Test fixture for radio frequency chip test

Abstract

The invention discloses a test fixture for radio frequency chip testing, which comprises two SMA connectors, two transmission lines and two bonding wires, and is characterized in that the two SMA connectors are respectively fixed at two ends of a PCB, one ends of the two transmission lines are respectively and correspondingly connected with one SMA connector, the other ends of the two transmission lines are provided with input / output ports, and the bonding wires are connected with the input / output ports. The transmission line and the RFIC chip are respectively connected by the two bonding wires; wherein the transmission line is of an integrally-formed structure and comprises a main body, a first connector and a second connector, the two ends of the main body are connected with the first connector and the second connector respectively, the second connector is further connected with a conductor of the SMA connector, the first connector is connected with the output port or the input port, and the second connector is connected with the output port or the input port. The width of the first connector is smaller than that of the output port or the input port and larger than that of the main body. According to the test fixture, the loss and mismatch between the transmission line and the chip are reduced, the loss and mismatch between the SMA connector and the transmission line are also reduced, and the test precision of the radio frequency chip is improved.

Description

Technical Field

[0001] The invention relates to the field of radio frequency and microwave, and more specifically to a test fixture for testing radio frequency chips. Background Art

[0002] A mature RF chip needs to go through multiple testing steps during the development process, mainly including three categories: functional testing, process screening testing and reliability testing. The accuracy of functional testing plays a vital role in the successful design of a high-performance RF chip. Usually, in the verification of RF chips, the measurement of test accuracy requires more precise calibration methods and test fixtures with higher test accuracy.

[0003] The test fixture commonly used for RF chip testing can be simplified as follows: Figure 1 As shown, the commonly used test fixture mainly includes an SMA connector 110, a transmission line 120, and a bonding wire 140, wherein two SMA connectors 110 are provided, and the two SMA connectors 110 are respectively fixedly installed at both ends of the PCB board 150, and two transmission lines 120 are also provided, one end of the two transmission lines 120 is connected to the two SMA connectors 110, and the other end thereof is connected to the RFIC chip 130 through the bonding wire 140, so as to fix the RFIC chip 130. In addition, please refer to Figure 2 , Figure 2 for Figure 1 , at the other end of the two transmission lines 120 close to the RFIC chip 130, input / output ports 121 and 122 of the transmission lines 120 are provided, and the input / output ports 121 and 122 of the transmission lines 120 are connected to the input / output ports 131 and 132 of the RFIC chip 130 through the bonding wires 140, thereby realizing the fixation of the RFIC chip 130 and the signal transmission between the chip and the test fixture; wherein the transmission line 120 is a standard 50Ω RF transmission line, and the bonding wire 140 is a gold wire.

[0004] exist Figure 1 and Figure 2 The commonly used test fixture for RF chip testing shown in the figure usually leads to higher insertion loss and return loss in higher microwave frequency bands. The main reasons include impedance mismatch, signal transmission continuity damage, microwave transmission mode change, etc. Figure 1 and Figure 2The test fixture shown usually causes the following mismatches: discontinuity and impedance mismatch between the input / output ports 131, 132 of the RFIC chip 130 and the corresponding input / output ports 121, 122 of the transmission line 120 (wherein, the input port 131 of the RFIC chip 130 corresponds to the output port 121 of the transmission line 120, and the output port 132 of the RFIC chip 130 corresponds to the input port 122 of the transmission line 120). The discontinuity is usually caused by the difference in two dielectric materials and processing techniques in the microwave transmission section. Due to the high performance required by the RFIC chip 130, the impedance of its input / output ports 131, 132 is not the standard 50Ω, so that there is a mismatch between the bonding wire 140 and the input / output ports 121, 122 of the transmission line 120 (because the transmission line is a standard 50Ω). In addition, there are also discontinuities, impedance mismatches, and changes in microwave transmission modes (mode mismatches) between the standard 50Ω transmission line 120 and the SMA adapter 110. The mode mismatch is caused by the fact that the coaxial line of the SMA adapter 110 transmits the TEM mode, while the transmission line 120 transmits the quasi-TEM mode, which will generate other transmission modes at the interface section, thereby causing mode mismatches.

