Patent Description:
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.

Portable information handling systems generally support mobile operations with processing components, input/output (I/O) devices and a power source integrated in a portable housing so that an end user may interact with the system free from external cable interfaces. For instance, tablet information handling systems integrate processing components and a battery in a planar housing covered by a touchscreen display that presents information as visual images and accepts touches as inputs. Convertible information handling systems generally distribute the processing components, battery and display between two separate rotationally coupled housing portions with one housing portion integrating the display and the other covered by a keyboard. A typical convertible information handling system rotates the housing portions from a closed position that protects the display by rotating it next to the keyboard to a clamshell position that holds the display vertically above the keyboard so an end user can type inputs at the keyboard while viewing the display. Some convertible information handling systems rotate the housing portions <NUM> degrees from the closed position to expose the display for use as a tablet.

Generally portable information handling system length and width dimensions are driven by the size of the display integrated in the housing. Often, end user's select information handling systems for a display viewing area and then weigh desired processing capabilities against system height and weight. Generally, more powerful processing components tend to have greater height and weight so that the processing components have adequate power and thermal operating constraints. As system height decreases, thermal constraints in particular become difficult to manage as the internal housing cavity tends to have less efficient cooling airflow. Some very thin systems maintain thermal constraints by relying on passive thermal transfer instead of including a cooling fan, however, active thermal management with a cooling fan generally offers a substantial increase in thermal management of more powerful processing components. Generally, information handling system manufacturers attempt to dispose processing components and active cooling resources in a portable housing in an efficient manner that allows for low Z-height.

One way to reduce portable housing length and width dimensions is to integrate the display in the housing with a narrow border along the perimeter of the display. Generally, to reduce the display border a variety of components typically included with the display housing portion are moved instead to the main housing portion. For instance, display housing portions often include a camera, microphone and wireless antenna that are instead moved to the main housing portion. Moving such components to the main housing portion tends to crowd areas of the main housing portion where the components are most convenient, such as along the base of the display. Wireless antenna placement presents a particular difficulty as the antenna radiation pattern faces increased interference and lower height in the main housing portion, which impedes wireless signal transfer. Further, to ensure adequate housing strength in the face of torsional forces introduced by rotation around hinges, metallic housing material is typically used, which further impacts wireless signal transfer. Although non-metallic windows may be included in the housing, these areas create weakness, such as in the case of a physical impact at the non-metallic window. In many cases, multiple antenna are included that communicate in shared frequency ranges, which will create isolation issues, especially within an all metal enclosure.

<CIT> discloses a computing device including electronic circuitry, and an antenna and heat venting chamber having an antenna radiating element disposed in at least a first plane, a ground plane element disposed in at least a second plane, a first side wall member defining a plurality of perforations, and a second side wall member having a portion that is disposed opposite to the first side wall member, where the portion of the second side wall member defines at least one opening. <CIT> discloses a wireless communication terminal comprising: a case having a bent hole formed in one side thereof; an antenna carrier disposed in the case such that a side thereof faces the bent hole, and including a duct passing through one side and the other side thereof; a fan disposed on the other side of the antenna carrier; and an antenna disposed on the antenna carrier and the top surface of the fan and having an antenna pattern for transmitting and receiving wireless signals, wherein the wireless communication terminal has the antenna and a heat dissipating structure disposed in proximity such that one member performs two or more functions, so as to provide a wireless communication terminal making good use of internal space. <CIT> discloses a heat dissipation apparatus including a housing, a heat-insulation structure, a fan and an antenna. The heat-insulation structure is disposed on the housing and the heat-insulation structure has a plurality of heat dissipation holes. The fan is disposed in the housing and an air exhaust channel is formed between the fan and the heat-insulation structure. The antenna is disposed in the air exhaust channel.

Therefore, a need has arisen for a system and method which isolates radiofrequency elements located in close proximity in an information handling system portable housing.

In accordance with the present invention, a system and method are provided which substantially reduce the disadvantages and problems associated with previous methods and systems for integrating antenna in an information handling system portable housing. An antenna structure disposed along one side of a housing supports plural antennas separated by a cooling fan disposed over the antenna structure to enhance isolation. In one embodiment, a tunable parasitic element disposed under the cooling fan exhaust further isolates the antenna.

