Abstract: Method and system for providing radio frequency by using a mobile computing device. A mobile phone comprises a tag antenna and a motherboard integrated with a radio frequency front end module, a processor and a memory. The tag antenna can receive a request carrier signal and transmit an answering carrier signal. The radio frequency front end module can demodulate the request carrier signal to generate a request baseband signal and transfer to the processor, and modulate an answering baseband signal from the processor to generate the answering carrier signal. The processor can decode the request baseband signal to generate request data, and encode answering data to generate the answering baseband signal and transfer the answering baseband signal to the radio frequency front end module. The answering data include the tag data or response data for representing a result of the write operation.