JP2008072486A - Antenna for portable radio set, and the portable radio set - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna for a portable radio set which realizes high-quality communication by elevating the gain at data communication or waiting at an operating frequency, and can reduce SAR (specific absorption rate) at speech, when a head of a human body approaches. <P>SOLUTION: The radio set is provided with a cabinet 1 which houses a radio unit, and a first and a second antenna elements 10, 12 which are arranged in a top end unit of the cabinet. The first antenna element 10 has a feeding unit 11 for exciting by an operating frequency using current, which flows on the cabinet and exciting the first antenna element 10 in a side end unit of the cabinet 1. The second antenna element 12 has a short circuit unit 13 which is arranged facing to the first antenna element 10 and connects to an earth unit 18 installed on the cabinet 1 near the feeding unit 11, and has an electrical length which is a little short than the first antenna element 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a built-in antenna for a portable wireless device and a portable wireless device that are mounted on a portable wireless device that communicates voice, data, and the like.

  In recent years, the specific absorption rate (SAR) of electromagnetic wave energy absorbed per unit time by a tissue of unit mass has been evaluated as an effect of electromagnetic waves generated by a mobile phone on a human body during a call. The standard value is defined as a local SAR, which is the standard of electromagnetic waves allowed by the human body, and it is required by laws and regulations that devices that generate electromagnetic waves in the vicinity of the human body, such as portable wireless devices, be kept below this standard value.

  Incidentally, the local SAR in Japan is determined such that the average value of the amount of energy absorbed in 6 minutes by an arbitrary tissue per 10 g is 2.0 W / kg or less.

  By the way, recent portable wireless devices tend to have built-in antennas from the viewpoint of portability and design. In many cases, a λ / 4 antenna is used as the built-in antenna, but this λ / 4 antenna operates as a whole antenna by passing a high-frequency current to the ground conductor or shield case of the housing to some extent. .

  Especially in straight-type portable wireless devices, the antenna element is often covered with the hand during a call to avoid deterioration of the antenna characteristics. Since it is in close contact with the vicinity, the vicinity of the power feeding portion of the antenna through which a large current flows is very close to the human head. At this time, since the high-frequency current also flows through the housing and operates as a part of the antenna, the local SAR near the ear often increases.

Here, as one of the methods for reducing the SAR, as shown in Patent Document 1, one end of the conductive flat plate is electrically short-circuited to the ground conductor, and the conductive flat plate closer to the antenna feeding portion than the one end is used. The other end is electrically opened from the ground conductor, and the input impedance of the open end of the conductive plate is made close to infinity with respect to the radio communication frequency. There is a method of reducing the SAR by suppressing the high-frequency current flowing into the.
JP 2001-308622 A

  However, although this method reduces the SAR, the high-frequency current is constantly suppressed, so that the gain is lowered during data communication and standby that do not require consideration of the SAR, and the communication quality deteriorates.

  The present invention has been made in view of the above points, and realizes high-quality communication by increasing the gain at the time of data communication and standby, and the gain is slightly reduced at the time of a call, but is absorbed by the human body by changing the current distribution. An object of the present invention is to provide a portable radio antenna and a portable radio capable of greatly reducing the amount of electromagnetic waves generated.

  According to a first aspect of the present invention, there is provided an antenna for a portable radio having a first antenna element and a second antenna element in a housing incorporating a radio unit, wherein the first antenna element is provided. Uses a current flowing on the housing to excite at a used frequency, and has a feeding portion for exciting the first antenna element at a side end portion of the housing. Sometimes disposed closer to the human head than the first antenna element, facing the first antenna element, having a short circuit near the feeding point of the first antenna element, It is characterized by having an electrical length shorter than that of the antenna element.

  The first antenna element is a λ / 4 antenna having an electrical length of approximately λ / 4 with respect to the use frequency because the first antenna element is excited at the use frequency using the current flowing on the housing. can do.

  Further, the position close to the human head can be near the receiver. In addition, the first and second antenna elements can be arranged at the upper end of the casing in order to avoid being covered by hand during data communication.

  Further, the second antenna element preferably includes means for making the electrical length variable, and as one of them, between the short-circuit portion and the grounding portion provided in the casing, Switching means for turning ON / OFF the connection between the short-circuit portion and the ground portion can be provided.

  Further, as a means for making the electrical length of the second antenna element variable, a variable reactance for making the reactance variable is provided between the short-circuit portion and the grounding portion provided in the housing. It can be.

