Corrected comments

boblark 4 months ago
parent 236f52e610
commit 6f92abdc7e
  1. 3
  2. 62

@ -75,7 +75,8 @@ void radioCESSBtransmit_F32::update(void) {
/* A +/- pulse to test timing of various delays. PULSE TEST
* This replaces any input from the audio stream
* This replaces any input from the audio stream,
* and levels shown are for gainIn==1.0.
for(int kk=0; kk<128; kk++)
uint16_t y=(ny & 1023);

@ -6,66 +6,8 @@
* Chip Audette (OpenAudio) Feb 2017
* and of course, to PJRC for the Teensy and Teensy Audio Library
* The development of the Controlled Envelope Single Side Band (CESSB)
* was done by Dave Hershberger, W9GR. Many thanks to Dave.
* The following description is mostly taken
* from Frank, DD4WH and is on line at the GNU Radio site, ref:
* Controlled Envelope Single Sideband is an invention by Dave Hershberger
* W9GR with the aim to "allow your rig to output more average power while
* keeping peak envelope power PEP the same". The increase in perceived
* loudness can be up to 4dB without any audible increase in distortion
* and without making you sound "processed" (Hershberger 2014, 2016b).
* The principle to achieve this is relatively simple. The process
* involves only audio baseband processing which can be done digitally in
* software without the need for modifications in the hardware or messing
* with the RF output of your rig.
* Controlled Envelope Single Sideband can be produced using three
* processing blocks making up a complete CESSB system:
* 1. An SSB modulator. This is implemented as a Weaver system to allow
* minimum (12 kHz) decimated sample rate with the output of I & Q
* signals (a complex SSB signal).
* 2. A baseband envelope clipper. This takes the modulus of the I & Q
* signals (also called the magnitude), which is sqrt(I * I + Q * Q)
* and divides the I & Q signals by the modulus, IF the signal is
* larger than 1.0. If not, the signal remains untouched. After
* clipping, the signal is lowpass filtered with a linear phase FIR
* low pass filter with a stopband frequency of 3.0kHz
* 3. An overshoot controller . This does something similar as the
* envelope clipper: Again, the modulus is calculated (but now on
* the basis of the current and two preceding and two subsequent
* samples). If the signals modulus is larger than 1 (clipping),
* the signals I and Q are divided by the maximum of 1 or of
* (1.9 * signal). That means the clipping is overcompensated by 1.9
* which leads to a much better suppression of the overshoots from
* the first two stages. Finally, the resulting signal is again
* lowpass-filtered with a linear phase FIR filter with stopband
* frequency of 3.0khz
* It is important that the sample rate is high enough so that the higher
* frequency components of the output of the modulator, clipper and
* overshoot controller do not alias back into the desired signal. Also
* all the filters should be linear phase filters (FIR, not IIR).
* This CESSB system can reduce the overshoot of the SSB modulator from
* 61% to 1.3%, meaning about 2.5 times higher perceived SSB output power
* (Hershberger 2014).
* References:
* 1-Hershberger, D.L. (2014): Controlled Envelope Single Sideband. QEX
* November/December 2014 pp3-13.
* 2-Hershberger, D.L. (2016a): External Processing for Controlled
* Envelope Single Sideband. - QEX January/February 2016 pp9-12.
* 3-Hershberger, D.L. (2016b): Understanding Controlled Envelope Single
* Sideband. - QST February 2016 pp30-36.
* 4-Forum discussion on CESSB on the Flex-Radio forum,
* Weaver Method of SSB: Note that this class includes a good umplementation
* of the Weaver method. To use this without invoking the CESSB corrections,
* just keep the input peak level below 1.0. One could disable CESSB by