JP4728696B2 - Antenna for information terminal - Google Patents

Description

  The present invention relates to an information terminal antenna, and more particularly to an information terminal antenna including a plurality of antennas for receiving radio signals of different frequency bands.

  Information terminals such as PDAs (Personal-Digital-Assistance) and mobile phones provide character information services using frequency bands for voice communications, and exchange information with other terminals at higher speeds. A GPS (Global-positioning-System) has been installed in order to install a wireless LAN (Local-Area-Network) or to provide weather information and news based on location information. Multiple wireless media have become available on one terminal. In connection with this, many antennas are mounted on one terminal.

  The radio wave used for GPS has a center frequency of 1.57542 MHz (hereinafter referred to as 1.5 GHz band), and the frequency used for the wireless LAN is 2.4 to 2.5 GHz (hereinafter referred to as 2.45 GHz band). ) Or 5.15 to 5.25 GHz (hereinafter referred to as the 5.2 GHz band).

  As shown in FIG. 14, in the conventional terminal, for example, a wireless LAN transmission / reception antenna 30 and a reception antenna 31 are arranged, cables 32a and 32b are pulled out from each, and connected to a radio (not shown) provided in the terminal. Diversity scheme is taken. Furthermore, for example, when an antenna that receives radio waves in different frequency bands, such as a GPS antenna, is to be mounted on an information terminal, there is little space for mounting in the first place due to the demand for miniaturization of the terminal. Due to the demand for expansion, there has been a problem of further reduction in mounting space, and miniaturization of the antenna is highly demanded.

  In addition, a signal exchanged by an antenna needs to be connected to a radio device provided in the terminal, and the number of antennas to be mounted must be wired using cables. In general, high-frequency cables are expensive, leading to increased cost of the terminal. Furthermore, there are some troublesome cable installations in the terminal assembly process, and damage to the cables in the assembly process and cables that pass through the hinges. However, the problem that it is damaged by the operation of the hinge part has occurred. For that reason, it is desirable to reduce the number of cables as much as possible. Therefore, it is conceivable that the wireless LAN reception antenna and the GPS antenna are integrated and the cable is omitted. In such a configuration, as described in Patent Document 1, for example, a proposal has been made to synthesize a radio signal with a signal synthesis circuit and then send it to a radio.

In Patent Document 1, as shown in FIG. 15, a signal transmission terminal of an antenna 101 that receives information from a satellite and a signal transmission terminal of an antenna 102 that receives information from the ground are connected via a line 103. A structure for attaching the signal transmission cable 104 in the middle of 103 is described. In addition, since the received signal from the satellite has a lower power level than the received signal from the ground, two amplifiers 105 and 106 are connected in series to the signal transmission terminal of the antenna 101 that receives information from the satellite. . Further, in line 103, filter 107 is connected in series to the signal transmission end of amplifier 105 at the first stage, and filter 108 for preventing oscillation is connected in series to the signal transmission end of antenna 102 that receives information from the ground. In addition, capacitors 109 and 110 for cutting a direct current component are connected in series to the signal sending ends of the amplifier 106 at the subsequent stage and the filter 108 on the antenna 102 side that receives information from the ground.
JP-A-9-139625 JP 2004-236014 A Proceedings of the 1996 IEICE General Conference, Volume 1, pages 610, 611

  In the information terminal antenna shown in FIG. 15, the oscillation that occurs when two antennas 101 and 102 having different frequencies are connected can be prevented by the filter 108.

However, with the approach, integration, and miniaturization of the two antennas 101 and 102 on the same substrate, the isolation between the antennas is deteriorated and only about 10 dB can be secured, and only 18 dB can be obtained even if technical solutions are made. . Patent Document 2 also describes that it is difficult to achieve isolation between antenna patterns when a plurality of antenna patterns are formed on the same plane. In fact, the inventors have 20 samples, and a patch that can receive multiple signals (1.5 GHz band and 2.5 GHz band) is placed on a 32 mm square dielectric substrate to provide isolation between antennas. Actually measured. As a result, the average value was 18.3 dB and the standard deviation was 1.4 dB.
As a result, the signals amplified by the amplifiers 105 and 106 are radiated to the outside through the line 103 to the antenna 102 that receives information from the ground, and further enter the antenna 101 that receives information from the satellite. Therefore, for example, when the antenna that receives information from the satellite is for GPS, there is a problem that it leads to a ranging error.

