Polar transmitter with zero crossing avoidance
AssigneeSamsung Electronics Co., Ltd.
InventorJacob Christopher Sharpe
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Abstract
A polar transmitter and method thereof generate a filtered IQ waveform in IQ space representing an input bit stream. The filtered IQ waveform is modified to avoid a zero crossing region by intermittently adding thereto a zero crossing avoidance signal with a frequency spectrum comprising at least first and second tones defining first and second peaks on opposite sides of a center-frequency valley. A polar signal comprising a polar amplitude and phase is generated based on the modified IQ waveform. An RF carrier is modulated using the polar signal.
Claims20
A method for modulating a bit stream, comprising:
- using a processor, generating, based on a stream of in-phase (I) and quadrature-phase (Q) (“IQ”) symbol pairs, each representing a portion of the bit stream, a filtered IQ waveform representable in IQ space;
- modifying, using the processor, the filtered IQ waveform to avoid a zero crossing region in the IQ space by intermittently adding thereto a zero crossing avoidance signal with a frequency spectrum comprising at least first and second tones defining first and second peaks on opposite sides of a center frequency valley;
- generating a polar signal comprising a polar amplitude and phase, based on the modified filtered IQ waveform;
- and
- modulating a radio frequency (RF) carrier using the polar signal.
A polar transmitter comprising:
- a symbol mapper circuit configured to receive an input bit stream and generate a stream of in-phase (I) and quadrature-phase (Q) (“IQ”) symbol pairs each representing a portion of the bit stream, to obtain an IQ waveform;
- a pulse shaper circuit configured to low pass filter the IQ waveform to obtain a filtered IQ waveform representable in IQ space;
- a zero crossing avoidance signal generator circuit configured to generate a zero crossing avoidance signal that is applied during a window encompassing a π phase shift transition, and having a characteristic defined by a primary peak at a zero crossing time coincident with a zero crossing of the filtered IQ waveform, a first valley at a time between a start time of the window and the zero crossing time, and a second valley at a time between the zero crossing time and an end time of the window;
- a delay circuit configured to delay the filtered IQ waveform to provide a delayed IQ waveform;
- an adder circuit configured to add the zero crossing avoidance signal with the delayed IQ waveform to obtain a modified IQ signal;
- an IQ to polar conversion circuit configured to convert the modified IQ signal into a polar signal;
- and
- a polar modulator circuit configured to modulate a radio frequency (RF) carrier using the polar signal.
A non-transitory computer-readable recording medium storing instructions that, when executed by at least one processor, implement a method for modulating a bit stream, the method comprising:
- generating, based on a stream of in-phase (I) and quadrature-phase (Q) (“IQ”) symbol pairs each representing a portion of the bit stream, a filtered IQ waveform in I-Q space;
- modifying, using the at least one processor, the filtered IQ waveform to avoid a zero crossing region in the I-Q space by intermittently adding thereto a zero crossing avoidance signal with a frequency spectrum comprising at least first and second tones defining first and second peaks on opposite sides of a center-frequency valley;
- generating a digital polar signal comprising a digital polar amplitude and phase, based on the modified filtered IQ waveform;
- and
- outputting the digital polar signal to a digital to analog converter for subsequent modulation of a radio frequency (RF) carrier using the polar signal.
Dependencies are inferred from the claim text.