GC_ET_Circuit-Function.html

2019-10-25   19:58:32

 aimg_Morse-Man



*(: GC_ET_Circuit-Function.txt

involving a short discussion of each module in the circuit function.

Below:  Transient Plot shows Phase Delays and inter-actions. 
Triple-Signals are phase-shifting across time. 
Note: AF10 forces phase shifting and produces a symetrical signal
.
Note: AF10 (blue) responds to the beat frequencies with peaks and nulls in its output. 
PD1-2-TS-24ms-150803-0800.jpg


The initial Problem for this Research Project :

In C.W. (morse-code) radio operations 
we may have three signals within a 100Hz passband.  
Say 650Hz, 700Hz , 750Hz.  
Commonly we listen for a 700Hz signal tone,  
but also hear signals +/- 50 Hz, +/- 150 Hz, +/- 250 Hz, 
which can make accurate copy of the 700 Hz target signal difficult. 
Therefore we design Narrow CW Audio Filters,   
to pass only the 700Hz signal tone +/- 50 Hz. 


Also, and frequently, adjacent signals are 30 dB louder than the target signal 
...  and these strong adjacent signals need to be severly attenuated for clear hearing.

Having several Morse Code signals at nearly the same audio pitch is Very confusing to the ear/brain. 
Our ear/brain system only wants to hear one of them ... the 700Hz signal.   


This project is concerned with designing a very selective CW Audio Filter. 

Our method  may be described as phasing-out the odd signals ; 
ie,  controlling / comparing / differentiating  the phases 
of the signals passing through the circuit. 
... so the final stages can "phase-out" the un-wanted signals  ( below 650 Hz  and  750 Hz above)
... and "phase-in" the target signal ( 700 Hz ) .

 
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Note on use of the Multiple-FeedBack BandPass Filter Topology:

From Wiki:
The Butterworth filter is a type of signal processing filter
designed to have as flat a frequency response as possible in the passband.
It was first described in 1930 by the British engineer and physicist Stephen Butterworth
in his paper entitled "On the Theory of Filter Amplifiers".

A design advantage of this 'MFB' topology is
that a single resistor can be used to control the f(0).

Method In the Filtering Stages of this circuit. 

* The Four filters progressively produce the band-width narrowing down to aprox. 100Hz @ -3dB, 150Hz at -12dB.  
* The Four Filters produce a phase relationship between Fx01 and Fx04 that can be Differentiated (subtracted)  
   to produce -48 dB notches +/- 175 Hz, and having a -48 dB stopband to the limits.  
* The Notches are -25 dB below the fourth filter Fx04. 
* The Fx05 un-tuned Differential final 'filter' subtracts the Fx01 and inverted signal at Fx04 
   and is the "final" stage for the Double-Notched Narrow-Signal Out. 




* Functional Modules : 

* The PreAmp is the initial gain control, and allows driving the Limiter into "turn-on" by user control. 

* The Roofing Triad Filter is the first module in the "AFX" circuit. 
   The Wide Roof has -26 dB Octave Roll-Off from Three OpAmps.

Note on Roofing Filter Rationale : 
* Sharply peaked preliminary band-pass signals would alter the phases of the various signals delivered to the Quad Filters.  
* A flat-topped preliminary signal, with steep sidebands  will allow the central signals 600 , 700, 800 
    to be passed through without distortion.  
* This approach allows the Roofing Filter to be an independent module and not require exact tuning. 
* This approach attenuates possible strong signals outside of the 350 Hz PassBand of interest.  

* The Roofing-Triad-Differential Filter has the function of :
(1) producing symetrical waveforms so the InterModulation Distortion is minimized in the fast acting Diode Limiter.  
(2) attenuating preliminary signals that are outside the desired passband ( outside of 600Hz to 800Hz )
.... this reduces the interference of strong adjacent signals, and reduces the potential overloading of the diode limiter,  thus reducing IMD.  

* The "AFX" Active Limiter has effective pulse noise reduction 
   and AGC features not found in vintage noise limiters, 
with minimal IMD. 

