JP7138556B2 - wireless communication device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a wireless communication device provided with an I/F cable having an antenna function.

An antenna is required for a wireless communication device to transmit and receive radio waves. The performance of an antenna is determined by its electrical size, which is standardized by the wavelength of radio waves to be transmitted and received. In general, the larger the antenna, the better the performance. On the other hand, there is also a demand for miniaturization of the device, so the antenna performance and the size of the wireless communication device are in a trade-off relationship, and the antenna is designed to obtain high antenna performance with a small antenna size.

If a high-frequency signal is passed through a metal structure, radio waves will be radiated. Therefore, instead of providing a structure dedicated to antennas, a general-purpose I/F cable for connecting to structures for other purposes, such as other devices, should be used. There is a cable antenna technology in which a high-frequency signal is passed through a cable (hereinafter simply referred to as an "I/F cable") to be used as an antenna.

Techniques related to cable antennas that use an I/F cable as part of the antenna are disclosed in Patent Documents 1 and 2, for example. In Patent Document 1, a signal line of a separately provided antenna is connected to a general-purpose interface terminal, and a high-frequency signal received by the antenna is superimposed on a low-speed signal originally flowing through an I/F cable and transmitted to an information communication terminal. , discloses a method for reducing the size of an information communication terminal by eliminating an antenna connector from the information communication terminal.

Further, in Patent Document 2, a monopole antenna is configured by connecting a coaxial cable to an I/F connector such as a USB, using the outer conductor of the coaxial cable as an antenna element, and using the GND of an information communication terminal as an antenna GND. A technique has been disclosed that enables radio waves to be received without providing a separate antenna.

Japanese Patent No. 5803896 Japanese Patent No. 5834487

Patent Document 2 discloses an example in which a cable connecting an earphone and an information communication terminal is used as an antenna element. In this case, there is no need to provide a dedicated structure as an antenna element, but neither disclosure nor suggestion is made as to how to improve performance as an antenna such as antenna gain and radiation efficiency. For example, if the length of the cable connected to the I/F connector is too long or too short compared to the ideal length for an antenna, the performance as an antenna will be degraded. There was a problem.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a radio communication apparatus capable of improving performance as an antenna by providing a cable with an antenna function.

A radio communication device according to the present invention includes a first transmission/reception circuit for transmitting/receiving a signal for radio communication with another radio communication device, and a second transmission/reception circuit for transmitting/receiving a signal having a frequency lower than that of the signal. a cable comprising a plurality of signal lines; and an external device including a third transmission/reception circuit for transmitting/receiving signals to/from the second transmission/reception circuit via the cable, wherein the cable comprises: Functioning as a monopole antenna , connected to the wireless communication terminal and the external device in a state of forming one or more loops, the first transmitting/receiving circuit communicates with the other wireless communication device via the cable. wireless communication between

According to the present invention, the cable is connected to the wireless communication terminal and the external device while forming one or more loops, and the first transmission/reception circuit communicates with another wireless communication device via the cable. Since wireless communication is performed, the high-frequency impedance viewed from the GND side of the cable can be changed by the number of loops, the position of the loop, and the size of the loop. As a result, the performance of the cable as an antenna can be improved.

1 is a configuration diagram of a wireless communication device according to Embodiment 1; FIG. 2 is a configuration diagram of a wireless communication device according to Embodiment 2; FIG. FIG. 10 is an explanatory diagram showing high-frequency currents of the wireless communication device according to the second embodiment; FIG. 10 is an explanatory diagram showing high-frequency currents of the wireless communication device according to the second embodiment; FIG. 10 is a configuration diagram showing a connection state between a wireless communication terminal provided in a wireless communication device according to Embodiment 3 and an external device; FIG. 10 is an explanatory diagram showing a high-frequency current of a wireless communication device according to related technology;

<Embodiment 1>
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a wireless communication device 1 according to Embodiment 1. As shown in FIG.

As shown in FIG. 1, the wireless communication device 1 includes a wireless communication terminal 11, an external device 12, and an I/F cable 13.

