波形发生器毕业设计论文

绪论波形发生器是一种广泛应用于电子电路，自动控制和科学实验等领域的信号源。

比如电参量的测量、雷达、通信、电子对抗与电子系统、宇航和严控遥测技术等等，从某种意义上说高品质信号源更是实现高性能指标的关键，很多现代电子设备和系统的功能都直接依赖于所用信号源的性能，因此，高品质信号源被人们喻为众多电子系统的“心脏”。

随着通信、雷达的不断发展，多信号源的频率稳定度、频谱纯度、频率范围和输出频率的个数以及信号波形的形状提出越来越多的要求。

为了提高信号源输出频率稳定度，可以采用晶体振荡器等方法来解决。

为了满足频率个数多的要求，可以采用频率合成技术，即通过对频率进行加减乘除运算，可从一个高稳定度和高精确度的标准频率源，产生大量的具有同一稳定度和精确度的不同频率。

运用DDS技术是设计波形发生器的一种通用手段，DDS不仅可以产生正弦波同时也可以产生任意波，这是其他频率合成方式所不具有的特点，任意波在各个领域有着广泛的应用。

通过DDS这种方法产生任意波是一种简单，低成本的方法，通过增加波形点数可以使输出达到很高的精度，这都是其他方法所无法比拟的。

自80年代以来各国都在研制DDS产品，并广泛应用于各个领域。

其中以AD公司的产品比较有代表性。

如AD7008、AD9850、AD9851、AD9852、AD9858等。

其系统时钟频率从30MHz到300MHz不等，其中的AD9858系统时钟更是达到了lGHz。

这些芯片还具有调制功能。

如AD7008可以产生正交调制信号，而AD9852也可以产生FSK、PSK、线性调频以及幅度调制的信号。

这些芯片集成度高，内部都集成了D/A转换器，精度最高可达12bit。

同时都采用了一些优化设计来提高性能。

如这些芯片中大多采用了流水技术，通过流水技术的使用，提高了相位累加器的工作频率，从而使得DDS芯片的输出频率可以进一步提高。

通过运用流水技术在保证相位累加器工作频率的前提下，相位累加器的字长可以设计得更长，如AD9852的相位累加器达到了48位。

而不是之前型号的32位，这样输出信号的频率分辨率大大提高了。

运用DDS技术生产的DDS任意波型信号发生器是较新的一类信号源，并且已经广泛投入使用。

它不仅能产生传统函数信号发生器能产生的正弦波、方波、三角波、锯齿波，还可以产生任意编辑的波形。

由于DDS的自身特点，还可以很容易的产生一些数字调制信号，如FSK、PSK等。

一些高端的信号发生器甚至可以产生通讯信号。

同时输出波形的频率分辨率、频率精度等指标也有很大的提高。

如HP公司的HP33120可以产生lOmHz-15MHz的正弦波和方波，同时还可以产生lOmHz-5MHz的任意波形，还具备调制功能，可以产生AM、FM、FSK、猝发、扫频等信号。

