CN201178125Y - Substrate-integrated waveguide dual-mode elliptic response filter - Google Patents

Abstract

The substrate integrated waveguide dual-mode elliptic response filter adopts two dual-mode single cavities with different sizes, and the upper surface metal layer (7) and the lower surface metal layer ( 8), the metallized through hole array (2) runs through the dielectric substrate (1), the upper surface metal layer (7) and the lower surface metal layer (8), and is surrounded by the metallized through hole array (2) to form a rectangular structure The cavity (3) is provided with a first inductive coupling hole (61) and a second inductive coupling hole (62) on opposite sides of the cavity (3) of a rectangular structure to introduce energy into and out of the cavity; the first metal The metallized through-hole array (4) and the second metallized through-hole array (5) are respectively arranged outside the first inductive coupling hole (61) and the second inductive coupling hole (62), corresponding to the input and output of the filter cavity , two collinear distributions, they are connected to external circuits, and can be connected to microstrip lines or other substrate integrated waveguide devices.

Description

Substrate-integrated waveguide dual-mode elliptic response filter

technical field

The utility model relates to a millimeter wave filter, which is realized by a Substrate Integrated Waveguide (SIW) dual-mode cavity, has the characteristics of an elliptical response, and is especially suitable for high frequency, low loss, high integration, and Applications with higher requirements on selectivity.

Background technique

The filter is one of the important basic unit circuits of the circuit system, and its performance has an important impact on the overall selectivity, noise figure, gain, and sensitivity of the system. Commonly used in microwave and millimeter wave circuits are filters based on metal waveguides and filters based on planar circuits such as microstrip lines and coplanar lines. Filters based on metal waveguides usually have the advantages of high Q value, low loss, and good selectivity, but they require high processing precision, high cost, large volume, and are difficult to integrate with active circuits. Although filters based on planar circuit technologies such as microstrip lines and coplanar lines are easy to integrate with active circuits, they usually have large radiation, large losses, low Q values, and poor performance. Substrate integrated waveguide technology has the advantages of easy integration and convenient fabrication of planar circuits, and has excellent performance similar to metal waveguide filters. Due to the limited spectrum resources, modern communication systems put forward higher and higher requirements on the selectivity of filters. Elliptic response filters are undoubtedly a preferred choice. A common way to implement an elliptic filter is to use cross-coupling, which creates transmission zeros. However, this method is complex in design and difficult to implement.

Contents of the invention

Technical problem: The purpose of this utility model is to propose a substrate-integrated waveguide dual-mode elliptic response filter, which uses substrate-integrated waveguide technology, a single-layer structure, simple processing, small volume, and high integration. , it uses a rectangular dual-mode cavity to achieve elliptical response, with relatively small insertion loss, excellent performance, and convenient design.

Technical solution: The utility model provides a dual-mode cavity filter with elliptic response, which is mainly based on substrate integrated waveguide technology and dual-mode theory, and is very suitable for application in the millimeter wave field.

The utility model adopts the following technical solutions:

The dual-mode cavity elliptic response filter uses two dual-mode single cavities with different sizes to obtain an elliptic response with bilateral steep drops, and each single cavity contributes a zero point and two poles; each single cavity uses a chip Integrated waveguide technology, the upper and lower surfaces of the dielectric substrate are coated with an upper surface metal layer and a lower surface metal layer respectively, and the array of metallized through holes runs through the dielectric substrate, the upper surface metal layer and the lower surface metal layer, and the metallization The through-hole array encloses a cavity with a rectangular structure, and a first inductive coupling hole and a second inductive coupling hole are respectively provided on opposite sides of the rectangular-structured cavity to introduce energy into and out of the cavity; the first metallized through-hole array and the second metallized through hole array are respectively arranged outside the first inductive coupling hole and the second inductive coupling hole, corresponding to the input and output of the filter cavity, the two are collinearly distributed, and they are connected to the external circuit, which can be Connect to microstrip lines or other substrate-integrated waveguide devices. The size and structure of the cavity of the rectangular structure, including length and width, aspect ratio, can independently control the positions of the zero point and the pole point of the filter, which brings great convenience to the design.

For the case where the transmission zero point is on the left, the width a of the first inductive coupling hole is 2.62 mm, and the width b of the second inductive coupling hole is 4.587 mm. For the case where the transmission zero point is on the left, the width a of the first inductive coupling hole is 2.62 mm, and the width b of the second inductive coupling hole is 4.587 mm.

For the case where the transmission zero point is on the left, the long side width of the cavity of the rectangular structure is 10.46 mm, and the short side length is 5.51 mm. For the case where the transmission zero point is on the right, the long side width of the cavity of the rectangular structure is 9.76mm, and the short side length is 5.73mm.

The diameter vr of the metallized through hole is 0.3 mm, and the distance vs of adjacent through holes is 0.6 mm. The dielectric thickness is 0.5mm and the dielectric constant is 2.2.

Beneficial effect:

1. The filter has good elliptic response characteristics, good selectivity, and relatively symmetrical upper and lower sideband responses.

2. The filter has a small insertion loss and adopts a dual-mode structure. Only two cavities are used to achieve four poles and two controllable zeros, while the traditional cross-coupled elliptic response cavity filter achieves The same performance requires four cavities, resulting in greater insertion loss. Compared with the main mode, the filter cavity has a larger unloaded quality factor, so the loss can be further reduced.

3. The filter adopts a single-layer substrate integrated waveguide structure, which is very simple to implement. It is produced using mature standard industrial processes, with low cost and high precision, and is easy to integrate with active planar circuits. Compared with metal waveguide filters Words are a great advantage.

4. The design of the filter is very simple. The two dual-mode cavities can be designed independently, and the pole and zero point are controlled by the cavities separately, which avoids the complicated design process of the cross-coupled elliptic filter.

