Protective shell for radio frequency chip test

Abstract

The utility model provides a protective shell used in a radio frequency chip test. The protective shell comprises a shell body made of an insulating material; the bottom opening of the shell, the top cover and the side wall define a cavity, the opening faces the circuit board to cover the radio frequency chip during testing, and the side wall is in contact with the circuit board; the side wall comprises a first sub-wall and / or a second sub-wall which are / is in contact with the radio frequency transmission line, the first sub-wall is located on the radio frequency signal receiving side of the radio frequency chip, and the second sub-wall is located on the radio frequency signal outputting side of the radio frequency chip; at least one of the first sub-wall and the second sub-wall comprises a contact part in contact with the radio frequency transmission line and paired impedance conversion layers symmetrically arranged on the two sides of the contact part, each impedance conversion layer comprises a hollowed-out area with an opening in the bottom to expose the radio frequency transmission line at the position, and the size of each hollowed-out area meets the following condition that at a set frequency point, the impedance conversion layers are arranged in pairs; the ratio of the impedance of the radio frequency transmission line outside the housing to the impedance of the impedance conversion layer viewed from the outer side surface of the housing is greater than or equal to 95%.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radio frequency, in particular to a protective shell for radio frequency chip testing. BACKGROUND

[0002] For fragile radio frequency devices such as chip dies, bonding wires, chip capacitors and other devices that need to be protected from dust and physical contact, the common practice is to prepare a special protective shell for them. For chip dies, the common permanent protection measure is to package the chip, but for chips used in pure die applications, or for radio frequency devices that will not specially increase the packaging process due to cost factors, the common practice is to use insulating or metal materials to make a protective shell to cover the radio frequency devices that need protection.

[0003] For chips with die-shaped testing requirements in the laboratory, a protective shell is made based on the evaluation board to prevent dirt and accidental contact from damaging the chip and gold wire, and to prevent strong winds during high and low temperature testing from affecting the bonding wire.

[0004] However, the existing protective shell for radio frequency devices has the following problems:

[0005] 1. If the radio frequency signal of the chip is led out through the surface layer transmission line (such as microstrip line, CPWG), a metal protective shell cannot be used because a completely sealed metal protective shell will cause almost complete reflection of the radio frequency signal during surface layer transmission, thus preventing the transmission of the radio frequency signal.

[0006] 2. The protective shell made of insulating material will cause impedance mismatch at the part where the protective shell contacts the radio frequency transmission line because of its own dielectric constant, which will have some impact on the radio frequency signal transmitted on the surface layer, and this impact will worsen as the frequency increases. CONTENT OF THE UTILITY MODEL

[0007] In order to avoid the impedance mismatch caused by the contact between the protective shell and the radio frequency transmission line, the present application proposes a new type of protective shell.

[0008] The protective shell for radio frequency chip testing is suitable for a test circuit board, and the radio frequency chip is placed on the test circuit board during testing. A radio frequency transmission line is arranged on the surface layer of the test circuit board. The protective shell comprises: a shell body made of insulating material, which encloses a cavity for protecting the radio frequency chip; the bottom of the shell body is open, and the top cover and the side wall enclose the cavity. During testing, the opening faces the test circuit board to cover the radio frequency chip, and the side wall is in contact with the test circuit board. The side wall comprises a first sub-wall and / or a second sub-wall in contact with the radio frequency transmission line. The first sub-wall is located on the side of the radio frequency chip receiving the radio frequency signal, and the second sub-wall is located on the side of the radio frequency chip outputting the radio frequency signal. At least one of the first sub-wall and the second sub-wall comprises: a contact part in contact with the radio frequency transmission line, and a pair of impedance transformation layers symmetrically arranged on both sides of the contact part. The impedance transformation layer comprises a hollowed-out area with an open bottom to expose the radio frequency transmission line at the location. The volume of the hollowed-out area satisfies the following condition: at a set frequency point, the ratio of the impedance on the radio frequency transmission line outside the shell to the impedance when looking from the outside of the shell to the impedance transformation layer is greater than or equal to 95%.

[0009] Optionally, the first sub-wall and the second sub-wall each comprise the contact part and the impedance transformation layer.

