Radio Frequency Transmitters and Receivers - Assignment Example

Radio Frequency Transmitters and Receivers Task 1 Question 1 a. b. Modulation is the process of transmitting low frequency information at high frequencies by varying its characteristics such as frequency, phase angle and amplitude. The process of modulation involves utilisation of various components that includesOscillator/ frequency generator, Power Amplifier, modulator and power supply (Raab, 820). Microphone The microphone has its use in conversion of sound signals to electrical signals in the transmitter. A microphone receives the sound signals from the source and converts it into electrical signals. Modulator The modulator facilitates in the modulation of the audio signal into the radio frequency carrier. Generally, the audio signal from the microphone is modulated to radio frequency carrier at the modulation stage. Frequency Generator The frequency generator, also known as the oscillator, provides the radio frequency transmitter with the appropriate operating frequency. The signal generator determines the frequency that the transmitter operates on throughout the transmission process. RF Power Amplifier Power amplification is the final stage of the radio frequency signal transmission process. The power amplifier strengthens the radio frequency to enable long distance transmission through the channel.Transmission of the radio frequency over long distances requires strong signals of since it is difficult to transmit weak signals over long distances. Antennae The role of the antennae is to convert electrical signals to magnetic signals. Question 2 Simulink screen shots Am signal Modulated signal Demodulated signal The frequency of the detected signal is less than the frequency of the message signal. The reduction in the measurement of the simulation frequency and the message signal frequency is because of errors in detecting the signal. Question 3 The figure represents a single frequency wave implying that a single sine wave modulation signal is used. The evaluation of the upper sideband is done by use of the following formula; fupper Side Band=fcarrier frequency+fmessage frequency. On the other hand, the lower Side frequency has its calculation using the formula; fcarrier frequency-fmessage frequency. This implies that: \ FLSB=fc-fm=10,000Hz-150Hz=9850Hz Hence fLSB=9.85 KHz Also, fUSB=fc+fm=10,000Hz+150Hz=10,150HZ Hence, fUSB=10.15 KHz Mathematical formulation method is used in locating the lower sideband frequency signal.Quadratic modulation of amplitude mathematical form is used to represent different sidebands in a radio frequency as shown below. sssb(t)=s(t).cos(2πf0t)-ŝ(t).sin (2πf0t), where, s(t) is the message, ŝ(t) ,the message’s Hilbert transformsand f0 is the carrier of the radio frequency. After expansion, the final equation obtained is: Sssb(t)=s(t).Cos(2πf0t0-ŝ(t). Sin (2πf0t) The lower sideband is removed mathematically by use of an idealised band pass filter. Task 2 Question 1 a. b. In the frequency modulating signals (FM), the carrier combines with the modulating signal hence causing the frequency of the resulting to vary with respect to the variation of the modulating signal’s instantaneous amplitude. The frequency modulation signals go through the following stages: speech amplification, modulation, oscillation, frequency multiplication and power amplification. The microphone receives the audio signals from the source and converts them to electrical signals. The microphone functions opposite of the functionality of the speakers. It picks ups sound or audio signals and converts them to voltages. The electrical signals from the microphone go through the speech amplifier. The purpose of the speech amplifier is to increase the strength of the signals before the modulation process. The amplified signals pass to the modulator where signal modulation takes place (Raab, 823). Frequency modulation facilitates the cancellation of natural noise from the signal. Generally, signal modulation removes distortions from the signals for effective transmission. After modulation, the signal goes on to the oscillator. The oscillator facilitates in determination of the final frequency of the signal for transmission. The oscillator generates frequencies that suit the speech signal to obtain the best frequency for transmission. The multiplier multiplies the signals for effective transmission. The power amplifier stimulates strength increment in the multiple signals for the final phase of transmission. The antennae convert the electrical signals to magnetic signals. Question 2 Simulink Screen Shots ᵝ=5 ᵝ=2 ᵝ=8 b.The modulation is directly proportional to the amplitude of the signal. When the modulation index is at |5| dB, the amplitude of the frequency is smaller as compared to the signal amplitude obtained when the modulation index is |8| dB. However, a reduction in the modulation index to |2| dB leads to a reduction in the size of the signal amplitude. The frequency of the signal also changes with respect to the change in the level of modulation index. When the modulation index is |5| dB, the frequency of the signal is smaller as compared to the frequency obtained when the modulation index is increased to |8| dB.Moreover, the signal frequency is smaller at the instance when the modulation index is |2| dB as compared to the frequency obtained when the modulation frequency is |5| dB. Task 3 a. b.The antennae receive the signals from the broadcasting house. The antenna acts as a transducer since itintercepts some of the electromagnetic waves power and produces small voltages at its