  Further, as a means for making the electrical length of the second antenna element variable, between the open end of the second antenna element and the second grounding portion provided in the housing, Switching means for turning on / off the connection between the open end and the second grounding portion may be provided.

  Further, as means for making the electrical length of the second antenna element variable, the connection between the open end of the second antenna element and the conductive pattern provided on the housing is turned ON / OFF. It is possible to provide switching means for performing.

  Furthermore, a portable wireless device according to a tenth aspect of the invention includes the portable wireless device antenna according to any one of the first to ninth aspects, in order to achieve the above-described object.

  As described above, according to the present invention, an antenna that operates by passing a high-frequency current over a housing provides high-quality communication during data communication when the human head is not in proximity, and SAR during communication when the human head is in proximity. There is an effect that can be reduced. That is, by electrically coupling the first antenna element and the second antenna element, when the human body is not in proximity, the current can be added in the same phase in the use band, thereby increasing the gain. Further, when the human body is close, the SAR can be greatly reduced because the gain is reduced while changing the current distribution by canceling out the currents in opposite phases in the use band. In addition, by making the electrical length of the second antenna element variable, it is possible to eliminate the influence on other bands, and to perform multi-band, high-quality data communication / calls with reduced SAR. is there.

  According to the first aspect of the present invention, the second antenna element is short-circuited in the vicinity of the feeding portion of the first antenna element, and the high-frequency current on the casing depending on the first antenna element is supplied to the second antenna. By flowing through the element, the first and second antenna elements are electrically coupled at the resonance frequency of the second antenna element slightly higher than the resonance frequency of the first antenna element. At a frequency slightly lower than the resonance frequency of the second antenna element, a current in phase with the current from the first antenna element flows on the second antenna element, and the resonance frequency of the second antenna element and At a slightly low resonance frequency, the current can be strengthened and the gain can be increased. This phenomenon is called effective resonance. That is, at the time of data communication in which no human body is close to the second antenna element, high-quality data communication can be performed by setting the frequency whose gain is increased by effective resonance within the use band.

  Further, according to such a configuration, a current having a phase opposite to that of the first antenna element flows on the second antenna element at a frequency slightly higher than the resonance frequency of the second antenna element, By canceling the current, the current distribution is changed and the gain is reduced. This phenomenon is called unnecessary resonance. That is, during a voice call where the human body is close to the second antenna element, unnecessary resonance that was outside the use band is moved into the use band due to the wavelength shortening effect due to the dielectric constant of the human body. Since the distribution is changed, it is possible to perform a voice call with significantly reduced SAR.

  According to the second aspect of the present invention, the current in the vicinity of the feeding portion of the first antenna element is maximized by setting the first antenna element to an electrical length of approximately λ / 4 with respect to the operating frequency. Therefore, the current flowing on the housing by the first antenna element can be greatly flowed to the second antenna element, and the first and second antenna elements can be electrically strongly coupled. Therefore, a great effect can be obtained.

  According to the third aspect of the present invention, by arranging the second antenna element in the vicinity of the receiver, the human head can be surely brought close to the second antenna element during a call. Voice calls can be greatly reduced.

  According to the fourth aspect of the present invention, by arranging the first and second antenna elements at the upper end of the housing, it is possible to perform high-quality data communication without approaching the human body during data communication.

  According to the fifth aspect of the present invention, since the electrical length of the second antenna element is variable, the resonance frequency of the second antenna element can be adjusted, and the unnecessary resonance is included in another use frequency band. Even in such a case, deterioration of communication quality can be avoided.

  According to a sixth aspect of the present invention, the unnecessary resonance is caused to change to another frequency band used by the switching means for turning on / off the connection between the short-circuit portion of the second antenna element and the ground portion of the housing. It is possible to avoid degradation of communication quality even when included in the network. That is, by switching off the connection between the short-circuit portion and the grounding portion of the housing and opening the short-circuit portion, no current flows through the second antenna element near the operating frequency, and the second This is the same as when no antenna element is arranged. Accordingly, it is possible to eliminate the unnecessary resonance in which the gain is reduced in other use frequency bands.

