The present disclosure may include, for example, a tunable capacitor having a decoder for generating a plurality of control signals, and an array of tunable switched capacitors comprising a plurality of fixed capacitors coupled to a plurality of switches. The plurality of switches can be controlled by the plurality of control signals to manage a tunable range of reactance of the array of tunable switched capacitors. Additionally, the array of tunable switched capacitors is adapted to have non-uniform quality (Q) factors. Additional embodiments are disclosed.

Provided herein are apparatus and methods for reconfigurable directional couplers in an RF transceiver. Reconfigurable directional couplers can be reconfigured and designed to provide high directivity using configurable capacitors to effect a mutual coupling and using lumped components or delay lines to effect a phase shift. Depending on the embodiment, the reconfigurable directional coupler can include capacitors, inductors, and switching components. The coupler can be designed for multi-band operation with an adjustable coupling factor conducive to semiconductor process integration. The coupler can have variable phase shifters to achieve a desired level of directivity in the coupler.

A balun includes a first winding which has a first terminal coupled to an input, and a second terminal coupled to a reference potential terminal. The balun includes a second winding magnetically coupled to the first winding. The second winding has a first terminal coupled to a first differential output, a second terminal coupled to a second differential output, and a tap coupled to the reference potential terminal. The balun includes a first capacitor which has a first terminal coupled to the first winding and a second terminal coupled to the second winding. The balun includes a third winding which has a first terminal coupled to the reference potential terminal and a floating second terminal. The balun includes a second capacitor which has a first terminal coupled to the third winding and a second terminal coupled to the second winding.

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 comprising a upper terminal portion coupled to a lower terminal portion through a variable capacitance. In another example, a method includes positioning the charge terminal at a defined height over a lossy conducting medium; adjusting a phase delay () of a feed network connected to the charge a terminal to match a wave tilt angle () corresponding to a complex Brewster angle of incidence (.sub.i,B) associated with the lossy conducting medium; adjusting the variable capacitance based upon an image ground plane impedance (Z.sub.in) associated with the lossy conducting medium; and exciting the charge terminal with an excitation voltage via the feed network. The excitation voltage can establish an electric field that couples into a guided surface waveguide mode along a surface of the lossy conducting medium.

A switched-capacitor circuit comprising a differential operational amplifier and a feedback circuit is described. In some embodiments, the feedback circuit may be configured to provide a reference voltage that is insensitive to temperature and/or process variations. In some embodiments, the feedback circuit may be configured to mitigate the time delay associated with one or more capacitors of the switched-capacitor circuit. The switched-capacitor circuit may be controlled by a pair of control signals. During a first phase, one or more capacitors may be charged, or discharged, through an input signal. During a second phase, the electric charge of the one or more capacitors may be retained.

An AC coupler for transmitting high-frequency components of a wideband signal includes a signal conductor and a shielding structure arranged as a transmission line. The signal conductor includes a conductive element and a capacitor configured to block direct current (DC) components of the wideband signal while transmitting high-frequency alternating current (AC) components of the wideband signal. The shielding structure is configured for conducting at least the AC components of the wideband signal while confining electric fields and currents in the shielding structure substantially to a region proximate to the signal conductor. The shielding structure has a width substantially greater than a width of the signal conductor. The difference between the shielding structure width and the signal conductor width may be substantially greater than an offset distance between the signal conductor and the shielding structure.

A high frequency band pass filter with a coupled surface mount transition is provided, including a filter substrate, circuit connection elements defining input and an output elements provided on a surface of the filter substrate, electronic filter components provided on the first surface of the filter substrate, and impedance matching structures provided on the first surface of the filter substrate between the electronic filter components and the respective input and output elements. Signal connection structures are provided on an opposed surface of the filter substrate, in locations that positionally correspond to respective positions of the input and output elements. The respective signal connection elements are capacitively coupled, through a thickness direction of the filter substrate, to a respective one of the input and output elements on the opposed surface of the filter substrate without the presence of any vertical conductive structures within the filter substrate at the input and the output elements.

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.

Data communication having improved electromagnetic interference (EMI) rejection when communicating through a coaxial cable is provided by using differential transmission and/or reception through a common-mode choke and a dissipative element resulting in extremely low radiated emissions and high immunity to external radiation interference in a low-cost way.

Provided herein are apparatus and methods for reconfigurable directional couplers in an RF transceiver. Reconfigurable directional couplers can be reconfigured and designed to provide high directivity using configurable capacitors to effect a mutual coupling and using lumped components or delay lines to effect a phase shift. Depending on the embodiment, the reconfigurable directional coupler can include capacitors, inductors, and switching components. The coupler can be designed for multi-band operation with an adjustable coupling factor conducive to semiconductor process integration. The coupler can have configurable coupling capacitors and phase shifters.