Có 20+ tài liệu thuộc chủ đề "truyền thông không gian"
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Scientists and mathematicians of the nineteenth century laid the foundation of telecommunication and wireless technology, which has affected all facets of modern society. Interested readers may ®nd an excellent reference on the historical developments of radio frequencies (RF) and microwaves in the IEEE Transactions on Microwave Theory and Technique (Vol. In the case of a single audio channel, the information...
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A microwave signal arriving at antenna A works as input to port 1 of the circulator. This frequency conversion facilitates ampli®cation of the signal economically. A band-pass ®lter is used at the output of the mixer to stop undesired harmonics. The size of the antenna can be smaller (3 feet or even smaller with higher- power satellites) against 8 to...
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This chapter begins with an introduction to line parameters and a distributed model of the transmission line. Solutions to the transmission line equation are then constructed in order to understand the behavior of the propagating signal. Finally, the Smith chart is introduced to facilitate graphical analysis and design of transmission line circuits.. 3.1 DISTRIBUTED CIRCUIT ANALYSIS OF TRANSMISSION LINES Any...
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Further,resonant circuits are an integral part of the frequency-selective ampli®er as well as of the oscillator designs. Since the inductive reactance is directly proportional to signal frequency,it tries to block the high-frequency contents of the signal. This frequency is called the resonant frequency of the circuit. It can be analyzed as follows.. Therefore,the transfer function of this circuit has a...
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As shown in Figure 5.1, impedance matching networks are employed at the input and the output of an ampli®er circuit. Figure 5.1 Block diagram of an ampli®er circuit.. The real part of the normalized impedance (or the normalized admittance) becomes unity at certain points on the line. Figure 5.2 Transmission line with a shunt matching element.. The imaginary part of...
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Further, it may be necessary in certain cases to keep the re¯ection coef®cient below a speci®ed value over a given frequency band. Matching bandwidth can be increased at the cost of a higher re¯ection coef®cient. Multisection binomial transformers exhibit almost ¯at re¯ection coef®cient about the center frequency and increase gradually on either side. Chebyshev transfor- mers can provide even wider...
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Z 11 Z 12 Z 21 Z 22. Similarly, with a source connected at port-2 while port-1 is open circuit, we ®nd that Z 12 V 1. Similarly, when the source is connected at port-2 and port-1 has an open circuit, we. As before, assume that the source is connected at port-1 while port-2 is open. Similarly, with a...
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Figure 8.1 A two-port network with terminations.. Transfer characteristics of the network can be formulated as follows. The frequency response of the designed circuit is shown in Figure 8.3. Figure 8.3 Frequency response of the T-section shown in Figure 8.2.. Figure 8.4 Image impedance of the constant-k ®lter of Figure 8.2 as a function of frequency.. Figure 8.5 A constant-k...
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A signal-¯ow graph is a graphical means of portraying the relationship among the variables of a set of linear algebraic equations. Associated terms are de®ned in this chapter along with the procedure to draw the signal-¯ow graph for a given set of algebraic equations. The manipula- tion of signal-¯ow graphs is summarized to ®nd the desired transfer functions.. Nodes or...
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10.1 STABILITY CONSIDERATIONS. Condition (10.1.3) can be rearranged as follows:. we ®nd that (10.1.10) is satis®ed if 1. Adding (10.1.13) and we get. From (10.1.6) and we have. Multiplying (10.1.13) and we get. Figure 10.2 A graphical representation of (10.1.7).. From (10.1.16) and we get. Figure 10.3 Input and output stability circles for Example 10.1.. 10.2 AMPLIFIER DESIGN FOR MAXIMUM...
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11.1 FEEDBACK AND BASIC CONCEPTS. Figure 11.1 A simple feedback system.. Figure 11.2 A schematic oscillator circuit.. Figure 11.3 An electrical equivalent of the schematic oscillator circuit.. Equation (11.1.10) represents the most general formulation. ®rst column will be removed from (11.1.10).. From (11.1.21) and (11.1.23),. Figure 11.4 illustrates the RF sections of these two circuits (excluding the transistor's. Figure 11.4...
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Hertz demonstrated radio frequency (RF) generation, propagation, and reception in the laboratory. Marconi's wireless communications using the telegraph meant that a ship was no longer isolated in the open seas and could have continuous contact to report its positions. In the early 1900s, most wireless transmission occurred at very long wavelengths.. In the 1920s, the one-way broadcast was made to...
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At low RF, a wire or a line on a printed circuit board can be used to connect two electronic components. They can be classi®ed into two categories: conventional and integrated circuits. They can be used for wired communications to connect a transmitter to a receiver (Cable TV is an example).. FIGURE 2.2 The currrent distribution within a wire operating...
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The antenna is a key component in any wireless system, as shown in Fig. FIGURE 3.1 Typical wireless system.. FIGURE 3.2 Various antennas [2].. If the source transmitting power is P t , the power density P d in watts per square meters at a distance R from the source can be calculated by. At a distance far from the...
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Various Components and Their System Parameters. Figure 4.1 shows a brief history of microwave technologies. These components can be represented by the symbols shown in Fig.. FIGURE 4.1 History of microwave techniques: (a) technology advancements. FIGURE 4.2 Symbols for various components.. A directional coupler is a four-port device with the property that a wave incident in port 1 couples power...
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The input signal to the receiver is in the frequency range of 20–470 MHz. Other receiver examples are shown in Fig. Most components shown in Figs. This chapter will discuss the system parameters of the receiver.. The performance of the receiver depends on the system design, circuit design, and working environment. For the output signal to be useful, the signal...
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Figure 6.1 shows a typical transmitter block diagram. The output signal could be upconverted to a higher frequency.. The power amplifiers are used to increase the output power before it is transmitted by an antenna. To have a low phase noise, the oscillator or local oscillator can be phase locked to a low-frequency crystal oscillator. Power output and operating frequency:...
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The nature of an echo signal provides information about the target—range, direction, and velocity.. Although radar cannot reorganize the color of the object and resolve the detailed features of the target like the human eye, it can see through darkness, fog and rain, and over a much longer range. It can also measure the range, direction, and velocity of the...
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Three such satellites can provide services covering all major population centers in the world. Wireless personal and cellular communications have enjoyed the fastest growth rate in the telecommunications industry. The received power is P r and the distance is R. The received power can be calculated in the following if we assume that there is no atmospheric loss, polarization mismatch,...
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The lower frequency is called the modulating signal, the higher frequency signal is called the carrier, and the output signal is called the modulated signal. The benefits of the modulation process are many, such as enabling communication systems to transmit many baseband channels simultaneously at different carrier frequencies without their interfering with each other. Some simple modulation can be achieved...