JP4844162B2 - ANTENNA DEVICE AND RADIO RECEPTION DEVICE USING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the characteristic of an antenna device having a structure in which a plurality of coils are wound around one and the same core. <P>SOLUTION: The antenna device is provided with a first coil L1 and a second coil L2 wound around the same core, a pair of terminals 113a and 113b, and a switching circuit 112 for connecting the first and second coils L1 and L2 to the pair of terminals 113a and 113b in series when control signals P1 and P2 represent a first state and connecting the first and second coils L1 and L2 to the pair of terminals 113a and 113b in parallel when the control signals P1 and P2 represent a second state. Since this prevents the first and second coils L1 and L2 from being opened, it is possible to prevent the coils from being subjected to characteristic deterioration based on self-resonance. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to an antenna device and a wireless reception device using the antenna device, and more particularly to an antenna device having a structure in which a plurality of coils are wound around the same core and a wireless reception device using the antenna device.

  Conventionally, an antenna coil having a structure in which a coil is wound around a core made of a magnetic material such as ferrite is known. A wireless receiver using such an antenna coil can usually receive only radio waves in a single frequency band. However, as described in Patent Document 1, a plurality of coils are wound around the same core. If the connection relation between these coils and the receiving circuit (detection IC) is switched and used, it is possible to receive radio waves in a plurality of bands.

The wireless receiver described in Patent Document 1 has two coils wound around the same core, and either one of them is connected to the receiving circuit, or these two coils are connected to the receiving circuit. The switching circuit can select whether to connect in series. Thereby, when only one coil is selected, the obtained inductance value becomes small, so that it is possible to receive radio waves in a relatively high frequency band. On the other hand, when both coils are selected, the obtained inductance value becomes large, so that it is possible to receive radio waves in a relatively low frequency band. Thereby, it is possible to receive radio waves in a plurality of bands without using a plurality of cores.
JP 2003-60520 A

  However, in the wireless reception device described in Patent Document 1, there are cases where desired characteristics cannot be obtained when only one coil is selected.

  Therefore, an object of the present invention is to improve the characteristics of an antenna device having a structure in which a plurality of coils are wound around the same core and a radio receiving device using the antenna device.

  As a result of intensive research on the cause of the above-described problem, the present inventor, when only one coil is selected, the other coil that is not selected causes self-resonance. I found out that it was deteriorating.

  The present invention has been made on the basis of the technical knowledge described above. An antenna device according to one aspect of the present invention includes a core, and the first coil and the first coil, both wound around the core. A plurality of coils including at least a second coil having a lower self-resonance point, a pair of terminals, and a switching circuit that switches a connection relationship between the pair of terminals and the plurality of coils, When both ends of the first coil are connected to the pair of terminals, respectively, the second coil is connected in parallel to the first coil.

  According to the present invention, since the first coil and the second coil are connected in parallel by the switching circuit, the combined self-resonance point of the coil is sufficiently more than the self-resonance point of the second coil. Move to higher bandwidth. For this reason, even when the self-resonance point of the second coil is included in the operating frequency band of the first coil, this does not affect the operating frequency band of the first coil. It becomes possible to obtain characteristics.

  When selecting the operating frequency band of the second coil, the first and second coils may be connected in series to the pair of terminals using the switching circuit, and both ends of the second coil may be connected to each other. You may connect to a pair of terminals, respectively. According to the former, it is possible to obtain a larger inductance value and Q value, and according to the latter, it is possible to simplify the configuration of the switching circuit.

  An antenna device according to another aspect of the present invention includes a core, a plurality of coils wound around the core, a pair of terminals, and the pair of terminals when the control signal represents a first state. A switching circuit for connecting the plurality of coils in parallel to the pair of terminals when the plurality of coils are connected in series to the terminal and the control signal represents the second state. It is characterized by that.

  According to the present invention, since the plurality of coils are not in an open state, for example, even when the self-resonance points of the plurality of coils are different from each other, the characteristics based on the self-resonance of the coils It becomes possible to prevent deterioration.

