Patent ID: 8135366

Claim:
A wireless communication circuit, comprising: a low noise amplifier which can switch a gain to a first gain or a second gain lower than the first gain, and amplifies and outputs, with a set gain, an RF signal; a first gain control amplifier which has a variable gain and amplifies and outputs the signal outputted from the low noise amplifier; a differential converter which has a variable gain and outputs a differential signal obtained by differential conversion on the signal outputted from the first gain control amplifier; a mixer circuit which outputs a signal obtained by mixing an oscillation signal and the differential signal; a filter which filters the signal outputted from the mixer circuit; a second gain control amplifier which has a variable gain, amplifies and outputs the signal outputted from the filter; a first control circuit which detects the output signal of the mixer circuit and controls the gains of the low noise amplifier and the first gain control amplifier such that a signal level of the output signal reaches a set reference level; and a second control circuit which controls the gain of the differential converter and the reference level of the first control circuit based on a signal level of the RF signal and a signal level of a disturbing wave included in the RF signal, and reduces the gain of the differential converter when the signal level of the RF signal is at least a specified level and the RF signal includes a disturbing wave of a predetermined level or higher, wherein an output of the low noise amplifier is connected with an input of the mixer circuit via the first gain control amplifier and the differential converter, and wherein the filter does not intervene between the output of the low noise amplifier and the input of the mixer circuit.