Did You Hear of Such an AM Receiver? For DSB-Suppressed Carrier.

[KerimF]

I don't think people are uninterested, it's just that what you are discussing might be seen as a "curiosity" of limited relevance in the real world.

Yes, what you say here is indeed true.
In fact, in the real world, if a person who never served certain powerful rich families (owners of a big company or corporation for example), his work would have no relevance in the real world.
But my personal observation may be wrong if you can help me know a famous inventor who wasn't working under the direction of certain big heads (unless his family is rich and famous already).

Yes, it is interesting and intriguing, but if you are hoping to see the world of broadcast radio adopt this technology en masse, you will surely be disappointed. Another way to express it is that it looks a bit like a solution looking for a problem.

It happens that, since I was in schools then universities, I studied hard while respecting always my teachers, good and evil, to get enough knowledge that helps me gain my living in the least while being really independent. To me, my independence is worth more than all treasures of the world. So, I was never tried to be rich (hired for a high-salary job for example) and lose it (naturally, this disappointed all my relatives who use to run after money). In my private business (since 1975 till now) I try my best that my various designs and products please my local customers, not the world.

So, I have the impression that I did a big mistake to share my work here. Should this thread be removed? The moderators have the answer.

...earlier on I asked why the carrier is frequency modulated, but I simply didn’t understand the answer. 

You didn't... because you likely didn't also hear of the two known topologies for the DSB-SC demodulators, Costas Loop and the Squaring method. Both cannot track the frequency of the suppressed carrier if it varies in a relatively wide spectrum. This is why I deliberately modulated, with exaggeration, the frequency of the carrier to show, clearly, to the academic professionals in RF communications around the world that their two known topologies are things of the past if they are rational and realistic, are they?

In a real application, the frequency of the carrier doesn't need to be modulated, unless there is a need to also send a low-rate data (as FM) while the AM transmission is active.

[KerimF]

A few times earlier I raised the following question, following the French style (no options):
What is the effective bandwidth of an RF channel that uses an FM-AM signal (the carrier is AM and FM modulated at the same time)?

I repeated it here by following the American style. Now you can select the right answer:

[1] BW_am + BW_fm
[2] BW_am
[3] BW_fm
[4] BW_am + BW_fm/2
[5] BW_am/2 + BW_fm
[6] (BW_am + BW_fm)/2

Cheers

Added: We can assume that BW_fm < BW_am

[radiolistener]

but if you are hoping to see the world of broadcast radio adopt this technology en masse

It is not allowed, since transmission with 80 kHz bandwidth on short wave is not allowed, such transmission just occupies the entire broadcast band, no worse than a jammer, since FM modulation provides constant power in entire operating bandwidth. Thus, one such station will jam dozens of other broadcasting stations. With no any kind of benefit. It will need 8x times more power for transmission and complicated demodulator to receive it.

And I suspect it will be much more sensitive to a multipath propagation issues on short wave than a usual FM modulation with much less bandwidth. It will be also very sensitive to a moving transmitter/receiver due to Doppler effect.

I see it this way: this type of modulation has all the disadvantages of both AM and FM modulation, but does not add any advantages. On the contrary, it takes up too much bandwidth.

[mawyatt]

Almost all communications systems today are digital, wether wired, optical or wireless. Over the past half century considerable effort has gone into pushing as many bits as fast as possible thru these communication channel limits utilizing all sorts of modulation schemes employing AM, FM, PM and various combinations of such.

Unless one can improve the through-put/spectral efficiency of modern digital comms and stay within the regulations, any "new" ideas are likely to fall on deaf ears!!

Best

[KerimF]

but if you are hoping to see the world of broadcast radio adopt this technology en masse

It is not allowed, since transmission with 80 kHz bandwidth on short wave is not allowed, such transmission just occupies the entire broadcast band, no worse than a jammer, since FM modulation provides constant power in entire operating bandwidth. Thus, one such station will jam dozens of other broadcasting stations. With no any kind of benefit. It will need 8x times more power for transmission and complicated demodulator to receive it.

