A power feed circuit for a circularly polarized antenna includes a synthesizing-distributing unit and a phase shift unit. The synthesizing-distributing unit distributes input signals to two paths with the same phase and same amplitude. The phase shift unit has two phase shift circuits connected respectively between the two paths distributed by the synthesizing-distributing unit and two feed points of a circularly polarized antenna. The phase shift unit outputs signals whose phase difference is 90° to the two feed points and of the circularly polarized antenna.

A power feed circuit for a circularly polarized antenna includes a synthesizing-distributing unit and a phase shift unit. The synthesizing-distributing unit distributes input signals to two paths with the same phase and same amplitude. The phase shift unit has two phase shift circuits connected respectively between the two paths distributed by the synthesizing-distributing unit and two feed points of a circularly polarized antenna. The phase shift unit outputs signals whose phase difference is 90° to the two feed points and of the circularly polarized antenna.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

A combiner/splitter is disclosed having a first trifilar transformer having a first outer transmission element electrically connected between a first port node and a first intermediate node. A second trifilar transformer has a second outer transmission element electrically connected between the first intermediate node and a second port node. A third trifilar transformer has a third outer transmission element electrically connected between the first port node and a second intermediate node. A fourth trifilar transformer has a fourth outer transmission element electrically connected between the second intermediate node and a third port node.

A balun includes: first wiring that has a first end connected to a first balanced line and a second end connected to a second balanced line; second wiring that has a grounded first end and a second end; third wiring that has a first end connected to the second end of the second wiring and a second end connected to an unbalanced line and is electromagnetically coupled to the second wiring; a first capacitor that has a first end connected to the first end of the third wiring and a grounded second end; and a second capacitor that has a first end connected to the second end of the third wiring and a grounded second end. The first wiring is electromagnetically coupled to at least one of the second wiring and the third wiring.

A directional coupler (2) includes a main line (11), a sub-line (12), a variable terminator (13), and a variable filter circuit (15). The variable terminator (13) is a variable impedance circuit that terminates one end portion of the sub-line (12). The variable filter circuit (15) is connected to the other end portion of the sub-line (12). The variable filter circuit (15) may include a filter, a bypass path, and a switch which is connected to at least one of the filter and the bypass path.

A Wilkinson power combiner (202) is described that includes a high-pass, HP, frequency circuit (500, 550), wherein the HP frequency circuit (500, 550) comprises at least one of: (i) one input port (510) coupled to at least two output ports (512, 514) via at least two paths; and an input shunt inductor (520) coupling the input port (510) to ground; wherein the one input port (510) is coupled to the at least two output ports (512, 514) via respective series capacitances (230, 238) on the at least two paths, which in cooperation with the input shunt inductor (520) forms a first HP frequency circuit; and (ii) at least one resistor (554, 528)-inductor (552, 524), R-L isolation circuit (500, 550) configured to couple the at least two output ports (512, 514) that forms a second HP frequency circuit.

A directional coupler includes a main line through which a signal is transmitted, first and second sub-lines that are selectively coupled to the main line, and a common output port that outputs a detection signal generated by the signal transmitted through the main line, wherein a first degree of coupling between the main line and the first sub-line is different than a second degree of coupling between the main line and the second sub-line.

Apparatus and methods for quadrature combined Doherty amplifiers are provided herein. In certain embodiments, a separator is used to separate a radio frequency (RF) input signal into a plurality of input signal components that are amplified by a pair of Doherty amplifiers operating in quadrature. Additionally, a combiner is used to combine a plurality of output signal components generated by the pair of Doherty amplifiers, thereby generating an RF output signal exhibiting quadrature balancing.