Patent Application
20230007808
The present invention is concerned with the removal of heat from heat-generating electric and electronic components of telecommunications equipment received within an environmentally hardened housing. In a more specific aspect, the invention is concerned with wireless telecommunication equipment which is deployed outdoors and susceptible to environmental conditions requiring the use of environmentally hardened housings.
Fixed wireless services typically use directional radio antennas on each end of a signal transmission channel. Such antennas are often mounted to buildings, transmission/repeater towers, poles, etc. Because they are designed for an outdoor environment, telecommunication antennas are typically housed in radomes or other housings that are weatherproof (i.e. environmentally hardened) to protect the delicate electronic and electric components associated with the antennas from ambient conditions such as rain, debris, air pollution, etc., while still permitting the unhindered propagation of electromagnetic radiation, particularly radio waves, to and from the protected antenna.
Development of Multiple Input Multiple Output (MIMO) technology for fixed wireless telecommunication systems, including 4G LTE (Long Term Evolution), has meant that a comparatively larger number of power-consuming, heat generating electronic components are housed in a common housing with the various antennas used. Typically, outdoors mounted enclosures for wireless transmission equipment, such as 4G LTE routers/modems, MIMO antenna base stations and modems, and the like, as well as stationary user equipment installed at (end) user premises, need to be rated ‘dust and water tight’ (e.g. IP65 standard). Meeting such requirements in turn makes the removal of heat generated by the electronic and electric components from within the housing and its dissipation/transfer into the surrounding ambient air difficult. Fan forced convection cooling systems typically employed in the computer industry are unsuitable for use in the essentially hermetically sealed enclosures of 4G outdoor antenna equipment/modems.
In conventional, directional wireless transceiver units/modems, heat generated by electronic circuits and other components typically received on a printed circuit board (PCB) and associated with the antenna elements, is conducted to a (metallic) finned heat sink mounted on the side of the enclosure or housing opposite the radiating antenna elements. For that purpose, one or more heat conducting bodies are placed in direct contact with the heat generating components at the PCB as well as the heat sink. Waste heat, which if not efficiently removed adversely affects the performance of the electronics, is thus first conducted from within the housing to the heat sink from where it is in turn transferred into the ambient surroundings (air) by convection and radiation.
The introduction of 5G, the 5th generation of mobile networks, requires a more dense deployment of outdoor modem/repeater/router units, hereinafter simply called mini base stations for ease of reference, which are specifically designed for the very localised wireless coverage of 5G, typically from 10 to a few hundred meters. These mini base stations provide ‘in-fill stations’ for the larger macro network. These small cells and user equipment (UE) are essential for 5G networks as the mmWave frequencies 5G employs have a very short connection range.
Deployment of 4G LTE and 5G systems in their application in fixed wireless access and the desire/need to maintain reverse compatibility with 3G and 4G systems, thereby to service a larger number of frequency bandwidths, also means that dedicated outdoor 4G LTE and 5G mini base stations will typically have an increased number of electronic and antenna components received within a common housing.
The increase in electronic components to operate the various antennas for the specific frequency band widths allocated to 3G, 4G, 4G LTE and 5G, in particular where such are mounted on a common PCB as is planned, in turn means not only an increase in power consumption and thus heat generation within the sealed housing, but also increased heat source densities within a relatively small foot print enclosure/housing.
Noting that 4G LTE/5G outdoor fixed wireless mini base stations are to have an as small as possible form factor for the housing, inclusive of associated thermal load dissipating arrangements, it will be necessary to devise improved thermal load dissipation strategies to take account of the increased power consumption and heat generation of such units.
An additional issue arises from the use of the mmWave frequency bands in 5G. Signals transmitted in the mmWave frequency bandwidth ‘bounce’ a lot during the day, either due to localised atmospheric changes or the temporary presence of objects in the radiation paths between mini base stations. In order to maintain optimal antenna performance in receiving/transmitting signals, re-orientation (about an axis in the radiation plane of the antenna(s) incorporated in the fixed modem/mini base station units) will need to take place more often than with traditional antennas used eg in 3G networks. It would be impractical to provide for manual re-orientation of the entire unit, therefore necessitating some mechanism that allows for automated mechanical re-orientation of mini base stations and UEs, without compromising the thermal load dissipation arrangement.