And I suspect it will be much more sensitive to a multipath propagation issues on short wave than a usual FM modulation with much less bandwidth.

What could I add? when someone doesn't have time to read all my replies like the one in the recent post #50 in which I answered the same question and ended it with:

In a real application, the frequency of the carrier doesn't need to be modulated, unless there is a need to also send a low-rate data (as FM) while the AM transmission is active.

[coppice]

Almost all communications systems today are digital, wether wired, optical or wireless. Over the past half century considerable effort has gone into pushing as many bits as fast as possible thru these communication channel limits utilizing all sorts of modulation schemes employing AM, FM, PM and various combinations of such.

Unless one can improve the through-put/spectral efficiency of modern digital comms and stay within the regulations, any "new" ideas are likely to fall on deaf ears!!

Best

Yep. For pretty much any comms idea right now you have to ask the question "is this competitive with OFDM, or so astonishingly low power it can carve out a niche?".

[radiolistener]

Added: We can assume that BW_fm < BW_am

No, FM modulation requires much more bandwidth for the same message signal dynamic range than AM modulation.
AM modulation just use double bandwidth of the message signal. This is why FM is not used on short wave, where bandwidth is very limited.

FM modulation is very complicated for math analysis due to it's non-linear properties, but as I know it requires about 10x times more bandwidth than message signal in order to keep dynamic range and bandwidth of the message signal at good quality with low distortions.

The most effective analog modulation is SSB (LSB or USB). Its bandwidth is equal to a message bandwidth. And it also very efficient from power point of view, since it don't need to transmit something when there is DC on message signal input.

[KerimF]

Almost all communications systems today are digital, wether wired, optical or wireless. Over the past half century considerable effort has gone into pushing as many bits as fast as possible thru these communication channel limits utilizing all sorts of modulation schemes employing AM, FM, PM and various combinations of such.

Unless one can improve the through-put/spectral efficiency of modern digital comms and stay within the regulations, any "new" ideas are likely to fall on deaf ears!!

Best

Sorry, aren't you suggesting that almost all analogue solutions in RF communications need to be removed now from the university's textbooks?
Or just the new ones are not supposed to be added to the old obsolete solutions (like of Costas and Squaring method) that the undergraduate students have to hear of, despite they are no more useful in today's digital world.

Sorry, if I couldn't understand you well.

[KerimF]

Added: We can assume that BW_fm < BW_am

No, FM modulation requires much more bandwidth for the same message signal dynamic range than AM modulation.
AM modulation just use double bandwidth of the message signal. This is why FM is not used on short wave, where bandwidth is very limited.

The most effective analog modulation is SSB (LSB or USB). Its bandwidth is equal to a message bandwidth. And it also very efficient from power point of view, since it don't need to transmit something when there is DC on message signal input.

It looks here as if we live on the famous Babylon Tower on which no one understand what another says

I agree with you, but it seems to me that you didn't notice it was just an academic question. You don't need to know its right answer.

[radiolistener]

What could I add? when someone doesn't have time to read all my replies like the one in the recent post #50 in which I answered the same question and ended it with:

In a real application, the frequency of the carrier doesn't need to be modulated, unless there is a need to also send a low-rate data (as FM) while the AM transmission is active.

Sorry, but I don't see any explanation of advantage of such DSB modulation with FM modulated carrier in the post #50.

If you remove FM modulation for the carrier your modulation turns into a usual DSB, isn't it?

[mawyatt]

Sorry, aren't you suggesting that almost all analogue solutions in RF communications need to be removed now from the university's textbooks?
Or just the new ones are not supposed to be added to the old obsolete solutions (like of Costas and Squaring method) that the undergraduate students have to hear of, despite they are no more useful in today's digital world.

Sorry, if I couldn't understand you well.

