CN104282969A - Band stop microstrip line filter - Google Patents

Abstract

The invention discloses a band-stop microstrip line filter. It includes a substrate, an input transmission line, a zigzag transmission line, an output transmission line, a quarter oval ground plate, and a symmetrical T-shaped coupling line connected in a square; An oval ground plate, one end of the zigzag transmission line is connected to one end of the input transmission line, the other end of the input transmission line is connected to the left end of the substrate, the other end of the zigzag transmission line is connected to one end of the output transmission line, and the other end of the output transmission line is connected to the right end of the substrate; An inscribed symmetrical T-shaped coupling line composed of 2×9 square inscribed symmetrical T-shaped coupling line units. The square inscribed symmetrical T-shaped unit includes a square ring and two T-shaped coupling lines. The invention has the advantages of good filtering performance, low insertion loss, simple structure, small size, convenient manufacture and integration.

Description

Band stop microstrip line filter

technical field

The invention relates to a microwave filter, in particular to a band-stop microstrip line filter.

Background technique

With the rapid development of radio technologies such as radar technology and wireless communication, microwave radio frequency circuits and systems have received more and more attention. The microwave filter is one of the important components, and its performance determines the working quality of the system to a large extent. Systems with various functions have been developed one after another, making microwave spectrum resources increasingly tight and frequency intervals shrinking, which puts forward higher requirements for filters. Among them, the microstrip filter is widely used because of its high performance, small size, short design cycle, easy integration, and easy processing with photolithography technology. In recent years, the development of high-performance substrate materials has enabled microstrip filters to be applied in a large frequency range, making microstrip filters the most commonly used filter type.

Low-pass filter and band-stop filter are one of the important components of the filter, which are used in the front stage of the transmitter or the rear stage of the receiver to filter out unwanted high-frequency signals. In recent years, there are also many literatures on the wide stopband bandstop filter. The wide stopband bandstop filter has the advantages of low in-band loss, small fluctuation, small reflection coefficient, etc., and has a wide stopband , which can effectively suppress high-frequency spurious signals, is an important direction for the development of today's filters.

Contents of the invention

The invention provides a band-stop microstrip line filter, and the technical scheme is as follows:

The band-stop microstrip line filter includes a substrate, an input transmission line, a zigzag transmission line, an output transmission line, a quarter oval ground plane, and a symmetrical T-shaped coupling line inscribed in a square; a zigzag transmission line is arranged horizontally in the center of the front of the substrate, and There is a quarter oval ground plate at the four corners, one end of the zigzag transmission line is connected to one end of the input transmission line, the other end of the input transmission line is connected to the left end of the substrate, the other end of the zigzag transmission line is connected to one end of the output transmission line, and the other end of the output transmission line is connected to the right end of the substrate ; The back of the substrate is provided with an inscribed symmetrical T-shaped coupling line consisting of 2×9 square inscribed symmetrical T-shaped coupling line units. The square inscribed symmetrical T-shaped unit includes a square ring and two T-shaped coupling lines.

The substrate is made of glass fiber epoxy resin material, the length of the substrate is 150mm-170mm, and the width is 35mm-45mm. The shape and size of the input transmission line and the output transmission line are the same, the length is 8mm-12mm, and the width is 2mm-4mm. The zigzag transmission line is formed by alternately connecting 18 longitudinal microstrip lines and 17 transverse microstrip lines. The strip lines are left-right symmetrical, with a width of 3.5mm-4.5mm and a length of 4mm-12mm. The quarter ellipse grounding plate is a quarter ellipse with a long radius of 45mm-55mm and a short radius of 17mm-19mm. The square inscribed symmetrical T-shaped coupling line is located at the center of the back of the substrate, with a total length of 60 mm to 80 mm and a total width of 15 mm to 20 mm. The distance between the two adjacent left and right square inscribed symmetrical T-shaped units is 1.5mm-2.5mm, and the distance between the upper and lower adjacent square inscribed symmetrical T-shaped units is 4mm-6mm. The total length of the square ring is 5mm-7mm, the total width is 5mm-7mm, and the ring width is 0.4mm-0.8mm. The total length of the T-shaped coupling line is 3 mm to 5 mm, the total width is 2 mm to 2.5 mm, and the line width is 0.4 mm to 0.8 mm.