In accordance with a first aspect, the present invention provides an outdoor-mountable, telecommunications module, such as a fixed wireless modem/router module, comprising an environmentally hardened housing, telecommunications equipment encased within the housing and disposed for rotation about an axis within the housing, and a thermal load mitigation system employing (i) thermal conduction of heat from at least some heat-generating components of the telecommunications equipment which in one non-limiting embodiment comprises a PCB including mmWave antenna signal generation and processing components providing a plurality of heat sources, as well as signal radiators/receivers (antennas), to a rotatable heat sink received within the housing, (ii) primarily conductive heat transfer across a small air gap between the rotatable heatsink and a non-rotating, stationary heat sink component collocated within the housing, and (iii) convective heat dissipation into the environment from a radiator disposed outside of the housing and which is in direct heat conductive connection with the non-rotating heat sink component disposed inside of the housing.
In the context of telecommunications equipment suitable for coverage of 3G, 4G, 4G LTE and 5G bandwidths, most if not all of the processors (ICs) used for 3G and 4G functionality generate a level of heat that can be allowed to radiated into the inside of the housing without a need to use dedicated heat mitigation or removal arrangements. Typically experienced heat loads are ultimately able to be ‘dissipated’ through the housing walls into the surrounding environment without raising the temperature within the housing to a degree adversely affecting operation of the electronic processors.
On the other hand, however, processors for 5G implementation generate heat amounts that require the use of dedicated heat transfer (i.e. removal) arrangements capable of removing larger heat amounts in shorter periods of time and direct the heat into the rotatable heat sink (as will be described in more detail below), then from the latter into the stationary heat sink that cooperates with the former, and from there into the housing-external convective radiator structure/arrangement.
Relevantly, the various structures and components that make up the thermal mitigation system will be designed and dimensioned such as to prevent the inside volume of the enclosure and in particular the heat generating electronic and electric components of the antenna signal generators housed on the rotatable PCB from reaching steady-state operating temperatures that negatively affect or over time degrade performance of the electric and electronic components, typically around environmental temperature levels of +55° C. Selection of suitable components/structures of the thermal mitigation system, and optimisation of their size and shape, aims to create an as small as possible module size and footprint, whilst maintaining a steady operating temperature within the housing that reflects the specification (recommended maximum operating temperatures) of the internal electronic components of the telecommunications equipment.
Embodiments and structures for the thermal mitigation system will be described below.
The thermal load mitigation system may optionally also provide means for (iv) convective heat removal from some of the lower-heat generating components into the housing through a finned heat sink thermally conductively coupled to these heat sources, and preferably also to the rotatable heat sink so that heat can also be directed into the latter.
Although air is usually viewed as an insulator when planning heat transfer management, the thermal mitigation system in accordance with the present invention makes use of an ‘air gap’ in the heat transmission path inside the housing between the rotatable heatsink and the non-rotating heat sink component collocated within the housing, as there is a risk that any low-viscosity thermal interface material (fluid) disposed between the rotatable and the co-operating stationary heat sink bodies could seize at low temperature or degrade over time with the fluctuations in temperature expected during normal operation.
In order to provide for an as efficient as possible thermal conductance path between the enclosure-internal rotatable heat sink and the enclosure-internal stationary heat sink, which comprises air gaps, whilst maintaining free relative rotational capability between the two heat sink components, it is advantageous for both sink components to comprise a plurality of concentric annular fins that interleave with each other in a manner that an as small as possible but rotation-enabling air gap is maintained between facing surfaces of the fins. Thermal expansion and contraction of the fins in the temperature operating range of the modem, typically in external environmental conditions of between −40° C. to +60° C., needs to be catered for. Preferably, the housing-internal, rotatable heat sink is made of the same metal alloy material as the co-operating housing-internal, stationary heat sink.
The width of the air gap between the fins of the rotatable and stationary enclosure-internal heat sink structures will be selected based on heat transfer efficiency, manufacturing machining tolerances as well as expected maximum and minimum operating temperatures within the housing, to cater for thermal expansion/contraction of the interacting components. Based on computer modelling, a possible iteration uses a gap of 1.0 to 1.5 mm between the surfaces of the concentric fins, which has been chosen for ease of manufacturing to the required tolerances. Using suitable aluminium alloys for the heat sink structures described, modelling suggests that this can achieve a 10° C. temperature differential between the housing-internal heat sink and the housing-external heat radiator at an ambient temperature of +55° C. in steady state operation of an outdoor 5G-enabled telecommunications module.
