Various examples are provided for enhanced guided surface waveguide probes, systems and methods. In one example, a guided surface waveguide probe includes a charge terminal elevated over a lossy conducting medium, the charge terminal includes a upper terminal portion coupled to a lower terminal portion through a variable capacitance. A feed network is configured to couple an excitation source to the charge terminal and provide a voltage to the charge terminal with a phase delay that matches a wave tilt angle associated with a complex Brewster angle of incidence associated with the lossy conducting medium. In another example a method includes positioning a charge terminal over a lossy conducting medium, where the charge terminal includes an upper terminal portion coupled to a lower terminal portion through a variable capacitance. The method also includes adjusting a phase delay of a feed network to match a wave tilt angle associated with a complex Brewster angle of incidence associated with the lossy conducting medium, where the feed network is configured to couple an excitation source to the charge terminal and provide a voltage to the charge terminal with the phase delay.

A filter circuit includes a serial arm connected between ports (P1-P2), a parallel arm having a resonator connected in series between ports (P1-P3), and another parallel arm having another resonator connected in series between ports (P2-P3). The serial arm includes a switching circuit, and the switching circuit connects an inductor or a capacitor to the serial arm in series using a switch.

A wide band radio frequency (RF) circulator is presented. The RF circulator includes at least one stage having four ports configured to circulate an input RF signal from a first port to a second port while isolating a third port, from the second port to the third port while isolating the first port, and from the third port to the first port while isolating the first port, wherein the fourth port is grounded; and wherein the at least one stage includes at least a pair of couplers connected via a delay line, wherein each coupler includes a main transmission line and a coupling transmission line disposed on distinct dielectric layers.

A high frequency circuit includes a transistor having an input electrode that inputs a high frequency signal and an output electrode that outputs the high frequency signal, a transmission line that is connected to any one of the input electrode and the output electrode, and transmits the high frequency signal, a coupling line electrically separated from the transmission line and electromagnetically coupled to the transmission line, and a resonance including an inductor and a capacitor connected in series between a first end of the coupling line and a reference potential. A resonance frequency of the resonance circuit is lower than an operating frequency band of the high frequency circuit.

A high frequency circuit includes a transistor having an input electrode that inputs a high frequency signal and an output electrode that outputs the high frequency signal, a transmission line that is connected to any one of the input electrode and the output electrode, and transmits the high frequency signal, a coupling line electrically separated from the transmission line and electromagnetically coupled to the transmission line, and a resonance including an inductor and a capacitor connected in series between a first end of the coupling line and a reference potential. A resonance frequency of the resonance circuit is lower than an operating frequency band of the high frequency circuit.

Illustrative embodiments of reconfigurable microwave filters, as well as associated systems and methods, are disclosed. In at least one illustrative embodiment, a reconfigurable microwave filter may comprise a plurality of cavity resonators on a common substrate and a plurality of control circuits each configured to control a resonant frequency of one of the plurality of cavity resonators. The reconfigurable microwave filter may also comprise a plurality of feedback circuits each configured to generate a feedback signal that is indicative of the resonant frequency of one of the plurality of cavity resonators and to transmit the feedback signal to one of the plurality of control circuits.

A signal cancelling duplexer is provided. Duplexers of the invention add equal amounts of a transmission signal and an out-of-phase component of the same transmission signal at the receiver, so that both signals cancel. Duplexers of the invention can be switched between multiple channels by changing switch settings within the duplexer. RF transceivers including a power amplifier, receiver amplifier, and the signal cancelling duplexer are also provided.

A signal cancelling duplexer is provided. Duplexers of the invention add equal amounts of a transmission signal and an out-of-phase component of the same transmission signal at the receiver, so that both signals cancel. Duplexers of the invention can be switched between multiple channels by changing switch settings within the duplexer. RF transceivers including a power amplifier, receiver amplifier, and the signal cancelling duplexer are also provided.

A transformer simulating circuit includes a primary side, a secondary side, a first coupling capacitor, and a second coupling capacitor. The primary side includes a primary core-loss resistor, a primary intra-winding capacitor, and a magnetizing inductor connected in parallel, and includes a primary leakage inductor module connected between a primary winding and the primary intra-winding capacitor, and a primary winding resistor connected to the primary leakage inductor module. The secondary side includes a secondary leakage inductor module connected between a secondary winding and a secondary intra-winding capacitor, and a secondary winding resistor connected to the secondary leakage inductor module. The first coupling capacitor and the second coupling capacitor are connected between the primary side and the secondary side. Therefore, a simulated frequency response of the transformer simulating circuit is closer to a measured frequency response of a real transformer.

A resonator comprising: an insulating layer having a top side and a bottom side; a conductive layer mounted to the bottom side of the insulating layer; a radio frequency (RF) connector designed to be connected to a transceiver, wherein the RF connector is mounted to the top side of the insulating layer, and wherein the RF connector has a center conductor that is electrically connected to the conductive layer; and means for attaching the conductive layer to a conductive structure, wherein the conductive structure has a dimension of at least one-half wavelength of an operating frequency of the transceiver such that when the resonator is attached to the transceiver and to the conductive structure the conductive structure functions as an antenna.