7 results about "Fractional bandwidth" patented technology

The invention discloses a three-path non-modulation broadband pseudo Doherty power amplifier, which belongs to the field of Doherty power amplifiers and comprises a one-to-three power divider, a phase compensation network, a main power amplifier, two paths of auxiliary power amplifiers and an output synthesis network formed by four transmission lines. The asymmetric architecture that the main power amplifier works in the class AB and the two paths of auxiliary power amplifiers work in the class C is adopted, and non-modulation synthesis is realized by utilizing a microstrip line network, so that the load impedance of the main power amplifier is kept constant in a broadband. According to the Doherty power amplifier, the problems that a traditional Doherty power amplifier is insufficient in power rollback range and narrow in working bandwidth are effectively solved, the rollback range as high as 9.5 dB and the fractional bandwidth exceeding 60% are achieved, meanwhile, a transformer difficult to integrate is abandoned, and the Doherty power amplifier has good process universality and high performance.

A broadband Doherty power amplifier is disclosed. The Doherty power amplifier includes a main power amplifier and a peak amplifier. Compared to the conventional method of combining the outputs of the main and peak amplifiers before an impedance transformation circuit, this Doherty power amplifier combines the outputs after an impedance transformation circuit in the peak amplifier output path. This eliminates or at least reduces the possible impedance step drop and corresponding impedance step rise for the main output path. This reduction or elimination of the step drop and rise reduces insertion loss and allows for increased efficiency at the first efficiency peak, thus improving the fractional bandwidth of the Doherty power amplifier.

An antenna device comprising a plurality of antennas arranged on a vehicle along a latitude direction intersecting the vehicle's direction of travel, includes: a first antenna supporting radio waves at a first frequency; and a second antenna supporting radio waves at a second frequency band whose fractional bandwidth is smaller than the fractional bandwidth of the first frequency, the second antenna being arranged on an outside relative to the first antenna in the latitude direction of the vehicle, the second antenna.

An ultra-wideband dual-polarized tightly coupled bowtie antenna array for ground-based polar ice sounding radar is described. The antenna array has a very large effective aperture to increase the directivity. At the same time, it is lightweight and low profile to minimize the payload and maximize the survey range. In an implementation, the antenna array operates between 180-620 MHz with a fractional bandwidth of 3.4:1. The broadband performance benefits from the tightly coupled antenna elements. A feature of the antenna array is the planar feeding structure without balun. The antenna array element has the microstrip feeding line integrated with one arm of the bowtie antenna. The other arm is directly fed by the microstrip line. By adding a ferrite core around the coax cable for common mode suppression, the bowtie antenna element can be fed differentially without using bulky vertical feeding structure and balun.

A dual-input microwave power amplifier (PA) with high-efficiency. The PA exploits the continuum of modes between the Doherty and Chireix PA mode of operation to achieve 40% fractional bandwidth while relying on the physical linear dispersion of the transmission lines of the lossless output combiner. A constant output is achieved at peak power over the entire bandwidth. The output backoff varies from 6 dB in the Doherty mode to 8 dB in the Chireix mode. The PA operates over a wider range of frequencies from 1 to 8 GHz. The dual-input PA operates in mixed-mode and thus requires variable input power drives and outphasing angle.

Various methods and systems are provided for increasing a fractional bandwidth of an ultrasound device, for use in both low and high frequency applications. In one example, where a transducer array includes one or more transducer elements comprising a plurality of capacitive micromachined ultrasound transducers (cMUT), the fractional bandwidth may be advantageously increased by applying different bias voltages to different groupings of cMUTs within each transducer element. A ratio between the different bias voltages may be optimized to maximize the fractional bandwidth. In another example, the different bias voltages may be configured to operate a first grouping of cMUTs in a transmit mode, and a second grouping of cMUTs in a receive mode.