Ultra-wideband bridge based on GaAs IPD technology

Abstract

The invention relates to the field of radio frequency devices, in particular to an ultra-wideband bridge based on a GaAs IPD process, which comprises a GaAs substrate, the GaAs substrate comprises three metal layers, the metal layers comprise a metal layer M1, a metal layer M2 and a metal layer M3, and the metal layer M1, the metal layer M2 and the metal layer M3 are used for forming a partial structure of the bridge. The surface of the metal layer M1, the surface of the metal layer M2 and the surface of the metal layer M3 are wrapped with thin-film polyimide media and thin-film silicon nitride media, the winding line structure is used, the overall size of the bridge is effectively compressed, the bridge is more suitable for miniaturized equipment, three sets of coupling lines (the first coupling line, the second coupling line and the third coupling line) are divided into a plurality of sections, and therefore the coupling lines are divided into multiple sections. And a parallel compensation capacitor is arranged between every two sections, so that the phase velocity difference between odd and even modes of the coupling line is effectively reduced, the port matching performance is improved, and the bridge structure is more compact and stable by adopting the three metal layers (M1, M2 and M3).

Description

Technical Field

[0001] The invention relates to the field of radio frequency devices, in particular to an ultra-wideband bridge based on GaAs IPD technology. Background Art

[0002] As the operating frequency and bandwidth of wireless communication systems continue to increase, the demand for high-performance, miniaturized microwave passive components is becoming increasingly urgent. As a key passive component, ultra-wideband orthogonal couplers play an important role in wireless communication systems. They are mainly used to distribute RF signals to two output ports and maintain a 90-degree phase difference between the two output signals. Such devices are crucial in applications such as power distribution, signal mixing, and beamforming of antenna arrays. Therefore, in-depth research on them has important practical significance.

[0003] Limitations of Traditional UWB Bridges

[0004] The traditional ultra-wideband bridge structure is usually composed of multiple stages of 90-degree coupled lines in series, and the number of stages is directly related to the required bandwidth. In other words, in order to meet higher bandwidth requirements, the number of coupled lines must be increased, which inevitably leads to an increase in the size of the bridge. In addition, since each stage of coupled lines will introduce a certain amount of loss, the more stages there are, the greater the overall insertion loss.

[0005] Challenges of On-Chip Bridge Design

[0006] In the design of on-chip devices, size and cost control are important considerations. In order to achieve broadband requirements, on-chip bridge designs often use transformer-coupled lines instead of traditional transmission line-coupled lines, and achieve the required broadband performance by cascading multiple transformers. However, the line width and line spacing of transformer-coupled lines are limited by process conditions, making it difficult for the actual coupling degree to meet theoretical requirements, which in turn makes the insertion loss of such designs generally large. For example, the existing 2-18GHz bridge products on the market usually have an insertion loss of close to 9dB at the high frequency end, which is a significant problem for some loss-sensitive applications.

[0007] Design Difficulties of Strongly Coupled Bridge

[0008] Considering that the bridge is a strong coupling device (coupling degree is about 3dB), in order to achieve ideal performance, the coupling degree of the middle coupling line needs to reach 2dB, which is very difficult in actual design. Therefore, another common design method is to connect two 8.34dB orthogonal couplers in series, which can greatly reduce the coupling degree requirements. However, the cost of this method is doubling the electrical length, which makes it difficult to further compress the size of the bridge, which is particularly disadvantageous in space-constrained application scenarios. Summary of the invention

[0009] 1. Technical issues to be resolved

[0010] In view of the deficiencies of the prior art, the present invention provides an ultra-wideband bridge based on GaAs IPD technology.

[0011] (II) Technical solution

[0012] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: an ultra-wideband bridge based on GaAs IPD process of the present invention comprises a GaAs substrate, wherein the GaAs substrate comprises three metal layers, and the metal layers comprise a metal layer M1, a metal layer M2 and a metal layer M3, wherein the metal layers M1, M2 and M3 are used to form a partial structure of the bridge, and the surfaces of the metal layers M1, M2 and M3 are wrapped with a thin film polyimide medium and a thin film silicon nitride medium, wherein the thin film silicon nitride medium is wrapped on the outside of the thin film polyimide medium, and the bottom of the GaAs substrate is electroplated with gold as a ground plane, and the GaAs substrate is provided with three groups of coupling lines, including coupling line one, coupling line two and coupling line three, and the three groups of coupling lines are adapted to form a bridge with the three metal layers, and the three groups of coupling lines are arranged in a meandering line structure, wherein the coupling line one and the coupling line three are each provided with one group, and the coupling line two is provided with two groups, each group of coupling lines is divided into a plurality of sections, and a parallel compensation capacitor is provided between each section.

