M S Engineering College,

Transcription

1 M S Engineering College (ISO , Affiliated to VTU, Belgaum) International Airport Road,NavarathaAgrahara, Sadahlli P.O, Bangalore ADVANCED COMMUNICATION MANUAL (10ECL67) Department of Electronics and communication Engineering Prepared By Azra Jeelani MTech, (PhD),Associate Professor M S Engineering College, Bangalore Natya.S MTech, Assistant Professor M S Engineering College, Bangalore Pavithra.S.G MTech, Assistant Professor M S Engineering College, Bangalore Jagadish.B.S ME,Assistant Professor, M S Engineering College, Bangalore Department of Electronics and Communication,MSEC Page 1

2 VTU PRESCRIBED SYLLABUS Sub Code:10ECL67 IA Marks :25 Hrs/ Week :03 ExamHours: 03 Total Hrs. :42 ExamMarks :50 1. Amplitude Shift Keying 2. Frequency Shift Keying 3. BPSK Generation and Detection 4. DPSK Generation and detection. 5. QPSK Generation and detection 6. TDM of 2 Bandlimited Signals 7. Analog and Digital Communication Link Using Optical Fiber 8. Measurement of frequency,guided wavelength,power,vswr and attenuationin a microwave test bench 9. Directivity and gain of an antenna 10. Determination of coupling and isolation characteristics of a stripline directional coupler. 11. Measurement of resonance characteristics and dielectric constant. 12.Power Division and Isolation characteristics of a microstrip 3dB power divider Department of Electronics and Communication,MSEC Page 2

3 Exp 1.: AMPLITUDE SHIFT KEYING Circuit Diagram: Modulation Circuit: Demodulation Circuit Department of Electronics and Communication,MSEC Page 3

4 Expected Waveforms Department of Electronics and Communication,MSEC Page 4

5 Design : 1. Modulation: VRE(max) = 2.5v RE = VRE = 2.5 IE= IC 2.5m = 1kΩ RE = 1kΩ Assume IB sat = 1.2IB = 0.03mA RB = VB IBsat = m = 10kΩ RB = 10kΩ Department of Electronics and Communication,MSEC Page 5

6 2. Demodulation fm = 1 2пRC ; fm = 300Hz, C = 0.1 µf R = 5.6 kω 3. Calculation : a. Modulation: Frequency: Amplitude: b. Dernodulation: Frequency: Amplitude Aim : To design a circuit for detection and generation of an Amplitude Shift Keying Components Required: Op-amp(μA-741 ), Diode(OA 79), SL- I 00 transistor, Resistor, Capacitor, function generator. Theory : Amplitude-shift keying (ASK) is a form of modulation that represents digital data as variations in the amplitude of a carrier wave. The amplitude of an analog carrier signal varies in accordance with the bit stream (modulating signal), keeping frequency and phase constant. The level of amplitude can be used to represent binary. Logic 0s and ls. We can think of a carrier signal as an ON or OFF switch. In the modulated signal. Logic 0 is represented by the absence of a carrier, thus giving OFF/ON keying operation and hence the name given. Procedure: 1. Before connection check all the components. 2. Make connections as shown in circuit diagram 3. Observe the waveform pattern on the CRO. 4. Modulated ASK signal is obtained, which will be carrier signal for positive half cycle. 5. Construct the circuit for demodulation and obtain the output which is same as the message signal. Result : Department of Electronics and Communication,MSEC Page 6

7 Exp2: FREQUENCY SHIFT KEYING Circuit Diagram: Modulation Circuit: DeModulation Circuit: Department of Electronics and Communication,MSEC Page 7

8 FSK Modulation And Demodulation Circuit Department of Electronics and Communication,MSEC Page 8

9 Design : a. Modulation: VRE(max) = 2.5v RE = VRE(max) IE = m = 1kΩ RE = 1kΩ Assume IBsat = 0.03IB RB = VB IBsat = = 10kΩ RB = 10kΩ b. Demodulation fm = 1 2пRC ; fm = 300Hz, C = 0.1 µf R = 5.6 kω Department of Electronics and Communication,MSEC Page 9