  In particular, when the amplification levels of the amplifiers 105 and 106 are required to be as high as 30 dB and 40 dB, for example, the problem of deterioration in isolation between antennas appears remarkably. Such degradation of isolation appears as degradation of the received signal similar to the effect of multipath as described in Non-Patent Document 1, for example.

  The problem to be solved by the present invention is to provide an information terminal antenna having a structure that suppresses deterioration of a received signal due to deterioration of isolation caused by the approach and integration of a plurality of antennas.

An information terminal antenna according to a first aspect of the present invention for solving the above-described problems includes a plurality of antennas that receive radio signals having different power levels and different frequency bands, and received power among the plurality of antennas. And at least one signal amplifying means for amplifying a transmission signal of a first antenna that receives a first radio signal having a low frequency, and the first radio signal of the plurality of antennas has a frequency different from that of the first radio signal. And at least one signal synthesizing unit that synthesizes a transmission signal of at least one other antenna that receives another radio signal having high received power and an output signal of the signal amplifying unit, and the signal amplifying unit and the signal synthesizing unit X (dB) is the isolation of the path from the other antenna to the first antenna without passing through the means, and the signal amplifying means is further used. The value obtained by subtracting the direction of isolation of terminals sending the signal of the further antenna is input from the terminal to which the output signal is the input of said signal amplification means of said signal combining means when the Y (dB) from, The isolation of the path from the other antenna to the first antenna, the gain of the signal amplifying means, and the relationship of X ≦ 18 (dB) and XY ≧ 25 (dB); wherein said signal synthesizing means is isolation setting, the gain of the first radio signal - sufficient isolation to keep the ripple of frequency characteristics below 1dB is ensured.

An information terminal antenna according to a second aspect of the present invention is characterized in that, in the first aspect, the signal synthesizing means is composed of a combination of a high-pass filter and a low-pass filter having at least one resonator. To do.

Third information terminal antenna according to the embodiment of the present invention, in a first aspect, the signal combiner, that it is constituted by a combination of filters and Wilkinson power combiner having at least one resonator Features.

An information terminal antenna according to a fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, each of the plurality of antennas is a planar patch antenna .

An information terminal antenna according to a fifth aspect of the present invention is the information terminal antenna according to any one of the first to fourth aspects, wherein the first antenna is an antenna that receives a signal using satellite communication. The antenna is an antenna that receives a terrestrial signal .

  ADVANTAGE OF THE INVENTION According to this invention, even if there exists degradation of the isolation between several antennas by size reduction of an antenna, characteristic deterioration as an antenna apparatus can be suppressed easily, and size reduction of the antenna for information terminals is attained. .

  The present inventor has prepared an information terminal antenna in which a GPS antenna and a wireless LAN antenna are formed on the same substrate. Then, the radio wave signal received by the GPS antenna is amplified, circulated to the wireless LAN antenna, and further incident on the GPS antenna. The 1.5 GHz gain-frequency characteristics in this case were examined, and FIG. Measurement results as shown by the solid line were obtained.

  According to the result, a ripple appears in the gain-frequency characteristic in the measured characteristic line indicated by the solid line with respect to the ideal characteristic line indicated by the broken line, thereby degrading the GPS signal in the information terminal antenna. I found out that That is, it has been clarified that the occurrence of the ripple is one of the factors that cause the GPS reception signal to deteriorate.

  An embodiment of the present invention for reducing the ripple will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view showing an external appearance of an information terminal antenna according to a first embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram thereof.

