JP2005159813A - Multifrequency resonance type inverted f antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multifrequency resonance type inverted F antenna capable of efficiently transmitting / receiving a radio wave over all operating frequency bands. <P>SOLUTION: According to the frequency, the length of a radiation element comprising a first radiation element 11, a second radiation element 12, and a third radiation element 13 is changed by using a switching circuit comprising a first switching circuit 14 and a second switching circuit 19 and a distance from a feeding point to a short-circuit plate is changed by using the second switching circuit 19 comprising a capacitor 22. Thus, the small-sized inverted F antenna with high convenience can be realized, which can efficiently transmit / receive a radio wave over a plurality of the frequency bands. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a multi-frequency resonance type inverted-F antenna that is used in a wireless device that switches frequencies and uses radio waves at a plurality of frequencies.

  In recent years, standards for a plurality of wireless LAN systems having different frequencies have been established, and there is a demand for a small antenna that can be used in a plurality of frequency bands as an antenna connected to a wireless LAN device. As such an antenna, it is preferable to use an inverted F-type antenna whose overall length is as short as a quarter of the wavelength and which can be shortened, and to resonate the antenna at a plurality of frequencies. Conceivable.

  Therefore, conventionally, in an inverted-F antenna, a plurality of resonance circuits composed of a coil and a capacitor are provided, and the length of the radiating element and the distance from the feeding point to the short-circuit plate are switched according to the frequency. A resonating multi-frequency resonant inverted-F antenna is realized (see, for example, Patent Document 1).

  Hereinafter, a conventional multi-frequency resonance type inverted-F antenna described in Patent Document 1 will be described. FIG. 7 is a configuration diagram of a conventional multi-frequency resonance type inverted-F antenna, which is an antenna that resonates at a low first frequency f1 and a high second frequency f2.

  In FIG. 7, reference numeral 5 denotes a ground plate to which an outer conductor of a feeder line (coaxial cable) 6 is connected. Reference numeral 7 denotes a radiating element, which is provided on the ground plate 5 in parallel at a predetermined interval. A central conductor of the feeder line 6 is connected to a predetermined position of the radiating element portion 7, and the predetermined position is a feeding point P0.

  At a predetermined position between the feeding point P0 and the end portion P1 of the radiating element unit 7, a parallel resonant circuit 8 including the capacitor 1 and the coil 2 and having a resonance frequency equal to f2 is inserted.

  The other end P <b> 2 of the radiating element unit 7 is grounded to the ground plate 5 by a short pin 9. Between the other end P2 and the feeding point P0, a series resonance circuit 10 including a capacitor 3 and a coil 4 and having a resonance frequency equal to f1 is disposed at a predetermined position P3 of the radiating element portion 7 with the ground plate 5. Connected between.

  The length of the radiating element unit 7 coincides with a quarter (λ1 / 4) of the wavelength (hereinafter referred to as λ1) at the low first frequency f1, and the distance between the parallel resonant circuit 8 and the series resonant circuit 10 is This coincides with a quarter of the wavelength (hereinafter referred to as λ2) at the second high frequency f2 (λ2 / 4). Further, the feed point P0 is such that the ratio of the distance from the feed point P0 to the connection point P2 of the short pin 9 to λ1 and the ratio of the distance from the feed point P0 to the connection point P3 of the series resonant circuit 10 to λ2 coincide. A series resonant circuit 10 is installed.

  The operation of the conventional multi-frequency resonance type inverted-F antenna configured as described above will be described. Since the parallel resonant circuit 8 resonates at a high second frequency f2, when the frequency is f2, the radiating element portion 7 from the feeding point P0 to the point P4 before the parallel resonant circuit 8 functions as a radiating element. Since the length of this portion is λ2 / 4, the length of the radiating element is optimally adjusted at the frequency f2. On the other hand, at the first frequency f1, since the impedance of the parallel resonant circuit 8 is low, the portion from the feeding point P0 to the tip P1 of the radiating element unit 7 functions as a radiating element, and the length of the radiating element unit 7 is λ1 / 4. Therefore, the length of the radiating element is optimally adjusted even at the frequency f1.

