Patent Grant
7808435
1. Technical Field
The present invention relates to antenna structures provided in wireless communication apparatuses, such as cellular phones, and to wireless communication apparatuses including the antenna structures.
2. Background Art
a is a schematic perspective view showing an example of an antenna structure (e.g., refer to Patent Document 1). The antenna structure 40 includes a dielectric base 41 having a rectangular parallelepiped shape, and a ground electrode 42 is formed on the bottom surface of the dielectric base 41. Furthermore, on the top surface of the dielectric base 41, a driven radiating or feeding electrode 43 and a parasitic radiating or non-feeding electrode 44 are provided adjacent to each other, separated by a slit s1. On a side surface of the dielectric base 41, a connecting electrode 45 and a connecting electrode 46, spaced from each other. The connecting electrode 45 serves to electrically connect the driven radiating electrode 43 and the ground electrode 42. The connecting electrode 46 serves to electrically connect the parasitic radiating electrode 44 and the ground electrode 42.
On a side surface of the dielectric base 41 opposing the surface on which the connecting electrodes 45 and 46 are formed, a feeding electrode 47 for the driven radiating electrode is formed, and a frequency controlling electrode 48 is also formed. An upper end of the feeding electrode 47 is provided with a space from the driven radiating electrode 43 so as to form a capacitor with the driven radiating electrode 43. A lower end of the feeding electrode 47 is formed so as to extend to the bottom surface of the dielectric base 41. The lower end of the feeding electrode 47 is provided with a space from the ground electrode 42, and the lower end of the feeding electrode 47 is electrically connected to, for example, a high-frequency circuit 50 for wireless communication provided in a wireless communication apparatus. An upper end of the frequency controlling electrode 48 is provided with a space from the driven radiating electrode 43 and with a space from the parasitic radiating electrode 44 so as to form capacitors C1 and C2 with the driven radiating electrode 43 and the parasitic radiating electrode 44, respectively. A lower end of the frequency controlling electrode is formed so as to extend to the bottom surface of the dielectric base 41. The lower end of the frequency controlling electrode 48 is provided with a space from the ground electrode 42. Furthermore, the lower end of the frequency controlling electrode 48 is grounded via switching means 51, for example, to the ground of a wireless communication apparatus.
In the antenna structure 40 shown in
The resonant operation (multiple resonant operation) of the driven radiating electrode 43 and the parasitic radiating electrode 44 is an antenna operation that sends the signal to send wirelessly to the outside. Furthermore, when a signal from the outside has reached the driven radiating electrode 43 and the parasitic radiating electrode 44, the driven radiating electrode 43 and the parasitic radiating electrode 44 resonate according to the received signal, whereby the received signal is transmitted from the driven radiating electrode 43 to the feeding electrode 47 and further to the high-frequency circuit 50 for wireless communication. The resonant operation of the driven radiating electrode 43 and the parasitic radiating electrode 44 according to the wireless communication signal from the outside, described above, is an antenna operation for reception.
In the antenna structure 40, the frequency controlling electrode 48 forms capacitors individually with the driven radiating electrode 43 and the parasitic radiating electrode 44, and the frequency controlling electrode 48 is grounded via the switching means 51. With this configuration, in the antenna structure 40, it is possible to switch the resonant frequency bands of the driven radiating electrode 43 and the parasitic radiating electrode 44 as described below. For example, let it be supposed that when the switching means 51 is OFF so that the frequency controlling electrode 48 is not grounded, for example, the driven radiating electrode 43 has a resonant frequency band indicated by a dotted line A having a resonant frequency f1 shown in
On the other hand, when the switching means 51 becomes ON so that the frequency controlling electrode 48 is grounded, capacitors are formed with the ground between the driven radiating electrode 43 and the frequency controlling electrode 48 and the parasitic radiating electrode 44 and the frequency controlling electrode 48. Thus, a capacitance with the ground is loaded to the driven radiating electrode 43, and also a capacitance with the ground is loaded to the parasitic radiating electrode 44.
c shows an equivalent circuit of the driven radiating electrode 43 by solid lines. Since the resonant operation of the driven radiating electrode 43 is an LC resonance of an inductance component L and a capacitance component C of the driven radiating electrode 43, shown in
In this antenna structure, when the switching means 51 is OFF, the frequency bands for wireless communication by antenna operations of the driven radiating electrode 43 and the parasitic radiating electrode 44 fall in a frequency range of, for example, a frequency fm to a frequency fn shown in
Thus, for example, in a case where the configuration for frequency switching described above is provided, the antenna structure 40 can support wireless communication in the frequency range of, for example, the frequency fm′ to the frequency fn′. That is, it is possible to increase the frequency band of the antenna structure 40. This is in contrast to a case where no configuration for frequency switching by the frequency controlling electrode 48 is provided, in which the frequency bands for wireless communication by antenna operations of the driven radiating electrode 43 and the parasitic radiating electrode 44 fall only in the frequency range of, for example, the frequency fm to the frequency fn.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2001-168634
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2005-150937
Recently, there exists a demand for multi-band antennas that are compatible with a plurality of wireless communication systems that use frequency bands different from each other. Even with the antenna structure 40 having an increased bandwidth as described above, it has been difficult to satisfy the demand for multiple bands due to the insufficiency of frequency bands that can be used for wireless communication.