  According to the seventh aspect of the present invention, the electrical length of the second antenna element is variable by a variable reactance provided between the short-circuit portion of the second antenna element and the grounding portion of the housing. Therefore, the second antenna element can be moved with the frequency of effective resonance and unnecessary resonance. Therefore, when the unnecessary resonance is included in another use frequency band, it is possible to avoid deterioration of communication quality by moving the unnecessary resonance by the second antenna element out of the use band by variable reactance. In addition, it is possible to perform high-quality data communication in multiband by moving the effective resonance into another use band, and in multiband by moving unnecessary resonance in another use transmission band during a call. Calls with reduced SAR can be performed. Further, according to such a configuration, when the space in which the second antenna element can be arranged is small with respect to the use frequency, the electrical length of the second antenna element can be made variable by the variable reactance. Can make up for the lack of space.

  According to the invention of claim 8, by the switching means for turning on / off the connection between the open end of the second antenna element and the second grounding portion provided near the open end of the housing, Even when the unnecessary resonance is included in another use frequency band, it is possible to avoid deterioration of communication quality. That is, by switching the connection between the open end and the second grounding portion to ON by the switching means to make a short circuit, the second antenna element does not operate as an antenna, and the second antenna element is This is the same as when not arranged. Accordingly, it is possible to eliminate the unnecessary resonance in which the gain is reduced in other use frequency bands.

  According to the ninth aspect of the present invention, the second antenna element is switched by switching means for turning on / off the connection between the open end of the second antenna element and the conductive pattern provided on the housing. Since resonance can be performed at a plurality of frequencies, it is possible to avoid deterioration in communication quality even when the unnecessary resonance is included in another use frequency band. That is, when the connection between the open end and the conductive pattern is switched ON by the switching means, the electrical length of the second antenna element is increased, so that the resonance frequency is moved to the low frequency side. Will be. Accordingly, it is possible to remove the unnecessary resonance in which the gain decreases in other use frequency bands, and to increase the gain in other use frequency bands.

  According to the invention described in claim 10, since the portable radio antenna according to any one of claims 1 to 9 is used, high-quality communication can be performed during data communication, and SAR can be performed during a call. It is possible to obtain a portable wireless device capable of performing a voice call with greatly reduced noise.

(First embodiment)
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the portable wireless device according to the present embodiment is formed using a substantially conductive material, and includes a housing 1 of a wireless unit that includes components such as a shield, a printed circuit board, and a battery. Short-circuited to a first antenna element 10 formed of a conductive member such as a sheet metal disposed on the body 1 and a grounding portion 18 provided in the housing 1 near the power feeding portion 11 of the first antenna element 10. The housing 1 is attached to the first antenna element 10 and the second antenna element 12 formed of a conductive member such as a sheet metal disposed on the back surface of the housing 1 with the housing 1 separated from the side surface of the housing 1. The receiver 14, the liquid crystal 15 for visual recognition, the operation key 16, and the transmitter 17 are provided opposite to each other.

  The casing 1, the first and second antenna elements 10, 12, the receiver 14, the liquid crystal 15, the key 16, and the transmitter 17 are covered with a protective resin casing 20, as shown in FIG. Yes. Moreover, the substantially L-shaped first antenna element 10 has an electrical length of approximately λ / 4 with respect to the operating frequency, and the first corner 2 at the upper end and the side end of the housing 1. Power is supplied from the power source 19 to the power supply unit 11 and operates as a λ / 4 antenna. The substantially L-shaped second antenna element 12 has an electrical length slightly shorter than approximately λ / 4 with respect to the use frequency, and the first corner portion to which the first antenna element 10 is fed. 2 is short-circuited through the short-circuit portion 13 to the grounding portion 18 on the casing 1 in the vicinity.

  Next, the basic operation of the portable wireless device in this embodiment will be described. By short-circuiting the second antenna element 12 in the vicinity of the power feeding portion 11 of the first antenna element 10 and flowing a high-frequency current on the housing depending on the first antenna element 10 to the second antenna element 12, The first and second antenna elements 10 and 12 are electrically coupled at the resonance frequency of the second antenna element 12 slightly higher than the resonance frequency of the first antenna element 10.