  By the way, in the multi-frequency resonance type antenna, it is also necessary for matching the antenna and the high frequency signal source that the input impedance of the antenna does not change depending on the resonance frequency. In the inverted F-type antenna, the input impedance is largely related to the ratio of the distance from the feeding point to the short pin 9 with respect to the wavelength, so this ratio must be kept unchanged between the frequency f1 and the frequency f2.

  The series resonant circuit 10 has a low impedance at the frequency f2, short-circuits the radiating element portion 7 and the ground plate 5 at that point, and has a high impedance and an open state at the frequency f1. Further, the positions of the feed point P0 and the series resonant circuit 10 are set so that the ratio of the distance from the feed point P0 to the short pin 9 with respect to λ1 matches the ratio of the distance from the feed point P0 to the series resonant circuit 10 with respect to λ2. It has established. Therefore, at the frequency f1 and the frequency f2, the ratio of the distance from the feeding point P0 to the point P2 where the radiating element part 7 is short-circuited with each other matches, and the input impedance of the antenna can be kept at the same value.

In this way, the length of the radiating element and the distance from the feed point P0 to the ground point P2 are optimized at both the frequencies f1 and f2, so that radio waves can be efficiently transmitted and received at both frequencies. it can.
Japanese Patent Laid-Open No. 11-251825 (pages 1 to 4, FIG. 1)

  In the inverted F-type antenna that transmits and receives radio waves at the low frequency f1 and the high frequency f2, the impedance of the series resonance circuit is reduced when the frequency to be transmitted and received is away from the frequency f2 that is the resonance frequency of the series resonance circuit and the parallel resonance circuit. As the impedance increases in the parallel resonant circuit, a high-frequency signal reaches both ends of the radiating element, and the antenna no longer resonates at that frequency. Therefore, there is a problem that the frequency range in which radio waves near the high frequency f2 can be efficiently transmitted and received is limited to a narrow range.

  An object of the present invention is to solve the above-described problems and to provide a small and highly convenient multi-frequency resonance type inverted-F antenna that can efficiently transmit and receive radio waves in a plurality of frequency bands.

  The main feature of the present invention is that the length of the radiating element and the distance from the feeding point to the ground point are switched by a switch that switches between conduction and non-conduction.

  According to the multi-frequency resonant inverted-F antenna of the present invention, a switch that can switch between conduction and non-conduction at a wide frequency and that does not use the resonance phenomenon of the circuit is used. By switching the distance to the ground point, a small and highly convenient inverted F-type antenna that can efficiently transmit and receive radio waves in a plurality of frequency bands can be realized.

  The object of the present invention is to provide a small and highly convenient antenna capable of efficiently transmitting and receiving radio waves in a plurality of frequency bands, with the length of the radiating element and the distance from the feed point to the ground point being conducted. It was realized by switching with a switch that switches between non-conduction and non-conduction.

A first invention made to solve the above problem is an inverted F-type antenna in which a radiating element is composed of a first radiating element part having a short circuit part and a second radiating element part having a feeding point. In the second radiating element portion, the first radiating element is disposed between the end opposite to the first radiating element portion with respect to the feeding point.
A multi-frequency resonance type in which a second switching circuit is provided between a point between the end on the first radiating element side with respect to the feeding point and the ground in the second radiating element part. This is an inverted F-type antenna, and has an effect of efficiently transmitting and receiving radio waves in a wide band at both low and high frequencies at which the antenna resonates.

