JP3407837B2 - Portable radio - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable wireless device which resonates at two frequencies, has a wide band, has a small loss in a matching circuit, and has a high gain.

[0002]

2. Description of the Related Art FIG. 14 shows an example of a conventional portable wireless device.
In this example, the feeding circuit impedance of the linear antenna 101 and the input impedance of the antenna terminal 106 of the internal wireless circuit 103 are matched by the matching circuit 102. That is, 101 is a linear antenna, 102 is a matching circuit, 103 is an internal wireless circuit, 104 is a housing, 105 is a feeding point of the antenna, 106 is an antenna terminal of the internal wireless circuit, 107 is a linear antenna and the internal wireless circuit. It is a cable to connect.

Conventionally, the impedance of the antenna terminal of the internal radio circuit 103 is generally 50Ω, and the matching circuit 102 is required as in this example except when the antenna has a quarter wavelength. In particular, in order to increase the antenna gain, it is preferable that the length of the linear antenna 101 be close to ½ wavelength (Reference (1): Tsunekawa et al .: “Multi-wave gain and housing length of small radio antenna”). Relationship "The Institute of Electronics, Information and Communication Engineers, Journal of the Institute of Electronics, Information and Communication Engineers B-II vol.J75-B-II No.10 pp705-707 1992
October year). When the length of the antenna 101 is close to ½ wavelength, the impedance of the feeding point of the antenna 101 is high, so a conversion circuit of high impedance and 50Ω, that is, the matching circuit 102 is required.

[0004]

With such a structure, loss occurs in the matching circuit 102 and the gain of the antenna is lowered. Furthermore, in order to resonate at two frequencies, a two-stage LC circuit or the like is required, and the circuit configuration of the matching circuit 102 becomes more complicated, resulting in more loss.
Further, in this case, the band is also narrow, and when a wide band is required, the Q of the matching circuit 102 has to be lowered, and the loss is further increased.

Therefore, in the conventional portable radio device, the linear antenna 101 and the antenna terminal 106 of the internal radio circuit 103 are provided.
A matching circuit 102 is required between the two, and in order to realize two resonances and a wide band, a more complicated matching circuit 1 having a low Q is used.
However, there is a drawback in that a large loss occurs and the antenna gain is extremely reduced. The object of the present invention is to solve such a problem, and it is possible to match the linear antenna with the internal circuit without using a matching circuit with a lumped constant, and to obtain a high gain. An attempt is made to provide a portable wireless device having the same.

[0006]

According to the present invention, an internal wireless circuit is housed in a housing, a linear antenna is arranged outside the housing, and the linear antenna and the internal wireless circuit are electrically connected. In the configured portable wireless device, the feeding point of the linear antenna and the antenna terminal of the internal wireless circuit are connected via the first transmission line, the second transmission line, and the connection cable, and also connected to the second transmission line. A capacitive element is connected in parallel near the connection point with the cable, the impedance of the feeding point of the linear antenna is Za, the characteristic impedance of the first transmission line is Z1, the electrical length of the first transmission line is L1, and the second transmission line. Characteristic impedance of Z2, the electrical length of the second transmission line is L
2. Za>Z1> Z2 ≧ Zn, L1≈λ / 4, L where Zn is the impedance of the antenna terminal of the internal radio circuit and the connection cable and λ is the wavelength of the lowest operating frequency.
The feature is that 2 ≦ λ / 4 is selected.

[0007]

[Operation] In the portable radio device according to the present invention, the antenna feed point of the antenna and the antenna terminal of the internal radio circuit are impedance-matched and connected by the first transmission line and the second transmission line. Can solve the problem of very low. Therefore, the gain of the portable wireless device can be improved by greatly reducing the loss of the matching circuit.