[0010] Optionally, the first sub-wall and the second sub-wall each have the impedance transformation layer.

[0011] Optionally, the impedance transformation layer is one or more pairs.

[0012] Optionally, the impedance transformation layer is one pair, and the length of the hollowed-out area of the impedance transformation layer is one-quarter of the wavelength of an electromagnetic wave at the frequency point, wherein the length direction is parallel to the radio frequency transmission line, and the wavelength is the wavelength of the center frequency of the working frequency band of the radio frequency chip.

[0013] Optionally, the impedance transformation layer is a plurality of pairs, and the plurality of pairs of impedance transformation layers are a plurality of impedance transformation sections. The length of the hollowed-out area of each impedance transformation layer is one-quarter of the wavelength of an electromagnetic wave at the frequency point, wherein the length direction is parallel to the radio frequency transmission line, and the wavelength is the wavelength of the center frequency of the working frequency band of the radio frequency chip.

[0014] Optionally, the ratio of the impedance on the radio frequency transmission line outside the shell to the impedance when looking from the outside of the shell to the impedance transformation layer is greater than or equal to 99.5%.

[0015] Optionally, the hollowed-out area is any one of a cube, a cuboid, and a semi-cylinder.

[0016] Optionally, the hollowed-out area of the impedance transformation layer has a space shape of a triangular prism, and the top of the triangular prism is located inside the shell.

[0017] Optionally, the radio frequency chip is a bare chip.

[0018] The protective shell for radio frequency devices according to the present application solves the problem of impedance mismatch of the existing protective shell without affecting the sealing property of the protective shell, optimizes the matching of the radio frequency signal path, and makes the optimized radio frequency signal transmission close to the case without the protective shell. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a plan view of the existing insulating protective shell for radio frequency devices.

[0020] Figure 2 is a perspective view of the insulating protective shell for radio frequency devices according to the embodiment of the present application.

[0021] Figure 3 is a plan view of the insulating protective shell for radio frequency devices according to the embodiment of the present application.

[0022] Figure 4 is a principle view of the quarter wavelength impedance transformer according to the embodiment of the present application.

[0023] Figure 5 is a plan view of the insulating protective shell for radio frequency devices according to the embodiment of the present application.

[0024] Figure 6 is a plan view of the insulating protective shell for radio frequency devices according to the embodiment of the present application. DETAILED DESCRIPTION

[0025] For convenience of description, in this document, Z 01 is the equivalent impedance of the radio frequency transmission line in contact with the contact part of the side wall, Z0 is the impedance of the radio frequency transmission line in air, and Z 02 , Z 03 are the equivalent impedances of the radio frequency transmission line under the impedance transformation layer.

[0026] Figure 1is a current commonly used insulating protective shell 101 for radio frequency devices. The radio frequency device and the insulating protective shell 101 are both arranged on a PCB board 102. The radio frequency device includes a chip 103 and a radio frequency transmission line 104. The chip 103 and a part of the radio frequency transmission line 104 are arranged inside a cavity 105 surrounded by the insulating protective shell 101. The radio frequency transmission line 104 contacts the side wall of the insulating protective shell 101 and then enters and exits the cavity 105. Since the insulating protective shell 101 itself has a certain dielectric constant, it will cause impedance mismatch at the contact parts 11, 12 contacting the radio frequency transmission line 104, i.e., the impedance of the radio frequency transmission line outside the insulating protective shell 101 is greatly different from the impedance from the outside to the inside of the insulating protective shell 101, thereby affecting the radio frequency signal transmitted in the radio frequency transmission line 104. That is, at the contact part 11 (i.e., between the reference surface one and the reference surface two) of the radio frequency transmission line contacting the insulating protective shell 101, the impedance is Z 01 , while at the part without contact (i.e., the left side of the reference surface one and the right side of the reference surface two), the impedance is Z0, thereby causing impedance mismatch.

[0027] Therefore, the present application proposes a new protective shell for radio frequency chip testing to eliminate the influence of the insulating protective shell on the transmission of radio frequency signals. Next, the protective shell proposed by the present application is described in detail with reference to the perspective structural view of Figure 2 and the planar structural view of Figure 3 .

