Antenna assembly and wireless unit employing it
An object of the invention is to provide an antenna apparatus whose directional characteristic can be switched 90 degrees conforming to the communication mode at the same time as the frequency band can be switched in response to the communication mode for application to a multiband radio for covering different communication modes such as voice communications and data communications, and a radio using the antenna apparatus. An antenna apparatus 1 of the invention includes linear radiator 2, 3 ; a first linear director 4 ; and first and second linear conductors 5 and 6 connected at one end to the radiator 2, 3 and at an opposite end to the first director 4 through switches 7 . The first and second conductors 5 and 6 are disposed symmetrically with respect to an orthogonal plane in the length direction of the radiator, and the radiator 2, 3 , the first director 4 , the first conductor 5 , and the second conductor 6 are switched between a loop state in which they are connected like a loop and a separate state in which they are separate by switching the switches 7.
1. An antenna apparatus comprising:
a linear radiator;
a first linear director; and
first and second linear conductors each being connected at one end to the radiator and at an opposite end to the first director through switches,
wherein the first and second conductors are disposed symmetrically with respect to an orthogonal plane in the length direction of the radiator,
wherein the radiator, the first director, the first conductor, and the second conductor are switched between a loop state in which they are connected like a loop and a separate state in which they are separate by switching the switches, and
wherein in the loop state, the antenna apparatus operates as a loop antenna corresponding to a first frequency band, and in the separate state, the antenna apparatus operates as a Yagi-Uda antenna corresponding to a second frequency band.
2. The antenna apparatus according to claim 1 , wherein the radiator, the first director, and the first and second conductors connected through the switches form a rectangular structure.
3. The antenna apparatus according to claim 1 , comprising first and second variable reactive elements connected to the first and second conductors.
4. The antenna apparatus according to claim 3 , wherein the first and second variable reactive elements are inserted onto the lines of the first and second conductors.
5. The antenna apparatus according to claim 1 , wherein one ends of the first and second conductors are connected at right angles to at least either the radiator or the first director.
6. The antenna apparatus according to claim 5 , wherein the radiator, the first director, and the first and second conductors connected through the switches form a convex structure on the same plane.
7. The antenna apparatus according to claim 5 , wherein the radiator, the first director, and the first and second conductors connected through the switches form a concave structure on the same plane.
8. The antenna apparatus according to claim 1 , comprising a second linear director placed between the radiator and the first director.
9. The antenna apparatus according to claim 8 , wherein the first director and the second linear director are placed in parallel with the radiator.
10. The antenna apparatus according to claim 1 , wherein power is fed into the radiator using a balanced line.
11. The antenna apparatus according to claim 1 , wherein power is fed into the radiator using an unbalanced line.
12. The antenna apparatus according to claim 1 , wherein the radiator, the director, and the first and second conductors are formed according to a conductor pattern on a dielectric substrate.
13. The antenna apparatus according to claim 1 , wherein the radiator, the first director, and the first and second conductors are formed on the surface of and/or inside a dielectric chip.
14. The antenna apparatus according to claim 1 , wherein the switch consists of diodes.
15. The antenna apparatus according to claim 1 , wherein the switch consists of MEMS switches.
16. A radio using the antenna apparatus according to claim 1 .
17. The antenna apparatus according to claim 1 , wherein the first frequency band is a low frequency band, and the second frequency band is a high frequency band.
18. The antenna apparatus according to claim 1 , wherein the first frequency band is for voice communications, and the second frequency band is for data communications.
19. The antenna apparatus according to claim 1 , comprising a control unit which controls switching the switches.
20. The antenna apparatus according to claim 19 ,
wherein the radiator comprises first and second linear radiators having the same length, and
wherein the control unit comprises:
a first choke coil connected at one end to the first radiator and grounded at an opposite end; and
a second choke coil connected at one end to the second radiator and at an opposite end to a control terminal and bypass capacitor grounded at one end.
21. The antenna apparatus according to claim 19 ,
wherein the radiator comprises first and second linear radiators having the same length, and
wherein the control unit comprises:
a first choke coil connected at one end to the first and second radiators and the first director and grounded at an opposite end; and
a second choke coil connected at one end to the first and second conductors and at an opposite end to a control terminal and a bypass capacitor grounded at one end.
22. The antenna apparatus according to claim 19 ,
wherein the radiator comprises first and second linear radiators having the same length,
wherein the control unit comprises:
a first stub connected at one end to the first radiator;
a first resonance circuit connected at one end to an opposite end of the first stub and grounded at an opposite end, the first resonance circuit for resonating in a first frequency band;
a second stub connected at one end to the opposite end of the first stub and grounded at an opposite end;
a third stub connected at one end to the second radiator;
a second resonance circuit connected at one end to an opposite end of the third stub and grounded at an opposite end, the second resonance circuit for resonating in the first frequency band; and
a fourth stub connected at one end to the opposite end of the third stub and at an opposite end to a control terminal and a bypass capacitor grounded at one end, and
wherein the length of each of the first and third stubs becomes one quarter guide wavelength in the first frequency band and the sum of the lengths of the first and second stubs and the sum of the lengths of the third and fourth stubs become each one quarter guide wavelength in a second frequency band lower than the first frequency band.
23. The antenna apparatus according to claim 19 ,
wherein the radiator comprises first and second linear radiators having the same length,
wherein the control unit comprises:
a first stub connected at one end to the first and second radiators and the first director;
a first resonance circuit connected at one end to an opposite end of the first stub and grounded at an opposite end, the first resonance circuit for resonating in a first frequency band;
a second stub connected at one end to the opposite end of the first stub and grounded at an opposite end;
a third stub connected at one end to the first and second conductors;
a second resonance circuit connected at one end to an opposite end of the third stub and grounded at an opposite end, the second resonance circuit for resonating in the first frequency band; and
a fourth stub connected at one end to the opposite end of the third stub and at an opposite end to a control terminal and a bypass capacitor grounded at one end, and
wherein the length of each of the first and third stubs becomes one quarter guide wavelength in the first frequency band and the sum of the lengths of the first and second stubs and the sum of the lengths of the third and fourth stubs become each one quarter guide wavelength in a second frequency band lower than the first frequency band.