High-level inter-isolation double-junction microstrip circulator isolator circuit structure

Abstract

The invention discloses an isolator circuit structure of a high-level inter-level isolation double-junction microstrip circulator, belongs to the field of microwave devices, and aims to shorten the length of an inductor and change the capacitance matched with the inductor, so that the plane size of a product can be effectively reduced; a three-section matching stub line interstage circuit structure design compensates the length of a connecting line between two loop junctions, so that the interstage isolation degree of the double-junction microstrip circulator isolator can be effectively improved; by combining the two designs, the interstage isolation degree of the double-junction microstrip circulator isolator is improved by more than 3dB under the condition that the size is not changed or reduced.

Description

Technical Field

[0001] The invention relates to the field of microwave devices, and in particular to a high-order isolation double-junction microstrip circulator isolator circuit structure. Background Art

[0002] There are two main circuit structures for inter-stage matching of existing double-junction microstrip circulator isolators: A kind of Figure 1 As shown, a 50 ohm microstrip transmission line 5 is directly used between the circulator and the isolator ( Figure 1 oval circle) connection; another Figure 3 As shown, a short stub 6 is added to the 50-ohm microstrip transmission line 5 connected between the circulator and the isolator ( Figure 3 oval circle); This type of double-junction microstrip circulator isolator uses a thin-film microstrip circuit structure. Figure 5 and Figure 6 As shown, the metal base plate 1 and the full metal surface of the spinning ferrite substrate 2 are connected by welding, and the circuit surface of the spinning ferrite substrate 2 and the ceramic gasket 3, and the ceramic gasket 3 and the permanent magnet 4 are connected by bonding.

[0003] The simulation diagrams of the structures of the above two connection modes are as follows: Figure 2 and Figure 4 As shown in the figure, it can be seen that due to size limitations, Figure 1 The connecting line between the two loop junctions of the structure is not long enough, and the high-order mode formed in the loop junction is not sufficiently decayed into the quasi-TEM mode of the microstrip line in the connecting line, resulting in the two junctions affecting each other and forming reflections, resulting in poor isolation between stages; and after adding a short stub Figure 3 Although the inter-stage isolation of the structure shown can be improved by more than 3dB, it still cannot meet the inter-stage isolation requirements of the T / R component for the double-junction microstrip circulator isolator.

[0004] That is, in order to adapt to the miniaturized design of current radar T / R components, the circuit design of the existing double-junction microstrip circulator isolator has been compressed in size, the connecting line between the two ring junctions has been shortened, and the high-order mode formed in the ring junction has not sufficiently fallen into the quasi-TEM mode of the microstrip line in the connecting line, resulting in the two junctions affecting each other and forming reflections, resulting in a decrease in inter-stage isolation; when the inter-stage isolation is reduced, the reflection formed will cause the standing wave at the antenna end of the T / R component to be larger, and the power amplifier of the T / R component is prone to load pulling. Summary of the invention

[0005] The purpose of the present invention is to provide a high-order isolation double-junction microstrip circulator isolator circuit to solve the above problems.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: a high-isolation double-junction microstrip circulator isolator circuit structure, including an inductor and a capacitor, the length of the inductor is shortened, and the shape of the capacitor matched with the inductor is changed to a rectangular capacitor, the width of the capacitor is not more than twice the width of a 50-ohm connecting line, and the length is not more than 1 / 8 of the wavelength; the connecting line between the circulator and the isolator is a 50-ohm microstrip transmission line with a short stub arranged on it, and three matching circuits are added on this basis.

[0007] As a preferred technical solution, the inductor length is shortened to 1 / 2 to 2 / 3 of the original inductor length.

[0008] As a preferred technical solution, the three added matching circuits are: adding a matching circuit between the circulator and the isolator, perpendicular to the midpoint of the stub; adding a matching circuit symmetrically at both ends of the stub. Through the matching and interaction of the three circuits, the electromagnetic field after the compensation transition is matched with the inter-stage transmission line, thereby achieving the purpose of reducing reflection and improving isolation.

[0009] As a further preferred technical solution, according to the LC matching design principle, the bandwidth and length of the three-segment circuit are determined, and the circuit width increased perpendicular to the midpoint of the short stub is not more than twice the width of the 50-ohm connecting line, and the length is not more than 1 / 8 wavelength.

[0010] As a further preferred technical solution, according to the LC matching design principle, the bandwidth and length of the three-segment circuit are determined, and the circuit width increased at both ends of the short stub is not more than twice the width of the 50-ohm connecting line, and the length is not more than 1 / 16 wavelength.

[0011] As a preferred technical solution, the total length of the short stub and the added three-section matching circuit is no longer than 1 / 4 wavelength.

