Patent ID: 7756488

Claim:
A high-frequency switch module comprising: a FET switch including a transmission input port arranged to receive a transmission signal, a reception output port arranged to output a reception signal, and an antenna port arranged to output the transmission signal to an antenna or to receive the reception signal from the antenna, the FET switch being arranged to connect the antenna port to the transmission input port or the reception output port by switching between the transmission input port and the reception output port; and a filter connected to the transmission input port and arranged to attenuate a higher-order harmonic of the transmission signal; wherein the filter includes a first low-pass filter and a second low-pass filter connected in series, the first low-pass filter including a transmission line and a stop band that includes a frequency of a second-order harmonic of the transmission signal, the second low-pass filter including a stop band that includes a frequency of a third-order harmonic of the transmission signal; a phase setting element including a transmission line is provided between the transmission input port of the FET switch and the filter; and an electrical length of the transmission line of the phase setting element is less than one fourth of a wavelength of the second-order harmonic and is set such that an impedance of a filter side viewed from the FET switch with respect to both the second-order harmonic and the third-order harmonic of the transmission signal is set to a predetermined impedance by shifting the impedance clockwise from infinity on a Smith chart to cause a phase change, such that an absolute value of an impedance with respect to a fundamental of the transmission signal does not change as compared to a state in which the phase setting element is not provided, and the impedance of the filter side viewed from the FET switch with respect to one of the first and second low-pass filters that is disposed on a side farthest from the FET switch is adjusted to be the predetermined impedance.