Seems you are the one suggesting, example your new revolutionary DSB-SC modulation scheme. We are certainly not suggesting remove anything in the Electronics 101 Texts as one needs to understand the modulation fundamentals of AM, FM and PM before venturing into the more complex and spectral efficient modulation schemes in use today.

Best

[SteveThackery]

So, I have the impression that I did a big mistake to share my work here. Should this thread be removed? The moderators have the answer.

This is the third time you've said something that gives me the impression that there might be a chip on your shoulder, which is motivating you to try to prove that you are smarter than most of the established "experts" in the field over the past 70-odd years.

This is why I deliberately modulated, with exaggeration, the frequency of the carrier to show, clearly, to the academic professionals in RF communications around the world that their two known topologies are things of the past if they are rational and realistic, are they?

Yes, there you go again - a perfect example of what I've just said. Three things: firstly, the "academic professionals in RF communications around the world" aren't listening, and they won't listen unless you can come up with something compelling that delivers some major step forward.

Secondly, I think you are seriously underestimating these academic professionals.

Thirdly, and the showstopper: these professionals would be the first to agree that the "two known topologies" are indeed a thing of the past! Of course they are! Radio communications are digital almost everywhere APART from the legacy stuff that is a continuation of services that have been running since decades past. Nobody cares about AM, FM, SSB, DSB, suppressed carriers - they are mid-20th century technology and the world has moved on.  21st century broadcast television is digital; 21st century broadcast radio is digital.

If you really want to demonstrate how smart you are, invent something better than OFDM and the associated protocols in the stack. Arguing the toss over something that is 40 years obsolete isn't going to impress anyone.

[KerimF]

So, I have the impression that I did a big mistake to share my work here. Should this thread be removed? The moderators have the answer.

This is the third time you've said something that gives me the impression that there might be a chip on your shoulder, which is motivating you to try to prove that you are smarter than most of the established "experts" in the field over the past 70-odd years.

Sorry, you remind me when I faced to be sent to jail when, in the 80's, I presented my work in real (both my FM-AM DSB-SC transmitter around 1Mhz on MW band, and my receiver) to the local authorities at the National Military headquarters in the capital. My crime, as you said, was my claim to know something not known in the West. They refused to verify my claim in any way and insisted that I was an ignorant dreamer. Yes, they used to believe (still do) that the West has gods, and I was seen, therefore, as a blasphemer towards those gods and deserve to be punished. Fortunately, my mind recalled what happened to Galileo (I hope you heard what happened to him). So, in a hurry, I apologized and asked their forgiveness for wasting their time with an ignorant dreamer and this was the Happy End. They were glad and proud for being right and they allowed me to return home, sane and safe.
Soon later, I installed the proper antennas, at home and workplace, and established a two-way scrambled RF link between the two. My links were heard just as an intermittent noisy interference for many months (as I explained earlier) when I decided to stop it and use instead the FM band (also as I explained earlier). The trick on FM band was better and it wasn't noticed for many years till I got a phone line at home which was located in a poor neighborhood.
 
In brief, since you also cannot verify what I say (it is not your field of interest), just tell me what you like me to tell you that lets you feel fine towards me, unless you have no choice but to insist, I am an ignorant blasphemer.

[KerimF]

Sorry, aren't you suggesting that almost all analogue solutions in RF communications need to be removed now from the university's textbooks?
Or just the new ones are not supposed to be added to the old obsolete solutions (like of Costas and Squaring method) that the undergraduate students have to hear of, despite they are no more useful in today's digital world.

Sorry, if I couldn't understand you well.

Seems you are the one suggesting, example your new revolutionary DSB-SC modulation scheme. We are certainly not suggesting remove anything in the Electronics 101 Texts as one needs to understand the modulation fundamentals of AM, FM and PM before venturing into the more complex and spectral efficient modulation schemes in use today.

Best

Anyway, I guess I am guilty, in the eyes of some members here, for saying that my analog solution is better, simpler and more reliable, than the two known ones by the world.

