Communications: electrical – Condition responsive indicating system – With particular system function
Reexamination Certificate
2000-04-25
2003-02-25
Crosland, Donnie L. (Department: 2632)
Communications: electrical
Condition responsive indicating system
With particular system function
C340S515000, C455S067150, C455S067700, C455S115200, C455S423000, C324S750010, C324S759030, C324S612000
Reexamination Certificate
active
06525657
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of radio frequency radiation testing for wireless communications devices and, more particularly, to a testing apparatus and method suitable for high speed testing and analysis of RF performance of wireless devices during mass production thereof.
BACKGROUND OF THE INVENTION
Numerous types of wireless communications devices are if being used for various purposes and the number of such devices being developed and produced for public use is growing rapidly worldwide. These devices operate over a wide range of radio frequencies and output power levels. The cellular telephone devices which are now common, for example, operate in the 800 or 900 MHz range and at power levels of about 600 mW while blue tooth devices operate in the 2.4 GHz range at significantly lower power levels. For most such devices, and particularly in the case of cellular telephones, there are technical standards (e.g. the Federal Communications Commission (FCC) in the U.S.A. or the Radio Standards Specifications (RSS) of the department of Industry Canada of the Canadian Government) and safety regulations (e.g. the Safety Code of Health Canada, a department of the Canadian government) which must be complied with by the manufacturers and carriers thereof in order to obtain government approval and avoid sanctions. Increasingly, these standards are providing narrower windows of acceptable performance levels which must be met by manufacturers, the reason being that more and more of the frequency spectrum is being carved up and allocated for wireless applications and an increasing number of geographic cells are being allocated for wireless communications. Consequently, a trend is underway whereby reduced power levels are being mandated for such devices. It is, therefore, becoming increasingly important to the usefulness of such devices that they utilize the full power level permitted to them in order to achieve their designated geographical coverage. This trend poses a challenge to the manufacturers of wireless devices to reduce their manufacturing tolerances for the operational power output levels of these devices so that for any given device one may be certain that, in operation, it will not exceed the maximum permitted power levels but will also not fall significantly below such maximum.
In addition to regulations imposing a more rigorous budgeting of power for purposes of allocating limited frequency resources, there is also a growing climate of concern for the health and safety issues relating to RF transmissions and the associated human radiation absorption levels. Regulatory standards, such as the Canadian Health Code, now exist to limit such absorption levels and these are referred to as SAR (Specific Absorption Rate) limitations. Many publications directed to SAR testing exist in the art and, as examples of these, reference is made to Health Canada Safety Code SC6 and the various reports and conference papers which are available through the Internet at the Website www.aprel.com of Aprel Laboratories of Nepean, Canada.
The purpose of SAR testing is to measure the electric field inside of simulated human tissue (i.e. simulated head and hand or body tissue) to determine the amount of RF energy which the tissue is absorbing when exposed to radiation from an RF source. SAR is calculated from the E-field (E
2
) measured in a volume grid of test points within the tissue and is expressed as RF power per kilogram of mass, averaged in 1 cubic centimeter (or 1 gram) of tissue for head tissue or 10 cubic centimeters (or 10 grams) for hand or body tissue. A human-like manikin or Unihead “phantom” container is used to hold a tissue simulation solution designed to simulate head tissue and a similar solution is used to simulate hand or body tissue. The wireless device under test (DUT), for example a cell phone, is positioned close to the phantom (usually directly below the reference center of the container) and an isotropic E-field probe (a dipole probe) is successively, precisely located within the tissue simulation solution, over a stepped series of positions covering the volume of the solution, by means of a robotic probe positioner. The complete SAR testing is, of course, completed in an electromagnetic controlled environment. The stepped re-positioning of the probe is done very slowly because the tissue simulating solution must be uniformly still and stable for all of the position tests in order to achieve useful results. Typically the E-field measurements are taken over a grid comprising a total of over 100 target test positions during standardized SAR testing. Therefore, the time required to complete such SAR testing is typically hours and such lengthy tests are unsuitable for production line testing.
However, the developed SAR testing standards are not uniform around the world and much debate exists over various aspects of the testing tools and methodology used to measure SAR performance. Moreover, because the objective of such standardized testing methodologies is to produce absolute measurements the test procedures which have to date been developed are complex, lengthy and laboratory-based. Consequently, the existing standardized tests are useful only for generic approval testing of specimens and cannot be used within the manufacturing process itself to test individual production units. There is, however, a strong need for a means of fast and effective production testing to ensure not only the compliance of production units with regulatory standards but to ensure also that specification tolerance limits (which may be specific to particular carriers) are met by those units.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the invention there is provided a radio frequency (RF) testing apparatus for rapid testing of a-wireless communications device for operational adherence of the device to a pre-determined reference specification defining specific absorption rate (SAR) parameters correlated to the device. The device is positioned within an RF shielded enclosure (chamber) and is operated at a test transmit power during the testing. A plurality of means for measuring electric-field (e.g. isotropic E-field probes) are position at a pre-determined location within human tissue simulation matter and take measurements of an electricfield at the location which are transmitted to receiving means. The measurements are compared (preferably by computer processing means) to the SAR reference specification and a determination is made whether the device adheres to the specification. Preferably, this also determines a measure of the metallic system integrity of the device. Preferably, a linear array of uniformly spaced E-field probes are provided.
The enclosure is of a sufficiently small size to permit the apparatus to be incorporated into a production line for manufacturing wireless communication devices and has reflective surfaces therein.
Also in accordance with the invention there is provided a radio frequency (RF) testing apparatus for rapid testing of the body loss of a wireless communication device positioned within an RF shielded enclosure having reflective surfaces therein and operating at a test transmit power during the testing. A plurality of RF power measuring means (e.g. isotropic probes) are spatially distributed within the enclosure and take measurements of the RF power received thereby. Those measurements are combined, preferably by computer processing means, and a value representing the averaged integrated body loss of the device is produced. One of the RF power measuring probes is preferably located within A the enclosure at a hot spot for the RF power for producing signal value representing the operating effective radiated power for the wireless communications device.
In a preferred embodiment of the invention (RF) multi-testing apparatus is provided according to the foregoing for rapid simultaneous testing of the body loss of a wireless communication device and operational adherence of the device to a pre-determined reference speci
Aprel, Inc.
Crosland Donnie L.
Woodcock & Washburn LLP
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