In an advantageous embodiment, the housing-external convective radiator structure/arrangement is provided on/at a closure member for an access opening of the housing. In this manner, the same module housing may be used for PCBs carrying different types of heat generating components, and therefore different overall heat generation ratings can be catered for, whereby radiator structures optimised as regards a specific one or more of heat removal ratings can then be provided/mounted to the closure member.
A particularly advantageous module format is one consisting of a preferably cylindrical housing having either an integral but preferably separate bottom closure cap, and in which the closure member is a cap or top closure member of the main cylindrical housing part which in operation is arranged in a generally vertical orientation.
In a preferred form, both the non-rotatable, housing-internal heat sink and the enclosure-external convective heat radiator are integrally formed with the closure member out of a suitable metal of high thermal conductivity, eg an aluminium alloy, thereby avoiding any interfaces in the heat conduction path between inside and outside of the enclosure (modem housing) comprising materials that conduct heat more poorly than an integral/unitary metallic body. It is possible though to manufacture the different heat transfer structures separately and assemble these together.
Advantageously, the enclosure-external convective heat radiator comprises a plurality of pin-like radiation elements in mutually spaced apart array configuration, such as concentric rows of upstanding pin elements spaced apart to maintain a predetermined small air gap with respect to each other, preferably no less than 0.5 mm, and more preferably around 1.0 to 2.5 mm. A different array configuration of the plurality of pins can of course also be selected, e.g. an orthogonal square array of interspaced pin rows.
Metallic pin elements that stand proud from and are integral with a base plate of the enclosure closure member, and spacing the plurality of pins appropriately, are selected to facilitate conductive but primarily convective heat transfer into the ambient air surrounding the housing (herein after also referred to as an enclosure).
The pins may be cylindrical, square or of other cross-sectional shape, and may not necessarily all have the same length (above the base plate), thereby creating a non-uniform temperature field across the entirety of pins which is conducive to thermally-induced air flow about the radiator.
The housing-external radiator employs a pin design because it is believed to be an effective form of heat transfer structure that does not require (additional) air flow or convection assisting structures or devices.
In accordance with other embodiments, fin-like structures instead of pin-like elements may be used in the convective radiator. The fins can have a variety of shapes and can be arranged in various configurations. The optimal combination of shapes and arrangements can be determined using software-based heat transfer optimisation models. In this context, although developed for a different purpose (heat removal from high-power LED lighting applications), finned heat radiator structures (heat sink) as proposed in the following documents could be used: ‘Optimum design of a radial heat sink with a fin-height profile for high-power LED lighting applications’, Daesok Jang, Se-Jin Yook, Kwa-Soo Lee, Applied Energy 116 (2014) p. 260-268, and ‘Optimization of a chimney design for cooling efficiency of a radial heat sink in a LED downlight’, Seung-Jae Park, Daesok Jang, Se-Jin Yook, Kwa-Soo Lee, Energy Conversion and Management 114 (2016) p. 180-187.
The fin-like structures may advantageously comprise a series of radially extending fins. In one form, the fins are all the same width and thickness and are arranged in concentric rings around the radiator. Each ring can have fins of a different height. The rings can increase in height towards the centre of the radiator to produce the appearance of a frustoconical shaped outer profile. Alternatively, the rings can decrease in height towards the centre of the radiator to form the appearance of a frustoconical shaped depression in the radiator. Heat transfer and heat dispersion from the heatsink can be optimised by changing the height of each ring or by changing the height of individual fins.
In another form, the fins are all the same height and comprise fins that extend over most of the radius of the radiator interspersed between fins that extend less than the radial extent of the first mentioned fins, eg ¼ to ⅓ or ½ of the radius of the radiator structure.
From a practical perspective, noting the intended environment of use of the modem in outdoor conditions, the housing-external heat radiator structure will be devised to prevent water from pooling, trapping of debris, take account of solar loading, amongst others.
