Tunable antenna and terminal

1. A tunable loop antenna, comprising:

a circuit board;

an antenna body configured to transmit and receive a signal of a first frequency band, wherein the antenna body comprises a feed end and a ground pin, and wherein the feed end is disposed on the circuit board; and

an electrical tuning network, wherein a ground point disposed on the circuit board is connected to the ground pin of the antenna body using the electrical tuning network, wherein the electrical tuning network comprises an inductor and a first tunable capacitor with a tunable capacitance value, wherein the inductor is connected in series to the first tunable capacitor, and wherein a load value of the inductor is reduced by tuning a first capacitance value of the first tunable capacitor such that a first effective electrical length of the antenna body is reduced.

2. The tunable loop antenna according to claim 1 , wherein the electrical tuning network further comprises a second tunable capacitor connected in parallel to the inductor and the first tunable capacitor, wherein the tunable antenna is configured to open circuit the second tunable capacitor to reduce the load value using the first tunable capacitor such that the first effective electrical length is reduced when the second tunable capacitor is open-circuited, and wherein the tunable antenna is configured to short circuit the first tunable capacitor to increase the load value using the second tunable capacitor such that the first effective electrical length is increased when the first tunable capacitor is short-circuited.

3. The tunable loop antenna according to claim 1 , wherein the electrical tuning network is connected to a tail end of the ground pin or connected to an area that is on the antenna body and near the ground pin.

4. The tunable loop antenna according to claim 1 , wherein the tunable antenna further comprises a parasitic antenna stub disposed on the circuit board and configured to excite a high-frequency mode of the first frequency band.

5. The tunable loop antenna according to claim 1 , wherein the antenna body is disposed at an edge of the circuit board.

6. The tunable loop antenna according to claim 4 , wherein the parasitic antenna stub is disposed at an edge of the circuit board and near the feed end.

7. The tunable loop antenna according to claim 4 , wherein the electrical tuning network, further comprises a second tunable capacitor disposed at a tail end of the parasitic antenna stub, and wherein the first effective electrical length and a second effective electrical length of the parasitic antenna stub are changed by tuning a second capacitance value of the second tunable capacitor.

8. A terminal, comprising:

a processor; and

a tunable antenna coupled to the processor, wherein the tunable antenna comprises:

a circuit board;

an antenna body configured to transmit and receive a signal of a first frequency band, wherein the antenna body comprises a feed end and a ground pin, and wherein the teed end is disposed on the circuit board; and

an electrical tuning network, wherein a ground point disposed on the circuit board is connected to the ground pin of the antenna body using the electrical tuning network,

wherein the electrical tuning network comprises an inductor and a first tunable capacitor with a first tunable capacitance value,

wherein the inductor is connected in series to the first tunable capacitor,

wherein a load value of the inductor is changed by tuning the first capacitance value of the first tunable capacitor such that a first effective electrical length of the antenna body is reduced, and

wherein the processor is configured to process transmitted and received signals of the tunable antenna.

9. The terminal according to claim 8 , wherein the first electrical tuning network further comprises a second tunable capacitor connected in parallel to the inductor and the first tunable capacitor, wherein the tunable antenna is configured to open circuit the second tunable capacitor to reduce the load value using the first tunable capacitor such that the first effective electrical length is reduced when the second tunable capacitor is open-circuited, and wherein the tunable antenna is configured to short circuit the first tunable capacitor to increase the load value using the second tunable capacitor such that the first effective electrical length is increased when the first tunable capacitor is short-circuited.

10. The terminal according to claim 8 , wherein the electrical tuning network is connected to a tail end of the ground pin or connected to an area that is on the antenna body and near the ground pin.

11. The terminal according to claim 8 , wherein the tunable antenna further comprises a parasitic antenna stub disposed on the circuit board and configured to excite a high-frequency mode of the first frequency band.

12. The terminal according to claim 8 , wherein the antenna body is disposed at an edge of the circuit board.

13. The terminal according to claim 11 , wherein the parasitic antenna stub is disposed at an edge of the circuit board and near the feed end.

14. The terminal according to claim 11 , wherein the tunable antenna further comprises a second tunable capacitor disposed at a tail end of the parasitic antenna stub, and wherein the first effective electrical length and a second effective electrical length of the parasitic antenna stub are changed by tuning a second capacitance value of the second tunable capacitor.