Wideband, low-error on-chip coupler based on quasi-degenerate mode technique

Abstract

A broadband, low-error on-chip coupler based on quasi-degenerate mode technology includes: multiple stacked ground layers on the chip, and a first coil and a second coil coupled to each other on the top ground layer. The coils are not in contact with the ground layers. The two ends of the first coil are connected to an input port and a through port, respectively. The two ends of the second coil are connected to an isolation port and a coupling port, respectively. The ground layers are connected to an external ground level. This invention can accurately anchor the product of even-mode and odd-mode impedances to a 50Ω system impedance while achieving a quasi-degenerate mode state for the even-mode and odd-mode, i.e., keeping the phase constants of the even-mode and odd-mode close within the target frequency band, thus solving the phase mismatch problem in the broadband range. Experimental results show that in the 80–120 GHz frequency band, the phase difference between the output signals of the through port and the coupling port remains within ±1.1° compared to 90°, achieving orthogonal characteristics.

Description

Technical Field

[0001] This invention relates to a technology in the field of radio frequency devices, specifically a broadband, low-error on-chip orthogonal coupler based on quasi-degenerate mode technology. Background Technology

[0002] Existing on-chip quadrature couplers struggle to achieve a high balance between amplitude and phase performance across the millimeter-wave wideband. The mismatch in their odd-even mode propagation characteristics leads to phase imbalance between the through-end and the coupled end, limiting the operating bandwidth and severely restricting the integration performance of modern communication / radar systems. Summary of the Invention

[0003] This invention addresses the shortcomings of existing technologies, such as complex structures, difficulty in on-chip integration, control of only a single capacitive parasitic property, and inability to ensure the performance of orthogonal couplers in the millimeter-wave broadband range. It proposes a broadband, low-error on-chip orthogonal coupler based on quasi-degenerate mode technology. This technology achieves precise anchoring of the product of even-mode and odd-mode impedances to a 50Ω system impedance while maintaining a quasi-degenerate mode state for both even and odd modes. Specifically, it keeps the phase constants of even and odd modes close within the target frequency band, thus solving the phase mismatch problem in the broadband range. Experimental results show that in the 80–120 GHz frequency band, the phase difference between the output signals of the through port and the coupled port remains within ±1.1° compared to 90°, achieving orthogonal characteristics.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a broadband, low-error on-chip orthogonal coupler based on quasi-degenerate mode technology, comprising: multiple stacked ground layers on the chip and a first coil and a second coil coupled to each other on the top ground layer, wherein: the coils are not in contact with the ground layers, the two ends of the first coil are respectively connected to an input port and a through port, the two ends of the second coil are respectively connected to an isolation port and a coupling port, and the ground layer is connected to the off-chip ground level.

[0006] The isolation port is connected to an on-chip 50 series to ground. resistance.

[0007] The multiple stacked grounding layers consist of at least six layers, wherein: the five grounding layers from top to bottom are each provided with a hollow groove for setting the first coil and the second coil, and the center part of the hollow groove is grounded.

[0008] The odd-mode phase constant βo and even-mode phase constant βe of the orthogonal coupler remain close within 80–120 GHz and do not change significantly with frequency, thus reaching a quasi-degenerate mode state.

[0009] The first and second coils are made of copper with a thickness of 3.2 μm, and both are wound with square wires with a side length of 180 μm.

[0010] The total height of the multiple stacked grounding layers is 8.2 μm, and the depth of the hollowed-out groove is 6.7 μm.

[0011] The grounding layer is made of copper.