The wireless communication terminal 11 includes a first transmission/reception circuit 111 , a second transmission/reception circuit 112 , and a dividing/combining section 113 . The first transmission/reception circuit 111 transmits or receives a high frequency signal for wireless communication with another wireless communication device. The second transmission/reception circuit 112 transmits or receives control signals to/from the external device 12 . Here, the control signal is a low frequency signal whose frequency is lower than that of the high frequency signal. The distributing/combining unit 113 distributes or synthesizes the signals by utilizing the fact that the frequencies of the signals transmitted or received by the first transmitting/receiving circuit 111 and the second transmitting/receiving circuit 112 are different.

The external device 12 has a high frequency filter section 121 and a third transmission/reception circuit 122 . The high-frequency filter unit 121 removes the frequency signal transmitted by the first transmission/reception circuit 111 . The third transmission/reception circuit 122 transmits or receives control signals to/from the second transmission/reception circuit 112 via the I/F cable 13 . Here, the frequency signals transmitted by the second transmission/reception circuit 112 and the third transmission/reception circuit 122 are not removed by the high-frequency filter section 121 .

Next, the operation of the wireless communication device 1 will be described. To simplify the explanation, the case where the first transmission/reception circuit 111 transmits a high-frequency signal will be described as an example.

A wireless communication terminal 11 is connected to an external device 12 via an I/F cable 13 . The I/F cable 13 is a cable in which a plurality of metal signal lines are bundled, and is connected to the wireless communication terminal 11 and the external device 12 using a general-purpose connector such as RJ11.

A low-frequency signal transmitted from the second transmission/reception circuit 112 and exchanged between the wireless communication terminal 11 and the external device 12 flows through the I/F cable 13 . At the same time, the high-frequency signal transmitted by the first transmission/reception circuit 111 is combined with the low-frequency signal by the distributing/combining section 113 and transmitted to the I/F cable 13 . Here, the low-frequency signal is, for example, a signal of several kHz or more and several MHz or less. A high-frequency signal is, for example, a signal of several hundred MHz or more and several GHz or less.

The dividing/synthesizing unit 113 is an electric circuit including a filter such as a low-pass filter or a high-pass filter. Since the I/F cable 13 is not a cable for transmitting high frequency signals such as a coaxial cable, it has the characteristic of radiating radio waves into space during transmission when trying to transmit a high frequency signal. Therefore, the high-frequency signal is radiated from the I/F cable 13 to the surrounding space as radio waves, and the I/F cable 13 behaves as a cable antenna.

On the other hand, since the signal transmitted by the second transmission/reception circuit 112 has a low frequency, it is not radiated from the I/F cable 13 and reaches the third transmission/reception circuit 122 through the high frequency filter section 121 . The high-frequency filter unit 121 is, for example, a low-pass filter circuit, and removes the signal that has not been attenuated by the radiation from the I/F cable 13 from among the high-frequency signals transmitted by the first transmission/reception circuit 111, It prevents high-frequency signals from being input to the transmission/reception circuit 122 .

However, the strength of the high frequency signal input to the third transmission/reception circuit 122 changes according to the length of the I/F cable 13 and the strength of the high frequency signal transmitted from the first transmission/reception circuit 111 . Therefore, if the strength of the high-frequency signal input to the third transmission/reception circuit 122 is weak enough not to affect the communication between the wireless communication terminal 11 and the external device 12, the high-frequency filter section 121 cannot be provided. Not required.

In general wireless communication equipment, it is common to match the impedance between the transmission source circuit and the antenna in order to avoid reflection loss, which is loss caused by reflection of high frequency signals at the boundary between the antenna and the transmission source circuit. is performed on Also, the antenna and the transmission source circuit are generally designed to have an impedance of 50Ω. The impedance of an antenna is a value determined by the frequency of a signal, the size of the antenna, the shape of the antenna, and the like.

Here, since the positional relationship between the wireless communication terminal 11 and the external device 12 is usually determined from the structural requirements of the wireless communication device 1, the length and layout of the I/F cable 13 connecting them are also determined by the wireless communication. It is dependently determined from the structural requirements of the device 1 . Therefore, the impedance of the I/F cable 13 as a cable antenna is also determined subordinately, and impedance matching is performed between the I/F cable 13 and the transmission source circuit (dividing/combining unit 113 in the case of the first embodiment). cannot be realized, and the reflection loss increases. Since the power resulting from the reflection loss is not radiated into space, the radiated radio wave intensity is lower than when appropriate impedance matching is performed, which adversely affects communication quality, such as shortening the communication range.