  In FIG. 1, a first antenna 1 that receives radio waves of a frequency of 1.5 GHz used for GPS and a second antenna 2 that receives radio waves of a frequency of 2.45 GHz used for a wireless LAN are dielectrics. It is formed on the substrate 3. A circuit board (not shown) is formed under the dielectric substrate 3, and a cable 5a for transmitting a signal to a signal processing unit (not shown) is connected to the circuit board (not shown). . A connector 6a is attached to the tip of the cable 5b.

  An amplifier 10 and a signal synthesis circuit 11 as shown in FIG. 2 are formed on a circuit board (not shown), and an input terminal of the amplifier 10 is connected to a signal transmission terminal of the first antenna 1. In the signal synthesis circuit 11, the output terminal of the amplifier 10 is connected to the first input terminal 11a, the signal transmission terminal of the second antenna 2 is connected to the second input terminal 11b, and the output A cable conductor is connected to the terminal 11c.

The first antenna 1 and the second antenna 2 are planar patch antennas, and are connected to the amplifier 10 and the signal synthesis circuit 11 through feed pins (not shown) that penetrate the dielectric substrate 3, respectively.
In FIG. 1, reference numeral 30 denotes another transmission / reception antenna 30 attached to the display device 33 on which the dielectric substrate 3 is mounted, reference numeral 34 denotes an input device attached to the display device via a hinge, and reference numeral 5 b denotes the transmission / reception antenna 30. A cable 5b connected to, and a reference numeral 6a indicate a connector 6b connected to the tip of the cable 5b.

  1 and 2, the isolation between the first and second antennas 1 and 2 is defined in the direction from the second antenna 2 to the first antenna 1 indicated by a broken line, and the gain of the amplifier 10 is the first. The direction from the antenna 1 to the signal synthesis circuit 11 is defined, and the isolation of the signal synthesis circuit 11 is defined from the first input terminal 11a to the second input terminal 11b.

  The characteristic line shown by the solid line in FIG. 16 has ripples because it circulates between the antennas 1 and 2 and is input to the amplifier 10 again as indicated by the broken line in FIG. It is.

  The 1.5 GHz band signal that passes between the antennas 1 and 2 and is input to the amplifier 10 again is obtained by isolating the 1.5 GHz band between the antennas 1 and 2, the 1.5 GHz band gain of the amplifier 10, and the signal synthesis circuit. It is quantified by a loop gain composed of 11 1.5 GHz band isolations.

  If the loop gain is −∞, the 1.5 GHz band signal received by the first antenna 1 is amplified by the amplifier 10 and then propagated only to the system output to the cable 5 via the signal synthesis circuit 1, There is no radiation from the second antenna 2 to the outside. However, the actual loop gain becomes larger or smaller depending on the frequency than the gain in the case of −∞ due to the relationship between the amplitude and the phase of the sneak signal from the amplifier 10 to the second antenna 2.

  In order to quantify the phenomenon that the 1.5 GHz band signal wraps around between the antennas 1 and 2 and affects the loop gain, the gain of the amplifier 10 when the loop gain is set to the horizontal axis and the loop gain is set to −∞. When the gain difference of the amplifier 10 in consideration of the wraparound is plotted on the vertical axis, it is as shown in FIG.

The gain difference on the vertical axis in FIG. 3 indicates that the 1.5 GHz band direct wave Asin (x) received from the satellite and the second antenna 2 are incident on the first antenna 2 via the signal synthesis circuit 11. It shows the difference between the loop gain, which is the coefficient of sin (x + α) on the right side obtained by the following formula obtained by superimposing the 5 GHz band sneak wave Bsin (x + t), and the gain when the loop gain is −∞. . That is, when there is no sneak wave from the second antenna 2 to the first antenna 1, the gain difference is 0 dB. In the following equation, t represents a phase difference.

  In FIG. 3, it can be seen that the gain difference increases as the loop gain increases. For example, when the loop gain is degraded to −10 dB, it may be 2 to 2.5 dB larger or smaller than the gain difference (0 dB) that is originally desired. The inventor has confirmed that the ripple appears larger or smaller with respect to the reference characteristic line indicated by the broken line in FIG. 16 and that the gain difference is preferably suppressed to 0.5 dB or less with respect to the reference characteristic line. Yes. Therefore, in consideration of the difference between increase and decrease with respect to the reference characteristic line indicated by the broken line in FIG. 16, the ripple needs to be suppressed to a range that is twice the preferable gain difference, that is, 1 dB or less.

