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digaree
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feedforward
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hosted
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lo_lut
lo_lut
 
 
moving_average
moving_average
 
 
Makefile
Makefile
 
 
README.md
README.md
 
 
TinyEVG.html
TinyEVG.html
 
 
afterburner.awk
afterburner.awk
 
 
afterburner.gtkw
afterburner.gtkw
 
 
afterburner.v
afterburner.v
 
 
afterburner_tb.v
afterburner_tb.v
 
 
async_to_sync_reset_shift.v
async_to_sync_reset_shift.v
 
 
banyan.v
banyan.v
 
 
banyan_ch_find.py
banyan_ch_find.py
 
 
banyan_mem.gtkw
banyan_mem.gtkw
 
 
banyan_mem.v
banyan_mem.v
 
 
banyan_mem_tb.v
banyan_mem_tb.v
 
 
banyan_readme.txt
banyan_readme.txt
 
 
banyan_tb.v
banyan_tb.v
 
 
banyan_topo.eps
banyan_topo.eps
 
 
biquad.gtkw
biquad.gtkw
 
 
biquad.v
biquad.v
 
 
biquad_tb.v
biquad_tb.v
 
 
ccfilt.v
ccfilt.v
 
 
cic_interp.v
cic_interp.v
 
 
cic_multichannel.gtkw
cic_multichannel.gtkw
 
 
cic_multichannel.v
cic_multichannel.v
 
 
cic_multichannel_tb.v
cic_multichannel_tb.v
 
 
cic_simple_us.gtkw
cic_simple_us.gtkw
 
 
cic_simple_us.v
cic_simple_us.v
 
 
cic_simple_us_tb.v
cic_simple_us_tb.v
 
 
cic_wave_recorder.gtkw
cic_wave_recorder.gtkw
 
 
cic_wave_recorder.v
cic_wave_recorder.v
 
 
cic_wave_recorder_tb.v
cic_wave_recorder_tb.v
 
 
cim_12x.v
cim_12x.v
 
 
circle_buf.gtkw
circle_buf.gtkw
 
 
circle_buf.v
circle_buf.v
 
 
circle_buf_serial.gtkw
circle_buf_serial.gtkw
 
 
circle_buf_serial.v
circle_buf_serial.v
 
 
circle_buf_serial_tb.v
circle_buf_serial_tb.v
 
 
circle_buf_tb.v
circle_buf_tb.v
 
 
complex_freq.gtkw
complex_freq.gtkw
 
 
complex_freq.v
complex_freq.v
 
 
complex_freq_tb.v
complex_freq_tb.v
 
 
complex_freq_wrap.v
complex_freq_wrap.v
 
 
complex_mul.gtkw
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complex_mul.v
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complex_mul_flat.gtkw
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double_inte.v
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double_inte_smp.v
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doublediff.v
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doublediff1.v
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dpram.v
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dpram_tb.v
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fchan_subset.v
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fdownconvert.v
fdownconvert.v
 
 
fifo.v
fifo.v
 
 
fifo_2c.v
fifo_2c.v
 
 
filter_test.py
filter_test.py
 
 
fiq_interp.v
fiq_interp.v
 
 
flag_xdomain.v
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flevel_set.v
flevel_set.v
 
 
freq_count.gtkw
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freq_count.v
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freq_count_tb.v
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freq_gcount.v
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fwashout.v
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half_filt.py
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iirFilter.v
 
 
iirFilterDoc.html
iirFilterDoc.html
 
 
iirFilter_tb.v
iirFilter_tb.v
 
 
interp1.v
interp1.v
 
 
iq_chain4.gtkw
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iq_chain4.v
iq_chain4.v
 
 
iq_chain4_tb.v
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README.md

Digital down-conversion

The down-conversion here is different from a typical down convert module in the sense that resulting stream of IQs are at half the data rate of the ADCs. And the low-pass filter that is applied after a typical down-conversion to get rid of the sum frequency, in our case, is nothing but an implicit decimation filter (hence the half data rate).

The detailed description of the mathematics behind it is written in a note by Larry Doolittle here.

Source code in fdownconvert.v. The gist is as follows:

  1. Mix an Intermediate Frequency generated from a DDS (DDS here comes from a CORDIC).
  2. Perform the matrix computation to extract I and Q.
  3. Note that the pipeline generates one I,Q pair per 2 ADC samples. Essentially, decimating the data.
  4. The IQ samples are then interleaved into a single data stream, maintaining n bits/sec IN and n bits/sec OUT.

IQ interpolation

Takes an interleaved IQ data stream at X samples per sec, and outputs 2 data streams I and Q at X samples per sec each. Does so by interpolating them.

Code

Level set

Dot product of the LO signal with (I-Q) baseband data/signal. This module is used to generate the real or imaginary components of the upconversion.

Code

Afterburner [secant interpolation]

SSB Out [up-conversion]

The goal here is to upconvert the feedback loop output IQ baseband stream to a DAC output stream. The IQ stream is running at half the data rate (see down-conversion above) assuming the DACs are running at the same frequency as the ADCs.

  1. Input of an IQ interleaved data stream.
  2. Perform IQ interpolation (described above) to bring the interleaved data stream up to regular rate.
  3. Upconvert the data by multiplying the IQ datastream with LO, use level set to generate Real and Imaginary components.
  4. Use afterburner.v to interpolate the mid-points of the IQ streams.

Code