10 c. Calculation : tmin = ms fmax = 1 = 1 tmin = KHz tmax = ms fmin = 1 = 1 tmax ms = KHz 1 DeModulation : f = = KHz Aim : To conduct an experiment to generate FSK signal and also design a circuit to demodulate the same. Components Required: Op-amp(~1A-74 l ), Diode(OA 79), SL-100 transistor, Resistor, Capacitor, function generator. Theory: Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave. The simplest FSK is binary FSK (BFSK). As suggested by the name, BFSK uses two discrete frequencies to transmit binary (O's and J's) information. In this scheme, binary 1 represents the frequency of one carrier and 0 represents the frequency of the other carrier. Procedure: 1. Before connection check all the components. 2. Make connections as shown in circuit diagram 3. Observe the waveform pattern on the CRO. 4. Modulated FSK signal is obtained then give FSK signal as input to the demodulation circuit.. Department of Electronics and Communication,MSEC Page 10

11 5. Construct the circuit for demodulation and obtain the output which is same as the message signal. Result : Exp3:BPSK Generation and Detection Circuit Diagram : Generation Department of Electronics and Communication,MSEC Page 11

12 Circuit Diagram : Degeneration BPSK Modulator : Department of Electronics and Communication,MSEC Page 12

13 Demodulator Circuit : Department of Electronics and Communication,MSEC Page 13

14 Design : a. Modulation : RC = VCC VCE IE Rb = Vin Vbe Ib = 1kΩ = 10 KΩ 1 Ib = If = ma hfe Rb = Vbe = 10 KΩ Isat b. Demodulation : fm >>Rc>> 1 fc C = 0.1µF, fm = 200Hz, fc = 10kHz R = 10kΩ Aim: Design & Demonstrate a BPSK system to transmit digital data using a suitable carrier. Demodulate the above signal with suitable circuit Components Required: Resistors, Capacitors, opamps, diodes, signal generators, CRO, power Supply Theorv: Phase shift keying is also one of the simplest digital modulation technique. In this system of modulation symbol 'l' is represented by phase 'Ǿ1' and symbol 'O' is represented by phase' Ǿ2' DPSK is one of the digital modulation schemes like PSK. Alternative to P.SK, instead of using the patterns to set the phase of the wave, it can instead be used to change it by a specified amount. The demodulator then determines the changes in the phase of the received signal rather than the Phase itself. Since this scheme depends on the difference between successive phases, it.i termed Differential phase-shift keying (DPSK). Procedure: 1. Connections are made as shown in circuit diagram 2. Provide message signal m(t) and carrier signal c(t) using signal generator 3 Observe the BPSK signal at the pin 3 of IC CD405 l and note down the readings (Voltage and time period) 4. Connect the detection circuit as shown and supply the BPSK signal and c(t) 5. Verify carefully, observe the intermediate ASK signal and finally observe Department of Electronics and Communication,MSEC Page 14

15 detected signal, note down its voltage level and time period. Result : Expected Waveforms Department of Electronics and Communication,MSEC Page 15

