W-band broadband on-chip reference antenna

Abstract

The invention belongs to the technical field of microwaves, and discloses a W-band broadband on-chip reference antenna. A traditional horn antenna serves as a reference antenna for on-chip antenna gain measurement, and extra measurement errors are introduced when a radio frequency probe and a corresponding waveguide or a coaxial transmission line are replaced. The invention provides an on-chip reference antenna of a W-band SIW-to-RWG transition structure, which is suitable for millimeter wave on-chip antenna measurement and has the advantages of broadband and stable gain, and solves the problems of large error, low efficiency, poor compatibility and the like in the traditional on-chip antenna measurement. On one hand, the single-layer dielectric plate and the metal substrate are combined to form an SIW-to-RWG transition structure, the metal cavity below the substrate and the transmission line type matching structure on the back face are matched, the bandwidth is effectively expanded, the energy transmission efficiency is improved, and on the other hand, linear rising stable gain is achieved through the horn antenna; the structure has the characteristics of simple structure and relatively wide working bandwidth, and can also be used for designing on-chip reference antennas of other frequency bands of millimeter waves.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave technology and antenna measurement, and particularly relates to a W-band broadband on-chip reference antenna with a substrate integrated waveguide-to-rectangular waveguide (SIW-to-RWG) vertical transition structure. BACKGROUND

[0002] Modern communication systems are constantly developing towards higher frequencies, and higher data transmission rates and miniaturization are required. At present, researchers have carried out research on the integration of millimeter wave antennas and radio frequency circuits on silicon substrates, and this integration technology is called antenna on chip (AoC). Unlike off-chip antennas, the measurement of on-chip antennas usually requires the use of radio frequency probes, which brings many challenges to antenna measurement. Almost all components in the wafer probe station, such as clamps, microscopes, positioners, probe stations and probe heads, are sources of electromagnetic field reflection and scattering, resulting in errors in the measurement results. Since all metal parts of the measurement device cannot be covered with absorbers, it is difficult to completely avoid these phenomena. When measuring in a commercially available probe station, the clamp sometimes acts as a ground plane, resulting in unnecessary modes.

[0003] In the process of millimeter wave antenna gain measurement, each component behind the calibration plane needs to accurately obtain the scattering parameter (S parameter) for embedding processing. However, research shows that after calibration, the performance of the antenna is still different from that in the probe-free state, which shows that the probe has an unavoidable impact on the return loss and radiation pattern of the antenna under test.

[0004] Traditional horn antennas as reference antennas for on-chip antenna gain measurement will introduce additional measurement errors when replacing radio frequency probes and corresponding waveguides or coaxial transmission lines, especially in the millimeter wave frequency band. An on-chip reference antenna with the characteristics of low cost, high gain and wide bandwidth is a better choice for an on-chip antenna measurement system. Therefore, replacing the traditional horn antenna with a new type of reference antenna can ensure that the antenna under test (AUT) and the reference antenna are in the same environment, avoid measurement errors caused by the probe environment, improve measurement accuracy and shorten measurement time. SUMMARY

[0005] TECHNICAL PROBLEM

[0006] The purpose of the present application is to provide a wideband, gain-stable W-band on-chip reference antenna suitable for millimeter wave on-chip antenna measurement, to solve the problems of large error, low efficiency and poor compatibility in traditional on-chip antenna measurement. The present application achieves breakthrough through the design of a specific structure: on the one hand, the SIW-to-RWG transition structure is composed of a single-layer dielectric plate and a metal substrate, combined with the metal cavity below the substrate and the back transmission line matching structure, which effectively expands the bandwidth and improves the energy transmission efficiency without increasing the overall structural complexity. Through the replacement design of metal wall and metal via and the electromagnetic coupling mechanism, the TE 10 mode in the transition structure is stably converted, realizing wide bandwidth and linearly rising stable gain; on the other hand, in view of the high cost of millimeter wave frequency probes, a metal pad compatible with the solderless PCB connector and the on-chip measurement platform is designed, which has good impedance matching characteristics and can efficiently couple energy to the transmission line, avoiding errors and cost problems caused by incompatible measurement components.