  At a frequency slightly lower than the resonance frequency of the second antenna element 12, a current in phase with the current from the first antenna element 10 flows on the second antenna element 12, and the resonance frequency of the second antenna element 12 and At a slightly lower resonance frequency, the current can be strengthened and the gain can be increased. This phenomenon is called effective resonance. Further, at a frequency slightly higher than the resonance frequency of the second antenna element 12, a current having a phase opposite to that of the first antenna element 10 flows on the second antenna element 12, and the currents cancel each other. As the current distribution is changed, the gain decreases. This phenomenon is called unnecessary resonance. Since the first antenna element 10 is a λ / 4 antenna, a high-frequency current flows also on the housing 1, a standing wave also stands on the housing 1, and operates as an integrated antenna to radiate radio waves. . At this time, a large current flows in the corner portion 2 of the housing 1 where the feeding portion 11 of the first antenna element 10 is located, and a current also flows in the second antenna element 12. 12 are electrically coupled. The gain is increased by generating effective resonance at a slightly lower frequency side of the resonance frequency of the second antenna element 12 that is slightly shorter than approximately λ / 4 of the operating frequency, and the gain is decreased by generating unnecessary resonance at the higher frequency side. To do.

  Next, an operation when the portable wireless device according to the present embodiment is used for data communication will be described. When such a portable wireless device is used for data communication as shown in FIG. 4, the resin housing 20 is grasped with the hand 30 and the liquid crystal 15 is visually recognized. At this time, since the lower part of the resin housing 20 is generally gripped by the hand 30, when the antenna is installed at the upper end of the housing 1, the human body is not close to the first and second antenna elements 10, 12, so Due to the effective resonance of the second antenna element 12, good antenna characteristics can be obtained and high-quality data communication can be performed. Here, FIG. 2 shows the frequency characteristics of the gain at the time of data communication as shown in FIG. The horizontal axis F is the frequency, the vertical axis G is the gain, the broken line A is the characteristic in the case of the first antenna element 10 alone (no second antenna element 12), and the solid line B is the characteristic in the case of having the second antenna element 12 Indicates. In the case where the second antenna element 12 is provided, it effectively resonates at a frequency slightly higher than the resonance frequency of the first antenna element 10, and a better characteristic can be obtained than in the case of the first antenna element 10 alone. Therefore, high-quality data communication can be performed. Unnecessary resonance occurs on the slightly higher frequency side of the frequency where effective resonance occurs, but there is no effect because it is outside the use band.

  Next, the operation when the portable wireless device according to the present embodiment is used for voice calls will be described. When such a portable wireless device is used for a voice call, as shown in FIG. 5, the resin housing 20 is grasped by hand, and the head 31 of the human body, specifically, the ear is in close contact with the receiver unit 14. . The second antenna element 12 is disposed in the vicinity of the receiver 14, and the electrical length is increased by the proximity of the human head 31 having a dielectric constant, so that the frequency of effective resonance and unnecessary resonance is low. The SAR can be reduced by moving to the band side and generating unnecessary resonance within the use band. Here, FIG. 3 shows the frequency characteristics of the gain during the voice call as shown in FIG. The horizontal axis F represents frequency, the vertical axis G represents gain, the broken line A ′ represents characteristics of the first antenna element 10 alone (without the second antenna element 12), and the solid line B ′ represents the case where the second antenna element 12 is present. The characteristics of When the second antenna element 12 is present, unnecessary resonance that was outside the use band during data communication by the human body moves into the use band, and the gain is lower than in the case of the first antenna element 10 alone. Therefore, SAR can be reduced. Further, in the present invention, the currents cancel each other and the gain is reduced and the current distribution is changed. In particular, since the current hardly flows in the vicinity of the second antenna element 12 close to the human head, Therefore, the SAR can be expected to be significantly reduced as compared with the method of reducing the SAR by suppressing the transmission power.

  As described above, according to the present embodiment, when a λ / 4 antenna that allows a high-frequency current to flow also on the housing is used, the gain of the second antenna element 12 is increased within the use band due to the effective resonance of the second antenna element 12. Because it is higher, high quality communication can be performed. Further, since the current distribution is changed while slightly reducing the gain by generating unnecessary resonance in the use band during a call, the SAR can be greatly reduced.

