RADIO TERMINAL DEVICE

摘要

A radio terminal device comprises an antenna (10), a transmitter circuit (11), a direct conversion receiver circuit (12), a circulator (13), and a band-rejection filter (14). A direct conversion receiver circuit (12) is smaller in size than a heterodyne receiver circuit and involves fewer spurious signals to be removed. Therefore, the entire radio terminal device becomes small. In addition, the direct conversion receiver circuit (12) comprises even-harmonic mixers (20, 21), and the frequency (flo) of a local oscillator (LO) is 1/2 of the received signal frequency (frx), so that there is no deterioration in sensitivity due to the leakage of local oscillation wave (LO) to the antenna (10).