Patent ID: 7551666

Claim:
A wireless communications system for transmitting/receiving a first wireless signal from a first wireless communications device and a second wireless signal from a second wireless communications device, the first and second wireless signals having different frequency bands from each other, wherein: the first wireless communications device includes: a first frequency converter operable to downconvert the second wireless signal transmitted from the second wireless communications device to a first low-frequency signal; a first sampler operable to oversample the first low-frequency signal downconverted by the first frequency converter; and a first demodulation digital circuit operable to demodulate the signal oversampled by the first sampler; the signal demodulated by the first demodulation digital circuit has a center frequency of fi [Hz]; the second wireless communications device includes: a second frequency converter operable to downconvert the first wireless signal transmitted from the first wireless communications device to a second low-frequency signal whose center frequency fd [Hz] is equal to a difference between a center frequency of the first wireless signal and that of the second wireless signal; a second sampler operable to undersample the second low-frequency signal downconverted by the second frequency converter; and a second demodulation digital circuit operable to demodulate the signal undersampled by the second sampler; a sampling frequency used in the first sampler and that used in the second sampler are the same sampling frequency fs [Hz]; the sampling frequency fs [Hz] is set to a value that is an even-number multiple of a wireless symbol transmission rate such that oversampling is done in the first sampler and undersampling is done in the second sampler; and the center frequency fi [Hz] is ½ to 1 times a frequency corresponding to a bandwidth of the first and second wireless signals and is ½ N (N is a natural number) times the sampling frequency fs [Hz].