Patent ID: 7006814

Claim:
A direct conversion receiver which is used in a radio unit and converts a reception signal inputted thereto from an antenna directly into a baseband signal, said radio unit using different frequencies for transmission and reception, said receiver comprising: a first local oscillator for generating a first local signal of a first local frequency f LO1 ; a second local oscillator for generating a second local signal of a second local frequency f LO2 ; an internal local signal generator for mixing the first local signal and the second local signal to generate an internal local signal; and a quadrature demodulator for performing quadrature demodulation of the reception signal based on the internal local signal to generate the baseband signal; and wherein, where a carrier frequency of a transmission signal of said radio unit is represented by f t and a carrier frequency of the reception signal is represented by f r and a frequency interval f s between the carrier frequencies of the transmission and reception signals is given as f s =|f r −f t |, when f r >f t , said first local frequency f LO1 satisfies f LO1 ≈f t −f s while said second local frequency f LO2 satisfies f LO2 2·f s and a frequency of the internal local signal is a sum frequency of the first local frequency and the second local frequency, but when f r <f t , the first local frequency f LO1 satisfies f LO1 ≈f t +f s while the second local frequency f LO2 satisfies f LO2 ≈2·f s and the frequency of the internal local signal is a difference frequency between the first local frequency and the second local frequency.