More specifically, a portable information handling system processes information with processing components disposed in a housing having rotationally coupled main and lid portions. A display integrated in the lid portion presents information as visual images with a narrow edge so that antenna to support wireless communication are integrated in the main housing portion. An antenna support disposed along a rear side of the main housing portion supports first and second antennas at opposing ends, such as LTE antennas to support wireless wide area network (WWAN) communication. Isolation between the antennas is provided by a grounded metal housing of a cooling fan that exhausts between the antennas over the antenna support. In one embodiment, the cooling fan assembles in an opening formed in a motherboard and couples to a heat pipe that transfers heat from a central processing unit (CPU) coupled to the motherboard. A tunable parasitic element disposed on the antenna support between the antenna and under cooling fan adapts isolation to plural frequency bands based upon the isolation response of the cooling fan and heat pipe for each frequency band.

The present invention provides a number of important technical advantages. One example of an important technical advantage is that a cooling fan assembles at an information handling system motherboard between wireless antennas to isolate the antennas, thus reducing mutual coupling and improving radiofrequency efficiency. Grounded metal structures of the cooling fan and heat transfer structure absorbs radiofrequency energy transferred between the antennas to allow placement of the antennas in close proximity within an information handling system housing with less impact upon desired radiofrequency transmissions. Leveraging metallic structure of a cooling fan to provide antenna isolation reduces the need to add other structures dedicated to antenna isolation. In one embodiment, a parasitic element is added to further reduce mutual coupling and tuned to adapt the parasitic response to changing frequencies of the antenna.

The present invention may be better understood, and its numerous objects, features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference number throughout the several figures designates a like or similar element.

A portable information handling system assembles a cooling fan to extend over an antenna structure disposed along one side of a housing so that a grounded conductive surface of the cooling fan isolates the antennas from each other. For purposes of this disclosure, an information handling system may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components.

Referring now to <FIG>, a top view depicts a portable information handling system <NUM> having plural antennas <NUM> and <NUM> disposed in a main housing portion <NUM>. In the example embodiment, main housing portion <NUM> rotationally couples to a lid housing portion <NUM> with a pair of hinges <NUM>, such as dual axle hinges that provide <NUM> degrees of rotational movement of lid housing portion <NUM> relative to main housing portion <NUM>. For instance, lid housing portion <NUM> rotates from a closed position having a display <NUM> over top of a keyboard <NUM> to a clamshell position of about <NUM> degrees of rotation in which main housing portion <NUM> supports display <NUM> in a viewing position over keyboard <NUM> so that an end user can type inputs while viewing display <NUM>. As depicted, display <NUM> rests on a support surface opposite keyboard <NUM> after about <NUM> degrees of rotation, such as allows an end user to interact with a touchscreen of display <NUM> as a tablet. A full <NUM> degrees of rotation of lid housing portion <NUM> relative to main housing portion <NUM> disposes keyboard <NUM> under display <NUM> to support mobile tablet interactions by an end user. In the example embodiment, main housing portion <NUM>, lid housing portion <NUM> and a cover that holds keyboard <NUM> in position have a metallic construction to provide structure support against torsional forces introduced during rotational movement. Further, display <NUM> integrates in lid housing portion <NUM> with a narrow edge construction that enhances portability and provides a clean industrial design having images presented across the length and width of the lid housing portion.

Manufacture of information handling system <NUM> with a minimal boundary display <NUM> and with a metallic housing presents difficulty for the effective disposition of antenna in information handling system <NUM> to support wireless communication. In the example embodiment, an antenna support <NUM> is coupled to main housing portion <NUM> between hinges <NUM> along the rear side of main housing portion <NUM> to provide wireless signal pathway in support of a pair of wireless wide area network (WWAN) antennas <NUM> and <NUM>, such as to support communication with an LTE network. Placement of antennas <NUM> and <NUM> in close proximity can degrade antenna performance due to mutual coupling of the antennas during transmissions in channels, such as do to near field current effects. A parasitic element <NUM> is disposed between antennas <NUM> and <NUM> to further aid isolation. For instance, antenna support <NUM> is a printed circuit board having approximately <NUM> between hinges <NUM> with each antenna <NUM> and <NUM> having a length of approximately <NUM> so a minimal space of approximately <NUM> exists to place parasitic element <NUM>. Generally, a quarter wavelength of space is desired between antenna <NUM> and <NUM> to obtain sufficient isolation for reducing mutual coupling, however that amount of space is difficult to find in main housing portion <NUM>, especially where metallic material is desired for housing strength. In the example embodiment, wireless local area network antenna <NUM> and near field communication antenna <NUM> are also included and best operated with a clear wireless signal pathway. To obtain acceptable WWAN signal strength, further isolation of antenna <NUM> and <NUM> is desirable.