  A second invention made to solve the above-described problem is a second radiating element in which the radiating element is separated from the first radiating element part and the first radiating element part in a DC manner and coupled in an AC manner. The radiating element unit is constituted by a third radiating element unit which is separated from the second radiating element unit in a direct current and is coupled in an alternating manner, and the first radiating element unit is provided with a short-circuit portion, The radiating element portion is provided with a feeding point, a first switching circuit is provided in the middle of the third radiating element portion, and in the second radiating element portion, the end of the first radiating element side with respect to the feeding point is provided. A multi-frequency resonant inverted F-type antenna having a second switching circuit provided between the point in between and the ground, the switching circuit can be switched by electrical means, and a low frequency at which the antenna resonates, Efficient power over a wide band at both high frequencies It is possible to transmit and receive, the switching frequency is easy, has the effect of enhanced usability of the antenna.

  According to a third aspect of the invention made to solve the above-described problem, the radiating element is a first radiating element part, and a second radiating element part is separated from the first radiating element part in a DC manner and coupled in an AC manner. The first radiating element portion is provided with a short-circuit portion, the second radiating element portion is provided with a feeding point, and the second radiating element portion is provided between the feeding point and the end portion. 1 is a multi-frequency resonance type inverted F-type antenna provided with a second switching circuit between a feeding point of the second radiating element section, an end on the first radiating element side, and a ground. And has the effect of simplifying the structure of the multi-frequency resonant inverted-F antenna.

  A fourth invention made to solve the above problems is the multi-frequency resonant inverted F antenna according to the second or third invention, wherein the control signal voltages of the first switching circuit and the second switching circuit are obtained. The second radiating element unit, or a multi-frequency resonant inverted F-type antenna that is applied via the second radiating element unit and the antenna feed line. It works to simplify.

  A fifth invention made to solve the above problems includes a first radiating element portion, and a second radiating element portion that is separated from the first radiating element portion in a DC manner and coupled in an AC manner. A radiating element, a short-circuit portion provided in the first radiating element portion, a feeding point provided in the second radiating element portion, and a feeding point and a second radiating element portion in the second radiating element portion. A first switching circuit provided at an arbitrary portion between the first radiating element portion and the end portion not facing the first radiating element portion; and a second radiating element portion, wherein the second radiating element portion and the first radiating element portion are A multi-frequency resonance type inverted-F antenna having a second switching circuit for connecting an arbitrary portion between an end portion facing the radiating element portion and the power feeding portion and the ground is provided. Multi-frequency resonance by arranging the circuit and the second switching circuit in any part It has the effect of simplifying the structure of the inverted-F antenna.

A sixth invention made to solve the above-described problems includes a first radiating element portion, a second radiating element portion that is separated from the first radiating element portion in a direct current and is coupled in an alternating manner. A radiating element having a third radiating element part that is DC-coupled and AC-coupled to the second radiating element part, a short-circuit part provided in the first radiating element part, and a second A feed point provided in the radiating element unit, a first switching circuit provided in an arbitrary portion of the third radiating element unit, and a second radiating element unit, the feeding point and the first radiating element unit Is a multi-frequency resonant inverted F antenna having a second switching circuit that connects between an arbitrary portion between the opposite ends and the ground, and the switching circuit can be switched by electric means. , Low frequency, high frequency of antenna resonance In person, it is possible to transmit and receive efficiently wave over a wide band, the switching frequency is easy, has the effect of enhanced usability of the antenna.

  According to a seventh invention for solving the above-mentioned problems, in any one of the first to sixth inventions, at least one or all of the first switching circuit and the second switching circuit are constituted by pin diodes. The multi-frequency resonance type inverted F antenna has a function that each switching circuit is constituted by one diode element.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

(Embodiment 1)
FIG. 1 is a configuration diagram of an antenna showing an embodiment of the present invention, which is a two-frequency resonance type inverted F antenna that can be used at two frequencies, a low first frequency f1 and a high second frequency f2. .

  FIG. 2 is a diagram for explaining the operation of the antenna shown in FIG. 1, and shows the electric field strength distribution when the antenna shown in FIG. 1 resonates at the frequency f1 and when it resonates at the frequency f2.

