关键字:直接数字合成(DDS); AD7008;AT89S51单片微机。
Abstract
In some electronic equipments electric circuit board fail monitors, often needs the frequency, the scope all can by the computer automatic
control supply oscillator. Uses such as MAX038 signal generating
device component and so on chip sur- resistance and cut switch
although also can adjust the frequency and the scope, but this kind of
adjustment is separate, also the electric circuit is complex, uses not
conveniently.But uses the direct digital synthesis chip AD7008 constitution the controllable supply oscillator, may produce the sine wave, the frequency-modulated wave, the amplitude modulation affects the
square-wave and so on, and its signal frequency and the scope may come
the accuracy control by the microcomputer, the adjustment to be
extremely convenient.
The present paper introduced carries on the parameter establishment
and the software programming with AT89S51 monolithic microcomputer
control direct numeral frequency synthesizer DDS AD7008, the
realization may produce the sine wave, the frequency-modulated wave,
the amplitude modulation affects the square-wave and so on, and its
signal frequency and the scope may come the accuracy control by the
microprocessor, the adjustment to be extremely convenient. This design topic is the electric circuit and the programming language knowledge which the use studies, controls with 51 series monolithic integrated circuits, may realize the frequency modulation which D D S chip (A D 7,008) completes, the phase modulation, the amplititude-modulated signal output.
The article first introduced the DDS theory knowledge, then in detail
introduced realizes this kind of theory hardware equipment, according
to hardware equipment determination design proposal. Then is to the
design proposal concrete description. In the description, in detail
introduced the AD7008 function characteristic.
引 言
自本世纪30年代末频率合成技术开始建立,迄今为止,频率合成技术已有近70年的历史。随着数字集成电路和微电子技术的发展,1971年,美国学者J.Tierney,C.M.Rader和B.Gold提出了以全数字技术,从相位概念出发直接合成所需波形的一种新的频率合成原理——直接数字频率合成(Direct Digital Frequency Synthesize)技术,它将先进的数字处理技术和方法引入信号合成领域。DDS的出现导致了频率合成技术领域的第二次革命。
直接数字频率合成器(Direct Digital Frequency Synthesis简称DDS)问世之初,构成DDS元器件的速度的限制和数字化引起的噪声这两个主要缺点阻碍了DDS的发展与实际应用。近几年超高速数字电路的发展以及对DDS的深入研究,DDS的最高工作频率以及噪声性能已接近并达到锁相频率合成器相当的水平。随着微电子技术的迅速发展,直接数字频率合成器得到了飞速的发展,它以有别于其它频率合成方法的优越性能和特点成为现代频率合成技术中的姣姣者。其主要优点有:(1)频率转换快:DDS频率转换时间短,一般在纳秒级;(2)分辨率高:大多数DDS可提供的频率分辨率在1 Hz数量级,许多可达0.001 Hz;(3)频率合成范围宽;(4)相位噪声低,信号纯度高;(5)可控制相位:DDS可方便地控制输出信号的相位,在频率变换时也能保持相位联系;(6)生成的正弦/余弦信号正交特性好等。因此,利用DDS技术特别容易产生频率快速转换、分辨率高、相位可控的信号,这在电子测量、雷达系统、调频通信、电子对抗等领域具有十分广泛的应用前景。
课题要求
要求信号输出范围为0~20MHz。