But I will have no reason not to believe someone who will test it, in real, and say it is not better than the ones he used to know.

[KerimF]

What could I add? when someone doesn't have time to read all my replies like the one in the recent post #50 in which I answered the same question and ended it with:

In a real application, the frequency of the carrier doesn't need to be modulated, unless there is a need to also send a low-rate data (as FM) while the AM transmission is active.

Sorry, but I don't see any explanation of advantage of such DSB modulation with FM modulated carrier in the post #50.

If you remove FM modulation for the carrier your modulation turns into a usual DSB, isn't it?

No, it will be always a DSB-SC signal which the world offers only two topologies to demodulate it (Costas Loop and the Squaring method) which are more complex and less reliable/practical than the one I liked to share in this forum
(I started to believe that presenting a new unfamiliar solution here was another silly decision I made in my life)

[SteveThackery]

 
In brief, since you also cannot verify what I say (it is not your field of interest), just tell me what you like me to tell you that lets you feel fine towards me, unless you have no choice but to insist, I am an ignorant blasphemer.

"An ignorant blasphemer"? I'm sorry, I have no idea what you mean. There is no blasphemy here.

I think you are aiming your efforts in the wrong direction. You seem to be trying to convince "the West" (via this forum) that you (and probably other people from your country) are just as smart as western academic experts by showing them a new modulation system that they haven't thought of. The thing is, nobody in the West thinks you're less smart than them. The vast majority of educational institutions are packed with academics from all over the world. When I was lecturing at university, I was the only English person in my office. The others were Italian, Japanese, Pakistani and Chinese. Only our qualifications and experience mattered.  Oh, and a good command of English.

Basically, the West is mostly about about making profits, and if someone can help make a company more profitable then issues around their country of origin are irrelevant. Here in the UK we have loads of Chinese people in academia, IT, telecommunications, and other high tech industries, despite China not being in the West and China being a dictatorship with appalling human rights. If you are smart enough you get the job.

You might be disappointed by the reactions of the people in this forum to your invention, but this is not because they are judging you and deciding you are less smart than them. It is only that your invention doesn't seem to bring any substantive benefit, bearing in mind that analogue radio has been obsolescent for forty years, now.

I think you should be directing your efforts in the opposite direction. I was horrified when you wrote this:

My crime, as you said, was my claim to know something not known in the West. They refused to verify my claim in any way and insisted that I was an ignorant dreamer. Yes, they used to believe (still do) that the West has gods, and I was seen, therefore, as a blasphemer towards those gods and deserve to be punished.

I could hardly believe my eyes when I read your story. Your treatment was appalling and outrageous. Plus it misrepresents the West. Yes, the West has a brilliant track record in science and technology, but definitely no "gods" (except money), and questioning and challenging the current scientific knowledge is not only allowed, it is encouraged. That is how science works.

So it seems to me that the people you need to convince are the people in your story, not the people in the West. As far as the West is concerned you are pushing at an open door.

[mawyatt]

Here is the West science rules, it rules over Politics, Religion, Race, Gender, and Money (mostly, explained later).

We taught (retired adjunct creating and teaching graduate level EE courses) and were taught science rules are to be broken, unless they can't, then they are called Laws!!

This is mostly true with exception to the semiconductor physics areas which have proven if enough market exist and enough $ are available certain perceived Physic Laws can be broken (Moores's Law).
 
We were taught long ago that semiconductor chip processing would stall at @ 10um, then 1um, and then later for sure nothing could ever be processed below 100nm except Direct Write E-Beam which wasn't a batch process so much too expensive for conventional chip processing.

We were also taught and experienced that it took almost a decade for the most advanced semiconductor technology to leave the Labs to end up in general purpose commercial products. That started to change when CMOS semiconductors took hold in the 80s, quickly bypassing any Government Labs attempts to "keep up", then started out pacing any financial means for the government to "keep up" with the "bleeding CMOS edge".

