A multiplexer includes a filter (10) arranged between a common terminal and an input/output terminal (110) and configured to pass a radio frequency signal in a first frequency band, and a filter (20) arranged between the common terminal and an input/output terminal (120) and configured to pass a radio frequency signal in a second frequency band. The filter includes series arm circuits (31 and 32) connected in series, a series arm circuit (33) connected in parallel to the series arm circuit (32), and a parallel arm circuit. The series arm circuit (32) includes a series arm resonator that is an acoustic wave resonator. The series arm circuit (33) includes a switch arranged on a second path connecting nodes. In a CA mode, the switch is OFF. In a non-CA mode, the switch is ON.

A multiplexer includes a filter (10) arranged between a common terminal and an input/output terminal (110) and configured to pass a radio frequency signal in a first frequency band, and a filter (20) arranged between the common terminal and an input/output terminal (120) and configured to pass a radio frequency signal in a second frequency band. The filter includes series arm circuits (31 and 32) connected in series, a series arm circuit (33) connected in parallel to the series arm circuit (32), and a parallel arm circuit. The series arm circuit (32) includes a series arm resonator that is an acoustic wave resonator. The series arm circuit (33) includes a switch arranged on a second path connecting nodes. In a CA mode, the switch is OFF. In a non-CA mode, the switch is ON.

A disclosure of the present specification provides a terminal which uses a frequency band of a mobile satellite service for LTE/LTE-A. The terminal comprises: a first duplexer for separating a transmitted signal and a received signal in band 1 defined in long term evolution (LTE)/LTE-Advanced; a second duplexer for separating a transmitted signal and a received signal in new band 65 which was a mobile satellite service (MSS) band and now is allocated for the terrestrial service; and a selection switch for selecting one of the first duplexer and the second duplexer. Herein, when only band 1 is configured and used, only the first duplexer may be operated by the selection switch. In contrast, when new band 65 is configured and used, wherein the configured band does not overlap the range of band 1, and when new band 65 is configured and used, wherein the configured band overlaps the range of band 1 for carrier aggregation, only the second duplexer may be operated by the selection switch

In a switching circuit, an inductance of an inductor of a shunt circuit is such that off capacitance of a second switching device that is in the off state when a first switching device is in the on state is used to define, in the shunt circuit, a series resonance circuit with a desired resonant frequency. Therefore, the frequency of an unnecessary signal to be attenuated is set to the resonant frequency of the series resonance circuit. Thus, the switching circuit achieves improved isolation characteristics with other circuits by attenuating the unnecessary signal.

Methods and devices for radio frequency (RF) loopback for transceivers are described. A transceiver for communicating RF signals with a target device may transmit signals at a transmit frequency and receive signals at a (different) receive frequency. The transceiver may include a waveguide diplexer for separating and combining signals based on frequency. The transceiver may be configured to couple a loopback signal from a common port of the waveguide diplexer; the loopback signal may be based on a transmit signal. The transceiver may include a loopback translator to translate the loopback signal from the transmit frequency to the receive frequency and provide the translated loopback signal to a receiver used for receiving signals from the target device. The receiver may compare the translated loopback signal with a representation of the transmit signal to generate a compensation signal. A transmitter may use the compensation signal to adjust subsequent transmit signals.

A method and apparatus for estimating and compensating TX LO leakage using circuitry on a loopback path connecting the transmitter and receiver are provided. The TX LO leakage may be estimated by measuring the DC signal on the receiver, measuring the phase difference between the received LO signal and the receiver LO signal, and filtering LO harmonics that may arise from the use of non-linear mixers. The DC signal on the receiver may be measured by opening and closing the loopback path, or changing the gain of the loopback path, or flipping the phase of looped back TX signal. The method may be used in an initialization or tracking calibration scheme.

A transceiver and an operation method thereof are provided. The transceiver includes a transmitter and a receiver. The transmitter is configured to receive an output reference signal to provide an output signal to a signal channel. The receiver is coupled to the signal channel to receive a receiving reference signal to provide a receiving signal. The receiver includes a comparator unit and a signal adjusting unit. The comparator unit is configured to compare a first signal and a second signal to obtain the receiving signal. The signal adjusting unit is coupled between the output reference signal, the receiving reference signal and the comparator unit to adjust a voltage level of at least one of the output reference signal and the receiving reference signal to obtain the first signal and the second signal.

A radio transceiver circuit for FDD communication is disclosed. It comprises a transmitter for FDD signal transmission in a first frequency band, a first receiver for FDD signal reception in a second frequency band, separate from the first frequency band, and a duplexer. An output port of the transmitter is operatively connected to a first port of the duplexer for transmitting, through the duplexer, signals in said first frequency band. An input port of the first receiver is operatively connected to a second port of the duplexer for receiving, through the duplexer, signals in said second frequency band. The radio transceiver circuit comprises a second receiver, separate from the first receiver, for reception in said first frequency band. An input port of the second receiver is operatively connected to said first port of the duplexer for receiving, through the duplexer, signals in said first frequency band. A related radio communication apparatus is also disclosed.

A radio transceiver circuit for FDD communication is disclosed. It comprises a transmitter for FDD signal transmission in a first frequency band, a first receiver for FDD signal reception in a second frequency band, separate from the first frequency band, and a duplexer. An output port of the transmitter is operatively connected to a first port of the duplexer for transmitting, through the duplexer, signals in said first frequency band. An input port of the first receiver is operatively connected to a second port of the duplexer for receiving, through the duplexer, signals in said second frequency band. The radio transceiver circuit comprises a second receiver, separate from the first receiver, for reception in said first frequency band. An input port of the second receiver is operatively connected to said first port of the duplexer for receiving, through the duplexer, signals in said first frequency band. A related radio communication apparatus is also disclosed.

According to an example embodiment of the inventive concept, a master unit for time division duplex includes a passive signal distributor for outputting, to a second node, a downlink signal input through a first node, and outputting, to the first node, an uplink signal input through a third node, and a signal transceiver for transmitting, to a remote unit, the downlink signal input from the second node, and outputting, to the third node, an uplink amplification signal received from the remote unit.