16 Exp 4: TDM OF 2 BAND LIIVIITED SIGNALS Department of Electronics and Communication,MSEC Page 16

17 Calculations : Department of Electronics and Communication,MSEC Page 17

18 Modulation : Triangular wave, f= = 1KHz, 1 Vp-p Sine wave,, f= = 526Hz, 4Vp-p DeModulation : Triangular wave, f= = 1KHz Sine wave, f= = Hz Aim: To design and demonstrated the working of TDM using PAM signals. Components Required: IC[7493, 4051), Resistor, Capacitors, Function generators CRO. Theory: A sampled waveform [PAM] is Off most of the t 1me, leaving the channel 2rmilable for others purpose during the interval between the samples. In particular, sample values from several different signals can be interleaved into a single waveform. This is the concept of Time Division Multiplexing. Several input message signals are prefiltered by low pass filter to make them strictly band-limited to remove high frequency components that are not needed to represent a signal adequately. The low pass filter output are sampled sequentially. Procedure: 1. Check the components. 2. Make connections as shown in the circuit diagram. 3. Apply the input signal [square wave] of 10 khz at pm 14 of 7493 and sine wave of 600Hz, 5Vp-p at pin 13 of IC Tune the input voltage till we get a sine wave at the output 3 of pin Now apply triangular wave of 5Vp-p and frequency l khz at pin 12 of IC Vary the input voltage till we get a TDM wave at the output. Observe in the CRO. 7. Now connect the demodulation circuit to get the demodulated sine wave and triangular wave. 8. Observe the waveform pattern in the CRO and plot. Department of Electronics and Communication,MSEC Page 18

19 Result: Exp : 5 Communication Link Using Optical Fiber Block diagram : Function Generator Emitter Circuit Detector Circuit Comparator AC Amplifier CRO Aim : To Study digital communication link in 650nm fiber optic digital cable Components Required: Fiber optic trainer, CRO, connecting probe, fiber optic wire Theorv: Fiber optic link can be used for transmission of digital as well as analog signals. Basically a fiber optic link contains three main elements, a transmitter, an optic fiber and a receiver. The transmitter module takes the input signal in the electrical form and then transforms it into optical energy containing the same information. Transmitter: Fiber optic transmitters are typically composed of a buffer, driven and optical source. The buffer provides both an electrical connection and Isolation between the transmitter and the electrical system supplying the data. Fiber optic link: Emitter and detector circuit on board from the fiber optic link this section provide the light source for the optic fiber and the light detector at the far end of the fiber optics links. The optic fiber plugs into the connectors provided in this part of the board. Receiver: The comparator circuit PLL, LPF AC amplifier circuit from receiver on the board. It is able to do the modulation process in order to recover the original information signal. Procedure : 1. Connect the power supply to the board. 2. Ensure all the switched faults are off. Department of Electronics and Communication,MSEC Page 19

20 3. Make the following connections Connect 1kHz Square wave output of emitter 1 's input Connect the fiber optic cable between emitter output and detectors input Detector 1 's output to comparator 1 's input Comparator 1 's output to AC amplifier 1 s input 4. On the board, switch emitter l's driver to digital mode. 5. Switch ON the power 6. Monitor both the inputs to comparator 1. Slowly adjust the comparators bias preset, until DC level on the input lies mid way between the high and low level of the signal on the positive input. 7. Observe the input to emitter l with the output from AC amplifier l and note that the two signals are same. Result : Department of Electronics and Communication,MSEC Page 20

21 Exp 6: Analog Communication Link Using Optical Fiber Function Generator Emitter Circuit Detector Circuit AC Amplifier CRO Aim : To Study digital communication link in 650nm fiber optic digital cable Components Required: Fiber optic trainer, CRO, connecting probe, fiber optic wire Theorv: Fiber optic link can be used for transmission of digital as well as analog signals. Basically a fiber optic link contains three main elements, a transmitter, an optic fiber and a receiver. The transmitter module takes the input signal in the electrical form and then transforms it into optical energy containing the same information. Transmitter: Fiber optic transmitters are typically composed of a buffer, driven and optical source. The buffer provides both an electrical connection and Isolation between the transmitter and the electrical system supplying the data. Fiber optic link: Emitter and detector circuit on board from the fiber optic link this section provide the light source for the optic fiber and the light detector at the far end of the fiber optics links. The optic fiber plugs into the connectors provided in this part of the board. Receiver: The comparator circuit PLL, LPF AC amplifier circuit from receiver on the board. It is able to do the modulation process in order to recover the original information signal. Procedure : 1. Connect the power supply to the board. 2. Ensure all the switched faults are off. 3. Make the following connections Connect 1kHz Square wave output of emitter 1 's input Connect the fiber optic cable between emitter output and detectors input Detector 1 's output to comparator 1 's input Department of Electronics and Communication,MSEC Page 21