[0007] Through the improvement of the present application, the limitations of error control difficulty, bandwidth limitation and poor component compatibility in traditional on-chip antenna measurement are overcome, providing a high-precision, high-efficiency measurement reference scheme for millimeter wave on-chip antenna, and providing a new idea for the structural design and functional optimization of on-chip reference antenna.

[0008] Technical scheme:

[0009] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a W-band wideband on-chip reference antenna, comprising a 3D printed metal horn antenna, a single-layer dielectric circuit board and a mechanically processed metal substrate fixedly connected in sequence from top to bottom. The single-layer dielectric circuit board is integrated with a metal pad for connecting a radio frequency probe, a 50-ohm transmission line, a ground coplanar waveguide (GCPW) to substrate integrated waveguide (SIW) transition structure, substrate integrated waveguide, and substrate integrated waveguide (SIW) to rectangular waveguide (RWG) vertical transition structure in sequence from the signal input end to the radiation end. The mechanically processed metal substrate is provided with a metal back cavity and a stepped matching structure inside.

[0010] Further, the key to the design of the SIW-to-RWG vertical transition structure is to achieve optimal energy coupling by adjusting the aperture size of the coupling slot and the geometric parameters of the surface metal patch on the dielectric circuit board, and to optimize the mode matching by adding an inductive metal column below the metal patch, to ensure the stable conversion of TE 10 mode in SIW to TE 10 mode in RWG through electromagnetic coupling, so that the vertical transition structure realizes a return loss of below-10dB within a wide frequency band.

[0011] Further, the metal pad is a 50Ω microstrip line pad, which keeps good impedance matching performance in a wide frequency range by optimizing its geometric parameters; the pad can completely couple energy to the transmission line at the core working frequency, and only when the upper limit of the core frequency band is exceeded, a small amount of surface wave is generated around the pad, thereby avoiding energy loss affecting the measurement accuracy.

[0012] Further, the metal via design of the dielectric circuit board needs to follow a certain ratio, the ratio of the via diameter to the pitch is determined according to the design formula of the substrate integrated waveguide, and the via arrangement is adapted to the SIW width to ensure the electromagnetic shielding effect of the equivalent metal wall and prevent signal leakage.

[0013] Further, the size of the metal back cavity of the machined metal substrate is accurately aligned with the coupling structure on the dielectric circuit board, and the inner wall of the cavity is kept smooth to reduce electromagnetic reflection loss; the height and length of the cavity are determined by simulation optimization combined with bandwidth requirements to effectively expand the working bandwidth of the antenna.

[0014] Further, the gradual change angle and length of the GCPW-to-SIW tapered transition structure are precisely designed to ensure low-loss and low-reflection transmission of radio frequency signals from the coplanar waveguide to the substrate integrated waveguide.

[0015] Further, the assembly of the overall structure of the antenna ensures the coaxiality and flatness of each component; the flange connection between the 3D printed metal horn antenna and the dielectric circuit board is tight, and the machined metal substrate and the circuit board are accurately aligned and fixed through the positioning hole to prevent additional electromagnetic loss caused by mechanical assembly errors.

[0016] Further, the design parameters of the antenna are repeatedly optimized by professional electromagnetic simulation software, and the tolerance of the key dimensions is controlled within a high-precision range to ensure the consistency of the actual performance and the simulation results.

[0017] Further, the manufacturing process of the antenna is selected according to the characteristics of different components: the 3D printed metal horn antenna adopts high-precision metal 3D printing process or CNC machining; the single-layer dielectric circuit board is made of standard PCB material or alumina ceramic thin film circuit process; the machined metal substrate adopts CNC milling process to ensure the accuracy of the cavity; and the components are assembled after being manufactured.

[0018] Beneficial effects:

[0019] Compared with the prior art, the application effectively solves the problems of error caused by changing probes and transmission lines, inconsistent measurement environment, limited bandwidth and the like in the traditional on-chip antenna measurement scheme by innovatively integrating an SIW-to-RWG vertical transition structure, a broadband matching pad, a metal back cavity and a 3D printed horn antenna. The application adopts a single-layer dielectric plate combined with an optimized vertical transition and matching structure, thereby realizing high transmission efficiency, wide working bandwidth and stable gain performance while ensuring simple structure. The broadband pad design compatible with a solderless PCB connector significantly reduces the dependence on expensive millimeter wave probes, saves measurement cost and improves system compatibility. The application has reasonable structure design and conforms to the existing processing technology level, can be used as a standard gain antenna for on-chip antenna measurement, has high engineering practicability and innovation in the fields of millimeter wave communication and on-chip device testing and the like, and can meet the requirements of high-precision and high-efficiency on-chip antenna measurement. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a structure perspective view of an alumina ceramic broadband on-chip reference antenna in the embodiment of the application.