An additional concept foresees the use of a chimney or funnel structure at the housing on top of the housing-external heat radiation structure. The chimney may be fitted on top of the radiator to further improve cooling efficiency. The chimney may comprise a pipe section with a flanged end, such that when the chimney is assembled onto the radiator the flanged end abuts a top surface of the fins.
Using a radiator design with a plurality of radial fins (instead of pins) has been investigated using thermal simulation tools. Use of a topping funnel structure allows for optimised convection airflow over the heat exchanger fins, i.e. the creation of an updraught of air entering radially into the zone of heat exchanger fins and discharging upwardly through the funnel. All else being equal, the presence of such funnel structure when used with a radiating heat sink having radiator fins, will in most cases improve overall cooling efficiency by a noticeable % degree as compared with modem embodiments devoid of such funnel structure. An advantage of the chimney/funnel structure is that it can serve to reduce the total amount of material required to manufacture the radiator component without compromising heat transfer capacity into the surrounding air. The chimney part can be moulded from the same plastic material as the main housing part and will also act as a solar shield and provide the heat sink structure with some protection from foreign materials.
In a preferred embodiment, the thermal mitigation system uses at least one heat pipe for assisting with the conductive heat transfer away from the high heat generating IC components on the telecommunications equipment PCB. For such purpose, the heat pipe(s) is (are) directly thermally coupled to the components (but electrically isolated from these) or indirectly via a heat spreader body mounted to the PCB, and the rotatable heat sink. The heat spreader body could have fins for convective heat transfer, as noted above, but in one embodiment will not incorporate features that promote convective heat transfer from the heat spreader into the housing, and will rather be devised to primarily remove the heat load received through heat conduction into the rotatable heat sink.
Preferably, alcohol-filled copper heat pipes are used, specified to meet a minimum operating temperature requirement of −40° C. without freezing.
Noting that liquid-filled heat pipes are most effective when drawing heat upward from a heat source, in a most preferred embodiment of the modem, the external heat radiator (and the co-working housing internal rotatable and non-rotatable heat sinks) will be located, in use of the modem, at the top of the modem unit, and the heat pipe(s) and PCB-mounted, associated heat spreader body will extend primarily in a vertical orientation.
In another aspect, the present invention provides the components of a thermal mitigation system for use with a PCB-based antenna, as described above, either in a preassembled format with the PCB antenna, or as a kit for incorporation into a stationary RF-transmission module/modem/router for outdoor use.
In accordance with a further embodiment, a mounting arrangement can be provided at the housing, for mounting the fixed wireless modem/router module to a vertical pole, the mounting arrangement comprising a first clamping unit that includes a section of the modem/router module and a first clamping element extending from the modem/router module section, and a second clamping element, with the first and second clamping elements being configured to be connected together in clamping engagement with the pole, wherein in use the modem/router module can be releasably secured to a top section of the pole by clamping the first and second clamping elements to the pole, with the modem/router module being positioned in relation to the pole such that signals to and from the modem/router module are unobstructed by the pole or the mounting arrangement through 360 degrees.
Further features and aspects of the invention will become clearer from the following description of two, non-limiting embodiments of the invention provided with reference to the accompanying drawings. It will be understood that features illustrated in the various embodiments may be interchanged where such are functionally equivalent.
The accompanying drawings illustrate schematically in various views two embodiments of a 5G/4G LTE reverse-compatible, outdoor-mountable, fixed wireless modem/router module 10, 100 with respective thermal mitigation systems 30, 130.
But for differences specifically mentioned below, the embodiments illustrated in
Turning then first to
Housing part 12 is made of a suitable, environmentally-hardened, RF-transparent polymer, such as ASA or PC with an ideally as close to 0 dielectric loss factor, and which in essence is not heated by RF-radiation emanating from within the module.
Module 10 will be supported/fastened in use to an outdoor structure like a building wall or a post using non-illustrated mechanical fasteners in a vertically upright position, with the closed end 14 oriented towards the ground. The outside of housing part 12 may also have appropriately formed mounting structures.
