TECHNICAL FIELD

[0001] This disclosure relates to heat sinks.

BACKGROUND

[0002] Cell towers are now a common site in many neighborhoods as they are typically placed in areas where people live and work. Cell towers support not only antennas but also data and signal processing circuitry. For example, it is not uncommon to find radio units attached to the cell tower. This processing circuitry can consume much power and, therefore, experience overheating. Accordingly, it is common to attach heat sinks to this processing circuitry.

SUMMARY

[0003] Certain challenges presently exist. For example, processing units (e.g., a radio unit or other processing unit) installed on a cell tower (or other structure) may be exposed to ambient wind travelling from different directions and at different speeds. When wind travels over a radio unit having a heat sink, cavities between cooling fins of the heat sink may cause a high pitched whistling noise. The frequency of the whistling noise is in a range that is sensitive to human ears.

[0004] We have discovered that the high pitching whistling noise may occur when the vortices from the flow separation of the ambient wind interacts with the cavities between the cooling fins and that when there is a strong symmetry in the heat sink, the whistling noise is amplified as the noise from the cavities interact.

[0005] Accordingly, in one aspect there is provided a heat sink. The heat sink comprises a base having a first major surface, a plurality of projecting members connected to the first major surface of the base and extending away from the first major surface of the base, and a noise reducer for reducing noise caused by wind travelling over the heat sink.

[0006] In another aspect, there is provided a radio unit. The radio unit comprises a transceiver configured to transmit and/or receive signals and a heat sink according to the method discussed above. [0007] In further aspect, there is provided a method of reducing noise caused by wind travelling over a heat sink. The method comprises providing within the heat sink a base having a first major surface and connecting a plurality of projecting members to the first major surface of the base, wherein the plurality of projecting members extend away from the first major surface of the base. The method further comprises including in the heat sink a noise reducer for reducing noise caused by wind travelling over the heat sink.

[0008] Embodiments of this disclosure provide effective ways of reducing noise caused by wind travelling over a heat sink.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments.

[0010] FIG. 1 illustrates whistling effect between fins of a heat sink.

[0011] FIGS. 2A and 2B show a processing unit including a heat sink provided with a noise reducer according to some embodiments.

[0012] FIGS. 3A-3C show cutouts of fins according to some embodiments.

[0013] FIGS. 4A-4B show cutouts of fins according to some embodiments.

[0014] FIG. 5 shows a processing unit including a heat sink provided with a noise reducer according to some embodiments.

[0015] FIG. 6A shows a cutout according to some embodiments.

[0016] FIGS. 6B and 6C show a noise reducing plate according to some embodiments.

[0017] FIG. 7 shows a process according to some embodiments.

DETAIFED DESCRIPTION

[0018] FIG. 1 shows how a whistling noise can be generated in a heat sink 102. As shown in FIG. 1, as wind 104 travels over projecting members 106 and 108 (a.k.a., cooling fins or fins for short) of the heat sink 102, the flow of wind 104 separates over the first and second fins 106 and 108, thereby causing vortices 110. When the vortices 110 hit the second fin 108, pressure fluctuation 112 may be created and if the pressure fluctuation 112 is caused by wind having certain wind speeds, the pressure fluctuation 112 may cause an acoustic feedback loop 114, thereby causing a whistling noise.

[0019] Since there are many different resonant frequency modes of the structure of the heat sink 102, it is not ideal to modify the geometry of the cavities to impact the structural resonance modes to prevent the occurrence of the acoustic feedback loop 114. Instead, it would be more efficient to modify the flow structure of the heat sink 102. Embodiments of this disclosure provide mechanisms for modifying the flow structure of the heat sink 102, thereby effectively reducing the whistling noise.

[0020] FIGS. 2A and 2B show a processing unit 200 according to some embodiments.

The processing unit 200 may include a heat sink 202 which comprises a plurality of fins 206.

The number of the fins may be within a range between 0 and 50 (desirably between 20 and 35). But the number of the fins may vary depending on the size of the heat sink. In the embodiments shown in FIGS. 2 A and 2B, additional structural features such as cutouts are added to the fins 206. These cutouts may serve as a noise reducer. These cutouts introduce flow disturbances to break up the symmetry of the flow separation, thereby producing different flow structure scales. The produced different flow structure scales may reduce the risk of amplification of the acoustic noise inside the heat sink 202.

[0021] The processing unit 200 may be a radio unit and may include additional parts

(e.g., 208). For example, in case the processing unit 200 is a radio unit, the processing unit 200 may include a transceiver 208. The heat sink 202 may be disposed on top of the transceiver 208 and may be configured to increase the heat flow away from the transceiver 208.

[0022] The heat sink 202 may comprise a base 204 and a plurality of fins 206 extending away from the upper surface of the base 204. Even though FIG. 2A shows that the base 204 corresponds to the upper layer of the transceiver 208, the base 204 may be provided as a separate layer that is disposed on top of the transceiver 208.