  In these figures, reference numeral 5 denotes a ground plate made of a metal plate, to which an outer conductor of a feeder line (coaxial cable) 6 is connected. On the ground plate 5, a first radiating element portion 11, a second radiating element portion 12, and a third radiating element portion 13 are provided in parallel with the ground plate 5. The center conductor of the feeder 6 is connected to the second radiating element portion 12, and this is the feeder point P0. Reference numeral 14 denotes a pin diode used as a switching element, which is connected between the third radiating element sections 13. The pin diode 14 constitutes a first switching circuit.

  A bias control circuit 15 controls the bias voltage of the pin diode 14. Reference numerals 16 and 17 denote low-pass filters. The low-pass filters 16 and 17 pass the bias signal from the bias control circuit 15 and block the passage of the frequency signal f1 and the signal of the frequency f2. The pin diode has a high impedance when no bias voltage is applied, but the impedance decreases when a bias voltage is applied. Therefore, the conduction and non-conduction of the pin diode 14 as the first switching circuit can be switched by the bias signal from the bias control circuit 15.

  A capacitor 18 is connected between the second radiating element section 12 and the third radiating element section 13, and separates the second radiating element section and the third radiating element section 13 from each other in a direct current manner. Connect. Reference numeral 19 denotes a pin diode used as a switching element, which is connected between the end of the second radiating element section 12 on the first radiating element section 11 side and the ground plate 5. The pin diode 19 constitutes a second switching circuit. A bias control circuit 20 controls the bias voltage of the pin diode 19. Reference numeral 21 denotes a low-pass filter, which allows a bias signal from the bias control circuit 20 to pass therethrough and prevents passage of a signal having a frequency f1 or a frequency f2. Similarly to the first switching circuit (pin diode 14), the second switching circuit (pin diode 19) switches between conduction and non-conduction of the second switching circuit by a bias signal from the bias control circuit 20.

Note that the bias signal from the bias control circuit 15 can be applied only to the pin diode 14 and the bias signal from the bias control circuit 20 can be applied only to the pin diode 19 by the capacitor 18. A capacitor 22 is connected between the first radiating element unit 11 and the second radiating element unit 12 to separate the first radiating element unit 11 and the second radiating element unit 12 in a direct current manner. Connect with high frequency. The anode terminal of the pin diode 19 is DC-isolated from the ground plate 5 by the capacitor 22 so that a bias voltage can be applied. Reference numeral 23 denotes a short-circuit plate, and the other end of the first radiating element unit 11 is grounded to the ground plate 5. 2
4 is a capacitor, and 25 is a high-frequency signal source. The capacitor 24 is connected between the feeding point P0 and the high frequency signal source 25, and prevents the bias signal from the bias control circuit 20 from being input to the high frequency signal source 25.

  The combined length of the first radiating element unit 11, the second radiating element unit 12, and the third radiating element unit 13 is equal to λ1 / 4, and the second radiating element unit 12 And the length to the pin diode 14 of the 3rd radiation | emission element part 13 corresponds with (lambda) 2/4. The feeding point P0 is provided at a point where L1: λ1 = L2: λ2 in FIG.

  The operation of the inverted F antenna configured in this way will be described. When the pin diode 14 that is the first switching circuit is turned on and the pin diode 19 that is the second switching circuit is turned off, the antenna resonates at the lower first frequency f1 as shown in FIG. .

  Further, when the first switching circuit (pin diode 14) is made non-conductive and the second switching circuit (pin diode 19) is made conductive, the third radiating element 13 reaches the first switching circuit (pin diode 14). 2 is coupled to the second radiating element portion 12, and the second radiating element portion 12 is short-circuited to the ground plate 5 by the second switching circuit (pin diode 19), as shown in FIG. The antenna resonates at the higher second frequency f2.

  In this way, by switching between conduction and non-conduction of the first switching circuit (pin diode 14) and the second switching circuit (pin diode 19), the resonance frequency of the antenna can be switched, and the conduction of the switching circuit. Is switched between whether the impedance of the switching element is high and open or low and short-circuited, so that the antenna can resonate in a wider band than when using a resonant circuit. it can.

