Patent Application
20080137787
Bus clocks of computer system platform may become a source of interference noise. The interference caused by the bus clocks may severely degrade the performance of components and/or devices of the computer system platform. For example, in notebook platforms an antenna may be placed on a lid of the notebook platform. This may cause interference to an operation of a liquid crystal display (LCD) of the notebook platform.
In order to avoid some noise interference effects, the computer platform has to meet at least some Electro Magnetic Compatibility (EMC) requirements. To meet the EMC requirements, frequency modulating (FM) of the bus clock may be used to spread an interfered spectrum. The FM may include a modulation depth of 0.5% (e.g., periodically shifting the bus clock frequency between nominal minus 0.5% to nominal plus 0.5%). By providing FM to the bus clock, the average clock rate remains intact however; the interference at spectral power density of all the harmonics of the bus clock frequency may be reduced.
The FM may solved EMC issues, however this technique is not always sufficient to solve the EMC issues for communication devices because the communication channel includes the complete spread clock harmonics.
The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanied drawings in which:
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However it will be understood by those of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.
Some portions of the detailed description, which follow, are presented in terms of algorithms and symbolic representations of operations on data bits or binary digital signals within a computer memory. These algorithmic descriptions and representations may be the techniques used by those skilled in the data processing arts to convey the substance of their work to others skilled in the art.
Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining,” or the like, refer to the action and/or processes of a computer or computing system, or similar electronic computing device, that manipulate and/or transform data represented as physical, such as electronic, quantities within the computing system's registers and/or memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, or transmission devices.
It should be understood that the present invention may be used in a variety of applications. Although the present invention is not limited in this respect, the circuits and techniques disclosed herein may be used in many apparatuses such as platforms which include, but not limited to, a central processing unit, one or more buses, a clock bus, one or more memory, on or more video controller, one or more audio controller, one or more display controller, one or more wireless communication devices or the like.
Turning first to
According to one exemplary embodiment of the invention, a bus 180 may transfer data, commands and clock 110 to components and devices of computing platform 100. A clock rate of clock 110 may be, for example 14.318 MHz. The clock rate may generate harmonics 170 and/or 175. The harmonics 170 and 175 may be received by antenna 160 of GPS receiver 140 and/or by antenna 165 of WLAN device 130, respectively. For example, GPS receiver 140 may be tuned to GPS L1 band. In at least some GPS receivers, L1 band frequency is 1575.42 MHz+/−1 MHz. The 110th harmonic of clock 110 may be 1574.98 MHz which is within the GPS L1 band. For example, assuming 0.5% FM of clock 110, the harmonics of clock 110 may vary between 1566.55 MHz and 1582.85 MHz, although it should be understood that the scope of the present is not limited to this example.
In some exemplary embodiments of the present invention, a power of the 110th harmonic of clock 110 may be −90 dBm. Thus, the 110th harmonic may cause interference to a reception of a GPS signal. Interference controller 150 may include, for example, a table of one or more clock harmonics that may cause interference to devices of computing platform 110 (e.g., GPS receiver 140 and/or WLAN device 130). Furthermore, interference controller 150 may receive indication on an operation mode of devices of computing platform 110.
According to some exemplary embodiments of the present invention, interference controller 150 may control a modulation pattern of FM modulator 120. The modulation pattern is designed to remove harmonics that cause interference to an operating device of computing platform 110.
Turning to
It should be understood that the above pattern is an example only and other patterns may be used according to parameters that may have effect on the EMC of computing device 100. For example, frequency range, power of harmonics, and the like.
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According to one exemplary embodiment of the invention, interference controller 150 may sense an operation state of the device that might be effected by the interference (diamond 330) and may exclude sweeping clock frequencies that may cause the interference to the device which is in operation (text block 340).
Although the scope of the present invention is not limited in this respect, it should be understood that components of the present invention may be implemented by hardware, by software and/or any combination of hardware and software.
While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
