Transmitter and associated method for reducing the adjacent channel power during wireless communications
First Claim
1. A transmitter for removing at least some out of band signals from a transmitted output signal having a predetermined bandwidth, comprising:
- a phase modulator for receiving a signal and modifying the phase of the signal;
a power amplifier for receiving the phase modified signal from the phase modulator and amplifying the phase modified signal;
a amplitude modulator for receiving the amplified phase modified signal and modifying the amplitude of the amplified phase modified signal, wherein the phase modification provided by said phase modulator and the amplitude modification provided by said amplitude modulator cooperate to filter out of band signals from the transmitted output signal.
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Accused Products
Abstract
A transmitter for improving the spectral characteristics of a transmitted output signal includes a phase modulator for receiving a signal and modifying the phase of the signal, a power amplifier for receiving the phase modified signal from the first operation and amplifying the phase modified signal, and an amplitude modulator for receiving the amplified phase modified signal and modifying the amplitude of the amplified phase modified signal. Although the phase and amplitude modulation are performed separately in order to minimize the amplitude distortion without complicating the design of the phase modulator, the combined effect of the phase and amplitude modulation is to filter the out of band spectral emissions of the transmitted output signal. Additionally, the transmitter can store the phase shift and amplitude modulation information in a table for a variety of different input data sequences such that the phase shift and amplitude modulation information need merely be looked up in the table as opposed to being calculated in response to each digital signal input.
34 Citations
15 Claims
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1. A transmitter for removing at least some out of band signals from a transmitted output signal having a predetermined bandwidth, comprising:
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a phase modulator for receiving a signal and modifying the phase of the signal;
a power amplifier for receiving the phase modified signal from the phase modulator and amplifying the phase modified signal;
a amplitude modulator for receiving the amplified phase modified signal and modifying the amplitude of the amplified phase modified signal, wherein the phase modification provided by said phase modulator and the amplitude modification provided by said amplitude modulator cooperate to filter out of band signals from the transmitted output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for removing at least some out of band signals from a transmitted output signal having a predetermined bandwidth, the method comprising:
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modifying the phase of a signal;
amplifying the phase modified signal; and
modifying the amplitude of the amplified phase modified signal, wherein the phase modification and said amplitude modification cooperate to filter out of band spectral signals from the transmitted output signal. - View Dependent Claims (9, 10)
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11. A method for removing at least some out of band signals from a signal output by a transmitter including at least one non-linear element, comprising:
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for each of a plurality of different input signals, predetermining an amplitude modification and a phase modification of the respective input signal which would remove at least some out of band spectral signals from the transmitted output signal;
storing the amplitude and phase modifications for each of the plurality of different input signals;
independently applying the amplitude modification and the phase modification to the input signal, wherein applying the amplitude modification comprises applying the amplitude modification after all non-linear elements of the transmitter. - View Dependent Claims (12, 13)
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14. A transmitter for improving the spectral characteristics of a transmitted output signal, comprising:
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a modulator, the modulator receiving a digital signal sample and subjecting the digital signal sample to a first filter for determining phase shift and amplitude variation information produced by the filter;
a table for storing the phase shift and amplitude variation information, wherein phase shift and amplitude variation information is received from the table in response to a digital signal input, such that the phase shift and amplitude variation information can be independently applied to the digital signal input to produce a modulated signal, such that the filter can be eliminated. - View Dependent Claims (15)
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Specification