Pulse or digital communications – Transmitters – Angle modulation
Reexamination Certificate
1998-09-25
2001-07-17
Chin, Stephen (Department: 2634)
Pulse or digital communications
Transmitters
Angle modulation
C375S322000, C370S902000
Reexamination Certificate
active
06263027
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates, generally, to digital modulator devices and communication systems and processes which use digital modulation, and, in particular embodiments, to such systems, processes and devices which minimize modulator size, and power requirements by minimizing the required number of multipliers.
DESCRIPTION OF THE RELATED ART
Electronic communication has become a part of many aspects of personal, business, military and other activities and tasks. As the popularity of various electronic communication devices increases, for example, personal communication devices such as cellular telephones, personal pagers, cordless telephones or the like, the demand for smaller, lighter, more power-efficient electronics increases.
Modulation of carrier signals with baseband signals is a function involved in many modern electronic communication systems. However, the hardware implementation of various conventional baseband modulators, at least for some popular system applications, requires significant die space and requires a significant amount of power.
Modulators are used in many modern electronic communication systems including, for example, devices that transmit signals over long distances, devices that transmit or store data represented as digital signals, and telecommunication devices. Transmitting devices typically modulate data signals to match their frequency characteristics to those of the transmission medium, for example, to minimize signal distortion, to use the available bandwidth efficiently, and to ensure that the signals have certain desirable properties. The process of modulation often involves modifying a high frequency signal, known as the carrier signal in sympathy with a data signal, called the modulating (or baseband) signal. For convenience, persons skilled in the art typically categorize modulation into one of two categories.
A first category, data modulation, involves encoding a stream of data (often referred to as a baseband signal) into a carrier signal. A carrier signal modified in accordance with a modulation scheme is referred to as a modulated carrier. Commonly used modulation schemes for the transmission of analog data over a bandpass channel (for example, a microwave, cellular telephone, or other radio frequency link) include, for example, Amplitude Modulation (AM), Frequency Modulation (FM), Single Sideband Modulation (SSB), etc. Commonly used modulation schemes for the transmission of digital data over a bandpass channel include, for example, Amplitude Shift Keying (ASK), Phase Shift Keying (PSK), Frequency Shift Keying (FSK), etc.
A second modulation category, up-conversion, involves shifting a signal from one frequency range to another (usually higher) frequency range. For example, in commercial broadcast applications, such as standard AM, FM or television broadcasts, a radio program (the baseband signal) is used to modulate a radio frequency carrier signal. The modulated radio frequency carrier signal is amplified and provided to a transmitting antenna for radiation as electromagnetic waves (radio waves). On the receiver end, a receiving antenna receives the electromagnetic waves, and demodulates and amplifies the signal to recover the original radio program.
In many popular applications, communication systems include portable or remote transmitting or receiving units that, in some instances, operate on limited power supplies, such as battery packs or the like, and/or are designed to be portable and stowable. For example, cellular telephone systems include cellular telephone transmitter/receiver units which, typically, operate on limited battery power and which are often designed to be carried in a compact space, such as a pocket, briefcase, purse or the like. Similarly, cordless telephone systems include cordless transmitter/receiver units which operate on a rechargeable battery and which are designed to be relatively light-weight and portable. It is typically desirable to minimize size, weight and power consumption requirements of such portable or remote units and components thereof. Of course, other communication systems would also benefit by minimizing size, weight and power consumption requirements.
However, modulation electronics required by some communication systems are often configured with components that have relatively high power requirements and take up considerable die space. For example, as described below with respect to
FIG. 3
herein, modulation electronics used in, for example, transmitting devices of some conventional communications systems employ two multipliers and an adder which can contribute significantly to the overall power requirement, size and weight of the modulator circuit of the device. Thus, there is a need in the industry to minimize size (die space requirements), weight and power consumption requirements of modulation electronics in various communication systems.
SUMMARY OF THE DISCLOSURE
According, preferred embodiments of the present invention are directed to modulation electronics modulation circuits and communication devices and systems employing the same, as well as modulation and communication processes, which address the above-noted industry need, by employing a modulator configuration which employs components that require minimal die space, and power. Example modulator configurations described herein avoid the need for two multipliers and an adder.
A communication system according to an embodiment of the invention includes at least one transmitter and at least one receiver for communication on a communication channel. The transmitter includes a data signal source for providing first and second (for example, I and Q channel signals) digital baseband signals, an encoder for digitally encoding the first and second baseband signals, a wave shaper for smoothing the first and second baseband signals and a modulator coupled to the wave shaper, to provide a modulated output signal. For analog transmission embodiments, the transmitter further includes a digital-to-analog converter coupled to the multiplier output, for providing an analog modulated output signal. In wireless system embodiments, a power amplifier is coupled for amplifying the analog modulated signal and an antenna is coupled for transmitting the amplified analog modulated signal to the receiver.
A modulator according to a preferred embodiment, includes a first multiplexer having a first data signal input coupled to receive the first digital baseband signal and a second data signal input coupled to receive the second digital baseband signal from the wave shaper. The first multiplexer provides a multiplexed output signal including components of the first and second digital baseband signals. The modulator also includes a source of alternating samples of first and second carrier signals.
In one preferred embodiment, the source of alternating samples of first and second baseband signals includes a second multiplexer having a first signal input coupled to receive a first carrier signal and a second signal input coupled to receive a second carrier signal. The second multiplexer provides a multiplexed output signal including components of the first and second digital baseband signals. In another preferred embodiment, the source of alternating samples of first and second carrier signals includes an addressable memory device containing stored values corresponding to said samples of first and second carrier signals. In yet further preferred embodiments, the stored values are associated with consecutive addresses, in the order of occurrence of their corresponding samples of the baseband signals and a counter is provided for controlling access to said stored values in consecutive order of their associated addresses.
The modulator also includes a multiplier having a first input coupled to the output of the first multiplexer and a second input coupled to the source of carrier signal samples (i.e., the second multiplexer or the memory device). The multiplier is thereby coupled to provide a digital modulated output signal.
In this ma
Xin Weizhuang
Yang Ganning
Al-Beshrawi Tony
Chin Stephen
Conexant Systems Inc.
Foley & Lardner
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