[0012] Technical effect

[0013] This invention surrounds the first and second coils with multiple stacked, slot-shaped grounding layers, artificially reshaping and controlling the electromagnetic field distribution. This increases the parasitic capacitance to ground of the first and second coils, precisely controlling the balance between their even-mode and odd-mode impedances. This keeps the phase constants βo and βe of the even and odd modes close within the 80–120 GHz range, forming a quasi-degenerate mode state. In testing of the on-chip quadrature coupler chip, within the 80–120 GHz wideband, the phase difference between the output signals of the through port and the coupled port remains within ±1.1° compared to 90°, and the amplitude imbalance is less than 0.25 dB. This quasi-degenerate mode operation overcomes the technical bottlenecks of narrow bandwidth and large errors in traditional on-chip quadrature couplers, offering a compact chip area and providing a low-error, wide-bandwidth, small-area on-chip quadrature signal generation solution for millimeter-wave communication and radar systems. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention;

[0015] Figure 2 for Figure 1 Cross-sectional view;

[0016] Figure 3 for Figure 2 Equivalent circuit diagram;

[0017] Figure 4 This is a physical image of the present invention;

[0018] Figures 5-10 This is a schematic diagram illustrating the effect of an example. Detailed Implementation

[0019] like Figures 1-4 As shown, this embodiment relates to a broadband, low-error on-chip orthogonal coupler based on quasi-degenerate mode technology, which includes: multiple stacked ground layers 3 on the chip and two mutually coupled first coil 1 and second coil 2 disposed in the top ground layer.

[0020] Both the first coil 1 and the second coil 2 are square-wound wires with a side length of 180μm, a wire width of 5μm, and a wire spacing of 3μm.

[0021] The first coil 1 is connected to input port 1a and through port 1b, and the second coil 2 is connected to coupling port 2a and isolation port 2b. Isolation port 2b is connected to an on-chip 50 The resistor is connected in series to ground.

[0022] like Figure 2 As shown, the multiple stacked grounding layers 3 consist of nine interconnected first to ninth grounding layers 301-309, with a total height of 8.2μm.

[0023] The first to fifth grounding layers 301-305 are provided with hollow grooves, the depth of which is 6.7μm and the horizontal distance between the hollow grooves and the coil is 15μm.

[0024] The distance from the bottom of the ninth grounding layer to the top of the sixth grounding layer is 1.5 μm.

[0025] like Figure 3 As shown, due to the even-mode impedance Z0e of the coupling between the first coil and the second coil and The even-mode impedance Z0e is proportional to the ground parasitic capacitances C11 and C22 of the first and second coils, thus reducing the even-mode impedance Z0e. The even-mode impedance Z0e decreases to 74.3Ω. Simultaneously, for a system matching impedance of 50Ω, the reduction in even-mode impedance provides room for increasing odd-mode impedance. Due to the odd-mode impedance... By reducing the coupling capacitance C12, the odd-mode impedance Z0o was increased to 32.7 Ω. The characteristic impedance of the coupler is maintained through this weighted allocation of odd and even mode impedances: It is matched to the impedance of a 50Ω system.

[0026] like Figure 5 As shown, the amplitude response of the on-chip quadrature coupler of this invention is compared with that of a conventional quadrature coupler. The through-port amplitude response and coupled-port amplitude response of a conventional quadrature coupler can only remain equal within a narrow bandwidth. In contrast, the on-chip quadrature coupler of this invention can guarantee equal through-port amplitude response and coupled-port amplitude response in the 80–120 GHz range.

[0027] like Figure 6 The figure shows the simulation results of the odd-mode phase constant βo and the even-mode phase constant βe of this invention. This invention reduces the difference between the odd-mode and even-mode phase constants, keeping βo and βe consistent over a wide frequency band. Within the 80–120 GHz range, the ratio of the even-mode phase constant to the odd-mode phase constant, βe / βo, is maintained below 1.08, achieving orthogonality between the through-port and coupled-port outputs.

[0028] Through practical application experiments, based on the on-chip orthogonal coupler chip of this invention, and in a test environment based on a vector network analyzer, the amplitude response and phase response from the input port to the through port and the coupling port were measured. The broadband, low-error on-chip orthogonal coupler based on quasi-degenerate mode technology of this invention were measured, and the experimental data obtained are as follows:

[0029] like Figure 7 The image shows the raw test data for the amplitude response from the input port to the through port and the coupled port within the 80-120 GHz range. It can be seen that the amplitude response from the input port to the through port is -2.99 dB to -3.22 dB in the 80–120 GHz range, and the amplitude response from the input port to the coupled port is -3.01 dB to -3.25 dB in the same range. Further subtracting the two amplitude responses and taking the absolute value generates the following result: Figure 8 The amplitude error curve is shown. Within the 80–120 GHz range, the amplitude imbalance of the on-chip quadrature coupler of this invention is less than 0.25 dB.