The disclosed antenna structure solves the problems described above by the following configurations. One configuration is as follows:
An antenna structure in which a base is mounted in a ground region on a circuit board, which may have a wireless communication circuit formed thereon, the base has provided thereon a driven radiating electrode that is electrically connected to the wireless communication circuit and that performs antenna operations in a plurality of resonant frequency bands different from each other, a parasitic radiating electrode electromagnetically coupled to the driven radiating electrode is provided with a space from the driven radiating electrode, the driven radiating electrode is a radiating electrode having one end that serves as a feeding end electrically connected to the wireless communication circuit and the other end that serves as an open end, the driven radiating electrode has such a form that the feeding end and the open end thereof are provided adjacent to each other via a space so that a loop-shaped current path is formed between the feeding end and the open end, the parasitic radiating electrode performs an antenna operation with the driven radiating electrode through electromagnetic coupling with the driven radiating electrode so as to cause multiple resonance at least in a harmonic resonant frequency band, the harmonic resonant frequency band being higher than a base resonant frequency band, the base resonant frequency band being lowest among the plurality of resonant frequency bands of the driven radiating electrode, the antenna structure comprising:
capacitance loading means for loading a capacitance to a harmonic-mode zero-voltage region of the driven radiating electrode, the harmonic-mode zero-voltage region being a region where a voltage becomes zero or nearly zero in a harmonic mode, the harmonic mode being an antenna operation mode in the harmonic resonant frequency band;
a grounding conduction path that electrically connects a ground electrode with the capacitance loading means, the ground electrode being formed in the ground region on the circuit board; and
switching means, provided in the grounding conduction path, for switching conduction ON/OFF between the capacitance loading means and the ground electrode on the circuit board to control switching between ON and OFF of capacitance loading by the capacitance loading means to the harmonic-mode zero-voltage region of the driven radiating electrode, thereby switching a base resonant frequency in the base resonant frequency band of the driven radiating electrode.
Another configuration according to the present invention is as follows:
An antenna structure in which a base is mounted in a ground region on a circuit board, which may have a wireless communication circuit formed thereon, the base has provided thereon a driven radiating electrode that is electrically connected to the wireless communication circuit and that performs antenna operations in a plurality of resonant frequency bands different from each other, a parasitic radiating electrode electromagnetically coupled to the driven radiating electrode is provided with a space from the driven radiating electrode, the driven radiating electrode is a radiating electrode having one end that serves as a feeding end electrically connected to the wireless communication circuit and the other end that serves as an open end, the driven radiating electrode has such a form that the feeding end and the open end thereof are provided adjacent to each other via a space so that a loop-shaped current path is formed between the feeding end and the open end, the parasitic radiating electrode performs an antenna operation with the driven radiating electrode through electromagnetic coupling with the driven radiating electrode so as to cause multiple resonance at least in a harmonic resonant frequency band, the harmonic resonant frequency band being higher than a base resonant frequency band, the base resonant frequency band being lowest among the plurality of resonant frequency bands of the driven radiating electrode, the antenna structure comprising:
wherein option capacitance loading means for loading a capacitance to a harmonic-mode zero-voltage region of the driven radiating electrode is formed on the base, the harmonic-mode zero-voltage region being a region where a voltage becomes zero or nearly zero in a harmonic mode, the harmonic mode being an antenna operation mode in the harmonic resonant frequency band, and
wherein when the option capacitance loading means loads a capacitance to the harmonic-mode zero-voltage region of the driven radiating electrode, a grounding conduction path is formed between the option capacitance loading means and a ground electrode formed in the ground region on the circuit board so that a capacitance is loaded to the harmonic-mode zero-voltage region of the driven radiating electrode, and when the option capacitance loading means does not load a capacitance to the harmonic-mode zero-voltage region of the driven radiating electrode, a grounding conduction path is not formed.
Furthermore, a wireless communication apparatus includes an antenna structure having a configuration characteristic as described herein.
As described herein, a base in an antenna structure has formed thereon a driven radiating electrode and a parasitic radiating electrode, and the parasitic radiating electrode is configured to cause multiple resonance with the driven radiating electrode by performing an antenna operation at least in a harmonic resonant frequency band of the driven radiating electrode. The multiple resonance by the parasitic radiating electrode in the harmonic resonant frequency band of the driven radiating electrode serves to increase the bandwidth in the harmonic resonant frequency band of the driven radiating electrode.
Furthermore, capacitance loading means for loading a capacitance to a harmonic-mode zero-voltage region of the driven radiating electrode, a grounding conduction path that electrically connects the capacitance loading means with the ground electrode on the circuit board, and switching means, provided in the grounding conduction path, for switching ON/OFF of conduction between the capacitance loading means and the ground electrode are provided. When the switching means is ON, the capacitance loading means is grounded to the ground electrode, so that the capacitance loading means loads a capacitance formed between the harmonic-mode zero-voltage region of the driven radiating electrode and the ground to the harmonic-mode zero-voltage region of the driven radiating electrode (capacitance loading is ON). Thus, compared with a state where the switching means is OFF so that the capacitance is not loaded to the driven radiating electrode (capacitance loading is OFF), when capacitance loading is ON, the electrical length of the driven radiating electrode increases in accordance with the magnitude of the loaded capacitance, whereby the base resonant frequency of the driven radiating electrode is switched to become lower. The switching of the base resonant frequency of the driven radiating electrode serves to increase the bandwidth of the base resonant frequency band of the driven radiating electrode.
