An electronic device may be provided with a first antenna fed by a first path and a second antenna fed by a second path. A first coupler may be disposed on the first path, a second coupler may be disposed on the second path, and a feedback path may couple the couplers to a receiver. A low-pass filter may be disposed on the second path. The first antenna may transmit signals in a low band. Some of the signals may couple onto the second antenna. The second coupler may pass the coupled signals to the receiver. Control circuitry may generate a scattering parameter value characterizing the coupling of the signals from the first antenna onto the second antenna. The scattering parameter value may be used to determine when to switch the first antenna out of use and the second antenna into use for covering the low band.

A printed circuit board (PCB) assembly supports selecting alternate printed antenna geometries of an antenna by selectively placing common PCB components (for example, zero-ohm resistors) on the PCB. The desired zero-ohm resistors may be placed using automated part placement equipment commonly used to place surface mount components. The configurable antenna comprises at least one antenna section having a plurality of antenna components. Zero-ohm resistors are selectively placed in series along the antenna section to couple the desired conductor components when manufacturing the PCB assembly. With some embodiments, a configurable antenna includes a low frequency antenna section that may be selectively coupled with a high frequency antenna section antenna through one or more zero-ohm resistors, where each antenna section has a plurality of antenna components. With this approach, a common printed circuit board may be used to support a plurality of antenna variations spanning different frequency bands.

Antenna elements for multiband antennas are disclosed. A multiband antenna is configured to operate in at least two frequency bands. The antenna element is configured to receive a signal from an unbalanced signal feed and comprises: a stalk configured to be mounted on a ground plane; at least one radiating element extending from the stalk; a balun configured to receive and convert an unbalanced signal from an unbalanced signal feed to a balanced signal and to supply the balanced signal to the at least one radiating element; and at least one resonance suppression filter. The at least one resonance suppression filter comprises an inductive component and a capacitive component arranged in parallel, and in some embodiments a resistive component in series with the inductive component.

A user equipment (UE) is provided that includes an antenna switch array for demultiplexing a reference signal sequentially to each antenna in a plurality of antennas. While the antenna switch array selects an antenna, the UE measures a reflection coefficient for the antenna. The UE then tunes the antenna responsive to the reflection coefficient measurement.

A printed circuit board (PCB) assembly supports selecting alternate printed antenna geometries of an antenna by selectively placing common PCB components (for example, zero-ohm resistors) on the PCB. The desired zero-ohm resistors may be placed using automated part placement equipment commonly used to place surface mount components. The configurable antenna comprises at least one antenna section having a plurality of antenna components. Zero-ohm resistors are selectively placed in series along the antenna section to couple the desired conductor components when manufacturing the PCB assembly. With some embodiments, a configurable antenna includes a low frequency antenna section that may be selectively coupled with a high frequency antenna section antenna through one or more zero-ohm resistors, where each antenna section has a plurality of antenna components. With this approach, a common printed circuit board may be used to support a plurality of antenna variations spanning different frequency bands.

A 5.sup.th generation (5G) or pre-5G communication system for supporting a higher data transfer rate than 4.sup.th generation (4G) communication systems such as long term evolution (LTE). An apparatus for radiating a signal in a wireless communication system may include: a power amplifier; a sub array including a plurality of antenna elements; and filter circuitry configured to transfer an output signal of the power amplifier to the sub array and including an input end and an output end. The filter circuitry may include: a first impedance matching circuit connected with the power amplifier; a second impedance matching circuit connected with the sub array; and a plurality of filters coupled in parallel to each of the first impedance matching circuit and the second impedance matching circuit. An impedance of the input end is matched with a sum of an impedance of the plurality of filters and an impedance of the first impedance matching circuit. An impedance of the output end is matched with a sum of the impedance of the plurality of filters and an impedance of the second impedance matching circuit.

A 5.sup.th generation (5G) or pre-5G communication system for supporting a higher data transfer rate than 4.sup.th generation (4G) communication systems such as long term evolution (LTE). An apparatus for radiating a signal in a wireless communication system may include: a power amplifier; a sub array including a plurality of antenna elements; and filter circuitry configured to transfer an output signal of the power amplifier to the sub array and including an input end and an output end. The filter circuitry may include: a first impedance matching circuit connected with the power amplifier; a second impedance matching circuit connected with the sub array; and a plurality of filters coupled in parallel to each of the first impedance matching circuit and the second impedance matching circuit. An impedance of the input end is matched with a sum of an impedance of the plurality of filters and an impedance of the first impedance matching circuit. An impedance of the output end is matched with a sum of the impedance of the plurality of filters and an impedance of the second impedance matching circuit.

An apparatus, including: an antenna interface, comprising: a first transformer including a first transmission line coupled to a second transmission line, wherein the first transmission line includes first and second ends configured to couple to a first communication device and a reference potential electrode, respectively, and wherein the second transmission line includes first and second ends configured to couple to an antenna and a second communication device, respectively; and a second transformer including a third transmission line coupled to a fourth transmission line, wherein the third transmission line includes first and second ends configured to couple to the first communication device and the reference potential electrode, respectively, and wherein the fourth transmission line includes first and second ends configured to couple to the second communication device and a ballast load, respectively.

An apparatus, including: an antenna interface, comprising: a first transformer including a first transmission line coupled to a second transmission line, wherein the first transmission line includes first and second ends configured to couple to a first communication device and a reference potential electrode, respectively, and wherein the second transmission line includes first and second ends configured to couple to an antenna and a second communication device, respectively; and a second transformer including a third transmission line coupled to a fourth transmission line, wherein the third transmission line includes first and second ends configured to couple to the first communication device and the reference potential electrode, respectively, and wherein the fourth transmission line includes first and second ends configured to couple to the second communication device and a ballast load, respectively.

Systems and methods for tuning multiplexer filters are disclosed. In one aspect, a multiplexer includes a first filter coupled to a common node, the first filter configured to pass a first band, a second filter coupled to the common node, the second filter configured to pass a second band, and at least one electrical component configured to generate a notch at a frequency between the first band and the second band.