Projection device

Abstract

The application discloses a projection device, which comprises a first circuit board, a second circuit board, a first connector, a transmission line and a second connector. The transmission line is used for connecting the first connector on the first circuit board and the second connector on the second circuit board. The transmission line comprises a flexible flat cable and an impedance matching film covering at least one surface of the flexible flat cable. Because the thickness of the impedance matching film covering different areas of the flexible flat cable is different, a new impedance discontinuity point can be formed on the flexible flat cable, and the width of a resonant cavity formed on the flexible flat cable is adjusted. Thus, the interference and suppression of the resonant cavity formed by the impedance discontinuity point on the flexible flat cable in the signal transmission process can be reduced, and the reliability of the signal transmission is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of projection display, in particular to a projection device. BACKGROUND

[0002] The projection device generally includes multiple circuit boards, for example, can include a main board for receiving a video signal, and a display board for controlling the projection device to project a projection image based on the video signal.

[0003] In the related art, in order to reduce the volume of the projection device to achieve the miniaturization requirement of the projection device, the multiple circuit boards in the projection device are generally stacked. Among them, a connector is arranged on each circuit board, and the connector on each circuit board can be connected with the connector on another circuit board through a transmission line. Thus, the transmission of signals (such as video signals) between two circuit boards can be realized.

[0004] However, since the impedances of the connectors of the two circuit boards cannot be completely matched, the reliability of the transmission signal is low. SUMMARY

[0005] The present application provides a projection device, which can solve the problem of low reliability of signal transmission in the related art. The technical solution is as follows:

[0006] On the one hand, a projection device is provided, which includes a first circuit board, a second circuit board, a first connector, a transmission line and a second connector.

[0007] The first connector is located on the first circuit board and connected with one end of the transmission line, and the second connector is located on the second circuit board and connected with the other end of the transmission line.

[0008] The transmission line includes a flexible flat cable and an impedance matching film covering at least one surface of the flexible flat cable, and the thickness of the impedance matching film covered by different regions of the flexible flat cable is different.

[0009] On the other hand, a projection device is provided, which includes a first circuit board, a second circuit board, a third circuit board, a first connector, a second connector, a transmission line and a ground wire.

[0010] The first connector, the second connector, the transmission line and the ground wire are all located on the third circuit board, and the first connector is respectively connected with the first circuit board, one end of the transmission line and one end of the ground wire, and the second connector is respectively connected with the second circuit board, the other end of the transmission line and the other end of the ground wire.

[0011] The transmission line and the ground line are arranged along a first direction, and the transmission line has a target region, and a distance between the target region and the ground line is smaller than a distance between the ground line and other regions of the transmission line except the target region.

[0012] The technical scheme provided by the present application has at least the following beneficial effects:

[0013] The present application provides a projection device, which comprises a first circuit board, a second circuit board, a first connector, a transmission line and a second connector. The transmission line is used to connect the first connector on the first circuit board and the second connector on the second circuit board. The transmission line comprises a flexible flat cable and an impedance matching film covering at least one surface of the flexible flat cable. Because the thickness of the impedance matching film covering different regions of the flexible flat cable is different, a new impedance discontinuity point can be formed on the flexible flat cable, and the width of the resonant cavity formed on the flexible flat cable can be adjusted. Thus, the interference and suppression of the resonant cavity formed by the impedance discontinuity point on the flexible flat cable in the signal transmission process can be reduced, and the reliability of the signal transmission can be ensured. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical schemes in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0015] Figure 1 is a schematic diagram of the change of characteristic impedance in a signal transmission process provided by an embodiment of the present application;

[0016] Figure 2 is a schematic diagram of the structure of a projection device provided by an embodiment of the present application;

[0017] Figure 3 is a schematic diagram of the cross section of a transmission line provided by an embodiment of the present application;

[0018] Figure 4 is a schematic diagram of the first surface of a transmission line provided by an embodiment of the present application;

[0019] Figure 5 is a schematic diagram of the cross section of another transmission line provided by an embodiment of the present application;

[0020] Figure 6 is a schematic diagram of the cross section of another transmission line provided by an embodiment of the present application;

[0021] Figure 7is a schematic diagram of a cross section of another transmission line provided by an embodiment of the present application;

[0022] Figure 8 is a schematic diagram of a structure of a transmission line provided by an embodiment of the present application;

[0023] Figure 9 is a schematic diagram of a cross section of another transmission line provided by an embodiment of the present application;

[0024] Figure 10 is a schematic diagram of a structure of another projection device provided by an embodiment of the present application;

[0025] Figure 11 is a schematic diagram of a structure of a third circuit board provided by an embodiment of the present application;

[0026] Figure 12 is a schematic diagram of a structure of another third circuit board provided by an embodiment of the present application. DETAILED DESCRIPTION

[0027] In order to make the objects, technical solutions and advantages of the present application clearer, the following will further describe the embodiments of the present application in detail with reference to the accompanying drawings.