A portion of the driven radiating electrode where the capacitance is loaded by the capacitance loading means is the harmonic-mode zero-voltage region of the driven radiating electrode. Thus, through ON/OFF operation of the switching means, it is possible to switch only the base resonant frequency of the driven radiating electrode without changing the harmonic resonant frequency of the driven radiating electrode. More specifically, the magnitude of a voltage in the harmonic mode in the harmonic-mode zero-voltage region of the driven radiating electrode is zero or nearly zero. Thus, for the harmonic mode, even if the switching means is turned ON, the capacitance loaded by the capacitance loading means to the harmonic-mode zero-voltage region of the driven radiating electrode may be regarded as a very small one, so that the state is substantially equivalent to that in the case where the capacitance by the capacitance loading means is not loaded to the harmonic-mode zero-voltage region of the driven radiating electrode. Thus, even if the ON/OFF operation of the switching means is switched, the harmonic resonant frequency of the driven radiating electrode does not change. In contrast, the magnitude of a voltage in the base mode in the harmonic-mode zero-voltage region of the driven radiating electrode has such a value that the state is affected by capacitance loading by the capacitance loading means. Thus, by switching the ON/OFF of capacitance loading by the ON/OFF switching operation of the switching means, the base resonant frequency of the driven radiating electrode is switched.
That is, in the configuration, since the bandwidth of the harmonic resonant frequency band of the driven radiating electrode increases by multiple resonance with the parasitic radiating electrode so that it is possible to achieve a desired frequency band, it is desired that the harmonic resonant frequency band of the driven radiating electrode does not change. Taking this into consideration, without changing the harmonic resonant frequency band of the driven radiating electrode, by switching only the base resonant frequency of the driven radiating electrode through switching of the ON/OFF of capacitance loading by the capacitance loading means, it is possible to increase the base resonant frequency band of the driven radiating electrode.
As described above, it is possible to increase the bandwidths of both the base resonant frequency band and the harmonic resonant frequency band of the driven radiating electrode. Thus, it is readily possible to provide an antenna structure that is compatible with a plurality of wireless communication systems or apparatus that use frequency bands different from each other, and to provide a wireless communication system including such an antenna structure. Particularly, the base having formed thereon the driven radiating electrode and the parasitic radiating electrode is mounted in the ground region on the circuit board. Thus, the disclosed configuration is epoch-making in that although electric fields radiated from the driven radiating electrode and the parasitic radiating electrode are drawn closer to the ground electrode on the circuit board so that basically the width of one resonant band is narrow and it is difficult to increase the frequency bandwidth, it becomes readily possible to increase the bandwidths of a plurality of frequency bands as described above.
Furthermore, the driven radiating electrode has such a form that the feeding end and the open end thereof are provided adjacent to each other with a space therebetween, and a current path between the feeding end and the open end has a loop shape. Thus, advantageously, it becomes readily possible to adjust the base resonant frequency and the harmonic resonant frequency of the driven radiating electrode. That is, since the driven radiating electrode has such a form that the feeding end and the open end thereof are provided adjacent to each other with a space and a current path between the feeding end and the open end has a loop shape, a capacitor is formed between the feeding end and the open end. This capacitor contributes more to the harmonic resonant frequency than to the base resonant frequency. Therefore, with the capacitor between the feeding end and the open end, it is possible to adjust the harmonic resonant frequency of the driven radiating electrode without substantially changing the base resonant frequency. That is, for example, by setting the electrical length between the feeding end and the open end of the driven radiating electrode to be such an electrical length that a predetermined base resonant frequency is achieved, and setting the capacitor between the feeding end and the open end to have a such a magnitude that a predetermined harmonic resonant frequency is achieved, it is possible to adjust the base resonant frequency and the harmonic resonant frequency independently of each other. Thus, it becomes readily possible to set both the base resonant frequency and the harmonic resonant frequency of the driven radiating electrode individually to predetermined frequencies.
Furthermore, since the driven radiating electrode has such a shape that the current path between the feeding end and the open end has a loop shape, it is possible to increase the electrical length of the driven radiating electrode without increasing the size of the driven radiating electrode. Thus, it is possible to reduce the size of the base, i.e., to reduce the size of the antenna structure.
Other features and advantages will become apparent from the following description of embodiments, which refers to the accompanying drawings.
a is a perspective view schematically showing an antenna structure according to a first embodiment.
b is a schematic exploded view of the antenna structure shown in
c is a graph for explaining an example of return loss characteristics of the antenna structure according to the first embodiment.
a is a graph for explaining voltage distributions of a driven radiating electrode in the antenna structure according to the first embodiment.
b is a model diagram showing an image of an example of relationship between the driven radiating electrode and voltage distributions thereof.
a is a model diagram showing an antenna structure that serves as a comparative example for the antenna structure according to the first embodiment.
b is a model diagram showing an image of an example of relationship between the driven radiating electrode in the antenna structure shown in
a is a graph showing return loss characteristics of the antenna structure according to the first embodiment, obtained through experiments performed by the inventors.
b is a graph showing return loss characteristics of the antenna structure shown in
a is a graph showing results of measurement of return loss characteristics and maximum gain of the antenna structure according to the first embodiment at frequencies of 750 MHz to 1000 MHz, obtained through experiments performed by the inventors.
b is a graph showing results of measurement of return loss characteristics and maximum gain of the antenna structure shown in
a is a graph showing results of measurement of return loss characteristics and maximum gain of the antenna structure according to the first embodiment at frequencies of 1700 MHz to 2200 MHz, obtained through experiments performed by the inventors.