  According to another aspect of the present invention, there is provided a radio receiving apparatus including the antenna apparatus described above and a receiving circuit connected to the pair of terminals. According to this, it is possible to provide a wireless reception device with excellent reception sensitivity.

  As described above, according to the present invention, an unselected coil does not affect the characteristics of the selected coil, so that an antenna device having desired characteristics can be provided. Further, if the antenna device according to the present invention is used for a radio reception device, a small and high-performance radio reception device can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a circuit diagram showing a configuration of a radio receiving apparatus according to a preferred first embodiment of the present invention.

  As shown in FIG. 1, the wireless reception device 100 according to the present embodiment includes an antenna device 110, a reception circuit 120, and a control circuit 130.

  The antenna device 110 includes a bar antenna unit 111 having a first coil L1 and a second coil L2, a switching circuit 112, and a pair of terminals 113a and 113b. The first coil L1 and the second coil L2 included in the bar antenna unit 111 are wound around the same core, and therefore both are magnetically coupled to each other. As the core, a Ni—Zn ferrite core, a Mn—Zn ferrite core, a metal core such as a silicon steel plate, an amorphous metal core, a laminated metal core, a metal dust core, or the like can be preferably used.

  Further, as shown in FIG. 1, the number of turns of the second coil L2 is set to be larger than that of the first coil L1, and therefore, the self-resonance point is the second coil than the first coil L1. The coil L2 is lower. The self-resonance point is the frequency at which the coil characteristics change from inductive to capacitive. Of course, when used as an inductance element, the frequency band lower than the self-resonance point must be set as the operating frequency. There is. The “operating frequency” means a frequency band that should be received by the receiving circuit 120.

  The switching circuit 112 is a circuit for switching the connection relationship between the pair of terminals 113a and 113b and the first and second coils L1 and L2, and as shown in FIG. 1, the first switch SW1 and the second switch A switch SW2 is provided. The first switch SW1 has three nodes A, B, and C, and is a switch that connects one of the node A and the node B to the node C. Here, the node A is a node connected to one end L1a of the first coil L1, and the node B is a node connected to the other end L1b of the first coil L1. The node C is a node connected to one end L2a of the second coil L2. The first switch SW1 having such a configuration is switched by a control signal P1 supplied from the control circuit 130.

  On the other hand, the second switch SW2 has two nodes D and E, and is a switch for selecting whether or not to connect the node D and the node E. Here, the node D is a node connected to one end L1a of the first coil L1, and the node E is a node connected to the other end L2b of the second coil L2. The second switch SW2 having such a configuration is switched by a control signal P2 supplied from the control circuit 130.

  The first and second switches SW1 and SW2 are composed of mechanical relay switches, bipolar transistors, junction field effect transistors, metal oxide film type field effect transistors, PIN diodes, compound semiconductor elements represented by GaAs, and the like. Can do.

  As shown in FIG. 1, the other end L1b of the first coil L1 is connected to a terminal 113a, and is connected to the receiving circuit 120 through the terminal 113a. Similarly, the other end L2b of the second coil L2 is connected to the terminal 113b, and is connected to the receiving circuit 120 via this terminal 113b. The receiving circuit 120 is a circuit that detects and amplifies signals supplied from the pair of terminals 113a and 113b.

  Next, the operation of the wireless reception device 100 according to the present embodiment will be described focusing on the operation of the switching circuit 112.

  FIGS. 2A and 2B are tables for explaining the connection state of the coils by switching of the switches. FIG. 2A shows the first switching method, and FIG. 2B shows the second switching method.

  First, the first switching method shown in FIG.

  In the first switching method, when the operating frequency is set to “low range”, the first switch SW1 is switched to the node A side and the second switch SW2 is turned off (the state shown in FIG. 1 corresponds to this). ). As a result, the first and second coils L1, L2 are connected in series to the pair of terminals 113a, 113b. For this reason, the inductance connected between the pair of terminals 113a and 113b is substantially the sum of the inductance of the first coil L1 and the inductance of the second coil L2, and operates in a relatively low frequency band. The frequency can be set.