HP公司的HP33250可以产生1uHz-80MHz的正弦波和方波，产生1uHz到25MHz的任意波形。

BK PRECISION公司的4070A型函数级任意波形发生器产生的正弦波和方波输出频率DC-21．5MHz，频率分辨率10mHZ。

同时还具有AM、FM、PM、SSB、BPSK、FSK、猝发、DTMFGeneration和DTMFDetection的功能。

并且具有了和PC机良好的接口，可以通过WINDOWS 界面的程序进行任意波形的编辑。

除了在仪器中的应用外，DDS在通信系统和雷达系统中也有很重要的用途。

通过DDS可以比较容易的产生一些通信中常用的调制信号如：频移键控(FSK)、二进制相移键控(BPSK)和正交相移键控(QPSK)等。

DDS可以产生两路相位严格正交的信号，在正交调制和解调中的到广泛应用，是一种很好的本振源。

此外随着集成电路制造工艺的逐步提高，通过采用先进的工艺和低功耗的设计，数字集成电路的工作速度已经有了很大的提高。

现在最新的DDS芯片工作频率已经可以达到1GHz，这样就可以产生频带比较宽的输出信号了。

为了进一步提高DDS的输出频率，产生了很多DDS与其他技术结合的频率合成方法。

如当输出信号是高频窄带信号的时候可以用混频滤波的方法扩展DDS 的输出，也可以利用DDS的频谱特性来产生高频信号，如利用较高的镜像频率输出。

可见，基于DDS技术的波形发生器能实现高稳定度、高精度、高分辨率的波形输出，具有频率切换速度快、体积小、价格便宜的特点,是一种很有发展前途的信号源。

所以本设计采用此方案。

近年来，随着可编程逻辑器件（FPGA、CPLD等）的广泛应用，功能的不断强大，以及快速算法的不断出现，任意波形发生器也向自动化、数字化、高精度化方向发展。

早期的DDS系统使用分离的数字器件搭接,随着整个电路系统运行频率的提高,采用分离器件构建的DDS电路有其自身无法克服的缺点,主要表现在电磁兼容和系统工作频率上。

后来出现的专用DDS芯片极大的推动了DDS技术的发展，但专用DDS芯片价格昂贵，且无法实现任意波形输出，而CPLD 及FPGA的发展为实现DDS提供了更好的技术手段。

FPGA(Field Programmable Gate Array)是目前广泛采用的一种可编程器件,它的应用不仅使数字电路系统的设计非常方便,并且还大大缩短了系统研制的周期,缩小了数字电路系统的体积和所用芯片的品种，它的时钟频率可达到几百兆赫兹,加上它的灵活性和高可靠性,非常适合用于实现波形发生器的数字电路部分。

