Reference no: EM132373822
Questions
1. In Transmitter step 3 you are given 1/T = 10,000 symbols/s and 1/Tx 400 x 103 . Find the corresponding value for the number of samples per symbol L.
2. Explain how an IIR filter having a forward coefficients array of [1] and a reverse coefficients array of [1 -1] implements an integrator.
3. Explain how an FIR filter having a coefficients array of [1 -1] implements a differentiator, as used in Receiver step 1.
4. Explain what a median filter does. Refer to the LabVIEW 2014 online help for the Median Filter function for information.
5. In Receiver Step 2 the "actual IQ rate" 1 Tz may be different than the rate 1 Tx that was used at the transmitter. ( Note that the symbol rate 1 T must be the same at the transmitter and receiver.) The value of the receiver's IQ rate determines the receiver sampling factor M.
What is the advantage to using a higher value of M ? What is the advantage of using a lower value of M?
6. The FM receiver uses a differentiator to undo the integral in Eq. (4). What is the effect of the differentiator on any noise that might be present along with the signal? To answer this, consider what a differentiator does in the frequency domain. What would be the effect of omitting the filter that follows the differentiator?
Questions
1. With the peak frequency deviation set at 5000 Hz, compare the rate of spectral rolloff with rectangular pulses and with Gaussian filtering. Also, by examining the plot of the transmitted message signal, can you find evidence of intersymbol interference when Gaussian filtering is used?
2. For each value of peak frequency deviation listed in Step 5, compare the null-to-null bandwidth of the transmitted signal with the bandwidth predicted by Carson's rule, Eq. (1). Compute the percentage difference in each case. Is Carson's rule more accurate for large peak frequency deviation or for small peak frequency deviation?
3. Observe the eye diagram shown on the receiver front panel. Compare the display when the eye diagram shows the baseband output waveform and when the eye diagram shows the aligned baseband output waveform. Describe what function PulseAlign(real) is performing.
4. Make a plot of the amplitude of the receiver's baseband output waveform vs. the peak frequency deviation. What is the relationship between these two quantities?
5. As described in Lab 7: Amplitude-Shift Keying, one of the quantities easily seen on the eye diagram is the optimum decision threshold location. In the present lab project, you were instructed to set the decision threshold to zero. Run the transmitter and receiver several times for different values of peak frequency deviation and for filtering set to "none" and "Gaussian." Observe the eye diagram and comment on the appropriateness of using zero for the decision threshold.
Lab Book: Introduction to Communication System - Lab-Based Learning with NI USRP and Lab VIEW Communications by Bruce A. Black.