- Added utilities for frequency planning
- Changed freq plane to: Fs 4096, int/dec 8X, Mixers 768
This commit is contained in:
canisio
301
utilities/rxspectrum.m
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301
utilities/rxspectrum.m
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function rxspectrum(scenario, fc, bw, fs, fshift, L)
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if( nargin == 0)
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fprintf('Use this function to plot your Receive spectrum\n');
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fprintf('\n');
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fprintf('First argument is to run 8 example scenarios.\n');
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fprintf('rxpsectrum(1) or rxspectrum(2)...to plot and study various scenarios\n');
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fprintf('\n');
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fprintf('For custom numbers function can be called as follows\n');
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fprintf('rxspectrum([], center frequency, data bandwidth, sampling frequency,shift or carrier frequency, x-axis plotting limit(optional arugment)\n');
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elseif (nargin == 1)
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%% System Parameters
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sys = [];
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sys.scenario = scenario;
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switch sys.scenario
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case 1
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% Good Scenario. Nyquist sampling theorem.
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%
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% The sampling rate of 4 GHz is high enough to satisfy Nyquist sampling
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% theorem.
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%
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% Use Nyquist Zone 1.
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sys.fc = 1e9;
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sys.bw = 300e6;
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sys.fs = 4e9;
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sys.fshift = -1e9;
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L = 7;
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sys.xlim = [-L L];
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sys.xticks = -L : L;
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case 2
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% Good Scenario. Bandpass sampling theorem.
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%
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% The sampling rate of 3 GHz is not high enough to satisfy Nyquist sampling
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% theorem but it is one of the good sampling rates from bandpass sampling
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% theorem.
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%
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% Use Nyquist Zone 2.
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sys.fc = 3e9;
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sys.bw = 300e6;
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sys.fs = 4e9;
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sys.fshift = 1e9;
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L = 7;
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sys.xlim = [-L L];
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sys.xticks = -L : L;
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case 3
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% Bad Scenario.
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%
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% Sampling rate does not satisfy Nyquist nor bandpass sampling theorem.
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%
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% Spectrum overlaps (completely or partially).
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sys.fc = 3e9;
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sys.bw = 300e6;
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sys.fs = 2.4e9; % Complete Overlap
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% sys.fs = 5.8e9; % Partial Overlap
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sys.fshift = -0.6e9;
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L = 10;
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sys.xlim = [-L L];
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sys.xticks = -L : L;
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case 4
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% Bad Scenario.
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%
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% Sampling rate satisifies bandpass sampling theorem but spectra touch each
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% other.
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%
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% Unless we have an ideal brick wall lowpass filter, we cannot recover the
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% signal at 3 GHz.
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sys.fc = 3e9;
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sys.bw = 300e6;
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sys.fs = 5.7e9;
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sys.fshift = 2.7e9;
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L = 10;
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sys.xlim = [-L L];
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sys.xticks = -L : L;
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case 5
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% Solution to scenario 4. Spectra no longer touch either other.
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%
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% But we cannot use Xilinx hard IP decimate-by-2.
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sys.fc = 3e9;
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sys.bw = 300e6;
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sys.fs = 3.4e9;
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sys.fshift = 0.4e9;
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L = 8;
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sys.xlim = [-L L];
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sys.xticks = -L : L;
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case 6
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% Solution to scenario 5. Spectra no longer touch either other and we can
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% use Xilinx hard IP decimate-by-2.
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sys.fc = 3e9;
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sys.bw = 300e6;
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sys.fs = 4e9;
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sys.fshift = 1e9;
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L = 8;
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sys.xlim = [-L L];
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sys.xticks = -L : L;
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case 7
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% Same problem even with Nyquist sampling theorem.