b is a graph showing results of measurement of return loss characteristics and maximum gain of the antenna structure shown in
a is a model diagram for explaining another example form of capacitance loading means.
b is a model diagram for explaining yet another example form of capacitance loading means.
c is a model diagram for explaining still another example form of capacitance loading means.
d is a model diagram for explaining a further example form of capacitance loading means.
e is a model diagram for explaining a still further example form of capacitance loading means.
a is a model diagram showing an example form of an antenna component in an antenna structure according to a second embodiment.
b is a model diagram showing an antenna structure having a configuration characteristic of the second embodiment.
c is a model diagram showing another antenna structure having a configuration characteristic of the second embodiment.
d is a model diagram showing yet another antenna structure having a configuration characteristic of the second embodiment.
e is a model diagram showing still another antenna structure having a configuration characteristic of the second embodiment.
a is a model diagram showing an antenna structure at a third embodiment.
b is a graph showing return loss characteristics of the antenna structure shown in
a is a model diagram showing an antenna structure according to a fourth embodiment.
b is a graph showing return loss characteristics of the antenna structure shown in
a is a model diagram showing an antenna structure having a configuration characteristic of a fifth embodiment.
b is a model diagram showing another antenna structure having a configuration characteristic of the fifth embodiment.
a is a model diagram showing an antenna structure having a configuration characteristic of a sixth embodiment.
b is a model diagram showing another antenna structure having a configuration characteristic of the sixth embodiment.
c is a model diagram showing yet another antenna structure having a configuration characteristic of the sixth embodiment.
a is a schematic perspective view showing a known antenna structure;
b is a graph showing resonant frequency bands of the antenna structure;
c is a schematic diagram of an equivalent circuit.
Now, embodiments of the antenna structure will be described with reference to the drawings.
a is a schematic perspective view showing an antenna structure according to a first embodiment, and
In the first embodiment, on a top surface of the base 2, a driven radiating or feeding electrode 6 and a parasitic radiating or non-feeding electrode 7 are disposed adjacent to each other via (i.e., separated by) a space S. The driven radiating electrode 6 has an L-shaped slit 8 formed therein so as to cut into the driven radiating electrode 6 from an end edge of the electrode 6. At the end edge of the driven radiating electrode 6 on the side of the opening of the cutting of the slit 8, with the slit 8 in the middle, one side Q serves as a feeding end and the other side K serves as an open end. Since the feeding end Q and the open end K are disposed adjacent to each other via the slit 8 in the driven radiating electrode 6 as described above, a current path between the feeding end Q and the open end K has a loop shape extending around the slit 8 and connecting the feeding end Q and the open end K. By forming the slit 8 in the driven radiating electrode 6 so that the driven radiating electrode 6 has a loop-shaped current path, it is possible to increase the electrical length of the driven radiating electrode 6 without increasing the size of the driven radiating electrode 6. Furthermore, compared with a case where a loop-shaped driving radiating electrode is formed using strip-shaped electrodes, it is possible to increase the electrode area of the driven radiating electrode 6. The increase in the electrode area serves to reduce current loss of the driven radiating electrode 6, and to increase the bandwidth of the frequency band of the driven radiating electrode 6.
On the circuit board 3, a wireless communication circuit (a high-frequency circuit) 10 is formed. Furthermore, on the surface of a region where the base 2 is mounted on the circuit board 3, a feeding electrode land 11 electrically connected to the wireless communication circuit 10 is provided in such a manner that the feeding electrode land 11 is electrically insulated from the ground electrode 4 via a space. On a side surface of the base 2, a driven electrode (not shown) for electrically connecting the feeding end Q of the driven radiating electrode 6 and the feeding electrode land 11 on the circuit board 3 is formed. The feeding end Q of the driven radiating electrode 6 is electrically connected to the wireless communication circuit 10 on the circuit board 3 via the driven electrode and the feeding electrode land 11. The driven radiating electrode 6 is electrically connected to the wireless communication circuit 10, and functions as a radiating electrode that performs antenna operations.
In the first embodiment, the driven radiating electrode 6 performs antenna operations in a plurality of resonant frequency bands different from each other. In this specification, a lowest resonant frequency band among the plurality of resonant frequency bands of the driven radiating electrode 6 will be referred to as a base resonant frequency band, and an antenna operation mode in the base resonant frequency band will be referred to as a base mode. Furthermore, a resonant frequency band that is higher than the base resonant frequency band will be referred to as a harmonic resonant frequency band, and an antenna operation in the harmonic resonant frequency band will be referred to as a harmonic mode.
On a side surface of the base 2, a capacitance loading electrode 12 that serves as capacitance loading means for loading a capacitance to the harmonic-mode zero-voltage region P of the driven radiating electrode 6 is formed. Furthermore, on the surface of the circuit board 3, an electrode land 13 electrically connected to the capacitance loading electrode 12 is formed in such a manner that the electrode land 13 is electrically insulated from the ground electrode 4 via a space. Furthermore, on the circuit board 3, a grounding conduction path 15 is formed. One end of the grounding conduction path 15 is electrically connected to the electrode land 13, and the other end thereof may be electrically connected to the ground electrode 4. That is, the grounding conduction path 15 is a conduction path for causing the capacitance loading electrode 12 to be grounded to the ground electrode 4 via the electrode land 13. In the grounding conduction path 15, switching means 16 for switching ON/OFF of the conduction of the grounding conduction path 15 is provided.