  In the first embodiment, the case where the first antenna element 10 uses a λ / 4 antenna has been described. However, the antenna in the present invention is not limited to this, and the frequency used by using the current flowing on the housing is used. Any antenna can be used as long as it is excited by. Moreover, although the 1st, 2nd antenna elements 10 and 12 were shown in the transversal direction of the housing 1, you may arrange | position in the housing longitudinal direction. Further, although the first and second antenna elements 10 and 12 are arranged at the upper end of the housing, the human body does not approach when data communication is performed and may not be the upper end as long as the human body approaches when talking. In addition, the power feeding portion of the first antenna element 10 is preferably at the side end portion so that current flows efficiently on the housing, but it is sufficient that the current can flow on the housing even slightly inside. The first and second antenna elements 10 and 12 are substantially parallel and in the same direction across the housing 1, but the first and second antenna elements 10 and 12 are above the angle formed within ± 90 degrees. Since the phase relationship of the current flowing through the antenna is the same as in the first embodiment and the effect of the present invention is obtained, the first and second antenna elements 10, 12 are parallel if the angle formed by them is within ± 90 degrees. It does not have to be in the same direction. In addition, an antenna may be disposed on the back surface of the resin housing 20, which is the surface opposite to the earpiece 14, but an antenna may be disposed on the upper surface of the resin housing 20. The first and second antenna elements 10 and 12 are shown as substantially L-shaped. However, when space is insufficient, for example, other downsizing methods such as a meander shape or a helical shape are used. Also good.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a diagram illustrating a configuration example of the antenna device according to the present embodiment. As shown in FIG. 7, the antenna device 100 according to the present embodiment includes first and second antenna elements 110 and 120 formed of a conductive member such as a sheet metal. The second antenna element 120 is connected to the grounding portion 124 and the second antenna element 120 in the middle of the microstrip line 122 that connects the grounding portion 124 grounded near the power feeding portion 111 of the first antenna element 110 and the second antenna element 120. A switch 123 is provided as a switching means for turning on / off the connection of the two antenna elements 120.

  When the switch 123 is in the ON state, the second antenna element 120 and the ground unit 124 are connected, and a current also flows through the second antenna element 120. When the switch 123 is in the OFF state, the second antenna element 120 and the grounding part 124 are open, and no current flows through the second antenna element 120 near the operating frequency. That is, it is the same as that the second antenna element 120 is not arranged.

  FIG. 6A is a diagram illustrating the frequency characteristics of the gain during data communication according to the present embodiment, and FIG. 6B is a diagram illustrating the frequency characteristics of the gain during a call according to the present embodiment. . In each figure, the horizontal axis F represents frequency, the vertical axis G represents gain, the same broken line C represents characteristics of the first antenna element alone (no second antenna element), and solid lines D1 and D2 represent the second antenna element. The characteristic when there is an antenna element is shown. F1 indicates a transmission band 1 in the first band, F2 indicates a reception band 1 in the first band, F3 indicates a transmission band 2 in the second band, and F4 indicates a reception band 2 in the second band. For example, in a mobile phone equipped with a GSM system and a W-CDMA system, the case where the DCS band is used as the first band and the W-CDMA band is used as the second band corresponds to this.

  According to the present embodiment, when the switch 123 is in the ON state, similarly to the first embodiment, the gain frequency characteristic D1 is shown during data communication and the gain frequency characteristic D2 is shown during a call. Therefore, when using the first band, it is possible to perform high-quality data communication and a call with reduced SAR. Further, according to the present embodiment, when the switch 123 is OFF, both ends of the second antenna element 120 are opened so that it does not operate as an antenna near the use frequency. The frequency characteristic C of the gain when there is no antenna element 120 is shown.

  That is, in the switch ON state of the present embodiment, the unnecessary resonance of the second antenna element 120 is included in the second band during data communication. However, according to the present embodiment, the unnecessary resonance can be removed. In the second band, when there is no problem with SAR due to low transmission power, this embodiment has an advantage that unnecessary deterioration can be removed.

  A specific example of this embodiment will be described below using the DCS band and the W-CDMA band as usage bands. The DCS band is a frequency band used mainly in urban areas in the world. If it corresponds to the first band in FIG. 6, the transmission band F1 is 1710 to 1785 MHz, and the reception band F2 is 1805 to 1880 MHz. The W-CDMA band is a frequency band used in parts of Japan and Europe. If it corresponds to the second band in FIG. 6, the transmission band F3 is 1920 to 1980 MHz, and the reception band F4 is 2110 to 2170 MHz. It is. Here, according to the present invention, it is possible to increase the gain as shown in FIG. 6 (a) during data communication in the DCS band and reduce the SAR as shown in FIG. 6 (b) during a call. Sometimes unnecessary resonance is included in the W-CDMA band as shown in FIG. According to the present embodiment, if the switch 123 is turned OFF when the W-CDMA band is used, the frequency characteristic C of the gain when the second antenna element 120 in FIG. In addition, in order to switch ON / OFF of the switch 123, it may switch by a user operating a terminal, and a terminal may discriminate | determine and switch automatically simultaneously when a system switches.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a diagram illustrating a configuration example of the antenna device according to the present embodiment. As shown in FIG. 8, the antenna device 200 according to the present embodiment includes first and second antenna elements 210 and 220 formed of a conductive member such as a sheet metal. The second antenna element 220 has a short-circuit portion 221 that is short-circuited in the vicinity of the power feeding portion 211 of the first antenna element 210, and a connection pin 225 for grounding the open end to the housing 201 and a second ground portion 224. A switch 223 is provided as a switching means for turning on / off the connection between the connection pin 225 and the second grounding portion 224 in the middle of the microstrip line 222 that connects the two.