[0028] During testing, the radio frequency chip 1 (which can be a bare chip, for example) is placed on a circuit board 2 for testing, and a radio frequency transmission line 3 for transmitting radio frequency signals is arranged on the surface layer of the circuit board 2 and connected to the radio frequency chip 1. The radio frequency chip can be a bare chip, but due to the need for protection against impact, dust, etc., or even considering the overall aesthetics, a sealed shell will be used to package the radio frequency chip.

[0029] The protective shell S mainly includes a shell 4 made of insulating material, which surrounds a cavity 5, and the radio frequency chip 1 is arranged inside the cavity 5 to protect it. The bottom of the shell 4 is provided with an opening, the top is provided with a top cover 6, and the side is provided with a side wall 7, and the top cover 6 and the side wall 7 surround the aforementioned cavity 5. When testing, the opening can be directed towards the protected radio frequency chip 1 to cover the shell 4 of the protective shell S over the radio frequency chip 1, and the side wall 7 contacts the circuit board 2. As shown in Figure 2As shown, the sidewall 7 includes a first sub-wall 71 and a second sub-wall 72 that contact the RF transmission line. The first sub-wall 71 is the signal input side of the RF chip 1, and the second sub-wall 72 is the signal output side of the RF chip 1. However, it is understandable that the signal input and signal output of the RF chip 1 can pass through the same sub-wall, in which case the first and second sub-walls are the same sub-wall; alternatively, only the signal input or signal output of the RF chip 1 may pass through the sub-wall, in which case the sidewall only includes the first or second sub-wall; or the RF chip 1 may have multiple signal inputs and outputs, contacting multiple sidewalls, in which case the first sub-wall 71 and the second sub-wall 72 can belong to multiple sidewalls respectively. Furthermore, the protective shell can also be other shapes, not just... Figure 2 The hexahedral shape shown.

[0030] When the housing 4 covers the RF chip 1, the first sub-wall 71 and / or the second sub-wall 72 will inevitably have contact portions with the RF transmission line 3, dividing the RF transmission line 3 into three parts: one inside the cavity 5, one directly below the first sub-wall 71 / or the second sub-wall 72, and one outside the cavity. Therefore, to avoid impedance mismatch caused by the contact between the first sub-wall 71 or the second sub-wall 72 and the RF transmission line, this application designs the first sub-wall 71 and / or the second sub-wall 72 to include a contact portion and an impedance transformation layer. Since the first sub-wall 71 and the second sub-wall 72 operate on the same principle, the following description will only refer to the first sub-wall 71 and will not be repeated.

[0031] like Figure 3 As shown, the contact portion is in contact with the RF transmission line 3, that is, the part located between reference plane one and reference plane two, and its impedance is Z. 01 Impedance transformation layers are symmetrically arranged on both sides of the contact portion. The bottom of the impedance transformation layers on both sides of the contact portion has identical cutout areas, exposing the RF transmission lines below the cutout areas to the air and preventing them from contacting the impedance transformation layers. The impedance transformation layers are located between reference plane one and reference plane three, and between reference plane two and reference plane four. By adjusting the shape and volume of the cutout areas, the impedance (i.e., the impedance of the RF transmission lines on the outside of the housing) at a set frequency can be adjusted. Figure 3 The impedance Z0 on the left side of reference plane three and the right side of reference plane four is compared with the impedance from the outside of the shell to the impedance transformation layer (i.e., Figure 3 The ratio of the impedance from the left side of reference plane three to the right side of reference plane three is greater than or equal to 95% (i.e., the ratio condition is greater than or equal to 95%).