[0021] Figure 2 It is a cross-sectional view showing the vertical transition of a substrate integrated waveguide to a rectangular waveguide in the embodiment of the application.

[0022] Figure 3 It is a schematic view of a metal structure on the back of an alumina ceramic plate in the embodiment of the application.

[0023] Figure 4 It is a top view of a mechanically processed metal substrate in the embodiment of the application.

[0024] Figure 5 It is a schematic view of the electric field distribution when transitioning from a substrate integrated waveguide to a rectangular waveguide at a frequency of 80GHz in the embodiment of the application.

[0025] Figure 6 It is an S parameter simulation curve of the transition from a substrate integrated waveguide to a rectangular waveguide in the embodiment of the application.

[0026] Figure 7 It is a simulation S parameter, gain curve and measured S parameter curve of the on-chip reference antenna in the embodiment of the application.

[0027] Figure 8 It is a normalized radiation pattern of the on-chip reference antenna in the embodiment of the application at frequencies of 70GHz, 80GHz and 90GHz, wherein (a) and (b) are the E-plane and H-plane radiation patterns at the three frequency points, respectively.

[0028] Numerical values in the figure represent:

[0029] 1-non-metal positioning via on ceramic board, 2-pad for connecting RF probe, 3-transmission line composed of microstrip line and grounded coplanar waveguide, 4-transition structure from grounded coplanar waveguide to SIW, 5-3D printed metal horn antenna (including flange), 6-machined metal base, 7-metal back cavity, 8-metal via on ceramic board, 9-gold plated layer on upper and lower surfaces of alumina dielectric layer, 10-alumina dielectric layer, 11-step matching structure in machined metal base, 12-metal patch of SIW to RWG transition structure, 13-via on machined metal base, 14-groove on machined metal base, 15-non-metal screw via on ceramic board, 16-transmission line matching structure on lower surface of ceramic board. DETAILED DESCRIPTION

[0030] The W-band on-chip reference antenna structure of the application includes a 3D printed metal horn antenna, a single-layer dielectric circuit board, a machined metal base, and further integrates a tapered transition structure from GCPW to SIW and a 50 Ω microstrip line pad, and each component is precisely fixed and connected through a non-metal positioning via on the circuit board, a non-metal screw via, and a via on the machined metal base. The whole is used in the millimeter wave on-chip antenna measurement scene and can be used as a standard gain antenna to ensure measurement accuracy and efficiency. The 3D printed metal horn antenna is the core radiation component and is responsible for efficient radiation of electromagnetic signals; the circuit board is a signal transition carrier and realizes vertical signal conversion between substrate integrated waveguide and rectangular waveguide through a metal patch of the SIW to RWG transition structure; the machined metal base is internally provided with a metal back cavity and a step matching structure inside it, which are respectively used for reflecting electromagnetic signals to expand the bandwidth of the antenna and optimize the signal matching performance; the transition structure from GCPW to SIW cooperates with the transmission line to realize low-loss transmission of RF signals from the coplanar waveguide to the substrate integrated waveguide; the pad for connecting the RF probe is compatible with the solderless PCB connector and the on-chip measurement platform to ensure effective transmission of the RF chip output signal.

[0031] The application will be further described below in conjunction with the specific embodiments and the accompanying drawings. It should be noted that the diagrams provided in the embodiments only schematically illustrate the basic concept of the application, and only the components related to the application are shown in the diagrams, not the number, shape and size of the components when actually implemented. The shape, number and proportion of each component when actually implemented can be arbitrarily changed, and the component layout pattern can also be more complex.

