2021-01-06   10:37:32

Computer                      the "P2D"  page


"Parallel 2 Differential "   radically different   Dual-Channel CW Audio Filters      


The designed advantages coming from the P2D approach are :
1) a flat-topped "W"ide Passband, for easier capture of  CW signals.
2) a "N"arrow Passband with extremely steep sideband skirts,  
3) uses Parallel Filters followed by un-tuned
Differential stages
4) if followed by a MFB Q=7 stage, then a single R(freq) can vary the f() narrow passband frequency.


Note:  In the following diagrams, R2 to Virtual Ground is the R(freq) for adjusting f(center)
Note: the -3dB level is equivalent to the 700 mV level in these Bode Plots.


List: April 10, 2015, gae

P2D-P33D-P44D Special Differentiated Stages to replace Filter stages. 

P2D-DIF-WN  Special Differentiated Stages to replace Filter stages. 


Special Differentiated Stages to replace Filter stages. 
Two Tuned Summing Stages
replaced by  Two Un-Tuned Differentiation Stages.
Same Results !!!  



Plot of Transient Analysis, Sine Input,
showing Phase-Shifting to obtain the required Band-Pass. 



P2D-P77D-P55D- for extremely steep "N" sidebands. 
Special Differentiated Stages to replace Filter stages. 
Two Tuned Summing Stages 
replaced by  Two Un-Tuned Differentiation Stages.
Same Results !!! 

First Triad is Q=7 +/- 50 Hz , then Differentiated.
Second Triad is Q=5 +/- 25 Hz , then Differentiated. 

First Triad is "W"ide  v=15, extremely steep for a "W"ide Filter.

Second Triad is "N"arrow  v=9.5 !!!   Close to DSP and already analog for Audio Output.  
At +/-90 degrees from f(700) the signal is near -48dB down. 



Differential Traces are :  "W"ide GREEN .  "N"arrow Black .
There are two passbands for "W" and two passbands for "N", each followed by a Differential Stage.  

Signal injected was "Noise".  
Shown is the effectiveness of a Differentiator in eliminating Common Mode noise signal.


*** Conclusions about the  P2D design approach :  
The Parallel designs  have been intriguing to develop. 
These are really radical 'techy' circuits and good to brag about. 
* The 12 stage (
P2S-QAA-P445)  circuit produces a "N"arrow filter output 
that compares favorably with DSP (after run through a DAC for the earphone signal). 
but are very ticky to construct and tune.  

* The P2D-DIF designs are much simpler, easy to tune, and produce passbands similar to DSP.

* The    AFX-RSF-S4-Q7   version #8  Filter circuit could be improved by using the P2D-DIF filter section. 

AFX , with (1) Roofing stage based on P2D triad, (2) driving the log-limiter,
(3) driving 
the Quad Filter Stage , (4)  followed by the "W" Integrated and "N" Differentiated Stages 
can produce   excellent  results,   and   is a well-developed good-working project.   
AFX "W"ide and "N"arrow stages produce similar results, and is 
much better for building and tuning.    

That is the author's General Conclusion.