Soon folks started talking about the end of Moore's Law and backed up with physics limitations, however the semiconductor folks didn't listen and kept pushing the CMOS envelope soon passing what any sane physicist would even say is possible much less even doable at these nanometer levels, when the complexity of these chips boasting 30+ Billion nanometer transistors, costing $1B just to develop in a $30B fab!!

Oh yeah, and this impossible semiconductor IC technology ends up in our iPhones, iPads and Laptops anyone can get a few months after the formal announcements of the impossible chip developments, and for under $1000!!

These "Semiconductor Gods" are not only in the West, as TSMC and Samsung are leading the fabrication charge into the nanometer regions supporting these 30+ Billion chips designed at Nvidia, Apple, Intel, AMD and so on which have design centers scattered throughout the world.

Soon, very soon in fact ( ) we'll experience a chip with ~100 Billion transistors in 2nm CMOS!!

Well we all know that's totally impossible

Best 

[radiolistener]

No, it will be always a DSB-SC signal which the world offers only two topologies to demodulate it (Costas Loop and the Squaring method) which are more complex and less reliable/practical than the one I liked to share in this forum

Just to be clear, DSB-SC (also known simply as DSB) refers to AM modulation without a carrier.
However, your modulation also incorporates FM modulation for the carrier.

When you add FM modulation, it no longer makes sense to discuss suppressed carriers, because the output bandwidth of FM is much wider than the narrow and stable carrier of AM.

In other words, by introducing FM modulation in your modulation scheme, you negate the advantages of SSB, DSB, and AM modulation:

- SSB: Bandwidth and power efficiency.
- DSB: Power efficiency.
- AM: Frequency tolerance.

As you know FM modulation is a non-linear operation, so adding it you also add all disadvantages of FM modulation.

What, then, is the benefit of your approach? I fail to see any advantage. Could you please clarify this point?


You also mentioned that using FM modulation is not mandatory for your modulation scheme. But if you remove FM modulation from the carrier, your "new" modulation scheme essentially becomes classic DSB (DSB-SC). So, I am struggling to understand what exactly you are referring to.

Do I understand correctly that you are describing a specific approach to demodulate DSB signals? If so, can you please explain it in math? Or at least with some text description step-by-step on how to process the signal. Because it's hard to understand from the analog schematic.

Additionally, you mentioned issues with demodulating wideband DSB signals using classic methods. I am particularly interested in different kind of modulation from a digital processing perspective, and I don't see any problem with demodulating a DSB signal with a 100 kHz bandwidth (or more) using DSP techniques.

Could you please clarify what specific issue you mean regarding the demodulation of wideband DSB signals using classic approaches?

[KerimF]

No, it will be always a DSB-SC signal which the world offers only two topologies to demodulate it (Costas Loop and the Squaring method) which are more complex and less reliable/practical than the one I liked to share in this forum

Just to be clear, DSB-SC (also known simply as DSB) refers to AM modulation without a carrier.
However, your modulation also incorporates FM modulation for the carrier.

Oh my God, how many times I still need to repeat that I added deliberately the FM modulation JUST to prove the higher performance of My DSB-SC Demodulator over the World's Known Ones.
Sorry I see you as someone needs $100 to start a project. One of his generous friends offered him $200. The former refused the offer and said: your $200 don't help me because I need $100 only.

My DSB-SC demodulator can recover two signals ($200). One doesn't have to send two signals just because my demodulator, unlike the two old ones, can recover them both at the same time. He can use my demodulator to receive one signal only ($100) without the need to add FM modulation.

If you still cannot get the reason for which I added the FM modulation, my English is surely very bad, sorry.

Note:
A simple/conventional diode detector can demodulate an AM DSB signal with low distortion, only if the modulation index is not close to 1. It cannot demodulate a DSB-SC.
This is why our dear Costas had to present to the world his famous solution (that needs I-Q signals) which was given the name of Costas Loop.
Also, those who are professional in RF communications took advantage of the non-linear characteristic of active elements to generate a signal which has twice the frequency of the suppressed carrier one (after proper filtering at 2fc) and solved the problem (by dividing 2fc by 2).

