Front-end circuit
The present invention concerns a front-end circuit (FEC) that is connectable to at least two radiators (RAD 1 M, RAD 1 D), wherein the front-end circuit (FEC) comprises sub-circuits (SC) and each sub-circuit (SC) is associated to one radiator (RAD 1 M, RAD 1 D). Further, each sub-circuit (SC) comprises a signal path (SP), an antenna port (AP) that is electrically coupled to the signal path (SP) and connectable to the radiator (RAD 1 M, RAD 1 D), a grounding port (GP) that is connectable to the radiator (RAD 1 M, RAD 1 D), a ground termination circuit (GTC), and a grounding switch (GS) that is electrically coupled to the grounding port (GP) and to the grounding termination circuit (GTC).
1. A front-end circuit, that is connectable to at least two radiators, the front-end circuit comprising:
sub-circuits, each sub-circuit being associated to one radiator,
wherein each sub-circuit comprises:
a signal path;
an antenna port that is electrically coupled to the signal path and connectable to the radiator;
a grounding port that is connectable to the radiator;
a ground termination circuit;
a grounding switch that is electrically coupled to the grounding port and to the grounding termination circuit; and
an antenna termination circuit and an antenna switch that is electrically connected to the antenna port,
wherein the antenna switch can connect the antenna port to one of the signal path or the antenna termination circuit,
wherein the grounding termination circuit allows adjusting the impedance for an operating radiator, and
wherein the antenna termination circuit allows choosing from several possibilities to terminate the radiator such that the antenna termination circuit allows adjusting the impedance of an unused, non-operation radiator.
2. The front-end circuit according to claim 1 , wherein the ground termination circuit comprises at least two termination paths, each termination path has a different impedance and the grounding switch can connect the grounding port to one of the termination paths respectively at a given time so that the radiator has different impedances for different configurations of the grounding switch.
3. The front-end circuit according to claim 1 , wherein the ground termination circuit comprises an impedance element selected from: a resistance element, a capacitive element, an inductive element and a LCR-circuit.
4. The front-end circuit according to claim 3 , wherein the ground termination circuit provides one or more individually selectable states chosen from an open state and a short-terminated state and an individual-terminated state, and
wherein in the individual-terminated state the ground switch electrically connects the impedance element to the grounding port.
5. The front-end circuit according to claim 1 , wherein the ground termination circuit comprises an LCR network, implemented with discrete components or transmission lines.
6. The front-end circuit according to claim 5 , wherein the LCR network is tunable.
7. The front-end circuit according to claim 1 , wherein the front-end circuit comprises impedance elements or filters, and
wherein the impedance elements or filters are integrated in the ground termination circuit.
8. The front-end circuit according to claim 1 , wherein the ground termination circuit comprises additional switches in a cascade or parallel configuration,
wherein each switch is followed by another switch or by one of an open-terminated path, a short-terminated path or an individual-terminated path, and
wherein in the individual-terminated path an impedance element is electrically connected to the grounding port.
9. The front-end circuit according to claim 1 , for use in a multiband communication device.
10. The front-end circuit according to claim 1 , that is specified for LTE communication.
11. A method for driving a front-end circuit of claim 1 , the method comprising the steps of:
determining at least one active radiator;
electrically connecting the grounding port which is coupled to the active radiator to a termination path of the ground termination circuit;
determining at least one inactive radiator; and
electrically connecting the antenna port which is coupled to the inactive radiator to a termination path of the antenna termination circuit.
12. The method according to claim 11 , further comprising the steps of:
consulting a mode table regarding optimal antenna performance;
electrically connecting the grounding port which is coupled to the active radiator to a termination path of the ground termination circuit according to the mode table via selecting and setting the according switching state of the respective grounding switch; and
electrically connecting the antenna port which is coupled to the inactive radiator to a termination path of the antenna termination circuit according to the mode table via selecting and setting the according switching state of the respective antenna switch.
13. The method according to claim 12 , further comprising the step of:
electrically connecting the grounding port which is coupled to the inactive radiator to a termination path of the ground termination circuit according to the mode table via selecting and setting the according switching state of the respective grounding switch.