The wall thickness and additional rigidity imparting structures like internal or external ribs or webs have been omitted from housing 12 for clarity purposes. The cylindrical main housing part 12 could also incorporate external heat radiation fins, as is otherwise known from other electrical devices with heat sources arranged within a sealed-off, so-called environmentally hardened casing, but this is less preferably as such structures can interfere with the radiation pattern of the antenna elements located within the modem 10.
Modem unit 10 is configured specifically as a cellular outdoor modem with both omni-directional antenna elements and directional antenna elements that may require sporadic spatial re-orientation. A typical (but not limiting) size for such modem would be 100 to 200 mm in diameter with a height of 350 to 450 mm.
Modem 10 uses PCB antenna technology which is known to the skilled person in fixed telecommunications equipment. A single, main PCB carrier 20 supports several PCBAs and other components like transformers, including a 5G mmWave modem chip 22a, mmWave active antenna modules 22b, sub-6 GHz antenna elements 22c, an ethernet controller chip 22d, high speed transceiver(s), device power management circuitry, etc. In the figures, these components are only illustrated schematically.
Typically, the RF antenna elements 22b and 22c are disposed on one face of the PCB 20 to radiate in a direction Normal to and away from a main plane of the PCB 20 (i.e. not through the PCB) while driving and power circuitry components (such as modem chip set(s) 22a, 22d, etc.) are mounted on the opposite face of PCB 20. The skilled person in telecommunications equipment, particularly fixed wireless equipment for use in 4G LTE and 5G, will appreciate however that there are a variety of suitable electronic components, antenna modules and driving circuitry components and arrangements that can be chosen for incorporation into a single PCB and various PCBA configurations.
Noting that the directional antenna modules 22a are mounted to the PCB 20 to essentially receive and radiated RF-signals from one face (or plane) of the sheet-like PCB only, and that signals transmitted and received in the mmWave frequency bandwidth ‘bounce’ a lot directionally, PCB 20 is received and mounted with its principal plane perpendicular to the horizontal reference ground and for stepwise (or non-stepwise) rotation about a vertical central axis within housing 12 thereby to enable selective (re-)orientation of the directional antennas with one degree of rotational freedom.
There are various ways of specifically implementing a suitable support arrangement of the PCB 20 within housing 12 that allows the PCB 20 to be rotated (and thus the antennas 22b re-oriented) and various drive arrangements to effect such rotational re-alignment can be chosen.
In the embodiment of
In contrast, the embodiment of
An annular bearing flange 116 with a ring of radially-inward directed teeth 117 provides an annular gear element that is sandwiched between the upper terminal rim portion 114a of bottom cap 114 and a facing ledge or step which collar 115 forms with housing 120, such that bearing flange 116 is secured against movement (rotation and axial). Additional measures can be provided to secure annular gear element/bearing flange 116 against rotation, such as glue, index features, etc. Annular gear element 116 could be made of metal but equally of a suitable polymer material, such as glass reinforced polyester or the like, having high impact resistance yet sufficient E-modulus to provide form stable teeth 117 into which comb a pinion 127 driven by the output axle of electric stepper motor 126.
Motor 126, which may be a stepper motor, is fixed against movement in a suitable mounting structure 129 moulded integrally on the underside of a circular support plate 128 that has an annular skirt 125 on its bottom facing side.
Circular support plate 128 can be made from an electrically insulating metal but is preferably made from an electrically insulating, low friction polymer material. As best seen in
It will be immediately appreciated that the chosen arrangement is such that actuation of motor 126, which rotates with circular support plate 128, causes its driven pinion 127 to rotationally move support plate 128 through its interaction with the stationary gear ring 116.
Finally, and again with reference to
The skilled person will appreciate that there are various ways of providing power supply not only to the drives 26, 126 that rotate PCB 20, but, more relevantly, to the PCBAs and all electronic components required for signal generation and transmission. Equally not shown, because these components are well known in the fixed wireless modem design and manufacturing industry, are a non-rotating PCBA for external interface ports of the modem, typically carried at the bottom 14 (or closure 114) of housing 12, 112, with internal flexible power supply and controller cabling trees and management equipment.
