An RF circuit (131 138) satisfies Pnoise+NF+G.ltoreq.Plim+sW (0.ltoreq.s.ltoreq.4) at an edge of a guard band with respect to a required transmission level PAll, an upper tolerance level of out-of-band noise Plim, a guard bandwidth W, and a noise level Pnoise, where NF is a noise figure and G is a gain. An IF circuit (121 123) satisfies PAll.ltoreq.Pin+G, where PIF is an output level of a BPF (123). Out-of-band noise levels are reduced to Pnoise by the steep BPF (123). The RF circuit (131 138) is structured so that noise from a local oscillator circuit (134) does not surpass noise from the IF circuit (121 123). Reductions in power consumption are thus realized in addition to guard bandwidth reductions, because of being able to eliminate out-of-band noise from an amplifier (138) using a low-loss filter (140) having an attenuation slope s.