  Therefore, in order to reduce the ripple in the information terminal antenna to 1 dB or less, the gain difference in FIG. 3 needs to be smaller than 0.5 dB. For this purpose, the phase difference of the sneak signal to the first antenna 1 is the worst. In the case of 0 degrees, the loop gain needs to be −25 dB or less.

  Here, the isolation between the antennas 1 and 2 is X (dB), and the value obtained by subtracting the isolation of the signal synthesis circuit 11 from the gain of the amplifier 10 is Y (dB).

  If the isolation X is larger than 25 dB, the ripple can be suppressed to 1 dB or less even if Y is 0 dB. On the other hand, with the proximity and integration of the combined antennas, the isolation X is 18 dB at most, which is less than that (X ≦ 18). In this case, if the information terminal antenna is configured so that X−Y ≧ 25 (dB), the gain difference in FIG. 3 can be reduced to 0.5 dB or less, and the ripple is reduced to 1 dB or less of the allowable range. It is possible to suppress.

  If such a relationship between X and Y is shown, the loop gain must be secured so as to be within the hatched range shown in FIG. Further, since isolation is not ensured in the range of XY <25 (dB), it is affected by the ripple of the gain-frequency characteristic.

  In FIG. 4, for example, when the isolation X between the antennas 1 and 2 is 12 dB and the gain of the amplifier 10 is 30 dB, if the isolation of the signal synthesis circuit 11 is 43 dB, Y = −13 dB, and X− Since Y ≧ 25, the ripple can be suppressed to 1 dB or less, and a high-quality information terminal antenna can be obtained.

  FIG. 5 shows a specific example of the signal synthesis circuit 11 with an isolation of 43 dB. A 1.5 GHz band low-pass filter 12 is connected between the first input end 11a and the output end 11c, and the second input A 2.45 GHz high-pass filter 13 is connected between the end 11b and the output end 11c.

  The low-pass filter 12 is a connection of 4.7 nH first and second inductances 12a and 12b and first and second inductances 12a and 12b connected in series between the first input terminal 11a and the output terminal 11c. It has a 2 pF capacitor 12c connected between the point and the ground line GND and a third inductance 12d of 2.2 nH.

  The high-pass filter 13 has a 1pF second and third capacitors 13a and 13b connected in series between the second input end 11b and the output end 11c, and a connection point between the second and third capacitors 13a and 13b. And a ground capacitor GND and a fourth capacitor 13c of 2.8 pF and a fourth inductance 13d of 3.7 nH.

  With this configuration, the signal synthesis circuit 11 ensures 43 dB isolation. A portion surrounded by a thick solid line is a resonator composed of LC.

  FIG. 6A shows the frequency-transmission characteristics of a signal propagating between the first input terminal 11a and the second input terminal 11b of the signal synthesis circuit 11 shown in FIG. FIG. 6B shows frequency-transmission characteristics of a signal propagating between the first input terminal 11a and the output terminal 11c of the signal synthesis circuit 11 shown in FIG. FIG. 6C shows the frequency-transmission characteristics of a signal propagating between the second input terminal 11b and the output terminal 11c of the signal synthesis circuit 11 shown in FIG.

  Note that the high-pass filter 13 and the low-pass filter 12 shown in FIG. 5 are not limited to the above values. Further, the number of resonators for ensuring isolation is not limited to one, and a plurality of resonators may be provided.

  The solid line shown in FIG. 7 has the configuration shown in FIG. 5 and is obtained by adjusting the values of the capacitors 12c, 13a, 13b, and 13c and the inductances 12a, 12b, 12d, and 13d described above. The broken line is a target characteristic line. According to FIG. 7, the ripple can be suppressed to 1 dB or less.