[0005] Therefore, it is necessary to provide an improved test fixture for radio frequency chip testing to improve and overcome the above-mentioned defects. Summary of the invention

[0006] The purpose of the present invention is to provide a test fixture for testing radio frequency chips. The test fixture of the present invention reduces the loss and mismatch between the transmission line and the chip, and also reduces the loss and mismatch between the SMA connector and the transmission line, thereby improving the test accuracy of the radio frequency chip.

[0007] To achieve the above-mentioned purpose, the present invention provides a test fixture for radio frequency chip testing, comprising two SMA connectors, two transmission lines and two bonding wires, the two SMA connectors are respectively fixed at the two ends of a PCB board, one end of the two transmission lines is respectively connected to a SMA connector, the other end of one transmission line is provided with an output port, the other end of the other transmission line is correspondingly provided with an input port, and the two bonding wires respectively connect the output port of the transmission line with the input port of the RFIC chip, and the input port of the transmission line with the output port of the RFIC chip; wherein the transmission line is an integrally formed structure and comprises a main body, a first connector and a second connector, the two ends of the main body are respectively connected to the first connector and the second connector, the second connector is also connected to the conductor of the SMA connector, the first connector is connected to the output port or the input port, and the width of the first connector is smaller than the width of the output port or the input port and larger than the width of the main body.

[0008] Preferably, the first connector includes a first transition portion and a first fixed portion, one end of the first transition portion is connected to the main body, and the other end is connected to the first fixed portion, and the other end of the first fixed portion is connected to the output port or the input port, the width of the first transition portion is greater than or equal to the width of the main body, the width of the first fixed portion is greater than or equal to the width of the first transition portion, and the width of the first fixed portion is less than the width of the input / output port.

[0009] Preferably, the width of the first transition portion increases stepwise from the connection with the main body to the connection with the first fixing portion.

[0010] Preferably, the width of the first fixing portion is the width of a connection between the first transition portion and the first fixing portion.

[0011] Preferably, the second connector includes a second transition portion and a second fixed portion, one end of the second transition portion is connected to the main body, and the other end is connected to the second fixed portion, and the second fixed portion is connected to the conductor of the SMA connector in a fitting manner; the width of the second transition portion is less than or equal to the width of the main body, and the width of the second fixed portion is less than or equal to the width of the second transition portion.

[0012] Preferably, the width of the second transition portion decreases in a stepwise manner from the connection with the main body to the connection with the second fixing portion, and the width of the second fixing portion is the width of the connection between the second transition portion and the second fixing portion.

[0013] Preferably, U-shaped grooves are respectively provided at both ends of the PCB board, and the U-shaped grooves are concave to form an air cavity. The U-shaped grooves are provided at the engagement point between the PCB board and the SMA connector, and are located on both sides of the SMA connector conductor, and the center line of the U-shaped groove coincides with the center line of the SMA connector conductor.

[0014] Preferably, the opening of the U-shaped groove faces the direction of the main body.

[0015] Preferably, the U-shaped groove consists of three interconnected cavities, the first cavity and the second cavity are respectively located on both sides of the SMA connector conductor, and the third cavity connects the first cavity and the second cavity and is perpendicular to the conductor of the SMA connector.

[0016] Preferably, the lengths of the first and second sections of the cavity are less than or equal to the length of the conductor of the SMA connector, and the length of the third section of the cavity is less than the length of the SMA connector.

