WO2007075036A1

WO2007075036A1 - Rf antenna using dielectric resonator

Info

Publication number: WO2007075036A1
Application number: PCT/KR2006/005745
Authority: WO
Inventors: Sang-Eun Jung; Jong-Woon Hong
Original assignee: Sang-Eun Jung; Jong-Woon Hong
Priority date: 2005-12-29
Filing date: 2006-12-27
Publication date: 2007-07-05

Abstract

An RF antenna using a dielectric resonator is disclosed. The RF antenna includes a dielectric resonator for resonating a signal of a predetermined frequency band, and a resonance frequency shift circuit, coupled to the dielectric resonator, for shifting the frequency resonating in the dielectric resonator. The dielectric resonator has the resonance characteristic in a frequency band higher than a frequency band intended to be received, and the resonance frequency shift circuit changes the resonance characteristic of the dielectric resonator so that the dielectric resonator resonates in a frequency band lower than the predetermined frequency band.

Description

RF ANTENNA USING DIELECTRIC RESONATOR

Technical Field

The present invention relates to an antenna receiving an RF signal, and more particularly to an antenna that is used in a portable terminal or a miniature device using a dielectric resonator.

Background Art With the development of wireless communication technology, the use of wireless communication devices has been abruptly increased. Recently, a mobile phone use rate is much higher than a wire phone use rate, and due to the introduction of wireless LAN and DMB technologies in addition to mobile phones, diverse wireless communication devices have been produced.

Such wireless communication devices are all provided with antennas to receive RF signals. Diverse types of antennas have been proposed in accordance with frequency bands used by the corresponding devices, and the sizes of antennas differ depending on the frequency bands used by the respective wireless communication devices.

Although most wireless communication devices are required to be portable or to be miniaturized, the size of the antenna for receiving the RF signal is one of important factors to disturb the miniaturization of the portable terminal or the wireless communication device. In particular, in the case where the used frequency band is relatively low in comparison to other communication frequencies, the size of the antenna becomes a serious obstacle to the miniaturization of the devices such as a portable phone, a DMB receiver, a wireless LAN communication device, and so forth.

FIG. 1 is a view illustrating an antenna provided in a general portable terminal .

As shown in FIG. 1, the antenna used in the portable terminal is a dipole antenna that is extended up and down. In order to watch a broadcast, a user should pull out the antenna, and this causes the user great inconvenience in use. The length of the antenna is in proportion to the wavelength of the frequency received through the antenna, and typically, the length of the antenna is determined by λ/4, where λ denotes the wavelength of the received frequency. Particularly, in the case of using a low frequency of 170MHz that is a ground-wave DMB frequency band, the length of the antenna normally becomes 30cm, and this length of the antenna cannot but become a serious obstacle to the miniaturization of the antenna.

Disclosure Technical Problem Therefore, the present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a miniature antenna that can be used in a low frequency band.

It is another object of the present invention to provide a miniature RF receiving antenna using a dielectric resonator, which is smaller than the existing antennas even in a relatively low frequency band.

It is still another object of the present invention to provide a miniature RF receiving antenna using a coil, a dielectric resonator, and an amplifier, which is miniaturized in a low frequency band. It is still another object of the present invention to provide an RF receiving antenna built in a wire communication device, which is miniaturized and has an improved receiving sensitivity as well .

Technical solution

In order to achieve the above objects, in one aspect of the present invention, there is provided an RF antenna using a dielectric resonator, which includes the dielectric resonator for resonating a signal of a predetermined frequency band; and a resonance frequency shift circuit, coupled to the dielectric resonator, for shifting the frequency resonating in the dielectric resonator; wherein the dielectric resonator has the resonance characteristic in a frequency band higher than a frequency band intended to be received, and the resonance frequency shift circuit changes the resonance characteristic of the dielectric resonator so that the dielectric resonator resonates in a frequency band lower than the predetermined frequency band.

The resonance frequency shift circuit may be connected to the dielectric resonator in parallel or in series. The RF antenna using a dielectric resonator may be coupled to an internal circuit that performs a predetermined signal process with respect to an output signal of the antenna .

The resonance frequency shift circuit may be composed of a combination of at least one inductor and at least one capacitor.

The resonance frequency shift circuit may shift the resonance frequency of the dielectric resonator by using the combination of the inductor and the capacitor connected in parallel.

The resonance frequency shift circuit may include a first inductor connected to one end part of the dielectric resonator, a second inductor connected to the first inductor, a first capacitor connected in parallel to the second inductor, and a second capacitor connected in series to the other end part of the dielectric resonator.