In order to solve such a problem, in Embodiment 1, the I/F cable 13 is connected to the wireless communication terminal 11 and the external device 12 while forming one or more loops. If the I/F cable 13 that functions as an antenna is looped, the path through which the high-frequency signal flows becomes looped, thus generating stray inductance.

In addition, stray capacitance is generated when the metal signal lines forming the I/F cable 13 come close to each other. Also, the value of the stray reactance changes depending on the size and number of turns of the loop. The stray reactance changes the impedance of the I/F cable 13 as seen from the divider/combiner 113 . In addition, since the phase of the stray reactance seen from divider/combiner 113 is rotated depending on the distance from divider/combiner 113, which is the transmission source, to the loop, impedance matching can also be adjusted by the distance from divider/combiner 113 to the loop.

As described above, by adjusting the size of the loop of the I/F cable 13, the number of turns of the loop, and the distance from the divider/synthesizer 113 to the loop, impedance matching when the I/F cable 13 is used as a cable antenna can be achieved. can be adjusted to increase the intensity of radio waves emitted by the I/F cable 13 .

Further, since the I/F cable 13 is a cable that connects the wireless communication terminal 11 and the external device 12, if the positional relationship between the wireless communication terminal 11 and the external device 12 does not change, the wireless communication device 1 is fixed to a case or the like. It is also possible to In that case, the shape including the loop portion of the I/F cable 13 does not change, and the antenna performance of the I/F cable 13 as a cable antenna also does not change. As a result, even when the antenna characteristics of the I/F cable 13 are adjusted by the loop, the I/F cable 13 is not displaced and the shape of the loop is not destroyed, so that the antenna performance is less likely to change.

Next, effectiveness of the first embodiment will be described. The inventors of the present application set the length of the I/F cable 13 to 1/2 of the wavelength of the signal transmitted and received by the first transmission/reception circuit 111, and opened the I/F cable 13 at the tip for high frequencies. I did an experiment.

If the I/F cable 13 is viewed as an antenna, it can be regarded as a 1/2 wavelength monopole antenna. The high frequency current becomes smaller. Therefore, radiation from the I/F cable 13 is reduced. However, if the loop is a single circular loop having a diameter of 1/10 of the wavelength of the signal transmitted by the first transmitting/receiving circuit 111 and the position of the loop is the central portion of the I/F cable 13, then the I/F It was confirmed that radiation from the F cable 13 increased.

In the above description, the transmission antenna was used as an example for the sake of simplicity, but it is well known that the same effect can be obtained with both the transmission antenna and the reception antenna due to the reciprocity of the antenna. . This also applies to subsequent embodiments.

As described above, in the wireless communication device 1 according to the first embodiment, the I/F cable 13 is connected to the wireless communication terminal 11 and the external device 12 while forming one or more loops. Since the transmitting/receiving circuit 111 performs wireless communication with another wireless communication device via the I/F cable 13, the high-frequency impedance of the I/F cable 13 side viewed from GND is measured by the number of loops, the position of the loop, and the position of the loop. and can vary with the size of the loop. Thereby, the performance of the I/F cable 13 as an antenna can be improved. Therefore, the effect that the communication quality of the wireless communication device 1 is improved can be obtained.

In addition, since the electrical size of the antenna is determined by the I/F cable 13, the antenna performance can be improved by increasing the electrical size of the antenna, the wireless communication terminal 11 can be made smaller, and the wireless communication device 1 can be made smaller. The effect of being compatible can also be obtained. Further, by operating the I/F cable 13 as a cable antenna, radio waves can be radiated from an electrically large antenna, that is, an antenna with small loss and good performance, so that an increase in the energy consumption of the wireless communication device 1 can be suppressed. .

The wireless communication terminal 11 further includes a divider/combiner 113 that divides or combines the signals transmitted/received to/from the first transmission/reception circuit 111 and the second transmission/reception circuit 112 . At least one signal line among the lines is connected to the first transmission/reception circuit 111 via the divider/combiner 113 .