When the switching means 16 is ON, the capacitance loading electrode 12 is grounded to the ground electrode 4. Thus, a capacitor is formed between the harmonic-mode zero-voltage region P of the driven radiating electrode 6 and the capacitance loading electrode 12, so that a capacitance with the ground is loaded to the harmonic-mode zero-voltage region P. On the other hand, when the switching means 16 is OFF, the capacitance loading electrode 12 is electrically disconnected from the ground electrode 4 and becomes electrically floating. Thus, no capacitor is formed between the harmonic-mode zero-voltage region P of the driven radiating electrode 6 and the capacitance loading electrode 12, so that no capacitance by the capacitance loading electrode 12 with the ground is loaded to the harmonic-mode zero-voltage region P.
The parasitic radiating electrode 7 has one end M that serves as an open end and the other end N that serves as a shorted end. On a side surface of the base 2, a grounding electrode (not shown) for electrically connecting the shorted end of the parasitic radiating electrode 7 to the ground electrode 4 is formed. In the first embodiment, the parasitic radiating electrode 7 is designed so as to be electromagnetically coupled to the driven radiating electrode 6 so that the parasitic radiating electrode 7 together with the driven radiating electrode 6 performs an antenna operation and causes multiple resonance in the harmonic resonant frequency band of the driven radiating electrode 6.
The antenna structure 1 according to the first embodiment has the structure described above. In the antenna structure 1, it is possible to switch the base resonant frequency in the base resonant frequency band of the driven radiating electrode 6 as described below. For example, let it be assumed that, when the switching means 16 is OFF, the base resonant frequency of the driven radiating electrode 6 is, for example, a frequency Fb6 shown in
The width of change of the switching of the base resonant frequency of the driven radiating electrode 6 at the time of switching of the switching means 16 from OFF to ON corresponds to the magnitude of the capacitance between the harmonic-mode zero-voltage region P of the driven radiating electrode 6 and the capacitance loading electrode 12 (i.e., the capacitance between the harmonic-mode zero-voltage region P of the driven radiating electrode 6 and the ground, loaded to the harmonic-mode zero-voltage region P by the capacitance loading electrode 12). Thus, in the first embodiment, the space between the harmonic-mode zero-voltage region P of the driven radiating electrode 6 and the capacitance loading electrode 12, the electrode width of the capacitance loading electrode 12, and so forth are designed so that a capacitance is formed between the harmonic-mode zero-voltage region P of the driven radiating electrode 6 and the capacitance loading electrode 12, such that the base resonant frequency of the driven radiating electrode 6 becomes a predetermined frequency when the switching means 16 is ON.
Since the base resonant frequency band of the driven radiating electrode 6 can be switched as described above, the following advantage can be achieved. Let it be supposed that, for example, a wireless communication system A performs wireless communication using a frequency band A shown in
Furthermore, in the first embodiment, since the capacitance by the capacitance loading electrode 12 is loaded to the harmonic-mode zero-voltage region P of the driven radiating electrode 6, the multiple resonance by the harmonic mode of the driven radiating electrode 6 and the parasitic radiating electrode 7 is not affected by ON/OFF switching of the switching means 16. Thus, occurrence of the following problem can be avoided. For example, let it be supposed that a wireless communication system C performs wireless communication using a frequency band C shown in
The following describes a reason that the base resonant frequency of the driven radiating electrode 6 can be switched without changing the harmonic resonant frequency thereof by using the harmonic-mode zero-voltage region P of the driven radiating electrode 6 as a region of the driven radiating electrode 6 where a capacitance is loaded by the capacitance loading electrode 12. Since the harmonic-mode zero-voltage region P of the driven radiating electrode 6 has a voltage of zero or nearly zero in the harmonic mode, even when the switching means 16 becomes ON so that a capacitor is formed between the capacitance loading electrode 12 and the driven radiating electrode 6, in the harmonic mode of the driven radiating electrode 6, the state is equivalent to that in the case where the capacitance is not loaded to the driven radiating electrode 6. Thus, even when the switching means 16 is switched ON/OFF, the harmonic resonant frequency of the driven radiating electrode 6 does not change, so that change in the harmonic resonant frequency band of the driven radiating electrode 6 in the multiple resonance by the harmonic mode of the driven radiating electrode 6 and the parasitic radiating electrode 7 is suppressed. In contrast, in the base mode, the harmonic-mode zero-voltage region P of the driven radiating electrode 6 is a region where the voltage has such a degree that the region is affected by loading of a capacitance by the capacitance loading electrode 12. Thus, it is possible to switch the base resonant frequency of the driven radiating electrode 6 by ON/OFF of capacitance loading by the capacitance loading electrode 12.
That is, with a configuration that allows capacitance loading to the harmonic-mode zero-voltage region P of the driven radiating electrode 6 by the capacitance loading electrode 12 and with a configuration for switching ON/OFF of the capacitance loading by the capacitance loading electrode 12, advantageously, it is possible to switch the base resonant frequency band of the driven radiating electrode 6 without changing the harmonic resonant frequency band of the driven radiating electrode 6.
This has been confirmed through experiments by the inventors. In the experiments, a sample A having the configuration of the antenna structure 1 according to the first embodiment was prepared, and a sample B shown in
As represented in the measurement results shown in the graphs of
That is, through the experiments, it has been confirmed that, by loading a capacitance with the ground to the harmonic-mode zero-voltage region P of the driven radiating electrode 6 by the capacitance loading electrode 12, and switching the ON/OFF of capacitance loading to the harmonic-mode zero-voltage region P, it is possible to switch the base resonant frequency of the driven radiating electrode 6 without changing the harmonic resonant frequency band of the driven radiating electrode 6. That is, the experiments demonstrate that if a capacitance with the ground is loaded by the capacitance loading electrode 12 to a region other than the harmonic-mode zero-voltage region P of the driven radiating electrode 6, the harmonic resonant frequency band of the driven radiating electrode 6 changes when the ON/OFF of capacitance loading is switched.