The resonance frequency shift circuit may include a first inductor connected in series to the dielectric resonator, a second inductor connected in series to the first inductor, a first capacitor connected in parallel to the second inductor, and a second capacitor connected in series to the second inductor. The resonance frequency shift circuit may be formed on a PCB, and the PCB on which the resonance frequency shift circuit is formed may be coupled to the dielectric resonator.

In another aspect of the present invention, there is provided an RF antenna using a dielectric resonator, which includes the dielectric resonator for resonating a signal of a predetermined frequency band; and a resonance frequency shift circuit, coupled to the dielectric resonator, for shifting the frequency resonating in the dielectric resonator; wherein the resonance frequency shift circuit is formed on a PCB, the PCB is coupled to the dielectric resonator, and the resonance frequency shift circuit is composed of a combination of at least one inductor and at least one capacitor. In still another aspect of the present invention, there is provided an active RF antenna using a dielectric resonator, which includes the dielectric resonator for resonating a signal of a predetermined frequency band; and a resonance frequency shift circuit, coupled to the dielectric resonator, for shifting the resonance frequency band of the dielectric resonator; wherein the resonance frequency shift circuit is composed of a coil having a core of which a shift range of the resonance frequency band is determined according to a user's manipulation. The dielectric resonator and the resonance frequency shift circuit may be formed on a PCB.

The active RF antenna using the dielectric resonator may further include a ground surface, formed on the same surface of the dielectric resonator and the PCB on which the resonance frequency shift circuit is formed, for facilitating the forming of an electric field. The active RF antenna using the dielectric resonator may further include an amplifying circuit, formed on the PCB, for amplifying a signal received through the dielectric resonator to output the amplified signal.

The dielectric resonator, the resonance frequency shift circuit, the amplifying circuit, and the ground surface may be formed in a body on the PCB.

Advantageous Effects

The RF receiving antenna using the dielectric resonator as constructed above according to the present invention is much smaller than the existing antenna, and it can be used even in the low frequency band. Accordingly, the RF receiving antenna according to the present invention can greatly contribute to the miniaturization of diverse kinds of portable devices such a portable phone, a ground-wave DMB receiver, and so forth. Also, the miniature antenna according to the present invention has a good receiving sensitivity in comparison to the conventional dipole antenna.

Description of Drawings

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a view illustrating an antenna provided in a general portable terminal; FIG. 2 is a block diagram illustrating the construction of an RF receiving antenna according to an embodiment of the present invention;

FIG. 3 is a circuit diagram illustrating the construction of a resonance frequency shift circuit according to an embodiment of the present invention;

FIG. 4 is a circuit diagram illustrating the construction of a resonance frequency shift circuit according to another embodiment of the present invention;

FIG. 5 is a view illustrating the structure of a dielectric resonator coupled to a PCB on which a resonance frequency shift circuit as illustrated in FIG. 4 is formed;

FIG. 6 is a circuit diagram illustrating the construction of a resonance frequency shift circuit according to still another embodiment of the present invention; FIG. 7 is a circuit diagram illustrating the construction of a resonance frequency shift circuit according to still another embodiment of the present invention;

FIG. 8 is a view illustrating the structure of a dielectric resonator coupled to a PCB on which a resonance frequency shift circuit as illustrated in FIG. 7 is formed;

FIG. 9 is a graph showing an output waveform of a dielectric resonator when the resonance frequency shift circuit is not coupled to the dielectric resonator, and an output waveform of the dielectric resonator when the resonance frequency shift circuit is coupled to the dielectric resonator; FIG. 10 is a view illustrating the shape of a dielectric resonator according to an embodiment of the present invention;

FIG. 11 is a view illustrating the results of measuring the sensitivity of an antenna in specified channels of a CDMA frequency band according to an embodiment of the present invention;

FIG. 12 is a view illustrating the results of measuring the radiation power of an antenna according to an embodiment of the present invention; FIG. 13 is a view illustrating the results of measuring the sensitivity of a general portable phone antenna in the channels of the CDMA frequency band as illustrated in FIG.

11;

FIG. 14 is a view illustrating the results of measuring the radiation power of a general portable phone antenna in the channels of the CDMA frequency band as illustrated in FIG. 12;

FIG. 15 is a graph showing the results of measuring the sensitivity as illustrated in FIG. 11; FIG. 16 is a graph showing the results of measuring the radiation power as illustrated in FIG. 12;

FIG. 17 is a graph showing the results of measuring the sensitivity as illustrated in FIG. 13;

FIG. 18 is a graph showing the results of measuring the radiation power as illustrated in FIG. 14;

FIG. 19 is a block diagram illustrating the construction of an RF receiving antenna according to another embodiment of the present invention;

FIG. 20 is a block diagram illustrating the construction of a miniature RF antenna using a core coil, a dielectric resonator, and an amplifier according to still another embodiment of the present invention;

FIG. 21 is a view illustrating the coil and the dielectric resonator of FIG. 19, coupled to a PCB; and

FIG. 22 is a view illustrating the amplifying circuit of FIG. 19, coupled to a PCB.