* The "AFX" MFB Quad Butterworth filters have a sequence of calculated "Q" 
   which reduces the transfer of Phase-Delay artifacts on the edge of the pass-band. 

* The Differential-Dual-Notch-Generator stage  produces Dual-Notches around the f(0) center frequency. 
   ... Simply, where the Fx01 and Fx04 signals cross each other, 
   the Differential Amp will see Zero Volts Difference and Produce "Dual-Notches".  

* The Integrated stage   produces a flat-topped Narrow passband ( not included in all schematics).

* The Audio stage was designed to produce a more "crisp" audio signal.

* The whole "AFX" circuit of some 20 opamps is easily tuned and adjusted.  
    

These are the main "AFX" results : 
(1) Active control of the Limiting Function, with minimal IMD. 
(2) Narrow Filtering of original passband, down to a narrow passband. 
(3) "Narrow +Double-Notch" waveforms. 

My prototype circuit functions to allow 
use of all these results in my daily radio operations. 

"AFX" project has been an extreme enhancement functionally 
to my transceiver for receiving CW (morse code) on the Amateur Radio Bands. 

I found each module to be a study of its own 
... each has been intriguing, and captivating, useful, rewarding.  

 

********************************************************************************

Fundamental Transfer Function  for the Multi-FeedBack BandPass Filter .
R(2) is the Resonant Loading resistor used for minor tuning of f(0) +/- 20%  .
Herein, we refer to this R(2) as R(freq) and it is the primary adjustment component.  

 MFB_BPF_equations_TI_.png

 
Below:  Transient Plot shows Phase Delays and inter-actions. 
Triple-Signals are phase-shifting across time. 
Note: AF10 forces phase shifting and produces a symetrical signal
.
Note: AF10 (blue) responds to the beat frequencies with peaks and nulls in its output. 
PD1-2-TS-24ms-150803-0800.jpg

 

*****************************************************************

 

 

 

The AFX project functions within the context of Amateur Radio C.W. (morse-code) operations, 
to produce narrow pass-band filtering, for the purpose of greater clarity in 'hearing' the message.   

Another way to look at equations

 AFX_equation_Band-Pass-Function_.png




*****************************************************************



Practical single stage calculations : 
from  http://www.k7mem.com   _Band-Pass-Filter-Calcs__ 

Download this  XLS  spreadsheet file from Audet in  ZIP format.  by J. Audet, VE2AZX

Download this  spreadsheet file from Audet in  MicroSoft XLS  format.    

Download this  spreadsheet file from Audet in  Linux ODS OpenOffice  format.    

 

Spice via Browser on the Internet :  http://www.partsim.com/
 

**************************************************************************************************************
This experimental project is an "Exotic" circuit !

For an initial discussion , go to this URL on the internet : 
  
Published at : "Do 'Exotic' amplifiers even exist?"  - ResearchGate.  Available from: 
https://www.researchgate.net/post/Do_Exotic_amplifiers_even_exist?_tpcectx=search  

Vasile Surducan asked a question:

Do "Exotic" amplifiers even exist?

Based on your experience as researchers, engineers or teachers involved in electronics, 
perhaps you have seen electronic designs which puzzled you 
trying to understand how and why those works.
Acording to Miriam Webster dictionary http://www.merriam-webster.com/dictionary/exotic,  
"exotic" means: very different, strange, or unusual. 
The term is coming from Latin exoticus, from Greek exōtikos, 
and it's first known use is 1599. Good synonims for "exotic" are bizarro or fantastic.    :)
I have opened this topic as an answer to Cyril Mechkov and his topic:  
"What is the truth about the exotic current feedback amplifier?" 
you are encouraged to post here the "exotic" amplifier structures 
(links or papers) you have experimented and tested in your real life 
trying to understand everything about those.


******************************************************************************************************************

 

 

 

*************   AFX ***   The BASIC Rationale  *********************
   

Introduction:        Audio-Filter-Xperiment 

Audio Filter Experiment for copying pulse CW Morse-Code on the Amatuer Radio Bands.  

This is a Research Project about  Phase-Filters for Narrow Channel CW reception. 

This Project started from a Discussion on the  Yahoo Groups HW8 site.  