Therefore, the high-frequency signal transmitted from the first transmission/reception circuit 111 can be combined with the electrical signal by the divider/combiner 113 and transmitted to the I/F cable 13 .

The connection between the wireless communication terminal 11 and the external device 12 via the I/F cable 13 is performed in a state where one circular loop is formed at the central portion of the I/F cable 13 in the longitudinal direction. The height is 1/2 of the wavelength of the signal transmitted/received by the first transmission/reception circuit 111, and the diameter of the circular loop is 1/10 of the wavelength of the signal transmitted/received by the first transmission/reception circuit 111. FIG.

Therefore, radiation from the I/F cable 13 is increased, and extremely high antenna performance with respect to the I/F cable 13 is obtained.

<Embodiment 2>
Next, the wireless communication device 2 according to Embodiment 2 will be described. FIG. 2 is a configuration diagram of the wireless communication device 2 according to the second embodiment. 3 and 4 are explanatory diagrams showing the high-frequency current of the wireless communication device 2 according to the second embodiment. In the second embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 2, in the second embodiment, the configuration of the radio communication terminal is different from that in the first embodiment. The wireless communication device 2 includes a wireless communication terminal 21 , an external device 12 and an I/F cable 13 .

The wireless communication terminal 21 includes a first transmission/reception circuit 111 , a second transmission/reception circuit 112 , an antenna 211 , and a GND ground plane (hereinafter simply referred to as “ground plane”) 212 .

The first transmission/reception circuit 111 is connected to the antenna 211 and transmits high frequency signals to the antenna 211 . The high-frequency signal transmitted to the antenna 211 is radiated from the antenna 211 toward space.

Antenna 211 is an unbalanced antenna such as a monopole antenna. The second transmission/reception circuit 112 is connected to at least one signal line among the plurality of signal lines forming the I/F cable 13 and communicates with the external device 12 . At least one of the signal lines constituting the I/F cable 13, which is different from the signal line connected to the second transmission/reception circuit 112, is connected directly to the ground plane 212 or through a high frequency such as a capacitor. connected through means.

Next, operation of the antenna 211 will be described with reference to FIG. As described above, since the antenna 211 is an unbalanced antenna, an unbalanced current flows through the ground plane 212 when a feed current is supplied to the antenna 211 . It is generally known that high-frequency currents flow along the edges of conductors, and unbalanced currents flow along the edges of ground plane 212, as indicated by the arrows in FIG. At least one signal line among the plurality of signal lines forming the I/F cable 13 is connected to the ground plane 212 , so the unbalanced current flows into the I/F cable 13 via the ground plane 212 . As described in the first embodiment, radio waves are radiated when a high-frequency current flows through the I/F cable 13. Therefore, the I/F cable 13 also operates as a cable antenna in the second embodiment.

When the I/F cable 13 operates as a cable antenna, radio wave radiation from the entire wireless communication device 2 is a combination of radiation from the antenna 211 and radiation from the I/F cable 13 .

Here, when the coordinate axes are set so that the ground plane 212 is on the XY plane, and the antenna 211 is a monopole antenna extending from the ground plane 212 in a direction parallel to the X axis as shown in FIG. Radio waves have directivity on the YZ plane, and are null in the X-axis direction.

On the other hand, as shown in FIG. 4, when the I/F cable 13 is extended in the Y direction, the unbalanced current also flows in the Y axis direction. The directivity is directed upward, and the Y-axis direction is null. When viewed from the radio communication device 2 as a whole, radio waves can be radiated in all directions, so communication with other radio communication devices existing in unspecified directions is possible.

Of course, the direction of high-frequency current flowing through antenna 211 and I/F cable 13 is not limited to the above. If the high-frequency current flowing in the antenna 211 and the high-frequency current flowing in the I/F cable 13 are not parallel, the null direction of radiation from each high-frequency current will not match. It can emit radio waves.