[0023] FIG. 2B shows details of the fins 206. As shown in FIG. 2B, each of the fins 206 comprises a plurality of protruding portions 210 and a plurality of cutouts 212 each of which is disposed between two protruding portions 210. The number of the fins and/or the number of the protruding portions shown in in the figures are provided for illustration purpose only and do not limit the embodiments of this disclosure in any way.

[0024] FIGS. 3A-3C (each of which is A-A’ view of the heat sink 202 shown in FIG. 2B) show details of the cutouts 212 according to different embodiments.

[0025] FIG. 3 A shows a first fin 302 and a second fin 312 of the heat sink. The fins 302 and 312 are immediately adjacent to each other and a cavity — is formed between the fins 302 and 312. The first fin 302 may comprises a cutout 304 disposed between two protruding portions 306 and 308. Similarly, the second fin 312 may comprise a cutout 314 disposed between two protruding portions 316 and 318. As shown in FIG. 3 A, the cutout 304 of the first fin 302 and the cutout 314 of the second fin 312 may be aligned. By including cutouts in each of the fins, the noise caused by the wind travelling over the heat sink can be reduced.

[0026] FIG. 3B shows the structure of the fins (322 and 332) according to different embodiments. The fins 322 and 332 are immediately adjacent to each other and a cavity — is formed between the fins. Like the fins 302 and 312, the fin 322 may comprises a cutout 324 between two protruding portions 326 and 328. Similarly, the fin 332 may comprise a cutout 334 between two protruding portions 336 and 338. Unlike the cutouts 304 and 314 included in the fins 302 and 312, however, the cutouts 324 and 334 included in the fins 322 and 332 are angled cutouts. Furthermore, unlike the cutouts 304 and 314 (which are aligned), the cutouts 324 and 334 are staggered. More specifically, as shown in FIG. 3B, the cutout 334 partially overlaps both the cutout 324 and the protruding portion 328. Similarly, the cutout 324 partially overlaps both the cutout 334 and the protruding portion 336. The amount of the overlap (O) (shown in FIG. 3B) may be within a range between 0 mm and 20 mm (preferably between 10 mm and 15 mm).

[0027] FIG. 3C shows the structure of the fins (e.g., 342 and 352) according to other embodiments. The fins 342 and 352 are adjacent to each other (among the plurality of fins included in the heat sink). Like the fins 302 and 312, the fin 342 may comprises a cutout 344 disposed between two protruding portions 346 and 348. Similarly, the fin 352 may comprise a cutout 354 disposed between two protruding portions 356 and 358. Furthermore, like the cutouts 324 and 334, the cutouts 344 and 354 are staggered. More specifically, as shown in FIG. 3C, the cutout 344 partially overlaps both the cutout 354 and the protruding portion 356. Similarly, the cutout 354 partially overlaps both the cutout the protruding portion 348 and the cutout 344. [0028] In the embodiments shown in FIGS. 3B and 3C, the tip patterns of the fins are asymmetric (i.e., having the staggered pattern), thereby further breaking up the symmetry of the flow separation. More specifically, the separation between the fins becomes more 3 -dimensional and, thus the feedback loop is not as strong as the feedback loop occurring in the conventional heat sink. Also because, in the embodiments shown in FIGS. 3B and 3C, different areas will have different resonant frequencies, the amplification will not be as strong.

[0029] Even though each of the cutouts shown in FIGS. 3A-3C is symmetric with respect to the center of the width of the cutout, in other embodiments, the cutouts may be asymmetric as shown in FIGS. 4A and 4B. FIG. 4A shows that one side of each of the cutouts is angled while the other side of the cutout is not angled. Similarly, FIG. 4B shows that one side of each of the cutouts is curved while the other side of the cutout is not curved.

[0030] As shown in FIGS. 2A-4, the noise reducer may be implemented by forming a plurality of cutouts at the top portions of the fins included in a heat sink of a processing unit. In different embodiments, however, the noise reducer may be implemented using a component that is not a part of the fins. An example of such component is shown in FIGS. 5-6C.

[0031] FIG. 5 shows a processing unit 500 (e.g., a radio unit) including a heat sink 502 which comprises a plurality of fins 504 and a noise reducer 506. The structure of the heat sink 502 is substantially similar to the structure of the heat sink shown in FIGS. 2A and 2B.

[0032] In the embodiments shown in FIGS. 2B-4, the fins of the heat sink include a plurality of cutouts. On the contrary, as shown in FIG. 6A (which is A-A’ view of the heat sink 502 shown in FIG. 5), the fins 504 of the heat sink 502 does not have any cutouts. Instead, the heat sink 502 comprises the noise reducer 506 (a.k.a., noise reducing plate 506) disposed over the fins 504.