[0032] Embodiment 1:

[0033] As Figures 1-8As shown, the embodiment discloses a W-band alumina ceramic chip reference antenna, which comprises a 3D-printed metal horn antenna 5, a single-layer dielectric circuit board (alumina ceramic circuit board composed of an alumina dielectric layer 10 and gold-plated layers 9 on its upper and lower surfaces) and a mechanically processed metal base 6, which are sequentially assembled through a non-metal positioning hole 1 on the ceramic plate, a non-metal screw hole 15 on the ceramic plate and a hole 13 on the mechanically processed metal base, a GCPW to SIW transition structure 4, a microstrip line and a ground coplanar waveguide, and a solder pad 2 connected to a radio frequency probe, which are integrated on the alumina ceramic circuit board, and the whole constitutes a complete on-chip reference antenna system.

[0034] Specifically, as shown in the figure, Figure 1 The flange of the 3D-printed metal horn antenna 5 is fixed to the alumina plate by bolts, and the waveguide interface is precisely aligned with the RWG port on the gold-plated upper and lower surfaces 9 of the alumina ceramic plate; the mechanically processed metal base 6 is located below the alumina ceramic circuit board, the mechanically processed metal base groove 14 is matched with the edge of the alumina ceramic circuit board, the non-metal screw hole 15 on the ceramic plate is matched with the hole 13 on the mechanically processed metal base, and the non-metal positioning hole 1 on the ceramic plate is used for positioning during assembly.

[0035] Specifically, as shown in the figure, Figure 2 The figure is a cross-sectional view of a substrate integrated waveguide vertically transitioning to a rectangular waveguide, the metal holes 8 on the ceramic plate are arranged along the edge of the SIW to form equivalent metal walls to constrain electromagnetic signals; the inner wall of the metal back cavity 7 forms a coupling space with the metal patch 12 of the transition structure; the stepped matching structure 11 in the mechanically processed metal base is located at the bottom of the metal back cavity 7.

[0036] Specifically, as shown in the figure, Figure 3 The figure is a schematic diagram of the metal structure on the back of the alumina ceramic plate, and 16 is the transmission line matching structure on the lower surface of the ceramic plate.

[0037] As an example, the core working frequency band of the W-band on-chip reference antenna covers 70-94GHz, the 3D-printed metal horn antenna is made of aluminum alloy material, the length and aperture of the horn antenna are optimized through radiation performance simulation to ensure that the gain linearly rises within the working frequency band, and the peak gain reaches 18dBi at 94GHz.

[0038] Specifically, 2 is a metal solder pad compatible with a solderless PCB connector and an on-chip measurement platform, the holes around the solder pad are grounded, the mechanically processed metal base is slotted to connect the solderless connector, and the solder pad has good impedance matching characteristics and can efficiently couple energy to the transmission line at less than 110GHz.

[0039] As an example, the thickness of the alumina dielectric layer 10 of the alumina ceramic circuit board is 0.127 mm, the relative dielectric constant is 9.9, and the loss tangent is 0.001 (140 GHz); the thickness of the gold layer plated on the upper and lower surfaces 9 of the alumina ceramic plate is 4 μm, and the diameter and spacing of the metal via hole 8 on the ceramic plate are determined by formula calculation to ensure adaptation to the SIW width and form effective electromagnetic constraints.

[0040] As an example, the machined metal base is made of aluminum alloy through a CNC milling process.

[0041] Figure 4 The top view of the machined metal base is shown in Figure 14, and the recessed groove of the machined metal base is adapted to the PCB solderless connector.

[0042] Figure 5 The electric field distribution is shown in Figure 18, which shows that the electric field energy is coupled from the SIW to the RWG, indicating that the transition structure can effectively realize mode conversion.

[0043] Figure 6 The S-parameter simulation curve of the SIW-to-RWG transition is shown in Figure 19, which shows that the return loss of the transition structure is better than 10 dB in the frequency band of 69.7-93 GHz, and the impedance bandwidth reaches 28.6%, indicating that the transition structure has good impedance matching performance in a wide frequency band.

[0044] Figure 7 The simulation S-parameter, gain curve, and measured S-parameter curves of the on-chip reference antenna are shown in Figure 20. In the frequency band of 70-94 GHz, the return loss (|S 11 |) of the antenna is better than -10 dB, the relative bandwidth reaches 29.3%, and the simulation and measurement results are consistent; the gain curve shows a linear upward trend, and reaches a peak gain of 18 dBi at 94 GHz, with stable and reliable performance.