[0032] Figure 3Only one pair of impedance transformation layers is shown. First, the use of a pair of impedance transformation layers for impedance matching is explained. Specifically, the structure of the impedance transformation layer can be designed using principles such as quarter-wavelength impedance transformation, multi-segment impedance transformation, and tapered impedance transformation. For tapered impedance transformation and multi-segment impedance transformation, the impedance matching effect is broadband. If the RF transmission line contains an impedance matching structure that satisfies the ratio condition greater than or equal to 95%, the overall reflection coefficient of the structure can be kept below -30dB over the broadband. However, for quarter-wavelength impedance matching, the impedance matching effect is narrowband. For impedance matching at the center frequency, the effect worsens with distance. If the ratio condition is still greater than or equal to 95%, the overall reflection coefficient of the structure can be kept below -30dB at the center frequency, but in frequency bands far from the center frequency, the reflection coefficient may not be below -30dB. Therefore, the impedance requirement for quarter-wavelength impedance matching can be defined as a ratio condition greater than or equal to 99.5%.

[0033] First, the design of the impedance transformation layer based on the quarter-wavelength impedance transformation principle is explained, forming a quarter-wavelength impedance transformer. The principle of the quarter-wavelength impedance transformer is as follows: Figure 4 As shown, the impedance between reference plane one and reference plane two is Z. 传 It consists of a quarter-wavelength transmission line. Wherein, Z in Z represents the input impedance as seen from the reference plane along the direction of the arrow (i.e., from left to right). 传 R is the transmission line impedance between reference plane one and reference plane two. L The load impedance at reference plane two is given. The transmission line length between reference plane one and reference plane two is λ / 4, where λ is the wavelength of the electromagnetic wave at the set frequency, and the impedance is Z. 传 A quarter-wavelength transmission line makes Z in The impedance is equal to that on the left side of the reference plane.

[0034] When the load is purely resistive (i.e., the load impedance equals the resistance), Z L =R L When ), we can obtain formula (1):

[0035]

[0036] Where β is the phase constant, β = 2 × pi / λ.

[0037] Based on the above formula Figure 3 In order to achieve impedance matching, the input impedance Z at three points on the reference plane is... in =Z0=Z 02 ×Z 02 / Z 01 Z 01It is known that by adjusting Z 02 Z can be adjusted in Thus, Z in =Z0.

[0038] return Figure 3 As can be seen from the above principle analysis, in order to achieve impedance matching, it is necessary to make... Figure 3 The impedance relationship shown is: Z0 = Z in =Z 02 ×Z 02 / Z 01 After transformation, the impedance calculation formula (2) for the impedance transformation layer can be obtained:

[0039]

[0040] Therefore, it is possible to use formula (2) and based on the known Z 01 The impedance of the impedance transformation layer needs to be designed to the value of Z0. For example, the impedance of the RF transmission line in air is usually Z0 = 50 ohms. Due to contact with the housing, the impedance of the RF transmission line between reference plane one and reference plane two changes from 50 ohms Z0 to 55 ohms Z1. At this time, the shape of the impedance transformation layer between reference plane three and reference plane one (the principle of the impedance transformation layer in reference plane two, reference plane four and another sub-wall is the same) needs to be designed to make the impedance Z0 = 50 ohms Z1 ... 02 =(55×50)^0.5=52.4 ohms, thus Z can be made in =Z0=50 ohm. This means from reference plane five to reference plane three (i.e. Figure 3 The input impedance, viewed from left to right, is 50 ohms. The impedance from reference plane six to reference plane three (i.e.,...) Figure 3 The input impedance viewed from right to left (in the middle) is also 50 ohms. Meanwhile, the input impedance viewed from reference plane two to reference plane six is ​​Z. 02 ×Z 02 / Z0=55 ohms, and the impedance from reference plane one to reference plane two is also 55 ohms. Therefore, the input impedance from reference plane three to reference plane one is Z. 02 ×Z 02 / Z 01 =50 ohms. The input impedance from reference plane five to reference plane three is 50 ohms. That is, the equivalent impedance on both sides of reference plane three and the equivalent impedance on both sides of reference plane four are both equal to 50 ohms. Therefore, the entire RF transmission line after the introduction of the protective shell is still impedance matched.

