15-02-2018, 08:41 AM
See: http://www.thevalvepage.com/radtech/synchro/synchro.htm for what is said to be a transcription of the Tucker article in the Journal of the British Institution of Radio Engineers in April 1954.
Wireless World 1948 August carried an article by “Cathode Ray” which drew from Tucker’s article in Electronic Engineering 1947 March.
However, the history of synchronous AM demodulation is much broader topic than covered by Tucker’s Homodyne and Synchrodyne articles. It was long a goal for both radio and TV vision demodulation, but realized in terms of mass-produced consumer-level products only in the IC age. I unearthed some of the history, albeit in a disjointed way, in connection with the old UKVRR thread: https://www.vintage-radio.net/forum/show...post348392, and have since found a bit more.
Be that as it may, I should answer the original question by saying some form of well-executed synchronous demodulation, whether PLL fully synchronous or quasi-synchronous, the choice between the two being circumstantial. Even the best rectifying demodulator, perhaps the precision rectifier, will distort with sideband asymmetry and if fading causes the carrier to drop enough to cause the modulation to go beyond 100%.
The circumstantiality of the choice between PLL fully synchronous and quasi-synchronous is well illustrated by the Motorola C-QUAM AM stereo decoding ICs. Envelope demodulation was done by a very low-distortion quasi-synchronous demodulator, this ensuring that the reference channel carried the same phase modulation (PM) as the signal, and so the PM did not distort the output. On the other hand, the I and Q signals were recovered by PLL fully synchronous demodulators.
Cheers,
Steve
Wireless World 1948 August carried an article by “Cathode Ray” which drew from Tucker’s article in Electronic Engineering 1947 March.
However, the history of synchronous AM demodulation is much broader topic than covered by Tucker’s Homodyne and Synchrodyne articles. It was long a goal for both radio and TV vision demodulation, but realized in terms of mass-produced consumer-level products only in the IC age. I unearthed some of the history, albeit in a disjointed way, in connection with the old UKVRR thread: https://www.vintage-radio.net/forum/show...post348392, and have since found a bit more.
Be that as it may, I should answer the original question by saying some form of well-executed synchronous demodulation, whether PLL fully synchronous or quasi-synchronous, the choice between the two being circumstantial. Even the best rectifying demodulator, perhaps the precision rectifier, will distort with sideband asymmetry and if fading causes the carrier to drop enough to cause the modulation to go beyond 100%.
The circumstantiality of the choice between PLL fully synchronous and quasi-synchronous is well illustrated by the Motorola C-QUAM AM stereo decoding ICs. Envelope demodulation was done by a very low-distortion quasi-synchronous demodulator, this ensuring that the reference channel carried the same phase modulation (PM) as the signal, and so the PM did not distort the output. On the other hand, the I and Q signals were recovered by PLL fully synchronous demodulators.
Cheers,
Steve