22 Comparator 1 's output to AC amplifier 1 s input 4. On the board, switch emitter l's driver to digital mode. 5. Switch ON the power 6. Monitor both the inputs to comparator 1. Slowly adjust the comparators bias preset, until DC level on the input lies mid way between the high and low level of the signal on the positive input. 7. Observe the input to emitter l with the output from AC amplifier l and note that the two signals are same. Result : Block Diagram Exp 7: Measurement of Numerical Aperture Aim : To measure the numerical aperture of the optical fiber Components Required: Fiber optics trainer kit,cro, optical fiber wire and scale Theory : Numerical aperture refers to the wave angle of which the light incident on the fiber end is totally internally reflected and is transmitted properly along the fiber. It s formed by the relation of this angle of the fiber optic in the cone of acceptance of the fiber. Procedure : 1. Connect power supply to the board. 2. Connect the frequency generator of 1 khz sine wave output to input of the emitter 1 circuit. Adjust its amplitude to 5Vp-p 3. Connect one end of fiber optic cable to the output socket of emitter l circuit either to other end of Numerical aperture measurement. Department of Electronics and Communication,MSEC Page 22

23 4. Hold the white screen having facing the fiber such that it cut face is perpendicular to the axis of fiber. 5. Hold the white screen with four concentric circles (10, 15, 20, 25)mrn diameter, vertically at the suitable distance to red spot of the fiber coincide with 10rnm circle. 6. Record the distance of screen from the fiber end and note the diameter of the spot. 7. Compute the numerical aperture from the formula given below: sin θmax = W L 2 +W 2 8. Vary the distance between the screen and optic cable and make it coincide with one of the concentric circles. Note the distance. 9. Tabulate the various distance and diameter of the circles made on the white screen and compute the numerical aperture from formula given above. Tabular Column Sl No Length(cm) Width(cm) sin θmax = W L 2 +W 2 θmax =sin 1 W L 2 +W 2 Formula : W = (MR+PN) 4 θmax =sin 1 W L 2 +W 2 Department of Electronics and Communication,MSEC Page 23

24 4. DPSK GENERATION AND DETECTION Aim: To conduct an experiment to generate DPSK signal and also design a circuit to demodulate it. Components required: Power supply, kit ADCL-0 I, Connecting wires. Circuit: Theorv: Differentially phase shift keying (DPSK) is differentially coherent modulation. DPSK does not need a synchronous (coherent) carrier at the demodulator. The input sequence of binary Department of Electronics and Communication,MSEC Page 24

25 bits are modified such that the next bit depents upon the previous bit. Therefore in the receiver the prn ious received bits are used to detect the present bit.the input sequence is d(t). Ouput sequence is b(t) and b(t-tb) is the previous output delayed by onj bit period. Depending upon valures of d(t) and b(t-tb) exclusive OR gates generates the output sequence b(t).dpsk does not need ca~rier at its receiver. Hence the complicated circuitry for generation of local carrier is avoided. Procedure: 1.Refer the block diagram and carry out the following connections and switch settings. 2.Connect the power supply in proper polarity to the bit ADCL-0 I and switch to UN. 3 Select data pattern of simulated data using switch Connect SDAT A generator to DATA JN of c\"fferei>'ial er,c:oder. 5. Connect NRZ-L data output to DATA JN of differe;r,tial encoder. 6. Connect the north generator to S-CLK to CLK IN of the differential encoder. 7. Connect differentially encoded data to control input C 1 at carrier modulator. 8. Connect carrier compunents SIN 1 to IN 1 of carrier modulator. i,,i 9. Connect carrier compunents SIN2 to IN2 of carrier modulator. I 0. Connect DPSK modulated signal MO DO UT to MODIN of BPSK demodulator. 11. Connect ouput of BPSK demodulator b(t) out to input of delay section b(t) and input b(t)in of decision device. 12. Connect output of delay section. B(t-Tb) out of the inpur b(t-tb) In of decision device. 13. Compare the DPSK decoded data at data out with respect to Input SDA TA. 14. Input NRZ-L data in differential encoder. Result: Department of Electronics and Communication,MSEC Page 25