In order to detect and know by how much the rotatable internal PCB 20 with its otherwise positionally fixed antenna modules 22b needs to be rotated such that the modem unit is appropriately ‘tuned’ for optimal transceiver performance, the PCBAs incorporate programmed or programmable processors for measuring signal strength from different directions as received by directional antenna elements 22b. The sensor signals are processed by a dedicated controller which is operationally associated with the rotational actuator or motor 26, 126 which is mechanically coupled to PCB 20, thereby enabling selective angular re-orientation of the antenna 22b to point towards the direction with the best measured signal source. The PCBAs can also be fitted with suitable circuitry to monitor signal strength and re-measure if there is a significant change in signal strength or quality, for example if the original signal source has been blocked by something in the surrounding environment. This means that the moveable PCB 20 of the modem 10, 100 is expected to remain stationary during most of its operating life with occasional periods of movement and measurement.
This also means that the design of the thermal mitigation system (or arrangement) 30, 130 needs to be considered when refining the design and placement of the antennas 22b to ensure that the metallic heat management components of system 30, 130 do not prevent the antennas 22b from performing efficiently at the desired frequencies, yet allow the heat generated by the various components of the modem unit 10, 110 such as the mmWave modem chip(s) 22a, to be effectively transferred to an internal heat sink and from there to an external heat radiator which dumps thermal load into the surrounding environment. That is, the antenna elements 22b need to be located on the PCB 20 such that the effective beam of the antenna radiation patterns should not intersect with heat sink and conduction arrangements.
Similarly, as noted above, wireless transmission modems with reverse compatibility which cater for various transmission standards leads to PCBA designs with a large number of components consuming up to 10 W each and creating hot spots on the PCB 20 which produce excess heat which needs to be conducted away from the PCBAs and heat-sensitive ICs, to enable the device to operate effectively up to a maximum (housing inside) operating temperature of +55° C.
Components required to drive 5G antennas have much larger transient power output levels that those used of other (e.g. 3G) antennas, and when taking account of an assumed duty cycle of TX to RX of 15%, this would mean a typical power output of a mmWave modem chip of approx. 18 W. Conventional thermal mitigation strategies and arrangements will not do the ‘cooling job’ appropriately.
Thermal mitigation system 30, 130 employs different components and heat transfer mechanisms to remove heat generated by various electric and electronic components of a PCB antenna arrangement, in particular mmWave antenna signal generation equipment received on the PCB, which is mounted within the water and dust tight housing 12, 112 to allow rotational re-orientation of the directional antenna components, to an internal heat sink within the sealed housing (enclosure), and transfer of heat from the internal heatsink to an external, non-rotating heat transfer radiator.
In the following will be described the various components/constituents of a prototype thermal mitigation system 30 of the invention's embodiment illustrated in
Subsequently, a furthermore elaborate embodiment of a modem 100 with modified thermal load mitigation system 130 will be described with reference to
Having reference to the embodiment of
In a preferred embodiment, the stationary heat sink and radiator arrangement 72, 74 will be manufactured as a single integrally formed component and will particularly advantageously be integrated into top closure element or cap 70 which is used to sealingly close the open top 16 of housing 12. This minimises component count and provides a more efficient heat transfer arrangement, although it is possible and feasible to provide three metallic components that are butted and fastened to each other without air gaps that are detrimental to heat conduction.
Top closure element 70 is manufactured by casting or other suitable metallurgical process (including additive manufacturing techniques) from an aluminium alloy or other metal with good thermal conduction properties and heat transfer coefficient. Top closure 70 is designed with (i) an adequate mass for temporarily storing substantial amounts of heat as continuously generated from heat sources (e.g. 22a) mounted to PCB 20 received within housing 12 as noted above, (ii) a heat transfer/radiation structure 72 which locates outside housing 12 when closure element 70 is mounted to close open top 16 of housing 12, optimised for small air gap conductive, convective and radiant transfer of heat into the surrounding environment of module 10, within an environmental operating range of typically −40° C. to +55° C., for example, and (iii) a stationary heat sink/transfer structure 74 which locates inside the housing 12 when top closure 70 is mounted to housing 12, optimised for small air gap conductive reception of heat from the operationally associated and thermally cooperating rotatable upper heat spreader 60 (as described in more detail below) located within housing 12.
