LINEAR AMPLIFICATION WITH NONLINEAR DEVICES

• US 3,777,275 A
• Filed: 01/31/1972
• Issued: 12/04/1973
• Est. Priority Date: 01/31/1972
• Status: Expired due to Term

• Current Assignee: Donald Clyde Cox
• Original Assignee: Donald Clyde Cox
• Inventors: Cox, Donald Clyde
• Primary Examiner(s): Kaufman, Nathan
• Application Number:
  US05/222,243
• Time in Patent Office: 673 Days
• Field of Search: 330/14,10,117
• US Class Current: 330/10
• CPC Class Codes: H03F 1/0294 using vector summing of two or more constant amplitude phase-modulated signals
• CPC Class Codes: H03F 1/3241 using predistortion circuits H03F1/3211, H03F1/3217 take precedence

Abstract

Available nonlinear amplifying devices are used to produce bandpass linear amplification of a signal having amplitude variations. The input signal is transformed into two constant amplitude phase modulated components which together contain in their phase fluctuations the total information content of the input. The components are amplified separately by devices which preserve phase, and the recombination of the amplified components reproduces a linearly amplified replica of the original input. The technique is primarily useful at high frequencies and can be modified to provide frequency translation.

Claims

1. A circuit for linearly amplifying a bandpass input signal having amplitude variations comprising, separating means for forming from its input a pair of constant amplitude phase modulated components, the separating means being adapted to receive the bandpass input signal as its input, said separating means including first and second converting means for converting the amplitude variations of the bandpass input signal to phase modulation of the pair of components, the first converting means producing one of said pair of components, the one component being phase modulated in a first sense, the phase modulation of the one component being proportional to the arc sine of the amplitude variations of the bandpass input signal, the second converting means producing a second of the pair of components, the second component being phase modulated in a second sense opposite to the first sense, the phase modulation of the second component being proportional to the arc sine of the amplitude variations of the bandpass input signal, device means for independently amplifying each of the constant amplitude components by the same gain factor to produce processed components, and recombining means for linearly combining the processed components to reconstruct a restructured replica of the bandpass input signal, the phase modulation of the two components being converted to amplitude variations in the replica.

2. A circuit as claimed in claim 1 wherein sAid device means is a pair of amplifying devices having identical nonlinear gain characteristics.

3. A circuit as claimed in claim 1 wherein said circuit further includes means for independently translating the frequency of each of the constant amplitude components by an identical frequency shift.

4. A circuit as claimed in claim 1 wherein the one component produced by the first converting means is C sin ( omega t + (t) + phi (t)), and the second component produced by the second converting means is C sin ( omega t + theta (t) - phi (t)) where C is a constant, t is time, omega is the carrier frequency, theta (t) is the time-varying phase of the band-pass input signal, and phi (t) is the time-varying phase modulation defined by E(t) Em sin phi (t) E(t) being the time-varying amplitude of the bandpass input signal and Em being the maximum amplitude of the bandpass input signal.

5. A circuit for linearly processing a band-pass signal having amplitude variations comprising:

detecting means for providing a signal representative of the amplitude envelope of its input, limiting means for producing an amplitude limited version of its input, means for applying the bandpass signal as inputs for both the detecting means and the limiting means, a series circuit of a first phase modulator, a mixer, a lowpass filter, and a high gain amplifier connected in that order, the output of the limiting means being connected to the mixer where it is combined with the output of the first phase modulator, the output of the detecting means being connected to the input of the high gain amplifier, means for phase shifting the output of the limiting means, the phase shifted output of the limiting means being applied to the first phase modulator, the output of the high gain amplifier being applied to the first phase modulator where it modulates the phase shifted output of the limiting means to produce a first constant amplitude phase modulated component, whose phase modulation is proportional to the arc sine of the amplitude variations of the bandpass signal and varies in a first sense relative to the amplitude variations of the bandpass signal, a second phase modulator, the phase shifted output of the limiting means being applied to the second phase modulator, means for applying the output of the high gain amplifier to the second phase modulator where it modulates the phase shifted output of the limiting means to produce a second constant amplitude phase modulated component, whose phase modulation is proportional to the arc sine of the amplitude variations of the bandpass signal and varies in a second sense, opposite to the first sense, relative to the amplitude variations of the bandpass signal, device means for operating independently upon each of the constant amplitude phase modulated components to produce processed components, and recombining means for linearly combining the processed components to reproduce a restructured replica of the bandpass signal, the phase modulation of the two components being converted to amplitude variations in the replica.