Modifications
Although capacitance loading means is formed by the capacitance loading electrode 12 in the examples shown in
Furthermore, although the capacitance loading electrode 12 is formed so as to extend from an end edge on the bottom surface of the base 2 to a side surface of the base 2 in the examples shown in
Furthermore, although the capacitance loading electrode 12 is formed so as to extend from an end edge on the bottom surface of the base 2 to a side surface of the base 2 in the examples shown in
Furthermore, although capacitance loading means is formed by the capacitance loading electrode 12 in the examples shown in
With the capacitance loading means formed by the capacitance-loading capacitor component 23 as described above, the following advantages can be achieved. The width of change in the base resonant frequency of the driven radiating electrode 6 at the time of switching of the switching means 16 from OFF to ON corresponds to capacitance between the driven radiating electrode 6 and the ground, loaded by the capacitance loading means. Thus, by forming capacitance loading means by the capacitance-loading capacitor component 23, particularly by a variable-capacitance capacitor component that allows continuous changing of capacitance, it becomes readily possible to precisely adjust the width of change in the base resonant frequency of the driven radiating electrode 6 at the time of switching of the switching means 16 from OFF to ON to a predetermined width of change. Accordingly, the antenna structure 1 and a wireless communication apparatus having frequency characteristics more suitable for the needs can be readily provided.
Furthermore, in the case where capacitance loading means is formed by the capacitance loading electrode 12, the magnitude of capacitance that can be loaded to the driven radiating electrode 6 by the capacitance loading electrode 12 is restricted, for example, by restriction of size, formation region, or the like. In contrast, by forming capacitance loading means by the capacitance-loading capacitor component 23, compared with the case where capacitance loading means is formed by the capacitance loading electrode 12, it is possible to increase the capacitance with the ground electrode 4, loaded to the driven radiating electrode 6 by the capacitance loading means. Thus, it is possible to increase the variable range of the width of change in the base resonant frequency of the driven radiating electrode 6 at the time of switching of the switching means 16 from OFF to ON. This results in an advantage that it becomes more readily possible to meet the needs for various frequency bands. In the case where capacitance loading means is formed by the capacitance loading electrode 12, advantageously, since the capacitance-loading capacitor component 23 is not needed, it is possible to alleviate increase in the number of parts, and structural complexity can be avoided.
Now, a second embodiment will be described. In the description of the second embodiment, components that are the same as those in the first embodiment are designated by the same numerals, and repeated description of the common components will be omitted.
In the second embodiment, as shown in
Now, an example configuration of an antenna structure 1 including the antenna component shown in
Now, another example configuration of an antenna structure 1 including the antenna component shown in
In the example of the antenna structure 1 shown in
Although two capacitance loading electrodes 12 are formed in the examples shown in
In the second embodiment, a plurality of capacitance loading means is provided on the base 2, and at least one of the plurality of capacitance loading means is electrically connected to the ground electrode 4 by the grounding conduction path 15 via switching means 16. Thus, cost of the antenna structure 1 can be reduced by the following reason. Depending on difference among the types or models of wireless communication apparatuses in which the antenna structure 1 is included, the required width of change in the base resonant frequency of the driven radiating electrode 6 at the time of switching of capacitance loading from OFF to ON differs. Thus, a possible approach is to manufacture antenna components for individual types or models of wireless communication apparatuses, each of the antenna components including capacitance loading means provided on the base 2 together with the driven radiating electrode 6, the capacitance loading means serving to load a capacitance with the ground electrode 4 to the harmonic-mode zero-voltage region P of the driven radiating electrode 6 in order to achieve the required width of change. In this case, however, since antenna components must be manufactured for individual types or models of wireless communication apparatuses, a large number of types of wireless communication apparatuses is needed. In contrast, by providing in an antenna component a plurality of capacitance loading means for loading mutually different capacitances to the harmonic-mode zero-voltage region P of the driven radiating electrode 6, and connecting the capacitance loading means to the ground electrode 4 on the circuit board 3 by the grounding conduction path 15 via the switching means 16 in accordance with a predetermined width of change in the base resonant frequency of the driven radiating electrode 6 by switching of capacitance loading between OFF and ON, it is possible to provide the same type of antenna component in a plurality of types of wireless communication apparatuses. That is, use of common antenna components is allowed. Thus, cost of the antenna structure 1 and wireless communication apparatuses including the antenna structure 1 can be reduced.
Now, a third embodiment will be described. In the description of the third embodiment, components that are the same as those in the first and second embodiments are designated by the same numerals, and repeated description of the common components will be omitted.
