A wireless device (e.g., a cellular phone or a smartphone) in a wireless communication system may transmit and receive data for two-way communication. The wireless device may include a transmitter for data transmission and a receiver for data reception. For data transmission, the transmitter may modulate a radio frequency (RF) carrier signal with data to generate a modulated RF signal, amplify the modulated RF signal to generate a transmit RF signal having the proper output power level, and transmit the transmit RF signal via an antenna to another device such as, for example, a base station. For data reception, the receiver may obtain a received RF signal via the antenna and may amplify and process the received RF signal to recover data sent by the other device.
The wireless device may operate within multiple frequency bands. For example, the wireless device may transmit and/or receive an RF signal within a first frequency band and/or within a second frequency band. To support multiple frequency bands and/or diversity operation, the wireless device may include a plurality of transceivers. Each transceiver may include an independent transmitter and receiver that may be tuned to operate within different frequency bands through independent local oscillators.
Calibration of the receivers may require one or more calibration signals with characteristics (e.g., frequencies) similar to local oscillator frequencies of one or more nearby receivers. Implementing signal generators to generate the calibration signals may increase a die size (and therefore the cost) of an associated integrated circuit and introduce complex calibration signal circuit routing to the receiver design.
Thus, there is a need for a low cost, die efficient approach to provide calibration signals to calibrate the receivers of a wireless device.