[0033] As shown in FIG. 6B (which is B-B’ view of the heat sink 502 shown in FIG. 5), the noise reducing plate 506 may be attached to the fins 504 of the heat sink 502. Alternatively, as shown in FIG. 6C (which is B-B’ view of the heat sink 502 shown in FIG. 5), the noise reducing plate 506 may float over the fins 504 (but instead may be attached to other component(s) of the processing unit 500). In the embodiments where the noise reducing plate 506 is attached to the fins 504, a soft material (e.g., rubber) may be provided between the noise reducing plate 506 and the fins 504.

[0034] The noise reducing plate 506 is configured to block the ambient wind travelling over the fins 504, thereby stopping the flow separation of the wind over the fins 504.

[0035] The noise reducing plate 506 shown in FIG. 5 comprise a plurality of holes 510 in order to reduce the weight of the noise reducing plate 506. In other embodiments, however, the noise reducing plate 506 may not include any holes.

[0036] Furthermore, even though FIGS. 6B and 6C show that the size of the noise reducing plate 506 is greater than the size of the heat sink 502, in other embodiments, the size of the noise reducing plate 506 may be equal to or less than the size of the heat sink 502.

[0037] FIG. 7 shows a process 700 for reducing noise caused by wind travelling over a heat sink. The process 700 may begin with step s702.

[0038] Step s702 comprises providing a base having a first major surface.

[0039] Step s704 comprises connecting a plurality of projecting members to the first major surface of the base, wherein the plurality of projecting members extend away from the first major surface of the base.

[0040] Step s706 comprises including in the heat sink a noise reducer for reducing noise caused by wind travelling over the heat sink.

[0041] In some embodiments, the noise reducer comprises a top portion of each of the plurality of projecting members, and the top portion of each of the plurality of projecting members comprises a plurality of cutouts.

[0042] In some embodiments, the noise reducer comprises a plate disposed over the plurality of projecting members.

[0043] Summary of Various Embodiments

A1. A heat sink, the heat sink comprising: a base having a first major surface; a plurality of projecting members connected to the first major surface of the base and extending away from the first major surface of the base; and a noise reducer for reducing noise caused by wind travelling over the heat sink. A2. The heat sink of embodiment Al, wherein the noise reducer comprises a top portion of each of the plurality of projecting members, and the top portion of each of the plurality of projecting members comprises a plurality of cutouts.

A3. The heat sink of embodiment A2, wherein at least one of the plurality of cutouts is symmetric with respect to a center axis of the width of said at least one of the plurality of cutouts.

A4. The heat sink of embodiment A2, wherein at least one of the plurality of cutouts is asymmetric with respect to a center axis of the width of said at least one of the plurality of cutouts.

A5. The heat sink of any one of embodiments A2-A4, wherein each of the plurality of cutouts is any one of a single-sided angled cutout, a double-sided angled cutout, a single-sided curved cutout, a double-sided curved cutout, or a mix of a single-sided angled cutout and a single-sided curved cutout.

A6. The heat sink of any one of embodiments A2-A5, wherein the plurality of projecting members include a first projecting member and a second projecting member, the first projecting member comprises a first cutout and a first protruding portion, the first cutout and the first protruding portion are adjacent to each other, the second projecting member comprises a second cutout, the second cutout comprises a first portion and a second portion, the first portion of the second cutout overlaps a portion of the first cutout, and the second portion of the second cutout overlaps a portion of the first protruding portion. A7. The heat sink of embodiment A6, wherein the portion of the first cutout that overlaps the first portion of the second cutout has a length within a range between 10 mm and 20 mm.

A8. The heat sink of any one of embodiments A2-A7, wherein the number of the plurality of projecting members is within a range between 10 and 40.

A9. The heat sink of embodiment Al, wherein the noise reducer comprises a plate disposed over the plurality of projecting members.

A10. The heat sink of embodiment A9, wherein the plate has a plurality of holes.

Al 1. The heat sink of embodiment A9 or A10, wherein the plate lies on a plane that is substantially parallel with the first major surface of the base.

Bl. A radio unit, the radio unit comprising: a transceiver configured to transmit and/or receive signals; and a heat sink according to any one of embodiments Al-Al 1.

Cl . A method of reducing noise caused by wind travelling over a heat sink, the method comprising: providing a base having a first major surface; connecting a plurality of projecting members to the first major surface of the base, wherein the plurality of projecting members extend away from the first major surface of the base; and including in the heat sink a noise reducer for reducing noise caused by wind travelling over the heat sink.

C2. The method of embodiment Cl, wherein the noise reducer comprises a top portion of each of the plurality of projecting members, and the top portion of each of the plurality of projecting members comprises a plurality of cutouts.

C3. The method of embodiment Cl, wherein the noise reducer comprises a plate disposed over the plurality of projecting members.

[0044] Conclusion

[0045] While various embodiments are described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of this disclosure should not be limited by any of the above described exemplary embodiments. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

[0046] Additionally, while the processes described above and illustrated in the drawings are shown as a sequence of steps, this was done solely for the sake of illustration. Accordingly, it is contemplated that some steps may be added, some steps may be omitted, the order of the steps may be re-arranged, and some steps may be performed in parallel.