Patent ID: 8369819

Claim:
A double frequency-conversion receiving circuit for use in a radio-frequency SIM card, the circuit comprising: a low noise amplifier to amplify an antenna signal; a local oscillator to generate a high-local-oscillation signal; a high-medium-frequency mixer, coupled to the low noise amplifier and the local oscillator, to generate a high-medium-frequency signal based on the amplified antenna signal and the high-local-oscillation signal; a frequency divider, coupled to the local oscillator, to perform N frequency dividing to the high-local-oscillation signal generated by the local oscillator, to generate a low-local-oscillation signal, N being a positive integer; a quadrature I/Q circuit, coupled to the frequency divider, to generate a low I/Q local-oscillation signal based on the low-local-oscillation signal; a low-medium-frequency mixer coupled to the high-medium-frequency mixer and the quadrature I/Q circuit, to generate a low-medium-frequency signal based on the high-medium-frequency signal and the low I/Q local-oscillation signal; and a low-medium-frequency processing circuit, coupled to the low-medium-frequency mixer, to generate an output signal based on the low-medium-frequency signal.