[0030] like Figure 9 The image shows the raw test data for the phase response from the input port to the through port and the coupled port within the 80–120 GHz range. It can be seen that the phase response from the input port to the through port ranges from -76.42° to -101.94° within the 80–120 GHz range, while the phase response from the input port to the coupled port ranges from +12.94° to -11.37° within the same range. Further subtracting the two phase responses, then subtracting 90° and taking the absolute value, yields the following result: Figure 10 The phase error curve is shown. Within the 80–120 GHz range, the phase imbalance of the on-chip quadrature coupler of this invention is within ±1.1°, ensuring orthogonality. This orthogonality characteristic is crucial for the performance of beamforming and image rejection mixers in millimeter-wave on-chip systems.

[0031] Compared with the prior art, the present invention surrounds the coupling coil with multiple stacked grounding layers in a slot shape, reshapes and controls the electromagnetic field distribution, increases the parasitic capacitance to ground of the coupling coil, and precisely controls the balance between its even-mode impedance and odd-mode impedance, so that the phase constants βo and βe of the even-mode and odd-mode remain close within 80–120 GHz, forming a quasi-degenerate mode state.

[0032] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A broadband, low-error on-chip coupler based on quasi-degenerate mode technology, characterized in that, include: The chip has multiple stacked ground planes and a first coil and a second coil coupled to each other on the top ground plane. The coils are not in contact with the ground planes. The two ends of the first coil are connected to the input port and the through port, respectively. The two ends of the second coil are connected to the isolation port and the coupling port, respectively. The ground plane is connected to the ground level outside the chip.

2. The broadband, low-error on-chip coupler based on quasi-degenerate mode technology according to claim 1, characterized in that, The isolation port is connected to an on-chip 50 series to ground. resistance.

3. The broadband, low-error on-chip coupler based on quasi-degenerate mode technology according to claim 1, characterized in that, The multiple stacked grounding layers consist of at least six layers, wherein: the five grounding layers from top to bottom are each provided with a hollow groove for setting the first coil and the second coil, and the center part of the hollow groove is grounded.

4. The broadband, low-error on-chip coupler based on quasi-degenerate mode technology according to claim 1, characterized in that, Both the first and second coils are wound with square wire.

5. The broadband, low-error on-chip coupler based on quasi-degenerate mode technology according to claim 1 or 4, characterized in that, Both the first and second coils are square-wound wires with a side length of 180μm, a wire width of 5μm, and a wire spacing of 3μm.

6. The broadband, low-error on-chip coupler based on quasi-degenerate mode technology according to claim 1 or 3, characterized in that, The multiple stacked grounding layers consist of nine interconnected first to ninth grounding layers. The first to fifth grounding layers are provided with hollow slots for setting the first coil and the second coil. The horizontal distance between the hollow slots and the coils is 15μm.

7. The broadband, low-error on-chip coupler based on quasi-degenerate mode technology according to any one of claims 1-6, characterized in that, The increase in the parasitic capacitances to ground C11 and C22 of the first and second coils reduced the even-mode impedance Z0e. The even-mode impedance Z0e decreased to 74.3Ω; For a system matching impedance of 50Ω, the reduction in even-mode impedance provides room for the increase in odd-mode impedance. Because of the odd-mode impedance... By reducing the coupling capacitance C12, the odd-mode impedance Z0o was increased to 32.7 Ω. This maintains the characteristic impedance of the coupler. It is matched to the impedance of a 50Ω system.

8. The broadband, low-error on-chip coupler based on quasi-degenerate mode technology according to claim 7, characterized in that, The total height of the multiple stacked grounding layers is 8.2 μm, and the depth of the hollowed-out groove is 6.7 μm.

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