Antenna apparatus and antenna switch circuit

1. An antenna device, comprising:

a first antenna, configured to transmit an RF signal;

an antenna detection circuit, comprising an inductor configured to detect a second antenna and directly connected between the second antenna and a ground terminal, wherein when the second antenna is absent, the inductor serves as an open-circuit path for a high-frequency signal, when the second antenna is present, the inductor serves as a short-circuited path for a low-frequency signal;

a switch control circuit, coupled to the antenna detection circuit, configured to receive an antenna detection signal generated by the open-circuit path or the short-circuit path to generate a first control signal indicative of the presence of the second antenna upon the detection thereof, and

a controller, coupled to the first antenna, the antenna detection circuit and the switch control circuit, configured to receive the first control signal and connect to the second antenna when the first control signal indicates the presence of the second antenna.

2. The antenna device of claim 1 , wherein the switch control circuit comprises first and second transistors coupled to the inductor, and upon detecting the presence of the second antenna, the first transistor is configured to generate a second control signal to disconnect the first antenna from the controller, and the second transistor is configured to generate the first control signal to connect the second antenna to the controller.

3. The antenna device of claim 1 , further comprises an isolation circuit coupled between the antenna detection circuit from the switch control circuit, configured to separate the antenna detection circuit from the switch control circuit and pass the detection of the second antenna to the switch control circuit.

4. The antenna device of claim 1 , wherein the inductor is configured to indicate the presence of the second antenna device.

5. An antenna switch circuit, comprising:

an antenna detection circuit, comprising only an inductor configured to detect presence of a first antenna and directly connected between the second antenna and a ground terminal, wherein when the second antenna is absent, the inductor serves as an open-circuit path for a high-frequency signal, when the second antenna is present, the inductor serves as a short-circuited path for a low-frequency signal; and

a switch control circuit, coupled to the antenna detection circuit, configured to receive an antenna detection signal generated by the open-circuit path or the short-circuit path to generate a first control signal indicative of the presence of the first antenna upon the detection thereof, and controls a controller to connect to the first antenna according to the first control signal.

6. The antenna switch circuit of claim 5 , wherein the switch control circuit comprises first and second transistors coupled to the inductor, and upon detecting the presence of the first antenna, the first transistor is configured to generate the first control signal, and second transistor is configured to generate a second control signal to disconnect a second antenna from the controller.

7. The antenna switch circuit of claim 5 , further comprises an isolation circuit coupled between the antenna detection circuit from the switch control circuit, configured to separate the antenna detection circuit from the switch control circuit and pass the detection of the first antenna to the switch control circuit.

8. The antenna switch circuit of claim 5 , wherein the inductor is configured to indicate the presence of the first antenna device.