Antenna diversity system and method for operating said system

1. Antenna diversity, comprising:

a first antenna element and a second antenna element, the first antenna element arranged for operating in an active mode and comprising a connection for connecting the first antenna element to a transceiver of said electronic device for transceiving electromagnetic signals and the second antenna arranged for operation in a parasitic mode by interfering the impedance of the first antenna element due to electromagnetic coupling, wherein the second antenna element in the parasitic mode is terminated by an adjustable impedance;

a pre-selection unit for adjusting the adjustable impedance ensuring that the amount of a mismatch between the impedance of the antenna element in the active mode and the impedance of the transceiver is below a predetermined threshold value,

a selection unit for adjusting the adjustable impedance within a range determined by the pre-selection unit fulfilling a predetermined received signal quality criterion for the transceived electromagnetic signal best.

2. Method for operating an antenna diversity, the diversity including a first and a second antenna element, the first antenna element being operated in an active mode by being connected to a transceiver for transceiving electromagnetic signals and the second antenna element being operated in a parasitic mode by interfering the impedance of the first antenna element due to electromagnetic coupling to the first antenna element, the method comprising:

adjusting an adjustable impedance ensuring that the amount of a mismatch between the impedance of the antenna element in the active mode and the impedance of the transceiver is below a predetermined threshold value;

selecting the adjustable impedance within a range determined by a pre-selection unit fulfilling a predetermined received signal quality criterion for the transceived electromagnetic signal best.

3. Method according to claim 2 , wherein said adjusting and selecting are repeated by selecting one of occasionally, after a predetermined time interval, after a change in the mismatch, and after a change of received signal quality.

4. Method according to claim 2 , wherein the step of adjusting the adjustable impedance comprises

sequentially varying the adjustable 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 as well as the co-ordinated degree of performance of the signal quality criterion for the electromagnetic signal transceived by the first antenna element.

5. Integrated circuit comprising:

a transceiver and;

a first input for connecting a first antenna element to transceiver for transceiving electromagnetic signals and;

a second input for connecting a second antenna arranged for operation in a parasitic mode by interfering the impedance of the first antenna element due to electromagnetic coupling;

an adjustable impedance connected to the second input for terminating the second antenna element;

a pre-selection unit connected to the first input and comprising an output for adjusting the adjustable impedance where the pre-selection unit is operative to ensure that the amount of a mismatch between the impedance of the antenna element in the active mode and the impedance of the transceiver is below a predetermined threshold value,

a selection unit connected to the preselection unit and to an output of the transceiver providing received signal quality information, where the selection unit is operative to adjust the adjustable impedance within a range determined by the pre-selection unit fulfilling a predetermined received signal quality criterion for the transceived electromagnetic signal best.