Considering communication with another wireless communication device, it is conceivable that the receiving wireless communication device exists in the horizontal plane direction (ZX plane direction) seen from the transmitting source wireless communication device. However, due to the characteristics of the antenna 211, even if the radio waves radiated from the antenna 211 have directivity on the YZ plane and the X-axis direction is null, the I/F cable 13 is made to run in the vertical direction (Y direction). As a result, radio waves can be strongly radiated from the I/F cable 13 in the horizontal plane.

At this time, since the I/F cable 13 is connected in a state of being looped one or more times, as described in the first embodiment, the I/F cable 13 may The impedance can be adjusted when the cable 13 is used as a cable antenna, and the effect of improving the quality of wireless communication can be obtained.

Next, a related technique will be described with reference to FIG. FIG. 6 is an explanatory diagram showing a high-frequency current of a wireless communication device according to related technology.

As shown in FIG. 6, there is a method of providing a parasitic antenna 213 that radiates radio waves from an unbalanced current in addition to the antenna 211 that feeds. However, in this method, it is necessary to provide a new parasitic antenna 213 in the wireless communication terminal, and in order to give the parasitic antenna 213 high performance, the parasitic antenna 213 is electrically large (typically 1 /4 to 1/2 wavelength). Therefore, there is a problem that the wireless communication terminal becomes large.

On the other hand, in the wireless communication device 2 according to the second embodiment, the wireless communication terminal 21 includes an antenna 211 to which the first transmission/reception circuit 111 is connected and a plurality of signal lines forming the I/F cable 13. and a ground plane 212 to which at least one of the signal lines is connected. connected to at least one signal line different from the line.

Therefore, unless the high-frequency current flowing in the antenna 211 and the high-frequency current flowing in the I/F cable 13 are parallel, the null direction of radiation from each high-frequency current does not match. Can emit radio waves. Since the performance of the I/F cable 13 as an antenna can be improved, the effect of improving the communication quality of the wireless communication device 2 can be obtained.

Moreover, since the wireless communication device 2 does not need to be provided with the parasitic antenna 213 as in the related technology, it is possible to suppress the wireless communication terminal 21 from increasing in size.

<Embodiment 3>
Next, a wireless communication device according to Embodiment 3 will be described. FIG. 5 is a configuration diagram showing a connection state between the wireless communication terminal 11 and the external device 12 provided in the wireless communication apparatus according to the third embodiment. In addition, in Embodiment 3, the same components as those described in Embodiments 1 and 2 are denoted by the same reference numerals, and descriptions thereof are omitted.

As shown in FIG. 5, in the third embodiment, the configuration of the wireless communication terminal is different from that in the first embodiment, and the connection between the dividing/synthesizing unit 113 and the high-frequency filter unit 121 by the I/F cable 13 is different. ing. A wireless communication device according to Embodiment 3 includes a wireless communication terminal 31 , an external device 12 and an I/F cable 13 . A base plate 212 is further provided for the wireless communication terminal 31 and the wireless communication terminal 11 .

The I/F cable 13 is a cable composed of a plurality of signal lines (two lines are shown as an example), and is a cable composed of a first signal line 131 and a second signal line 132 here. In addition, although the I/F cable 13 is illustrated in a straight line in FIG. there is

Next, the operation of the wireless communication device according to Embodiment 3 will be described. As shown in FIG. 5, when viewed from the high frequency signal, one end of the first signal line 131 and one end of the second signal line 132 are short-circuited inside the high frequency filter section 121 in terms of high frequency. The other end of the first signal line 131 is connected to the ground plane 212 inside the divider/synthesis unit 113 in terms of high frequency, either directly or through a means for connecting high frequencies such as a capacitor. The other end of the second signal line 132 is connected to the first transmission/reception circuit 111 . Although not shown, the first signal line 131 and the second signal line 132 are connected to the second transmitting/receiving circuit 112 or the third transmitting/receiving circuit 122 in a low-frequency manner as required, and communicate with the wireless communication terminal 11. It is used for exchanging signals with the external device 12 .

For example, when feeding power directly to the I/F cable 13, the signal line to be fed (the second signal line 132 in the third embodiment) and other signal lines (the first signal line 131 in the third embodiment) ) are close to each other, the impedance at high frequencies of the signal line to be fed is extremely lowered. Therefore, there is a problem that it is difficult to achieve impedance matching with the feeding circuit (the first transmitting/receiving circuit 111 in the third embodiment).