Referring now to <FIG>, bottom cutaway view depicts portable information handling system <NUM> having first and second antenna <NUM> and <NUM> disposed proximate a cooling fan <NUM> exhaust. Information handling system <NUM> processes information with a central processing unit (CPU) <NUM> that executes instructions and a random access memory (RAM) that stores the information and instructions. To remove excess thermal energy generated by CPU <NUM>, a heat sink and heat pipe <NUM> thermally couple to CPU <NUM> to transfer thermal energy towards a cooling fan <NUM>. Cooling fan <NUM> generates a cooling airflow past heat pipe <NUM> to draw thermal energy out of main housing portion <NUM>.

In the example embodiment, cooling fan <NUM> has a metallic or other conductive housing material and is placed to exhaust over top of parasitic element <NUM>. In the example position depicted, cooling fan <NUM> is placed between antennas <NUM> and <NUM> to aid in isolation of each of antennas <NUM> and <NUM>. For example, radio <NUM> grounded to a motherboard in main housing portion <NUM> communicates wireless signals to antennas <NUM> and <NUM> through a coaxial cable interface. Antenna support <NUM> grounds using gaskets with metal material extending from a keyboard cover described below. Cooling fan <NUM> couples to and grounds to the motherboard that supports radio <NUM>, as does heat pipe <NUM>. With the grounded metal structure of cooling fan <NUM> disposed between antennas <NUM> and <NUM>, isolation of antennas <NUM> and <NUM> is enhanced. Further, parasitic element <NUM> provides isolation by, in effect, forcing surface currents related to mutual coupling to travel along the ground plane, essentially creating a longer path for current to follow and making up for the "shortfall" in spacing between antennas <NUM> and <NUM>.

Referring now to <FIG>, a top view depicts an antenna support <NUM> having a cooling fan <NUM> extending between antenna <NUM> and <NUM> disposed on the antenna support <NUM>. Antenna support <NUM> has a side wall extending downward that defines an exhaust through which cooling fan <NUM> expels heated airflow. For the upper view of <FIG>, antenna support <NUM> is placed over cooling fan <NUM>. Referring now to <FIG>, a bottom view depicts antenna support <NUM> having cooling fan <NUM> disposed on the antenna support. Antenna <NUM> and <NUM> are formed on perpendicular sides of antenna support <NUM> with cooling fan <NUM> abutted against the back side of antenna support <NUM>. Placement of cooling fan <NUM> in between antenna <NUM> and <NUM> creates a metal structure inserted between the antennas that acts as an isolator, shield and grounding mechanism that aid antenna performance. The intersection <NUM> of cooling fan <NUM> and antenna support <NUM> defines antenna isolation between antennas <NUM> and <NUM> that are formed on opposing ends of antenna support <NUM>.

Referring now to <FIG>, a bottom exploded view depicts antenna support <NUM> integrated in a keyboard cover <NUM>. In the example embodiment, cooling fan <NUM> is sized to fit in an opening formed in motherboard <NUM> that aligns cooling fan <NUM> between antenna <NUM> and <NUM>. The opening in motherboard <NUM> allows freedom along the Z-axis or height of information handling system <NUM> to adjust placement of cooling fan <NUM> in a manner relative to antenna <NUM> and <NUM> that optimizes radiofrequency isolation, thus improving antenna performance. Heat pipe <NUM> is formed as necessary to fit over CPU <NUM> and communicate thermal energy from CPU <NUM> to the exhaust of cooling fan <NUM>. In the example embodiment, antenna support <NUM> defines antenna <NUM> and <NUM> on a flexible printed circuit board folded into perpendicular sections and held in position by a plastic molded support <NUM> and interfaced through a cable connection <NUM>. Support <NUM> couples to a radiofrequency window <NUM> integrated in a keyboard cover <NUM>, such as with snaps or other coupling mechanisms. For example, radiofrequency window <NUM> has a hardened thermoplastic material that also forms an exhaust vent <NUM> for exhaust of cooling fan <NUM>. Keyboard cover <NUM> is a metallic material, such as aluminum, that provides increased structural strength to help resist torsional forces introduced at a low Z-height housing during rotational movement. Metallic members <NUM> extend downward from keyboard cover <NUM> proximate window <NUM> to help further isolate antenna <NUM> and <NUM>. For example, antenna support <NUM> is grounded to members <NUM> with gaskets so that members <NUM>, cover <NUM>, cooling fan <NUM>, heat pipe <NUM> and motherboard <NUM> all share a common ground. In addition, members <NUM> aid in capture and retention of antenna support <NUM>.