[0017] Compared with the prior art, the test fixture for radio frequency chip testing of the present invention arranges a first connector with a step-wise change in width at one end of the transmission line, so that the width of the transmission line is continuously stepped close to the input / output port, thereby improving the continuity and impedance mismatch between the input / output port of the transmission line and the input / output port of the RFIC chip; and arranges a second connector with a step-wise change in width at the other end of the transmission line, and arranges a U-shaped groove of an air cavity on the PCB board, which not only improves the continuity and impedance mismatch between the transmission line and the SMA connector, but also improves the performance of the coaxial-microstrip line transition, thereby improving the accuracy of chip testing.

[0018] The present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, which are used to illustrate embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a structural diagram of the usage status of an existing test fixture for testing radio frequency chips in combination with the chip.

[0020] Figure 2 for Figure 1 A partial cross-sectional view of the structure shown.

[0021] Figure 3 The present invention is a structural diagram of the use status of the test fixture for radio frequency chip testing and the chip.

[0022] Figure 4 for Figure 3 A partial enlarged view of the structure shown.

[0023] Figure 5 for Figure 4 Schematic diagram of the partial structure of the transmission line shown.

[0024] Figure 6 A schematic diagram of the three-dimensional structure of an SMA connector fixed on a PCB board.

[0025] Figure 7 It is a schematic diagram of the planar structure in which an SMA connector is fixed on a PCB board and connected to a transmission line.

[0026] Figure 8 for Figure 7 A schematic diagram of the structure of a U-shaped groove opened on a PCB board is shown.

[0027] Fig. 9 This is a comparison diagram of S11 test results between the existing test fixture and the test fixture of the present invention.

[0028] Fig.10 This is a comparison diagram of S22 test results of the existing test fixture and the test fixture of the present invention.

[0029] Fig.11 1 is a comparison diagram of S21 test results of the existing test fixture and the test fixture of the present invention. DETAILED DESCRIPTION

[0030] Embodiments of the present invention are now described with reference to the accompanying drawings, in which similar element numbers represent similar elements. As described above, the present invention provides a test fixture for testing radio frequency chips, which reduces the loss and mismatch between the transmission line and the chip, and also reduces the loss and mismatch between the SMA connector and the transmission line, thereby improving the test accuracy of the radio frequency chip.

[0031] Please refer to Figure 3 , Figure 3 The following is a structural diagram of the use state of the test fixture for testing radio frequency chips of the present invention in combination with the chip. Figure 3 As shown, the test fixture for radio frequency chip testing of the present invention includes two SMA connectors 200 , two transmission lines 300 and two bonding wires 400 . Two SMA connectors 200 are respectively fixed on both ends of the PCB board 600, one end of the two transmission lines 300 is respectively connected to a corresponding SMA connector 200, the other end of one transmission line 200 is provided with an output port 310, and the other end of the other transmission line 200 is correspondingly provided with an input port 310, and two bonding wires 400 respectively connect the output port 310 of the transmission line 200 with the input port 510 of the RFIC chip 500, and the input port 310 of the transmission line 300 with the output port 510 of the RFIC chip 500, and the bonding wires 400 are gold wires to ensure the accuracy of signal transmission; wherein, in the present invention, no distinction is made between the input port and output port of the two transmission lines 300 and the input and output ports of the RFIC chip 500. As is well known, the input and output ports are only defined by the signal flow direction, and there is no difference in the structure of the two, so the two can be interchanged at will without making a specific distinction.

[0032] Please refer to Figure 4The transmission line 300 is an integrally formed structure and includes a main body 320, a first connector 330, and a second connector 340. The two ends of the main body 320 are respectively connected to the first connector 330 and the second connector 340. The second connector 340 is connected to the conductor 210 of the SMA connector 200. The first connector 330 is connected to the output port or the input port 310. The width of the first connector 330 is smaller than the width of the output port 310 or the input port 310 and larger than the width of the main body 320. In the present invention, by providing a first connector 330 on the transmission line 300, and the width of the first connector 330 is between the width of the main body 320 of the transmission line 300 and the width of the input / output port 310, the main body 320 of the transmission line 300 gradually changes to the input / output port 310 through the first connector 330, so that the width of the connection part between the transmission line 300 and the RFIC chip 500 is gradually changed, thereby improving the continuity between the input / output port 310 of the transmission line 300 and the input / output port 510 of the RFIC chip 500, and reducing the impedance mismatch between the input / output port 310 of the transmission line 300 and the input / output port 510 of the RFIC chip 500, and further improving the test accuracy of the RF chip.