[0013] Preferably, the coupling coefficient of coupling line one is the highest, and the electrical length is 90 degrees; the coupling coefficient of coupling line two is the lowest, and the electrical length is 90 degrees; the coupling coefficient of coupling line three is in the middle, and its electrical length is 270 degrees.

[0014] Further preferably, the bridge includes node one, node two, node three, node four, node five and node six, the node one is the input port of the bridge, the node two is the coupled output port of the bridge, the node three is the through output port of the bridge, the node four is the phase compensation transmission line, the node five is the compensation capacitor, and the node six is ​​the matching load of the isolation port of the bridge.

[0015] Again preferably, the input port of the coupling line one is the input port of the bridge, the isolation port of the coupling line one is also the isolation port of the entire bridge, and the coupling end and the through end of the coupling line one are respectively connected to the input ends of the coupling line two at the left and right ends.

[0016] Preferably, the coupling ends of the two sections of coupling line 2 are respectively used as two output ports of the bridge, and the through end and the isolation end of the coupling line 2 are respectively connected to the two sides of coupling line 3.

[0017] Further preferably, the return loss of the bridge in the frequency band of 2-18 GHz is higher than 15 dB, the maximum value in the band is greater than 40 dB, the maximum insertion loss of the coupled output port of the bridge is 6.5 dB, and the maximum insertion loss of the direct output port of the bridge is 5.5 dB.

[0018] Again preferably, the average amplitude error of the bridge within the band is 0.74 dB, and the maximum amplitude error occurs at 2 GHz, which is 2.3 dB.

[0019] Preferably, the average phase difference of the bridge within the band is 89.5 degrees, which is 0.5 degrees different from the ideal value, and the maximum phase error occurs at 18 GHz.

[0020] (III) Beneficial effects

[0021] Compared with the prior art, the present invention provides an ultra-wideband bridge based on GaAs IPD technology, which has the following beneficial effects:

[0022] Material and structure optimization:

[0023] GaAs substrate: The use of a 100-micron thick GaAs substrate ensures that the bridge has good high-frequency characteristics.

[0024] Multi-layer metal structure: Three metal layers (M1, M2, M3) are used to make the bridge structure more compact and stable.

[0025] Dielectric material: The surface of the metal layer is covered with a thin film polyimide dielectric, and the outside is covered with a thin film silicon nitride dielectric, which enhances the mechanical strength and electrical performance of the bridge.

[0026] Ground plane: The bottom of the GaAs substrate is electroplated with gold as the ground plane, which provides a good grounding effect and reduces signal reflection and interference.

[0027] Coupled Line Design:

[0028] Coupling line segmentation and compensation capacitor: The three groups of coupling lines (coupling line 1, coupling line 2, coupling line 3) are divided into several segments, and a parallel compensation capacitor is set between each segment, which effectively reduces the phase velocity difference between the odd and even modes of the coupling lines and improves the port matching.

[0029] Coupling coefficient and electrical length: Coupling line 1 has the highest coupling coefficient and an electrical length of 90 degrees; coupling line 2 has the lowest coupling coefficient and an electrical length of 90 degrees; coupling line 3 has a coupling coefficient between the two and an electrical length of 270 degrees. This design allows the bridge to maintain good coupling characteristics at different frequencies.

[0030] Node optimization:

[0031] Node definition and connection method: By defining the key nodes of the bridge (node ​​one to node six), the input and output ports and their functions are clarified, and the internal signal path of the bridge is optimized.

[0032] Coupling line 1: Its input port serves as the input port of the bridge, the isolation port serves as the isolation port of the bridge, and the coupling end and the through end are respectively connected to the input end of coupling line 2, forming an effective signal distribution path.

[0033] Coupling line 2: The coupling ends of the two sections of coupling line 2 serve as the two output ports of the bridge, and the through end and the isolation end are respectively connected to the two sides of coupling line 3, thereby achieving effective signal separation.

[0034] Performance improvements:

[0035] Return loss: The bridge exhibits high return loss (above 15dB) in the 2-18GHz frequency band, especially reaching over 40dB at certain frequencies, which indicates that the bridge has good impedance matching characteristics.

[0036] Insertion loss: The maximum insertion loss of the coupled output port is 6.5dB, and the maximum insertion loss of the through output port is 5.5dB, which means that the bridge has less loss when transmitting signals.

