中文摘要：

在语音通信中，声回声抵消技术是一种用于消除在扬声器与传声器共存情况下所产生的回声干扰的技术．在声回声抵消系统的实现过程中，可以通过子带技术来提高系统的性能，并减小算法本身的运算量．常见的子带算法多是基于复值实现的，而复数运算往往会给系统的实现带来一些麻烦．提出了一种适用于声回声抵消系统的过采样实值子带算法，该子带算法通过通用离散傅立叶变换对全通带输入信号进行调制，然后将各频带内的信号通过原型低通滤波器同时降采样处理得到各复值子带信号，然后采用共轭调制分量对各复值子带信号对进行的单边带调制，保持子带信号的共轭特性，取信号实部进而实现了实值子带信号．通过对该实值子带算法的运算量进行分析表明，该算法避免了各子带内系统对复数的处理的复杂性，并达到子带内系统运算量减半的目的．算法仿真实验结果表明：该算法与复值子带算法的性能相当，具有实时性好、可靠性高、实现简单等特点，适用于声回声抵消系统等．

英文摘要：

In speech telecommunication, where a microphone and a loudspeaker are placed close to each other, users are always annoyed by the delayed echo. Acoustic echo cancellation system is developed to reduce the disturbance of the echo noise. In practieal implementation of acoustic echo cancellation, subband technology is used to improve the system performance and reduce the computational complexity of the algorithm. The general subband construction is based on the complex-valued implementation. However, the complex-valued calculation, such as complex-valued multiplication, results in some problems. In this paper, an oversampled real-valued subband algorithm for acoustic echo cancellation is proposed. The proposed algorithm modulates the input fullband signal by general discrete Fourier transformation （GDFT） to shift the focused subband signals to corresponding frequency range. Then the signals in subbands are passed through the proto lowpass filter and decimated to produce the odd type complex-valued subband signals. The complex-valued subband signal pairs are then modulated on single side band by conjugate modulating components to realize the real-valued subband signals. However, the conjugate modulation does not occupy extra computational complexity for the modulation component feature, which can be implemented by fetching their real and imaginary or their opposing ones iteratively. The analysis on the real-valued subband algorithm demonstrates that it avoids complex computations of complex-valued signal in subbands and half computational complexity is cut off. Compared with the subband algorithm in which uses single modulation component to modulate the complex-valued subband signals, the proposed subband algorithm still keeps the conjugate relation between complex-valued subband signal pairs. The simulation results of the algorithm demonstrate that the proposed algorithm has the same performance as the complex-valued subband algorithm and is superior in real-time implementation, high stability and easy realizati