  When the switch 223 is in the ON state, the connection pin 225 and the second grounding part 224 are connected, and both ends of the second antenna element are short-circuited, so that it does not operate as an antenna. That is, since the second antenna element 220 is not arranged, effective resonance and unnecessary resonance due to the second antenna element 220 can be removed as in the second embodiment.

  In the present embodiment, if the switch 223 is turned off, the switch 123 is the same as the switch 123 in the second embodiment. Further, in this embodiment, if the switch 223 is turned on, both ends of the second antenna element 220 are short-circuited so that it does not operate as an antenna. is there. Therefore, as in the second embodiment, high-quality data communication and a call with reduced SAR can be performed when the first band is used, and unnecessary resonance can be removed when the second band is used.

  In addition, in the second embodiment, when both ends of the second antenna element 120 are opened with the switch 123 turned off, it appears as an antenna of a λ / 2 open element for a frequency that is approximately twice the use frequency. If a frequency approximately twice as high is used, there is a possibility of an influence. That is, as a specific example, when the second antenna element 120 is resonated in the GSM band transmission band (880 to 915 MHz) and both ends of the second antenna element 120 are opened according to the second embodiment, In some cases, the DCS band that includes a frequency 1760 to 1830 MHz, which is approximately twice the GSM band transmission band, and the PCS band that has a transmission band of 1850 to 1910 MHz are affected.

  However, in this embodiment, both ends of the second antenna element 220 are short-circuited, so that effective resonance and unnecessary resonance can be removed at all frequencies, and other usable bands can be affected. There is an advantage of becoming.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a diagram illustrating a configuration example of the antenna device according to the present embodiment. As shown in FIG. 9, the antenna device 300 according to the present embodiment includes first and second antenna elements 310 and 320 formed of a conductive member such as a sheet metal, and the second antenna element 320 is the first antenna element 320. A varicap 323 is provided as a variable reactance for frequency adjustment in the middle of the microstrip line 322 connecting the ground part 324 grounded near the power feeding part 311 of one antenna element 310 and the second antenna element 320. It is a feature.

  The varicap is a varactor diode, and operates as a capacitor whose capacitance changes depending on the magnitude of the applied voltage. Therefore, the electrical length of the second antenna element 320 can be changed by changing the voltage applied to the varicap 323. For example, if the voltage applied to the varicap 323 is increased, the capacitance is reduced, so that the electrical length of the second antenna element 320 is shortened, and the resonance frequency moves to the high frequency side.

  In the above embodiment, the varicap 323, which is a variable capacitance, is provided as the variable reactance. However, frequency adjustment may be performed using a variable inductance instead of the varicap 323.

  Using such a portable wireless device, the SAR in the transmission band 1 of the first band and the transmission band 2 of the second band in FIG. 6 is reduced. The frequency characteristic of the gain at the time of data communication using the first band according to the present embodiment is shown in FIG. 6A which is the same as that used in the description of the second embodiment, and according to the present embodiment. The frequency characteristics of the gain during a call using the first band are shown in FIG. 6B, which is the same as that used in the description of the third embodiment. FIG. 6C is a diagram showing the frequency characteristics of the gain at the time of data communication using the second band according to the present embodiment, and FIG. 6D uses the second band according to the present embodiment. It is the figure which showed the frequency characteristic of the gain at the time of a telephone call. In each figure, the horizontal axis F is frequency, the vertical axis G is gain, the same broken line C is the characteristic of the first antenna element alone (no second antenna element), and the solid line D3 is the same as the solid lines D1 and D2. , D4 indicates characteristics when the second antenna element is provided. 6A and 6B, F1 is a transmission band 1 in the first band, F2 is a reception band 1 in the first band, F3 is a transmission band 2 in the second band, and F4 is The reception band 2 in the second band is shown. For example, in a mobile phone equipped with a GSM system and a W-CDMA system, the case where the DCS band is used as the first band and the W-CDMA band is used as the second band corresponds to this.