  In the antenna shown in FIG. 1, a bias signal is applied to the second switching circuit (pin diode 19) via the second radiating element section 12, and the bias signal is applied to the first switching circuit (pin diode 14). By applying it through the third radiating element section 13, the two bias control circuits 15 and 20 can be arranged close to each other, and the antenna and the bias control circuits 15 and 20 are simply compact inverted F Type antenna is realized.

  By the way, the input impedance of the inverted F-type antenna is largely related to the ratio of the length from the feeding point P0 to the short-circuit plate 23 with respect to the wavelength. In the antenna of FIG. 1, the lower frequency f1 and the higher frequency f2 are used. Since the ratio is kept constant, the input impedance can be kept constant at either frequency, and matching can be achieved with the high-frequency signal source at both frequencies.

  Of course, it is possible to switch between three or more frequencies by increasing the number of switching circuits provided between the feeding point P0 and the short-circuit plate 23 and the number of switching circuits on the opposite side of the short-circuit plate 23. It is. The antenna can be made to resonate at each frequency, the input impedance can be kept constant, and matching with the high-frequency signal source can be achieved.

In the first embodiment, the third radiating element portion 13 is divided into two in the longitudinal direction and the first switching circuit 14 is provided therebetween, but the position of the two divisions can be arbitrarily set. . Further, the second switching circuit 19 is provided at the end of the second radiating element section 12 on the first radiating element section 11 side, but it may be at an arbitrary position near the end. Thereby, the frequency f2 can be arbitrarily set within a predetermined range.

(Embodiment 2)
FIG. 3 is a diagram showing the structure of a multi-frequency resonance type inverted-F antenna according to an embodiment of the present invention. By controlling two switching circuits with one bias control circuit, a simple and small-sized inverted F antenna is shown. Type antenna is realized. FIG. 4 is a diagram for explaining the operation of the antenna shown in FIG. 3. In the antenna shown in FIG. 3, the electric field on the antenna when resonating at a low first frequency f1 and resonating at a high second frequency f2. The intensity distribution is shown.

  In these figures, reference numeral 5 denotes a ground plate made of a metal plate, to which an outer conductor of a feeder line (coaxial cable) 6 is connected. A first radiating element portion 11 and a second radiating element portion 12 are provided on the ground plate 5 in parallel with the ground plate 5. The center conductor of the feeder 6 is connected to the second radiating element portion 12, and this is the feeder point P0. Reference numeral 14 denotes a pin diode used as a switching element, and is inserted between the feeding point P 0 and the end of the second radiating element section 12 in the second radiating element section 12. The pin diode 14 constitutes a first switching circuit. A bias control circuit 15 controls the bias voltage of the pin diode 14.

  The low-pass filter 16 allows the bias signal from the bias control circuit 15 to pass and blocks the passage of the frequency f1 signal and the frequency f2 signal. Reference numeral 19 denotes a pin diode used as a switching element, which is connected between the end of the second radiating element section 12 on the first radiating element section 11 side and the ground plate 5. The bias voltage of the pin diode 19 is also controlled by the bias control circuit 15. The pin diode 19 constitutes a second switching circuit.

  A capacitor 22 separates the first radiating element unit 11 and the second radiating element unit 12 in a direct current manner and connects them in a high frequency manner. Reference numeral 23 denotes a short-circuit plate, and the other end of the first radiating element unit 11 is grounded to the ground plate 5. Reference numeral 26 denotes a short-circuit plate, and the other end of the second radiating element portion 12 is grounded to the ground plate 5. Reference numeral 24 denotes a capacitor, and reference numeral 25 denotes a high-frequency signal source. The capacitor 24 prevents the bias signal from the bias control circuit 20 from flowing into the high frequency signal source 25.

  The combined length of the first radiating element portion 11 and the portion of the second radiating element portion 12 up to the first switching circuit is equal to λ1 / 4, and the second radiating element portion The length of the portion 12 coincides with λ2 / 2. In addition, the feeding point is provided at a point where L1: λ1 = L2: λ2 in FIG.