The invention has the advantages of good filtering performance, simple structure, small size, convenient manufacture and integration.

Description of drawings

Figure 1 is a frontal structural diagram of a bandstop microstrip line filter;

Fig. 2 is the back structure diagram of the band-stop microstrip line filter;

Fig. 3 is a structural diagram of a symmetrical T-shaped unit inscribed in a square;

Fig. 4 is the performance curve diagram of band stop microstrip line filter;

Figure 5 is a surface current distribution diagram of the band-stop microstrip line filter at 5.1 GHz;

Fig. 6 is a surface current distribution diagram of the band-stop microstrip line filter at 5.4 GHz;

Fig. 7 is a surface current distribution diagram of the band-stop microstrip line filter at 5.78 GHz.

Detailed ways

As shown in Figures 1 to 3, the bandstop microstrip line filter includes a substrate 1, an input transmission line 2, a zigzag transmission line 3, an output transmission line 4, a quarter elliptical ground plate 5, and a symmetrical T-shaped coupling line connected in a square 6. There is a zigzag transmission line 3 in the center of the front of the substrate 1, and a quarter oval ground plate 5 is provided at the four corners of the front of the substrate 1. One end of the zigzag transmission line 3 is connected to one end of the input transmission line 2, and the other end of the input transmission line 2 is connected to the substrate 1. The left end is connected, the other end of the zigzag transmission line 3 is connected to one end of the output transmission line 4, and the other end of the output transmission line 4 is connected to the right end of the substrate 1; Connected to the symmetrical T-shaped coupling line 7 , the square inscribed symmetrical T-shaped unit 6 includes a square ring 8 and two T-shaped coupling lines 9 .

The substrate 1 is made of glass fiber epoxy resin material, the length of the substrate 1 is 150mm-170mm, and the width is 35mm-45mm. The shape and size of the input transmission line 2 and the output transmission line 4 are the same, the length is 8mm-12mm, and the width is 2mm-4mm. The zigzag transmission line 3 is formed by alternately connecting 18 longitudinal microstrip lines and 17 transverse microstrip lines. The microstrip line is left-right symmetrical, with a width of 3.5 mm to 4.5 mm and a length of 4 mm to 12 mm. The quarter ellipse grounding plate 5 is a quarter ellipse with a long radius of 45mm-55mm and a short radius of 17mm-19mm. The square inscribed symmetrical T-shaped coupling line 6 is located at the center of the back of the substrate 1, with a total length of 60mm-80mm and a total width of 15mm-20mm. The distance between the two adjacent left and right square inscribed symmetrical T-shaped units 7 is 1.5mm-2.5mm, and the distance between the upper and lower two adjacent square inscribed symmetrical T-shaped units 7 is 4mm-6mm. The total length of the square ring 8 is 5mm-7mm, the total width is 5mm-7mm, and the ring width is 0.4mm-0.8mm. The T-shaped coupling line 9 has a total length of 3 mm to 5 mm, a total width of 2 mm to 2.5 mm, and a line width of 0.4 mm to 0.8 mm.

Example 1

Band stop microstrip line filter:

A glass fiber epoxy resin material with a dielectric constant of 4.4 is selected to make a microstrip substrate with a thickness of 0.5 mm. The substrate has a length of 160 mm and a width of 40 mm. The shape and size of the input transmission line and the output transmission line are the same, the length is 10mm, and the width is 3mm. The zigzag transmission line is formed by alternately connecting 18 vertical microstrip lines and 17 transverse microstrip lines. The length of the transverse microstrip lines is 4mm and the width is 3mm. The longitudinal microstrip lines are left-right symmetrical and the width is 4mm. The length is 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm from both ends to the middle. The quarter ellipse grounding plate is a quarter ellipse with a long radius of 50mm and a short radius of 18mm. A square inscribed symmetrical T-shaped coupling line is located at the center of the backside of the substrate, with a total length of 70mm and a total width of 19mm. The distance between two adjacent square inscribed symmetrical T-shaped units on the left and right is 2 mm, and the distance between two adjacent square inscribed symmetrical T-shaped units on the upper and lower sides is 5 mm. The overall length of the square ring is 6mm, the overall width is 6mm, and the width of the ring is 0.6mm. The total length of the T-shaped coupling line is 4mm, the total width is 2.2mm, and the line width is 0.6mm. Various performance indicators of the band-stop microstrip line filter are tested with CST software, and the performance curve of the obtained filter is shown in Figure 4. It can be seen from the figure that the 3dB passband ranges from 0GHz to 5.1GHz and 5.78GHz to 7.0GHz, the 3dB stopband ranges from 5.1GHz to 5.78GHz, and the maximum insertion loss is -44dB. The insertion loss is small and the return loss is large in these passband ranges, and the insertion loss is large and the return loss is small in the stopband range, which shows that the filter has excellent band-stop filtering performance. Figure 5, Figure 6 and Figure 7 are the surface current distribution diagrams of the band-stop microstrip line filter at 5.1GHz, 5.4GHz and 5.78GHz respectively.