Best Mode

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The matters defined in the description, such as the detailed construction and elements, are nothing but specific details provided to assist those of ordinary skill in the art in a comprehensive understanding of the invention, and thus the present invention is not limited thereto. FIG. 2 is a block diagram illustrating the construction of an RF receiving antenna according to an embodiment of the present invention. Referring to FIG. 2, the RF antenna using a dielectric resonator according to an embodiment of the present invention includes the dielectric resonator 200 and a resonance frequency shift circuit 202. In the embodiment of the present invention, the RF receiving antenna receives an RF signal using the dielectric resonator, without employing an antenna radiating element such as a dipole.

The dielectric resonator 200 functions to resonate the received RF signal at a specified frequency. The resonance frequency of the dielectric resonator 200 is determined by the shape and size of the dielectric resonator. The shape of the dielectric resonator is divided into a hexahedron and a disk. Also, the size of the dielectric resonator differs depending on the resonance frequency.

In the embodiment of the present invention, the dielectric resonator used in the antenna resonates at a frequency higher than a frequency band intended to be received.

The size of the dielectric resonator is in inverse proportion to the frequency, in the same manner as the antenna.

For example, the size of a dielectric resonator having a resonance frequency band of 1.8GHz is smaller than the size of a dielectric resonator having a resonance frequency band of 900MHz. In order to minimize the size of the dielectric resonator used, it is required to use the dielectric resonator having the resonance frequency higher than the frequency intended to be received through the antenna

For example, a hexahedral dielectric resonator resonating in the frequency band of 1.8GHz has dimensions of about 3 (W) x3 (L) x6 (H) mm, and a hexahedral dielectric resonator resonating in the frequency band of 900MHz has dimensions of about 6 (W) x6 (L) x8 (H) mm. In the present invention, when an RF signal in the frequency band of 900MHz is received, a dielectric resonator resonating in the frequency band of 1.8GHz, the size of which is smaller than that of a dielectric resonator in the frequency band of 900MHz, is used.

FIG. 10 is a view illustrating the shape of a dielectric resonator according to an embodiment of the present invention. As shown in FIG. 10, the dielectric resonator may be hexahedral, and have a structure of which both side surfaces 1000 and 1002 are opened. In order to transfer a signal resonating in the dielectric resonator, strip lines may be coupled to other side surfaces of the dielectric resonator, which are not opened.

In order to transfer the signal resonating in the dielectric resonator, cables for transferring the signal may be installed on the opened side surfaces 1000 and 1002 of the dielectric resonator, unlike the structure of FIG. 10. A dielectric resonator 200 is coupled to a resonance frequency shift circuit 202. The resonance frequency shift circuit 202 serves to shift the resonance frequency of the dielectric resonator coupled thereto. For example, although the dielectric resonator 200 is a resonator resonating at the frequency band of 1.8GHz, the resonance frequency shift circuit 202 shifts the resonance frequency of the dielectric resonator to the frequency band of 900MHz. The resonance frequency shift circuit 202 is the core element of the present invention, and enables the high-frequency dielectric resonator having a small size to receive a low- frequency signal . FIG. 2 illustrates a resonance frequency shift circuit coupled in series to a dielectric resonator. However, it will be apparent to skilled in the art that they may be coupled in parallel to each other.

In the embodiment of the present invention, the resonance frequency shift circuit includes an inductor element and a capacitor element. The resonance frequency shift circuit can shift the resonance frequency of the high- frequency dielectric resonator to the low-frequency band, using the inductor element and the capacitor element . In the embodiment of the present invention, the resonance frequency shift circuit including the inductor element and the capacitor element is formed on a PCB board, and the PCB board on which the resonance frequency shift circuit is formed is coupled to the dielectric resonator to implement the antenna according to the present invention. Of course, the present invention is not limited to the resonance frequency shift circuit formed on the PCB board, but it will be apparent that the resonance frequency shift circuit may be provided in diverse forms. The construction of the resonance frequency shift circuit will be explained in detail with reference to the accompanying drawings. FIG. 3 is a circuit diagram illustrating the construction of a resonance frequency shift circuit according to an embodiment of the present invention.

Referring to FIG. 3, the resonance frequency shift circuit according to an embodiment of the present invention may be coupled in parallel to both end parts of the dielectric resonator, and includes an inductor Ll and a capacitor Cl. The resonance frequency shift circuit shifts the resonance frequency of the dielectric resonator, corresponding to the inductance values of the inductor Ll and the capacitor Cl. The capacitor and the inductor change the frequency resonating through the dielectric resonator in accordance with the available frequency determination characteristic of the inductor and the capacitor.