5. The upper and lower surfaces of the filter are connected by metallized holes, which is convenient for grounding and isolation, and it is easy to achieve complete isolation between input and output. Using the substrate-integrated waveguide cavity as a resonator basically eliminates radiation loss, and the filter loss is much lower than that of filters based on microstrip and coplanar lines.

Description of drawings

Figure 1 is a single-cavity structural diagram of a substrate-integrated waveguide dual-mode filter, where Figure 1(a) is a front view and Figure 1(b) is a side view.

Figure 2 is a single-cavity transmission characteristic and mode electric field diagram of a substrate-integrated waveguide dual-mode filter, and a diagram illustrating cavity dimensions.

FIG. 3 is a structural diagram of a two-cavity dual-mode filter in Embodiment 1. FIG.

Fig. 4 is a diagram of the transmission characteristic of the filter of the implementation example, wherein the dotted line is the test result, and the solid line is the simulation result.

In the above figure, there are: a dielectric substrate 1, an array of metallized through holes 2, a cavity 3 with a rectangular structure, a first array of metallized through holes 4, a second array of metallized through holes 5, a first inductive coupling hole 61, The second inductive coupling hole 62 , the upper surface metal layer 7 , and the lower surface metal layer 8 .

Detailed ways

The dual-mode cavity elliptic response filter uses two dual-mode single cavities with different sizes to obtain an elliptic response with bilateral steep drops, and each single cavity contributes one zero point and two poles. The structure of the single cavity is shown in Figure 1. It adopts the substrate integrated waveguide technology, including the dielectric substrate 1, the upper surface metal layer 7 and the lower surface metal layer 8 coated on the upper and lower surfaces of the dielectric substrate 1, and the The metallized through-hole array 2 of the upper surface metal layer 7 and the lower surface metal layer 8 of the upper and lower metal surfaces. The cavity 3 with a rectangular structure is a standard rectangular structure, and the first inductive coupling hole 61 and the second inductive coupling hole 62 lead energy into and out of the cavity. The first metallized through-hole array 4 and the second metallized through-hole array 5 correspond to the input and output of the filter cavity respectively, and the two are collinearly distributed, and they are connected to external circuits, which can be connected to microstrip lines or Other substrates integrate waveguide devices, and the through-hole array can also suppress the entry of low-order modes. The modes used in this filter are TE ₁₀₃ mode and TE ₂₀₁ mode. Figure 2 shows the transmission characteristics of a single cavity and the electric field diagram of the mode used. The input and output of the TE ₁₀₂ memetic filter are distributed in a straight line and are located at the zero electric field of the mode, which can be well suppressed. By properly adjusting the size of the cavity, the transmission zero point can be easily moved to the upper sideband or the lower sideband, and the zero and pole points can be independently controlled by the cavity.

The actual design of the filter is shown in Figure 3. The dual-mode cavity 31 shown in FIG. 1 , the microstrip and its gradient line 32 for testing or connected to the external circuit, and the inductive aperture coupling window 33 . The whole filter is composed of two rectangular dual-mode cavity lines arranged in a straight line, which is relatively small. Except for the microstrip line and its gradient line for testing, the filter itself is very small. The substrate is Rogers5880 with a dielectric constant of 2.2 and a thickness of 0.5mm. Two different cavities are responsible for one out-of-band transmission zero and two in-band poles, which is convenient for debugging. The measured transmission characteristics of the filter are shown by the dotted line in Figure 4. The measured return loss is better than -11.5dB, and the in-band insertion loss is about 2.92dB. This loss includes the influence of the test connector, microstrip feeder and gradient line. These losses are quite obvious in the Ka band. After deducting this part of the loss, the actual loss of the filter will be smaller, which should be less than 2dB. The center frequency of the designed filter is 35 GHz, and the measured bandwidth is about 2 GHz. It can be found that the test results are in good agreement with the simulation results. The main difference is that the bandwidth is a bit larger, which should be caused by the inaccurate positioning of the cavity hole on the left. The selectivity of the filter is very good, and it quickly drops below -20dB, which is a typical characteristic of an elliptic filter.

Claims (3)

1. A substrate-integrated waveguide dual-mode elliptic response filter is characterized in that the dual-mode cavity elliptic response filter uses two different dual-mode single cavities in size to obtain the elliptic response of bilateral steep drop, each The single cavity contributes a zero point and two poles; each single cavity adopts the chip integrated waveguide technology, and the upper surface metal layer (7) and the lower surface metal layer ( 8), the metallized through hole array (2) runs through the dielectric substrate (1), the upper surface metal layer (7) and the lower surface metal layer (8), and is surrounded by the metallized through hole array (2) to form a rectangular structure The cavity (3) is provided with a first inductive coupling hole (61) and a second inductive coupling hole (62) on opposite sides of the cavity (3) of a rectangular structure to introduce energy into and out of the cavity; the first metal The metallized through-hole array (4) and the second metallized through-hole array (5) are respectively arranged outside the first inductive coupling hole (61) and the second inductive coupling hole (62), corresponding to the input and output of the filter cavity , two collinear distributions, they are connected to external circuits, and can be connected to microstrip lines or other substrate integrated waveguide devices. 2. substrate integrated waveguide dual-mode elliptic response filter according to claim 1, it is characterized in that the width a of the first inductive coupling hole (61) is 2.62mm, the width b of the second inductive coupling hole (62) is 4.587mm. 3. The substrate-integrated waveguide dual-mode elliptic response filter according to claim 1, characterized in that the diameter vr of the metallized through-hole array (2) is 0.3 mm, and the spacing vs of adjacent through-holes is 0.6 mm.

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