[0041] The required impedance Z is calculated. 02the value of the impedance, the size and shape of the hollowed-out region can be designed according to the value. First, based on the quarter wavelength impedance transformation principle, the length of the hollowed-out region is the quarter wavelength of the electromagnetic wave at the selected frequency point, the length direction is the transmission direction of the radio frequency signal, and is parallel to the radio frequency transmission line, and in Figure 3 the distance between the reference surface three and the reference surface one or the distance between the reference surface two and the reference surface four. Second, the shape of the hollowed-out region can include various shapes, such as the easily processed cuboid shape shown in Figure 2 and Figure 3 , or the same easily processed semi-cylindrical shape, as long as the hollowed-out region can ensure that the impedance between each reference surface meets the aforementioned calculated value. For example, in one simulation example, at a transmission frequency of 10 GHz, the wavelength is 19 mm, and the length of the hollowed-out region is 19 / 4 = 4.75 mm. The shape of the hollowed-out region is a cuboid, and the width and height (i.e. the other two size measurement factors of the cuboid in addition to the length direction) are 0.2 mm respectively. According to the simulation results, Z 01 is 46 ohm, and Z 02 is 48 ohm, so that:

[0042]

[0043] , the ratio of 50 ohm to 50.08696 ohm is 99.826%>99.5%, which meets the aforementioned ratio condition, so it can be considered that impedance matching has been achieved.

[0044] Figure 3 The quarter wavelength impedance transformation shown in Figure 5 only includes one pair of impedance transformation layers, and it can be understood that it can also include multiple pairs of impedance transformation layers to achieve impedance matching through the multi-section impedance transformation principle, as shown in Figure 5 . In the example shown, the first sub-wall 51 and the second sub-wall 52 each include two pairs of impedance transformation layers, and the first sub-wall 51 is taken as an example for description. The hollowed-out region between the reference surface one and the reference surface three and the hollowed-out region between the reference surface two and the reference surface four constitute the first pair of impedance transformation layers, and the hollowed-out region between the reference surface three and the reference surface five and the hollowed-out region between the reference surface four and the reference surface six constitute the second pair of impedance transformation layers.

[0045] In the multi-section impedance transformation, the length of each section is still the quarter wavelength, that is, the length of each hollowed-out region is still the quarter wavelength, and the impedance of each section can be obtained through the table lookup method, such as the binomial transformer design table shown in Table 1.

[0046]

[0047] In Table 1, N is the logarithm of the impedance transformation layer, and for Figure 5In the illustrated example, N = 2. Z L is the impedance of the RF transmission line portion in contact with the contact portion, i.e. Figure 5 is the Z between reference surface one and reference surface two in the middle 01 , Z1 is the impedance of the pair of impedance transformation layers farthest from the contact portion between reference surface one and reference surface two, i.e. Figure 5 is the Z between reference surface five and reference surface three and between reference surface four and reference surface six in the middle 03 ; Z2 is the impedance of the pair of impedance transformation layers closer to the contact portion relative to the impedance transformation layer with impedance Z1, i.e. Figure 5 is the Z between reference surface one and reference surface three and between reference surface four and reference surface two in the middle 02 , Z3 and so on. In one example, Z0 = 50 ohm, Z 01 = 75 ohm, since Z 01 / Z0 = Z L / Z 0= 75 / 50 = 1.5, then by looking up Table 1, Z 03 = Z0 x 1.1067 = 55.335 ohm, Z 02 = Z0 x 1.3554 = 67.77 ohm. Thus, the appropriate shape of the impedance transformation layers can be further obtained by simulation. It can be appreciated that more sections can be included in the multi-section impedance transformation, i.e. more pairs of impedance transformation layers can be provided, rather than just the two pairs of impedance transformation layers as shown in Figure 5 . The binomial transformer design table shown in Table 1 can make the reflection coefficient curve after impedance matching the flattest. In addition, the impedance values required for each section in the multi-section impedance transformation can be obtained by looking up the Chebyshev transformer design table, so that the bandwidth that can be matched is maximized.

[0048] It can be appreciated that for the impedance transformation layers designed according to the quarter wavelength impedance transformation and multi-section impedance transformation principles, the hollowed-out regions can be various, including the cuboid-shaped hollowed-out regions shown in Figure 3 and Figure 5 , as well as square-shaped and other various regular or irregular shapes.