More particularly, as seen in
Integrally with circular base 76, exterior heat transfer/radiation structure 72 consists of concentrically arranged annular rows 78 of radiator pins 80 of suitable number, diameter, height and small spacing from each other for adequate heat transfer/radiation into the surrounding air of the heat load it receives through heat conduction over any given time period from the interior heat sink/transfer structure 74 of top closure 70. A spacing of 1.5 mm between individual pins appears to create a structure of discrete metallic components with which convective heat transfer into the surrounding air is within desired parameters.
Integrally with circular base 76, interior heat sink/transfer structure 74 consists of a number of concentrically arranged annular fins 75 (as best seen in
As can be seen in particular in
The rear heat spreader 40 with parallel fins convectively transfers some of the heat received into the sealed housing 12 cavity (via its fins 42) and minimises hot spots at the locations of individual components on the PCBAs. Simulations have showed that the rear heat spreader 40 needs to have a much smaller width than the internal diameter of hosing 12 to allow adequate convective airflow within housing 12 to transfer some of the thermal load generated.
The rear heat spreader 40 is furthermore also thermally coupled through a central portion of its base plate portion 46 with, and appropriately releasably secured to, a first, generally upright orientated, flat sectioned heat pipe 50 whose upper terminal end 51 is bent at 90° to extend about parallel with the top end wall portion 44 of heat spreader 40.
A second, generally horizontally orientated, flat-sectioned heat pipe 52 having a greater width than heat pipe 40 is thermally coupled with and appropriately releasably secured to the outside of common top wall portion 44 of rear heat spreader 40, to remove heat from spreader 40 through heat conduction into horizontal heat pipe 52
The second, horizontally extending heat pipe 52 has a width that is greater than the first heat pipe 50 and about the same as the width of finned rear heat spreader 40. It is releasably secured to the bent portion 51 of first heat pipe 50 on a bottom-oriented face thereof, and on its top oriented face to the underside of the essentially squat-cylindrically shaped upper heat spreader 60.
The upright heat pipe 50 is thermally coupled and releasably secured to the rear side/face of PCB 20 to lie above the more energy-consuming, and therefore hotter, heat generating electronic components of the PCBA (in particular the mmWave modem chip 22a). Relevantly, whilst in thermal contact with and secured to the PCB 20, vertical heat pipe 50 (but also horizontal heat pipe 52) is electrically isolated from the PCB and the PCBAs.
The heat pipes 50, 52 are custom-developed alcohol-filled, formed copper heat pipes to conduct heat away from the hot spots on the PCBAs. Alcohol-filled heat pipes are specified to meet the minimum operating temperature requirement of −40° C. without freezing.
It has been found that such heat pipes 50, 52 are most effective when drawing heat upward from a heat source. Consequently, from a heat transfer management perspective, the stationary heat sink and radiator arrangement 72, 74 is advantageously placed at the top of the modem housing 12, and preferentially made integrally with closure cap 70, whilst side-wise located external radiator structures like known in the prior art, are not believed to be at all viable or at least less viable for removing the heat which in particular is generated by mmWave signal generators received within small format modem housings, as is the case here.
As has been noted, cylindrically-squat shaped upper heat spreader 60 is designed to have freedom of rotation relative to and within housing 12 and the co-operating stationary inner heat sink/transfer structure 74 of the combined heat sink and radiator arrangement provided at the top of housing 12. Its upward facing side is cast with concentric annular fins 62 that mesh with the set of annular fins 75 on the downward-facing side of the heat sink 74. This allows for a high surface area, which increases heat transfer, and enables rotation around the central axis with a narrow air gap between the moving and stationary parts.
Relevantly, as noted, upper heat spreader 60 is secured against rotation to the PCB 20. This can be effected using mounting clamps or other mechanical (or adhesive) fasteners, not shown in the figures.
Although air is usually viewed as an insulator when planning heat management, this design makes use of an air gap because there is a risk that any low-viscosity thermal interface material (fluid) could seize at low temperature or degrade over time with the fluctuations in temperature expected during normal operation. The width of the air gap can be selected based on the required heat transfer efficiency and manufacturing machining tolerances. A possible iteration uses a 1.5 mm gap between the surfaces of the concentric fins, which has been chosen for ease of manufacturing to the required tolerances. This leads to a 10 degree difference in temperature between the upper heat spreader and external heat sink at an ambient temperature of +55 degrees Celsius. If a 0.5 mm gap were used the resulting temperature difference would be 5 degrees.
