shown in FIG. 6, a notch (groove) 20 is provided in the ground conductor 15A between the antennas 11A and 11B, the distance d between the antennas is 0.053λ, and the notch width w is 0.007λ. FIG. 7 shows the correlation between the antennas 11A and 11B when the notch length h is changed by the field analysis. FIG. 6A shows an open state of the foldable portable terminal, and FIG. 6B shows a closed state of the foldable portable terminal. In FIG. 7, the horizontal axis represents the notch length h / λ in terms of electrical length, and the vertical axis represents the correlation coefficient Cr of the antenna. As is apparent from FIG. 7, when the notch length h is increased, the correlation coefficient Cr decreases. The notch length at this time is 0.1λ or less. Further, FIG. 8 and FIG. 9 show amplitude directivity and zx plane phase directivity by electromagnetic field analysis when the notch length h is 0.087λ. Although no significant change is seen in the amplitude directivity, the phase difference between the antennas 11A and 11B when the zx plane phase directivity is not present is about 40 ° at the maximum when the notch 20 is not present. In some cases, the phase difference is as large as about 65 °. From this, it can be said that the main cause of the decrease in the correlation is the phase difference between the two elements. Therefore, by inserting the notch 20 in the ground conductor 15A between the antennas 11A and 11B, the path of the high-frequency current flowing between the antennas 11A and 11B is changed, and the correlation is lowered by adding a phase difference. become.

  Here, FIG. 10 shows the correlation between the antennas 11A and 11B when the distance d between the antennas is 0.053λ, the notch length h is 0.06λ, and the notch width w is changed by electromagnetic field analysis. In FIG. 10, the horizontal axis represents the notch width w / λ in terms of electrical length, and the vertical axis represents the correlation coefficient Cr of the antenna.

  Further, as shown in FIG. 11, the correlation coefficient Cr when the notch length h is changed when the capacitor 21 is loaded in the notch 20 is shown in FIG. FIG. 11A shows an open state of the foldable portable terminal, and FIG. 11B shows a closed state of the foldable portable terminal. As can be seen from FIG. 12, the correlation decreases at about half the notch length h compared to when the capacitor 21 is not loaded, but the correlation increases when the notch length is h / λ = 0.047. The amplitude directivity and phase directivity on the zx plane are shown in FIGS. Although no significant change is seen in the amplitude directivity, the maximum value of the phase difference when the correlation is the lowest approaches 90 ° when looking at the zx plane phase directivity. When the sum of the phase difference of the path change due to the insertion of the notch 20 and the phase difference of the capacitor 21 approaches 90 °, the mutual coefficient Cr decreases.

  It is known that when feeding with a phase difference between antennas of 90 °, a cardioid directivity with a null point in one direction is obtained, but using the form of the present invention, the feeding line is phased. The phase difference between the antennas can be adjusted to 90 ° by a notch added to the ground conductor. Further, by adding a capacitor, the phase difference between the antennas can be 90 ° even if the notch length is shortened.

  Here, assuming that the distance d between antennas is 0.053λ, the notch width W is 0.007λ, the insertion position of the capacitor 21 is an end (a = 0), and the notch length h is 0.013λ, FIG. 15 shows the correlation between the antennas 11A and 11B when the capacitance value C [pF] is changed. In FIG. 15, the horizontal axis represents the capacitance value C [pF], and the vertical axis represents the antenna correlation coefficient Cr.

  Further, when the inter-antenna distance d is 0.053λ, the notch width W is 0.007λ, and the notch length h is 0.013λ, the insertion position a of the capacitor 21 by electromagnetic field analysis is changed between the antennas 11A and 11B. The correlation is shown in FIG. In FIG. 16, the horizontal axis represents the insertion position a / λ of the capacitor 21 in terms of electrical length, and the vertical axis represents the antenna correlation coefficient Cr.

  And in this small portable terminal device 10 for radio reception, the tip portions of the two projecting pieces 15a and 15b formed by notching the edge of the upper ground conductor 15A that hits the upper half portion 15 and providing a recess, that is, the notch 20 In addition, two antennas 11A and 11B for diversity reception are provided, for example, as a correlation changing mechanism 25 that changes the correlation between antenna elements in a recess, that is, a notch 21 portion where the edge of the upper ground conductor 15A is cut out. For example, a variable reactance element 22 as shown in FIG. 17A or a switch 23 as shown in FIG. Then, the correlation change mechanism 25 changes the phase of the high-frequency current flowing through the upper ground conductor 15A, and the phase difference between the antennas 11A and 11B is set to 90 °, thereby reducing the correlation between the antenna elements. . That is, depending on the length (h) of the notch 21, the installation position (hr) of the variable reactance element 22, the installation position (hs1, hs2) and number of the switch 23, the reactance value of the variable reactance element 22, the state of the switch 23, etc. Control is performed so that the phase difference between the antennas 11A and 11B is 90 ° at the use frequency. The variable reactance element 22 is a capacitance, an inductance, a varicap (varactor diode), a transistor, a phase shifter, or the like, and may be any element that affects the impedance of the high-frequency current. The switch 23 may be any switch that changes the path of the high-frequency current, such as a switch made of GaAs, a PIN diode, or MEMS. Further, the correlation changing mechanism 25 may be a combination of the variable reactance element 22 and the switch 23.

  Furthermore, in this small portable terminal device 10 for wireless reception, as shown in FIG. 18, two antennas 11A and 11B for diversity reception are connected to a reception unit 32 via a diversity circuit 31, and are connected to the reception unit 32. The correlation changing mechanism 25 including the variable reactance element 22 or the switch 23 is controlled by the control unit 33 that provides a reception frequency selection signal.