[0049] In addition, the impedance transformation layers can also be designed using the gradual impedance transformation principle. Figure 6The profile of the protective shell designed by using the principle of the gradually changing impedance transformation is shown in the figure, wherein the z axis reflects the height of the hollowed-out area, the x axis reflects the length of the hollowed-out area, and the y axis reflects the width of the hollowed-out area. The hollowed-out area of the impedance transformation layer is a straight triangular prism with a right-angled triangle as the bottom surface. The height of each point on the hypotenuse of the right-angled triangle gradually changes in the z axis direction (i.e., the top of the triangular prism is located on the inner side of the shell of the protective shell), so that the impedance of each point of the impedance transformation layer in the x axis direction can be controlled, thereby making the equivalent impedance of the impedance transformation layer the required impedance value. For example, when the hollowed-out area is a triangular prism and the radio frequency transmission line is a microstrip line, the width of the hollowed-out area (i.e., the parameter perpendicular to the direction of the radio frequency signal transmission, for the triangular prism, the height of the triangular prism) is equal to the width of the radio frequency transmission line; when the radio frequency transmission line is a coplanar waveguide (CPWG), the width is equal to the width of the signal source + twice the spacing. The height h of the triangular prism in the z axis direction changes linearly with the transmission direction x of the radio frequency signal, i.e., h(x) = kx, and the slope k reflects the rate of change of the height h. The value of the slope k needs to satisfy: the impedance corresponding to the reference surface at the x value when the height h is 0 is equal to Z0, the impedance corresponding to the reference surface at the x value when the height h reaches the maximum value is approximately equal to Z0, i.e., the impedance between the reference surface two and the reference surface three is Z0, the impedance between the reference surface one and the reference surface two is the impedance Z of the impedance transformation layer, and the impedance on the left side of the reference surface one is Z0. Thus, impedance matching is achieved. By determining the height and length of the hollowed-out area, Z0 at the reference surface one and Z0 at the reference surface two can be achieved, i.e., the ratio of the height to the length is determined as the slope k. It should be noted that when the height reaches a certain degree, the hollowed-out area can be considered to have no effect on the characteristic impedance of the transmission line. 01 01 02 02 02 01

[0050] The impedance transformation layer designed by using the principle of the gradually changing impedance transformation can make the impedance of the impedance transformation layer approximately exponentially change, and the processing is relatively simple. In a simulation example, at a transmission frequency of 10 GHz, the wavelength is 19 mm, the length of the hollowed-out area is 19 / 4 = 4.75 mm, the width is 0.2 mm, and the height gradually decreases from 0.2 mm to 0 mm along the x axis, i.e., the value of the hollowed-out area in the x axis is 4.75 mm, the width of the extension in the y axis is 0.2 mm, and the height value in the z axis changes from 0.2 to 0 as the value of the x axis changes from 0 to 4.75. Impedance matching can be achieved, and the impedance transformation layer of the hollowed-out area on the other side of the contact part and the other sub-wall is the same, and thus is not described herein.

[0051] ​​​​​​It is understood that for a gradual impedance transformation, the length of the hollowed-out region of the impedance transformation layer does not have to be equal to a quarter wavelength length, and is most preferably greater than a half wavelength length. In addition, the shape of the hollowed-out region can be any regular or irregular shape, as long as the equivalent impedance of the hollowed-out region is the desired impedance value.

[0052] The foregoing description of the exemplary embodiments of this application has been presented for the purposes of illustration and description. It is readily apparent to those skilled in the art that various other modifications can be made within the scope of the application. Although the description has been presented in connection with the preferred embodiments, it is not intended to limit the scope of the application as defined in the appended claims and their equivalents. Additionally, although a specific implementation has been described, this implementation is meant to be illustrative only and changes can be made in the implementation without departing from the scope of the application. Furthermore, some of the specific details of the described implementation have not been discussed in order not to obscure the description.

[0053] Moreover, various operations will be described as multiple discrete operations, however, the order of description is not intended to imply that these operations are order dependent. In particular, unless specifically stated, the operations can occur in any order and be performed concurrently.

[0054] The terms "comprise", "have" and "include" are synonymous, unless the context dictates otherwise. The phrase "A / B" means "A or B". The phrase "A and / or B" means "(A and B) or (A or B)".

[0055] As used herein, the terms "module" or "unit" can refer to, be or include an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor and / or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality.

