Antenna for portable terminal and portable terminal using same
A dielectric resonator antenna which emits an electric wave by having a dielectric body resonate is disclosed. A magnetic material is contained in the electric body, thereby increasing the relative permeability to more than 1 and lowering the relative permittivity. Consequently, the Q-value of the resonance can be lowered while maintaining the rate of wavelength shortening. With this technique, a broadband dielectric resonator antenna can be realized.
1. A dielectric resonator antenna being adapted to emit a radio wave by resonating a signal, said dielectric resonator antenna comprising:
a conductive plate having a first and a second surface which are faced opposite to each other;
a dielectric placed opposite to said first surface of the conductive plate, said dielectric having a relative permeability (μra) of μra >1;
an electrode provided to said dielectric and adapted to be supplied with said signal; and
a magneto-dielectric layer placed on said second surface of the conductive plate;
wherein said dielectric contains a magnetic material and a dielectric material to have frequency vs. antenna input impedance characteristics in which frequencies are partly superimposed in a half of resonance peak between a first mode on a low frequency side and a second mode on a high frequency side, and
wherein said magneto-dielectric layer has a relative permeability (μrr) and a relative permittivity (∈rr), where μrr is not less than ∈rr, whereby said magneto-dielectric layer produces a mirror-image effect with respect to an electric field.
2. The dielectric resonator antenna according to claim 1 , wherein said dielectric is mounted directly on said first surface of the conductive plate.
3. The dielectric resonator antenna according to claim 1 , further comprising an insulator which is mounted on said first surface of the conductive plate and has a relatively permittivity (∈rd) of ∈rd>1, wherein said dielectric is mounted on said insulator.
4. The dielectric resonator antenna according to claim 1 , wherein a wavelength shortening coefficient is 200 or less.
5. The dielectric resonator antenna according to claim 1 , wherein a wavelength shortening coefficient is 100 or less.
6. The dielectric resonator antenna according to claim 1 , wherein a wavelength shortening coefficient is 50 to 3.
7. The dielectric resonator antenna according to claim 1 , wherein said magnetic material contains at least one of a simple substance of cobalt, manganese, or iron, and an alloy and a compound magnetic material each containing at least one of cobalt, manganese, and iron.
8. The dielectric resonator antenna according to claim 1 , wherein said dielectric material contains one or both of a resin material containing at least one of liquid crystal resin, epoxy resin, olefin-based resin, fluororesin, BT (bismaleimide triazine) resin, and polyimide resin and an inorganic dielectric material containing at least one of silica (SiO 2 , SiO), silicon nitride (SiN, Si 3 N 4 ), zirconia (ZrO, ZrO 2 ), hafnia (HfO, HfO 2 ), titania (TiO, TiO 2 ), aluminum nitride (AIN), SrBi 2 Ta 2 O 9 , SrBi 2 (Ta 1-x ,Nb x ) 2 O 9 , Sr 2 (Ta 1-x ,Nb x ) 2 O 7 , BST (barium strontium titanate), PZT (lead zirconate titanate), alumina (Al 2 O 3 ), BiTiO 3 , SrTiO 3 , PbZrO 3 , PbTiO 3 , and CaTiO 3 .
9. The dielectric resonator antenna according to claim 8 , wherein fine powder of said magnetic material is dispersed into said resin material.
10. The dielectric resonator antenna according to claim 9 , wherein said inorganic dielectric material is further dispersed into said resin material.
11. A portable terminal including the dielectric resonator antenna according to claim 1 .
12. A portable terminal including a plurality of dielectric resonator antennas each according to claim 1 and being capable of adjusting a radio wave radiation direction.
13. A method of manufacturing a dielectric resonator antenna that emits a radio wave by radiating a radio wave to a resonator formed by a dielectric and resonating said radiated radio wave in said dielectric, said method comprising:
adjusting a relative permittivity on condition that a relative permeability exceeds 1, to thereby obtain a magneto-dielectric material that can achieve a predetermined wavelength shortening coefficient;
forming said dielectric by the use of said magneto-dielectric material, wherein said dielectric contains a magnetic material and a dielectric material to have frequency vs. antenna input impedance characteristics in which frequencies are partly superimposed in a half of resonance peak between a first mode on a low frequency side and a second mode on a high frequency side; and
forming a magneto-dielectric layer having a relative permeability (μrr) and a relative permittivity (∈rr), where μrr is not less than ∈rr, whereby said magneto-dielectric layer produces a mirror-image effect with respect to an electric field,
wherein said magneto-dielectric material is produced by mixing together the magnetic material and the dielectric material.
14. A method of manufacturing a dielectric resonator antenna that emits a radio wave by radiating a radio wave to a resonator formed by a dielectric and resonating said radiated radio wave in said dielectric, said method comprising:
adjusting a relative permittivity on condition that a relative permeability exceeds 1, to thereby obtain a magneto-dielectric material that can achieve a predetermined wavelength shortening coefficient;
forming said dielectric by the use of said magneto-dielectric material, wherein said dielectric contains a magnetic material and a dielectric material to have frequency vs. antenna input impedance characteristics in which frequencies are partly superimposed in a half of resonance peak between a first mode on a low frequency side and a second mode on a high frequency side; and
forming a magneto-dielectric layer having a relative permeability (μrr) and a relative permittivity (∈rr), where μrr is not less than ∈rr, whereby said magneto-dielectric layer produces a mirror-image effect with respect to an electric field.
15. The method according to claim 14 , wherein said magnetic material contains at least one of a simple substance of cobalt, manganese, or iron, and an alloy and a compound magnetic material each containing at least one of cobalt, manganese, and iron.
16. The method according to claim 14 , wherein said dielectric material contains one or both of a resin material containing at least one of liquid crystal resin, epoxy resin, olefin-based resin, fluororesin, BT (bismaleimide triazine) resin, and polyimide resin and an inorganic dielectric material containing at least one of silica (SiO 2 , SiO), silicon nitride (SiN, Si 3 N 4 ), zirconia (ZrO, ZrO 2 ), hafnia (HfO, HfO 2 ), titania (TiO, TiO 2 ), aluminum nitride (AIN), SrBi 2 Ta 2 O 9 , SrBi 2 (Ta 1−x ,Nb x ) 2 O 9 , Sr 2 (Ta 1−x ,Nb x ) 2 O 7 , BST (barium strontium titanate), PZT (lead zirconate titanate), alumina (Al 2 O 3 ), BiTiO 3 , SrTiO 3 , PbZrO 3 , PbTiO 3 , and CaTiO 3 .
17. The method according to claim 16 , further comprising dispersing fine powder of said magnetic material into said resin material.
18. The method according to claim 17 , further comprising dispersing said inorganic dielectric material into said resin material.