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相关概念视频

Frequency-dependent Selection01:21

Frequency-dependent Selection

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When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.
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Upsampling01:22

Upsampling

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Managing signal sampling rates is essential in digital signal processing to maintain signal integrity. A decimated signal, characterized by a reduced frequency range due to its lower sampling rate, can be upsampled by inserting zeros between each sample. This upsampling process expands the original spectrum and introduces repeated spectral replicas at intervals dictated by the new Nyquist frequency. To refine this zero-inserted sequence, it is passed through a lowpass filter with a cutoff...
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Design Example01:23

Design Example

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The innovation of touch-tone telephony revolutionized the telecommunications industry by replacing the traditional rotary dial with a dual-tone multi-frequency (DTMF) signaling system. This system uses a matrix-style keypad with buttons arranged in four rows and three columns, creating 12 distinct signals each assigned to a pair of frequencies. Each button press results in a simultaneous generation of two sinusoidal tones – one from a low-frequency group (697 to 941 Hz) and one from a...
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Sampling Theorem01:15

Sampling Theorem

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In signal processing, the analysis of continuous-time signals, denoted as x(t), often involves sampling techniques to convert these signals into discrete-time signals. This process is essential for digital representation and manipulation. A critical component in sampling is the train of impulses, characterized by the sampling interval and the sampling frequency. The relationship between these parameters and the original signal's properties dictates the success of the sampling process.
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Frequency-Domain Interpretation of PD Control01:24

Frequency-Domain Interpretation of PD Control

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Proportional-Derivative (PD) controllers are widely used in fan control systems to improve stability and performance. A fan control system can be effectively represented using a Bode plot to illustrate the impact of a PD controller through its transfer function. The Bode plot visually conveys how PD control modifies the fan's response across various frequencies, providing a frequency domain interpretation of the controller's behavior.
The proportional control gain, combined with the...
177
Basic Discrete Time Signals01:16

Basic Discrete Time Signals

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The unit step sequence is defined as 1 for zero and positive values of the integer n. This sequence can be graphically displayed using a set of eight sample points, showing a step function starting from n=0 and remaining constant thereafter.
The unit impulse or sample sequence is mathematically expressed as zero for all n values except at n=0, where it is one. The unit impulse sequence, denoted by δ(n), is the first difference of the unit step sequence, while the unit step sequence u(n) is...
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相关实验视频

Updated: Sep 13, 2025

Quasi-light Storage for Optical Data Packets
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基于编码辅助符号选择的四维QPSK调制传输方案.

Junjie Cai, Bo Liu, Jianxin Ren

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    概括

    我们介绍了一种使用编码来提高信号传输效率的新型四维正方位相位移关键 (4D-SS-QPSK) 方案. 这种方法可以提高光纤系统中的接收器灵敏度.

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    相关实验视频

    Last Updated: Sep 13, 2025

    Quasi-light Storage for Optical Data Packets
    07:45

    Quasi-light Storage for Optical Data Packets

    Published on: February 6, 2014

    11.0K
    Generation and Coherent Control of Pulsed Quantum Frequency Combs
    06:42

    Generation and Coherent Control of Pulsed Quantum Frequency Combs

    Published on: June 8, 2018

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    A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
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    A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

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    科学领域:

    • 光学通信是指光学通信.
    • 数字信号处理 数字信号处理
    • 信息理论 信息理论

    背景情况:

    • 传统的正方形相位移键 (QPSK) 由于高维空间的低效利用而受到影响.
    • 比特间接编码调制 (BICM) 是数字通信中的标准技术.

    研究的目的:

    • 提出和评估一个新的四维方格相位转换键 (4D-SS-QPSK) 调制方案.
    • 在强度调制/直接检测 (IM/DD) 系统中提高光谱效率和接收器灵敏度.

    主要方法:

    • 整合哈夫曼编码与位交叉编码调制 (BICM) 进行非统一的信号生成.
    • 三个QPSK信号和一个BPSK信号聚合成一个四维相位单元.
    • 在源 (SE) 的帮助下选择符号子集,并将其映射到预定义的四维子集.

    主要成果:

    • 在2公里的IM/DD七核光纤传输系统中以14.175Gb/s的速度进行演示.
    • 在3.8 × 10−3.3的HD-FEC BER极限下,获得了 -10.4 dBm的接收器光学功率.
    • 在没有BICM的情况下,通过3D-SS-QPSK获得了大约0.7dB的接收器灵敏度增益,在没有BICM的情况下通过4D-SS-QPSK获得了0.5dB.

    结论:

    • 拟议的4D-SS-QPSK方案有效地克服了传统QPSK在高维空间利用方面的局限性.
    • 编码辅助的符号选择显著提高了接收器的灵敏度和传输效率.
    • 这种调制方案为未来的高速光通信系统提供了有希望的进步.