terminals. The small voltages form the antennae passes on to the radio frequency amplifier. The radio frequency amplifier amplifies the tiny voltages intercepted by the antenna. The main purpose of the antenna is to intercept the electromagnetic waves from the broadcasting station and converting it into small voltages.Consequently, the function of the radio frequency amplifier is to amplify the output of the antennae. The oscillator’s frequency is easily tunes over a given range. In a radio receiver, the purpose of the oscillator is to control the frequency range under which the receiver operates. The multiplier multiplies signals from the oscillator as well as that coming from the radio frequency amplifier, which enhances the filtration process. The signals go to the filter whose main purpose it eliminate the unwanted frequencies in the signal. The frequencies of the signal intercepted by the antennae contain high levels of distortion because of the environmental noise. The filter has a purpose to remove distortion of the signal because of the presence of unwanted frequencies.After filtration, the clean signal passes on to the detector. The detector’s role is to recover the information in the modulated electromagnetic radio wave.The detector detects availability or unavailability of the radio signals in the receiver.The detector then produces clicks to the audio amplifier. The audio amplifier increases the gain of the detected signals and passes them to the speaker, which is the output device. Task 4 b). Antenna and RF Amplifier The signals enter the receiver circuitry through the antennae. The antenna intercepts the electromagnetic signals and converts them into small voltages. The small voltages are kept at the bottom of the antenna where the radio frequency amplifier amplifies them. The radio frequency amplifier accepts only the relevant signals and rejects all the unwanted signals from the antenna. The radio frequency amplifier works in conjunction with the oscillator to ensure selection of the appropriate signals. The radio frequency amplifier also performs the role of amplifying the small signals from the antenna. The level of amplification at the RF stage is selected keenly to avoid overloading of the mixer due to the presence of strong signals. The amplification process ensures sufficient amplification of the signals to achieve effective signal noise ratio (Stagner, 1465). Mixer The mixer combines the amplified signals from the local oscillator and the RF amplifier.This is acrucial process part since it determines the performance of the other components in the superheat. The output of the mixer should be linear to avoid generation of spurious signals. Local Oscillator The local oscillator contains comprises of a frequency oscillator that is variable and is tuned by use of a capacitor that is variable. A frequency synthesizer is also utilised in the place of variable frequency oscillator for higher levels of stability and accuracy. IF Amp, IF block The ‘IF,’ stages ensures that the signals from the mixer are separated in with respect to their frequencies. The filter classifies signals with a particular frequency into a given group while those with different signals are classified into another group. Detector, Audio Amplifier The purpose of the detector is to identify the radio frequencies from the ‘IF’ output and transfer them to an audio amplifier, which then amplifies the signals for the output speaker. Task 5 The transmitter and the receiver arrangements on the circuit board depend on the functionality of the system, which is to utilise the two systems. A system that utilises both the transmitter and the receiver works towards ensuring optimum results in both. The arrangement of the transmitter, as well as the receiver, should ensure maximum sensitivity of the receiver and increase the output of the receiver. Thearrangement should ensure that the transmitter produces the highest output while the receiver achieves highest sensitivity levels. The transmitter output signal should be improved to ensure maximum output power. On the other hand, the input circuit of the receiver should be improved to enhance its sensitivity.Improvement of the transmitter, as well as the receiver, ensures maximum efficiency of the system. Improper arrangement of the receiver and the transmitter in radio stations causes distortion of the signals, which results in poor reception as well as transmission levels. The circuit board arrangement of the receiver, as well as the transmitter,is effectively. The output of the receiver becomes the transmitter’s input. In this case, the transmitter input is optimum since it is the amplified signal of the receiver. By placing the receiver before the transmitter in a circuit board, the transmitter input is optimum while the sensitivity of the receiver is kept at high levels (Günther). Works Cited Raab, Frederick H., et al. "Power amplifiers and transmitters for RF and microwave." Microwave Theory and Techniques, IEEE Transactions on 50.3 (2002): 814-826. Kumar, Chatterjea Prafulla, and Houghton Leslie Wilfred."Radio communication system." U.S. Patent No. 2,462,069. 22 Feb. 1949. Stagner, Colin, et al. "A practical super heterodyne-receiver detector using stimulated emissions." Instrumentation and Measurement, IEEE Transactions on 60.4 (2011): 1461-1468. Günther, Peter Uwe, and Jörg-Reinhardt Kropp. "Opto-electrical module for optical signals from at least two optical data channels for arranging on a main circuit board of a component assembly and opto-electrical component assembly." U.S. Patent No. 7,347,634. 25 Mar. 2008. Read More