Referring now to <FIG>, top view depicts the antenna support <NUM> extending out from the keyboard and having the radiofrequency window <NUM> removed. Keyboard <NUM> extends through key openings formed in cover <NUM> to accept key inputs from an end user. Antenna support <NUM> extends outward from cover <NUM> to provide a clear radiofrequency pathway for transmission of wireless signals. As explained above, cooling fan <NUM> fits under parasitic element <NUM> midway between antenna <NUM> and <NUM>. Referring now to <FIG>, a bottom view depicts antenna support <NUM> extending out from the keyboard <NUM> and having the radiofrequency window <NUM> removed. From the bottom view, placement of cooling fan <NUM> over parasitic element <NUM> and between antenna <NUM> and <NUM> is illustrated. Referring now to <FIG> a side view depicts antenna support <NUM> having the radiofrequency window <NUM> removed. Cooling fan exhaust <NUM> formed in the plastic molded support <NUM> of antenna support <NUM> provides openings through which cooling fan <NUM> exhausts heated air.

Referring now to <FIG> an upper perspective view depicts the antenna support <NUM> having the radiofrequency window <NUM> removed. In the example embodiment, antenna <NUM> supports auxiliary LTE communications and antenna <NUM> supports main LTE communications. Each of antenna <NUM> and <NUM> are printed circuits defined in a flexible printed circuit board and folded over a non-conductive plastic molded support base <NUM> to extend outward from keyboard <NUM> and cover <NUM>. Parasitic element <NUM> is disposed between antenna <NUM> and antenna <NUM> and tuned to reduce mutual coupling, such as can be caused by surface currents extending between antenna <NUM> and antenna <NUM>. As illustrated by <FIG>, parasitic element <NUM> may include conductive elements that extend downward between cooling fan <NUM> exhaust <NUM> openings. In various embodiments, antennas and parasitic element printed circuits may have various forms as desired to transmit desired wireless signals, such as WLAN signals, and with various antenna configurations, such as MIMO antenna configurations. Antenna tuning will depend upon the desired wireless transmission signal frequencies, the space between hinges of the housing that is available for the antenna structure, and the relationship between system ground and the antenna where ground may include cooling fan <NUM> and heat pipe <NUM>.

Referring now to <FIG> a graph illustrates isolation performance of the antenna support <NUM> with cooling fan <NUM> over antenna support <NUM> and withdrawn from a position over the antenna support. The example graph includes S-parameters in dB for antenna interference with cooling fan <NUM> pushed into position between antenna <NUM> and <NUM>, and for cooling fan <NUM> pushed backwards away from antenna <NUM> and <NUM>. Although antenna performance varies along the radiofrequency spectrum and targets desired transmission bands, generally an improvement of 20dB in antenna efficiency is provided by improved isolation resulting from placement of cooling fan <NUM> between antenna <NUM> and <NUM>. The improved performance is generally provided in a restricted space by disruption of mutual coupling with the shared ground structures, however, as frequency shifts between different bands, resonance of the mutual coupling shifts so that tuning of the ground response can further adjust antenna performance.