[0008]

【Example】

Embodiment 1 FIG. 1 shows a first embodiment of the present invention. In this invention,
The internal radio circuit and the linear antenna are matched using a transmission line, and two resonances are caused. Here, 1 is a linear antenna, 2 is a housing, 3 is an internal radio circuit, 4 is a first transmission line, 5 is a second transmission line, 6 is a capacitive element, 7 is a connection cable, and 8 is a linear antenna. The feeding point 1 and 9 are the ends of the connection cable 7, and are substantially antenna terminals of the internal wireless circuit 3. 10 is a ground plane of the first and second transmission lines 4 and 5, and 1
Reference numeral 1 is a dielectric substrate that constitutes the first and second transmission lines 4 and 5, and 12 is a dielectric case that covers the wireless device. In general, the internal radio circuit 3 is a 50Ω system, and the linear antenna has a length close to ½ wavelength in order to secure the antenna gain, as shown in literature (1).

With such a structure, the first and second transmission lines 4 and 5 play the role of the conventional matching circuit 102 and resonate twice, so that a matching circuit using a lumped constant or the like is required. Therefore, the loss of the matching circuit is reduced and a high gain is obtained. The experimental results of Example 1 are shown in FIG. 2A is a return loss diagram, and FIG. 2B is a Smith chart diagram. As is clear from FIG. 2, two resonances occur and 880 MHz.
At the low resonance point of (a), VSWR <2 has a very wide band of 180 MHz and a specific bandwidth of about 20%. Here, as parameters of the antenna that was tested, the length of the linear antenna 1 was 12.5 cm, the housing was 13 × 5 × 2 cm, and the characteristic impedance Z1 of the first transmission line 4 was about 100Ω.
Length L1 is 4.5 cm, characteristic impedance Z2 of the second transmission line 5 is about 50Ω, length L2 is 4.0 cm, dielectric substrate 11
Had a thickness of about 1.5 mm, a dielectric constant of about 3.5, and a capacitor was used as the capacitive element 6, and its capacitance was about 3 pF.

The reason why two resonances and a wide band can be obtained in this structure will be described. The equivalent circuit of the antenna is shown in FIG. As shown in FIG. 3, from the linear antenna 1 to the first
5 through the transmission line 4, the second transmission line 5, the capacitive element 6
It is connected to the 0Ω internal radio circuit 3. First, FIG. 4 shows measured values of the impedance of the linear antenna 1 as viewed from the feeding point 8. As shown in this figure, the impedances of the frequencies a (880 MHz) and b (1454 MHz) to be finally resonated are Za = 203 + j149Ω and Zb = 147.
It was −j239Ω. Therefore, by rounding these impedances, the impedances a1 (Za) = 200 + j150Ω, b1 (Z) at the antenna feeding point 8 in FIG.
b) = 150−j200Ω is shown in FIG. This 2
One point should be at 50Ω (center of Smith chart).

In FIG. 5, impedances after passing through the first transmission line 4 as seen from the feeding point 8 are shown by a2 and b2. Here, considering the dielectric constant of the dielectric substrate 11, the electrical length L1 of the first transmission line 4 has a low resonance frequency of 880M.
It becomes about λ / 4 when normalized by the wavelength λL of Hz. Furthermore, since the characteristic impedance of the first transmission line 4 is 100Ω, it operates as a λL / 4 matching circuit at low frequencies. This matching principle is described in the literature (Reference (2): The Institute of Electronics and Communication Engineers: “Antenna Engineering Handbook”, Chapter 6, Feeding Circuit, 6.3.
Balanced line system, coaxial line system, strip line system lines and equipment, 6.3.2 matching circuit, [3] impedance matching circuit, p. 24 1). This matching circuit basically has a wide band characteristic. On the other hand, at a high frequency, when the wavelength is λH, the first transmission line 4 has λH
The length is close to / 2, and it rotates almost once on the Smith chart. Therefore, the impedance after passing through the first transmission line 4 (point in FIG. 3) is a2 = 32−j24Ω, b
2 = 61 + j92Ω.

