Unlike conventional conception that power amplifier and filter are regarded as two separate components and designed separately, this paper presents a high efficiency power amplifier with filtering capability, which is called filtering power amplifier. The proposed power amplifier integrates a bandpass filter as output matching network so that entire size is reduced to some extent. The filter will play the role of filtering and impedance matching simultaneously, and thus high-order harmonics are suppressed for output of the filtering power amplifier. For demonstration, an example of filtering power amplifier was designed, fabricated and measured. The measurement shows that it is featured by highly-selective bandpass response and good out-of-band performance. As high as 46.2 dB suppression can be achieved and extended over the forth-order harmonic. The example also retains the advantages of high efficiency and output power. The maximum output power can reach 40.5 dBm, and the maximum power-added efficiency is as high as 62%.
At present, it is a trend in wireless communication to integrate conventional separate components into a single one for further miniaturisation and whole performance optimisation. In this study, a novel filtering Doherty power amplifier topology is proposed, which incorporates a bandpass power divider for power division. The power divider is characterised by third‐order bandpass response and good out‐of‐band performance, and then it can purify the input spectrum for the whole amplifier. For demonstration, an example of this filtering Doherty power amplifier at 2.0 GHz was designed, fabricated and measured. The measured results show that at least 21 dB of the out‐of‐band suppression is obtained up to fourth harmonic for purifying the input spectrum. Meanwhile, high back‐off efficiency is still retained for this filtering Doherty power amplifier.
Vibration measurement for flexible structures is widely used in various kinds of precision engineering fields. However, it is a challenge to measure vibration in special applications, such as cryogenic, dangerous and magnetic interference. In this paper, a high-precision vibration measurement system based on machine vision is designed. The circle center on the target is employed as the image feature. The circle feature is extracted using the improved algorithm based on gradient Hough transform. Then the image Jacobian matrix is used to compute the vibrations in Cartesian space from the image feature changes. Experiments verify the effectiveness of the proposed methods.
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