[0028] In the field of projection display technology, with the continuous improvement of video resolution, the clock frequency (i.e. signal frequency) in the process of video signal transmission is also gradually improved. For example, when a laser projection device (i.e. laser television) transmits a video signal of 4K resolution (4K Resolution) using the V-by-one protocol of high-definition digital display interface, the clock frequency of the video signal can reach 2.97 GHz. It can be understood that when the frequency of the video signal reaches 1 GHz or above, the multipath transmission of video signals of different frequencies in the fading channel will produce inter symbol interference (ISI), which in turn causes the video signal received by the receiving end of the video signal to have error code, thereby affecting the reliability of the video signal transmission.

[0029] In the related art, in order to ensure the reliable transmission of the video signal, the sending end of the video signal can perform pre-emphasis or de-emphasis processing on the video signal to be sent, and the receiving end of the video signal can perform channel estimation and channel equalization processing. Channel equalization refers to compensating for the characteristics of the channel or the entire video signal transmission system. Based on the constant or variable characteristics of the channel and the transmission rate of the video signal, the channel equalization processing of the receiving end has multiple implementation manners. Through channel equalization processing, the receiving end of the video signal can eliminate or weaken the inter symbol interference problem caused by the multipath time delay in the transmission of the video signal.

[0030] However, in order to reduce the volume of the projection device and achieve miniaturization of the projection device, the main board for transmitting the video signal and the display board for receiving the video signal are generally stacked in the projection device, and the video signal needs to pass through the connector of the main board, the connector of the display board, the transmission line and the via hole during transmission, thereby causing impedance discontinuity during transmission of the video signal.

[0031] Figure 1 is a schematic diagram of characteristic impedance of the video signal in the related art during transmission of the video signal between the main board and the display board. The horizontal axis represents transmission time of the video signal in picoseconds (ps), and the vertical axis represents the characteristic impedance value of the video signal during transmission in ohms (Ω). Figure 1 Point M1 in corresponds to the connection point of the connector on the main board and the transmission line, and point M2 corresponds to the connection point of the connector on the display board and the transmission line. Referring to Figure 1 It can be seen that, due to the mismatch between the characteristic impedance of the connector itself and the transmission impedance of the transmission line, impedance mutation occurs at points M1 and M2, i.e. impedance discontinuity. The points M1 and M2 can also be referred to as impedance discontinuity points. Thus, the path from the connector of the main board to the connector of the display board forms a resonant cavity, and the width of the resonant cavity is the distance between points M1 and M2. The resonant cavity causes standing waves of the video signal during transmission, thereby causing large channel fading during transmission of the video signal.

[0032] It can be understood that the greater the distance between the points M1 and M2, the stronger the interference and suppression of the resonant cavity on the video signal. When the distance between the two impedance discontinuity points is comparable to the wavelength of the video signal, the multipath interference of the video signal during channel transmission is also more serious, further reducing the reliability of the video signal transmission.

[0033] It can also be understood that, due to the size limitation of the projection device, the adjustment range of the length of the transmission line between the connector of the main board and the connector of the display board is small. Therefore, the distance between the two impedance discontinuity points on the path from the main board to the display board cannot be changed by changing the length of the transmission line (i.e. changing the distance between the two connectors).

[0034] Figure 2 is a structural schematic diagram of a projection device provided by an embodiment of the present application, as Figure 2 indicated, the projection device includes a first circuit board 10, a second circuit board 20, a first connector 30, a transmission line 40 and a second connector 50. The first connector 30 is located on the first circuit board 10 and connected with one end of the transmission line 40. The second connector 50 is located on the second circuit board 20 and connected with the other end of the transmission line 40.

