Info Llt
0 2 4 6 8 10 12 14 Drain-to-source voltage v vj Figure P3.2. 0 2 4 6 8 10 12 14 Drain-to-source voltage v vj Figure P3.2. 3.9 An AM signal applied to an envelope detector has carrier frequency oc 250krad s. The upper envelope is a triangular waveform which goes from 10V to 2V and back up to 10 V at a constant rate in 0.2 ms the lower envelope is similar . Assuming that the diode is ideal, calculate the maximum time-constant of the detector load to avoid diagonal clipping. Justify any...
The Radiofrequency Amplifier
The choice of an amplifier to boost the power coming out of the modulator to the level required to drive the antenna can be made when the following points have been considered 1 The amplifier must be linear so as to preserve the nature of the modulated signal. 2 The output power of the amplifier can vary from a few watts to hundreds of kilowatts. 3 A high conversion efficiency is a necessity when high power is a requirement. The portion of the dc power supplied to the amplifier which is not...
Id
Figure 9.11. A combination of the series and shunt sampling gates improves performance. 9.3.2.5 Operational Amplifier Sampling Gate. The circuit is shown in Figure 9.12. The operational amplifier is connected to give a gain of R2 R1 when the transistor is in the off state. When the transistor is on, R2 is short-circuited and the gain is reduced to unity. 9.3.2.6 Multiplier Sampling Gate. A PAM sampler can be seen as a multiplication of the analog signal and a train of pulses. The process is...
Shortwave Radio
Frequencies between 3 MHz and 30 MHz are set aside for use in long distance radio communication. This frequency band is generally referred to as the short-wave band. The wavelength that lies between 1 m and 100 m is short compared to that of the medium wave. It was pointed out in Section 2.9 that the increased frequency of the carrier used in short-wave communication gives its electromagnetic transmission wave increasingly directional properties. Transmission antennae can be designed to...
Component Design
An important point to remember is that an antenna is a reciprocal device, that is, it can be used both for transmitting signals as well as for receiving them. An antenna structure that produces a good ground wave radiation pattern will have a good response to the same ground wave radiation when used in the receiving mode. Commercial FM receivers commonly use two types of antennas the vertical whip antenna, most commonly used with automobile radios, and the dipole and folded dipole antennas used...
Frequency Modulation Theory
While a saw-tooth modulating signal provides a simple picture of the FM signal, a sinusoidal modulating signal is the simplest for the derivation of the mathematical expressions to describe the FM signal. Figure 4.1. The sawtooth waveform vs frequency modulates a carrier to give the output vfm. Note that the relative change in frequency has been exaggerated for clarity. In normal FM radio, the change in frequency relative to the carrier is less than 0.15 Figure 4.1. The sawtooth waveform vs...
Problems Mvh
8.1 Describe the attractive features of the carbon microphone that make it well suited to the telephone system. A carbon microphone has a static resistance of 75 O and it is connected in series with a 12 V battery and a load resistor R. A sound wave impinging on the microphone causes a sinusoidal variation of the microphone resistance with a peak value equal to 15 of the static value. What is the value of the load resistor R if the second harmonic component of the current is 7.5 of the current...
Access Techniques
11.3.1 Multiplex and Demultiplex Revisited When modulation is used to accommodate a number of signals on a single channel we refer to it as multiplexing. Figure 11.2 shows five baseband signals, each of which occupies the frequency band 300 Hz to 3 kHz. By choosing suitable carrier frequencies for each one, they may be transmitted over the same cable or the airwaves by radio and subsequently demodulated with no interference between them. When different carrier frequencies are used to multiplex...
Info Bnv
Figure 5.4. a The phasor diagram when signal frequency is lower than carrier frequency. b The phasor diagram when signal frequency is higher than carrier frequency. Figure 5.4. a The phasor diagram when signal frequency is lower than carrier frequency. b The phasor diagram when signal frequency is higher than carrier frequency. Replacing R2 in Equation 5.2.7 by Z2 gives It is evident that V1 and V2 are no longer at right angles to each other. The angle between them depends on the magnitude and...
E3 The Clocked Sr Flipflop
A flip-flop is normally a part of a much larger system of gates. Each gate takes a finite amount of time to change its state so there is no guarantee that the two inputs S and R of a flip-flop will arrive simultaneously or whether one will arrive before the other. For example, because of delays in their respective paths, suppose S 0 and R 1 and they are both supposed to change states simultaneously, then if S arrived a little ahead of R, we would momentarily have S 1 and R 1 an unacceptable...
E2 Basics Of Sr Flipflop Circuits
Figure E.1 a shows the NOT gate non-resettable equivalent of the flip-flop, b shows the resettable equivalent using NOR gates and c shows a second realization using NAND gates. In the flip-flop circuit shown in Figure E.1 b , the S and R terminals are the control inputs. Q and Q are the outputs and they are complementary that is when one of them is a 1 the other must be a 0 . There are four different combinations of 1s and 0s that can exist at the terminals S and R. 1a If we assume that S R 0...
Etacs
Channel bandwidth 30 kHz 25 kHz Traffic channel per RF channel 1 1 Reverse channel Forward channel Peak deviation voice channels control wideband data Data rate on control wideband channel 10 kbps 8 kbps Number of channels 832 1000
Converting the ClassC Amplifier into a Frequency Multiplier
To convert a class-C amplifier into a frequency multiplier with a multiplication factor of 2, the L and C of the tank circuit are chosen to resonate at 2oo when the input signal frequency is fflo. Successful operation of the system demands that the Q factor Figure 2.22. The output waveform of a class-C amplifier after a single pulse excitation. Note the sinusoidal waveform and the exponential decay of the envelope. Figure 2.22. The output waveform of a class-C amplifier after a single pulse...