This Project eventually ended up on the  Research Gate .Net website, 

 with many contributions from Electronic Engineers from around the world,  

with special mention of  Dr. Barrie Gilbert, Director of Invention, at  Analog Devices Inc.,  

and  Dr. Dobromir Dobrev, Professor,  at Bulgarian Academy of Sciences. 

 This is a Study about Differential Phase-Filters and includes these topical sections : 
  Roofing Triad Filter  & Active Log-Limiter  &  MultiFeedBack Filters  &  Dual-Notch Differential Phase Filters  &  Audio Amp.           

       *** 
       *** Designed for Easy Construction and Easy tuning and Superior CW Narrow Audio Filtering. 
       *** Constructed and used daily for Amateur Radio CW (morse code) Operations on the Radio Bands, a "proven design". 
       *** The AFX CW audio filtering has been measured and is near Digital Signal Processing quality as presented to the Ear.
       *** The vintage  LM324 OpAmp was chosen because 
             the project frequency response and gain requirements are within bounds.

       *** Note that OpAmp null and balance trim-pots are not shown, and common by-pass caps not shown. 
       ***    (1) for simplification
       ***    (2) circuit designs are self-balancing and produce symetrical waveforms, as is.
 

*** This developing topic has evolved into the AFX'V' project  
*** (linked on home-page of this website) which provides much testing diagrams/methods.   

***********************************************************************  
Still Developing Discussion 

(note: 

( this website & project does not contain an in-depth presentation 
( of basic Delyanis-Friend Multi-Feed-Back Filter  nor any tutorial 
( nor their academic math basis.  

Fundamental Transfer Function  for the Multi-FeedBack BandPass Filter .
R(2) is the Resonant Loading resistor used for minor tuning of f(0)  .
 

 ET_MFB_TranFunc_OPtBaD.jpg


 

Fundamental developments were made in Dual-Notch Phase-Filtering
*** ( 
the Dual-Notches function which are a Key Feature of this project. 
*** ( this section is still being written and revised .

Another way to look at equations

AFX_equation_Band-Pass-Function_.png

Practical single stage calculations : 
from  http://www.k7mem.com/Electronic_Notebook/filters/act_bpfil.html  

Download this  XLS  spreadsheet file from Audet in  ZIP format.  by J. Audet, VE2AZX

Download this  spreadsheet file from Audet in  MicroSoft XLS  format.    

Download this  spreadsheet file from Audet in  Linux ODS OpenOffice  format.    

 

**************************************************************************************************************************

*** (!)  Frequently you will encounter the "Anti-Parallel Diodes" 
as a Negative-Feedback element. 

 

AFX_Hewlett-Resistor_parallel-diodes-opposed_.png 

***  My documentation includes many references to a "v" ('variance') number. 
***   [  "v" = sideband slope of best fit   is  calculated by  : 
           ( (BW@-12dB) - (BW@-3dB ) / (9dB)  )    ]    
*** Variance is a better descriptor of the Non-Gaussian BandPass curves than the "Q" factor. 

 

**************************************************************************************************************
For an initial discussion , go to this URL on the internet : 
  
Published at :  Do "Exotic" amplifiers even exist? - ResearchGate.  Available from: 
https://www.researchgate.net/post/Do_Exotic_amplifiers_even_exist?_tpcectx=search  

 

Vasile Surducan asked a question:

Do "Exotic" amplifiers even exist?

 



Based on your experience as researchers, engineers or teachers involved in electronics, 
perhaps you have seen electronic designs which puzzled you 
trying to understand how and why those works.



Acording to Miriam Webster dictionary http://www.merriam-webster.com/dictionary/exotic,  
"exotic" means: very different, strange, or unusual. 
The term is coming from Latin exoticus, from Greek exōtikos, 
and it's first known use is 1599. Good synonims for "exotic" are bizarro or fantastic.    :)

I have opened this topic as an answer to Cyril Mechkov and his topic: 
"What is the truth about the exotic current feedback amplifier?"

You are encouraged to post here the "exotic" amplifier structures 
(links or papers) you have experimented and tested in your real life 
trying to understand everything about those.

******************************************************************************************************************