[0035] Figure 3 is a schematic cross-sectional view of a transmission line 40 provided by an embodiment of the present application, Figure 4 is a top view of a first surface S1 of the transmission line 40. As shown in the figure, Figure 3 the transmission line 40 includes a flexible flat cable (FFC) 41 and an impedance matching film 42 covering at least one surface of the FFC 41. The thickness of the impedance matching film 42 covering different regions of the FFC 41 is different.

[0036] As one possible example, the impedance matching film 42 covers all regions of the FFC 41, and the thickness of the impedance matching film 42 covering different regions of the FFC 41 is different.

[0037] As another possible example, the impedance matching film 42 covers some regions of the FFC 41, and some regions of the FFC 41 are not covered by the impedance matching film 42.

[0038] In the embodiment of the present application, the impedance matching film 42 covering the FFC 41 is used for impedance matching of the first connector 30 and the second connector 50 connected to the FFC 41, so as to ensure that the FFC 41 can normally transmit signals.

[0039] It can be understood that the thickness of the medium (for example, the impedance matching film 42 or air) covering the FFC 41 and the dielectric constant of the medium will affect the characteristic impedance value in the signal transmission process. The characteristic impedance value of each region of the FFC 41 is positively related to the thickness of the medium covering the region, and is negatively related to the dielectric constant of the medium covering the region. The dielectric constant of the region of the FFC 41 not covered by the impedance matching film 42 is by default the dielectric constant of air, and the dielectric constant of the air is smaller than the dielectric constant of the impedance matching film 42. If the characteristic impedance values of any two adjacent regions of the FFC 41 are different, then an impedance mutation will occur at the junction of the two regions, that is, the junction of the two regions is an impedance discontinuity point.

[0040] Since the initial positions of the impedance discontinuity points on the FFC 41 are the connection points of the FFC 41 and the first connector 30 (i.e., point M1) and the connection points of the FFC 41 and the second connector 50 (i.e., point M2), the distance between the two impedance discontinuity points is comparable to the wavelength of the signal transmitted in the FFC 41. In the embodiment of the present application, by changing the thickness or the dielectric constant of the medium covering a region of the FFC 41, the characteristic impedance value of the region can be changed. Thus, new impedance discontinuity points can be formed on the FFC 41.

[0041] For example, referring to Figure 3Impedance discontinuities M3 and M4 can be formed at the junction of the first region P1 and the second region P2. Thus, a new resonant cavity can be formed on the flexible flat cable 41. The width of the new resonant cavity is smaller than the width of the resonant cavity formed by the impedance discontinuity M1 at the first connector 30 and the impedance discontinuity M2 at the second connector 50. Moreover, the width of the new resonant cavity formed by the two adjacent impedance discontinuities on the flexible flat cable 41 is also smaller than the wavelength of the signal transmitted in the flexible flat cable 41. Thus, the resonant cavity on the flexible flat cable 41 can effectively reduce the suppression and interference of the signal, and further ensure the reliability of the signal transmission.

[0042] In summary, the projection device provided by the embodiments of the present application includes a first circuit board, a second circuit board, a first connector, a transmission line and a second connector. The transmission line is used to connect the first connector on the first circuit board and the second connector on the second circuit board. The transmission line includes a flexible flat cable and an impedance matching film covering at least one surface of the flexible flat cable. Since the thickness of the impedance matching film covering different regions of the flexible flat cable is different, new impedance discontinuities can be formed on the flexible flat cable, and the width of the resonant cavity formed on the flexible flat cable can be adjusted. Thus, the resonant cavity formed by the impedance discontinuities on the flexible flat cable can reduce the interference and suppression in the signal transmission process, and the reliability of the signal transmission can be ensured.

[0043] Optionally, the impedance matching film 42 can be an aluminum foil Mylar. The aluminum foil Mylar is a substance formed by using a metal aluminum foil as a base material and then combining the aluminum foil with a polyester tape after applying an adhesive.

[0044] As a first possible implementation manner, as shown in Figure 3 The thickness of the impedance matching film 42 on the first region P1 of the first surface S1 is smaller than the thickness of the impedance matching film 42 on the other regions P2 of the first surface S1 except the first region P1. The first region P1 is closer to the first connector 30 and / or the second connector 50 than the other regions P2.

[0045] In the embodiments of the present application, since the characteristic impedance value of each region of the flexible flat cable 41 is positively correlated with the thickness of the impedance matching film 42 covering the region, the characteristic impedance value at the first region P1 of the flexible flat cable 41 is smaller than the characteristic impedance value at the other regions P2 of the first surface S1 except the first region P1. Correspondingly, a new impedance discontinuity can be formed at the junction of the first region P1 and the other regions P2 of the flexible flat cable 41.