Claims (9)

1. A bandstop microstrip line filter, characterized in that it comprises a substrate (1), an input transmission line (2), a zigzag transmission line (3), an output transmission line (4), a quarter oval ground plate (5 ), a symmetrical T-shaped coupling line (6) inscribed in a square; a zigzag transmission line (3) is arranged horizontally in the center of the front of the substrate (1), and a quarter oval grounding plate (5) is arranged at the four corners of the front of the substrate (1), One end of the zigzag transmission line (3) is connected to one end of the input transmission line (2), the other end of the input transmission line (2) is connected to the left end of the substrate (1), the other end of the zigzag transmission line (3) is connected to one end of the output transmission line (4), and the output transmission line (4) The other end is connected to the right end of the substrate (1); the back of the substrate (1) is provided with an inscribed symmetrical T-shaped coupling line (7) composed of 2×9 square inscribed symmetrical T-shaped coupling line units (6), The square inscribed symmetrical T-shaped unit (6) includes a square ring (8) and two T-shaped coupling lines (9). 2. A bandstop microstrip line filter as claimed in claim 1, characterized in that the substrate (1) is made of glass fiber epoxy resin material, the length of the substrate (1) is 150 mm to 170 mm, and the width is 35mm ~ 45mm. 3. A bandstop microstrip line filter as claimed in claim 1, characterized in that the shape and size of the input transmission line (2) and the output transmission line (4) are the same, the length is 8mm to 12mm, and the width is the same. It is 2mm ~ 4mm. 4. A bandstop microstrip line filter as claimed in claim 1, characterized in that the zigzag transmission line (3) is formed by alternately connecting 18 longitudinal microstrip lines and 17 transverse microstrip lines, The length of the transverse microstrip line is 3.5 mm to 4.5 mm, and the width is 2.5 mm to 3.5 mm. The longitudinal microstrip line is left-right symmetrical, with a width of 3.5 mm to 4.5 mm and a length of 4 mm to 12 mm. 5. A bandstop microstrip line filter as claimed in claim 1, characterized in that the quarter ellipse ground plate (5) is a quarter ellipse with a long radius of 45mm ～55mm, and the short radius is 17mm～19mm. 6. A bandstop microstrip line filter as claimed in claim 1, characterized in that the square inscribed symmetrical T-shaped coupling line (7) is located at the center of the back of the substrate (1), with a total length of 60 mm to 80mm, the total width is 15mm ~ 20mm. 7. A bandstop microstrip line filter as claimed in claim 1, characterized in that the distance between the left and right two adjacent square inscribed symmetrical T-shaped units (6) is 1.5mm-2.5mm, and the upper and lower The distance between two adjacent square inscribed symmetrical T-shaped units (6) is 4 mm to 6 mm. 8. A bandstop microstrip line filter as claimed in claim 1, characterized in that the total length of the square ring (8) is 5 mm to 7 mm, the total width is 5 mm to 7 mm, and the ring width is 0.4 mm ~ 0.8mm. 9. A bandstop microstrip line filter as claimed in claim 1, characterized in that the total length of the T-shaped coupling line (9) is 3 mm to 5 mm, the total width is 2 mm to 2.5 mm, and the line width is 0.4mm～0.8mm.