  In this embodiment, when the voltage applied to the varicap 323 is 0 V, the gain frequency characteristic D1 is shown during data communication using the first band, and the gain frequency characteristic D2 is shown during a call. Therefore, as in the above embodiment, high-quality data communication / call with reduced SAR can be performed when the first band is used.

  Next, when the resonance frequency of the second antenna element 320 is moved to the high frequency side by applying an applied voltage to the varicap 323, the gain frequency characteristic D3 is shown during data communication and the gain frequency characteristic D4 is shown during a call. Show. Therefore, even when the second band is used, high-quality data communication / call with reduced SAR can be performed.

  As described above, according to this embodiment, there is an advantage that not only high-bandwidth high-quality data communication is possible but also a call with reduced SAR is possible in multiband.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a diagram illustrating a configuration example of the antenna device according to the present embodiment. 6 (a) to 6 (d), which are the same as those used in the description of the second and fourth embodiments, show the frequency characteristics of the gain according to this embodiment.

  As shown in FIG. 10, the antenna device 400 according to the present embodiment includes first and second antenna elements 410 and 420 formed of a conductive member such as a sheet metal, and the second antenna element 420 is the first antenna element 420. Between the connection pin 425 and the conductive pattern 426 for connecting the open end to the conductive pattern 426 provided on the housing 401, which has a short-circuit portion 421 that is short-circuited in the vicinity of the power supply portion 411 of one antenna element 410. Further, in order to make the electrical length of the second antenna element 420 variable, a switch 423 is provided as switching means for turning on / off the connection with the conductive pattern 426.

  When the switch 423 is in the ON state, the conductive pattern 426 and the second antenna element 420 are connected, so that the electrical length of the second antenna element 420 becomes longer, and the switch 423 is longer than in the OFF state. The resonance frequency of the second antenna element 420 moves to the low frequency side.

  In the present embodiment, when the switch 423 is in the ON state, the voltage applied to the varicap 323 in the fourth embodiment is the same as the state in which the applied voltage is 0 V (D1 in FIG. 6A and FIG. 6B). D2). Further, in this embodiment, when the switch 423 is in the OFF state, it is the same as the state in which the voltage applied to the varicap 323 in the fourth embodiment is applied (D3 in FIG. 6C, FIG. 6D). D4). Therefore, as in the fourth embodiment, according to the present embodiment, there is an advantage that not only high-bandwidth and high-quality data communication is possible, but also a call with reduced SAR in multiband is possible.

  As described above, in the second to fifth embodiments, the merits of making the electrical length of the second antenna element variable are shown, but the characteristic degradation due to unnecessary resonance of the second antenna element is shown. Even in the use band, there is no need to change the electrical length as long as the characteristics can be tolerated. Further, the description has been made assuming a multi-band antenna, but if necessary, it may be used for a single-band antenna.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described with reference to the drawings. FIG. 11 is a diagram illustrating a configuration example of the antenna device according to the present embodiment. As shown in FIG. 11, the antenna device 500 according to the present embodiment includes first and second antenna elements 510 and 520 formed of a conductive member such as a sheet metal.

  Here, in the portable wireless device, from the viewpoint of protecting the liquid crystal from static electricity, a conductive member 530 such as a copper foil grounded to the housing 501 by the grounding portion 531 is often disposed around the liquid crystal. In this embodiment, the grounding portion 531 is short-circuited to the housing 501 near the power feeding portion 511 of the first antenna element 510 and the short-circuiting portion 521 of the second antenna element 520 is connected near the grounding portion 531. As a result, the first and second antenna elements 510 and 520 are coupled.

  The second antenna element 520, which is slightly shorter than approximately λ / 4 of the operating frequency, provides good characteristics during data communication where the human body is not close to each other, so that high-quality communication can be performed. Since the unnecessary resonance moves into the use band during a call close to, the gain is lowered and the current distribution is changed, so that the SAR can be greatly reduced.