[0046] For example, as shown in Figure 3 andFigure 4 As shown, the first region P1 can include two sub-regions, which can be located on both sides of the other region P2. In this way, impedance discontinuities M3 and M4 can be formed on the flexible flat cable 41. Among them, new resonant cavities can be formed between point M1 and point M3, between point M3 and point M4, and between point M4 and point M2. The width of the new resonant cavity is smaller than the width of the resonant cavity formed between point M1 and point M2.

[0047] Alternatively, referring to Figure 5 , the first region P1 can only include one sub-region. As shown in (a) of Figure 5 , the one sub-region can be located at one end of the flexible flat cable 41 close to the first connector 30 (i.e. close to point M1). Alternatively, as shown in (b) of Figure 5 , the one sub-region can be located at one end of the flexible flat cable 41 close to the second connector 50 (i.e. close to point M2).

[0048] Among them, the length of the first region P1 along the extension direction of the flexible flat cable 41 can be a fixed value, i.e. the position of the new impedance discontinuity formed by the flexible flat cable 41 can be a fixed position.

[0049] For example, the new impedance discontinuity can be located at 1 / 4 and / or 3 / 4 of the flexible flat cable 41. Alternatively, the new impedance discontinuity can be located at 1 / 3 and / or 2 / 3 of the flexible flat cable 41. In addition, the thickness of the impedance matching film 42 covering the first region P1 can be determined based on the impedance values of the first connector 30 and the second connector 50. Based on this, the degree of impedance mutation of the new impedance discontinuity can be made closer to the degree of impedance mutation of the impedance discontinuity at the connection between the flexible flat cable 41 and the first connector 30, and the impedance discontinuity at the connection between the flexible flat cable 41 and the second connector 50. In this way, the reliability of the flexible flat cable 41 in transmitting signals can be further ensured.

[0050] Optionally, the other region P2 can include a plurality of first sub-regions, and the first region P1 is located between two adjacent first sub-regions. Alternatively, the first region P1 includes a plurality of second sub-regions, and the first sub-regions and the second sub-regions can be arranged alternately.

[0051] For example, referring to Figure 6 , the other region P2 can include three first sub-regions, and the first region P1 can include two second sub-regions. The three first sub-regions and the two second sub-regions are arranged alternately. For example, the two second sub-regions can be located at 1 / 4 and 3 / 4 of the flexible flat cable 41, respectively. Alternatively, referring to Figure 7In (a) and (b), other regions P2 may include two first sub-regions, and first region P1 may include a second sub-region. This second sub-region is located between the two first sub-regions. For example... Figure 7 As shown in (a), this second sub-region can be located at 1 / 4 of the flexible flat cable 41. Figure 7 As shown in (b), the second sub-region can be located at 3 / 4 of the flexible flat cable 41.

[0052] Optionally, the length of the first region P1 along the extension direction of the flexible flat cable 41 can be relatively short. Correspondingly, the location of the first region P1 can be approximately the location of any newly added impedance discontinuity on the flexible flat cable 41. The length of the first region P1 along the extension direction of the flexible flat cable 41 can be determined based on the duration of the impedance change at the impedance discontinuity M1 and / or, the impedance discontinuity M2, and the signal transmission rate. The thickness of the impedance matching film 42 covering the first region P1 can be determined based on the impedance values ​​of the first connector 30 and the second connector 50. This ensures that the impedance change at the newly added impedance discontinuity is close to the impedance change at the junction of the flexible flat cable 41 and the first connector 30 and the second connector 50.

[0053] As another possible implementation, such as Figure 8 As shown in (a), (b), and (c), the impedance matching membrane 42 may include a first membrane layer 421 and a second membrane layer 422. The first membrane layer 421 covers the first surface S1 of the flexible flat cable 41. The second membrane layer 422 covers a second region P3 on the second surface S2 of the flexible flat cable 41, where the second region P3 is a partial area on the second surface S2. That is, the first membrane layer 421 completely covers the first surface S1 of the flexible flat cable 41, while the second membrane layer 422 only covers a partial area of ​​the second surface S2 of the flexible flat cable 41.