  The operation of the inverted F antenna configured in this way will be described. When the first switching circuit (pin diode 14) and the second switching circuit (pin diode 19) are made non-conductive, second switching of the first radiating element unit 11 and the second radiating element unit through which a high-frequency signal flows. The length to the circuit (pin diode 19) is equal to λ1 / 4, and the antenna resonates at a low first frequency f1, as shown in FIG. When the first switching circuit (pin diode 14) and the second switching circuit (pin diode 19) are made conductive, the second radiating element section 12 is grounded to the ground plate 5 at both ends. Since it is equal to / 2, as shown in FIG. 4, the antenna resonates at a high second frequency f2.

  Thus, the resonance frequency of the antenna can be switched by switching between conduction and non-conduction of the first switching circuit (pin diode 14) and the second switching circuit (pin diode 19). In addition, since the switching circuit is turned on and off by the impedance of the switching element, the antenna can resonate in a wider band than when a resonance circuit is used.

  Further, in the antenna of FIG. 3, the ratio of the length from the feeding point to the short-circuit plate with respect to the wavelength does not change between the frequency f1 and the frequency f2, and the feeding point P0 and the second switching circuit (pin diode 19). ). Therefore, the input impedance of the antenna is kept constant, and matching with the high-frequency signal source can be achieved at both frequencies.

  As shown in FIG. 3, the distance from the feeding point P0 to the point where the electric field intensity becomes zero at the higher frequency f2 is from the feeding point P0 to the point where the electric field intensity becomes maximum at the lower frequency f1. 2 is grounded to the ground plate 5 at the point where the electric field strength becomes zero at the higher frequency f2, and the electric field strength is maximized at the lower frequency f1. By inserting one switching circuit (pin diode 14), the conduction and non-conduction of the first switching circuit (pin diode 14) and the second switching circuit (pin diode 19) can be switched simultaneously to change the resonance frequency of the antenna. It becomes possible to switch, and only one bias control circuit for controlling the switching circuit is required. Further, the control signal is transmitted by superposing the feeder 6 and the second radiating element section 12 to control the first switching circuit (pin diode 14) and the second switching circuit (pin diode 19). Wiring for sending can be eliminated. In this manner, a simple and small antenna can be realized even though one antenna can cope with a plurality of frequencies.

  In the second embodiment, the second radiating element portion 12 is divided into two in the longitudinal direction and the first switching circuit 14 is provided therebetween, but the position of the two divisions can be arbitrarily set. . Further, the second switching circuit 19 is provided at the end of the second radiating element section 12 on the first radiating element section 11 side, but it may be at an arbitrary position near the end. Thereby, the frequency f2 can be arbitrarily set within a predetermined range.

(Embodiment 3)
FIG. 5 is a diagram showing the structure of a multi-frequency resonance type inverted-F antenna according to an embodiment of the present invention. By controlling two switching circuits with one bias control circuit, a simple and small-sized inverted F antenna is shown. Type antenna is realized. FIG. 6 is a diagram for explaining the operation of the antenna shown in FIG. 5. In the antenna shown in FIG. 5, the electric field intensity on the antenna when resonating at a low first frequency f1 and resonating at a high second frequency f2. The distribution is shown.

  In these drawings, reference numeral 5 denotes a ground made of a metal plate, to which an outer conductor of a feeder line (coaxial cable) 6 is connected. A first radiating element portion 11 and a second radiating element portion 12 are provided on the ground plate 5 in parallel with the ground plate 5. The center conductor of the feeder 6 is connected to the second radiating element portion 12, and this is the feeder point P0. A pin diode 14 is used as a switching element, and is inserted between the feeding point and the end of the second radiating element unit 12 in the second radiating element unit 12. The pin diode 14 constitutes a first switching circuit. A bias control circuit 15 controls the bias voltage of the pin diode 14. The low-pass filter 16 allows the bias signal from the bias control circuit 15 to pass and blocks the passage of the frequency f1 signal and the frequency f2 signal.