26 5.QUADRATURE PHASE SHIFT KEYING Aim: To study carrier modulation techniques by Quadrature Phase shifting method. Components Required: ADCL-02&03 Kits, Connecting chords, Power supply, CRO Theorv: In this modulation, called Quadraiure PSK(QPSK) or 4 PSK the sine carrier takes 4 phases values, separated of 90deg and determined by the combinations of bit pair (Di bit) of the binary data signal. The data are coded into Dibit by a circuit generating: A data signal l(in-phase) consisting in voltage levies con-esponding to the value of the first bit of the considered pair, for duration equal to 2 bit intervals. " A data signal Q(in-quadrature) consisting in voltage levies corresponding to the value of the first bit of the considered pair, for duration equal to 2 bit intervals. Circuit: Department of Electronics and Communication,MSEC Page 26

27 The block diagram of the modulator used on the module is shown in the figure, four 500kH:, sine carriers, shifted between them of 90deg are applied to modulator, the data (signal I & Q) reach the modulator from the dibit generator. The instantaneous value uf I anc.l Q data bit generates a symbol. Since I and Q can take either 0 or I value, maximum 4 possible symbols can be generated (00, 01, 10 and 11 ). According to the symbol generated one of the four-sine carrier \vill be selected. The relation between the symbol generated and sine carrier is shown in table. Department of Electronics and Communication,MSEC Page 27

28 A receiver for the QPSK signal is shown in fog,.synchronous detection is required and hence. i.t is necessary to locally regenerate the carriers, the scheme for carrier regeneration is similar to that employed in BPSK. In that earlier case we squared the incoming signal, extracted _the waveform at twice the carrier frequency by filtering and recovered the carrier by frequency dividing by two.1n the present case, it is required that the incoming signal be raised to the fourth pover after which filtering recovers a waveforms at four times the carrier.the incoming signal also applied to the sampler followed by an sadder and envelope detectors. Two adders add the sampled QPSK signal, sampled by the clock having different phases. At the output of added ti1e signals consisting the envelope corresponds to the 1 and Q bit. Envelope detector then filters the high frequency components and recovers I and Q bits having exactly same phase and frequency compared to transmitter 1 or Q bit. These I & Q bits then applied to data decoder logic to recover the original NRZ-L data pattern. Procedure: NOTE: KEEP THE SWITCH FAULTS IN OFF.POSJTION 1. Refer the block diagram and carry out the following connections and S\vitch setting:;. 2. Connect power supply in proper polarity to the kits ADCL-02 & ADCL-03 and switch it ON. 3. Select data pattern of simulated data using switch SW Connect SDA TA generated to DAT AIN of the NRZ-L CODER 5. Connect NRZ-L DATA to DA TA IN of the DIBIT CONVERSION. 6. Connect SCLOCK to CLK IN of the DIBIT CONVERSION. 7. Connect the dibit data I & Q bit to control in out C 1 and C2 CARRIER MODULATOR respectively. NOTE: adjust I & Q as shown in waveform by operating RST switch on ADCL02 before connecting it to C 1 & C2. 8. Connect carrier components to input of CARRIER MODULA TOR as follows: Department of Electronics and Communication,MSEC Page 28

29 i.s!n I to TN I ii.sin 2 to IN 2 iii.sin 3 to IN 3 iv.s1n 4 to IN 4 9. Connect QPSK modulated signal MODOUT on ADCL-02 to the MOD IN of the QPSK DEMODULATOR on ADCL-03. NOTE: Adjust Recovered I & Q bit on ADCL 03 as per ADCL -02 by RST Switch on ADCL Connect 1 BJT, Q BIT.& CLK OUT outputs of QPSK Demodulator to I BIT IN, Q-BIT &CLK IN posts of data decoder respectively. 11. Observations on ADCL-02 KIT: a. lnout NRZL Data at DATA INPUT. b. Canier frequency SIN 1 TO SIN 4. c. DiBIT pair generated data I bit & Q bit at DlBIT CONVERSION. d. QPSK modulated signal at :tv10d OUT. 12. Observations on ADCL-02 KIT: a. Output of first squarer at SQUARER 1. b. Output of second squarer at SQUARER 2. c Four sampling clocks at the output of SAMPLING CLOCK GENER.A.. TOR d. Two adder outputs at the output of ADDt:R. e. Recovered data bits (I & Q) at the output of ENVELOPE DETECTORS. f. Recovered NRZL data from I & Qbits at the output of DATA DECODER. Result: Department of Electronics and Communication,MSEC Page 29