[0054] As the first possible implementation, refer to Figure 9 In (a) and (b), the second side S2 of the flexible flat cable 41 may only be covered with the second membrane layer 422, and the other areas P4 on the second side S2, except for the second region P3, are not covered with membrane layers (i.e., the covering medium is air).

[0055] In the embodiment of the present application, the thickness of the medium (i.e. the first film layer 421) on the first surface S1 of the flexible flat cable 41 is equal. The first film layer 421 is used to provide a fixed transmission impedance for the flexible flat cable 41 to transmit signals. The second region P3 on the second surface S2 is covered with the second film layer 422, and the other regions P4 on the second surface S2 except the second region P3 are not covered with the film layer. Therefore, the characteristic impedance value at each position on the flexible flat cable 41 is determined based on the dielectric constant of the medium covered on the second surface S2 of the flexible flat cable 41. Since the dielectric constant of the impedance matching film 42 is greater than the dielectric constant of air, and the characteristic impedance value at each region on the flexible flat cable 41 is negatively related to the dielectric constant of the medium covered at the region, the characteristic impedance value at the second region P3 on the second surface S2 of the flexible flat cable 41 which is covered with the second film layer 422 is less than the characteristic impedance value at the other regions P4 on the second surface S2 which are covered with the air film layer.

[0056] It can be understood that the second region P3 on the second surface S2 of the flexible flat cable 41 which is covered with the second film layer 422 and the other regions P4 on the second surface S2 which are covered with the air film layer have an impedance mutation at the junction, i.e. a new impedance discontinuity point M5 is formed. The thickness of the second film layer 422 can be determined based on the impedance value of the first connector 30 or the second connector 50. The position of the new impedance discontinuity point M5 can also be a fixed position.

[0057] For example, referring to (a) in FIG. 6, the second region P3 can be located at one end of the flexible flat cable 41 close to the first connector 30. The new impedance discontinuity point M5 can be located at 1 / 4 of the flexible flat cable 41. Alternatively, referring to (b) in FIG. 6, the second region P3 can be located at one end of the flexible flat cable 41 close to the second connector 50. The new impedance discontinuity point M5 can be located at 3 / 4 of the flexible flat cable 41. Figure 9 Figure 9 As a second possible implementation, as shown in (c) in FIG. 6, the impedance matching film 42 can further include a third film layer 423. The third film layer 423 covers a third region P5 on the second surface S2 of the flexible flat cable 41, and the second region P3 and the third region P5 are arranged at two ends of the flexible flat cable 41.

[0058] As a second possible implementation, as shown in (c) in FIG. 6, the impedance matching film 42 can further include a third film layer 423. The third film layer 423 covers a third region P5 on the second surface S2 of the flexible flat cable 41, and the second region P3 and the third region P5 are arranged at two ends of the flexible flat cable 41. Figure 8

[0059] ​​Similar to the first implementation described above, an impedance abrupt change occurs at the boundary between the third region P5 on the second surface S2 of the flexible flat cable 41, where the third film layer 423 is covered, and the other regions P4 on the second surface S2, where the air film layer is covered, forming a new impedance discontinuity point M6. The thickness of the third film layer 423 can be determined based on the impedance value of the first connector 30 or the second connector 50. The location of this new impedance discontinuity point M6 can also be fixed.

[0060] For example, refer to Figure 8 In (c), the second region P3 can be located on the flexible flat cable 41 near the end of the first connector 30, and the third region P5 can be located on the flexible flat cable 41 near the end of the second connector 50. Correspondingly, the new impedance discontinuity point M5 can be located at 1 / 4 of the flexible flat cable 41, and the impedance discontinuity point M6 can be located at 3 / 4 of the flexible flat cable 41. Alternatively, the second region P3 can be located on the flexible flat cable 41 near the end of the second connector 50, and the third region P5 can be located on the flexible flat cable 41 near the end of the first connector 30. Correspondingly, the new impedance discontinuity point M5 can be located at 3 / 4 of the flexible flat cable 41, and the impedance discontinuity point M6 can be located at 1 / 4 of the flexible flat cable 41.

[0061] In summary, this application provides a projection device including a first circuit board, a second circuit board, a first connector, a transmission line, and a second connector. The transmission line connects the first connector located on the first circuit board and the second connector located on the second circuit board. The transmission line includes a flexible flat cable and an impedance matching film covering at least one side of the flexible flat cable. Because the thickness of the impedance matching film covering different areas of the flexible flat cable is different, new impedance discontinuities can be formed on the flexible flat cable, thereby adjusting the width of the resonant cavity formed on the flexible flat cable. This reduces the interference and suppression of the resonant cavity formed by the impedance discontinuities on the flexible flat cable during signal transmission, thus ensuring the reliability of signal transmission.