  Reference numeral 19 denotes a pin diode used as a switching element, which is connected between the end of the second radiating element section 12 on the first radiating element section 11 side and the ground plate 5. The pin diode 19 constitutes a second switching circuit. A capacitor 22 separates the first radiating element unit 11 and the second radiating element unit 12 in a direct current manner and connects them in a high frequency manner. Reference numeral 23 denotes a short-circuit plate, and the other end of the first radiating element unit 11 is grounded to the ground plate 5. A capacitor 24 prevents the bias signal from the bias control circuit 20 from flowing into the high-frequency signal source 25.

  Note that the total length of the first radiating element unit 11 and the second radiating element unit 12 is equal to λ1 / 4, and the first radiating element unit 11 of the second radiating element unit 12 is the same. The length from the end on the side to the first switching circuit is equal to λ2 / 2. The feeding point is provided at a point where L1: λ1 = L2: λ2 in FIG.

  The operation of the inverted F antenna configured in this way will be described. When the first switching circuit (pin diode 14) and the second switching circuit (pin diode 19) are made non-conductive, a high-frequency current flows through the first radiating element unit 11 and the second radiating element unit 12, and its length The length is equal to λ1 / 4, and the antenna resonates at the frequency f1 as shown in FIG. When the first switching circuit (pin diode 14) and the second switching circuit (pin diode 19) are made conductive, the second radiating element section 12 includes the first switching circuit (pin diode 14) and the second switching circuit. Although it is grounded to the ground plate 5 at (pin diode 19), the length is equal to 2λ / 2, so that the antenna resonates at a frequency f2, as shown in FIG.

  Thus, the resonance frequency of the antenna can be switched by switching between conduction and non-conduction of the first switching circuit (pin diode 14) and the second switching circuit (pin diode 19). Further, since the switching circuit is switched on and off by the impedance of the switching element as in the first and second embodiments, the antenna is resonated in a wider band than when a resonance circuit is used. be able to.

  In the antenna of FIG. 5 as well, since the ratio of the length from the feeding point P0 to the short-circuit plate 23 with respect to the wavelength does not change at the two frequencies, the input impedance is kept constant and matched with the high-frequency signal source at both frequencies. Can be taken.

  Further, as shown in FIG. 6, the distance from the feeding point P0 to the point where the electric field strength becomes zero at the higher frequency f2 is from the feeding point P0 to the point where the electric field strength becomes the maximum at the lower frequency f1. The first switching circuit (pin diode 14) and the second switching are grounded to the ground plate 5 by the first switching circuit at the point where the electric field strength becomes zero at the lower frequency f1 when the distance is shorter than. The circuit (pin diode 19) can be switched on and off at the same time to switch the resonance frequency of the antenna, and only one bias control circuit is required to control the switching circuit.

  Further, the control signal is transmitted by superposing the feeder 6 and the second radiating element section 12 to control the first switching circuit (pin diode 14) and the second switching circuit (pin diode 19). Wiring can be eliminated. In this manner, a simple and small antenna can be realized even though one antenna can cope with a plurality of frequencies.

  In the third embodiment, the second switching circuit 19 is provided at the end of the second radiating element section 12 on the first radiating element section 11 side. However, any position near the end may be used. Thereby, the frequency f2 can be arbitrarily set within a predetermined range.

  As described above, the multi-frequency resonant inverted-F antenna according to the present invention is useful for a wireless communication device using a plurality of frequencies, and is particularly suitable for being used as an antenna for a wireless LAN device that is required to be downsized. Yes.

