T DONT NO
This article described the three directions (before, left, right) ultrasonic ranging system is to understand the front of the robot, left and right environment to provide a movement away from the (Similar to GPS Positioning System) A principle of ultrasonic distance measurement 1, the principle of piezoelectric ultrasonic generator Piezoelectric ultrasonic generator is the use of piezoelectric crystal resonators to Ultrasonic generator, the internal structure as shown in Figure 1, it has two piezoelectric chip and a resonance When it's two plus pulse signal, the frequency equal to the intrinsic piezoelectric oscillation frequency chip, the chip will happen piezoelectric resonance, and promote the development of plate vibration resonance, ultrasound is Conversely, if the two are not inter-electrode voltage, when the board received ultrasonic resonance, it will be for vibration suppression of piezoelectric chip, the mechanical energy is converted to electrical signals, then it becomes the ultrasonic 2, the principle of ultrasonic distance measurement Ultrasonic transmitter in a direction to launch ultrasound, in the moment to launch the beginning of time at the same time, the spread of ultrasound in the air, obstacles on his way to return immediately, the ultrasonic reflected wave received by the receiver immediately stop the Ultrasound in the air as the propagation velocity of 340m / s, according to the timer records the time t, we can calculate the distance between the launch distance barrier (s), that is: s = 340t / 2 Ultrasonic Ranging System for the Second Circuit Design System is characterized by single-chip microcomputer to control the use of ultrasonic transmitter and ultrasonic receiver since the launch from time to time, single-chip selection of 8751, economic-to-use, and the chip has 4K of ROM, to facilitate Circuit schematic diagram shown in Figure Draw only the front range of the circuit wiring diagram, left and right in front of Ranging Ranging circuits and the same circuit, it is 1,40 kHz ultrasonic pulse generated with the launch Ranging system using the ultrasonic sensor of piezoelectric ceramic sensors UCM40, its operating voltage of the pulse signal is 40kHz, which by the single-chip implementation of the following procedures to puzel: mov 14h, # 12h; ultrasonic firing continued 200ms here: cpl 0; output 40kHz square wave nop; nop; nop; djnz 14h, here; ret Ranging in front of single-chip termination circuit P0 input port, single chip implementation of the above procedure, the P0 port in a 40kHz pulse output signal, after amplification transistor T, the drive to launch the first ultrasonic UCM40T, issued 40kHz ultrasonic pulse, and the continued launch of Ranging the right and the left side of the circuit, respectively, then input port P1 and P2, the working principle and circuit in front of the same 2, reception and processing of ultrasonic Used to receive the first launch of the first pair UCM40R, the ultrasonic pulse modulation signal into an alternating voltage, the op-amp amplification IC1A and after polarization IC1B to IC IC2 is locked loop with audio decoder chip LM567, internal voltage-controlled oscillator center frequency of f0 = 1/1R8C3, capacitor C4 determine their target R8-conditioning in the launch of the carrier frequency on the LM567 input signal is greater than 25mV, the output from the high jump 8 feet into a low-level, as interrupt request signals to the single-chip Ranging in front of single-chip termination circuit output port INT0 interrupt the highest priority, right or left location of the output circuit with output gate IC3A access INT1 port single-chip, while single-chip P3 and P 4 received input IC3A, interrupted by the process to identify the source of inquiry to deal with, interrupt priority level for the first left right Part of the source code is as follows: receive1: push psw push acc clr ex1; related external interrupt 1 jnb 1, right; P1 pin to 0, ranging from right to interrupt service routine circuit jnb 2, left; P2 pin to 0, to the left ranging circuit interrupt service routine return: SETB EX1; open external interrupt 1 pop? acc pop? psw reti right: ?; right location entrance circuit interrupt service routine ? Ajmp? Return left: ; left Ranging entrance circuit interrupt service routine ? Ajmp? Return 4, the calculation of ultrasonic