[0062] Figure 10 This is a schematic diagram of another projection device provided in an embodiment of this application, for reference. Figure 10 The projection device includes: a first circuit board 10, a second circuit board 20, a first connector 30, a transmission line 40, a second connector 50, a third circuit board 60, and a grounding wire 70. Figure 10 (Not shown in the image).

[0063] The first connector 30, the second connector 50, the transmission line 40 and the ground line 70 are all located on the third circuit board 60, and the first connector 30 is connected with the first circuit board 10, one end of the transmission line 40 and one end of the ground line 70 respectively, and the second connector 50 is connected with the second circuit board 20, the other end of the transmission line 40 and the other end of the ground line 70 respectively.

[0064] Figure 11 is a structural schematic diagram of a third circuit board provided by an embodiment of the present application. As shown in the figure, the transmission line 40 and the ground line 70 are arranged along a first direction X, and the transmission line 40 has a target region Z1. The distance between the ground line 70 and the target region Z1 is less than the distance between the ground line 70 and other regions of the transmission line 40 except the target region Z1. Figure 11

[0065] It can be understood that, for the transmission line 40 and the ground line 70 arranged on the third circuit board 60, the distance between each region of the transmission line 40 and the ground line 70 will affect the characteristic impedance value of each region of the transmission line 40. By changing the distance between the transmission line 40 and the ground line 70, i.e. changing the thickness of the medium between the transmission line 40 and the ground line 70, the characteristic impedance value of any region of the transmission line 40 is positively correlated with the distance between the region and the ground line 70.

[0066] In the embodiment of the present application, by making the distance between the ground line 70 and the target region Z1 of the transmission line 40 less than the distance between the ground line 70 and other regions of the transmission line 40 except the target region Z1, the characteristic impedance value of the target region Z1 can be made less than the characteristic impedance value of other regions. Thus, an impedance mutation will occur at the junction of the target region Z1 and other regions, i.e. a new impedance discontinuity point is formed, and a new resonant cavity is formed on the transmission line 40. The width of the new resonant cavity is less than the width of the resonant cavity formed by the impedance discontinuity point at the first connector 30 and the impedance discontinuity point at the second connector 50. Moreover, the width of the new resonant cavity formed by two adjacent impedance discontinuity points on the transmission line 40 is also less than the wavelength of the signal transmitted in the transmission line 40. Thus, the inhibitory and interfering effects of the resonant cavity on the signal on the transmission line 40 can be reduced, and the reliability of signal transmission can be ensured.

[0067] ​In summary, the projection device provided by the embodiments of the present application has the first connector and the second connector connected through the ground line and the transmission line, and the distance between the target region on the ground line and the transmission line and other regions on the ground line and the transmission line except the target region is smaller than the distance between the target region on the ground line and the transmission line and other regions on the ground line and the transmission line except the target region. In this way, the characteristic impedance value of the target region on the transmission line is smaller than the characteristic impedance value of other regions on the transmission line, so that a new impedance discontinuous point is formed at the junction of the target region and other regions, and the width of the resonant cavity formed on the transmission line is adjusted. In this way, the interference and suppression of the resonant cavity formed by the impedance discontinuous point on the transmission line in the signal transmission process can be reduced, so as to ensure the reliability of the signal transmission.

[0068] As a first possible example, refer to Figure 11 The line width of the target region Z1 on the transmission line 40 is larger than the line width of other regions. For example, the target region Z1 protrudes towards the ground line 70 relative to other regions.

[0069] In the embodiments of the present application, when the line width of the target region Z1 on the transmission line 40 is larger than the line width of other regions, the distance between the ground line 70 and the target region Z1 is smaller than the distance between the ground line 70 and other regions on the transmission line 40, in the case that the line width of each region of the ground line 70 is the same. In this way, the characteristic impedance value of the target region Z1 is smaller than the characteristic impedance value of other regions on the transmission line 40, so that a new impedance discontinuous point can be formed on the transmission line 40.