Configuration diagram of an antenna showing an embodiment of the present invention Operational explanatory diagram of the antenna shown in FIG. The figure which shows the structure of the multifrequency resonance type | mold inverted F type antenna in one embodiment of this invention Operational explanatory diagram of the antenna shown in FIG. The figure which shows the structure of the multifrequency resonance type | mold inverted F type antenna in one embodiment of this invention Operational explanatory diagram of the antenna shown in FIG. Configuration diagram of conventional multi-frequency resonance type inverted-F antenna

Explanation of symbols

1 Capacitor 2 Coil 3 Capacitor 4 Coil 5 Ground plate 6 Feed line (coaxial cable)
DESCRIPTION OF SYMBOLS 7 Radiation element part 8 Parallel resonance circuit 9 Short pin 10 Series resonance circuit 11 1st radiation element part 12 2nd radiation element part 13 3rd radiation element part 14 Pin diode (1st switching circuit)
DESCRIPTION OF SYMBOLS 15 Bias control circuit 16 Low-pass filter 17 Low-pass filter 18 Capacitor 19 Pin diode (2nd switching circuit)
20 Bias control circuit 21 Low-pass filter 22 Capacitor 23 Short-circuit plate 24 Capacitor 25 High-frequency signal source 26 Short-circuit plate (short-circuit part)

Claims (7)

The radiating element is an inverted F-type antenna composed of a first radiating element part having a short circuit part and a second radiating element part having a feeding point,
In the second radiating element portion, a first switching circuit is provided between an end opposite to the first radiating element portion with respect to the feeding point and a ground.
In the second radiating element section, a second switching circuit is provided between a point between the end on the first radiating element section side with respect to the feeding point and a ground. Resonant inverted F type antenna. A radiating element includes a first radiating element part, a second radiating element part that is separated from the first radiating element part in a direct current manner and coupled in an alternating manner, and the second radiating element part and the direct current. And a third radiating element portion that is separated and connected in an alternating manner,
The first radiating element portion is provided with a short-circuit portion,
The second radiating element portion is provided with a feeding point,
Providing a first switching circuit in the middle of the third radiating element section;
In the second radiating element portion, a second switching circuit is provided between a point between the end on the first radiating element side with respect to the feeding point and a ground, and the multi-frequency resonance is provided. Type inverted F type antenna. The radiating element is composed of a first radiating element part and a second radiating element part that is separated from the first radiating element part in a direct current and coupled in an alternating manner,
The first radiating element portion is provided with a short-circuit portion,
The second radiating element portion is provided with a feeding point,
A first switching circuit is provided between the feeding point and the end of the second radiating element portion;
A multi-frequency resonance type inverted F type characterized in that a second switching circuit is provided between the feeding point of the second radiating element portion, the end on the first radiating element side, and a ground. antenna. The control signal voltage of the first switching circuit and the second switching circuit is applied via the second radiating element unit or the second radiating element unit and an antenna feed line. The multi-frequency resonant inverted-F antenna according to claim 2 or 3. A radiating element having a first radiating element part and a second radiating element part separated from the first radiating element part in a DC manner and coupled in an AC manner;
A short-circuit portion provided in the first radiating element portion;
A feeding point provided in the second radiating element section;
In the second radiating element portion, a first switching provided at an arbitrary portion between the feeding point and an end portion of the second radiating element portion on the side not facing the first radiating element portion. In the circuit and the second radiating element part, a second part connecting between the second radiating element part, an end facing the first radiating element part, and a power feeding part, and a ground. And a multi-frequency resonance type inverted F-type antenna. A first radiating element part, a second radiating element part that is DC-coupled and AC-coupled to the first radiating element part, and dc-separated from the second radiating element part. And a radiating element having a third radiating element portion coupled in an alternating manner;
A short-circuit portion provided in the first radiating element portion;
A feeding point provided in the second radiating element section;
A first switching circuit provided at an arbitrary portion of the third radiating element portion;
The second radiating element unit includes a second switching circuit that connects between an arbitrary portion between the feeding point and an end facing the first radiating element unit and a ground. Multi-frequency resonant inverted F type antenna. 7. The multi-frequency resonant inverted F antenna according to claim 5, wherein at least one or all of the first switching circuit and the second switching circuit are configured by pin diodes.

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