In the third embodiment, in addition to the configuration of the first or second embodiment, the parasitic radiating electrode 7 has a loop-shaped current path. For example, in an example shown in
In the third embodiment, the parasitic radiating electrode 7 performs antenna operations in a plurality of resonant frequency bands different from each other. A base resonant frequency Fb7 in a base resonant frequency band, which has lowest frequencies among the plurality of resonant frequency bands of the parasitic radiating electrode 7, is chosen to be, for example, a frequency in the vicinity of the base resonant frequency Fb6 of the driven radiating electrode 6, and the antenna operation (base mode) in the base resonant frequency band of the parasitic radiating electrode 7 causes multiple resonance together with the base mode of the driven radiating electrode 6, for example, as indicated by a solid lie α in
Also in a case of such a configuration, in the third embodiment, similarly to the first and second embodiments, a configuration is provided that allows switching ON/OFF the capacitance loading by capacitance loading means (the capacitance loading electrode 12 in the example shown in
In the third embodiment, the parasitic radiating electrode 7 causes multiple resonance both in the base resonant frequency band and the harmonic resonant frequency band of the driven radiating electrode 6. Thus, as well as increasing the bandwidth of the base frequency band of the driven radiating electrode 6 through switching of the base resonant frequency of the driven radiating electrode 6, it is possible to increase the bandwidth of the base frequency band of the driven radiating electrode 6 by multiple resonance by the parasitic radiating electrode 7. Accordingly, it is possible to further increase the bandwidth of the base frequency band of the driven radiating electrode 6.
Furthermore, in the third embodiment, similarly to the driven radiating electrode 6, the parasitic radiating electrode 7 has a loop-shaped current path. Thus, similarly to the driven radiating electrode 6, it is possible to adjust the base resonant frequency and the harmonic resonant frequency of the parasitic radiating electrode 7 substantially independently of each other. Accordingly, it becomes readily possible to adjust the base resonant frequency and the harmonic resonant frequency of the parasitic radiating electrode 7 individually to predetermined frequencies. Furthermore, since the parasitic radiating electrode 7 also has a loop-shaped current path by forming the slit 26 in the electrode 7 similarly to the driven radiating electrode 6, advantageously, it is possible to increase the electrical length of the parasitic radiating electrode 7 without increasing the size thereof, and it is possible to increase the bandwidth of the frequency band.
In the example shown in
Now, a fourth embodiment will be described. In the description of the fourth embodiment, components that are the same as those in the first to third embodiments will be designated by the same numerals, and repeated description of the common components will be refrained.
In the fourth embodiment, in addition to the configuration of the third embodiment, capacitance loading means for loading a capacitance to a region of the parasitic radiating electrode 7 where the voltage becomes zero or nearly zero in the harmonic mode of the parasitic radiating electrode 7 (a harmonic-mode zero-voltage region) is provided. For example, in an example shown in
For example, when the switching means 16 is OFF, capacitance loading by the capacitance loading electrode 12 to the harmonic-mode zero voltage region P of the driven radiating electrode 6 is OFF. Furthermore, capacitance loading by the capacitance loading electrode 27 to the harmonic-mode zero-voltage region U of the parasitic radiating electrode 7 is OFF. In this case, for example, the base resonant frequency of the driven radiating electrode 6 is a frequency Fb6 shown in
Although the capacitance loading means on the side of the driven radiating electrode 6 is formed by the capacitance loading electrode 12 in the example shown in
Furthermore, although the capacitance loading electrodes 12 and 27 are electrically connected to the ground electrode 4 via the common switching means 16 and the grounding conduction path 15 in the example shown in
In the fourth embodiment, capacitance loading means (the capacitance loading electrode 27) is provided also for the parasitic radiating electrode 7 in order to load a capacitance to the harmonic-mode zero-voltage region thereof, similarly to the driven radiating electrode 6, it is possible to switch the base resonant frequency of the parasitic radiating electrode 7 without changing the harmonic resonant frequency of the parasitic radiating electrode 7. Thus, through switching of the base resonant frequencies of the driven radiating electrode 6 and the parasitic radiating electrode 7, it is possible to further increase the bandwidth of the base resonant frequency band.
A modification of the fourth embodiment is shown in
Now, a fifth embodiment will be described. In the description of the fifth embodiment, components that are the same as those in the first to fourth embodiments will be designated by the same numerals, and repeated description of the common components will be omitted.
In the antenna structure 1, in some cases, positions where capacitance loading means can be formed are restricted due to, for example, the layout of wires on the circuit board 3. In this case, there exists a risk that the positions where capacitance loading means can be formed do not match positions where a capacitance can be loaded by capacitance loading means to the harmonic-mode zero voltage region P of the driven radiating electrode 6. The fifth embodiment has a configuration in which such a situation can be avoided. More specifically, the fifth embodiment has a configuration described below in addition to the configuration of the first to fourth embodiments.
Since the driven radiating electrode 6 is formed on the base 2, the voltage distribution at the driven radiating electrode 6 is affected by the dielectric constant of the base 2. Thus, it is possible to adjust the area of the harmonic-mode zero voltage region P of the driven radiating electrode 6 by adjusting the dielectric constant of the base 2. Based on this fact, for example, the antenna structure 1 according to the fifth embodiment is designed as follows. For example, the position of forming capacitance loading means is determined on the basis of restrictions of position of forming capacitance loading means and so forth. A region of the driven radiating electrode 6 to which a capacitance is loaded by the capacitance loading means is determined as a position where the harmonic-mode zero voltage region P is to be provided. The dielectric constant of the base 2 is determined so that the harmonic-mode zero voltage region P of the driven radiating electrode 6 is provided at the determined position. The base 2 is formed of a dielectric material having the determined dielectric constant.