[0070] As a second possible example, refer to Figure 12 The line width of the target region Z1 on the transmission line 40 is equal to the line width of other regions. The line width of the first region Z1’ corresponding to the target region Z1 in the ground line 70 is larger than the line width of the second region corresponding to other regions in the ground line 70. The second region is other regions on the ground line 70 except the first region Z1’. That is, the first region Z1’ in the ground line 70 protrudes towards the transmission line 40 relative to the second region. The first region Z1’ in the ground line 70 corresponding to the target region Z1 is the region where the projection of the target region Z1 on the ground line 70 is located, and the second region in the ground line 70 corresponding to other regions is the region where the projection of other regions on the ground line 70 is located.

[0071] In the embodiments of the present application, when the line width of the first region Z1' corresponding to the target region Z1 in the ground line 70 is greater than the line width of the second region corresponding to other regions in the ground line 70, and the line width of each region of the transmission line 40 is the same, the distance between the first region Z1' and the target region Z1 in the ground line 70 is less than the distance between the second region and other regions in the transmission line 40. Thus, the characteristic impedance value of the target region Z1 can also be less than the characteristic impedance value of other regions in the transmission line 40, thereby forming a new impedance discontinuous point on the transmission line 40.

[0072] Optionally, with reference to Figure 11 and Figure 12 In the above first and second examples, the target region Z1 on the transmission line 40 can include two sub-regions, which can be located on both sides of other regions. Thus, the impedance discontinuous points M7 and M8 can be formed on the flexible flat cable 41. Among them, new resonant cavities are formed between the point M1 and the point M7, between the point M7 and the point M8, and between the point M8 and the point M2. The width of the new resonant cavity is less than the width of the resonant cavity formed between the point M1 and the point M2.

[0073] The length of the two sub-regions included in the target region Z1 along the extension direction of the transmission line 40 can be a fixed value, that is, the position of the new impedance discontinuous point formed by the transmission line 40 can be a fixed position. For example, the new impedance discontinuous point can be located at 1 / 4 and / or 3 / 4 of the transmission line 40. Alternatively, the new impedance discontinuous point can be located at 1 / 3 and / or 2 / 3 of the transmission line 40.

[0074] The line width of the target region Z1 on the transmission line 40, or the line width of the first region Z1' corresponding to the target region Z1 in the ground line 70, can be determined based on the impedance values of the first connector 30 and the second connector 50. Thus, the degree of impedance mutation of the new impedance discontinuous point can be closer to the degree of impedance mutation of the impedance discontinuous point at the connection between the transmission line 40 and the first connector 30, and the impedance discontinuous point at the connection between the transmission line 40 and the second connector 50. Thus, the reliability of the transmission line 40 in transmitting signals can be further ensured.

[0075] Optionally, the third circuit board 60 can be a printed circuit board (PCB) or a flexible printed circuit (FPC) board.

[0076] It can be understood that, since the signals transmitted between the first circuit board 10 and the second circuit board 20 in the projection device are transmitted in the form of differential signals, the transmission line 40 on the third circuit board 60 can be a differential transmission line. Since the first connector 30 and the second connector 50 on the third circuit board 60 each have a plurality of pairs of differential signal interfaces, the first connector 30 can communicate with the second connector 50 through a plurality of pairs of differential transmission lines, that is, the first connector 30 can simultaneously transmit a plurality of pairs of differential signals to the second connector 50. Correspondingly, a plurality of ground lines 70 can be provided between the first connector 30 and the second connector 50, and the plurality of pairs of differential transmission lines can be arranged between adjacent two ground lines 70.

[0077] In summary, the embodiment of the present application provides a projection device, in which a first connector and a second connector are connected through a ground line and a transmission line, and the distance between a target region on the ground line and the transmission line and other regions on the ground line and the transmission line except the target region is smaller than the distance between the target region and the other regions. Thus, the characteristic impedance value of the target region on the transmission line can be smaller than the characteristic impedance value of the other regions on the transmission line except the target region, so that a new impedance discontinuity point is formed at the junction of the target region and the other regions, and the width of the resonant cavity formed on the transmission line is adjusted. Thus, the interference and suppression of the resonant cavity formed by the impedance discontinuity point on the transmission line in the signal transmission process can be reduced, so as to ensure the reliability of the signal transmission.

[0078] It can be understood that, in the present application, the term "at least one side" refers to one side or multiple sides, and the term "multiple sides" refers to two or more sides.

[0079] In the present application, "and / or" means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. The character " / " generally represents an "or" relationship between the front and rear associated objects.

