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本文叙述一种双环自适应增量调制(DLADM)系统。它由一个内环和一个外环组成,内环是线性增量调制(LDM);外环是数字压扩增量调制(DCDM),具有量化阶自适应的功能。这种DLADM是专为移动通信研制的,具有数码率低、电路简单、单一电源、功耗低等特点。对所研制的系统进行了性能测试,在数码率为9.6kbps时,对于400Hz正弦信号,最大的信号量化噪声比SQNR_m是18.5dB,SQNR>16dB的动态范围大于25dB;80Hz正弦信号时的SQNR_m是17.8dB,SNR>15dB的动态范围大于20dB,平均单词可懂度为90%。数码率为8kbps、400Hz正弦信号时的SQNR_m为17.7dB,SQNR>16dB的动态范围大于22dB,话音可懂。文中叙述其工作原理,进行了理论分析,介绍了测试结果。
This paper describes a double loop adaptive delta modulation (DLADM) system. It consists of an inner ring and an outer ring, the inner ring is a linear incremental modulation (LDM); the outer ring is a digital companding delta modulation (DCDM), with the quantization level adaptive function. This DLADM is designed for mobile communications developed with a low digital rate, simple circuit, a single power supply, low power consumption and so on. The performance of the system was tested. When the digital rate is 9.6kbps, the maximum signal-to-noise ratio of SQNR_m is 18.5dB and the dynamic range of SQNR> 16dB is greater than 25dB for 400Hz sinusoidal signal. SQNR_m of 80Hz sinusoidal signal is 17.8dB, SNR> 15dB dynamic range greater than 20dB, average word readability of 90%. Digital rate of 8kbps, 400Hz sinusoidal signal SQNR_m is 17.7dB, SQNR> 16dB dynamic range greater than 22dB, the voice is understandable. The article describes its working principle, a theoretical analysis, introduced the test results.