Detecting moisture with an antenna

1. A system for moisture detection, the system comprising:

a communication apparatus;

a housing for the communication apparatus comprising a conductive cover separated by a dielectric, the dielectric separating the conductive cover into a first cover part and a second cover part, wherein the first cover part is a first antenna and the second cover part is a second antenna separated by the dielectric, the first antenna and the second antenna being external to the communication apparatus;

an impedance sensor configured to detect an impedance at the second antenna based on a received signal received through a wave medium from the first antenna, the wave medium being in and around the communication apparatus; and

a control circuit configured to detect moisture based on the impedance at the second antenna and transmit a moisture event to a switch that disconnects power to one or more components of the communication apparatus.

2. The system of claim 1 , further comprising an accelerometer, wherein the accelerometer is configured to trigger an interrogation of the second antenna in response to detection of a free-fall event, and wherein the received signal is based on an antenna signal transmitted from the first antenna.

3. The system of claim 2 , wherein the impedance is determined by the impedance sensor as an effective series resistance between the first antenna and the second antenna.

4. The system of claim 2 , wherein the first antenna is a cellular network antenna and the antenna signal is a ping signal transmitted at substantially regular intervals.

5. The system of claim 2 , wherein the impedance sensor is configured to determine the impedance based on a comparison of the antenna signal and the received signal.

6. The system of claim 1 , wherein the impedance sensor is configured to derive the impedance from a voltage and/or a current of a signal received by the second antenna.

7. A non-transitory computer readable storage medium comprising computer executable instructions, the computer executable instructions executable by a processor, the computer executable instructions comprising:

instructions executable to transmit an antenna signal from a first cover part of a housing for a communication apparatus, wherein the first cover part is a first antenna, to a second cover part of the housing, wherein the second cover part is a second antenna, the first antenna and the second antenna forming part of the housing for the communication apparatus and being separated by a dielectric, the first antenna and the second antenna being external to the communication apparatus;

instructions executable to receive an impedance from an impedance sensor, wherein the impedance is electrical impedance at the second antenna detected by the impedance sensor and based on a received signal received through a wave medium from the first antenna, the wave medium being in and around the communication apparatus; and

instructions executable to detect moisture based on the impedance at the second antenna and transmit a moisture event to a switch that disconnects power to one or more components of the communication apparatus.

8. The computer readable storage medium of claim 7 , wherein the moisture is detected in response to a magnitude of the impedance at the second antenna falling below a threshold magnitude.

9. The computer readable storage medium of claim 7 , wherein the moisture is detected in response to a decrease in the impedance detected by the impedance sensor over time.

10. The computer readable storage medium of claim 7 , wherein the moisture is detected as a moisture level, which is determined from a mapping of the impedance to the moisture level.

11. The computer readable storage medium of claim 7 , wherein the moisture is detected in response to detection of a pattern of impedance changes across multiple frequencies.

12. The computer readable storage medium of claim 7 further comprising instructions executable to determine the impedance in response to detection, by the impedance sensor, of signals reflected by the second antenna due to an impedance mismatch between the second antenna and a signal generator.

13. The computer readable storage medium of claim 7 , wherein the impedance is an indication of impedance and/or an indication of a change in the impedance.

14. A method to detect moisture with an antenna, the method comprising:

transmitting an antenna signal from a first cover part of a housing for a communication apparatus, wherein the first cover part is a first antenna, to a second cover part of the housing, wherein the second cover part is a second antenna, the first antenna and the second antenna forming part of the housing for the communication apparatus and being separated by a dielectric, the first antenna and the second antenna being external to the communication apparatus;

detecting, by an impedance sensor, an impedance at the second antenna based on a received signal received through a wave medium from the first antenna, the wave medium being in and around the communication apparatus; and

detecting moisture with a processor based on the impedance at the second antenna wherein the moisture is detected in response to a decrease in the impedance detected by the impedance sensor over time; and

transmitting a moisture event to a switch that disconnects power to one or more components of the communication apparatus.

15. The method of claim 14 , wherein the antenna signal has a voltage and a current, and wherein detecting the impedance comprises determining the impedance by dividing the voltage by the current.

16. The method of claim 15 , wherein in the antenna signal is transmitted at a first frequency, the method further comprising transmitting the antenna signal at a second frequency in response to detection of a fall and/or an impact of the communication apparatus, the communication apparatus including the first antenna, the second antenna, the impedance sensor, and the processor, and wherein the communication apparatus is a mobile phone.