| 摘要 |
PROBLEM TO BE SOLVED: To provide a direct conversion receiver where reception quality is maintained excellently without increasing its power consumption. SOLUTION: ADC offset voltage is produced in an output base band signal of mixers 14a, 14b because of even harmonic distortions of the mixers 14a, 14b. The DC offset voltage is eliminated by capacitors 19a, 19b and the resulting base band signal is given to A/D converters 20a, 20b. Capacitances of the capacitors 19a, 19b are selected so that a cut-off frequency of a high-pass filter consisting of the capacitors 19a, 19b and input resistors of the A/D converters 20a, 20b is about 1% of a symbol rate of QPSK modulation in use or below. Thus, the effect of the DC offset voltage is disregarded without losing reception quality (BER). |
