Modulators – Pulse or interrupted continuous wave modulator – Pulse width modulator
Reexamination Certificate
2001-11-27
2003-04-15
Pascal, Robert (Department: 2817)
Modulators
Pulse or interrupted continuous wave modulator
Pulse width modulator
C370S212000, C375S238000
Reexamination Certificate
active
06549085
ABSTRACT:
FIELD OF THE INVENTION
In general, the present invention relates to the field of communication systems. More specifically, the present invention relates to a generation of modulated radio frequency (“RF”) signals.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,838,210 describes a method for producing a modulated RF signal via pulse modulation. Specifically, U.S. Pat. No. 5,838,210 describes modulating the width of the pulse and the phase of the pulse. With conventional pulse width modulation (PWM), only the width of the pulse is modulated by a duty ratio signal. It is known in the art that the best method to produce a PWM signal is to implement natural-sampling whereby a duty ratio signal is compared to a varying periodic ramp to produce the PWM as shown in
FIG. 1
with only the width of the pulse being modulated. However, in the RF-PWM case, both the duty ratio and phase of the pulse must be varied. Consequently, the varying ramp in
FIG. 1
must also vary with the desired phase.
Prior art natural sampling methods allow for only the width to vary and do not allow for the fixed ramp to vary. They assume that the magnitude of the slope of the fixed ramp is a constant. In the case of RF-PWM, the slope of a ramp varies with the derivative of the phase. Therefore, prior art natural sampling methods target baseband PWM as opposed to RF-PWM, and therefore do not provide the requisite natural sampling.
Thus, there is a need for a new and unique natural sampling method for RF-PWM.
SUMMARY OF THE INVENTION
One form of the present invention is a method for generating a pulse width modulated signal. First, a complex baseband signal is received. Second, a first pulse edge vector and a second pulse edge vector are computed as a function of the complex baseband signal. Third, a first set of natural sampling points is determined as a function of the first pulse edge vector and a second set of natural sampling points is determined as a function of the second pulse edge vector. Finally, the pulse width modulated signal having a plurality of pulse edges corresponding to the first set of natural sample points and the second set of natural sample points is generated.
A second form of the present invention is a method for facilitating a generation of a pulse width modulated signal. First, a complex baseband signal is received. Second, a first pulse edge vector is computed as a function of the complex baseband signal. Third, a second pulse edge vector is computed as a function of the first pulse vector is response to a detection of a jump k&pgr; within the first pulse edge vector.
The foregoing forms, and other forms, features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiment, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.
REFERENCES:
patent: 5838210 (1998-11-01), Midya et al.
patent: 6414613 (2002-07-01), Midya et al.
patent: 6473457 (2002-10-01), Pascual et al.
“Integral Noise Shaping for Quantization of Pulse Width Modulation”: Pallab Midya & Matt Miller; Motorola Labs, Schaumburg, Illinois and Mark Sandler, Kings College, London. An audio engineering society preprint, presented at the 109thConvention Sep. 22-25, 2000 in Los Angeles, California, USA.
“Prediction Correction Algorith for Natural Pulse Width Modulation”: Pallab Midya, Bill Roeckner, Pat Rakers, & Poojan Wagh; Motorola Labs, Schaumburg, Illinois. An audio engineering society preprint, presented at the 109thConvention Sep. 22-25, 2000 in Los Angeles, California, USA.
Midya Pallab
Rakers Patrick
Wagh Poojan A.
Glenn Kimberly E
Haas Kenneth A.
Motorola Inc.
Pascal Robert
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