Info Bym
Figure 5.1. The block diagram of the domestic FM receiver showing frequency ranges and bandwidths. Figure 5.1. The block diagram of the domestic FM receiver showing frequency ranges and bandwidths. interfering signals and noise takes place. The filtered signal then proceeds to the amplitude limiter. The need for the limiter becomes evident when one recalls that the FM signal is usually converted into an AM signal in the discriminator before it is detected. This means that any variation in the...
References Pch
1. Foster, D. E. and Seeley, S. W., Automatic Tuning Simplified Circuits and Design Practice, Proc. IRE., 25, 289, 1937. 2. Seeley, S. W., Radio Electronics, McGraw-Hill, New York, 1956. 3. Seeley, S. W. and Avins, J., ''The Ratio Detector'', RCA Review, 8, 201, 1947. 4. Best, R. E., Phase-Locked Loops, McGraw-Hill, New York, 1984. 5. DeFrance, J. J., Communication Electronics Circuits, 2nd Ed., Rinehart Press, San Francisco, 1972. 6. Stark, H. and Tuteur, F. B., Modern Electrical...
Stereophonic Fm Transmission
In an effort to create a realistic sound presentation from recorded music, two microphones are used, one to record the sound as it is perceived on the right side and the second on the left side. During playback the right- and left-hand side signals have to be fed to the right- and left-hand side loudspeakers, respectively. The listener sitting in front of the speakers can distinguish the sounds of the different instruments as coming from their proper positions when the music was recorded. When...
The Paging System
There are a number of occupations in which the professional has to move around from one job to the next and essentially is almost never available at a wireline telephone. The paging system is designed to receive and store information until the professional is ready to read it. They are most commonly used by home appliance servicemen, office equipment servicemen, doctors, photographers, and in the last few years they have become very popular with teenagers. Different paging systems have varying...
Info Vtw
Example 4.4.2 The Integrator. Design an integrator to satisfy the following specifications 3 What is the gain at 10 Hz and 15 kHz Solution. The required response is as shown in Figure 4.21. The relationship between two frequencies f1 and f on the basis of decades of frequency is given by where n is the number of frequency decades. When f 10 Hz and f 1kHz, n 2. The gain at 10 Hz 2 x 20 dB 40 dB. The voltage gain of 40 dB corresponds to a voltage ratio of 100. Therefore, R2 R1 100. Choosing R2 1...
Info Ybm
Other larger groups can be formed, for example 6 mastergroups may be combined to form a jumbogroup with 3600 voice channels. To recover the original baseband signals from the various groups, the appropriate number of filtering demodulation processes will have to be carried out. At each stage of the demodulation process, the correct carrier will have to be reinstated for this to be possible. In FDM, voice signals were ''stacked'' in the frequency spectrum so that many such signals could be...
Design A Ce Circuit
When Equation 2.7.3 is plotted on the characteristics of the device shown in Figure 2.37 it gives a straight line with a slope equal to 1 Rc and intercepts on the y axis equal to Vcc Rc and on the x axis equal to Vcc. This line is known as the load line and determines the behavior of the device when it is connected to the collector load, Rc, and the supply voltage Vcc. Because the current in a class-A amplifier flows for the entire 2p radians of the input ac cycle, its analysis depends on a...
Generation Of Fm Block Diagram
Figure 4.11. The use of a double-tuned circuit provides increased dynamic range and improves the linearity by balancing the non-linearity of one LC circuit with the other. Note that the push-pull arrangement shown here will generate predominantly odd harmonics. vfm t A sin oct mf sin ost cos oct 4.4.4 vfm t Afsin oc t 1 mf sin oc os t sin oc os t . 4.4.5 It should be noted that the above approximation eliminates all the sidebands except the two closest to the carrier. The modulation is then...
Frequency Multiplier
The purpose of the frequency multiplier is to raise the frequency generated by the crystal-controlled oscillator to the value required for the transmitter carrier. As explained earlier, it is not possible to obtain physically robust crystals at high Figure 2.20. a A Hartley oscillator with one of the inductors replaced by a crystal. This circuit is called a Pierce oscillator. The field-effect transistor may be replaced by any other suitable active device. b The equivalent circuit of the Pierce...
Introduction Vtg
In amplitude modulation, the frequency of the carrier is kept constant while its amplitude is changed in accordance with the amplitude of the modulating signal. In frequency modulation, the amplitude of the carrier is kept constant and its frequency is changed in accordance with the amplitude of the modulating signal. It is evident that, if a circuit could be found which will convert changes in frequency to changes in amplitude, the techniques used for detecting AM can be used for FM as well....
Twistedpair Cable
This consists of two insulated wires twisted together to form a pair. Several to many hundred pairs may be put together to form a cable. When this is done it is usual to use different pitches of twist in order to limit electromagnetic coupling between them and hence cross-talk. The conductor material is copper, usually numbers 19, 22, 24, and 26 American Wire Gauge AWG , and the insulation is usually polyethylene. Wax-treated paper insulation was used in the past but the ingress of moisture...
I V I V
The current flowing in each transistor is a half-sinusoid whose average value dc equivalent is c p. The average current for the two transistors is 2 c p. Since this current is flowing against a potential difference of Vcc, the dc power input is The complementary symmetry class-B amplifier has the following disadvantages 1 It requires two equal dc power supplies. 2 Complementary pairs of transistors are not easy to manufacture, especially at high power levels. 3 The circuit cannot have a voltage...