[0045] Figure 8 The normalized directional patterns of the on-chip reference antenna at frequencies of 70 GHz, 80 GHz, and 90 GHz are shown in Figure 21. The E-plane and H-plane directional patterns at the three frequency points show good symmetry and stable beam width, indicating that the antenna has excellent radiation performance.

[0046] Working principle: The radio frequency signal is input to the pad 2 through the probe, enters the substrate integrated waveguide through the 50-ohm transmission line 3 and the low-loss GCPW-to-SIW transition structure 4. The TE 10 mode energy in the substrate integrated waveguide is effectively coupled and converted to the TE 10The mode is finally radiated outward through the 3D printed horn antenna 5.

[0047] In summary, the application provides a high-performance, low-cost, and easily integrated W-band broadband on-chip reference antenna, which is particularly suitable for precise measurement of millimeter-wave on-chip antennas. It should be understood by those skilled in the art that the single-layer dielectric circuit board is not limited to alumina ceramic, and other high-frequency PCB materials can also be used to achieve the same purpose.

[0048] The above description is only a description of the preferred examples of the application, and is not any limitation on the scope of the application, and any changes and modifications made by those skilled in the art according to the above disclosure are within the protection scope of the claims.

Claims

1. A W-band broadband on-chip reference antenna, characterized in that, The device comprises a 3D-printed metal horn antenna, a single-layer dielectric circuit board, and a machined metal substrate, which are fixedly connected from top to bottom. The single-layer dielectric circuit board integrates, from the signal input end to the radiating end, the following components in sequence: a metal pad for connecting an RF probe, a 50-ohm transmission line, a transition structure from a ground coplanar waveguide to a substrate integrated waveguide, a substrate integrated waveguide, and a vertical transition structure from a substrate integrated waveguide to a rectangular waveguide. The metal substrate has a metal back cavity and a stepped matching structure inside.

2. The W-band broadband on-chip reference antenna as described in claim 1, characterized in that, The vertical transition structure from the substrate-integrated waveguide to the rectangular waveguide includes a metal patch on the upper surface of the dielectric circuit board and a stepped matching structure at the bottom of the metal back cavity. An inductive metal pillar is disposed below the metal patch to optimize TE. 10 Pattern matching and transformation.

3. The W-band broadband on-chip reference antenna as described in claim 1, characterized in that, The substrate integrated waveguide is composed of periodically arranged metallized vias on the dielectric circuit board, and an independent metallized via is provided at the center of the dielectric resonant cavity to realize power division and cavity tuning.

4. The W-band broadband on-chip reference antenna as described in claim 1, characterized in that, The metal back cavity of the machined metal substrate is located directly below the dielectric substrate cavity. The inner wall of the metal back cavity is smooth, and its size is precisely aligned with the coupling structure on the dielectric circuit board, working together to extend the working bandwidth of the antenna.

5. The W-band broadband on-chip reference antenna as described in claim 1, characterized in that, The machined metal substrate also includes screw holes, positioning holes, and grooves for accommodating PCB solderless connectors.

6. The W-band broadband on-chip reference antenna as described in claim 1, characterized in that, The 3D-printed metal horn antenna is connected to the dielectric circuit board via a flange. The flange, dielectric circuit board, and machined metal substrate are compactly pressed together and fixed by positioning pins and bolts that penetrate each layer of the structure.

7. The W-band broadband on-chip reference antenna as described in claim 1, characterized in that, The metal pad is a 50-ohm microstrip line pad with a grounding via around it. The pad has good impedance matching characteristics in the frequency band up to 110 GHz, which can efficiently couple energy to the subsequent transmission line.

8. The W-band broadband on-chip reference antenna as described in claim 1, characterized in that, The transition structure from the grounded coplanar waveguide to the substrate integrated waveguide is a low-loss tapered gradient structure. Its gradient angle and length are optimized to ensure low-loss and low-reflection transmission of radio frequency signals from the coplanar waveguide to the substrate integrated waveguide.

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