【正文】 果的分析，在做FPGA設(shè)計(jì)時(shí)，把主要的精力都放在了寫(xiě)代碼本身，而較少的關(guān)注時(shí)序分析的問(wèn)題。但當(dāng)設(shè)計(jì)比較復(fù)雜，運(yùn)行頻率比較高的時(shí)候，不做時(shí)序分析，不加上一些必要的約束，就很難保證設(shè)計(jì)能且穩(wěn)定的運(yùn)行在所設(shè)定的頻率上。第五章 總結(jié)與展望本設(shè)計(jì)對(duì)等精度頻率計(jì)進(jìn)行了系統(tǒng)的設(shè)計(jì)。和傳統(tǒng)的頻率計(jì)相比，利用FPGA設(shè)計(jì)的頻率計(jì)簡(jiǎn)化了電路板設(shè)計(jì)，提高了系統(tǒng)設(shè)計(jì)的實(shí)用性和可靠性，實(shí)現(xiàn)數(shù)字系統(tǒng)的軟件化，這也是數(shù)字邏輯設(shè)計(jì)的趨勢(shì)。特別在周期部分測(cè)量過(guò)程中，由于使用VerilogHDL編寫(xiě)的除法器做除法運(yùn)算時(shí)，只能得到商和余數(shù)，而不能得到二進(jìn)制表示的小數(shù)，因此在后面的顯示時(shí)把余數(shù)給忽略了。此設(shè)計(jì)只能對(duì)15Hz10MHz的頻率進(jìn)行測(cè)量，而不能測(cè)量信號(hào)的占空比，脈寬的測(cè)量。若加入這些功能，若只用FPGA做設(shè)計(jì)就會(huì)顯得相對(duì)復(fù)雜，此時(shí)可用單片機(jī)控制，不僅控制顯示，而且對(duì)FPGA進(jìn)行輸入控制，控制FPGA去完成哪個(gè)測(cè)量。致謝在這里首先要感謝指導(dǎo)老師鄒雪妹老師。從論文選題、實(shí)驗(yàn)仿真到最后論文的撰寫(xiě)，鄒老師都做了悉心的指導(dǎo)，并提出了許多寶貴的建議。其次要感謝論文中參考的參考文獻(xiàn)的作者；感謝對(duì)于提供論文中隱含的上述提及的支持者以及研究思想和設(shè)想的支持者；感謝各大網(wǎng)站平臺(tái)提供的強(qiáng)大的技術(shù)支持。同時(shí)，也向我的家人致以真心的謝意！最后，衷心感謝各位評(píng)閱老師！感謝您們?cè)诎倜χ袇⑴c我的論文評(píng)閱工作。 Communications TutorialFrequency ModulationIntroduction:Frequency Modulation (FM) is a form of modulation in which changes in the frequency of the carrier wave correspond directly with changes in the baseband signal. This is considered an analog form of modulation, because the baseband signal is typically an analog waveform without discrete, digital values. This demo is designed to illustrate the theory behind frequency modulation, and introduce practical aspects of its implementation. Common Applications:FM is most monly used for radio and television broadcasting. In fact, FM radio, which operates from 88 Mhz to 108 MHz, uses FM modulation to transmit audio signals. Each radio station utilizes a 38 kHz frequency band to broadcast audio. Analog television implements FM modulation as well. In fact, television channels 0 through 72 utilize various bandwidths between 54 MHz and 825 MHz. This bandwidth is used for a variety of technologies, also including FM radio.Mathematical Background:The basic principle behind FM modulation is that the amplitude of an analog baseband signal can be represented by a slightly different frequency of the carrier. Mathematically, we will represent this by describing the steps required to modulate the frequency of a sinusoidal carrier.The actual mathematical process to modulate a baseband signal, m(t), onto the carrier requires a two step process. First, the message signal must be integrated with respect to time to get an equation for phase with respect to time, ?(t). This enables the modulation process because phase modulation is fairly straightforward. With typical IQ modulator circuitry. A block diagram description of a FM transmitter is shown below:As the block diagram above illustrates, the integration of a message signal results in an equation for phase with respect to time. This equation is defined by the following equation:Again, the resulting modulation is phase modulation, which involves changing the phase of the carrier over time. This process is fairly straightforward and requires a quadrature modulator, shown below:Demonstration:The following demonstration will introduce more practical aspects of frequency modulation and will examine the affect of the carrier frequency and FM deviation on the resulting FM signal. 1) First, open the example “FM ” and run the program. Notice that there are three basic parameters that we will adjust. First, the ‘Baseband Frequency’ adjusts the frequency of the message signal that we desire to send. Second, the Carrier Frequency is the frequency which we will utilize to carry our message signal. Finally, the FM Deviation determines the frequency difference between the greatest instantaneous frequency of the modulated signal and the carrier frequency. In this step, adjust the baseband frequency and observe the affect on the graph entitled FM modulated Wave.2) Next, we will experiment with the carrier frequency and observe the affect on modulated FM signal. Notice, that the minimum carrier frequency is equivalent to the frequency of the baseband. In addition, the frequency deviation is also automatically adjusted so that it is never greater than the carrier frequency. Below, we show a scenario where the carrier frequency is equal to the frequency of the baseband. Because these frequencies are identical, the modulated FM signal is not purely sinusoidal.As the image above illustrates, the baseband signal cannot be well represented in this scenario. Ideally, the carrier frequency should be substantially greater than the frequency of the baseband signal. In the graph below, we show the results of increasing the carrier frequency. Here, you can see that the full period of each frequency is represented. 3) Finally, we will observe the affect of the modulation index on the FM signal. To do this, adjust the carrier frequency to its maximum, 1 MHz. You will notice that the maximum FM Deviation has now automatically been adjusted to 500 kHz. Slide the FM Deviation slider to the maximum, 500 kHz and observe the results. As you can see in the graph below, that the frequency of the resulting time domain signal shows substantial variation. In fact, as the graph illustrates, the minimum level of the baseband signal are represented by 0 Hz. In addition, the maximum level of the baseband signal is represented by 2 MHz. While significant FM deviation is visually obvious, smaller FM deviation values are not. To observe this, change the FM deviation to 200 kHz. At this setting, various levels of the baseband signal will be represented by frequencies ranging from 800 kHz to MHz. The time domain of the modulated waveform is shown below:As the graph above, changes in the frequency deviation is less obvious in the time domain. However, it is important to observe its affect on a munications system. Ideally, a munications system should have a maximum frequency deviation to more accurately represent the baseband signal. However, this is not without tradeoffs. By increasing the frequency deviation, we also increase the power required to generate the signal and the frequency bandwidth that it occupies.4) Finally, click on the “Frequency Domain” tab to view an FFT power spectrum of the modulated signal