  Here, since the number of turns of the second coil L2 is sufficiently larger than that of the first coil L1, the second coil L2 is dominant as an obtained inductance value. Therefore, as the operating frequency, it is possible to use substantially the same frequency band as when the second coil L2 is used alone.

  On the other hand, when the operating frequency is set to “high range”, the first switch SW1 is switched to the node B side and the second switch SW2 is turned on. As a result, the first and second coils L1, L2 are connected in parallel to the pair of terminals 113a, 113b. For this reason, the inductance connected between the pair of terminals 113a and 113b is substantially the reciprocal of the sum of the reciprocal of the inductance of the first coil L1 and the reciprocal of the inductance of the second coil L2. In addition, the high frequency side can be set as the operating frequency.

  In this case, as the obtained inductance value, the first coil L1 having a small number of turns is dominant, and therefore, the operating frequency may be approximately the same frequency band as that when the first coil L1 is used alone. Is possible. That is, the contribution of the second coil L2 is slight, and from this point of view, it seems that there is no problem even if the second coil L2 is in an open state. However, if the second coil L2 is opened while the first coil L1 is connected between the pair of terminals 113a and 113b, the self-resonance characteristic of the second coil L2 has an effect and the characteristic deteriorates. Resulting in.

  FIG. 3 is a schematic diagram showing the relationship between two bands (low frequency and high frequency) that are operating frequencies and the self-resonance points of the first and second coils L1 and L2.

As shown in FIG. 3, the band B1 (first band) mainly using the inductance of the first coil L1 is naturally set to a band lower than the self-resonance point f1 of the _first coil L1. ing. Similarly, the band B2 (second band) mainly using the inductance of the second coil L2, of course, is set to a band lower than the self-resonance point f2 of the _second coil L2. However, if the self-resonant point f2 of the _second coil L2 exists in or near the first band B1, self-resonance occurs when the second coil L2 is opened, and the characteristics of the first band B1 Will have a big impact on

The influence of such self-resonance is eliminated by connecting the first and second coils L1 and L2 in parallel as described with reference to FIG. That is, when the first and second coils L1 and L2 are connected in parallel, the synthesized self-resonant point f _{1 + 2} moves to a frequency that is substantially the same as or close to the self-resonant point f ₁ of the first coil L1. To do. As a result, the self-resonance characteristic of the second coil L2 does not adversely affect the first band B1, and good characteristics can be obtained.

  On the contrary, when the first coil L1 is in an open state, the self-resonance characteristic of the first coil L1 hardly affects the second band B2. This point is taken into consideration in the second switching method shown in FIG.

In the second switching method, when the operating frequency is set to “low range”, the first switch SW1 is switched to the node B side and the second switch SW2 is turned off. As a result, only the second coil L2 is connected between the pair of terminals 113a and 113b, and the first coil L1 is in an open state. However, since the number of turns of the first coil L1 is smaller than that of the second coil L2, as shown in FIG. 3, the self-resonant point f ₁ of the first coil L1 is located inside or in the vicinity of the second band B2. Therefore, the self-resonance characteristic of the first coil L1 hardly has an adverse effect on the second band B2.

  In the second switching method, the control when the operating frequency is set to “high range” is the same as in the first switching method.

  When the second switching method is adopted, as is apparent from FIG. 2B, the first switch SW1 may remain fixed on the node B side. Therefore, when the second switching method is employed, the first switch SW1 can be omitted, and the number of parts can be reduced. On the other hand, when the first switching method is adopted, the first switch SW1 cannot be omitted, but a larger inductance value and Q value can be obtained. It is possible to increase the reception sensitivity when set to.

As described above, in the present embodiment, when the first band B1 on the high frequency side is selected as the operating frequency, the first and second coils L1 and L2 are connected in parallel. Even when the self-resonant point f2 of the _second coil L2 exists in or near the band B1, the adverse effect due to this can be avoided.

  Next, a second preferred embodiment of the present invention will be described.

  FIG. 4 is a circuit diagram showing a configuration of a radio receiving apparatus according to the preferred second embodiment of the present invention.