Referring now to <FIG>, a circuit block diagram depicts a radio module <NUM> that adopts parasitic element <NUM> resonance based upon antenna frequency. In the example embodiment, radio module <NUM> is an integrated circuit having GPIO and/MIPI interfaces to control antenna and parasitic element resonance. Radio module <NUM> communicates wireless signals to antenna <NUM> and <NUM> through RF ports <NUM> and <NUM> and an impedance switch and tuner <NUM> and <NUM> disposed between each antenna <NUM> and <NUM>. In the example embodiment, radio module <NUM> tunes antenna <NUM> and antenna <NUM> to support four different LTE frequency bands: B12 (<NUM>-<NUM>); B29/<NUM>/<NUM>/<NUM> (<NUM>-<NUM>); B26/<NUM>/<NUM>/<NUM>/<NUM>/<NUM> (<NUM>-<NUM>); and B8 (<NUM>-<NUM>). For example, impedance switch and tuner <NUM> and <NUM> selects LC circuit values to match antenna <NUM> and <NUM> impedance to the frequency of radio module <NUM>. Radiofrequency tuning may also depend upon detection of bodies proximate to antenna <NUM> and antenna <NUM>, such as may introduce near field effects that interfere with antenna impedance tuning. For example, a Hall sensor <NUM> is monitored by sensor logic <NUM> to trigger a sensor hub <NUM>, such as when a tablet mode rotates the housing portions in proximity to each other. Radio module <NUM> may select impedance tuning settings for antenna <NUM> and <NUM> based upon a trigger from such a proximity detection.

As an example, of impedance tuning based upon inputs by a Hall sensor <NUM>, radio module <NUM> stores antenna impedance tuning states for each of plural housing configurations and applies the stored antenna impedance tuning states based upon Hall sensor output. For instance, in a clamshell mode Hall sensor <NUM> detects the rotational orientation of lid housing portion <NUM> rotated <NUM> degrees relative to main housing portion <NUM>. In response to detection of clamshell mode, radio module <NUM> looks up impedance values for the selected LTE band at a clamshell rotational orientation and applies the impedance values to adjust the impedance of antenna <NUM> and <NUM> and parasitic element <NUM>. The impedance values reflect an expected impact on radiofrequency characteristics for the relative position of lid housing portion <NUM> to antenna support <NUM>, such as near field effects created by the metal material of lid housing portion <NUM>. In various embodiments, stored impedance values to apply to antenna <NUM> and <NUM> and to parasitic element <NUM> may be kept for a variety of orientations of lid housing portion <NUM> relative to main housing portion <NUM> as desired based upon experiment antenna performance. Further adjustment of antenna impedance may be performed by measuring capacitive effects associated with the proximity of lid housing portion <NUM> to antenna support <NUM>, such as by monitoring capacitance to detect object proximity, such as to maintain SAR constraints as set forth in <CIT>, entitled "Information Handling System Radio Transmit Power Management', published as <CIT>.

In addition to tuning antenna <NUM> and <NUM>, a GPIO interface <NUM> of radio module <NUM> interfaces through an SP4T switch <NUM> or similar selection structure to tune parasitic element <NUM>. For example, SP4T switch <NUM> has a setting for each of the four LTE frequency band groups described above. The isolation performance of parasitic element <NUM> varies based upon the ground structure interfaced with it. For instance, the size of the conductive housing of cooling fan <NUM> and the length of heat pipe <NUM> will each impact the isolation of mutual coupling between antenna <NUM> and <NUM> provided by parasitic element <NUM>. Thus, in various embodiments, logic in radio module <NUM> considers the frequency at which antenna <NUM> and <NUM> communicate, the size and length of ground structures interfaced with antenna structure <NUM>, and the detection of proximate object when setting resonance of parasitic element <NUM>.

Claim 1:
A portable information handling system (<NUM>) comprising:
a housing (<NUM>; <NUM>);
a motherboard (<NUM>) coupled to the housing (<NUM>; <NUM>);
a processor coupled to the motherboard (<NUM>) and operable to execute instructions that process information;
a memory coupled to the motherboard (<NUM>) and interfaced through the motherboard (<NUM>) with the processor, the memory operable to store the instructions and information;
a radio (<NUM>) interfaced with the processor, the radio operable to communicate wireless signals;
first and second antennas (<NUM>; <NUM>) interfaced with the radio (<NUM>) and disposed at one side of the housing (<NUM>; <NUM>), the first and second antennas (<NUM>; <NUM>) operable to transmit and receive the wireless signals; and
a cooling fan (<NUM>) with a grounded metallic material coupled to the motherboard (<NUM>), disposed between the first and second antennas, and having an exhaust at the one side of the housing (<NUM>; <NUM>).