SummaryWaveform generator is a widely used in electronic circuits, automatic control and scientific experiments in areas such as the signal source. For example, the measurement of electrical parameters, radar, communications, electronic warfare and electronic systems, aerospace and strictly controlling telemetry, etc., in a sense of high-quality signal source is the key to the achievement of performance indicators, The features of many modern electronic devices and systems are directly dependent on the signal source that used in the performance , Therefore, high-quality signal source was described as a large number of electronic systems "heart."With communication, the continuous development of radar, multi-signal sources, frequency stability, spectral purity, frequency range and the number of output frequencies, as well as the shape of the signal waveform to a growing number of requests. In order to improve the signal source output frequency stability, such as crystal oscillator can be used to resolve this issue. In order to meet the requirements of multi-frequency number, frequency synthesis technology can be used, that is, addition and subtraction through multiplication and division of the frequency of operation can be seen from a high stability and high accuracy of the standard frequency source, resulting in a large number of have the same stability and accuracy of different frequencies.The use of DDS technology is the design of a common waveform generator means, DDS not only can produce sine wave at the same time can generate arbitrary wave, this is the manner in which the other frequency synthesizer does not have the characteristics of any wave in all fields have a wide range of applications. Through the DDS arbitrary wave of such methods is a simple, low-cost way to increase the output waveform points can be achieving a high degree of accuracy, by other means this is second to none.Since the 80's from all countries in the development of DDS products, and are widely used in various fields. AD in which the company's products more representative. Such as the AD7008, AD9850, AD9851, AD9852, AD9858 and so on.The system clock frequency ranging from 30MHz to 300MHz, in which the system clock of the AD9858 is reached lGHz. The chips also have the modem function. Such as the AD7008 quadrature modulation signal can be generated, while the AD9852 can also be generated FSK, PSK, amplitude modulation and linear frequency modulation signal. These highly integrated chips, are integrated within the D / A converter, the accuracy of up to 12bit. At the same time have adopted a number of optimization designed to improve performance. because these chips are mostly used in water technology, water technology through the use of the phase accumulator to increase the operating frequency, allowing the output frequency of DDS chip can be further improved. Water through the use of technology in the phase accumulator to ensure that the premise of the operating frequency, the phase accumulator word length can be designed for longer, such as the AD9852 has reached the phase accumulator 48. Models rather than 32 before, so that the output signal of the frequency resolution significantly improved.The use of DDS technology to produce the DDS arbitrary waveform signal generator is a relatively new type of signal source, and has been widely put into use. It is not only capable of producing the traditional function of the signal generator can produce sine, square, triangle wave, sawtooth wave, but also can generate arbitrary waveform editor. Due to the characteristics of the DDS can also be very easy to produce some digital modulation signals, such as FSK, PSK, etc.. Some high-end signal generator can even have a communication signal. At the same time, the frequency resolution of the output waveform, frequency and other indicators of accuracy are greatly improved. HP33120 companies such as HP can generate the lOmHz-15MHz sine and square wave, but also can produce lOmHz-5MHz of arbitrary waveform, but also have the modulation function, can be AM, FM, FSK, Burst, Sweep signal. HP's HP33250 can have the 1uHz-80MHz sine and square wave, resulting in the 1uHz to 25MHz arbitrary waveform. BK PRECISION company level 4070A Arbitrary Waveform function generator sine wave and square wave output frequency DC-21.5MHz, frequency resolution 10mHZ. At the same time, also has AM, FM, PM, SSB, BPSK, FSK, Burst, DTMFGeneration and DTMFDetectionfunction. And have a good machine and the PC interface, the interface can process WINDOWS arbitrary waveform editor.In addition to the application of instruments, DDS in communications systems and radar systems are also very important purposes. DDS can be more easily adopted by some of the commonly used modulation communication signal, such as: frequency shift keying (FSK), binary phase shift keying (BPSK) and Quadrature Phase Shift Keying (QPSK) and so on. DDS can generate two quadrature phase signal strictly in the quadrature modulator and demodulator in a wide range of applications, this is a good local oscillator.In addition with the integrated circuit manufacturing process of gradual improvement through the use of advanced technology and low-power design, digital integrated circuits have a speed greatly improved. Now, its latest operating frequency of the DDS chip can reach 1GHz, so that could have a relatively wide frequency band of the output signal.To further enhance the DDS output frequency, resulting in a lot of DDS technology and other methods of frequency synthesis. Such as when the output signal is a high-frequency narrow-band signal can be used when the method of filtering expansion mixer output DDS, the DDS can also be used to generate high-frequency spectral characteristics of signals, such as the use of high frequency output of the mirror. Can be seen, based on the DDS waveform generator technology to achieve high stability, high accuracy, high-resolution output of the waveform, with frequency switching speed, small size, the characteristics of prices is a very promising signal source. Therefore, the design of this program.In recent years, with programmable logic device (FPGA, CPLD, etc.) a wide range of applications, functions from strength to strength, as well as the continual emergence of fast algorithm, arbitrary waveform generator to the automatic, digital, high-precision of direction. DDS system, the use of early separation of overlapping digital devices, with an operating frequency of the entire circuit system improvement of the separation device used to build the DDS circuit has its own can not overcome the shortcomings, mainly in the electromagnetic compatibility andsystem frequency. Later, there dedicated DDS chip greatly promoted the development of DDS technology, but dedicated DDS chip is expensive, and can not achieve the arbitrary waveform output, and the CPLD and FPGA development for the realization of DDS technology to provide a better means.FPGA (Field Programmable Gate Array) is widely used as a programmable device, which not only makes the application of digital circuit design is very convenient, but also greatly shorten the system development cycle, reducing the size of the digital circuit system and varieties used in the chip, its clock frequency can reach several hundreds Hz, together with its flexibility and high reliability, very suitable for the realization of the digital waveform generator circuit part.1 波形发生器的实现方式波形发生器在生产实践和科技领域中有着广泛的应用。