Abstract: In accordance with some embodiments of the present disclosure, a multi-band transmitter comprises a plurality of band paths with each band path configured for a different frequency range. Each band path comprises a modulator configured to modulate a data signal onto a carrier signal associated with the frequency range of the band path to generate a radio frequency (RF) signal associated with the band path and frequency range of the band path. Each band path also comprises a step-down balun that includes an input coil configured to receive the RF signal from the modulator. Each band path further comprises a tuner configured to tune the input coil to the frequency range of the band path. The tuner is also configured to compensate for off-state conduction of switches of the tuner to reduce non-linear tuning effects of the balun associated with the off-state conduction.

Abstract: In accordance with some embodiments of the present disclosure, a multi-band transmitter comprises a plurality of band paths with each band path configured for a different frequency range. Each band path comprises a modulator configured to modulate a data signal onto a carrier signal associated with the frequency range of the band path to generate a radio frequency (RF) signal associated with the band path and frequency range of the band path. Each band path also comprises a step-down balun that includes an input coil configured to receive the RF signal from the modulator. Each band path further comprises a tuner configured to tune the input coil to the frequency range of the band path. The tuner is also configured to compensate for off-state conduction of switches of the tuner to reduce non-linear tuning effects of the balun associated with the off-state conduction.

Abstract: A soft saturation detection circuit for a radio frequency (“RF”) power amplifier is configured to detect the onset of soft saturation in an unambiguous and accurate manner. The circuit compares the time derivative of a voltage signal indicative of the RF output power to the time derivative of a control voltage signal for the RF power amplifier. The circuit also employs a gating mechanism that ensures that a soft saturation indication signal is generated under appropriate operating conditions.

Abstract: Method and apparatus are provided for protecting radio frequency (RF) power amplifiers. A circuit (10) is provided for limiting a supply current to a first stage (Q3) of the RF power amplifier having a second stage (Q2) coupled to the first stage. The circuit comprises a comparator (14) having first and second inputs and an output, and a switching circuit (12, 20, 22, 24) having an input coupled to the output of the comparator (14) and having an output configured to couple to the first stage (Q3). The first input of the comparator (14) is configured to receive the supply current, and the second input is configured to receive a current supplied to the second stage (Q2). The comparator (14) is configured to compare a ratio of the supply current to the first stage to the current supplied to the second stage (Q2) with a predetermined value. The switching circuit (12, 20, 22, 24) is configured to limit the supply current to the first stage (Q3) when the ratio exceeds the predetermined value.

Abstract: A radio frequency (“RF”) power amplifier circuit as described herein is configured to detect and measure an output load mismatch and to adjust the operating characteristics of the RF power amplifier to reduce output signal distortion. The circuit includes a directional RF signal coupler that obtains a coupled reflected RF signal that is indicative of the output load mismatch. The coupled reflected RF signal is processed to generate one or more bias control signals for the RF power amplifier. In operation, a mismatch condition will result in a measurable coupled reflected RF signal and a corresponding reduction in output power from the RF power amplifier. Ultimately, the output power control mechanism strives to maintain the RF power amplifier within a linear operating range.

Abstract: A radio frequency (RF) power amplification circuit including a power amplifier is provided for preventing breakdown of the power amplifier. The power amplifier includes an input for receiving RF signals and an output for providing amplified RF signals. The RF power amplification circuit also includes a bias circuit coupled to the input of the power amplifier to permit normal operation of the power amplifier when the base current is below a predetermined current threshold and to prevent normal operation of the power amplifier when the base current is above the predetermined current threshold.