For example, in the examples of the antenna structure 1 in the figures used to describe the first to fourth embodiments, the capacitance loading electrode 12 is formed at a corner of the base 2. However, by adjusting the dielectric constant of the base 2 as described above, for example, as shown in
Although the entirety of the base 2 is formed of the same dielectric material in the example described above, the voltage distribution in the harmonic mode of the driven radiating electrode 6 is susceptible to the effect of the dielectric constant in a region where the open end of the driven radiating electrode 6 is formed. Thus, for example, it is possible to use a dielectric material having a dielectric constant for providing the harmonic-mode zero voltage region P of the driven radiating electrode 6 at the determined position to form only a base portion where the open end of the driven radiating electrode 6 is formed. Furthermore, for example, as shown in
Although the capacitance loading electrode 12 is provided as capacitance loading means on the side of the driven radiating electrode 6 in the examples shown in
In the fifth embodiment, as described above, the dielectric constant of the base 2 is adjusted entirely or partially, or a dielectric member is provided on a region where the open end of the driven radiating electrode 6 or the parasitic radiating electrode 7 is formed, thereby adjusting the position where the harmonic-mode zero voltage region P of the driven radiating electrode 6 or the harmonic-mode zero-voltage region U of the parasitic radiating electrode 7 is provided. Thus, even in a case where the position of forming capacitance loading means for the driven radiating electrode 6 or the parasitic radiating electrode 7 is restricted, it is possible to load a capacitance to the harmonic-mode zero voltage region P of the driven radiating electrode 6 or the harmonic-mode zero-voltage region U of the parasitic radiating electrode 7 by the capacitance loading means. Thus, it is possible to perform switching of the base resonant frequency bands of the driven radiating electrode 6 and the parasitic radiating electrode 7.
Now, a sixth embodiment will be described. In the description of the sixth embodiment, components that are the same as those in the first to fifth embodiments will be designated by the same numerals, and repeated description of the common components will be omitted.
Depending on the specification of a wireless communication apparatus in which the antenna structure 1 is included, the base resonant frequency band of the driven radiating electrode 6 satisfies conditions of a predetermined frequency band without switching the base resonant frequency of the driven radiating electrode 6. In such a case, since it is not needed to switch the base resonant frequency of the driven radiating electrode 6, it is possible to construct an antenna structure 1 including an antenna component according to one of the first to fifth embodiments and not including the switching means 16. Thus, an antenna structure 1 according to the sixth embodiment is configured as follows.
In the sixth embodiment, as shown in
Furthermore, when the antenna structure 1 is required to support wireless communication in four frequency bands A, C, D, and E shown in
In the configuration of the antenna structure according to the sixth embodiment, since the switching means 16 can be omitted, it is possible to simplify the antenna structure. Instead of the capacitance loading electrode 12 shown in
In the sixth embodiment, option capacitance loading means is provided on the base 2. Thus, use of a common antenna component is allowed. That is, an antenna component in which option capacitance loading means is formed on the base 2 can be provided in an antenna structure 1 in which it is needed to load a capacitance with the ground electrode 4 to the harmonic-mode zero-voltage region P or U of the driven radiating electrode 6 or the parasitic radiating electrode 7, and also in an antenna structure 1 in which switching of the ON/OFF of capacitance loading is needed. Thus, use of a common antenna component is allowed, so that it is possible to reduce cost of the antenna structure 1.
Now, a seventh embodiment will be described. The seventh embodiment relates to a wireless communication apparatus. In the wireless communication apparatus according to the seventh embodiment, the antenna structure 1 according to one of the first to sixth embodiments is provided. The wireless communication apparatus except for the antenna structure can be configured in various manners, and the configuration of the wireless communication apparatus except for the antenna structure is not particularly limited and is determined as appropriate.
The present invention is not limited to the first to seventh embodiments, and various modified embodiments are possible. For example, although the driven radiating electrode 6 has such a form that the current path has a loop shape with the slit 8 in the first to seventh embodiments, for example, a driven radiating electrode 6 having a loop current path may be provided using strip electrodes. This also applies to a case where the parasitic radiating electrode 7 has a loop-shaped current path.
Furthermore, although the driven radiating electrode 6 has only one slit in the first to seventh embodiments, for example, a plurality of slits may be provided side by side, with the current path of the driven radiating electrode 6 having a loop shape extending around the slits to connect the feeding end Q and the open end K, and the number of slits formed is not limited. Furthermore, the shape of the slits is not limited. This also applies when slits are formed on the parasitic radiating electrode 7.
Furthermore, although the base 2 has a rectangular parallelepiped shape in the first to seventh embodiments, the base 2 may have shapes other than a rectangular parallelepiped shape, such as a cylindrical shape or a polygonal shape.
Furthermore, although one driven radiating electrode 6 and one parasitic radiating electrode 7 are provided on the base 2, a plural number of at least one of the driven radiating electrode 6 and the parasitic radiating electrode 7 may be provided on the base 2.
The present invention is suitable, for example, for an antenna structure that is compatible with a plurality of wireless communication systems having mutually different operating frequency bands and to a wireless communication apparatus.
Although particular embodiments have been described, many other variations and modifications and other uses will become apparent to those skilled in the art. Therefore, the present invention is not limited by the specific disclosure herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-036830 | Feb 2006 | JP | national |
This is a continuation under 35 U.S.C. §111(a) of PCT/JP2006/323818 filed Nov. 29, 2006, and claims priority of JP2006-036830 filed Feb. 14, 2006, both incorporated by reference.
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| Number | Date | Country | |
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| 20090015497 A1 | Jan 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2006/323818 | Nov 2006 | US |
| Child | 12188550 | US |