In contrast, in Embodiment 3, wireless communication terminal 31 further includes base plate 212 to which at least one of signal lines 131 and 132 constituting I/F cable 13 is connected, The first transmission/reception circuit 111 is connected to at least one signal line 132 different from the at least one signal line 131 connected to the ground plane 212 among the plurality of signal lines 131 and 132 forming the I/F cable 13 . and the end of at least one signal line 132 connected to the first transmission/reception circuit 111 on the external device 12 side and the end of the at least one signal line 131 connected to the ground plane 212 on the external device 12 side shorted.

Therefore, when the I/F cable 13 side is viewed from the first transmission/reception circuit 111, it can be regarded as a folded monopole antenna. It is known that the folded monopole antenna can increase the impedance compared to the monopole antenna. becomes easier. As a result, the intensity of radio waves radiated into space can be further increased.

<Other Modifications>
In Embodiments 1 to 3, it is also possible to change the arrangement and shape of the constituent elements. For example, loading an antenna with an inductor or a capacitor to improve impedance matching is a common antenna technology, and can be easily assumed to be applied to antennas including the cable antennas described herein. It is a change that In addition, by branching the antenna and combining parasitic elements with different lengths, the antenna can support multiple frequencies, and by fabricating the antenna with a copper foil pattern on the substrate, miniaturization and cost reduction are realized. It is also a common technique in the relevant field, and its application is assumed.

In the above explanation, the wireless communication terminal and the external device exchange signals via an I/F cable. It is clear that the cable antenna is also effective.

In addition, within the scope of the invention, each embodiment can be freely combined, and each embodiment can be appropriately modified or omitted.

Reference Signs List 1, 2 wireless communication device 11 wireless communication terminal 12 external device 13 I/F cable 21, 31 wireless communication terminal 111 first transmission/reception circuit 112 second transmission/reception circuit 113 dividing/synthesizing unit 122 second 3 transmitting/receiving circuits, 131, 132 signal lines, 211 antenna, 212 ground plane.

Claims (5)

A wireless communication terminal including a first transmission/reception circuit for transmitting/receiving a signal for wireless communication with another wireless communication device, and a second transmission/reception circuit for transmitting/receiving a signal having a frequency lower than that of the signal;
a cable consisting of a plurality of signal lines;
an external device including a third transmission/reception circuit that transmits/receives a signal to/from the second transmission/reception circuit via the cable;
with
the cable functions as a monopole antenna and is connected to the wireless communication terminal and the external device while forming one or more loops;
The wireless communication device, wherein the first transmission/reception circuit performs wireless communication with the other wireless communication device via the cable. The wireless communication terminal further includes a divider/combiner that divides or combines the signals transmitted/received to/from the first transmission/reception circuit and the second transmission/reception circuit,
2. The wireless communication device according to claim 1, wherein at least one signal line among the plurality of signal lines forming the cable is connected to the first transmission/reception circuit via the divider/combiner. The wireless communication terminal further includes an unbalanced antenna to which the first transmission/reception circuit is connected, and a ground plane to which at least one of the plurality of signal lines forming the cable is connected,
The second transmitting/receiving circuit is connected to at least one of the plurality of signal lines forming the cable, which is different from at least one of the signal lines connected to the ground plane. 1. The wireless communication device according to 1. The wireless communication terminal further includes a ground plane to which at least one of the plurality of signal lines forming the cable is connected,
the first transmission/reception circuit is connected to at least one signal line different from at least one signal line connected to the ground plane among the plurality of signal lines forming the cable;
An end portion of the at least one signal line connected to the first transmission/reception circuit on the side of the external device and an end portion of the at least one signal line connected to the ground plane on the side of the external device are short-circuited. The wireless communication device of claim 1, wherein The connection between the wireless communication terminal and the external device in the cable is performed in a state in which one circular loop is formed at the central portion in the longitudinal direction of the cable,
the length of the cable is half the wavelength of the signal transmitted and received by the first transmission/reception circuit;
2. The wireless communication device according to claim 1, wherein the diameter of said circular loop is 1/10 of the wavelength of said signal transmitted and received by said first transmission/reception circuit.

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