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Method and apparatus for reducing off-channel interference produced by a linear transmitter
| Details |
Inventors: Cygan, Lawrence F.; Gailus, Paul H.; Turney, William J.; Baker, Michael H.;
Assignee: Motorola, Inc. (Schaumburg, IL)
Primary Examiner: Eisenzopf; Reinhard J.
Assistant Examiner: Nguyen; Lee
Attorney, Agent or Firm: Coffing; James A., Crilly; Daniel C.
A linear transmitter (100), which utilizes closed loop feedback to maintain its linearity, employs a method for reducing off-channel interference produced by the linear transmitter (100). A dynamically alterable parameter source (DAPS, 126) is provided to the linear transmitter (100). The DAPS (126) is then used to adjust at least one loop parameter of the closed loop feedback such that off-channel interference is reduced. |
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DETAILED DESCRIPTION What is claimed is: 1.
In a linear transmitter that includes an information signal source and a power amplifier having a varying load impedance, the linear transmitter utilizing a closed loop feedback path to maintain linearity, wherein the closed loop feedback path includes a loop phase adjusting circuit, a method for reducing off-channel interference comprising the steps of: A) providing a dynamically alterable parameter source; B) measuring the varying load impedance to produce a measured load impedance; C) inputting the measured load impedance to the dynamically alterable parameter source; D) producing, by the dynamically alterable parameter source, a loop phase adjustment value base on the measured load impedance; E) inputting the loop phase adjustment value to the loop phase adjusting circuit; and F) adjusting, by the loop phase adjusting circuit, a phase value for the closed loop feedback path based, at least in part, on the loop phase adjustment value.
2.
In a linear transmitter that includes an information signal source and a power amplifier having a varying load impedance, the linear transmitter utilizing a closed loop feedback path to maintain linearity, and the closed loop feedback path including a loop phase adjusting circuit, a method for reducing off-channel interference comprising the steps of: A) providing a dynamically alterable parameter source; B) providing a training signal within a training interval; C) at times falling substantially within the training interval, measuring the varying load impedance to produce a measured load impedance; D) inputting the measured load impedance to the dynamically alterable parameter source; at times falling substantially outside the training interval, E) using the dynamically alterable parameter source to produce a loop phase adjustment value based on the measured load impedance; F) inputting the loop phase adjustment value to the loop phase adjusting circuit; and G) adjusting, by the loop phase adjusting circuit, loop phase of the closed loop feedback path based on the loop phase adjustment value, thereby reducing off-channel interference produced during the training interval and at times falling substantially outside the training interval
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Audio Signal Processing 