[0033] For details, please refer to Figure 5 The first connector 330 of the transmission line 300 includes a first transition portion 331 and a first fixing portion 332; one end of the first transition portion 331 is connected to the main body 320, and the other end is connected to the first fixing portion 332, and the other end of the first fixing portion 331 is connected to the output port or the input port 310; the width of the first transition portion 331 is greater than or equal to the width of the main body 320, the width of the first fixing portion 332 is greater than or equal to the width of the first transition portion 331, and the width of the first fixing portion 332 is less than the width of the output / input port 310. Through the above design, the width of the first transition portion 331 is between the width of the main body 320 and the width of the first fixed portion 332. At the same time, the width of the first fixed portion 332 is between the width of the first transition portion 331 and the output / input port 310. Therefore, through the first connector 330, the width of the transmission line 300 gradually increases from the main body 320 and transitions to the output / input port 310, thereby improving the continuity between the input / output port 310 of the transmission line 300 and the input / output port 510 of the RFIC chip 500.

[0034] Furthermore, the width of the first transition portion 331 increases stepwise from the connection with the main body 320 to the connection with the first fixing portion 332; and the width of the first fixing portion 332 is the width of the connection between the first transition portion 331 and the first fixing portion 332; Figure 5 As shown, the minimum width of the first transition portion 331 is the width of the main body 320, and the maximum width is the width of the first fixed portion 332, and the width of the first transition portion 331 increases linearly and stepwise from the minimum width to the maximum width, so that the width of the transition portion 331 continuously increases from the width of the main body 320 to the width of the first fixed portion 332, which greatly improves the connectivity between the transmission line 300 and the RFIC chip 500; at the same time, the width of the first fixed portion 332 is fixed and remains the maximum width of the first transition portion 331, so that the continuity of the first transition portion 331 is directly transferred to the output / input port 310 connected thereto, so as to improve the continuity between the input / output port 310 of the transmission line 300 and the input / output port 510 of the RFIC chip 500.

[0035] Please refer to Figure 4 ,like Figure 4 As shown, the second connector 340 includes a second transition portion 341 and a second fixing portion 342. One end of the second transition portion 341 is connected to the main body 320, and the other end is connected to the second fixing portion 342. The second fixing portion 342 is connected to the conductor 210 of the SMA connector 200 in a fitting manner (such as Figure 4 , Figure 5 ); the width of the second transition portion 341 is less than or equal to the width of the main body 320, and the width of the second fixed portion 342 is less than or equal to the width of the second transition portion 341; specifically, the width of the second transition portion 341 decreases in a step-wise manner from the connection with the main body 320 to the connection with the second fixed portion 342, and the width of the second fixed portion 342 is the width of the connection between the second transition portion 341 and the second fixed portion 342; that is, the width of the second transition portion 341 decreases in a continuous step-wise manner from the connection with the main body 320 to the connection with the second fixed portion 342, and the width of the second fixed portion 342 is fixed to the width of the connection with the second transition portion 341, so as to maintain the continuity of the continuous reduction of the width of the second transition portion 341; to improve the continuity between the transmission line 300 and the conductor 210 of the SMA connector 200.

