Parasitic elements diversity antenna

1. Antenna diversity of an electronic device, in particular of a cellular terminal, comprising:

a first and a second antenna element ( 110 a , 110 b ) one of which being operated in an active mode by being connected to a transceiver ( 160 ) of said electronic device for transceiving electromagnetic signals whereas the other one of which being operated in a parasitic mode by interfering the impedance of the antenna element in the active mode due to electromagnetic coupling; wherein the antenna element ( 110 a , 110 b ) in the parasitic mode has an adjustable impedance; characterized by

a switching unit ( 120 ) for either operating the first antenna element ( 110 a ) in the parasitic mode and simultaneously operating the second antenna element ( 110 b ) in the active mode or alternatively operating the first antenna element in the active mode and simultaneously operating the second antenna element in the parasitic mode;

a pre-selection unit ( 130 ) for providing N configurations of the antenna diversity ensuring that the amount of a mismatch between the impedance of the antenna element in the active mode and the impedance of the transceiver ( 160 ) is below a predetermined threshold value, respectively, wherein each of said configurations represents a particular position of the switching unit ( 120 ) in combination with a particular predetermined amount of the impedance ( 170 a or 170 b ) of that antenna element which is—due to the position of said switching unit ( 120 )—operated in the parasitic mode;

a selection unit ( 140 ) for selecting that single specific configuration out of the plurality of the N configurations provided by the pre-selection unit ( 130 ) fulfilling a predetermined signal quality criterion for the transceived electromagnetic signal best; and

a control unit ( 150 ) for adjusting the position of the switching unit ( 120 ) and the amount of the impedance ( 170 a or 170 b ) of that antenna element which is—due to the position of the switching unit ( 120 )—operated in the parasitic mode, according to the selected specific configuration.

2. Method for operating an antenna diversity as used for an electromagnetic device, in particular for a cellular terminal, the diversity including a first and a second antenna element one of which being operable in an active mode by being connected to a transceiver ( 160 ) of said electronic device for transceiving electromagnetic signals whereas the other one of which being operable in a parasitic mode by interfering the impedance of the antenna element in the active mode due to electromagnetic coupling to said antenna element in the active mode; the method being characterized by the steps of:

providing N configurations of the antenna diversity ensuring that the amount of a mismatch between the impedance of the antenna element in the active mode and the impedance of the transceiver ( 160 ) is below a predetermined threshold value, respectively, wherein each of said configurations represents a particular situation in which either the first antenna element ( 110 a ) is operated in the parasitic mode and simultaneously the second antenna element ( 110 b ) is operated in the active mode or vice versa in combination with a particular predetermined amount of the impedance ( 170 a , 170 b ) of that antenna element which is currently operated in the parasitic mode;

selecting that single specific configuration out of the plurality of the N configurations fulfilling a predetermined signal quality criterion for the transceived electromagnetic signal best; and

adjusting the selected specific configuration.

3. Method according to claim 2 , characterized in that the method steps are repeated occasionally or after a predetermined time interval.

4. Method according to claim 2 , characterized in that the step of providing the N configurations comprises the substeps of:

a1) operating the first antenna element in the active mode and the second antenna element in the parasitic mode;

a2) sequentially varying the impedance of the second antenna element to n1 different amounts and detecting the co-ordinated amounts of mismatch between the impedance of the first antenna element and the impedance of the transceiver ( 160 ) as well as the co-ordinated degree of performance of the signal quality criterion for the electromagnetic signal transceived by the first antenna element, respectively;

b1) operating the first antenna element in the parasitic mode and the second antenna element in the active mode;

b2) sequentially varying the impedance of the first antenna element to n2 different amounts and detecting the co-ordinated amounts of mismatch between the impedance of the second antenna element and the impedance of the transceiver ( 160 ) as well as the co-ordinated degree of performance of the signal quality criterion for the electromagnetic signal transceived by the second antenna element, respectively; and

c) selecting and providing those N configurations out of the n1+n2 configurations with N≦n 1+n 2 the amounts of impedance mismatch of which are below a predetermined threshold value.