Front-end circuit and impedance adjustment method

摘要

A front-end circuit includes an RFIC, an antenna, N duplexers, N variable impedance adjustment circuits, a switch for selecting any two of the N variable impedance adjustment circuits, and a control unit which receives a control signal from the RFIC, where 2≦N. The control unit executes switching operations of the N variable impedance adjustment circuits and the switch in accordance with control information. The control signal indicates to 1) control the switch to select two variable impedance adjustment circuits corresponding to a p-th frequency band and a q-th frequency band respectively, 2) control a variable impedance adjustment circuit corresponding to the p-th frequency band to increase input impedance in the q-th frequency band as viewed from the antenna side and 3) control a variable impedance adjustment circuit corresponding to the q-th frequency band to increase input impedance in the p-th frequency band as viewed from the side.

主权项

1. A front-end circuit comprising:
a radio frequency integrated circuit; a transmission and reception antenna; N duplexers in between the radio frequency integrated circuit and the transmission and reception antenna, an i-th duplexer of the N duplexers being for transmission and reception of signals in an i-th frequency band of predetermined first to N-th frequency bands, where N is a predetermined integer greater than or equal to 2 and i is an integer satisfying 1≦i≦N; N variable impedance adjustment circuits, an i-th variable impedance adjustment circuit of the N variable impedance adjustment circuits being connected to the i-th duplexer; a switch which is connected to the transmission and reception antenna and which selects any two of the N variable impedance adjustment circuits; and a control circuit which receives a control signal from the radio frequency integrated circuit, wherein the control circuit executes switching operations of the N variable impedance adjustment circuits and the switch in accordance with control information indicated by the control signal, and the control signal indicates to, when a p-th frequency band and a q-th frequency band of the predetermined first to N-th frequency bands are selected, where p is an integer satisfying 1≦p≦N, q is an integer satisfying 1≦q≦N and p≠q:
control the switch to select two variable impedance adjustment circuits corresponding to the p-th frequency band and the q-th frequency band respectively;control a selected variable impedance adjustment circuit corresponding to the p-th frequency band to increase input impedance in the q-th frequency band as viewed from the transmission and reception antenna side; andcontrol a selected variable impedance adjustment circuit corresponding to the q-th frequency band to increase input impedance in the p-th frequency band as viewed from the transmission and reception antenna side.