30 ANALOG AND DIGITAL (WITH TDM) COMMUNICATION LINK USING OPTICAL Setting Up of Fibre Optic Analog Link: Block Diagram: Aim: To Study a 650nm Fibre optic analog link Components Required: Fibre optic trainer, CRO, connecting probe, Fibre optic wire Theorv: Fibre optic link can be used for transmission of digital as well as analog signals.basically a Fibre optic link contains three main elements, a transmitter, an optic Fibre and a receiver. The transmitter module takes the input signal in the electrical form and then transforms it into optical energy containing the same information Transmitter: Fibre optic transmitters are typically composed of a buffer, driven ::md optical source. The buffer provides both an electrical connection and Isolation between the transmitter and the electrical system supplying the data. Fibre optic link: Emitter and detector circuit on board from the Fibre optic link this section provide the light source for the optic Fibre a11d t'.1e light detector at the far end of the Fibre optics links. The optic Fibre plugs into the connectors provided in this part of the board The comparator circuit PLL, LPF AC amplifier circuit from receiver on the board. It is able to do the modulation process in order to recover the original information signal. Procedure: Department of Electronics and Communication,MSEC Page 30

31 1. Connect the power supply to the board. 2. Ensure all the switched faults are off. 3. Make the following connections Connect I khz Sine wave output of emitter l's input Connect the Fibre optic cable between emitter output and detectors input Detector 1 's output to comparator 1 's input Comparator l's outut to AC amplifier I's input 4. On the board, switch emitter 1 's driver to digital mode. 5. Switch ON the power 6. J'vlonitor both the inputs to comparator 1. Slowly adjust the comparators bias preset, until DC 7. Observe the input to emitter 1 with the output from AC amplifier 1 and note that the two signals are same. Result: Setting Up of Fibre Optic Analog Link: Aim: To Study a 650nm Fibre optic digital link Components Required: Fibre optic trainer, CRO, connecting probe, Fibre optic wire Theorv: Fibre optic link can be used for transmission of digital as well as analog signals. Basically a Fibre optic link contains three main elements, a transmitter, an optic Fibre and a receiver. The transmitter module takes the input signal in the electrical form and then transforms it into optical energy containing the same information. Transmitter: Fibre optic transmitters are typically composed of a buffer, driven and optical source. The buffer provides both an electrical connection and Isolation betvveen the transmitter and the electrical system supplying the data. Fibre optic link: Emitter and detector circuit on board from the Fibre optic link this section provide the light source for the optic Fibre and the light detector at the far end of the Fibre optics links. The optic Fibre plugs into the connectors provided in this part of the board. Department of Electronics and Communication,MSEC Page 31

32 Receiver: The comparator circuit PLL, LPF AC amplifier circuit from receiver on the board. It is able to do the modulation process in order to recover the original information signal. 1. Connect the power supply to the board. 2. Ensure all the switched faults are off. 3. Make the following connections Connect!kHz Square wave output of emitter 1 's input Connect the Fibre optic cable between emitter output and detectors input Detector 1 's output to comparator 1 's input Comparator 1 's output to AC amplifier I's input 4. On the board, switch emitter l's driver to digital mode. 5. Switch ON the power 6. Monitor both the inputs to comparator 1 (tp 13 & 14). Slowly adjust the comparators bias preset, until DC level on the input lies mid way between the high and low level of the signal on the positive input (tp 14). 7. Observe the input to emitter l(tp 5) with the output from AC amplifier l(tp 28) and note that the two signals are same. Result: Department of Electronics and Communication,MSEC Page 32