  As shown in FIG. 4, the wireless reception device 200 according to the present embodiment is mainly different from the wireless reception device 100 according to the first embodiment described above in the configuration of the antenna device 210. In the present embodiment, the bar antenna unit 211 constituting the antenna device 210 includes three coils L11, L12, and L13, and the switching circuit 212 includes a pair of terminals 213a and 213b and these three coils L11 and L12. , L13 are switchable.

More specifically, the coils L11, L12, and L13 included in the bar antenna unit 211 are all wound around the same core, and the number of turns is
L11 <L12 <L13
Is set to For this reason, the self-resonance points f ₁₁ , f ₁₂ , and f ₁₃ of the coils L11, L12, and L13 are
f ₁₁ > f ₁₂ > f ₁₃
It is.

  As shown in FIG. 4, the switching circuit 212 has four switches SW11 to SW14. The switch SW11 has three nodes F, G, and H, and is a switch that connects either the node F or the node G to the node H. Here, the node F is a node connected to one end L11a of the coil L11, and the node G is a node connected to the other end L11b of the coil L11. The node H is a node connected to one end L12a of the coil L12. The switch SW11 having such a configuration is switched by a control signal P11 supplied from the control circuit 230.

  The switch SW12 has three nodes I, J, and K, and is a switch that connects either the node J or the node K to the node I. Here, the node I is a node connected to the other end L12b of the coil L12, and the node J is a node connected to one end L13a of the coil L13. The node K is a node connected to the other end L13b of the coil L13. The switch SW12 having such a configuration is switched by a control signal P12 supplied from the control circuit 230.

  Further, the switch SW13 has two nodes L and M, and is a switch for selecting whether or not to connect the node L and the node M. Here, the node L is a node connected to the other end L11b of the coil L11, and the node M is a node connected to one end L13a of the coil L13. The switch SW13 having such a configuration is switched by a control signal P13 supplied from the control circuit 230.

  The switch SW14 has two nodes N and O, and is a switch for selecting whether or not to connect the node N and the node O. Here, the node N is a node connected to one end L11a of the coil L11, and the node O is a node connected to the other end L13b of the coil L13. The switch SW14 having such a configuration is switched by a control signal P14 supplied from the control circuit 230.

  As shown in FIG. 4, the other end L11b of the coil L11 is connected to a terminal 213a, and is connected to the receiving circuit 220 via this terminal 213a. Similarly, the other end L13b of the coil L13 is connected to the terminal 213b, and is connected to the receiving circuit 220 via this terminal 213b. The receiving circuit 220 is a circuit that detects and amplifies signals supplied from the pair of terminals 213a and 213b.

  Next, the operation of the wireless reception device 200 according to the present embodiment will be described focusing on the operation of the switching circuit 212.

  FIG. 5 is a table for explaining the connection state of the coil by switching the switch, and shows an example of a preferable switching method.

  First, when the operating frequency is set to “low range”, the switches SW11 and SW12 are switched to the nodes F and J, respectively, and both the switches SW13 and SW14 are turned off. As a result, the three coils L11, L12, and L13 are connected in series to the pair of terminals 213a and 213b. Here, since the coil L13 has more turns than the coils L11 and L12, the coil L13 is dominant as an obtained inductance value. Therefore, as the operating frequency, it is possible to use substantially the same frequency band as when the coil L13 is used alone.

  On the other hand, when the operating frequency is set to “high range”, the switches SW11 and SW12 are switched to the nodes G and K, respectively, and both the switches SW13 and SW14 are turned on (the state shown in FIG. 4 corresponds to this). As a result, the three coils L11, L12, and L13 are connected in parallel to the pair of terminals 213a and 213b. In this case, the coil L11 having a small number of turns is dominant as an inductance value to be obtained, and therefore, it is possible to use almost the same frequency band as the operating frequency when the coil L11 is used alone. In other words, even if one or both of the coils L12 and L13 are in an open state, the band does not change so much.

