A filter includes a first resonance circuit including a first capacitor and a first inductor connected in parallel between a ground terminal and a first node electrically connected to a first signal terminal not through any capacitor, no inductor being connected in series with the first capacitor between the first node and the ground terminal, a second resonance circuit including a second capacitor and a second inductor connected in parallel between the ground terminal and a second node electrically connected to a second signal terminal not through any capacitor, and a third resonance circuit including a third capacitor and a third inductor connected in parallel between a third node, located in a path through which a high-frequency signal is transmitted between the first and second nodes, and the ground terminal, and a first series inductor connected in series with the third capacitor between the third node and the ground terminal.

A filter includes a first resonance circuit including a first capacitor and a first inductor connected in parallel between a ground terminal and a first node electrically connected to a first signal terminal not through any capacitor, no inductor being connected in series with the first capacitor between the first node and the ground terminal, a second resonance circuit including a second capacitor and a second inductor connected in parallel between the ground terminal and a second node electrically connected to a second signal terminal not through any capacitor, and a third resonance circuit including a third capacitor and a third inductor connected in parallel between a third node, located in a path through which a high-frequency signal is transmitted between the first and second nodes, and the ground terminal, and a first series inductor connected in series with the third capacitor between the third node and the ground terminal.

RF duplexing and methods of operating the same are described herein. In one embodiment, an RF duplexing system may include a control circuit and a duplexer with a first tunable RF filter and second tunable RF filter. The control circuit is operable in a full duplexing transmission mode and a half duplexing transmission mode. The control circuit tunes the first tunable RF filter in the full duplexing transmission mode so that the first tunable RF filter defines a transmission passband and tune the second tunable RF filter so that the second tunable RF filter defines a receive passband. Also, the control circuit tunes one of the tunable RF filters so that the tunable RF filter defines the passband while the other tunable RF filter enhances the passband. In this manner, the tunable RF filters in the duplexer are both utilized to get better performance during the half duplexing mode.

A high-selectivity low-loss duplexing system includes a first duplexer having a first port, a second port, a transmit port and a receive port. A second duplexer has a third port, a fourth port, an inverted transmit port and the receive port. The first port and the third port are connected to an antenna by a balun. The transmit port and the inverted transmit port are connected to at least one power amplifier. The receive port is connected to a low noise amplifier. A phase shifter includes a lattice filter configured to short the second port to the third port and the fourth port to the first port at a receive frequency, and short the second port to the first port and the fourth port to the third port at a transmit frequency.

Embodiments of the present invention provide an apparatus and a method for interference cancellation. The apparatus includes: a splitter, configured to acquire a first transmit signal and a second transmit signal; a first circulator, configured to transmit the first transmit signal to an antenna and to send a to-be-processed signal to a combiner, where the to-be-processed signal includes a receive signal component and a self-interference signal component, the self-interference signal component corresponds to an interference signal generated due to that the antenna reflects the first transmit signal; a second circulator, configured to: transmit the second transmit signal to an equivalent load, and acquire a reference signal generated due to that the equivalent load reflects the second transmit signal, where an impedance of the equivalent load corresponds to an impedance of the antenna; and a combiner, configured to cancel the self-interference signal component according to the reference signal.

Embodiments of the present invention provide an apparatus and a method for interference cancellation. The apparatus includes: a splitter, configured to acquire a first transmit signal and a second transmit signal; a first circulator, configured to transmit the first transmit signal to an antenna and to send a to-be-processed signal to a combiner, where the to-be-processed signal includes a receive signal component and a self-interference signal component, the self-interference signal component corresponds to an interference signal generated due to that the antenna reflects the first transmit signal; a second circulator, configured to: transmit the second transmit signal to an equivalent load, and acquire a reference signal generated due to that the equivalent load reflects the second transmit signal, where an impedance of the equivalent load corresponds to an impedance of the antenna; and a combiner, configured to cancel the self-interference signal component according to the reference signal.

A two-port tunable or reconfigurable network having a filter transfer function may include: a network input port; a network output port; a hybrid coupler having a hybrid input port, a hybrid isolated port, a hybrid through port, and a hybrid coupled port; a first internal two-port network connected between the network input port and the hybrid input port; a second internal two-port network connected between the network output port and the hybrid isolated port; and a third internal two-port network connected between the hybrid through port and the hybrid coupled port. At least one of the first internal two-port network, the second internal two-port network, the third internal two-port network, and the hybrid coupler may be tunable or reconfigurable in response to an electrical signal or a user-operated control in a way that tunes or reconfigures the filter transfer function of the two-port tunable or reconfigurable network. A two-port tunable or reconfigurable network having a filter transfer function may include: a network input port; a network output port; a hybrid coupler having a hybrid input port, a hybrid isolated port, a hybrid through port, and a hybrid coupled port; a first load; a second load; a first internal two-port network connected between the between the first load and the hybrid through port; and a second internal two-port network connected between the between the second load and the hybrid coupled port. At least one of the first internal two-port network, the second internal two-port network, the hybrid coupler, the first load, and the second load may be tunable or reconfigurable in response to an electrical signal or a user-operated control in a way that tunes or reconfigures the filter transfer function of the two-port tunable or reconfigurable network.

A two-port tunable or reconfigurable network having a filter transfer function may include: a network input port; a network output port; a hybrid coupler having a hybrid input port, a hybrid isolated port, a hybrid through port, and a hybrid coupled port; a first internal two-port network connected between the network input port and the hybrid input port; a second internal two-port network connected between the network output port and the hybrid isolated port; and a third internal two-port network connected between the hybrid through port and the hybrid coupled port. At least one of the first internal two-port network, the second internal two-port network, the third internal two-port network, and the hybrid coupler may be tunable or reconfigurable in response to an electrical signal or a user-operated control in a way that tunes or reconfigures the filter transfer function of the two-port tunable or reconfigurable network. A two-port tunable or reconfigurable network having a filter transfer function may include: a network input port; a network output port; a hybrid coupler having a hybrid input port, a hybrid isolated port, a hybrid through port, and a hybrid coupled port; a first load; a second load; a first internal two-port network connected between the between the first load and the hybrid through port; and a second internal two-port network connected between the between the second load and the hybrid coupled port. At least one of the first internal two-port network, the second internal two-port network, the hybrid coupler, the first load, and the second load may be tunable or reconfigurable in response to an electrical signal or a user-operated control in a way that tunes or reconfigures the filter transfer function of the two-port tunable or reconfigurable network.

A radio-frequency module includes power amplifiers on a major surface of a module substrate, a transmit filter coupled to an output terminal of the power amplifier to pass a transmit signal in a communication band A, a transmit filter coupled to an output terminal of the power amplifier to pass a transmit signal in a communication band C, a transmit filter coupled to an output terminal of the power amplifier to pass a transmit signal in a communication band E, a resin member covering the major surface, a metal shield layer covering a surface of the resin member, and a metal shield plate on the major surface between the power amplifier and the power amplifier and also between the power amplifier and the power amplifier. The metal shield plate is in contact with a first ground electrode at the major surface and also with the metal shield layer.

A high-frequency module includes: a module board that has main surfaces which are opposed to each other; a plurality of high-frequency components that are arranged on at least one of the main surfaces; a resin member that covers at least one of the main surfaces and has a plurality of side surfaces along an outer edge of the module board; and a shield electrode layer that covers some of the side surfaces without covering other side surfaces.