[0036] Please refer to Figures 6 to 8 , U-shaped grooves 610 are respectively provided at both ends of the PCB board 600, and the U-shaped grooves 610 are concave to form an air cavity. The U-shaped grooves 610 are provided at the position where the PCB board 600 and the SMA connector 200 are engaged (such as Figure 6As shown), and located on both sides of the conductor 210 of the SMA connector 200, the center line of the U-shaped groove 610 coincides with the center line of the conductor 210 of the SMA connector 200 (as shown Figure 7 As shown), that is, the conductor 210 of the SMA connector 200 is located in the middle of the U-shaped groove 610, and the second connector 340 of the transmission line 300 is also located in the middle of the U-shaped groove 610; in the present invention, the U-shaped groove 610 is arranged on the PCB board 600 to form an air cavity, and the arrangement of the air cavity can enable the conductor 210 of the SMA connector 200 and the second connector 340 of the transmission line 300 to achieve good coaxial-microstrip transition performance and reduce the influence of mismatch.

[0037] More specifically, the opening of the U-shaped groove 610 is oriented toward the main body 320 (eg Figure 7 As shown), the U-shaped groove 610 is composed of three sections of interconnected cavities, the first section cavity 611 and the second section cavity 612 are respectively located on both sides of the conductor 210 of the SMA connector 200, and the third section cavity 613 connects the first section cavity 611 and the second section cavity 612 and is perpendicular to the conductor 210 of the SMA connector 200. The specific structure of the U-shaped groove 610 is as shown in FIG. Figure 8 As shown; wherein, the length h1 of the first section cavity 611 and the second section cavity 612 is less than or equal to the length of the conductor 210 of the SMA connector 200 (the length of the conductor 210 of the SMA connector 200 refers to the length of the conductor 200 extending from the SMA connector to the transmission line 300), and the length h2 of the third section cavity 613 is less than the length of the SMA connector 200 (the length of the SMA connector 200 refers to the length of the SMA connector 200 in contact with the PCB board 600); through specific simulation results, it is concluded that the U-shaped groove 610 is arranged as above to better achieve the good performance of the coaxial-microstrip transition and reduce the mismatch effect between the conductor 210 and the transmission line.

[0038] Usually in the field of RF microwaves, S parameters are used as a performance reference for devices and matching circuits. Among the S parameters, S12 is the reverse transmission coefficient, that is, the isolation; S21 is the forward transmission coefficient, that is, the insertion loss (gain); S11 is the input reflection coefficient, that is, the input return loss; S22 is the output reflection coefficient, that is, the output return loss. After determining the matching structure, it is necessary to use professional electromagnetic simulation software to make the final size confirmation to meet S parameters or other performance requirements. Please refer to Figures 9 to 11 , Figure to Fig.11 It is a comparison chart of return loss and insertion loss test results of the existing test fixture and the test fixture of the present invention, wherein curve D0 represents the existing test fixture, and curve D1 represents the test fixture of the present invention. Fig. 9This is a comparison chart of S11 test in the range of 2 to 8 GHz. It can be seen from the figure that compared with D0, the D1 curve has a higher echo at the center frequency of 5 GHz, and D0 deviates from the center frequency by 1 GHz. In addition, within the entire test frequency range, the S11 of D1 is basically maintained below -14dB, which is better than D0. Fig.10 This is a comparison chart of S22 test in the range of 2 to 8 GHz. Fig. 9 The results are similar, and S22 of curve D1 is better than that of curve D0. Fig.11 This is a comparison chart of S21 tests in the range of 2 to 8 GHz. It can be seen from the figure that curve D1 is better than D0 as a whole. In the range of 4 to 5.5 GHz, the S21 of the D1 curve is greater than -0.9dB, which is better than the D0 curve. In addition, at high frequencies, the S21 of the D1 curve is also significantly better than the D0 curve.

[0039] In summary, the test fixture for radio frequency chip testing of the present invention improves the continuity and impedance mismatch between the input / output port 310 of the transmission line 300 and the input / output port 510 of the RFIC chip 500 by setting a first connector 330 with a step-wise width change at one end of the transmission line 300; and by setting a second connector 340 with a step-wise width change at the other end of the transmission line 300 and setting a U-shaped groove 610 of an air cavity on the PCB board 600, not only the continuity and impedance mismatch between the transmission line 300 and the SMA connector 200 are improved, but also the performance of the coaxial-microstrip line transition is improved, thereby improving the accuracy of chip testing.