[0037] Amplitude and phase error: The average amplitude error within the band is 0.74dB, and the maximum amplitude error occurs at 2GHz, which is 2.3dB; the average phase difference is 89.5 degrees, which is 0.5 degrees different from the ideal value, and the maximum phase error occurs at 18GHz. These indicators show that the bridge can maintain good amplitude and phase consistency within a wide bandwidth.

[0038] Overall benefits:

[0039] Size reduction: By using a meander wire structure, the overall size of the bridge is effectively reduced, making it more suitable for miniaturized devices.

[0040] Wide applicability: Due to its good performance in the 2-18GHz frequency band, the bridge is suitable for a variety of high-frequency communications and microwave applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of the GaAs substrate process of the present invention;

[0042] Figure 2 It is a schematic diagram of the principle of the electric bridge of the present invention;

[0043] Figure 3 It is a structural schematic diagram of the bridge of the present invention;

[0044] Figure 4It is a schematic diagram of the simulated insertion loss and return loss of the bridge of the present invention;

[0045] Figure 5 It is a schematic diagram of the simulated output amplitude error of the bridge of the present invention;

[0046] Figure 6 It is a schematic diagram of the simulated output phase difference of the bridge of the present invention;

[0047] In the figure: 1, node one; 2, node two; 3, node three; 4, node four; 5, node five; 6, node six. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] See also Figure 1-6 The working principle and preferred technical scheme of the ultra-wideband bridge based on GaAs IPD technology of the present invention are as follows:

[0050] Materials and structure: Figure 1 Shown

[0051] GaAs substrate: A GaAs substrate with a thickness of preferably 100 microns is used as the substrate of the bridge.

[0052] Three metal layers: including metal layer M1, metal layer M2 and metal layer M3. These metal layers are used to form different parts of the bridge.

[0053] Dielectric material: The surfaces of the metal layers M1, M2, and M3 are wrapped with a thin film polyimide dielectric, and the thin film silicon nitride dielectric is wrapped outside the thin film polyimide dielectric to improve the mechanical strength and electrical performance of the bridge, and the thin film polyimide dielectric is preferably wrapped in two layers on the surfaces of the metal layers M1, M2, and M3.

[0054] Ground plane: The bottom of the GaAs substrate is electroplated with gold as the ground plane to provide good grounding.

[0055] Coupled line design: Figure 2 Shown

[0056] Three groups of coupling lines: including coupling line 1, coupling line 2 and coupling line 3. Coupling line 1 and coupling line 3 each have one group, and coupling line 2 includes two groups.

[0057] Coupled line segmentation: Each set of coupled lines is divided into several segments, and a parallel compensation capacitor is set between each segment to reduce the phase velocity difference between the odd and even modes of the coupled lines, thereby improving port matching.

[0058] Coupling coefficient: Coupling line one has the highest coupling coefficient, and its electrical length is 90 degrees; coupling line two has the lowest coupling coefficient, and its electrical length is also 90 degrees; coupling line three has a coupling coefficient between the two, and its electrical length is 270 degrees.

[0059] Node definition: Figure 3 Shown

[0060] Node 1: represents the input port of the bridge.

[0061] Node 2: represents the coupled output port of the bridge.

[0062] Node 3: represents the direct output port of the bridge.

[0063] Node 4: represents a transmission line added at the coupled output port for phase compensation.

[0064] Node five 5: represents the compensation capacitance of three sets of coupling lines.

[0065] Node six 6: represents the matching load of the bridge isolation port.

[0066] Connection method: Figure 2 As shown (where coupling line 1 represents coupling line 1, coupling line 2 represents coupling line 2, coupling line 3 represents coupling line 3, port 1 represents input port, port 2 and port 3 represent output ports, Cp1, Cp2 and Cp3 represent compensation capacitors)

[0067] Coupling line 1: The input port serves as the input port of the bridge; the isolation port serves as the isolation port of the entire bridge; the coupling end and the through end are respectively connected to the input ends of coupling line 2 at the left and right ends.

[0068] Coupling line 2: It is divided into two sections, and the coupling end of each section of coupling line 2 serves as the two output ports of the bridge; the through end and the isolation end are respectively connected to the two sides of coupling line 3.

[0069] Performance parameters:

[0070] like Figure 4 As shown, |S11| represents the return loss / reflection coefficient of the bridge input port, |S21| represents the insertion loss of the coupled output port, and |S31| represents the insertion loss of the through output port.

[0071] Return loss: The return loss of the bridge in the 2-18GHz frequency band is higher than 15dB, and the maximum value in the band is greater than 40dB;

[0072] Insertion loss: The maximum insertion loss of the coupled output port is 6.5dB; the maximum insertion loss of the through output port is 5.5dB.