  As shown in the flowchart of FIG. 19, when the control unit 33 starts operating, it first determines whether or not there is a change in the reception frequency (step S1), and the determination result is YES, that is, there is a change in the reception frequency. In this case, the selection of the reception frequency is accepted (step S2). Then, a control signal corresponding to the received reception frequency selected is generated (step S3), the correlation changing mechanism is controlled so that the phase difference between the two antennas becomes 90 °, and the receiving unit is After control and tuning to the reception frequency (step S4), reception is started (step S5). If the determination result in step S2 is NO, that is, if there is no change in the reception frequency, reception starts immediately (step S5).

  Then, it is determined whether or not to end the reception (step S6). If the determination result is NO, that is, if the reception is continued, the process returns to step S1 and repeats steps S1 to S6. When the result is YES, the control operation is terminated.

  In the small-sized mobile terminal device 10 for wireless reception having such a configuration, even in a configuration such as a mobile terminal in which the size of the ground conductor is 0.25λ or less compared to the electrical length λ of the frequency to be used, A diversity effect can be obtained by lowering the correlation, which is optimal for mobile reception in a mobile phone, a mobile TV, a wireless communication card, and the like.

It is an external appearance perspective view of the small portable terminal device for radio | wireless reception to which this invention is applied. It is a figure which shows typically the example which installed two antennas for diversity reception in parallel in a foldable portable terminal. It is a figure which shows typically the example which installed two antennas for diversity reception in a foldable portable terminal so as to be orthogonal. It is a characteristic view which shows typically the correlation of the two antennas for diversity reception in a foldable portable terminal. It is a characteristic view which shows typically the correlation between antennas when two antennas for diversity reception in a foldable portable terminal are provided on ground conductors of various sizes and the distance between the antennas is changed. It is a perspective view which shows typically the state which put the notch (groove | channel) in the grounding conductor between the two antennas for diversity reception in a foldable portable terminal. It is a characteristic view which shows typically the correlation between antennas when notch length is changed. It is a characteristic view which shows typically the amplitude directivity by electromagnetic field analysis when the said notch length is 0.087λ. It is a characteristic view which shows typically zx surface phase directivity by electromagnetic field analysis when the above-mentioned notch length is 0.087λ. It is a characteristic view which shows typically zx surface phase directivity by electromagnetic field analysis at the time of changing notch width. It is a perspective view which shows typically the state which loaded the capacitor to the notch part. FIG. 6 is a characteristic diagram schematically showing the correlation between the notch length and the antenna when a capacitor is loaded in the notch portion. It is a characteristic view which shows typically the amplitude directivity of the zx plane when a capacitor is loaded in the notch part. It is a characteristic view which shows typically the phase directivity of zx surface when a capacitor is loaded in a notch part. It is a characteristic view which shows typically the correlation between antennas when a capacitance value is changed when a capacitor is loaded in a notch part. It is a characteristic view which shows typically the correlation between antennas at the time of changing the insertion position of a capacitor. It is a figure which shows typically the state which provided the correlation change mechanism which changes the correlation between antenna elements in the recessed part which notched the edge part of the upper ground conductor. It is a block diagram which shows the electrical principal part structure of the said small portable terminal device for radio | wireless reception. It is a flowchart which shows the procedure of the control operation | movement by the control part in the said small portable terminal device for radio | wireless reception. It is a block diagram which shows the operation principle of the diversity reception of the antenna selection reception system by a switch. It is a block diagram which shows the operation principle of the diversity reception of the synthetic reception system of a high frequency signal level. It is a block diagram which shows the operation | movement principle of the diversity reception of the composite reception system of a data level. It is a figure which shows typically the antenna arrangement | positioning of space diversity. It is a figure which shows typically the antenna arrangement | positioning of polarization diversity.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Small portable terminal device for radio | wireless reception, 11A, 11B antenna, 12 types of operation buttons, 13 Lower half part, 13A Lower ground conductor, 14 Display panel, 15 Upper half part, 15A Upper ground conductor, 15a, 15b Projection piece, 16 Hinge part, 16A connecting line, 20 notch, 21 capacitor, 22 variable reactance element, 23 switch, 25 correlation changing mechanism, 31 diversity circuit, 32 receiving part, 33 control part 33

Claims (4)

A ground conductor;
A plurality of antenna elements provided at tip portions of a plurality of projecting pieces formed by cutting out the edge of the ground conductor;
A correlation change mechanism that is provided in a recess formed by cutting out the edge of the ground conductor and changes the correlation between antenna elements;
The wireless reception small portable terminal device, wherein the correlation changing mechanism reduces the correlation between antenna elements by changing a phase of a high-frequency current flowing through the ground conductor.   2. The correlation changing mechanism reduces a correlation between antenna elements by changing a phase of a high-frequency current flowing in the ground conductor and setting a phase difference between the antennas to 90 degrees. A small portable terminal device for wireless reception as described.   2. The small portable terminal device for wireless reception according to claim 1, wherein the correlation changing mechanism includes an element for changing a reactance of each projecting piece portion provided with each antenna element.   The correlation changing mechanism can provide a phase difference between antennas of 90 ° even if each projecting piece portion is shortened by providing an element that changes reactance at each projecting piece portion provided with each antenna element. The small-sized portable terminal device for wireless reception according to claim 3, wherein:

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