For example, in order to shift the resonance frequency of the dielectric resonator having the resonance frequency band of 1.8GHz to 900MHz, the capacitance value of the capacitor Cl may be 12OpF, and the inductance value of the inductor Ll may be 33μH.

FIG. 4 is a circuit diagram illustrating the construction of a resonance frequency shift circuit according to another embodiment of the present invention.

Referring to FIG. 4, the resonance frequency shift circuit according to another embodiment of the present invention may include a first inductor Ll connected to a first end part of the dielectric resonator, a second inductor L2 connected to a second end part of the dielectric resonator, a first capacitor Cl connected in parallel to the second inductor, and a second capacitor C2 connected between the second inductor L2 and ground.

Here, an output signal of which the resonance frequency has been converted is applied to the second inductor L2 and the first capacitor Cl, and the signal applied to the second inductor is transferred to an internal circuit connected to the antenna. The internal circuit receives an RF signal from the antenna composed of the dielectric resonator and the resonance frequency shift circuit according to the present invention, and performs general signal processes such as signal conversion and frequency modulation/demodulation.

As shown in FIGS . 3 and 4 , the resonance frequency shift circuit includes one or two inductors and capacitors. However, it will be apparent to skilled in the art that the number of inductors and capacitors may differ as needed.

FIG. 5 is a view illustrating the structure of a dielectric resonator coupled to a PCB on which a resonance frequency shift circuit as illustrated in FIG. 4 is formed. In FIG. 5, PCB pattern on which the circuit as illustrated in FIG. 4 is formed and a dielectric resonator 500 coupled thereto are illustrated.

In FIG. 5, a first inductor Ll and a second inductor L2 may be formed in the form of a general PCB pattern. Unlike this, chip inductors may be used as the first inductor Ll and the second inductor L2.

Also, the chip capacitors may be coupled to the PCB pattern as the first capacitor Cl and the second capacitor C2.

In FIG. 5, the first capacitor Cl is formed between both end parts of a second inductor pattern so as to be connected in parallel to the second inductor L2. One end part of the second capacitor L2 is connected in series to a part in which the first inductor pattern is formed, and the other end part thereof is connected to ground.

A pad 504 for coupling the dielectric resonator to an upper part of the PCB is provided on both end parts of the dielectric resonator, and the dielectric resonator is fixed to the PCB by the pad. The PCB as illustrated in FIG. 5 may be 5 (W) x9 (L) in size.

In FIG. 5, the PCB pattern on which strip lines are coupled to both side surfaces of the dielectric resonator is illustrated. However, the dielectric resonator may be coupled to the resonance frequency shift circuit as a cable is connected to an open part of the dielectric resonator.

FIG. 6 is a circuit diagram illustrating the construction of a resonance frequency shift circuit according to still another embodiment of the present invention.

Referring to FIG. 6, the resonance frequency shift circuit may be coupled in series to one end part of the dielectric resonator, and includes an inductor Ll and a capacitor Cl. As shown in FIG. 6, the inductor Ll and the capacitor Cl are connected in parallel to each other, and the resonance frequency shift circuit shifts the resonance frequency of the dielectric resonator, corresponding to the inductance and capacitance values of the inductor Ll and the capacitor Cl.

FIG. 3 illustrates a resonance frequency shift circuit composed of an inductor and a capacitor and coupled in parallel to the dielectric resonator according to an embodiment of the present invention. Even in the case where the resonance frequency shift circuit composed of an inductor and a capacitor is connected in series to the dielectric resonator, it can serve as the resonance frequency shift circuit. In this case, the capacitance and inductance values of the capacitor Cl and the inductor Ll are basically the same as those connected in parallel to each other. However, their values may differ due to the change of the PCB pattern.

FIG. 7 is a circuit diagram illustrating the construction of a resonance frequency shift circuit according to still another embodiment of the present invention.

Referring to FIG. 7, the resonance frequency shift circuit according to still another embodiment of the present invention may include a first inductor Ll connected to one end part of the dielectric resonator, a second inductor L2 connected in series to the first inductor Ll, a first capacitor Cl connected in parallel to the second inductor, and a second capacitor C2 connected in series to the second inductor.

FIG. 7 illustrates the construction in which the resonance frequency shift circuit is connected in series to the dielectric resonator. As illustrated in FIG. 7, the resonance frequency shift circuit is connected to one end part of the dielectric resonator only.