  In FIG. 1, the first antenna 1 and the second antenna 2 are formed on the same substrate. However, as shown in FIG. 8, the first antenna 1 is formed on the first dielectric substrate 3a. A structure in which the second antenna 2 is formed on the second dielectric substrate 3b and these dielectric substrates 3a and 3b are mounted on a circuit substrate (not shown) may be employed. Further, the first antenna 1 and the second antenna 2 may be overlapped or integrally formed.

(Second Embodiment)
FIG. 9 is a circuit diagram showing an information terminal antenna according to a second embodiment of the present invention. 9, the same reference numerals as those in FIG. 2 denote the same elements.

  In FIG. 9, two amplifiers 10a and 10b are connected in series between the signal transmission end of the first antenna 1 and the first input end 11a of the signal synthesis circuit 11, and the first-stage amplifier 10a and the subsequent-stage amplifier 10b. A band pass filter 14 for removing signals in unnecessary frequency bands is connected in series. Similarly to the first embodiment, the signal synthesis circuit 11 includes a 1.5 GHz band low-pass filter 12 connected between the first input terminal 11a and the output terminal 11c, a second input terminal 11b, and an output terminal. The high-pass filter 13 for 2.45 GHz band connected between 11c.

  Even in this case, for example, if the isolation between the first antenna 1 and the second antenna 2 is 12 dB, the gains of the amplifiers 10 a and 10 b are 30 dB, and the isolation of the signal synthesis circuit 11 is 43 dB, this is obtained. The ripple generated in the gain-frequency characteristic line in the 1.5 GHz band is 1 dB or less.

  Note that the isolation of the signal synthesis circuit 11 may be greater than 43 dB.

(Third embodiment)
FIG. 10 is a circuit diagram showing an information terminal antenna according to a second embodiment of the present invention. 10, the same reference numerals as those in FIG. 2 indicate the same elements.

  In FIG. 10, two amplifiers 10 a and 10 b are connected in series between the signal transmission end of the first antenna 1 and the first input end of the signal synthesis circuit 11. The output terminal of the subsequent amplifier 10 b is connected to the first input terminal 11 a of the signal synthesis circuit 11.

  The signal synthesis circuit 11 includes a low-pass filter 12 and a high-pass filter 13 formed on the circuit board 4 and a Wilkinson power synthesis circuit 16 connected between the filters 12 and 13.

  The Wilkinson type power combining circuit 16 includes a microstrip line 16a formed on a dielectric layer, a resistor 16b is connected between both ends thereof, and a central portion thereof is connected to an output end 11c of the signal combining circuit 11. It is connected. One end of the microstrip line 16a is connected to the first input terminal 11a of the signal synthesis circuit 11 via the low-pass filter 12, and the other end is connected to the second input terminal 11b of the signal synthesis circuit 11 via the high-pass filter 13. It is connected to the.

  The Wilkinson type power combining circuit 16 is easy to propagate a signal from one end of the microstrip line 16a to the output end 11c, but is difficult to propagate a signal to the other end, so that isolation is achieved. It is a circuit suitable for.

  Also in this case, the isolation of the signal synthesis circuit 11 is a value that suppresses the ripple of the gain-frequency characteristic to 1 dB or less, as in the first embodiment.

(Fourth embodiment)
FIG. 11 is a signal combining circuit for an information terminal antenna according to the fourth embodiment of the present invention, and the connection of two antennas 1, 2 and amplifiers 3 with different frequencies is the same as in the first embodiment. Yes.

  A signal synthesis circuit 11 shown in FIG. 11 includes a Wilkinson power synthesis circuit 17 and a high-pass filter 18 formed on a dielectric layer.

  The Wilkinson type power combining circuit 17 includes a microstrip line 17a formed on a dielectric substrate, a resistor 17b is connected between both ends thereof, and a central portion thereof is connected to an output end 11c of the signal combining circuit 11. It is connected. One end of the microstrip line 17a is connected to the first input terminal 11a in the signal synthesis circuit 11, and the other end is connected to the second input in the signal synthesis circuit 11 via the high-pass filter 18. It is connected to the end 11b.

