An alternation voltage- or current generator comprises a first switch driving output network whose frequency can be tuned. The tunable network comprises a first Inductor that is coupled with a first capacitor. A second inductor and/or at least a second capacitor and/or at least a series circuit of a third inductor and a third capacitor which is coupled via at a second switch to the network. The second switch is controlled by a controlled delay (PWM) which is synchronized by a sign change of current and/or voltage in the network.

A system that incorporates the subject disclosure may include, for example, a circuit for receiving a request to initiate a first multiple-input and multiple-output (MIMO) communication session and a second MIMO communication session, and configuring a first antenna configuration and a second antenna configuration to enable the first MIMO communication session and the second MIMO communication session. The first MIMO communication session shares spectrum from the first antenna configuration and the second antenna configuration, and the second MIMO communication session utilizes spectrum from the second antenna configuration that differs from the shared spectrum. Other embodiments are disclosed.

A system that incorporates the subject disclosure may include, for example, a circuit for initiating a first multiple-input and multiple-output (MIMO) communication session with a primary base station, and initiating a second MIMO communication session with a first secondary base station of a plurality of secondary base stations without terminating the first MIMO communication session with the primary base station. The primary base station can include a primary antenna system having a first communication range, while each of the plurality of secondary base stations can include a secondary antenna system having a second communication range that is a subset of the first communication range of the primary antenna system. The plurality of secondary base stations can correspond to a plurality of small cell sites distributed within the first communication range of the primary base station. Other embodiments are disclosed.

A system that incorporates the subject disclosure may include, for example, a circuit for determining a magnitude difference between a first signal supplied to an antenna and a second signal radiated by the antenna, determining a phase difference between the first signal supplied to the antenna and the second signal radiated by the antenna, measuring a change in reactance of an antenna, detecting an offset in an operating frequency of the antenna based on one of the magnitude difference, the phase difference, the change in reactance, or any combination thereof, and adjusting a resonant frequency of the antenna to mitigate the offset in the operating frequency of the antenna. Other embodiments are disclosed.

A communication device that incorporates the subject disclosure may include, for example, a conductive cover, an antenna structure, and a circuit. The antenna structure can comprise a first portion of the conductive cover having a first slot formed therein. The first portion can form a first antenna element for converting between first electromagnetic signals and first electrical signals. The first slot can define a shape of a trade dress design in the conductive cover. The circuit can be communicatively coupled to first edges of the first slot to define a first port. The circuit can perform operations comprising transmitting the first electronic signals into the first antenna element. Other embodiments are disclosed.