A semiconductor chip includes a first wireless communication circuit, a local oscillator (LO) buffer, and an auxiliary path. The first wireless communication circuit has a signal path, wherein the signal path has a mixer input port and a signal node distinct from the mixer input port. The auxiliary path is used to electrically connect the LO buffer to the signal node of the signal path. The LO buffer is reused for a loop-back test function through the auxiliary path.

A semiconductor chip includes a first wireless communication circuit, a local oscillator (LO) buffer, and an auxiliary path. The first wireless communication circuit has a signal path, wherein the signal path has a mixer input port and a signal node distinct from the mixer input port. The auxiliary path is used to electrically connect the LO buffer to the signal node of the signal path. The LO buffer is reused for a loop-back test function through the auxiliary path.

A band-pass filter includes an unbalanced port, a first balanced port, a second balanced port, and first to third resonators provided between the unbalanced port and the first and second balanced ports. The second resonator and the third resonator each are a resonator with both ends open. The second resonator and the third resonator are adjacent to each other in a circuit configuration, and electromagnetically coupled by magnetic coupling as main coupling. The first resonator is provided closer to the second resonator than to the third resonator, and jump-coupled to the third resonator.

A band-pass filter includes an unbalanced port, a first balanced port, a second balanced port, and first to third resonators provided between the unbalanced port and the first and second balanced ports. The second resonator and the third resonator each are a resonator with both ends open. The second resonator and the third resonator are adjacent to each other in a circuit configuration, and electromagnetically coupled by magnetic coupling as main coupling. The first resonator is provided closer to the second resonator than to the third resonator, and jump-coupled to the third resonator.

In one example, an apparatus comprises: a first metal layer including a first segment and a second segment, in which the first segment is electrically coupled to a single-ended signal terminal, the second segment has a disconnected end; a second metal layer including a third segment and a fourth segment, in which the third segment is magnetically coupled to the first segment, the fourth segment is magnetically coupled to the second segment, a first end of the third segment and a first end of the fourth segment are electrically coupled at a center tap, and a second end of the third segment and a second end of the fourth segment are electrically coupled to respective first and second signal terminals of a pair of differential signal terminals; and a phase adjustment device proximate the center tap and electrically coupled to a second voltage reference terminal.

In one example, an apparatus comprises: a first metal layer including a first segment and a second segment, in which the first segment is electrically coupled to a single-ended signal terminal, the second segment has a disconnected end; a second metal layer including a third segment and a fourth segment, in which the third segment is magnetically coupled to the first segment, the fourth segment is magnetically coupled to the second segment, a first end of the third segment and a first end of the fourth segment are electrically coupled at a center tap, and a second end of the third segment and a second end of the fourth segment are electrically coupled to respective first and second signal terminals of a pair of differential signal terminals; and a phase adjustment device proximate the center tap and electrically coupled to a second voltage reference terminal.

A packaged integrated circuit (IC) includes an IC die having first and second external contacts and a package substrate. The IC die is attached to the package substrate which includes a balun in a first metal layer. The balun is connected to the first and second external contacts of the IC die and to a first external contact of the package substrate. The first and second external contacts of the IC die communicate a differential signal with the package substrate, and the first external contact of the package substrate communicates a single-ended signal corresponding to the differential signal. Alternatively, the balun is connected to an external contact of the IC die and to first and second external contacts of the package substrate, in which the external contact of the IC die communicates a single-ended signal and the first and second external contacts of the package substrate communicate a differential signal.

A packaged integrated circuit (IC) includes an IC die having first and second external contacts and a package substrate. The IC die is attached to the package substrate which includes a balun in a first metal layer. The balun is connected to the first and second external contacts of the IC die and to a first external contact of the package substrate. The first and second external contacts of the IC die communicate a differential signal with the package substrate, and the first external contact of the package substrate communicates a single-ended signal corresponding to the differential signal. Alternatively, the balun is connected to an external contact of the IC die and to first and second external contacts of the package substrate, in which the external contact of the IC die communicates a single-ended signal and the first and second external contacts of the package substrate communicate a differential signal.

Techniques are provided for fanning out a signal from a balun. In various aspects, the system can include a balun configured to receive a signal for transmission at an input and to provide a representation of the signal at an output, a plurality of pass gate circuits, each pass gate circuit configured to receive the representation of the signal at a first node, to receive a control signal at a second node to pass the representation of the signal to a third node when the control signal is in a first state, and to isolate the representation of the signal from the third node when the control signal is in a second state. The first state of the control signal can include a non-zero voltage, and the second state of the control signal can include the non-zero voltage with a polarity opposite the non-zero voltage of the first state.

Techniques are provided for fanning out a signal from a balun. In various aspects, the system can include a balun configured to receive a signal for transmission at an input and to provide a representation of the signal at an output, a plurality of pass gate circuits, each pass gate circuit configured to receive the representation of the signal at a first node, to receive a control signal at a second node to pass the representation of the signal to a third node when the control signal is in a first state, and to isolate the representation of the signal from the third node when the control signal is in a second state. The first state of the control signal can include a non-zero voltage, and the second state of the control signal can include the non-zero voltage with a polarity opposite the non-zero voltage of the first state.