Abstract: Embodiments of a low-complexity and potentially physically small wideband impedance transformer that can be used in a combining network of a wideband Doherty amplifier are disclosed. In one embodiment, a wideband Doherty amplifier includes Doherty amplifier circuitry and a wideband combining network. The wideband combining network includes a wideband quarter-wave impedance transformer that includes a quarter-wave impedance transformer and compensation circuitry connected in parallel with the quarter-wave impedance transformer at a low-impedance end of the quarter-wave impedance transformer. The compensation circuitry is configured to reduce a total quality factor of the wideband quarter-wave impedance transformer as compared to a quality factor of the quarter-wave impedance transformer, which in turn increases a bandwidth of the wideband quarter-wave impedance transformer, and thus a bandwidth of the wideband Doherty amplifier.

Abstract: Microstrip directional couplers and methods of their design are disclosed. According to one aspect, a microstrip directional coupler has a substrate of a first thickness. Disposed upon the substrate is a first microstrip having a first portion of a first length and a second microstrip having a second portion of a second length. The first and second microstrips are positioned to exhibit a gap between the first portion and the second portion. The first and second lengths are less than one sixteenth of a wavelength at the lowest frequency of operation of the directional coupler. The gap is less than a predetermined amount to reduce a difference in phase velocity of even and odd modes of the microstrip directional coupler.

Abstract: Embodiments of a low-complexity and potentially physically small wideband impedance transformer that can be used in a combining network of a wideband Doherty amplifier are disclosed. In one embodiment, a wideband Doherty amplifier includes Doherty amplifier circuitry and a wideband combining network. The wideband combining network includes a wideband quarter-wave impedance transformer that includes a quarter-wave impedance transformer and compensation circuitry connected in parallel with the quarter-wave impedance transformer at a low-impedance end of the quarter-wave impedance transformer. The compensation circuitry is configured to reduce a total quality factor of the wideband quarter-wave impedance transformer as compared to a quality factor of the quarter-wave impedance transformer, which in turn increases a bandwidth of the wideband quarter-wave impedance transformer, and thus a bandwidth of the wideband Doherty amplifier.

Abstract: Embodiments of a low-complexity and potentially physically small wideband impedance transformer that can be used in a combining network of a wideband Doherty amplifier are disclosed. In one embodiment, a wideband Doherty amplifier includes Doherty amplifier circuitry and a wideband combining network. The wideband combining network includes a wideband quarter-wave impedance transformer that includes a quarter-wave impedance transformer and compensation circuitry connected in parallel with the quarter-wave impedance transformer at a low-impedance end of the quarter-wave impedance transformer. The compensation circuitry is configured to reduce a total quality factor of the wideband quarter-wave impedance transformer as compared to a quality factor of the quarter-wave impedance transformer, which in turn increases a bandwidth of the wideband quarter-wave impedance transformer, and thus a bandwidth of the wideband Doherty amplifier.

Abstract: Embodiments of a low-complexity and potentially physically small wideband impedance transformer that can be used in a combining network of a wideband Doherty amplifier are disclosed. In one embodiment, a wideband Doherty amplifier includes Doherty amplifier circuitry and a wideband combining network. The wideband combining network includes a wideband quarter-wave impedance transformer that includes a quarter-wave impedance transformer and compensation circuitry connected in parallel with the quarter-wave impedance transformer at a low-impedance end of the quarter-wave impedance transformer. The compensation circuitry is configured to reduce a total quality factor of the wideband quarter-wave impedance transformer as compared to a quality factor of the quarter-wave impedance transformer, which in turn increases a bandwidth of the wideband quarter-wave impedance transformer, and thus a bandwidth of the wideband Doherty amplifier.

Abstract: Microstrip directional couplers and methods of their design are disclosed. According to one aspect, a microstrip directional coupler has a substrate of a first thickness. Disposed upon the substrate is a first microstrip having a first portion of a first length and a second microstrip having a second portion of a second length. The first and second microstrips are positioned to exhibit a gap between the first portion and the second portion. The first and second lengths are less than one sixteenth of a wavelength at the lowest frequency of operation of the directional coupler. The gap is less than a predetermined amount to reduce a difference in phase velocity of even and odd modes of the microstrip directional coupler.