For ease of explanation, the Smith chart is changed to an admittance diagram and shown in FIG. In FIG.
2, b2 are in the same positions as in FIG. Here, the admittance after passing through the second transmission line 5 is a3, b3.
Since the characteristic impedance of the second transmission line 5 is 50Ω, the second transmission line 5 only rotates on the Smith chart depending on its length, but since the frequencies are different between a and b, the rotation angle can be different. If a2 is turned 160 degrees here, b
2 rotates about 270 degrees. This is an electrical length of about 0.22λ
Equivalent to L, 0.36λH, and considering the dielectric constant of the substrate,
It corresponds to the electrical length L2 of the second transmission line 5. At this time, a
3 = 0.019-j0.015S, b3 = 0.022-j0.0
35 s, and the real part substantially matches the matching condition of Y = 0.02 + j0 (Z = 50 + j0). Therefore, at this point, the capacitive element 6 may be added in parallel to bring each imaginary part closer to zero. The capacitive element 6 has a low frequency of about 0.018S.
If it is (about 3.2 pF), it is about 0.0 at high frequency.
3S, and each admittance is a = 0.19 + j0.00
3S, b4 = 0.002-j0.005S. Converting these into impedances, a4 = 51-j8Ω, b4 = 4
3 + j10Ω and VSWR becomes 1.5 or less. As described above, with the antenna structure according to the present invention, two resonances and a wide band can be realized.

In this example, the resonance frequency, the antenna length, the impedance of the internal radio circuit 3 and the like are determined and explained by showing a concrete example, but the values are not limited to the values shown here, and the matching principle is the same. If they do, they all have the same effect. Therefore, the conditions for that are summarized as follows. Let the characteristic impedance of the first transmission line 4 be Z1,
And this electric length is L1, the characteristic impedance of the second transmission line 5 is Z2, and this electric length is L2, the impedance of the feeding point 8 of the antenna 1 is Za, the impedance of the antenna terminal 9 of the internal radio circuit 3 is Zn, and When the wavelength of the lowest operating frequency of the wireless device is λ, Za>Z1> Z2 ≧ Zn, L1≈λ / 4, L2 ≦ λ / 4.

The results of experiments conducted on the radiation characteristics of this antenna are shown in FIGS. FIG. 7 shows the case of 880 MHz and FIG. 8 shows the case of 1454 MHz. Where 0dB is 1/2
It is the maximum level of the wavelength dipole antenna. 7 and 8
In both cases, the maximum level exceeds the dipole level, and it can be seen that sufficient radiation is performed. When these efficiencies were measured, it was about -0.5 dB at 880 MHz and 1454 MHz.
Then, it is −0.7 dB, which also shows that the antenna has very little loss. However, the pattern shape has different resonance wavelengths depending on the frequency, so 880MHz and 1454
It can be seen that there is a difference in MHz. In FIG. 7, the main polarization E
The θ pattern faces the housing (−Z) direction, while 145
At 4 MHz, it faces the opposite case (+ Z).

As described above, the use of the antenna according to the present invention eliminates the need for a complicated matching circuit composed of a lumped constant between the linear antenna 1 and the antenna terminal 9 of the internal radio circuit 3. The loss can be greatly reduced. Further, since it is possible to realize two resonance and wide band characteristics, it is possible to provide a portable wireless device having a very high gain and wide band characteristics.

It should be noted that although the structure described above does not have a mechanism for accommodating the linear antenna 1 inside the housing 2, it is conceivable to provide the radio with an antenna accommodating mechanism for the sake of convenience. Even in this case, the present invention can be implemented without impairing the effects of the present invention. Second Embodiment FIG. 9 shows a second embodiment of the present invention. This embodiment is an example in which the first and second transmission lines 4 and 5 are composed of general coaxial cables. Here, reference numerals 1 to 9 are the same as those in the first embodiment, but the first and second transmission lines 4 and 5 are formed by coaxial cables.

Also in this case, each condition is exactly the same as that of the first embodiment. That is, the first transmission line (coaxial cable) 4 has a characteristic impedance of about 100Ω and an electrical length of about 0.25λ.
L, the second transmission line (coaxial cable) 5 has a characteristic impedance of about 50Ω, an electrical length of about 0.22λL, and a capacitive element 6
Has a capacitance of about 3 pF. Therefore, the effect in this case is exactly the same, and since the first and second transmission lines 4 and 5 are coaxial cables, the degree of freedom in internal wiring is higher than that in the first embodiment.