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sys.fc = 1.5e9;
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sys.bw = 300e6;
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sys.fs = 4e9;
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sys.fshift = -1.5e9;
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L = 7;
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sys.xlim = [-L L];
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sys.xticks = -L : L;
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case 8
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sys.fc = 1.5e9;
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sys.bw = 300e6;
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sys.fs = 2e9;
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sys.fshift = -0.5e9;
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L = 7;
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sys.xlim = [-L L];
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sys.xticks = -L : L;
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otherwise
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error('Invalid sys.scenario');
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end % switch
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end %if(nargin == 1)
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if (nargin == 5)
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%% System Parameters
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sys = [];
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sys.scenario = scenario;
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sys.fc = fc;
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sys.bw = bw;
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sys.fs = fs;
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sys.fshift = fshift;
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L = 7;
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sys.xlim = [-L L];
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sys.xticks = -L : L;
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end
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if (nargin == 6)
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%% System Parameters
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sys = [];
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sys.scenario = scenario;
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sys.fc = fc;
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sys.bw = bw;
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sys.fs = fs;
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sys.fshift = fshift;
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sys.xlim = [-L L];
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sys.xticks = -L : L;
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end
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sys.xunit = 'GHz';
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%%
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if isempty(findobj('Number', sys.scenario))
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figure(sys.scenario)
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set(gcf, 'Position', [27 82 1180 638])
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else
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figure(sys.scenario)
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clf
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end
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%%
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Nsubplots = 5;
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subplot(Nsubplots, 1, 1);
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xlim(sys.xlim);
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xticks(sys.xticks);
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set(gca, 'Position', [0.04 0.8720 0.9277 0.09])
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plotspectrum('asym', sys.fc, sys.bw, 'r', sys.xunit);
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plotspectrum('asymflip', -sys.fc, sys.bw, 'r', sys.xunit);
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title(sprintf('Analog Bandpass Signal (Center = %.2f GHz. BW = %d MHz.)', ...
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sys.fc/1e9, sys.bw/1e6), 'FontSize', 12);
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plotannotations(sys.fs, 1);
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set(get(gca, 'XAxis'), 'FontSize', 11);
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%%
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subplot(Nsubplots, 1, 2);
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xlim(sys.xlim);
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xticks(sys.xticks);
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set(gca, 'Position', [0.04 0.6720 0.9277 0.09])
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title(sprintf('Sampling Images (Towards +ve Frequencies). Fs = %.2f GHz.', ...
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sys.fs/1e9), 'FontSize', 12);
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for n = 1:8
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f1 = sys.fc + n*sys.fs;
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f2 = -sys.fc + (n*sys.fs);
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plotspectrum('asym', f1, sys.bw, 'b', sys.xunit);
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plotspectrum('asymflip', f2, sys.bw, 'b', sys.xunit);
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end
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set(get(gca, 'XAxis'), 'FontSize', 11);
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%%
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subplot(Nsubplots, 1, 3);
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xlim(sys.xlim);
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xticks(sys.xticks);
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set(gca, 'Position', [0.04 0.4720 0.9277 0.09])
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title(sprintf('Sampling Images (Towards -ve Frequencies). Fs = %.2f GHz.', ...
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sys.fs/1e9), 'FontSize', 12);
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for n = -1:-1:-8
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f1 = sys.fc + n*sys.fs;
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f2 = -sys.fc + (n*sys.fs);
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plotspectrum('asym', f1, sys.bw, 'c', sys.xunit);
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plotspectrum('asymflip', f2, sys.bw, 'c', sys.xunit);
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end
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set(get(gca, 'XAxis'), 'FontSize', 11);
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%%
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subplot(Nsubplots, 1, 4);
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xlim(sys.xlim);
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xticks(sys.xticks);
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set(gca, 'Position', [0.04 0.2720 0.9277 0.09])
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title(sprintf('Real Digital Signal (Fs = %.2f GHz. BW %d MHz.)', ...
