i need help. I am a graduating student. Electronics and communications is my course. So if you have any ideas or thesis proposals, you may suggest it. Thanks for your help 
My thesis in year 1979 was a simple demodulator for Double Sideband Suppressed Carrier (DSB-SC) signal.
At that time, I did it for the IF AM frequency 455 KHz by using CD4046 (PLL IC) and LM339 (quad comparator IC) to recover the phase and frequency of the suppressed carrier. But after I built the project I didn’t find the time to submit its papers since I was in a hurry to start my private business (for electronic circuit design). But later and for a few years, I took advantage of this demodulator in my private audio RF links by using DSB-SC.
Now I am 64, and after searching on the internet it seems to me (perhaps I am wrong) that my simple DSB-SC demodulator is not done by anyone else yet.
For example, if you can ask your supervisor (in communications) about it (I mean... by using a conventional PLL as CD4046, the suppressed carrier of a DSB-SC signal could be recovered, phase and frequency), you will likely hear him say "It can't be done"
If you will find out that this project could interest your professors, it will be my pleasure to help you understand and build it.
I think after more than 30 years, the importance of this demodulator is rather academic only now. The DSB-SC system is not widely used since its ‘known’ demodulators are complex (if linear) or costly (if digital). It is sad that my low-cost reliable solution was not found by some others hence known since long.
):smile:
Sorry for my late reply because I was very sick and I went to hospital.
Your question is good since a project should be useful in a way or another mainly in industry.
The proposed DSC-SC demodulator (low-cost, simple and reliable) using the conventional analog PLL seems being a novel idea even now. You may like to verify that its analysis cannot be found in any reference at any university around the world. Although I found it in 1979, it was universally accepted that despite of the many advantages of the DSB-SC system, it couldn't be used at a large scale (as AM, FM and SSB) because its analog demodulators (see Costas Loop, for example) cannot be implemented easily as it is case for other systems. Naturally, Costas Loop was implemented digitally later in special ICs and though this digital solution is reliable, it is also complex and costly.
Obviously, the proposed DSB-SC demodulator, based on the analog PLL, can also be produced as an IC for frequencies that the complex digital demodulators (of DSB-SC) cannot be justified for. But, if no one knows about this simple analog demodulator, how it can be produced
For example, here was my first DSB-SC system I built (as a test, in 1980) so that conventional AM receivers (unlike mine) hear my audio signal as noise.
Transmitter (DSB-SC):
The frequency (Fc) of the suppressed carrier is 1 MHz.
Fc is varied at a rate of 6 Hz (sinusoidal) to cover a bandwidth of ±50 KHz (that is Fc varies in the range 1 MHz ±50 KHz).
The bandwidth of the audio signal is about 5 KHz.
Receiver:
Intermediate Frequency (IF) is 455 KHz.
PLL demodulator is based on 4066 and LM339. It is in lock with the varying Fc (frequency and phase).
Synchronous multiplier recovers the audio signal.
Now, after I gave you a specific situation (problem), you can verify that you won't find a professor in communications who can solve it even in theory. This is why no one produced yet an IC for this analog demodulator as it was done for the digital one. It is up to you to decide if you will be the first one to introduce it to the world or not
Kerim
