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Diversity combining is the technique applied to combine the multiple received signals of a diversity reception device into a single improved signal. == Various techniques == Various diversity combining techniques can be distinguished: * Equal-gain combining: All the received signals are summed coherently. * Maximal-ratio combining is often used in large phased-array systems: The received signals are weighted with respect to their SNR and then summed. The resulting SNR yields where is SNR of the received signal . * Switched combining: The receiver switches to another signal when the currently selected signal drops below a predefined threshold. This is also often called "Scanning Combining". * Selection combining: Of the N received signals, the strongest signal is selected. When the N signals are independent and Rayleigh distributed, the expected diversity gain has been shown to be , expressed as a power ratio.〔D.G. Brennan, "Linear diversity combining techniques," Proc. IRE, vol.47, no.1, pp.1075–1102, June 1959〕 Therefore, any additional gain diminishes rapidly with the increasing number of channels. This is a more efficient technique than switched combining. Sometimes more than one combining technique is used – for example, lucky imaging uses selection combining to choose (typically) the best 10% images, followed by equal-gain combining of the selected images. Other signal combination techniques have been designed for noise reduction and have found applications in single molecule biophysics, chemometrics among other disciplines.〔(Mashaghi et al. Noise reduction by signal combination in Fourier space applied to drift correction in optical tweezers, Rev. Sci. Instrum. 82, 115103 (2011) )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Diversity combining」の詳細全文を読む スポンサード リンク
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