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@ -419,6 +419,7 @@ span.mainfunction {color: #993300; font-weight: bolder} |
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{"type":"radioCESSBtransmit_F32","data":{"defaults":{"name":{"value":"new"}},"shortName":"CESSB_Mod","inputs":"1","output":"0","category":"radio-function","color":"#E6E0F8","icon":"arrow-in.png","outputs":"2"}}, |
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{"type":"radioCESSB_Z_transmit_F32","data":{"defaults":{"name":{"value":"new"}},"shortName":"CESSB_Z_Mod","inputs":"1","output":"0","category":"radio-function","color":"#E6E0F8","icon":"arrow-in.png","outputs":"2"}}, |
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{"type":"RadioFMDiscriminator_F32","data":{"defaults":{"name":{"value":"new"}},"shortName":"FMDiscrim","inputs":"1","output":"0","category":"radio-function","color":"#E6E0F8","icon":"arrow-in.png","outputs":"2"}}, |
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@ -3538,6 +3539,11 @@ The actual packets are taken |
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that include file has information relating to this Teensy Audio implementation, as well. |
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</p> |
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<p>This class may not be suitable for directly driving external I-Q hardware |
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mixers. The limited LO-RF isolation of those mixers can introduce a midband tone |
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that will be transmitted. To work around this problem, use the companion |
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class radioCESSB_Z_transmit_F32 that uses the phasing method of SSB generation.</p> |
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<p>The first activity for CESSB is to limit or clip the amplitude of the SSB signal. Internally |
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this always occurs when the envelope of the SSB signal exceeds 1.0. This is all done |
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with floating point arithmetic so values may exceed 1.0. The input level where this occurs |
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@ -3564,7 +3570,150 @@ The actual packets are taken |
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to a communications bandwidth of around 2700 Hz.</p> |
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</script> |
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<script type="text/x-red" data-template-name="radioBFSKModulator_F32"> |
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<script type="text/x-red" data-template-name="radioCESSBtransmit_F32"> |
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<div class="form-row"> |
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<label for="node-input-name"><i class="fa fa-tag"></i> Name</label> |
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<input type="text" id="node-input-name" placeholder="Name"> |
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</div> |
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</script> |
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<script type="text/x-red" data-help-name="radioCESSB_Z_transmit_F32"> |
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<!-- ============ radioCESSB_Z_transmit_F32 ========= --> |
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<h3>Summary</h3> |
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<div class=tooltipinfo> |
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<p>Converts audio into SSB and then applies Dave Hershberger, W9GR, |
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CESSB controlled clipping and |
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filtering. This prevents the SSB peaks from exceeding a maximum level. |
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This increases the peak limited average power by 3 or more dB. The output |
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can be up converted by a RadioIQMixer_F32 object or sent via DAC's as |
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I-Q baseband, ready for quadrature mixer transmit. |
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</p> |
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</div> |
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<h3>Audio Connections</h3> |
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<table class=doc align=center cellpadding=3> |
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<tr class=top><th>Port</th><th>Purpose</th></tr> |
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<tr class=odd><td align=center>In 0</td><td>Input Audio Signal</td></tr> |
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<tr class=odd><td align=center>Out 0</td><td>Baseband SSB I Signal</td></tr> |
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<tr class=odd><td align=center>Out 1</td><td>Baseband SSB Q Signal</td></tr> |
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</table> |
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<h3>Functions</h3> |
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<p class=func><span class=keyword>setSampleRate_Hz</span> |
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(<strong>float32_t</strong> fs_Hz bitRate);</p> |
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<p class=desc>Specifically, this sets the sample rate, in samples per second, |
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that is used by CESSB. It also sets other parameters, such as |
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decimation ratios and filter cutoff frequencies. Thus this function |
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is <strong>required.</strong> At this time, the design is centered |
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on 48000 sps, but can be used with other close values such as |
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44100 or 50000. The plan is to eventually support 96000 sps if users |
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are needing it. There is no default value and the CESSB objects will not run if |
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this function is not called.</p> |
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<p class=func><span class=keyword>getLevels</span>(<strong>int</strong> what);</p> |
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<p class=desc>Returns a pointer to a structure of type levels. This allows |
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knowledge of the average and peak levels at both the input and output sides |
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of the SSB clipper and overshoot compensator. If what==0 the pointer is returned |
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but no updating is done. That is used to setup the process before data is |
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available. If what != 0, the contents of the structure are updated and measuring |
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is reset. The function levelDataCount() below can be used to set the time |
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between updates. The stucture is part of the object and is defined as: |
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<pre> |
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struct levels { |
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float32_t pwr0; // Average power at input |
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float32_t peak0; // Peak voltage at input |
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float32_t pwr1; // Average power at output |
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float32_t peak1; // Peak voltage at output |
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uint32_t countP; // Number of averaged samples for pwr0. |
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}; |
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</pre></p> |
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<p class=func><span class=keyword>levelDataCount</span>();</p> |
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<p class=desc>Returns an uint32_t with the number of averaged samples |
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of the input power. See getLevels() above. The number of output |
