A transformer includes multiple differential ports and first and second transformer windings. The first transformer winding includes a first transformer half-winding coupled to a first differential port of the differential ports. The first transformer winding also includes a second transformer half-winding coupled to a second differential port of the differential ports. An amplifier system that has a transformer is also provided. The amplifier system includes a first and a second stage amplifier. The first stage amplifier includes a first and a second amplifier. The second stage amplifier includes a third and a fourth amplifier. The transformer is coupled between the first stage amplifier and the second stage amplifier, where the transformer has a primary loop and a secondary loop. The primary loop of the transformer may be configured to receive differential signals of the first amplifier. A method for fabricating a transformer is also provided.

A transformer includes multiple differential ports and first and second transformer windings. The first transformer winding includes a first transformer half-winding coupled to a first differential port of the differential ports. The first transformer winding also includes a second transformer half-winding coupled to a second differential port of the differential ports. An amplifier system that has a transformer is also provided. The amplifier system includes a first and a second stage amplifier. The first stage amplifier includes a first and a second amplifier. The second stage amplifier includes a third and a fourth amplifier. The transformer is coupled between the first stage amplifier and the second stage amplifier, where the transformer has a primary loop and a secondary loop. The primary loop of the transformer may be configured to receive differential signals of the first amplifier. A method for fabricating a transformer is also provided.

A high-frequency signal predistortion device includes a high-frequency signal estimator, a predistortion estimator, and a predistorter. The high-frequency signal estimator is configured to determine non-linear distortion characteristics of high-frequency signals transmitted by antennas. The predistortion estimator is coupled to the high-frequency signal estimator. The predistortion estimator is configured to determine a predistortion coefficient based on the non-linear distortion characteristics. The predistorter is coupled to the predistortion estimator. The predistorter is configured to distort a base signal of the high-frequency signals based on the predistortion coefficient.

Apparatus and methods for overload protection of low noise amplifiers (LNAs) are provided herein. In certain configurations, an LNA system includes an input switch having an analog control input that controls an impedance of the input switch, an LNA that amplifies a radio frequency (RF) input signal received from the input switch, and an overload protection circuit that provides feedback to the input switch's analog control input based on detecting a signal level of the LNA. The overload protection circuit detects whether or not the LNA is overloaded. Additionally, when the overload protection circuit detects an overload condition, the overload protection circuit provides feedback to the analog control input of the switch to increase the impedance of the switch and reduce the magnitude of the RF input signal received by the LNA.

Apparatus and methods for overload protection of low noise amplifiers (LNAs) are provided herein. In certain configurations, an LNA system includes an input switch having an analog control input that controls an impedance of the input switch, an LNA that amplifies a radio frequency (RF) input signal received from the input switch, and an overload protection circuit that provides feedback to the input switch's analog control input based on detecting a signal level of the LNA. The overload protection circuit detects whether or not the LNA is overloaded. Additionally, when the overload protection circuit detects an overload condition, the overload protection circuit provides feedback to the analog control input of the switch to increase the impedance of the switch and reduce the magnitude of the RF input signal received by the LNA.

A radio apparatus includes an amplifier that amplifies electrical power of a signal that is wirelessly transmitted, and a processor that executes a process including: performing, by using a distortion compensation coefficient that compensates distortion generated in the amplifier, distortion compensation of an input signal; reading, from a predetermined memory, a threshold that varies in accordance with the electrical power of the input signal; and comparing the read threshold with a monitoring target which includes the distortion compensation coefficient used with respect to the input signal to monitor whether an abnormality is present in the distortion compensation of the input signal.

A radio apparatus includes an amplifier that amplifies electrical power of a signal that is wirelessly transmitted, and a processor that executes a process including: performing, by using a distortion compensation coefficient that compensates distortion generated in the amplifier, distortion compensation of an input signal; reading, from a predetermined memory, a threshold that varies in accordance with the electrical power of the input signal; and comparing the read threshold with a monitoring target which includes the distortion compensation coefficient used with respect to the input signal to monitor whether an abnormality is present in the distortion compensation of the input signal.

RF communications circuitry, which includes a first RF filter structure and RF detection circuitry, is disclosed. The first RF filter structure includes a first group of RF resonators, which include a first pair of weakly coupled RF resonators coupled to a signal path of a first RF signal. One of the first group of RF resonators provides a first sampled RF signal. The RF detection circuitry detects the first sampled RF signal to provide a first detected signal. The first RF filter structure adjusts a first filtering characteristic of the first RF filter structure based on the first detected signal.

RF communications circuitry, which includes a first RF filter structure and RF detection circuitry, is disclosed. The first RF filter structure includes a first group of RF resonators, which include a first pair of weakly coupled RF resonators coupled to a signal path of a first RF signal. One of the first group of RF resonators provides a first sampled RF signal. The RF detection circuitry detects the first sampled RF signal to provide a first detected signal. The first RF filter structure adjusts a first filtering characteristic of the first RF filter structure based on the first detected signal.

Systems and methods for compensating for non-linearity of a non-linear subsystem using predistortion are disclosed. In one embodiment, a system includes a non-linear subsystem and a predistorter configured to effect predistortion of an input signal of the non-linear subsystem such that the predistortion compensates for a non-linear characteristic of the non-linear subsystem. In addition, the system includes a narrowband filter that filters a feedback signal that is representative of an output signal of the non-linear subsystem to provide a filtered feedback signal, and an adaptor that adaptively configures the predistorter based on the filtered feedback signal and a reference signal that is representative of an input signal of the non-linear subsystem. By utilizing the filtered feedback signal, rather than the feedback signal, a complexity, and therefore, cost of the adaptor is substantially reduced.