propagation time When you start firing at the same time start the single-chip circuitry within the timer T0, the use of timer counting function records the time and the launch of ultrasonic reflected wave received When you receive the ultrasonic reflected wave, the receiver circuit outputs a negative jump in the end of INT0 or INT1 interrupt request generates a signal, single-chip microcomputer in response to external interrupt request, the implementation of the external interrupt service subroutine, read the time difference, calculating the distance Some of its source code is as follows: RECEIVE0: PUSH PSW PUSH ACC CLR EX0; related external interrupt 0 ? MOV R7, TH0; read the time value MOV R6, TL0? CLR C MOV A, R6 SUBB A, # 0BBH; calculate the time difference MOV 31H, A; storage results MOV A, R7 SUBB A, # 3CH MOV 30H, A? SETB EX0; open external interrupt 0 POP ACC? POP PSW RETI Fourth, the ultrasonic ranging system software design Software is divided into two parts, the main program and interrupt service routine, shown in Figure 3 (a) (b) (c) Completion of the work of the main program is initialized, each sequence of ultrasonic transmitting and receiving Interrupt service routines from time to time to complete three of the rotation direction of ultrasonic launch, the main external interrupt service subroutine to read the value of completion time, distance calculation, the results of the output and so V CONCLUSIONS Required measuring range of 30cm ~ 200cm objects inside the plane to do a number of measurements found that the maximum error is 5cm, and good Single-chip design can be seen on the ultrasonic ranging system has a hardware structure is simple, reliable, small features such as measurement Therefore, it can be used not only for mobile robot can be used in other detection Thoughts: As for why the receiver do not have the transistor amplifier circuit, because the magnification well, CX20106 integrated amplifier, but also with automatic gain control level, magnification to 76dB, the center frequency is 38k to 40k, is exactly resonant ultrasonic sensors frequency
T DONT NO
答案是是2/3。
自己去百度文库找！什么资料都有！
The MWC can operate with as few as p = 2N channels and with a sampling rate fs = 1/T > B on each channel,so that it approaches the minimal rate of 2NB Advanced configurations enable additional hardware savings bycollapsing the number of branches p by a factor of q at the expense of increasing the sampling rate of each channelby the same factor [109] The choice of periodic functions pi(t) is flexible: The highest Dirac frequency needsto exceed In principle, any periodic function with high-speed transitions within the period T can satisfythis One possible choice for pi(t) is a sign-alternating function, with M = 2L + 1 sign intervalswithin the period T [109, 161] Imperfect sign alternations are allowed as long as periodicity is maintained [9]This property is crucial since precise sign alternations at high speeds are extremely difficult to maintain, whereassimple hardware wirings ensure that pi(t) = pi(t + Tp) for every t 2 R The waveforms pi(t) need low mutualcorrelation in order to capture different mixtures of the Popular binary patterns, , the Gold or Kasamisequences, are especially suitable for the MWC [161] Another important practical design aspect is that the lowpassfilter h(t) does not have to be A nonflat frequency response can be compensated for in the digital domain,using the algorithm developed in [162]
你可以在google 学术里去搜索你要的论文，你可以把你想要搜的关键词翻译成英文的，然后在google学术里搜索，有些是可以下载的！因为我经常用!希望被采纳！
最低工资委员会的操作数=2渠道和采样率=1财政司司长/>对每个通道，所以它的方法的最小速度2nb。先进的配置使附加硬件储蓄所倒塌的分行数目的一个因素，问为代价的增加，每个通道采样率由同一因素[ 109]。选择周期函数皮（吨）是灵活的：最高的狄拉克频率超过25。原则上，任何周期函数与高速内过渡的时期可以满足这一要求。一个可能的选择皮（吨）是一个注册交替作用，米=2+ 1符号间隔在期[ 109，161 ]。不完美的标志还允许只要维持周期是[ 9 ]。此属性是至关重要的准确标志交替高速度是极难维持，而简单的硬件接线确保皮（吨）=π（吨+普瑞尔）每2R波形皮（吨）需要低相互相关为了捕捉不同的混合物的光谱。流行的二进制模式，例如，黄金或kasami序列，尤其适用于康复[ 161]。另一个重要方面是，低通滤波器的实用设计过滤器小时（吨）不一定是理想的。一个非平坦的频率响应可以补偿在数字域，使用方法[ 162]。
您可以亲自挑选：可以用关键词检索或根据专业、杂志名检索。标题前面有个绿色的小方块的文章可以浏览全文。参考资料：
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我刚好也这专业的我记得有一个什么论文网 全是PDF格式的论文 好像新注册可以免费下载5篇的 毕竟久了 记不太清什么网你慢慢找吧 那里文献很多
在上面找到的都是你自己可以完成的，建议还是直接找别人写一篇比较保险！我和我同学找的是脚印代写论文写的，用支付宝担保交易很有保障，并且现在论文过了，所以才推荐给你，建议去看看，百度一下就知道了
你可以在google 学术里去搜索你要的论文，你可以把你想要搜的关键词翻译成英文的，然后在google学术里搜索，有些是可以下载的！因为我经常用!希望被采纳！
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