MPSK Tutorial. Tom Rondeau Tom Rondeau () MPSK Tutorial / 26

Transcription

1 MPSK Tutorial Tom Rondeau Tom Rondeau () MPSK Tutorial / 26

2 Outline 1 Introduction 2 Digital Modulation Study 3 Tom Rondeau () MPSK Tutorial / 26

3 Download Materials Introduction Presentation PDF Case Study materials GNU Radio apps to run examples. Links to source code for analysis. Data le for rst case study. Images of expected output. Exercises. Tom Rondeau () MPSK Tutorial / 26

4 Sources and Sinks Introduction sources_and_sinks.grc Demonstration of using multiple sources to create a noisy sine wave and multiple sinks to view it in dierent domains. Tom Rondeau () MPSK Tutorial / 26

5 Sources and Sinks Introduction sources_and_sinks.grc Showing both the frequency and time domain of the noisy signal. Tom Rondeau () MPSK Tutorial / 26

6 Digital Modulation Study Information Representation bits_representation.grc We can visualize bits as a series of 1's and 0's that are translated into 1's and 1 's. Tom Rondeau () MPSK Tutorial / 26

7 Digital Modulation Study Information Representation bits_representation.grc We can do the same for another stream of bits and work actually combine them into a single signal. Tom Rondeau () MPSK Tutorial / 26

8 Digital Modulation Study Information Representation bits_representation.grc We combine these by using complex numbers as an orthogonal basis. Tom Rondeau () MPSK Tutorial / 26

9 Complex Numbers Digital Modulation Study z(t) = x(t)cos(2πft + φ(t)) + jy(t)sin(2πft + φ(t)) z(t) = c(t)e j2πft+φ(t) Tom Rondeau () MPSK Tutorial / 26

10 Digital Modulation Study Complex Numbers: Polar Plots} Tom Rondeau () MPSK Tutorial / 26

11 Digital Modulation Study Information as a Complex Number bit_representations.grc Putting one signal on the real axis and another signal on the imaginary axis, we can combine these on two orthogonal planes. The constellation plot on the right is just a polar plot. Tom Rondeau () MPSK Tutorial / 26

12 Modulating & Transmitting a Signal mpsk_stage1.grc Using a pre-build PSK modulator block from GNU Radio. Tom Rondeau () MPSK Tutorial / 26

13 Modulating & Transmitting a Signal Tom Rondeau () MPSK Tutorial / 26

14 The Received Signal mpsk_stage2.grc We can simulate a channel model with noise, frequency and timing osets, and multipath. Tom Rondeau () MPSK Tutorial / 26

15 The Received Signal mpsk_stage2.grc Signal captured using a multipath channel with some AWGN noise and timing oset. To make the signal recognizable, no frequency oset was used. Tom Rondeau () MPSK Tutorial / 26

16 After Timing Recovery mpsk_stage3.grc We use a control loop algorithm to nd the right sampling time to x clock mismatches between the transmitter and receiver. Tom Rondeau () MPSK Tutorial / 26

17 After Timing Recovery mpsk_stage3.grc Showing a no-noise situation to illustrate ISI (self-interference) issues in the received signal before timing recovery and matched ltering. Tom Rondeau () MPSK Tutorial / 26

18 After Timing Recovery - With Noise mpsk_stage3.grc Even with noise, we can still recover the proper timing. Tom Rondeau () MPSK Tutorial / 26

19 Multipath in Brief Multipath channels result from a signal bouncing o objects and hitting the receiver at dierent times and with dierent phases. Tom Rondeau () MPSK Tutorial / 26

20 Eects of Multipath mpsk_multipath.grc This simulation allows us to adjust the multipath channel as though we are adjusting a stereo's equalizer. (See also: multipath_sim.grc) Tom Rondeau () MPSK Tutorial / 26

21 Equalizing Multipath Cartoon showing signal corrupted by multipath. Equalizer tries to invert the multipath so that the combination is a at frequency response. Tom Rondeau () MPSK Tutorial / 26

22 Equalizing Multipath mpsk_stage4.grc Using the constant modulus algorithm (CMA) blind equalizer is used here to correct multipath distortion. Tom Rondeau () MPSK Tutorial / 26

23 Equalizing Multipath mpsk_stage4.grc Note the similarity between the time-synchronized and ltered output with multipath and the ISI of the signal before the matched lter with no multipath. Tom Rondeau () MPSK Tutorial / 26

24 Equalizing Multipath mpsk_stage4.grc Equalization working with noise. Tom Rondeau () MPSK Tutorial / 26

25 Phase Oset Correction mpsk_stage5.grc The transmitter and receiver work o dierent clocks, so there will be a frequency and phase oset. We need to correct for any small frequency and phase osets. Tom Rondeau () MPSK Tutorial / 26

26 After Timing Recovery - With Noise mpsk_stage5.grc Left gure shows a rotate constellation. The Costas Loop block xes the oset. Tom Rondeau () MPSK Tutorial / 26