[0073] like Figure 5 Shown

[0074] Amplitude error: The average amplitude error within the band is 0.74dB, and the maximum amplitude error occurs at 2GHz, which is 2.3dB.

[0075] like Figure 6 Shown

[0076] Phase difference: The average phase difference within the band is 89.5 degrees, which is 0.5 degrees different from the ideal value (90 degrees); the maximum phase error occurs at 18 GHz, which is 4.2 degrees different from the ideal value.

[0077] advantage:

[0078] Size reduction: All three sets of coupled lines utilize a meandering line structure to reduce the overall size, thereby reducing the overall size of the bridge.

[0079] Performance improvement: Through optimized design, the phase velocity difference between the odd and even modes of the coupled lines is reduced, the port matching performance of the bridge is improved, and good performance in the 2-18GHz frequency band is achieved.

[0080] In summary, the present invention provides an ultra-wideband bridge based on GaAs IPD technology, which realizes high-performance ultra-wideband communication function through carefully designed material combination, coupling line layout and compensation capacitor configuration, and is suitable for high-frequency communication and microwave applications.

[0081] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An ultra-wideband bridge based on GaAs IPD technology, characterized in that: The invention comprises a GaAs substrate, wherein the GaAs substrate comprises three metal layers, and the metal layers comprise a metal layer M1, a metal layer M2 and a metal layer M3, wherein the metal layers M1, M2 and M3 are used to form a partial structure of an electric bridge, and the surfaces of the metal layers M1, M2 and M3 are wrapped with a thin film polyimide medium and a thin film silicon nitride medium, wherein the thin film silicon nitride medium is wrapped on the outside of the thin film polyimide medium, and the bottom of the GaAs substrate is electroplated with gold as a ground plane, and the GaAs substrate is provided with three groups of coupling lines, including a coupling line 1, a coupling line 2 and a coupling line 3, and the three groups of coupling lines are adapted to form an electric bridge with the three metal layers, and the three groups of coupling lines are arranged in a meandering line structure, wherein the coupling line 1 and the coupling line 3 are each provided with a group, and the coupling line 2 is provided with two groups, each group of coupling lines is divided into a plurality of sections, and a parallel compensation capacitor is provided between each section.

2. The ultra-wideband bridge based on GaAs IPD technology according to claim 1, characterized in that: The coupling coefficient of the coupling line 1 is the highest, and the electrical length is 90 degrees. The coupling coefficient of the coupling line 2 is the lowest, and the electrical length is 90 degrees. The coupling coefficient of the coupling line 3 is in the middle, and its electrical length is 270 degrees.

3. The ultra-wideband bridge based on GaAs IPD process according to claim 2, characterized in that: The bridge comprises a node one (1), a node two (2), a node three (3), a node four (4), a node five (5) and a node six (6), wherein the node one (1) is an input port of the bridge, the node two (2) is a coupled output port of the bridge, the node three (3) is a direct output port of the bridge, the node four (4) is a phase compensation transmission line, the node five (5) is a compensation capacitor, and the node six (6) is a matching load of an isolation port of the bridge.

4. The ultra-wideband bridge based on GaAs IPD process according to claim 3, characterized in that: The input port of the coupling line 1 is the input port of the bridge, the isolation port of the coupling line 1 is also the isolation port of the entire bridge, and the coupling end and the through end of the coupling line 1 are respectively connected to the input ends of the coupling line 2 at the left and right ends.

5. The ultra-wideband bridge based on GaAs IPD process according to claim 4, characterized in that: The coupling ends of the two sections of the coupling line 2 are respectively used as two output ports of the bridge, and the through end and the isolation end of the coupling line 2 are respectively connected to the two sides of the coupling line 3.

6. The ultra-wideband bridge based on GaAs IPD process according to claim 5, characterized in that: The return loss of the bridge in the 2-18 GHz frequency band is higher than 15 dB, and the maximum value in the band is greater than 40 dB. The maximum insertion loss of the coupled output port of the bridge is 6.5 dB, and the maximum insertion loss of the direct output port of the bridge is 5.5 dB.

7. The ultra-wideband bridge based on GaAs IPD technology according to claim 6, characterized in that: The average amplitude error of the bridge within the band is 0.74 dB, and the maximum amplitude error occurs at 2 GHz, which is 2.3 dB.

8. The ultra-wideband bridge based on GaAs IPD technology according to claim 7, characterized in that: The average phase difference of the bridge within the band is 89.5 degrees, which is 0.5 degrees different from the ideal value, and the maximum phase error occurs at 18 GHz.

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