The capacitors and the inductors constituting the dielectric resonance circuit of FIG. 7 also shift the resonance frequency of the dielectric resonator, corresponding to their capacitance and inductance values.

The output signal of the resonance frequency shift circuit of FIG. 7 is applied to both ends of the second inductor L2 , and is transferred to an internal circuit. The internal circuit receives an RF signal from the antenna composed of the dielectric resonator and the resonance frequency shift circuit according to the present invention, and performs general signal processes such as signal conversion and frequency modulation/demodulation. FIG. 8 is a view illustrating the structure of a dielectric resonator coupled to a PCB on which a resonance frequency shift circuit as illustrated in FIG. 7 is formed.

In FIG. 8, PCB pattern on which the circuit as illustrated in FIG. 7 is formed and a dielectric resonator 800 coupled thereto are illustrated.

In FIG. 8, a first inductor Ll and a second inductor L2 may be formed in the form of a general PCB pattern. Of course, the first inductor Ll and the second inductor L2 maybe implemented in the form of a chip inductor. Also, typical chip capacitors may be used as the first capacitor Cl and the second capacitor C2 , and are coupled to parts of the PCB pattern.

In FIG. 8, the first capacitor Cl is formed between both end parts of a second inductor pattern so as to be connected in parallel to the second inductor L2. One end part of the second capacitor L2 is connected in series to a part in which the second inductor pattern is formed.

A pad 804 for coupling the dielectric resonator to an upper part of the PCB is provided on the dielectric resonator, and the dielectric resonator is fixed to the PCB by the pad. In FIG. 8, the PCB pattern on which a strip line is coupled to one side surface of the dielectric resonator is illustrated. However, as described above, the dielectric resonator may be coupled to the resonance frequency shift circuit as a cable is connected to an open part of the dielectric resonator.

FIG. 9 is a graph showing an output waveform of a dielectric resonator when the resonance frequency shift circuit is not coupled to the dielectric resonator, and an output waveform of the dielectric resonator when the resonance frequency shift circuit is coupled to the dielectric resonator.

In the case where the dielectric resonator of the frequency band of 1.8GHz is used as the antenna, the output waveform of the dielectric resonator has a peak value in the frequency band of 1.8GHz as shown in FIG. 9. However, in the case where the resonance frequency shift circuit as shown in FIGS. 3 through 8 is coupled to the dielectric resonator, the output waveform of the dielectric resonator has a peak value in the frequency band of 900MHz that is lower than the frequency band of 1.8GHz .

Using this principle, a relatively small antenna can be used in not only a CDMA portable phone that mainly uses the frequency band of 900MHz but also a ground-wave DMB receiver that mainly uses the frequency band of 200MHz. For example, by coupling the dielectric resonator resonating in the frequency band of 900MHz to the resonance frequency shift circuit, the antenna can be constructed to receive the ground-wave DMB signal in the frequency band of 200MHz.

Hereinafter, the result of testing the RF signal receiving performance of the dielectric resonator according to an embodiment of the present invention will be described. In order to test the receiving performance of the dielectric resonator according to the preferred embodiment of the present invention, the test was made on the case of receiving the frequency band of 900MHz. The frequency band of 900MHz is the frequency band for a CDMA portable phone, and the performance of the antenna according to the present invention was compared with the receiving performance of a general portable phone antenna. An antenna used in the test according to the preferred embodiment of the present invention was in the form of a hexahedron. In the test, the resonance frequency shift circuit as shown in FIG. 3 was used, the capacitance value of the capacitor was 12OpF, and the inductance value of the inductor Ll was 33μH.

A general portable phone antenna compared with the antenna according to the preferred embodiment of the present invention was a general dipole antenna having the diameter of 4mm and the length of 30mm.

In order to test the receiving performance of the antenna, two indexes were tested. One was a total isotropic sensitivity (TIS) , and the other was a total radiation power (TRP) . When measuring the TIS, the receiving performance of the equipment was measured using a bit error rate or a frame deletion rate. According to the feature of the TIS test, a proper digital error rate was used for the estimation of an effective radiation receiving sensitivity in respective spatial measurement positions. The receiving performance of the equipment was characterized in three dimensions by analyzing measurement data obtained through movement in space, and the receiving sensitivity of the equipment was estimated using data obtained by changing by 30° in theta and pi-axis directions. By integrating all sensitivity values, a total isotropic sensitivity was calculated.

FIG. 11 is a view illustrating the results of measuring the sensitivity of an antenna in specified channels of a CDMA frequency band according to the preferred embodiment of the present invention. As shown in FIG. 11, the sensitivity was measured at intervals of 30°. The total isotropic sensitivity obtained by integrating all the sensitivities was measured as 94.99dBm, and the measurement results in other two channels were 94.59dBm and 93.24dBm.