  Therefore, according to the present embodiment, when the second antenna element 520 is configured, the second antenna element 520 is grounded by being integrally designed with a conductive member such as a copper foil for preventing static electricity of the liquid crystal. Therefore, there is an advantage that cost reduction can be realized without requiring a new component such as a connection pin.

  INDUSTRIAL APPLICABILITY The present invention can be used for a built-in portable radio antenna and a portable radio mounted on a portable radio that communicates voice, data, and the like.

It is a perspective explanatory view showing an embodiment of an antenna for portable radios and a portable radio concerning the present invention. It is a frequency characteristic figure of the gain at the time of data communication of the antenna for portable radios concerning the present invention, and a portable radio. It is a frequency characteristic figure of the gain at the time of the telephone call of the antenna for portable radios and a portable radio concerning the present invention. It is explanatory drawing which shows the use condition at the time of the data communication in embodiment of the antenna for portable radios which concerns on this invention, and a portable radio. It is explanatory drawing which shows the use condition at the time of the telephone call in embodiment of the antenna for portable radios which concerns on this invention, and a portable radio. It is explanatory drawing which shows the frequency characteristic of the gain in embodiment of the antenna for portable radios which concerns on this invention, and a portable radio. It is a perspective explanatory view showing a second embodiment of an antenna for a portable wireless device and a portable wireless device according to the present invention. It is a perspective explanatory view showing a third embodiment of an antenna for a portable wireless device and a portable wireless device according to the present invention. It is a perspective explanatory view showing a 4th embodiment of an antenna for portable radios and a portable radio concerning the present invention. It is a perspective explanatory view showing a 5th embodiment of an antenna for portable radios and a portable radio concerning the present invention. It is a perspective explanatory view showing a 6th embodiment of an antenna for portable radios and a portable radio concerning the present invention.

Explanation of symbols

1, 101, 201, 301, 401, 501 Housing 2 Corners 10, 110, 210, 310, 410, 510 First antenna element 11, 111, 211, 311, 411, 511 Power feeding unit 12, 120, 220, 320, 420, 520 Second antenna element 13, 121, 221, 321, 421 Short-circuit part 14 Reception part 15 Liquid crystal 16 Operation key 17 Transmission part 18, 124, 324, 521, 531 Ground part 20 Resin housing 30 Hand 31 Human head 100, 200, 300, 400, 500 Antenna device 122, 222, 322 Microstrip line 123, 223, 423 Switch 224 Second grounding part 225, 425 Connection pin 323 Varicap 426 Conductive pattern 530 Conductive Element

Claims (10)

A portable radio antenna having first and second antenna elements in a housing containing a radio unit,
The first antenna element is excited at a working frequency using a current flowing on the housing, and has a power feeding unit for exciting the first antenna element at a side end of the housing,
The second antenna element is disposed opposite to the first antenna element at a position closer to the human head than the first antenna element during a call, and is short-circuited near the feeding point of the first antenna element. And an electric length shorter than that of the first antenna element.   2. The portable radio antenna according to claim 1, wherein the first antenna element has an electrical length of approximately [lambda] / 4 of the operating frequency.   The antenna for a portable wireless device according to claim 1 or 2, wherein the position close to the human head is near a receiver.   4. The portable radio antenna according to claim 1, wherein the first and second antenna elements are arranged at an upper end portion of the casing. 5.   5. The portable radio device according to claim 1, wherein the second antenna element includes means for changing an electrical length of the second antenna element. 6. antenna.   The second antenna element is configured to turn on / off the connection between the short-circuit portion and the ground portion between the short-circuit portion and the ground portion provided in the housing as means for changing the electrical length. 6. The portable radio antenna according to claim 5, further comprising switching means for turning off.   The second antenna element is provided with a variable reactance that makes a reactance variable between the short-circuit portion and the grounding portion provided in the housing as a means for making the electrical length variable. The antenna for a portable radio according to claim 5, characterized in that   The second antenna element is provided as a means for changing the electrical length between the open end of the second antenna element and a second grounding portion provided in the housing. 6. The portable radio antenna according to claim 5, further comprising switching means for turning on / off a connection between the second grounding portion and the second grounding portion.   The second antenna element, as means for changing the electrical length, is provided between the open end of the second antenna element and the conductive pattern provided on the housing. 6. The portable radio antenna according to claim 5, further comprising switching means for turning on / off the connection between the conductive pattern and the conductive pattern.   A portable wireless device comprising the portable wireless device antenna according to any one of claims 1 to 9.

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