  The high-pass filter 18 includes first and second capacitors 18a and 18b connected in series between the end of the microstrip line 17a of the Wilkinson power combining circuit 17 and the second input terminal 11b of the signal combining circuit 11. A third capacitor 18c and an inductance 18d are connected between the connection point between the capacitors 18a and 18b and the ground line GND. In the present embodiment, the first and second capacitors 18a and 18b are 1 pF, the third capacitor 18c is 3.5 pF, and the inductance 18d is 3.9 nH.

  FIG. 12A shows the frequency-transmission characteristics of a signal propagating between the first input terminal 11a and the second input terminal 11b of the signal synthesis circuit 11 having such a configuration, and FIG. FIG. 12C shows the frequency-transmission characteristics of a signal propagating between the first input terminal 11a and the output terminal 11c of the synthesis circuit 11, and FIG. 12C shows the relationship between the second input terminal 11b and the output terminal 11c of the signal synthesis circuit 11. The frequency-transmission characteristic of the signal which propagates is shown. In this case, in the signal synthesis circuit 11, the isolation from the first input terminal 11a to the second input terminal 11b is 43 dB. However, in FIG. 12, the thickness of the dielectric substrate (not shown) on which the microstrip line 17a constituting the Wilkinson type power combining circuit 17 of FIG. 11 is formed is 0.8 mm, and the gold foil constituting the microstrip line 17a is formed. In this example, the thickness is 18 μm, the dielectric constant of the dielectric substrate is 4.3, and the length from one end to the center of the pattern of the microstrip line 17a is 27 mm.

(Fifth embodiment)
FIG. 13 is a circuit diagram showing a fifth embodiment of the present invention. The same reference numerals as those in FIG. 9 denote the same elements.

  In FIG. 13, two amplifiers 10a and 10b are connected in series between the signal transmission end of the first antenna 1 for GPS and the first input end 11a of the signal synthesis circuit 11, and the first stage amplifier 10a and the subsequent stage are connected. Between the amplifiers 10b, a band pass filter 14 for removing signals in unnecessary frequency bands is connected in series.

  The output terminal of the subsequent amplifier 10b is connected to the first input terminal 11a of the first signal synthesis circuit 11, and the second input terminal 11b of the first signal synthesis circuit 11 is connected to the second input terminal 11b for the wireless LAN. The signal transmission terminal of the second antenna 2 is connected, and the first input terminal 21a of the second signal synthesis circuit 21 is connected to the output terminal 11c.

  The second input terminal 21b of the second signal synthesis circuit 21 receives a third antenna that receives radio waves in a frequency band higher than the 2.45 GHz band wireless LAN signal, for example, radio waves in the 5.2 GHz band. 9 is connected. An output terminal 23 is connected to the output terminal 21 c of the second signal synthesis circuit 21. In general, a radio wave received by a 5.2 GHz band wireless LAN antenna has a higher power level than a radio wave received by a GPS antenna.

  The first signal synthesis circuit 11 is connected between the first input terminal 11a and the output terminal 11c, and passes between a low-pass filter 12 that passes a 1.5 GHz band signal, and between the second input terminal 11b and the output terminal 11c. And a high-pass filter 13 that allows signals of 2.45 GHz band to pass therethrough. The second signal synthesis circuit 21 is connected between the first input terminal 21a and the output terminal 21c, and passes through a low-pass filter 22 that passes a signal of 1.5 GHz band and 2.45 GHz band, and a second input terminal 21b. And a high-pass filter 23 connected between the output terminal 21c and passing a 5.2 GHz signal.

  In the isolation of the first and second signal synthesis circuits 11 and 21, as in the first embodiment, the magnitude of the ripple on the 1.5 GHz gain-frequency characteristic line with the lowest power level is 1 dB or less. The high-pass filters 13 and 23 and the low-pass filters 12 and 22 are configured so that the measurement error due to GPS is reduced.