The heat spreaders and heat sinks 40, 60, 72/74 can be made from die-cast aluminium. The external surfaces of the heat sinks could be coated with a corrosion-resistant finish such as Dacromet, which does not impact the thermal properties of the underlying material.
Turning then to the modem embodiment illustrated in
The stationary upper heat sink and radiator arrangement 172, 174 is in this embodiment also manufactured as a single integrally formed component and particularly advantageously unitary with top closure element or cap 170 which is used to sealingly close the open top 116 of housing 112. The cap 170 here comprises a housing-facing annular skirt 171 that is internally threaded for cooperating with an externally threaded terminal annular top rim 113 of housing 112 to seal-off module 100. However, instead of comprising a plurality of heat radiating pins 80, the housing-external radiator structure 172 consists of a plurality of radially extending upright fins 180 that converge towards the longitudinal axis of housing 112. Interleaving with fins 180 that have a radial extension such as to terminate closer to a central cylindrical void defined by the radially inner ends of the fins 180, are a plurality of radially shorter fins to maximise fin density when packed into a radially converging convective heat radiating array or structure.
As may be seen from
It will be further seen that rather than having a finned heat spreader block 40 as illustrated in
It will also be noted that a separate metallic circular top plate 144 is soldered or otherwise secured for gap-free thermal conduction to the top terminal face of block 140, rather than being made integral with the latter, as was the case with the finned heat spreader block 40. Top plate 144 is provided with semi-circular channels which accommodate the horizontally bent upper terminal ends 151 of heat pipes 150 in similar fashion as previously described. That is, in comparing the heat transfer systems 30 and 130, with the exception of providing for convective heat transfer via fins into the inside of housing 112, heat spreader block 140 together with top plate 144 perform the same heat conduction functionality towards the rotatable upper heat spreader 160 as block 40 but with less convective heat radiation surface area present within the housing 112.
The upper second heat transfer pipe 52 of the module embodiment of
Thermal pad 152 is devised as a surge barrier, ie a member to electrically isolate the rotatable heat transfer components of system 130 from the upper, fixed heat sink body 174.
Finally, and best seen by comparing
In the examples shown in
By changing the height of each ring, or by changing the height of individual fins, the heat transfer and convective heat dispersion into the surrounding air from the heat transfer/radiation structure can be optimised. Computer simulations have been conducted on each of the arrangements shown in
The skilled person will appreciate that variations of the two embodiments described and illustrated are possible without departing from the inventive gist. For example, the housing 12, 112 need not be cylindrical, and ways of securing the top closure 70, 170, with its heat transfer constituent parts 72, 74, other than through a screw-cap type mechanism, are equally possible.
Turning lastly to
The modem/router module 100 can be releasably secured to a top terminal end of vertical pole 190 by clamping movable clamping plate 194 against a stationary clamping plate 196 that is integrally formed with the bottom cap member 114′, with pole 190 between these clamping plates 194, 196, using a pair of clamping bolts 198 that when fastened/loosened cause displacement of movable clamping plate 194 to/from fixed clamping plate 196.
Clamping plates 194, 196 have contoured main plate portions 199 with reinforcing ribs 197 for increased rigidity and stability when the two clamping plates are secured to each other and clampingly sandwich the pole 190 there between.
It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.
In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.
Furthermore, relative reference terms such as ‘upper’, ‘lower’, ‘radially’, ‘axially’, ‘longitudinally’, etc are used herein for convenience in describing components and their relative positioning to each other. These terms should not be viewed as importing an essentiality unless the context dictates otherwise.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020900704 | Mar 2020 | AU | national |
| 2020903220 | Sep 2020 | AU | national |
This application is a continuation application of International Patent Application No. PCT/AU2021/050202 entitled “TELECOMMUNICATIONS HOUSING WITH IMPROVED THERMAL LOAD MANAGEMENT,” filed on Mar. 5, 2021, which claims priority to Australian Patent Application No. 2020903220, filed on Sep. 8, 2020, and Australian Patent Application No. 2020900704, filed on Mar. 6, 2020, each of which are herein incorporated by reference in their entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/AU2021/050202 | Mar 2021 | US |
| Child | 17901187 | US |
