ANTENNA DEVICES AND PORTABLE ELECTRONIC DEVICES COMPRISING SUCH ANTENNA DEVICES
An exemplary embodiment of an antenna device generally includes a radiator structure with at least one first radiator element. The antenna device also includes a first feeding connection coupling the radiator structure to a first radio circuit for operation in a first frequency band. The antenna device further includes a second feeding connection coupling the radiator structure to a second radio circuit for operation in a second frequency band. A set of capacitors is connected to the radiator structure. This set includes at least one capacitor where a first end of each capacitor in the set is connected to the radiator structure and a second end is provided at ground potential, at least for the first frequency band. The sum of the values of the capacitors in the set is below 15 picofarads.
1 . An antenna device for operation in at least a first lower and a second higher frequency band, the antenna device comprising:
a radiator structure including at least one first radiator element and having a first and a second end;
a first feeding connection coupling the radiator structure to a first radio circuit for operation in the first frequency band;
a second feeding connection coupling the radiator structure to a second radio circuit for operation in the second frequency band;
a set of capacitors connected to the radiator structure and including at least one capacitor, where a first end of each capacitor in the set is connected to the radiator structure and a second end is provided at ground potential, at least for the first frequency band, and the sum of the values of the capacitors in the set is below 15 picofarads.
2 . The antenna device of claim 1 , further comprising a first low pass filter series-connected in the first feeding connection between the first radio circuit and the radiator structure.
3 . The antenna device of claim 1 , wherein the set of capacitors comprises a first capacitor connected to the radiator structure.
4 . The antenna device of claim 3 , wherein the first capacitor is series-connected in the second feeding connection.
5 . The antenna device of claim 3 , further comprising a second low pass filter connected between the second end of the first capacitor and ground.
6 . The antenna device of claim 1 , wherein the set of capacitors comprises a second capacitor connected between the second end of the radiator structure and ground.
7 . The antenna device of claim 1 , wherein the radiator structure comprises a second radiator element coupled to the first radiator element via a third low pass filter.
8 . The antenna device of claim 1 , wherein the radiator structure has a length corresponding to the whole length of a first side of a circuit board of a portable radio communication device.
9 . The antenna device of claim 8 , wherein the first side is a short side of the circuit board.
10 . The antenna device of claim 8 , further comprising a common feeding connection joining the first and the second feeding connections to the radiator structure, the common feeding connection being configured to stretch at right angles to the longitudinal extension of the radiator structure along a second side of the circuit board.
11 . The antenna device of claim 10 , further comprising a parasitic element placed adjacent the common feeding connection.
12 . The antenna device of claim 11 , further comprising a third capacitor connected between the parasitic element and ground.
13 . The antenna device of claim 1 , further comprising a matching unit connected between the first feeding connection and ground.
14 . The antenna device of claim 1 , further comprising a resistor connected between the radiator structure and ground.
15 . The antenna device of claim 1 , wherein antenna device includes one or more low pass filters designed for allowing signals in the first frequency band and blocking signals in the second frequency band.
16 . The antenna device of claim 1 , wherein the first radio circuit includes an amplifier, and wherein the capacitors of the set, radiator structure, and any other electrical components connected to the radiator structure provide an impedance that is close to the optimal noise impedance of the amplifier in the first frequency band.
17 . The antenna device of claim 1 , wherein:
the first frequency band is the FM band; and/or
the second frequency band includes at least one cellular frequency band.
18 . A portable radio communication device comprising in its interior:
an antenna device of claim 1 ;
a circuit board; and
a first and a second radio circuit connected to the antenna device.
19 . The portable radio communication device of claim 18 , wherein the radiator structure is provided above a part of the circuit board lacking a ground plane.
20 . The portable radio communication of claim 18 , wherein:
the circuit board has a first side; and
the radiator structure stretches along the whole length of this first side.