FIG. 1 is a perspective view showing an appearance of an information terminal according to the first embodiment of the present invention. FIG. 2 is a circuit diagram of the information terminal antenna according to the first embodiment of the present invention. FIG. 3 is a diagram showing the relationship between the loop gain and the gain difference in the information terminal antenna according to the embodiment of the present invention. FIG. 4 is a diagram showing the relationship between the antenna isolation X and the loop gain Y in the amplifier and signal synthesis circuit according to the embodiment of the present invention. FIG. 5 is a circuit configuration diagram showing an example of a signal synthesis circuit of the information terminal antenna according to the first embodiment of the present invention. FIGS. 6A to 6C are frequency-transmission characteristics diagrams of an information terminal antenna including the signal synthesis circuit shown in FIG. FIG. 7 is a gain-frequency characteristic diagram of an output signal in the 1.5 GHz band of the information terminal antenna according to the first embodiment of the present invention. FIG. 8 is a perspective view showing an appearance of the information terminal according to the first embodiment of the present invention. FIG. 9 is a circuit diagram of the antenna for information terminals according to the second embodiment of the present invention. FIG. 10 is a circuit diagram of an information terminal antenna according to a third embodiment of the present invention. FIG. 11: is a block diagram which shows the signal synthesis circuit of the antenna for information terminals which concerns on 4th Embodiment of this invention. 12A to 12C are frequency-transmission characteristics diagrams of an information terminal antenna including the signal synthesis circuit shown in FIG. FIG. 13 is a circuit diagram showing an information terminal antenna according to a fifth embodiment of the present invention. FIG. 14 is a perspective view showing a conventional information terminal antenna. FIG. 15 is a circuit diagram showing a conventional information terminal antenna. FIG. 16 is a gain-frequency characteristic diagram of an output signal in a 1.5 GHz band in a conventional information terminal antenna.

Explanation of symbols

1: first antenna 2: second antenna 3: dielectric substrates 5a, 5b: cables 6a, 6b: connector 10: amplifier 11: signal synthesis circuit 12: low pass filter 13: high pass filter 14: band pass filter 16, 17: Wilkinson power combiner circuit 18: High-pass filter 21: Signal combiner circuit 30: Transmit / receive antenna 31: Receive antenna 32a, 32b: Cable 33: Display device 34: Input device 35a, 35b: Connector

Claims (5)

A plurality of antennas for receiving radio signals of different frequency bands and different power levels;
At least one signal amplifying means for amplifying a transmission signal of a first antenna that receives a first radio wave signal having a low reception power among the plurality of antennas;
Of the plurality of antennas, a signal transmitted from at least one other antenna that receives a different radio signal having a frequency different from that of the first radio signal and having a higher reception power than the first radio signal, and the signal amplification means Comprising at least one signal synthesis means for synthesizing the output signal;
The isolation of the path from the other antenna to the first antenna without passing through the signal amplifying means and the signal synthesizing means is set to X (dB), and the gain of the signal amplifying means is When the value obtained by subtracting the isolation in the direction of the terminal to which the output signal of the other antenna is input from the terminal to which the output signal of the signal amplifying means is input is Y (dB), X ≦ 18 (dB) and as the relationship X-Y ≧ 25 (dB) are established, the isolation of the path from the another antenna to the first antenna, the gain of the signal amplifying means, and wherein said signal synthesizing means Isolation is set, and sufficient isolation is secured to suppress the ripple of the gain-frequency characteristic of the first radio signal to 1 dB or less. Antenna for broadcast terminal.   2. The information terminal antenna according to claim 1, wherein the signal synthesizing unit includes a combination of a high-pass filter and a low-pass filter having at least one resonator.   2. The information terminal antenna according to claim 1, wherein the signal synthesizing unit is configured by a combination of a filter having at least one resonator and a Wilkinson power combiner.   The information terminal antenna according to any one of claims 1 to 3, wherein each of the plurality of antennas is a planar patch antenna.   5. The method according to claim 1, wherein the first antenna is an antenna that receives a signal using satellite communication, and the another antenna is an antenna that receives a terrestrial signal. The antenna for information terminals described in 1.

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