[KerimF]

Do I understand correctly that you are describing a specific approach to demodulate DSB signals? If so, can you please explain it in math? Or at least with some text description step-by-step on how to process the signal. Because it's hard to understand from the analog schematic.

You request is reasonable.

Unfortunately, I use math just to solve (find out) the values of the elements which are used in a design that seems (logically) to work/function as expected if the right (optimum) values are found.

In our case here, I am afraid that having a basic knowledge on how a PLL circuit works is a prerequisite to understand the updated one here.
If you didn't have the chance and time to study a simple conventional PLL, I don't think I can help you, unless you ask me very specific questions (not general ones).

[radiolistener]

Unfortunately, I use math just to solve (find out) the values of the elements which are used in a design that seems (logically) to work/function as expected if the right (optimum) values are found.

In our case here, I am afraid that having a basic knowledge on how a PLL circuit works is a prerequisite to understand the updated one here.
If you didn't have the chance and time to study a simple conventional PLL, I don't think I can help you, unless you ask me very specific questions (not general ones).

I did not ask what a PLL is, nor did I suggest that I don’t understand how it works. My question was specific and technical: I asked for a description of your approach to demodulating a DSB signal, either mathematically or at least verbally.

Instead of addressing the question, you consistently shift to unrelated topics like politics or make assumptions about others understanding. Bringing up political issues in the context of this technical discussion is entirely inappropriate. Please focus on the math and provide a clear and concise explanation of your method without unnecessary digressions.

[mawyatt]

Could this new modulation scheme be related to BPSK?

Best

[KerimF]

Could this new modulation scheme be related to BPSK?

Best

I am not sure why it is so hard for me to explain, using English, that the title of this thread is simply to attract attention to a third topology (not known universally yet) to demodulate DSB-SC signals.

So, I added here a rather weird FM modulation, 455 Khz +/- 30 kHz (though I used it to scramble my short-range RF voice links. in the 80's) because no other known topology can recover the AM modulating signal from this FM-AM DSB-SC, unless the frequency of its suppressed carrier is made somehow invariant (fixed).

What I presented on post #9 is just about a new DSB-SC demodulator, nothing else. And if someone has LTspice he can set the parameter:
FM_pk = 0 instead of 0.5
By doing this, he removes the FM modulation completely while the recovered AM audio signal stays the same. For instance, in this case, the DSB-SC demodulators of Costas Loop and Squaring method (which are more complex to build than mine) can also recover it.

In brief, what we got here is a DSB-SC demodulator (actually, it works for any AM index, from m=0, no audio modulating signal, to infinity, no carrier). But it is simpler to build and more reliable/practical than the known ones. (It happens it can also act simultaneously as an FM demodulator in case the carrier frequency is modulated, besides its amplitude).

Kerim

[KerimF]

As you know AI bots are made by humans. So, if a programmer has no idea about something, his AI bot cannot know it too.

I guess for example, this is one of the questions that an AI bot cannot answer properly:

BW_am is the bandwidth of an RF channel when the amplitude of its carrier is modulated.

BW_fm is the bandwidth of the same RF channel but when the frequency of its carrier is modulated.

The question is:
What is the bandwidth, BW_am_fm (in function of BW_am and BW_fm), of this channel when both the amplitude and frequency of its carrier are modulated at the same time?

I wish to know how an AI bot will answer this question. Unfortunately, unlike most readers here, I can’t access one.

But, what about who have a Natural Intelligence? Hmmm... now I am doomed

[KerimF]

Since this thread is almost locked, speaking practically, here is the answer of post #73:

BW_am_fm = BW_am + BW_fm

I guess proving it is easy to most of you.

See you on another thread.

Cheers
Kerim