[0040] The present invention has been described above in conjunction with the best embodiments, but the present invention is not limited to the embodiments disclosed above, but should cover various modifications and equivalent combinations based on the essence of the present invention.

Claims

1. A test fixture for radio frequency chip testing, comprising two SMA connectors, two transmission lines and two bonding wires, wherein the two SMA connectors are respectively fixed at two ends of a PCB board, one end of the two transmission lines is respectively connected to a corresponding SMA connector, the other end of one transmission line is provided with an output port, the other end of the other transmission line is correspondingly provided with an input port, and the two bonding wires respectively connect the output port of the transmission line with the input port of the RFIC chip, and the input port of the transmission line with the output port of the RFIC chip; characterized in that: The transmission line is an integrally formed structure and includes a main body, a first connector, and a second connector. The two ends of the main body are respectively connected to the first connector and the second connector. The second connector is also connected to the conductor of the SMA connector. The first connector is connected to the output port or the input port. The width of the first connector is smaller than the width of the output port or the input port and larger than the width of the main body.

2. The test fixture for radio frequency chip testing according to claim 1, characterized in that: The first connector includes a first transition portion and a first fixed portion, one end of the first transition portion is connected to the main body, and the other end is connected to the first fixed portion, and the other end of the first fixed portion is connected to the output port or the input port, the width of the first transition portion is greater than or equal to the width of the main body, the width of the first fixed portion is greater than or equal to the width of the first transition portion, and the width of the first fixed portion is less than the width of the input / output port.

3. The test fixture for radio frequency chip testing according to claim 2, characterized in that: The width of the first transition portion increases stepwise from the connection with the main body to the connection with the first fixing portion.

4. The test fixture for radio frequency chip testing according to claim 3, characterized in that: The width of the first fixing portion is the width of the connection between the first transition portion and the first fixing portion.

5. The test fixture for radio frequency chip testing according to claim 1, characterized in that: The second connector includes a second transition portion and a second fixed portion, one end of the second transition portion is connected to the main body, and the other end is connected to the second fixed portion, and the second fixed portion is connected to the conductor of the SMA connector in a fitting manner; the width of the second transition portion is less than or equal to the width of the main body, and the width of the second fixed portion is less than or equal to the width of the second transition portion.

6. The test fixture for radio frequency chip testing according to claim 5, characterized in that: The width of the second transition portion decreases stepwise from the connection with the main body to the connection with the second fixing portion, and the width of the second fixing portion is the width of the connection between the second transition portion and the second fixing portion.

7. The test fixture for radio frequency chip testing according to claim 1, characterized in that: A U-shaped groove is respectively provided at both ends of the PCB board, and the U-shaped groove is concave to form an air cavity. The U-shaped groove is provided at the engaging position between the PCB board and the SMA connector, and is located on both sides of the SMA connector conductor, and the center line of the U-shaped groove coincides with the center line of the SMA connector conductor.

8. The test fixture for radio frequency chip testing according to claim 7, characterized in that: The opening of the U-shaped groove faces the direction of the main body.

9. The test fixture for radio frequency chip testing according to claim 8, characterized in that: The U-shaped groove consists of three sections of interconnected cavities, the first section of the cavity and the second section of the cavity are respectively located on both sides of the SMA connector conductor, and the third section of the cavity connects the first section of the cavity and the second section of the cavity and is perpendicular to the conductor of the SMA connector.

10. The test fixture for radio frequency chip testing according to claim 9, characterized in that: The lengths of the first and second sections of the cavity are less than or equal to the length of the conductor of the SMA connector, and the length of the third section of the cavity is less than the length of the SMA connector.

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