Patent ID: 7515662

Claim:
A communication system, comprising: a first terminal; a network coupled to the first terminal; and a second terminal coupled to the network to receive a signal from the first terminal, wherein the second terminal comprises, an antenna configured to output a received signal from the first terminal; receiving circuit that comprises, an IQ mixer configured to output a first signal obtained by combining the received signal with an in-phase signal and a second signal obtained by combining the received signal with a quadrature signal, a first filter configured to receive a test signal during a first period and the first signal during a second period, a second filter configured to receive the test signal during the first period and the second signal during the second period, a test signal generator configured to generate the test signal to detect at least one of a gain ripple characteristic and a group delay characteristic of a filter, a first ADC configured to receive an output signal from the first filter, a second ADC configured to receive an output signal from the second filter, a first filter compensation circuit configured to receive output signals from the first ADC to determine a first coefficient during the first period and compensate for said at least one of the gain ripple characteristic and the group delay characteristic of the first filter by operating according to the first coefficient during the second period, and a second filter compensation circuit configured to receive output signals from the second ADC to determine a second coefficient during the first period and compensate for said at least one of the gain ripple characteristic and the group delay characteristic of the second filter by operating according to the second coefficient during the second period; and a transmitting circuit that comprises, a transmission digital circuit configured to generate a digital signal corresponding to the first signal during the test period and the digital signal corresponding to a transmission signal during a transmission portion of the second period, and a first DAC and a second DAC configured to convert the digital signals received from the transmission digital circuit to an analog signal and to output the analog signal as the test signal during the first period and the analog signal as an output signal during the transmission portion of the second period, and an additional IQ mixer configured to output a third signal to the antenna obtained by combining the output signal with the in-phase signal and a fourth signal to the antenna obtained by combing the output signal with the quadrature signal wherein the test signal comprises a signal having a frequency that is sequentially increased from a lowest frequency to a highest frequency of a pass band of the first filter and the second filter or the frequency of the signal is sequentially decreased from the highest frequency to the lowest frequency of the pass band of the first filter and the second filter.