A differential double balanced duplexer (dDBD) includes a transmitter and a first balun are coupled to a first impedance tuner that produces a first impedance that blocks received signals at a first frequency range from travelling across the first balun and into the transmitter, and a second impedance that passes transmitted signals at a second frequency range to travel across the first balun to the antenna. The dDBD also includes a receiver and a second balun coupled to a second impedance tuner that produces a first impedance that allows the received signals at the first frequency range to travel across the second balun and into the receiver, and a second impedance that blocks the transmitted signals at the second frequency range from travelling across the second balun and into the receiver. As such, the dDBD allows for increased isolation and decreased insertion loss.

An apparatus for communicating across an isolation barrier includes a differential pair of input terminals. The apparatus includes a bandpass filter circuit configured to receive a received signal on the differential pair of input terminals and to provide a received differential signal on a differential pair of nodes. The apparatus includes a demodulator directly coupled to the bandpass filter circuit and configured to directly demodulate the received differential signal on the differential pair of nodes to provide a demodulated received signal.

A filter includes a first input/output terminal, a second input/output terminal, a third input/output terminal, a fourth input/output terminal, a first stage resonant circuit connected between the first input/output terminal and the second input/output terminal, at least one intermediate stage resonant circuit, and a final stage resonant circuit connected between the third input/output terminal and the fourth input/output terminal. The first stage resonant circuit and the final stage resonant circuit each include an inductor. The at least one intermediate stage resonant circuit includes an inductor and a capacitor connected in parallel to each other, and one end of the inductor and one end of the capacitor connected in parallel to the inductor are connected to a reference potential.

A balun for a power amplifier is disclosed. In one aspect, a balun based on acoustic coupled resonator filters (CRFs) has a 4:1 impedance ratio between an unbalanced side and a balanced side. As such, the balun is well suited for use between power amplifiers and filters. The 4:1 ratio is achieved through one or more design options, including material selection, material thickness selection, series versus shunt inductor positions, CRF topology selection, or the like. The overall size is reduced relative to non-CRF baluns providing more room in a mobile device for other components or batteries.

Provided are a structure having excellent shielding performance against electromagnetic waves in a frequency band of several tens of GHz, and a composition. Further, provided is a method for manufacturing a structure which makes it possible to easily manufacture a structure having excellent shielding performance against electromagnetic waves in a frequency band of several tens of GHz. The structure includes a substrate, a plurality of passive elements disposed on the substrate, and an electromagnetic wave absorbing film positioned at least in a region between the plurality of passive elements disposed on the substrate. The passive element is selected from the group consisting of an inductor and a balun. The electromagnetic wave absorbing film contains magnetic particles. In a case where a real part of a complex relative magnetic permeability of the electromagnetic wave absorbing film is defined as and a complex part of the complex relative magnetic permeability of the electromagnetic wave absorbing film is defined as , the complex part of the complex relative magnetic permeability of the electromagnetic wave absorbing film satisfies any one of requirements 1 to 3. Requirement 1: at a frequency of 28 GHz is 0.1 to 10, Requirement 2: at a frequency of 47 GHz is 0.1 to 5, and Requirement 3: at a frequency of 60 GHz is 0.1 to 2.

In an embodiment, a circuit includes a first input terminal configured to be coupled to a first terminal of a first capacitor, a second input terminal configured to be coupled to a second terminal of the first capacitor, a balun including a primary inductor and a secondary inductor, and a second capacitor. The primary inductor includes a first terminal coupled to the first input terminal, a second terminal coupled to the second input terminal, a first inductive portion coupled between the first terminal of the primary inductor and a first intermediate terminal, a second inductive portion coupled between the second terminal of the primary inductor and a second intermediate terminal, and a third inductive portion coupled between the first and second intermediate terminals. The secondary inductor includes a first terminal coupled to a ground terminal. The second capacitor is coupled between the first and second intermediate terminals.

Apparatus and methods for radio frequency (RF) signal splitting are disclosed. In certain embodiments, a front-end system includes a filter that filters an RF receive signal to generate a differential filtered RF signal between a first output and a second output, a first low noise amplifier (LNA) that generates a first amplified RF signal by amplifying a first component of the differential filtered RF signal received from the first output, a second LNA that generates a second amplified RF signal by amplifying a second component of the differential filtered RF signal received from the second output, a first multi-throw switch that receives the first amplified RF signal, and a second multi-throw switch that receives the second amplified RF signal.