[0056] In the drawings, some of the structural or methodological features are shown in certain arrangements and / or orders. It should be understood, however, that such specific arrangements and / or orders can not be required. In some embodiments, the features can be arranged differently than shown in the illustrative figures. Also, inclusion of a structural or methodological feature in a particular figure does not imply that such feature is required in all embodiments, and in some embodiments, the features can not be included or can be combined with other features.

[0057] It should be understood that, although the terms "first", "second" or the like can be used herein to describe various elements or data, these elements or data should not be limited by these terms. These terms are only used to distinguish one feature from another. For example, a first feature could be termed a second feature, and, similarly, a second feature could be termed a first feature, without departing from the scope of the example embodiments.

[0058] It should be noted that in this specification similar references and letter designations refer to similar items throughout the several views, and that numbering might be repeated in the several views, and that similar references and letter designations do not necessarily refer to the same item in all the several views.

[0059] While the present application has been illustrated and described in connection with certain preferred embodiments thereof, it will be readily apparent to those of ordinary skill in the art that various changes in form and detail can be made therein without departing from the spirit and scope of the application.

Claims

1. A protective case for radio frequency chip testing, adapted to a test circuit board on which the radio frequency chip is placed during testing, a surface layer of the circuit board being provided with a radio frequency transmission line, characterized in that The protective shell comprises: a shell of insulating material enclosing a cavity for protecting the radio frequency chip; the shell has an open bottom, a top cover and a side wall enclosing the cavity, the opening faces the circuit board to cover the radio frequency chip during testing, and the side wall is in contact with the circuit board; the side wall comprises a first sub-wall and / or a second sub-wall in contact with the radio frequency transmission line, the first sub-wall is located on the side of the radio frequency chip receiving radio frequency signals, and the second sub-wall is located on the side of the radio frequency chip outputting radio frequency signals; at least one of the first sub-wall and the second sub-wall comprises: a contact portion in contact with the radio frequency transmission line, a pair of impedance transformation layers symmetrically arranged on both sides of the contact portion, the impedance transformation layer comprises a hollowed-out area with an open bottom to expose the radio frequency transmission line at the location, and the volume of the hollowed-out area satisfies the following condition: the ratio of the impedance on the radio frequency transmission line outside the shell to the impedance when looking at the impedance transformation layer from the outside of the shell is greater than or equal to 95% at a set frequency point.

2. The protective case of claim 1, wherein, Both the first sub-wall and the second sub-wall comprise the contact portion and the impedance transformation layer.

3. The protective case of claim 1, wherein, Both the first sub-wall and the second sub-wall have the impedance transformation layer.

4. The protective case of claim 1, wherein, The impedance transformation layer is one or more pairs.

5. The protective case of claim 1, wherein, The impedance transformation layer is a pair, and the length of the hollowed-out area of the impedance transformation layer is one-quarter of the wavelength of the electromagnetic wave at the frequency point, wherein the length direction is parallel to the radio frequency transmission line, and the wavelength is the wavelength of the center frequency of the working frequency band of the radio frequency chip.

6. The protective case of claim 1, wherein, The impedance transformation layer is a plurality of pairs, and the plurality of pairs of impedance transformation layers are a plurality of impedance transformation sections, and the length of the hollowed-out area of each impedance transformation layer is one-quarter of the wavelength of the electromagnetic wave at the frequency point, wherein the length direction is parallel to the radio frequency transmission line, and the wavelength is the wavelength of the center frequency of the working frequency band of the radio frequency chip.

7. The protective case of claim 5 or 6, wherein, The ratio of the impedance on the radio frequency transmission line outside the shell to the impedance when looking at the impedance transformation layer from the outside of the shell is greater than or equal to 99.5%.

8. The protective case of claim 5 or 6, wherein, The hollowed-out area is any one of a cube, a cuboid, and a semi-cylinder.

9. The protective case of claim 1, wherein, The space shape of the hollowed-out area of the impedance transformation layer is a triangular prism, and the top of the triangular prism is located inside the shell.

10. The protective case of claim 1, wherein, The radio frequency chip is a bare chip.

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