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samples may differ by an integer factor because of decimation inside |
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the object.</p> |
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<p class=func><span class=keyword>setGains</span>( |
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<strong>float32_t</strong> gainIn, |
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<strong>float32_t</strong> gainCompensate, |
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<strong>float32_t</strong> gainOut);</p> |
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<p class=desc> These are the controls for the CESSB class. gainIn sets |
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the amount of clipping by setting the input level to the clipper. |
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gainCompensate sets the amount of correction applied to prevent |
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overshoot. A value of 1.4 is normally used. gainOut is |
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for convenience and sets the drive level to the next block. </p> |
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<p class=func><span class=keyword>setSideband</span>(<strong>bool</strong> sbReverse);</p> |
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<p class=desc>The LSB/USB selection depends on the processing of the |
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IQ outputs of this class. But, what we can do here is to reverse the |
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selection by reversing the phase of the Q signal. </p> |
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<p class=func><span class=keyword>setIQCorrections</span> |
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(<strong>bool</strong> useIQCorrection, <strong>float32_t</strong> gainI, |
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<strong>float32_t</strong> crossIQ,<strong>float32_t</strong> crossQI);</p> |
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<p class=desc>This allows small corrections at the output end of the |
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CESSB object, to patch up hardware flaws. The variable useIQCorrection should be |
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<strong>true</strong> to use the corrections. gainI corrects for gain errors between |
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the I and Q channels and should be close to 1.0. |
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The variables, crossIQ and crossQI correct for phase errors and should |
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be close to 0.0. There is interaction between the 3 variables, but |
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converging adjustment to null the unwanted sideband is doable. Either crossIQ or crossQI |
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should end up as 0.0. If use IQCorrection is false, there is no processor |
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load for corrections.</p> |
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<h3>Examples</h3> |
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<p class=exam>File > Examples > OpenAudio_ArduinoLibrary > CESSB_ZeroIF |
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</p> |
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<h3>Notes</h3> |
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<p>The technical description, implementation and test results are in references |
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listed in the include file for this class, |
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<a href="https://github.com/chipaudette/OpenAudio_ArduinoLibrary/blob/master/radioCESSBtransmit_F32.h" |
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target="_blank">available from Github</a> |
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These should be used to understand the details of CESSB. The notes at the top of |
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that include file has information relating to this Teensy Audio implementation, as well. |
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</p> |
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<p>The first activity for CESSB is to limit or clip the amplitude of the SSB signal. Internally |
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this always occurs when the envelope of the SSB signal exceeds 1.0. This is all done |
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with floating point arithmetic so values may exceed 1.0. The input level where this occurs |
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depends on the setting for gainIn, described above. The maximum level seen ahead of the clipper |
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is measured by getLevels() as described above. One way to control the input to the CESSB block |
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is with |
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<a href="http://www.janbob.com/electron/OpenAudio_Design_Tool/index.html?info=AudioEffectCompressor2_F32" |
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target="_blank">Compressor2 Library block.</a> Note that Compressor2 |
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is not a clipper, but is rather an automatic gain control that uses look-ahead |
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processing to allow gradual gain changes. |
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</p> |
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<p>The output of the CESSB processing is the in-phase and quadratuere components |
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(I-Q) of the SSB signal that has the suppressed carrier at zero frequency. |
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This can be translated to higher frequencies, either by a RadioIQMixer_F32 |
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object, or by feeding through a pair of DAC's to quadrature hardware mixers. This |
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produces either an Upper Sideband (USB) or a Lower Sideband (LSB) signal. The sideband |
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can be selected in various ways, including the function for this class, setSideband() |
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described above.</p> |
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<p>Note the companion class, RadioCESSBtransmit_F32, that uses the Weaver-method |
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as is done used |
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in the referenced Hershberger documents. The performance of the two classes is |
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very similar. This version removes concerns about mid-band spurious tone generation |
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when used with hardware mixers.</p> |
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<p>CESSB as implemented here is intended for voice input, and also filters the voice |
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to a communications bandwidth of around 2800 Hz.</p> |
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<p>The Hilbert filter used with this class will provide high opposite |
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sideband rejection down to about 150 Hz. It is using 201 coefficients at a sample |
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rate of 12000. Still, for some situations it may be desireable to use an IIR |
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high pass filter on the input audio.</p> |
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</script> |
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<script type="text/x-red" data-template-name="radioCESSB_Z_transmit_F32"> |
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<div class="form-row"> |
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<label for="node-input-name"><i class="fa fa-tag"></i> Name</label> |
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<input type="text" id="node-input-name" placeholder="Name"> |
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