Patent Application
20080136513
1. Field of the Invention
The invention relates generally to an apparatus and method for amplifying baseband signals, and more specifically, to a power efficient method of providing for automatic gain control.
2. Discussion of the Related Art
A radio receiver in a wireless communication system is coupled to an antenna and includes a low-noise amplifier, programmable-gain amplifier, one or more intermediate frequency stages, a filtering stage, automatic gain control (AGC), and a baseband-processing stage. The low-noise amplifier receives transmitted RF signals via the antenna and amplifies them. The programmable-gain amplifier may further amplify the RF signals. The one or more intermediate frequency stages mix the amplified RF signals with one or more local reference signals to convert the amplified RF signal into baseband or intermediate frequency (IF) signals. The filtering stage filters the baseband or IF signals to attenuate unwanted out-of-band signals to produce filtered signals. The baseband-processing stage recovers raw data from the filtered signals in accordance with the particular wireless communication standard employed.
The signal strength of a received RF signal may vary substantially (e.g., by 100 dB). Thus, the AGC adjusts the gain of the low-noise amplifier, the programmable-gain amplifier, and/or digital gain within the baseband-processing stage such that the receiver is sensitive enough to detect received low-power signals and, once detected, to adjust the gain of these components to achieve nominal signal level. The AGC may also be configured to decrease the gain of the low-noise amplifier, the programmable-gain amplifier, and/or the digital gain of the baseband-processing stage when the received signal is a strong signal. Gain control typically comprises varying the load of an amplification circuit, thus dissipating power.
Embodiments of the invention are configured for performing automatic gain control for converting an IF and/or a baseband signal having a highly variable power to a signal having power within a predetermined range. A multi-stage amplification means comprises a plurality of fixed-gain amplifier stages and a switching means coupled to an AGC means. The AGC means is configured for controlling the switching means for bypassing at least one of the plurality of fixed-gain amplifier stages. Bypassing an amplifier stage reduces power dissipation. In one embodiment, the multi-stage amplification means comprises a fine gain adjustment means and a coarse gain adjustment means. The fine gain adjustment means may be configured for performing variable gain adjustment by adjusting a load-resistor value in at least one amplifier.
In one embodiment of the invention, a system configured for performing automatic gain control, comprises a multi-stage amplification means configured for amplifying a received baseband signal in a plurality of stages, and an AGC means configured for bypassing at least one of the plurality of stages in the multi-stage amplification means.
The multi-stage amplification means may include, by way of example, but without limitation, a sequence of amplifiers including a bypass switch arrangement. The sequence of amplifiers may comprise a plurality of baseband amplifiers, or a combination of at least one baseband amplifier, at least one IF amplifier, and at least one RF amplifier. The multi-stage amplification means may include a variable-gain amplifier for performing fine gain adjustment. The AGC means may include, by way of example, but without limitation, any apparatus or algorithm configured for operating the bypass switch arrangement to provide for gain control of a signal input to the multi-stage amplification means.
Although particular embodiments are described herein, many variations and permutations of these embodiments fall within the scope and spirit of the invention. Although some benefits and advantages of the preferred embodiments are mentioned, the scope of the invention is not intended to be limited to particular benefits, uses, or objectives. Rather, embodiments of the invention are intended to be broadly applicable to different wireless technologies, system configurations, networks, and transmission protocols, some of which are illustrated by way of example in the figures and in the following description of the preferred embodiments. 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.
Embodiments according to the present invention are understood with reference to the following figures.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the exemplary embodiments are not intended to limit the invention to the particular forms disclosed. Instead, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.
In accordance with one embodiment of the invention,
In one embodiment, the amplifier stages 113 and 115 (as well as stages 114 and 116) are configured for providing coarse gain adjustment.
A multi-stage amplifier in accordance with one embodiment of the invention may further include at least one variable-gain amplifier (such as amplifiers 109 and 110) configured for performing fine gain adjustment. In this case, the AGC module 154 is configured to adjust a load-resistor value in the at least one variable-gain amplifier 109 and 110.
Coarse gain adjustment 202 comprises performing automatic gain control to bypass at least one of a plurality N of amplification stages. For example, a decision 203.1 may be made to bypass an amplifier stage that provides a constant gain to an input signal. Otherwise the input signal is amplified 204.1. Such decisions 203.1-203.N may be made for each amplifier stage as a means for providing coarse gain adjustment to the received baseband signal.
It should be appreciated that those skilled in the art will be able to devise various arrangements, which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are intended to be only for pedagogical purposes to aid the reader in understanding the principles of the invention. This disclosure and its associated references are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof.
It should be appreciated by those skilled in the art that the block diagrams herein represent conceptual views of illustrative circuitry, algorithms, and functional steps embodying principles of the invention.
The functions of the various elements shown in the drawings, may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. The functions may be provided by a single dedicated processor, by a shared processor, or by a plurality of individual processors, some of which may be shared. A processor may include, without limitation, digital signal processor (DSP) hardware, read-only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and/or custom, may also be included. Similarly, the function of any component or device described herein may be carried out through the operation of program logic, through dedicated logic, or through the interaction of program control and dedicated logic, the particular technique being selectable by the implementer as more specifically understood from the context.
Any element expressed herein as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a combination of circuit elements which performs that function or software in any form, including, firmware, micro-code or the like, combined with appropriate circuitry for executing that software to perform the function. Embodiments of the invention as described herein reside in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the operational descriptions call for. Applicant regards any means which can provide those functionalities as equivalent as those shown herein.
