Reducing peak-to-average variance of a composite transmitted signal via out-of-band artifact signaling
First Claim
1. A transmitter for processing signals in a multiple mobile subscriber unit wireless communication system comprising:
- wideband digital combiner means, tier combining a plurality, n, of channel signals which are to be transmitted to a plurality of the mobile subscriber units, to produce a wideband composite digital signal, x(t), consisting of the n channel signals spaced apart in frequency, the wideband composite digital signal x(t) having an envelope that varies over time and a predetermined bandwidth;
artifact signal generating means, connected to receive the wideband composite digital signal, for generating an out-of-band artifact digital signal, a(t), which offsets the amplitude variations of the wideband composite digital signal, the artifact digital signal having frequency components that fall in a bandwidth outside of the predetermined bandwidth of the wideband composite digital signal;
summing means, connected to add the wideband composite digital signal x(t) and out-of-band artifact digital signal a(t), to produce a constant envelope digital signal, h(t);
digital-to-analog (D/A) conversion means, connected to receive the constant envelope digital signal, h(t), and to provide a constant envelope analog signal;
upconverter meters, connected to the D/A converter, for upconverting the constant envelope analog signal to a radio frequency (RF) to produce a constant envelope RF signal;
a high power amplifier, connected to receive the constant envelope RF signal, and to provide a power amplified RF signal;
RF filtering means, connected to receive the power amplified RF signal, for filtering components of the power amplified RF signal corresponding to the out-of-band artifact signal, to provide a wideband composite transmit signal; and
an antenna, for receiving the wideband composite transmit signal from the filtering means, and for providing a wide band wireless composite signal to the plurality of mobile subscriber units.
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Accused Products
Abstract
A technique which enables the use of a low cost non-linear power amplifier to generate a wideband composite signal, such as in cellular mobile telephones (CMTs), personal communication systems (PCSs), and other multi-channel wireless system. A constant envelope signal is generated from a wideband composite signal comprised of a combination of many narrowband modulated signals. The technique involves adding one or more out-of-band artifact signals that accurately offset the amplitude variations of the wideband composite signal. The constant envelope signal is then fed to a high power amplifier, and, prior to radio transmission the amplified signal is filtered to remove the out-of-band artifact signals. As a result, only the desired composite signal having any required envelope variations is provided to the antenna, while at the same time, only a constant envelope signal is fed through the power amplifier.
135 Citations
7 Claims
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1. A transmitter for processing signals in a multiple mobile subscriber unit wireless communication system comprising:
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wideband digital combiner means, tier combining a plurality, n, of channel signals which are to be transmitted to a plurality of the mobile subscriber units, to produce a wideband composite digital signal, x(t), consisting of the n channel signals spaced apart in frequency, the wideband composite digital signal x(t) having an envelope that varies over time and a predetermined bandwidth; artifact signal generating means, connected to receive the wideband composite digital signal, for generating an out-of-band artifact digital signal, a(t), which offsets the amplitude variations of the wideband composite digital signal, the artifact digital signal having frequency components that fall in a bandwidth outside of the predetermined bandwidth of the wideband composite digital signal; summing means, connected to add the wideband composite digital signal x(t) and out-of-band artifact digital signal a(t), to produce a constant envelope digital signal, h(t); digital-to-analog (D/A) conversion means, connected to receive the constant envelope digital signal, h(t), and to provide a constant envelope analog signal; upconverter meters, connected to the D/A converter, for upconverting the constant envelope analog signal to a radio frequency (RF) to produce a constant envelope RF signal; a high power amplifier, connected to receive the constant envelope RF signal, and to provide a power amplified RF signal; RF filtering means, connected to receive the power amplified RF signal, for filtering components of the power amplified RF signal corresponding to the out-of-band artifact signal, to provide a wideband composite transmit signal; and an antenna, for receiving the wideband composite transmit signal from the filtering means, and for providing a wide band wireless composite signal to the plurality of mobile subscriber units. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification