DOC PREVIEW
Rose-Hulman ECE 300 - Frequency Multiplying Circuit

This preview shows page 1 out of 4 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 4 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 4 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

Frequency Multiplying CircuitTheory of OperationPre-Lab CalculationsLaboratory ProcedureBuilding up the Circuit.Frequency Multiplication6-1 6. Frequency Multi plying Circuit ECE 300 Lab 6 Frequency Multiplying Circuit In this lab we look at extracting a higher frequency sine wave from lower frequency square wave. 6.A. Theory of Operation From our study of the Fourier series expansion of a periodic signal, we know that a square wave at frequency Fo is composed of a sum of sinusoidal waves at frequencies nFo, where n ranges from 1 to infinity. If we take this signal and pass it through a band pass filter that has a pass band narrow enough to filter out all harmonics except one, we can obtain a sine wave that has a higher frequency than the fundamental frequency of the square wave. For this lab we will use a 2 kHz square wave with an amplitude of 0.5 volts. This square wave contains sinusoidal frequencies of 2 kHz, 4kHz, 6kHz, 8KHz, 10kHz, and higher. We will use a 6th order filter with a pass-band of 9 kHz to 11 kHz. Thus, when we pass our 2 kHz square wave through this filter, we should obtain a 10 kHz sine wave at the output. 6.B. Pre-Lab Calculations • Compute the Fourier series coefficients of a 0.5 volt amplitude square wave. Specifically find the magnitude of the 5th harmonic (the one at 10 kHz). • Simulate the circuit of Figure 6-1. You should run two simulations: o An AC sweep from 5 kHz to 15 kHz. Obtain Bode plots of Vo2/Vin, Vo1/Vin, and Vo/Vin. For this simulation, use the part VAC for the input voltage source. o A Transient analysis to view Vo(t). For the input, use the part called Vsq. Set the frequency to 2 kHz and the amplitude to 0.5 Volts. Set up the Transient analysis to run for 100 ms and set the maximum time step to 1 µs. Plot Vo(t) from 99 ms to 100 ms. Use the cursors to measure the amplitude and frequency of this waveform. Compare the amplitude of this waveform to the amplitude predicted by the Fourier series expansion. An example output waveform is shown in Figure 6-2. + C4 0.01U +-U3Ideal_OPAMP +-U2 Ideal_OPAMP + R3 56k + C50.01U0 Vo2 Vo+R67.5k0 + R847 + R2 47k + R9 56 0 + C20.01U+ - U1 Ideal_OPAMP Vin+ C60.01U0 + C1 0.01U +R5 7.5k0 + R1 27k + R7 100 + - V4 FREQUENCY = 2k AMPLITUDE = 0.50+ C3 0.01U Vo10 + R4 12k Figure 6-1: 6th order band pass filter.6-2 Time99.0ms 99.1ms 99.2ms 99.3ms 99.4ms 99.5ms 99.6ms 99.7ms 99.8ms 99.9ms 100.0msV(Vo)-200mV-100mV0V100mV200mV Figure 6-2: Sinusoidal output of the filter. Note: A 6th order filter may be very difficult to build and operate. If you want, you can use the 4th order filter shown Figure 6-6 in instead of the 6th order filter. Note that, in theory, the 4th order filter will not work as well as a 6th order filter in extracting the 5th harmonic. However, a 4th order filter may be easier to build in the lab. 6.C. Laboratory Procedure 6.C.2. Building up the Circuit. (1) For a large circuit like this it is important to build it in small pieces and verify the operation of each piece. Wire up the first stage as shown in Figure 6-3 using a TL072 OP-AMP (or whatever OP-AMP you can find). The input should be a 1 volt sine wave or smaller.6-3+-U1TL072Vin-+VinVo2+R127k0+C40.01U+R412k0+C10.01U0+R7100 Figure 6-3: First stage of the band-pass filter. Using VEE, measure a bode plot of Vo2/Vin and compare it to the one predicted by PSpice. If the plots agree, you can continue with the second stage. If the output of this stage is incorrect, find the problem before continuing. Measurement Results: Create a graph that displays the measured and PSpice plots of Vo2/Vin. Plot both traces on the same graph. (2)Wire up the second stage as shown in Figure 6-4. The input should be a 1 volt sine wave or smaller. +C20.01U0+-U1TL072Vin+R847Vo1-+VinVo2+R127k0+C40.01U+R57.5k+C50.01U+R412k00+R247k+-U2Ideal_OPAMP+C10.01U0+R7100 Figure 6-4: First two stages of the band-pass filter. Using VEE, measure a bode plot of Vo1/Vin and compare it to the one predicted by PSpice. If the plots agree, you can continue with the third stage. If the output of this stage is incorrect, find the problem before continuing. Measurement Results: Create a graph that displays the measured and PSpice plots of Vo1/Vin. Plot both traces on the same graph. (3)Wire up the third stage as shown in Figure 6-5. The input should be a 1 volt sine wave or smaller.6-4+C20.01U0+-U1TL072Vin+R847+R356kVo1-+VinVo2+-U3Ideal_OPAMP+R67.5k+C60.01U+R127k0+C30.01U0+C40.01U+R57.5k+C50.01U+R412k00+R247k+-U2Ideal_OPAMP0+C10.01U+R956Vo0+R7100 Figure 6-5: 6th order band-pass filter. Using VEE, measure a bode plot of Vo/Vin and compare it to the one predicted by PSpice. If the output of this stage is incorrect, find the problem before continuing. Measurement Results: Create a graph that displays the measured and PSpice plots of Vo/Vin. Plot both traces on the same graph. 6.C.2. Frequency Multiplication Now that the filter is correctly wired, we can test it with a square wave input. Apply a 0.5 V amplitude 2 kHz square wave to your filter and measure the amplitude and frequency of the output using an oscilloscope. Compare the measured amplitude and frequency to the values found from PSpice and the Fourier series expansion. Record the results in a table for easy comparison. Demonstrate your circuit to your lab instructor. Display the input square wave and the output sine wave on the scope display. +R224k+C50.01U+R71000+R46.8k0+C40.01U0Vo+R56.8k0Vo1+-V1FREQUENCY = 2kAMPLITUDE = 0.5+R120k+R8130+-U2Ideal_OPAMPVin+-U1Ideal_OPAMP0+C20.01U+C10.01U Figure 6-6: 4th order band-pass filter with a pass band of 9 kHz to 11


View Full Document

Rose-Hulman ECE 300 - Frequency Multiplying Circuit

Documents in this Course
Exam 2

Exam 2

8 pages

Load more
Download Frequency Multiplying Circuit
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Frequency Multiplying Circuit and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Frequency Multiplying Circuit 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?