[0080] In the present application, the terms "first", "second", and the like are used to distinguish the same items or similar items with basically the same function, and it should be understood that there is no logical or time sequence dependence between "first", "second", and "nth", and the number and execution order are not limited.

[0081] The above description is only exemplary embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A projection device, characterized in that, The projection device includes: a first circuit board, a second circuit board, a first connector, a transmission line, and a second connector; The first connector is located on the first circuit board and connected to one end of the transmission line; the second connector is located on the second circuit board and connected to the other end of the transmission line. The transmission line includes a flexible flat cable and an impedance matching film covering at least one side of the flexible flat cable, wherein the thickness of the impedance matching film covering different areas of the flexible flat cable is different; the impedance matching film is aluminum foil Mylar. The flexible flat cable has impedance discontinuities at both ends of the impedance matching film, and the flexible flat cable has impedance discontinuities at the junctions where the thicknesses of the impedance matching film are different; in the extension direction of the flexible flat cable, any two adjacent impedance discontinuities form a resonant cavity, and the distance between the two adjacent impedance discontinuities is the width of the formed resonant cavity. The impedance discontinuity at the junction of the different thicknesses of the impedance matching film is located at 1 / 4 and / or 3 / 4 of the flexible flat cable; or, the impedance discontinuity at the junction of the different thicknesses of the impedance matching film is located at 1 / 3 and / or 2 / 3 of the flexible flat cable. The width of the resonant cavity is smaller than the distance between the two ends of the flexible flat cable, and smaller than the wavelength of the signal transmitted in the flat cable.

2. The projection device according to claim 1, characterized in that, The impedance matching film covers the first side of the flexible flat cable, and the thickness of the impedance matching film on the first region of the first side is less than the thickness of the impedance matching film on other regions of the first side besides the first region. The first region is closer to the first connector and / or the second connector than the other regions.

3. The projection device according to claim 2, characterized in that, The first region includes two sub-regions, which are located on either side of the other region.

4. The projection device according to claim 1, characterized in that, The impedance matching membrane includes a first membrane layer and a second membrane layer; The first film layer covers the first side of the flexible flat cable; The second film layer covers a second region on the second surface of the flexible flat cable, and the second region is a portion of the second surface.

5. The projection device according to claim 4, characterized in that, The impedance matching membrane further includes a third membrane layer; The third film layer covers a third region on the second surface of the flexible flat cable, and the second region and the third region are arranged at intervals at both ends of the flexible flat cable.

6. A projection device, characterized in that, The projection device includes: a first circuit board, a second circuit board, a third circuit board, a first connector, a second connector, a transmission line, and a grounding wire; The first connector, the second connector, the transmission line, and the grounding line are all located on the third circuit board, and the first connector is connected to the first circuit board, one end of the transmission line, and one end of the grounding line, respectively. The second connector is connected to the second circuit board, the other end of the transmission line, and the other end of the grounding line, respectively. Wherein, both the transmission line and the grounding line are arranged along a first direction, and the transmission line has a target area, and the distance between the grounding line and the target area is less than the distance between the grounding line and other areas of the transmission line other than the target area; The transmission line has impedance discontinuity points at both ends, and the transmission line has impedance discontinuity points at the intersection of the target region and other regions outside the target region; in the extension direction of the transmission line, any two connected impedance discontinuities form a resonant cavity, and the distance between the two connected impedance discontinuities is the width of the formed resonant cavity. The impedance discontinuity at the boundary between the target region and other regions outside the target region is located at 1 / 4 and / or 3 / 4 of the transmission line; or, the impedance discontinuity at the boundary between the target region and other regions outside the target region is located at 1 / 3 and / or 2 / 3 of the transmission line. The width of the resonant cavity is smaller than the distance between the two ends of the transmission line and smaller than the wavelength of the signal transmitted in the transmission line.

7. The projection device according to claim 6, characterized in that, The linewidth of the target area of ​​the transmission line is greater than the linewidth of other areas of the transmission line.

8. The projection device according to claim 6, characterized in that, The linewidth of the target region of the transmission line is equal to the linewidth of the other regions of the transmission line. The line width of the first region of the grounding wire corresponding to the target region of the transmission line is greater than the line width of the second region of the grounding wire corresponding to other regions of the transmission line.

9. The projection device according to any one of claims 6 to 8, characterized in that, The target area comprises two sub-regions, which are located on either side of the other area.

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