[0012] The present invention is based on the original double-junction microstrip circulator isolator circuit design, and redesigns the inter-stage matching circuit structure, specifically including: 1. The original structure is a three-terminal symmetrical structure. The new circuit structure of the present invention shortens the inductor length and changes the capacitor matched with it at the same time, changing the original slot-shaped capacitor with coupling effect into a simple rectangular capacitor, and optimizing and limiting its bandwidth and length; 2. In order to compensate for the length of the connecting line between the two circulator junctions, three sections of matching circuits are added on the basis of the original short stub, that is, between the circulator and the isolator, at the midpoint of the short stub perpendicular to the connecting line, a matching circuit is added; and a matching circuit is added symmetrically at both ends of the short stub, which can effectively improve the inter-stage isolation of the double-junction microstrip circulator isolator. Compared with the original inter-stage matching scheme of the double-junction microstrip circulator isolator, the inter-stage isolation of the double-junction microstrip circulator isolator is improved by more than 3dB through the inter-stage matching circuit structure design of the three-segment matching short stub of the present invention while keeping the size unchanged or reduced.

[0013] Compared with the prior art, the advantages of the present invention are: the new inter-stage matching circuit structure of the present invention shortens the inductor length and changes the capacitor matched therewith, which can effectively reduce the product planar size; the three-segment matching short-stub inter-stage circuit structure design compensates for the length of the connecting line between the two ring junctions, which can effectively improve the inter-stage isolation of the double-junction microstrip circulator isolator; combining the above two designs, the inter-stage isolation of the double-junction microstrip circulator isolator can be improved by more than 3dB without changing or reducing the size. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a circuit diagram of a 50-ohm microstrip transmission line connection circuit between loop junctions in the prior art of the present invention; Figure 2 for Figure 1 Circuit structure simulation curve diagram; Figure 3 The circuit structure diagram of the prior art loop-interjunction 50-ohm microstrip transmission line plus a short stub of the present invention; Figure 4 for Figure 3 Circuit structure simulation curve diagram; Figure 5 and Figure 6 This is the structural diagram of the commonly used double-junction microstrip circulator isolator; Figure 7 This is a circuit diagram of an X-band double-junction microstrip circulator isolator according to Embodiment 1 of the present invention; Figure 8 for Figure 7 Circuit structure simulation diagram; Fig. 9 A comparison diagram of the circuit inter-stage isolation of Example 1 of the present invention and the circuit simulation results of the prior art; Fig.10 It is a circuit structure diagram of a C-band double-junction microstrip circulator isolator according to Embodiment 2 of the present invention; Fig.11 for Fig.10 Circuit structure simulation diagram; Fig.12 A comparison diagram of the circuit inter-stage isolation of Embodiment 2 of the present invention and the circuit simulation results of the prior art; Fig.13 This is a circuit diagram of a Ku-band double-junction microstrip circulator isolator according to Embodiment 3 of the present invention; Fig.14 for Fig.13 Circuit structure simulation diagram; Fig.15 The figure is a comparison diagram of the circuit inter-stage isolation of Example 3 of the present invention and the circuit simulation results of the prior art.

[0015] In the figure: 1. Metal base plate; 2. Spin-magnetic ferrite substrate; 3. Ceramic gasket; 4. Permanent magnet; 5. 50 ohm microstrip transmission line; 6. Short stub; 7. Inductor; 8. Capacitor; 9. Matching circuit. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with the accompanying drawings.

[0017] Embodiment 1:

[0018] An X-band double-junction microstrip circulator isolator circuit structure, see Figure 7 , including an inductor 7 and a capacitor 8, the length of the inductor 7 is shortened to 1 / 2 of the original inductor length, which is 0.28 mm, and the shape of the capacitor 8 matched with the inductor 7 is changed to a rectangular capacitor, the width of the capacitor 8 is 0.28 mm, and the length is 0.54 mm; the connection line between the circulator and the isolator is a 50-ohm microstrip transmission line 5 on which a short stub line 6 is provided, and three matching circuits 9 are added on this basis; In this embodiment, the three added matching circuits 9 are: between the circulator and the isolator, perpendicular to the midpoint of the stub 6, a matching circuit 9 is added, the width of the matching circuit 9 is 0.27 mm, and the length is 0.76 mm; a matching circuit 9 is added symmetrically at both ends of the stub 6, and the width of the two matching circuits 9 is 0.34 mm, and the length is 0.36 mm; The total length of the short stub 6 and the added three-stage matching circuit 9 is no longer than 1 / 4 wavelength; This embodiment is used for X-band. The simulation diagram of the circuit structure of this embodiment is as shown in FIG. Figure 8 As shown, the simulation results of the circuit of this embodiment and the circuit of the prior art are compared as shown in FIG. Fig. 9 As shown, Fig. 9 The solid line in the middle is the circuit result of this embodiment, and the dotted line is the circuit result of the prior art. It can be seen from the figure that in the frequency range of 9-10.2 GHz, the inter-stage isolation is improved from -26.83 dB to -29.33 dB.