33 7. MEASUREMENT OF BENDING LOSSES AND NUMERICAL APERTURE OF A GIVEN OPTICAL FIBRE. Study of Bending Losses: Aim: To study loss using 1 m Fibre optic cable Theorv: In optical Fibre wire, whenever the condition of angle of incidence of the incident light is bended the losses are introduced due to refraction of light. This occurs when Fibre is subjected to bending lower radius of curvature more or less. Procedure: 1. Repeat al I the steps from 1 to 6 of digital I ink using Im cable. 2. Ensure that all S\Vitched faults are off. 3. Make the follo\ving connections. 4. Connect the 1 khz sine \Vave output to emitter l's input. Department of Electronics and Communication,MSEC Page 33

34 5. Connect the Fibre optic cable between emitter output and detector input. 6. Detector l's output to AC amplifier l's input 7. On the board, switch emitter l's driver to analog mode. 8.Observe the input to emitter with the output from AC amplifier & note the signals are same. Tabular Column First Bending: Second Morning: Third Binding: Result: Department of Electronics and Communication,MSEC Page 34

35 Measurement of Numerical Aperture: Aim: To measure the numerical aperture of Fibre Components: Fibre optic cable, screen, trainer kit. Theorv: Numerical aperture refers to the wave angle of which the light incident on the Fibre end is totally internally reflected and is transmitted properly along the Fibre. It s formed by the relation of this angle of the Fibre optic in the con'e of acceptance of the Fibre. Procedure: 1. Connect pm:ver supply to the board. Department of Electronics and Communication,MSEC Page 35

36 2. Connect the frequency generator of 1 khz sine wave output to input of the emitter circuit. Adjust its amplitude to 5Yp-p 3. Connect one end of Fibre optic cable to the output socket of emitter l circuit either to other end of Numerical aperture measurement. 4. Hold the white screen having facing the Fibre such that it cut face is perpendicular to the axis of Fibre. 5. Hold the white screen with four concentric circles (10, 15, 20, 25)mrn ck11neter, vertically at the suitable distance to n1jke :':'.d spot of the Fibre coincide with 10rnm circle. 6. Record the distance of screen from the Fibre end and note the diameter of the spot. 7. Compute the numerical aperture from the formula given below: 8. Vary the distance between the screen and optic cable and make it coincide with one of the concentric circles. Note the distance. 9.Tabulate the various distance and diameter of the circles made on the white screen and compute the numerical aperture from formula given above. TABULAR COLUMN Formula: W = (MR+PN)/4 Department of Electronics and Communication,MSEC Page 36

37 MEASUREMENT OF FREQUENCY, GUIDE WAVELENGTH, POWER, VSWR AND ATTENUATION IN A MYCROWAVE TEST BENCH To set the square wave and measurement of frequency,vswr and attenuation: Measurement of Power and VSWR: Department of Electronics and Communication,MSEC Page 37

38 Calculations: Frequency: Guided wavelength: Tabular Column: s.no Power MSR CVD R=MSR+(CVD*L.C) Calculations: Department of Electronics and Communication,MSEC Page 38

39 Aim: To conduct an experiment to obtain guide wavelength,frequency,power and attenuation in a microwave test bench. Components required: Attenuator, frequency meter,isolator,oscillator, detector,klystron power supply,vswr meter and CRO. Theory: Department of Electronics and Communication,MSEC Page 39