Since no matching circuit is required in this embodiment as well, the loss of the matching circuit can be reduced, the gain is high, the resonance occurs at any two points or in a wide band, and the structure of the transmission line is simple. Machine can be provided. Third Embodiment FIG. 10 shows a third embodiment of the present invention. In this embodiment, the first transmission line 4 and the second transmission line 5 are cylindrical guides formed of an insulator when the linear antenna 1 is housed in the housing 2, and in this example, a cylindrical guide 13. The case where it is formed on the peripheral surface is shown. Here, reference numerals 1 to 9 are the same as those in the first embodiment. However, in this embodiment, the feeding point 8 of the linear antenna 1 is
Is composed of a metal ring-shaped body, and supports the linear antenna 1 so that it can freely move in and out. In order to make the first and second transmission lines 4 and 5 formed in the cylindrical guide 13 easy to understand, only the portion of the cylindrical guide 13 is shown in FIG. 11. Figure 11
A is an external view of the cylindrical guide 13, and FIG. 11B is a sectional view thereof. As shown in this figure, the base plate 10 of the first and second transmission lines 4 and 5 is adhered and formed in the longitudinal direction on one side of the cylindrical guide 13, and the first and second transmission lines 4 are opposed to the base plate 10. And the metal conductors forming 5 are formed. The characteristic impedance of the first and second transmission lines 4 and 5 can be set by the width of the metal conductor. Further, the transmission line may be formed of a thin film-shaped printed circuit and wound to form a cylindrical guide. By doing so, the transmission line can be constructed relatively easily and without taking up space.
Also in this third embodiment, only the first and second transmission lines 4 and 5 are formed around the cylindrical guide 13, and other conditions are the same as in the first embodiment. By combining the third embodiment and the second embodiment, one of the first transmission line and the second transmission line is formed on the peripheral surface of the cylindrical guide 13, and the other is formed by a coaxial cable. You can also do it.

Therefore, since the matching circuit is not required even in this embodiment, the loss of the matching circuit can be reduced, the gain is high, the resonance occurs at any two points or a wide band, and the space of the transmission line portion is required. It is possible to provide a portable wireless device that does not. Fourth Embodiment FIGS. 12 and 13 show a fourth embodiment of the present invention.
In this embodiment, the linear antenna 1 is added to the configuration of the third embodiment.
The coil antenna 14 that operates during storage is connected to the tip of the. Here, FIG. 12A is a perspective view in which the inside of the housing is seen through, and FIG. 12B is a view showing only the cylindrical guide 13. Reference numerals 1 to 13 are the same as those in the third embodiment. Reference numeral 15 is a lower contact that comes into contact with the contact 1A provided at the bottom of the linear antenna 1 when the linear antenna 1 is housed. In this case, the coil antenna 14 is not connected to the linear antenna 1. Therefore, when the linear antenna 1 is pulled out, the same operation as that without the coil is performed, and the effect is the same as that of the first to third embodiments.

On the other hand, FIG. 13 shows a state in which the linear antenna 1 is housed in the cylindrical guide 13. 13A is a perspective view of the inside of the housing 2 seen through, and FIG. 13B is a view showing only the cylindrical guide 13. Linear antenna 1 when the antenna is stored
The lower contact 1A is connected to the plus of the connection cable 7 at the lower contact 15 of the cylindrical guide 13. For this reason, the stored linear antenna 1 and the base metal 10 of the cylindrical guide 13 are housed.
Constitutes a transmission line, and transmits high-frequency power to the tip of the housed linear antenna 1, that is, a portion slightly protruding from the housing, and feeds it to the non-contact coil antenna 14.
In this case, since the impedance at the antenna feeding point 8 is different when the linear antenna 1 is pulled out and when it is stored, the antenna design as shown in the first embodiment is performed when the antenna is pulled out, and the number of turns of the coil antenna 14 is stored when the antenna is stored. It is necessary to adjust the impedance to match the impedance.

Therefore, since the matching circuit is not required even in this embodiment, the loss of the matching circuit can be reduced, the gain is high, the resonance occurs at any two points or a wide band, and the space for the transmission line portion is required. In addition, it is possible to provide a portable wireless device that can secure a sufficient antenna gain even when the linear antenna is housed.

[0022]

As described above, according to the portable radio device of the present invention, a complicated matching circuit constituted by a lumped constant is not required between the linear antenna 1 and the antenna terminal 9 of the internal radio circuit 3. Therefore, this loss can be significantly reduced, and further, two resonance and wide band characteristics can be realized, so that it is possible to provide a portable wireless device having extremely high gain and wide band characteristics. it can.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a portable wireless device proposed in claim 1 of the present invention.