FIG. 15 is a graph showing the results of measuring the sensitivity as illustrated in FIG. 11.

FIG. 13 is a view illustrating the results of measuring the sensitivity of a general portable phone antenna in the channels of the CDMA frequency band as illustrated in FIG.

11. In the same manner as the measurement in FIG. 11, the sensitivity was measured at intervals of 30°.

The total isotropic sensitivity obtained by integrating all the sensitivities shown in FIG. 13 was measured as 9β.84dBm. With respect to a general portable phone antenna, the total isotropic sensitivity was also measured, and the measurement results in other two channels were 97.73dBm and 96.55dBm.

FIG. 17 is a graph showing the results of measuring the sensitivity as illustrated in FIG. 13.

In comparison to the general portable phone antenna, the antenna according to the preferred embodiment of the present invention has the total isotropic sensitivity that is slightly lower than that of the general portable phone antenna, and thus there is no great difference in total isotropic sensitivity between them.

In order to estimate the RF radiation performance of the device, the total radiation power (TRP) was measured by sampling the radiation transmission power in diverse positions surrounding the device. Theta and pi were changed at intervals of 30° in an axis direction, and the radiation power was estimated using data obtained as above. The total radiation power was measured by integrating all the measured power values.

FIG. 12 is a view illustrating the results of measuring the radiation power of an antenna according to the preferred embodiment of the present invention. As shown in FIG. 12, the radiation power was measured at intervals of 30° in an axis direction.

The total radiation power obtained by integrating all the radiation powers was measured as 17.83dBm, and the results of measuring the total radiation power in other two channels were 18.07dBm and 17.72dBm. FIG. 16 is a graph showing the results of measuring the radiation power as illustrated in FIG. 12.

FIG. 14 is a view illustrating the results of measuring the radiation power of a general portable phone antenna in the channels of the CDMA frequency band as illustrated in FIG. 12. In the same manner as the measurement in FIG. 12, the radiation power was measured at intervals of 30°.

The total radiation power obtained by integrating all the radiation powers shown in FIG. 14 was measured as 17.1IdBm. With respect to a general portable phone antenna, the total radiation power was also measured, and the measurement results in other two channels were 18.08dBm and 17.22dBm.

FIG. 18 is a graph showing the results of measuring the radiation power as illustrated in FIG. 14.

In comparison to the general portable phone antenna, the antenna according to the preferred embodiment of the present invention has the total radiation power that is slightly higher than that of the general portable phone antenna, and thus there is no great difference in total radiation power between them.

Hereinafter, an active RF antenna using a dielectric resonator according to the preferred embodiment of the present invention will be described in detail with reference to FIGS. 19 to 22.

FIG. 19 is a block diagram illustrating the construction of an RF receiving antenna according to another embodiment of the present invention, and FIG. 20 is a block diagram illustrating the construction of a miniature RF antenna using a core coil, a dielectric resonator, and an amplifier according to still another embodiment of the present invention. Referring to FIGS 19 and 20, the RF antenna using a dielectric resonator according to another embodiment of the present invention includes a signal receiving end 1100, an amplifying circuit 1200, and a PCB 1300.

The signal receiving end 1100 according to the present invention may comprise a dielectric resonator 1110 and a resonance frequency shift circuit 1120. The dielectric resonator 1110 serves to resonate the received RF signal at a specified frequency. The resonance frequency in the dielectric resonator 1110 is determined by the shape and size of the dielectric resonator 1110. In the embodiment of the present invention, the dielectric resonator 1110 used in the antenna according to the present invention resonates at a frequency higher than the frequency intended to be received through the antenna. In the same manner as the antenna, the size of the dielectric resonator is in inverse proportion to the frequency. For example, the size of the dielectric resonator 1110 having the resonance frequency band of 900MHz is smaller than the size of the dielectric resonator having the resonance frequency band of 200MHz. In order to minimize the size of the dielectric resonator 1110, it is required to use the dielectric resonator 1110 having the resonance frequency higher than the frequency intended to be received through the antenna .

The present invention can be used to receive a DMB signal or an FM signal having a frequency band that is relatively lower than other communication signals. In the embodiment of the present invention, the dielectric resonator 1110 having the frequency band of 900MHz is used to receive the DMB signal having the frequency band of 200MHz.

The dielectric resonator 1110 is generally hexahedral , and has dimensions of about 3 (W) x3 (L) x7 (H) mm. The size of the dielectric resonator 1110 having the frequency band of 900MHz is smaller than the size of the dielectric resonator 1110 having the frequency band of 200MHz, and is remarkably reduced in comparison to the dipole antenna that receives the typical frequency band of 200MHz.

