Modulators – Pulse or interrupted continuous wave modulator
Reexamination Certificate
2002-06-11
2003-09-23
Wells, Kenneth B. (Department: 2817)
Modulators
Pulse or interrupted continuous wave modulator
C332S115000
Reexamination Certificate
active
06624712
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to power modulators and in particular to a power modulator and method of operating a power modulator.
BACKGROUND OF THE INVENTION
Switched-mode modulators are often used for power supply modulation in radio transmitters as a means to improve the efficiency of RF power amplifiers. In either the envelope tracking (ET) technique, or envelope elimination and restoration method (EER), an efficient switching power supply is used to vary the supply voltage of a power amplifier according to an envelope function. The power amplifier is operated at or near saturation, where its efficiency is optimal.
It is well known that the frequency of the switching power modulator must generally be at least 10 times the modulation bandwidth of the amplified signal so to accurately comply with the envelope function and ease filtering requirements. Where large signal bandwidths are used, the required switching rate may exceed that practically attainable, or may be high enough that significant switching losses are incurred.
In order to address these issues, prior art solutions have attempted to control the supply voltage using a combination of a switch-mode converter stage for gross power level control and a subsequent linear regulator stage for precise power envelope control. Such a prior-art solution is shown in FIG.
1
and described in detail in the International Application WO 00/48306 HIGH-EFFICIENCY AMPLIFIER AND BURST CONTROL. As shown in
FIG. 1
, amplifier
101
is preceded by linear regulator
103
and switching modulator (or switch-mode converter)
105
. Although the above solution does allow for more efficient operation of amplifier
101
, a problem exists in that oftentimes clipping occurs in amplifier
101
. More particularly, in order to avoid saturation of linear regulator
103
and clipping of the envelope function, V
PA
must be held less than V
SUP
. Because the prior-art solution discussed above fails to assure that V
SUP
>V
PA
clipping often occurs. Therefore a need exists for a power modulator and method of operating a power modulator that prevents saturation of linear regulator
103
and clipping amplifier
101
.
REFERENCES:
patent: 6011815 (2000-01-01), Eriksson et al.
patent: 6366177 (2002-04-01), McCune et al.
patent: 6377784 (2002-04-01), Mc Cune
patent: WO 00/48306 (2000-08-01), None
patent: WO 00/48307 (2000-08-01), None
patent: WO 01/10013 (2001-02-01), None
Cygan Lawrence
Khan Andrew
Haas Kenneth A.
Motorola Inc.
Wells Kenneth B.
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