  However, if the self-resonant points of the coils L12 and L13 exist in or near the band, the coils L12 and L13 cause self-resonance, which greatly affects the characteristics in the band. On the other hand, if the coils L12 and L13 having a low self-resonance point are connected in parallel to the coil L11 as in the present embodiment, the self-resonance point moves to the higher frequency side, thus eliminating such problems. It becomes possible to do.

  Further, when the operating frequency is set to “middle range”, the switches SW11 and SW12 are switched to the nodes G and K, respectively, and the switches SW13 and SW14 are turned on and off, respectively. As a result, the coils L12 and L13 are connected in parallel to the pair of terminals 213a and 213b, and the coil L11 is opened. In this case, the coil L12 having a small number of turns is dominant as an inductance value to be obtained, and therefore, it is possible to use almost the same frequency band as that when the coil L12 is used alone as the operating frequency. In other words, even if L13 is in an open state, the bandwidth does not change so much.

  However, if a self-resonant point of the coil L13 exists in or near the band, the coil L13 causes self-resonance, which greatly affects the characteristics in the band. On the other hand, if the coil L13 having a low self-resonance point is connected in parallel to the coil L12, the self-resonance point moves to the higher frequency side, so that such a problem can be solved.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in the above embodiment, an example in which two or three coils are wound around the same core has been described. However, the present invention is not limited to this, and two or more coils are wound on the same core. It is possible to apply to all cases where is wound. Moreover, it is not essential that the number of turns and the self-resonance points of the plurality of coils are all different from each other, and the number of turns and the self-resonance points of any two or more coils may be the same.

  Furthermore, in the above-described embodiment, the operating frequencies that are switched by selection of the coils do not overlap each other (see FIG. 3), but the plurality of operating frequencies may partially overlap.

  The antenna device according to the present invention has a variable inductance function, so it is considered that other uses other than the antenna can be applied. However, the antenna device has a small core size due to its nature. For this reason, the advantages of sharing the same core for multiple operating frequencies are great, and the antenna device has a significant adverse effect due to self-resonance of other coils. In this case, it is extremely important that the object of the present invention is an antenna device.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  [Preparation of sample]

  First, a rod-shaped ferrite core having a size of 6 mm × 6 mm × 40 mm is prepared, and a polyurethane insulating coated copper wire 2 having a diameter of 0.12 mm is used as a coil (L1) for a short wave band (3 MHz to 30 MHz) around the ferrite core. The books were bundled in parallel and wound for 14 turns. Furthermore, as a coil (L2) for a medium wave band (530 kHz to 1700 kHz), two similar copper wires were wound in 75 turns in parallel. As a result, the total number of turns of L1 and L2 is 89 turns. Both coils were arranged at the approximate center of the ferrite core. A ferrite core having an initial permeability of about 80 in the above frequency band was used. Thereby, the bar antenna by the sample 1 was completed.

  Further, for comparison, the short-wave coil L1 is deleted from the sample 1, the sample 2 in which only the medium-wave coil L2 is wound, and the medium-wave coil L2 is deleted from the sample 1, and the short-wave Sample 3 in which only the strip coil L1 was wound was produced.

  [Evaluation of characteristics]

  Next, the inductance value and Q value were measured about the produced samples 1-3. Measurement of sample 1 includes a state where coils L1 and L2 are connected in parallel, a state where coils L1 and L2 are connected in series, a state where only coil L1 is connected (coil L2 is open), and a state where only coil L2 is connected Measurement was performed on four states (coil L1 is in an open state).

  The measurement results are shown in FIGS.

  FIG. 6 shows a state in which the coils L1 and L2 are connected in series in the sample 1 (denoted as “series”), a state in which only the coil L2 is connected in the sample 1 (denoted as “L2 (L1 open)”), and a sample Two measurement results are shown. These are data indicating characteristics when the operating frequency is switched to the medium wave band mainly by using the coil L2.

  As shown in FIG. 6, a high Q value and a stable inductance value were obtained in any of the measurement results in the medium wave band (530 kHz to 1700 kHz) that is the operating frequency. In particular, in sample 1 where coils L1 and L2 were connected in series, the highest Q value was obtained at the operating frequency.

