Abstract: A low-profile antenna structure can control its directivity with great flexibility. Excited elements 11 and 12 are symmetrically arranged on a y-axis, whereas parasitic elements 13 and 14 are symmetrically arranged on an x-axis, with respect to an origin. The excited elements, as well as the parasitic elements, each have an inverted-F antenna structure and are a distance of ?/4 apart from each other. Feed circuits 21 and 22 are respectively connected to and feed signals to the excited elements 11 and 12, such that phases of the signals to be fed are different from each other by a desired degree. Variable reactors 23 and 24 (i) are respectively connected to the parasitic elements 13 and 14, and (ii) in accordance with reactance values thereof, can each change an electrical length of the corresponding one of the parasitic elements.

Abstract: A low-profile antenna structure can control its directivity with great flexibility. Excited elements 11 and 12 are symmetrically arranged on a y-axis, whereas parasitic elements 13 and 14 are symmetrically arranged on an x-axis, with respect to an origin. The excited elements, as well as the parasitic elements, each have an inverted-F antenna structure and are a distance of ?/4 apart from each other. Feed circuits 21 and 22 are respectively connected to and feed signals to the excited elements 11 and 12, such that phases of the signals to be fed are different from each other by a desired degree. Variable reactors 23 and 24 (i) are respectively connected to the parasitic elements 13 and 14, and (ii) in accordance with reactance values thereof, can each change an electrical length of the corresponding one of the parasitic elements.

Abstract: An RF power amplifier includes an RF power amplifying section having a variable amplification gain. A phase shifter connected to the RF power amplifying section serves to shift a phase of an output signal of the RF power amplifying section. The phase shifter has an input terminal subjected to the output signal of the RF power amplifying section and an output terminal subjected to a signal which results from shifting the phase of the output signal of the RF power amplifying section. A control-signal generating section serves to generate a control signal on the basis of the signals at the input terminal and the output terminal of the phase shifter. The control signal depends on a power of the output signal of the RF power amplifying section. The amplification gain of the RF power amplifying section is controlled in response to the control signal.