The dielectric resonator 1110 is coupled to the resonance frequency shift circuit 1120. The resonance frequency shift circuit 1120 serves to shift the resonance frequency of the dielectric resonator 1110 coupled in series or parallel to the resonance frequency shift circuit. For example, although the dielectric resonator 1110 itself is the resonator having the shape and size for resonating at 900MHz, the resonance frequency of the dielectric resonator 1110 can be shifted to the frequency band of 200MHz using the resonance frequency shift circuit 1120.

The resonance frequency shift circuit 1120 is composed of a combination of a coil (i.e., inductor component) having at least one core and at least one capacitor.

The capacitor and/or the inductor (i.e., coil) constituting the resonance frequency shift circuit 1120 shift the resonance frequency of the dielectric resonator corresponding to their capacitance and/or inductance values. Typically, the capacitor and/or the inductor serve to determine the characteristic frequency value of a circuit such as a filter, and change the frequency resonating through the dielectric resonator in accordance with the available frequency determination characteristic of the inductor and the capacitor. The resonance frequency shift circuit 1120 is the core element of the present invention, and enables the high- frequency dielectric resonator 1110 having a small size to receive a low-frequency signal. In one embodiment of the present invention, the resonance frequency shift circuit 1120 is formed on a PCB board 1300, and this PCB board 1300 on which the resonance frequency shift circuit is formed is coupled to the dielectric resonator to provide an antenna according to the present invention. Of course, the present invention is not limited to the resonance frequency shift circuit formed on the PCB board, but it will be apparent to those skilled in the art that the resonance frequency shift circuit may be provided in diverse forms.

Preferably, the resonance frequency shift circuit 1120 according to the present invention may be constructed using a coil having a core. In an electric circuit, a coil is an element for realizing inductance that is one of basic constants, and a coil having a core used in the present invention means a coil wound round a core unit, which may go into or come out from the coil . In accordance with upward and downward movement of the core, the inductance value of the coil is changed, and thus a user can set a desired resonance point of the dielectric resonator 1110 by adjusting the core positioned in the coil.

On the other hand, the antenna according to the present invention may include the signal receiving end 1100 constructed using the dielectric resonator 1110 and the coil 1120 having the core provided therein, and the amplifying circuit 1200 for amplifying a signal received through the signal receiving end 1100.

That is, the amplifying circuit 1200 receives an RF signal from the signal receiving end 1100 that is composed of the dielectric resonator 1110 and the resonance frequency shift circuit 1120, and performs general signal processes such as signal conversion, frequency modulation/demodulation, and signal amplification.

Radio waves may differ in reaching distance and strength depending on their surrounding environments. If a radio wave is received in an area where the wave propagation environment is inferior, the strength of the received radio wave becomes weak, and thus the signal process thereof is impossible in an electronic appliance. To overcome this, the amplifying circuit 1200 amplifies the received signal and transfers the amplified signal to the signal processing unit of the electronic appliance.

The amplifying circuit 1200 is composed of a surface mount type coil, a resistor, a capacitor, and an FET for amplifying the received signal, and the inductance value of the coil and the FET may be changed in accordance with the frequency of the received signal. That is, the inductance value of the coil is changed according to the frequency of the received signal in such a manner that the inductance value becomes high if the received frequency is low, while the inductance value becomes low if the received frequency is high.

For example, in the case of amplifying the frequency band of 200MHz, a coil having an inductance value of 100~120nH is used, while in the case of amplifying the frequency band of 900MHz, a coil having the inductance value of 10~15nH is used. In this case, it is required to use an FET that matches the frequency band to be amplified.

FIG. 21 is a view illustrating the circuit coupled to the PCB in FIG. 20, and FIG. 22 is a view illustrating the construction of the whole antenna according to an embodiment of the present invention.

Referring to FIGS. 21 and 22, in an active RF antenna using a dielectric resonator according to an embodiment of the present invention, a signal receiving surface 1400 and a ground surface 1500 are arranged on the same surface of the PCB board 1300 on which the dielectric resonator 1110 and the resonance frequency shift circuit 1120 is formed to facilitate the forming of an electric field. In this case, it will be apparent to those skilled in the art that the size and shape of the ground surface 1500 formed on the PCB 1300 differ in accordance with the frequency band.

The signal receiving surface 1400 serves to transfer the signal received through the dielectric resonator to an input unit of an amplifying end through the resonance frequency shift circuit. In a general monopole antenna, the ground surface is grounded to cause the forming of the electric field to be non-uniform, and this may cause the field strength of the received signal to become weak. To solve this problem, the ground surface is formed on the PCB board 1300 to form uniform field strength.