40 10. DIRECTIVITY AND GAIN OF AN ANTENNA Aim: To measure the directivity and gain of antenna's standard dipole. Components Required: Power supply, microwave source (VCO), 6dB attenuator, Transmitting antenna, Rotatable Test Antenna, Detector, Active filterm VSWR meter, CRO. Procedure: 1. Set up the system as shown in block for a standard dipole antenna 2. Keeping the voltage at minimum, switch ON the power supply. 3.Vary the power supply voltage and check the output for different VCO frequencies. 4. Keeping at the resonant frequceny, calculate and keep the minimum distance for field between the transmitting and receiving antenna using the formula: S = 2d0.0 where cl is the broader dimension of the antenna. 5 Keeping the line of sight properly (0 at the tum table). Tabulate the output obtained. 6. Rotate the tum table in clock wise and anto clock-\vise for different angle of deflection and tabulate the output for every angle(e~). 7. Plot a graph: angle Vs output 8 Find the half power beam with (HPBW) from the points where the power half (3dB points or 0.707\i points) 9. Directivity of the antenna can be calculated using the formula I (HPBW)4 where HPBW is the half power beam width in degrees. En and E < >> are the output signals measured at the receiving antenna for 00 and for different angles respectively 10. Gain of the antenna can be calculated using the formula. Circuit Diagram Department of Electronics and Communication,MSEC Page 40

41 Tabular Column: 11. DETERMINATION OF COUPLING AND ISOLATION CHARACTERISTICS OF A STRIPLINE (OR MICROSTRIP) DIRECTIONAL COUPLER Aim: Determination of coupling and Isolation characteristics of a stripline Components required: Power supply, Microwave source, attenuator, detector, active filter, VSWR or CRO Procedure: 1. Set up the system as sho\vn in figure 2. Keeping the voltage at minimum, Switch On the po\ver supply. 3. lnsert a 50ohm transmission line and check for the output at the end of the system using a CRO/VSWR meter/ F power meter 4. Vary the power supply voltage and check the output for different VCO frequencies. 5. Keep the VCO frequency constant, note down the output. This value can be taken as the input to the power divider. 6.Replace the 50ohm transmission line with the Wilkinson power divider. 7. Tabulate the output at port2,3 and Calculate insertion loss and coupling factor in each coupled arm. 9. Calculate the isolation between port 3 and 4 by feeding the input to port 3 and measure 10. Output at port by terminating port I and port Repeat the experiment for different VCO frequencies. Result: Department of Electronics and Communication,MSEC Page 41

42 12.MEASUREMENT OF RESONANCE CHARACTERISTICS AND DIELECTRIC CONSTANT Tabular Column Department of Electronics and Communication,MSEC Page 42

43 Department of Electronics and Communication,MSEC Page 43

44 Aim: To measure the resonance characteristic characteristics of a mycrostrip Ring Resonator and Determination of Dielectric constant of the substrate. Apparatus: Power supply, attenuator, detector, active filter, CRO, metal Zig Procedure: 1.Connect 6dB attenator to RF output in C-band solid state source with power supply order to control noise. 2. Also connect an 6dB attenuator to detector also. 3. In order to gain proper sine wave tune voltage and gain. 4. Once we get sine wave, place a ring resonator in metal zig. Then place metal zig between supply and detector. 5. Now adjust voltage and gain in order to get a sine wave. 6. Now tabulate the values of voltage obtained from CRO and frequency which is obtained from power supply. Department of Electronics and Communication,MSEC Page 44

45 7. This is the procedure for ring resonator in air. Now cover the ring resonator with a material on metal zig and follow the same procedure to get dielectric. 13.Power Division and Isolation characteristics o(a microstrip 3dB power divider Block Diagram To check sine wave: Block Digram to power arms Calculation: Power at arm2: P1-P2 Power at arm3:p1-p3 Power at arm1:p2-p3 Department of Electronics and Communication,MSEC Page 45

46 Aim: To measure the power division and isolation characteristics of divider. rnicrostrip power Apparatus: Power supply, attenuators, detector, active filter, CRO, metal zig, VSWR, 50ohm mismatch terminals. Procedure: 1.First check only for sine wave without connecting the metal zig and set the frequency as 5gHz. 2. Now remove the connection to CRO and connect it to VSWR. 3. Set the VSWR to Connect the metal zig also. 5. If p2 is considered as output then p3 is connected to 50ohm mismatch terminator and vice-versa. 6. p I is always considered as input. 7. Calculate the power arm 2 and 3 and isolation which should be zero. Department of Electronics and Communication,MSEC Page 46