Amplitude Modulation Technique Page
How many methods of generating an amplitude modulated radio signal are you
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- High Level "Heising" constant current
Anode Modulation (Plate Modulation)
The Heising method was the first practical method of generating an
Amplitude Modulated radio signal. This method used the application of an audio signal superimposed on the anode
supply voltage of a class-C RF amplifier.
- Controlled Carrier
- Chireix "Outphasing" Modulation (RCA
Outphasing modulation was invented by Henry Chireix in 1935. This method
obtains an AM signal by the use of counter-phase modulation and vector addition of two radio frequency signals.
It was marketed by RCA under the trade name "Ampliphase."
- Class-B High Level Anode Modulation
- Doherty High-Efficiency Linear Amplifier
- Pulse-Width High-Level Anode Modulation
- High-Efficiency Screen/Impedance Modulation (Terman
- Asea Brown Boveri (ABB) Pulse-Step Modulation
One of the first, workable, solid state modulation techniques for very
high power use for Low, Medium and Shortwave transmitters running from 100 kw to 600 kw. In this type, the modulation
steps are broken up into 24 modules. In this method, low voltage power supplies are stacked in series and switched
into and out of operation to generate an anode modulation voltage. To further refine the linearity, each power
supply step is pulse-width modulated, creating a smooth transition from one step to the next. Numbering the modules
from 1-28, the low numbered modules handle the lower levels of modulation. This would mean that the lower the level
of modulation the unit handles, the more it is used. However, the PSM controller attempts to distribute the usage
among the vaious levels by rotating the units through different levels of modulation levels. This gives longer
overall life of each individual unit.
Graphic illustration of how output envelope wave (blue) is produced by pulse-step input (yellow).
- Continental Electronics Corporation (CEC) Pulse-Step
- Nautel Corporation - AMPFET
- Polyphase Pulse-Width Modulation
- Harris DX Series Pulse-Code Modulation (PCM)
- Kahn Power-Side System