As described above, the antenna according to the present invention can greatly reduce the size of the antenna by using the dielectric resonator as the antenna and shifting the resonance frequency of the dielectric resonator, and thus it can be used in diverse devices. Accordingly, the present invention can greatly contribute to the miniaturization of a relatively low-frequency communication terminal such as a DMB terminal and a DMB USB driver, and a portable phone using cellular or PCS.

In the general dipole antenna having a low Q value, the resonance point is distorted if the length of the antenna is not accurately determined, and this causes the gain of the antenna to be greatly reduced. According to the present invention, it is possible for the antenna to have a higher Q value, and thus a wider receiving bandwidth of the antenna can be secured.

Industrial Applicability

As can be seen from the foregoing, the miniature antenna according to embodiments of the present invention, which is smaller than the existing antenna, can be used even in the low frequency band, and thus it can greatly contribute to the miniaturization of diverse kinds of portable devices such a portable phone, a ground-wave DMB receiver, and so forth.

In addition, the miniature antenna according to the present invention has a good receiving sensitivity in comparison to the conventional dipole antenna.

While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment and the drawings, but, on the contrary, it is intended to cover various modifications and variations within the spirit and scope of the appended claims.

Claims

1. An RF antenna using a dielectric resonator, comprising: the dielectric resonator for resonating a signal of a predetermined frequency band; and a resonance frequency shift circuit, coupled to the dielectric resonator, for shifting the frequency resonating in the dielectric resonator; wherein the dielectric resonator has the resonance characteristic in a frequency band higher than a frequency band intended to be received, and the resonance frequency shift circuit changes the resonance characteristic of the dielectric resonator so that the dielectric resonator resonates in a frequency band lower than the predetermined frequency band.

2. The RF antenna of claim 1, wherein the resonance frequency shift circuit is connected to the dielectric resonator in parallel.

3. The RF antenna of claim 1, wherein the resonance frequency shift circuit is connected to the dielectric resonator in series .

4. The RF antenna of claim 1, wherein an internal circuit that performs a predetermined signal process with respect to an output signal of the antenna is coupled to the antenna.

5. The RF antenna of claim 2 or 3, wherein the resonance frequency shift circuit is composed of a combination of at least one inductor and at least one capacitor.

6. The RF antenna of claim 5, wherein the resonance frequency shift circuit shifts the resonance frequency of the dielectric resonator by using the combination of the inductor and the capacitor connected in parallel.

7. The RF antenna of claim 2, wherein the resonance frequency shift circuit comprises: a first inductor connected to one end part of the dielectric resonator; a second inductor connected to the first inductor; a first capacitor connected in parallel to the second inductor; and a second capacitor connected in series to the other end part of the dielectric resonator.

8. The RF antenna of claim 3, wherein the resonance frequency shift circuit comprises: a first inductor connected in series to the dielectric resonator; a second inductor connected in series to the first inductor; a first capacitor connected in parallel to the second inductor; and a second capacitor connected in series to the second inductor.

9. The RF antenna of claim 1, wherein the resonance frequency shift circuit is formed on a PCB, and the PCB on which the resonance frequency shift circuit is formed is coupled to the dielectric resonator.

10. An RF antenna using a dielectric resonator, comprising : the dielectric resonator for resonating a signal of a predetermined frequency band; and a resonance frequency shift circuit, coupled to the dielectric resonator, for shifting the frequency resonating in the dielectric resonator; wherein the resonance frequency shift circuit is formed on a PCB, the PCB is coupled to the dielectric resonator, and the resonance frequency shift circuit is composed of a combination of at least one inductor and at least one capacitor.

11. The RF antenna of claim 10, wherein the dielectric resonator is coupled to the PCB using a pad.

12. An active RF antenna using a dielectric resonator, comprising: the dielectric resonator for resonating a signal of a predetermined frequency band; and a resonance frequency shift circuit, coupled to the dielectric resonator, for shifting the resonance frequency band of the dielectric resonator; wherein the resonance frequency shift circuit is composed of a coil having a core of which a shift range of the resonance frequency band is determined according to a user's manipulation.

13. The active RF antenna of claim 12, wherein the dielectric resonator and the resonance frequency shift circuit are formed on a PCB.

14. The active RF antenna of claim 13, further comprising a ground surface, formed on the same surface of the dielectric resonator and the PCB on which the resonance frequency shift circuit is formed, for facilitating the forming of an electric field.

15. The active RF antenna of claim 14, further comprising an amplifying circuit, formed on the PCB, for amplifying a signal received through the dielectric resonator to output the amplified signal.

16. The active RF antenna of claim 15, wherein the dielectric resonator, the resonance frequency shift circuit, the amplifying circuit, and the ground surface are formed in a body on the PCB.