  Although a sudden fluctuation in the inductance value due to the self-resonance of the coil L2 was observed in the vicinity of 22 to 23 MHz, there is no problem in practical use because this band is far away from the operating frequency.

  On the other hand, FIG. 7 shows a state in which coils L1 and L2 are connected in parallel in sample 1 (denoted as “parallel”), a state in which only coil L1 is connected in sample 1 (denoted as “L1 (L2 open)”), and The measurement result of Sample 3 is shown. These are data indicating characteristics when the operating frequency is switched to the short wave band mainly by using the coil L1.

  As shown in FIG. 7, in the state where the coils L1 and L2 are connected in parallel in the sample 1 and in the sample 3, a high Q value and a stable inductance value are obtained in the short wave band (3 MHz to 30 MHz) which is the operating frequency. On the other hand, in the state where only the coil L1 is connected in the sample 1, a rapid fluctuation of the inductance value and a significant decrease in the Q value were observed in the vicinity of 12 to 13 MHz due to the self-resonance of the coil L2. This is a fluctuation occurring within the operating frequency, and becomes a serious problem in practical use.

  As described above, when the operating frequency is switched to the short wave band by using the coil L1, by connecting the coils L1 and L2 in parallel, a rapid fluctuation or Q value of the inductance value in the band due to the self-resonance of the coil L2 can be obtained. It was confirmed that it was possible to prevent a significant drop in the.

1 is a circuit diagram showing a configuration of a wireless reception device according to a preferred first embodiment of the present invention. FIG. 3 is a table for explaining a connection state of coils by switching of switches included in the switching circuit shown in FIG. 1, wherein (a) shows a first switching method and (b) shows a second switching method. It is a schematic diagram which shows the relationship between the two zone | bands which are operating frequencies, and the self-resonance point of 1st and 2nd coil L1, L2. It is a circuit diagram which shows the structure of the radio | wireless receiving apparatus by preferable 2nd Embodiment of this invention. It is a table | surface for demonstrating the connection state of the coil by switching of the switch contained in the switching circuit shown in FIG. 4, and shows an example of the preferable switching method. In the embodiment, the data shows the characteristics when the operating frequency is switched to the medium wave band mainly by using the coil L2. In the examples, the data shows the characteristics when the operating frequency is switched to the short wave band mainly by using the coil L1.

Explanation of symbols

100, 200 Radio receiving device 110, 210 Antenna device 111, 211 Bar antenna unit 112, 212 Switching circuit 113a, 113b, 213a, 213b Terminal 120, 220 Reception circuit 130, 230 Control circuit L1, L2, L11-L13 Coil L1a, L2a, L11a to L13a One end of the coil L1b, L2b, L11b to L13b The other end of the coil SW1, SW2, SW11 to SW14 Switch A to O Nodes P1, P2, P11 to P14 Control signal

Claims (7)

A core, a plurality of coils each including at least a second coil wound around the core and having a self-resonance point lower than that of the first coil, a pair of terminals, and the pair of terminals And a switching circuit for switching the connection relationship between the plurality of coils,
The switching device connects the second coil in parallel to the first coil when both ends of the first coil are connected to the pair of terminals, respectively.   The antenna device according to claim 1, wherein the self-resonance point of the second coil is included in an operating frequency band of the first coil.   3. The switching circuit according to claim 1, wherein when the operating frequency band of the second coil is selected, the switching circuit connects the first and second coils in series to the pair of terminals. Antenna device.   3. The antenna device according to claim 1, wherein when the operating frequency band of the second coil is selected, the switching circuit connects both ends of the second coil to the pair of terminals, respectively. .   A core, a plurality of coils wound around the core, a pair of terminals, and the control signal representing the first state, the plurality of coils are connected in series to the pair of terminals. When the control signal represents the second state, the antenna device includes a switching circuit that connects the plurality of coils in parallel to the pair of terminals.   The antenna device according to claim 5, wherein self-resonant points of the plurality of coils are different from each other. A radio receiving apparatus comprising: the antenna apparatus according to claim 1; and a receiving circuit connected to the pair of terminals.

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