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sys.fs/1e9, sys.bw/1e6), 'FontSize', 12)
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n = -8:8;
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f1 = sys.fc + n*sys.fs;
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f2 = -sys.fc + (n*sys.fs);
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plotspectrum('asym', f1, sys.bw, 'r', sys.xunit);
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plotspectrum('asymflip', f2, sys.bw, 'r', sys.xunit);
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plotannotations(sys.fs, 0);
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set(get(gca, 'XAxis'), 'FontSize', 11);
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%%
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subplot(Nsubplots, 1, 5);
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xlim(sys.xlim);
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xticks(sys.xticks);
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set(gca, 'Position', [0.04 0.0720 0.9277 0.09])
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title(sprintf(['Complex Baseband Signal (Fs = %.2f GHz. BW %d MHz. ', ...
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'fshift = %.2f GHz)'], sys.fs/1e9, sys.bw/1e6, sys.fshift/1e9), ...
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'FontSize', 12);
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f1 = f1 + sys.fshift;
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f2 = f2 + sys.fshift;
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plotspectrum('asym', f1, sys.bw, 'r', sys.xunit);
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plotspectrum('asymflip', f2, sys.bw, 'r', sys.xunit);
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plotannotations(sys.fs, 0);
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set(get(gca, 'XAxis'), 'FontSize', 11);
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Fs = sys.fs / 1e9;
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x = [-Fs/2, -Fs/4, -Fs/4, Fs/4, Fs/4, Fs/2];
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y = [0.25, 0.25, 0.75, 0.75, 0.25, 0.25];
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hold on
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plot(x, y, 'k--', 'LineWidth', 2)
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end
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% ------------------------------------------------------------------------------
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% Helper Functions
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% ------------------------------------------------------------------------------
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function plotannotations(fs, zone)
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%% Plot DC.
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xline(0, 'LineWidth', 3, 'Color', 'g', 'LineStyle', '--')
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y = 0.9;
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addtext1(0, y, '0')
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%% Plot fs/2.
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xline(fs/2/1e9, 'LineWidth', 3, 'Color', 'g', 'LineStyle', '--')
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xline(-fs/2/1e9, 'LineWidth', 3, 'Color', 'g', 'LineStyle', '--')
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addtext1(0 + fs/2/1e9, y, 'Fs/2')
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addtext1(0 - fs/2/1e9, y, '-Fs/2')
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%% Plot fs.
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xline(fs/1e9, 'LineWidth', 3, 'Color', 'g', 'LineStyle', '--')
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xline(-fs/1e9, 'LineWidth', 3, 'Color', 'g', 'LineStyle', '--')
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addtext1(0 + fs/1e9, y, 'Fs')
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addtext1(0 - fs/1e9, y, '-Fs')
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%% Plot 3*fs/2.
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xline(fs*1.5/1e9, 'LineWidth', 3, 'Color', 'g', 'LineStyle', '--')
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xline(-fs*1.5/1e9, 'LineWidth', 3, 'Color', 'g', 'LineStyle', '--')
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addtext1(0 + 1.5*fs/1e9, y, '3*Fs/2')
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addtext1(0 - 1.5*fs/1e9, y, '-3*Fs/2')
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% %% Plot ...
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% ntext4(0 + 1.6*fs/1e9, 0.6, '...', 'FontSize', 30, 'FontWeight', 'bold');
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% ntext4(0 - 1.7*fs/1e9, 0.6, '...', 'FontSize', 30, 'FontWeight', 'bold');
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% %%
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% if zone == 1
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% addtext2(0.7, 0.65, {'Nyquist', 'Zone 1'})
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% addtext2(0.7 + fs/2/1e9, 0.65, {'Nyquist', 'Zone 2'})
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% % addtext2(0.7 + fs/1e9, 0.65, {'Nyquist', 'Zone 3'})
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% end
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end
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function addtext1(x, y, t)
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h = ntext4(x, y, t);
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h.FontSize = 15;
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h.FontWeight = 'bold';
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h.HorizontalAlignment = 'center';
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end
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function addtext2(x, y, t)
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h = ntext4(x, y, t);
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h.FontSize = 15;
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h.FontWeight = 'bold';
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h.Color = [0 0.4470 0.7410];
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h.HorizontalAlignment = 'center';
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end
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