Frequency Shift¶

[1]:

%pylab inline
pylab.rcParams['savefig.dpi'] = 300
from caf_verilog.freq_shift import FreqShift

%pylab is deprecated, use %matplotlib inline and import the required libraries.
Populating the interactive namespace from numpy and matplotlib

[2]:

fs = 625e3
freq_res = 200
n_bits = 8

[3]:

n = np.arange(0,10e3)
x = np.exp(2*np.pi*((50e3)/fs)*n*1j)

[4]:

Px, ff = psd(x,2**10, fs)
plot(ff, 10*np.log10(Px))
xlim([0, 100e3])
ylim([-80, 0])

[4]:

(-80.0, 0.0)

../_images/nb_examples_FrequencyShift_4_1.png

[5]:

fq = FreqShift(x, freq_res, fs, n_bits)

[6]:

fq.gen_tb(20e3)

[7]:

max(fq.x_quant.real), min(fq.x_quant.real), max(fq.x_quant.imag), min(fq.x_quant.imag)

[7]:

(2047.0, -2031.0, 2043.0, -2043.0)

[8]:

max(x.real), min(x.real), max(x.imag), min(x.imag)

[8]:

(1.0, -0.9921147013145629, 0.9980267284283143, -0.9980267284282867)

[9]:

Px_in, ff_in = psd(fq.x_quant,2**10, fs)
plot(ff_in, 10*np.log10(Px_in))
xlim([0, 100e3])
ylim([-80, 40])
savefig('freq_shift_in.png')

../_images/nb_examples_FrequencyShift_9_0.png

Generated Shifted Signal¶

[10]:

from caf_verilog.io_helper import read_complex_output
gss = read_complex_output(fq.test_output_filename)
sss = read_complex_output(fq.submodules['sig_gen'].test_output_filename)

[11]:

print(len(gss), len(x))

10000 10000

[12]:

assert len(gss) == len(x)

[13]:

print(gss[:5])

[(1015+0j), (779+656j), (174+1006j), (-523+873j), (-962+333j)]

[14]:

Px, ff = psd(sss,2**12, fs)
plot(ff, 10*np.log10(Px))
xlim([15000, 25000])
ylim([-80, 20])

[14]:

(-80.0, 20.0)

../_images/nb_examples_FrequencyShift_15_1.png

[15]:

Px_out, ff_out = psd(gss,2**12, fs)
plot(ff_out, 10*np.log10(Px_out))
xlim([0, 100e3])
savefig('freq_shift_out.png')

../_images/nb_examples_FrequencyShift_16_0.png

[16]:

f, axarr = plt.subplots(2, sharex=True, gridspec_kw={'hspace': 0})
axarr[0].plot(ff_in, 10*np.log10(Px_in))
axarr[0].set_xlim([0, 100e3])
axarr[0].set_ylim([-80, 40])
axarr[1].plot(ff_out, 10*np.log10(Px_out))
axarr[1].set_xlim([0, 100e3])
axarr[1].set_xlabel('Frequency (Hz)')
axarr[0].set_title('Power Spectral Density (dB/Hz)')
f.savefig('freq_shift_inout.png')

../_images/nb_examples_FrequencyShift_17_0.png

Generated Negative Shifted Signal¶

[17]:

%mkdir -p ./neg_shift

[18]:

fqn = FreqShift(x, freq_res, fs, 8, neg_shift=True, output_dir='./neg_shift')

[19]:

fqn.gen_tb(20000)

[20]:

import os
gssn = read_complex_output(os.path.join(fqn.output_dir, fqn.test_output_filename))

[21]:

assert len(gssn) == len(x)

[22]:

sssn = []
for ss in sss:
    sssn.append(ss.real + (ss.imag*-1j))

[23]:

for ii in range(len(gssn)):
    check_res = fqn.x_quant[ii] * sssn[ii]
    check_i = int(check_res.real) >> 8
    assert gssn[ii].real == check_i
    check_q = int(check_res.imag) >> 8
    assert gssn[ii].imag == check_q

[24]:

Px, ff = psd(gssn,2**12, fs)
plot(ff, 10*np.log10(Px))
xlim([0, 100e3])
ylim([-80, 40])

[24]:

(-80.0, 40.0)

../_images/nb_examples_FrequencyShift_26_1.png