12-10-2010, 11:00 AM
THE DIGITAL AMPLITUDE MODULATOR
Timothy P. Hulick, Ph.D., W9QQ
886 Brandon Lane
Schwenksville, PA 19473
Abstract.
This paper is the first of two presenting the Digital Amplitude Modulator and the Digital Linear Amplifier. One leads to the other with the Digital Amplitude Modulator the precursor and the first theorized. Linear amplitude modulation in very high power full carrier systems still requires rather large solid state or vacuum tube devices in Medium Wave (MW) and Short Wave (SW), telephone and VHF and UHF television transmission broadcast systems. The analog format for these systems for MW and SW is simple full carrier 100% AM with no phase modulation. For vestigial sideband television, and any of the X-QAMs, X-VSBs or any other digital format requiring both AM and PM to describe the envelope vector of the modulated signal, simultaneous AM and PM are required. This paper presents a modern approach to digitally synthesized analog amplitude modulation boasting very high power efficiency, and linearity which is only a function of quantization error. This is the first of two papers on Digital Amplitude Modulation and Digital Linear Amplification where all non-orthogonal multiple carrier formats, digital or analog, are transmitted by RF or microwave by means of analog wave-form modulation. Saturated class C amplifiers are used as binarily related carrier power sources each connected to one input of a set of 3 dB power combiners arranged such that the output of the (n-1)th combiner feeds the other input of the nth combiner. Linear amplitude modulation takes place in the array of power combiners as amplifiers feeding the array are gated on or off according to the bit content of the digitized baseband modulation signal as sampled by means of an analog to digital converter. Modulation is absolutely linear with no flat topping, differential gain or phase or incidental carrier phase modulation. The only source of distortion is the quantization error. The spurious free dynamic range is dictated by the A/D converter used.
for more information about the :-
http://www.amradprojects/lf/DIGITALMODULATOR.PDF
Timothy P. Hulick, Ph.D., W9QQ
886 Brandon Lane
Schwenksville, PA 19473
Abstract.
This paper is the first of two presenting the Digital Amplitude Modulator and the Digital Linear Amplifier. One leads to the other with the Digital Amplitude Modulator the precursor and the first theorized. Linear amplitude modulation in very high power full carrier systems still requires rather large solid state or vacuum tube devices in Medium Wave (MW) and Short Wave (SW), telephone and VHF and UHF television transmission broadcast systems. The analog format for these systems for MW and SW is simple full carrier 100% AM with no phase modulation. For vestigial sideband television, and any of the X-QAMs, X-VSBs or any other digital format requiring both AM and PM to describe the envelope vector of the modulated signal, simultaneous AM and PM are required. This paper presents a modern approach to digitally synthesized analog amplitude modulation boasting very high power efficiency, and linearity which is only a function of quantization error. This is the first of two papers on Digital Amplitude Modulation and Digital Linear Amplification where all non-orthogonal multiple carrier formats, digital or analog, are transmitted by RF or microwave by means of analog wave-form modulation. Saturated class C amplifiers are used as binarily related carrier power sources each connected to one input of a set of 3 dB power combiners arranged such that the output of the (n-1)th combiner feeds the other input of the nth combiner. Linear amplitude modulation takes place in the array of power combiners as amplifiers feeding the array are gated on or off according to the bit content of the digitized baseband modulation signal as sampled by means of an analog to digital converter. Modulation is absolutely linear with no flat topping, differential gain or phase or incidental carrier phase modulation. The only source of distortion is the quantization error. The spurious free dynamic range is dictated by the A/D converter used.
for more information about the :-
http://www.amradprojects/lf/DIGITALMODULATOR.PDF