[0019] Embodiment 2:

[0020] Compared with Example 1, this embodiment is a C-band double-junction microstrip circulator isolator circuit structure, including an inductor 7 and a capacitor 8. The length of the inductor 7 is shortened to 1 / 2 of the original inductor length, which is 0.62 mm, and the shape of the capacitor 8 matched with the inductor 7 is changed to a rectangular capacitor. The width of the capacitor 8 is 0.5 mm and the length is 1.75 mm. The connecting line between the circulator and the isolator is a 50-ohm microstrip transmission line 5 on which a short stub 6 is arranged. On this basis, three matching circuits 9 are added. Between the circulator and the isolator, a matching circuit 9 is added perpendicular to the midpoint of the short stub 6. The width of the matching circuit 9 is 0.56 mm and the length is 2 mm. A matching circuit 9 is symmetrically added at both ends of the short stub 6. The width of these two matching circuits 9 is 0.7 mm and the length is 0.65 mm. Its structure is as follows: Fig.10 As shown, the simulation diagram of the circuit structure of this embodiment is as shown in Fig.11 As shown, the simulation results of the circuit of this embodiment and the circuit of the prior art are compared as shown in FIG. Fig.12 As shown, Fig.12 The solid line in the middle is the circuit result of this embodiment, and the dotted line is the circuit result of the prior art. It can be seen from the figure that in the frequency range of 5.3-6.2 GHz, the inter-stage isolation is improved from -25.54 dB to -34.07 dB.

[0021] Embodiment 3:

[0022] Compared with Example 1, this embodiment is a Ku-band double-junction microstrip circulator isolator circuit structure, in which the length of the inductor 7 is shortened to 1 / 2 of the original inductor length, which is 0.62 mm, and the shape of the capacitor 8 matched with the inductor 7 is changed to a rectangular capacitor, and the width of the capacitor 8 is 0.5 mm and the length is 1.75 mm; the connecting line between the circulator and the isolator is a 50-ohm microstrip transmission line 5 on which a short stub 6 is arranged, and three matching circuits 9 are added on this basis, and between the circulator and the isolator, a matching circuit 9 is added perpendicular to the midpoint of the short stub 6, and the width of the matching circuit 9 is 0.56 mm and the length is 2 mm; a matching circuit 9 is added symmetrically at both ends of the short stub 6, and the width of these two matching circuits 9 is 0.7 mm and the length is 0.65 mm; its structure is as follows Fig.13 As shown, the simulation diagram of the circuit structure of this embodiment is as shown in Fig.14 As shown, the simulation results of the circuit of this embodiment and the circuit of the prior art are compared as shown in FIG. Fig.15 As shown, Fig.15 The solid line in the middle is the circuit result of this embodiment, and the dotted line is the circuit result of the prior art. It can be seen from the figure that in the frequency range of 15-17.5 GHz, the inter-stage isolation is improved from -24.85 dB to -30.05 dB.

[0023] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-isolation double-junction microstrip circulator isolator circuit structure, including an inductor and a capacitor, characterized in that: The length of the inductor is shortened, and the shape of the capacitor matching the inductor is changed to a rectangular capacitor. The width of the capacitor is no more than twice the width of the 50-ohm connecting line, and the length is no more than 1 / 8 wavelength. The connecting line between the circulator and the isolator is a 50-ohm microstrip transmission line with a short stub, and three matching circuits are added on this basis.

2. A high-isolation double-junction microstrip circulator isolator circuit structure according to claim 1, characterized in that: The inductor length is shortened to 1 / 2 to 2 / 3 of the original inductor length.

3. The high-isolation double-junction microstrip circulator isolator circuit structure according to claim 1, characterized in that: The three added matching circuits are: adding a matching circuit between the circulator and the isolator, perpendicular to the midpoint of the short stub; and adding a matching circuit symmetrically at both ends of the short stub.

4. The high-isolation double-junction microstrip circulator isolator circuit structure according to claim 3, characterized in that: The circuit width increased perpendicular to the midpoint of the short stub is no more than twice the width of a 50-ohm connection line, and the length is no more than 1 / 8 of a wavelength.

5. The high-isolation double-junction microstrip circulator isolator circuit structure according to claim 3, characterized in that: The circuit width increased at both ends of the short stub is no more than twice the width of a 50-ohm connection line, and the length is no more than 1 / 16 of a wavelength.

6. The high-isolation double-junction microstrip circulator isolator circuit structure according to claim 1, characterized in that: The total length of the short stub and the added three-section matching circuit is no longer than 1 / 4 wavelength.

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