2 is a characteristic curve diagram for explaining the operation of the embodiment shown in FIG.

FIG. 3 is an equivalent circuit diagram for explaining the operation of the embodiment shown in FIG.

FIG. 4 is a characteristic curve diagram for explaining the operation of FIG.

5 is a characteristic curve diagram for explaining the operation of FIG.

FIG. 6 is a characteristic curve diagram similar to FIG.

FIG. 7 is a characteristic curve diagram showing the antenna radiation characteristic of the embodiment shown in FIG.

FIG. 8 is a characteristic curve diagram similar to FIG.

FIG. 9 is a perspective view showing a second embodiment of the present invention.

FIG. 10 is a perspective view showing a third embodiment of the present invention.

11 is an enlarged perspective view showing a main part of the embodiment shown in FIG. 10 in an enlarged manner, and B is a sectional view.

FIG. 12 is a perspective view and B is a sectional view showing an embodiment of the present invention.

13 is a perspective view for explaining the operation of FIG. 12,
B is a sectional view.

FIG. 14 is a perspective view for explaining a conventional technique.

[Explanation of symbols]

1 linear antenna 2 housing 3 Internal radio circuit 4 First transmission line 5 Second transmission line 6 Capacitive element 7 connection cable 8 Antenna feed point 9 Antenna terminal 10 Ground plate constituting the first and second transmission lines

Continuation of the front page (56) Reference JP 62-213303 (JP, A) JP 5-243829 (JP, A) JP 6-314918 (JP, A) JP 60-55703 (JP , A) JP 6-260828 (JP, A) JP 59-30306 (JP, A) JP 5-343911 (JP, A) JP 7-176936 (JP, A) JP 8-288723 (JP, A) JP-A-6-152221 (JP, A) JP-A-7-111415 (JP, A) JP-A-54-51447 (JP, A) JP-A-7-193421 (JP, A) JP 53-82246 (JP, A) JP 5-206888 (JP, A) JP 5-37226 (JP, A) JP 7-263930 (JP, A) JP 7 -106999 (JP, A) JP 61-25301 (JP, A) JP 7-221531 (JP, A) JP 62-51802 (JP, A) JP 8-186420 (JP, A) ) JP-A-6-260827 (JP, A) Actually open 63-99406 (JP, U) Actually open 1-171102 (JP U) (58) investigated the field (Int.Cl. ^7, DB name) H01Q 1/24 H01Q 9/30 H04B 1/18 - 1/40

Claims (5)

(57) [Claims] 1. A portable wireless device constituted by housing an internal wireless circuit in a housing, arranging a linear antenna outside the housing, and electrically connecting the linear antenna and the internal wireless circuit, The feeding point of the linear antenna and the antenna terminal of the internal radio circuit are connected via a first transmission line, a second transmission line and a connection cable, and a connection point between the second transmission line and the connection cable. Connect a capacitive element in parallel in the vicinity,
The impedance of the feeding point of the linear antenna is Za, the characteristic impedance of the first transmission line is Z1, the electrical length of the first transmission line is L1, the characteristic impedance of the second transmission line is Z2, and the electrical length of the second transmission line is L2, the impedance of the antenna terminal of the internal wireless circuit and the connection cable is Z
If n and the wavelength of the lowest operating frequency are λ, then Za> Z1
> Z2 ≧ Zn, L1≈λ / 4, L2 ≦ λ / 4. 2. The mobile wireless device according to claim 1, wherein the linear antenna is mounted in a housing so as to be stored therein. 3. The portable wireless device according to claim 2, wherein either or both of the first transmission line and the second transmission line are provided on a peripheral surface of a cylindrical guide for accommodating the linear antenna in a housing. A portable wireless device characterized by being formed. 4. The portable wireless device according to claim 2, wherein a coil-shaped antenna is installed at the tip of the linear antenna. 5. The portable wireless device according to claim 4, wherein the lower portion of the linear antenna is connected to the positive terminal of the connection cable when the linear antenna is stored.