CN104934662A - Substrate integrated waveguide ferrite tunable band-pass filter - Google Patents

Abstract

The invention belongs to the technical field of adjustable filters, and relates to an adjustable bandpass filter based on substrate integrated waveguide ferrite, which includes an upper metal copper clad layer, a dielectric layer, a narrow side metallized through hole, a lower metal copper clad layer, Central inductive metallized through hole; wherein, the dielectric substrate and the upper metal copper clad layer are sequentially arranged on the lower metal copper clad layer, and the upper metal copper clad layer and the lower metal copper clad layer are connected by two rows of narrow side metallized through holes parallel to each other , forming a substrate integrated waveguide together with the dielectric layer; a row of central inductive metallized through holes is opened in the center of the substrate integrated waveguide, and it is characterized in that, in the dielectric layer, adjacent to the two rows of narrow edge metallized through holes are respectively The ferrite block is embedded and arranged, and the upper and lower surfaces of the ferrite block are metallized, and are connected and conducted with the upper and lower metal clad copper layers. The invention realizes the ferrite-loaded substrate integrated waveguide adjustable bandpass filter, so as to meet the requirement of the adjustable bandpass filter in the substrate integrated system.

Description

A Substrate Integrated Waveguide Ferrite Tunable Bandpass Filter

technical field

The invention belongs to the technical field of adjustable filters, in particular to a ferrite adjustable band-pass filter based on substrate integrated waveguide technology.

Background technique

The concept of substrate integrated circuits based on ordinary printed circuit board (PCB) technology has been greatly developed since it was proposed in 2000, and the most concerned one is substrate integrated waveguide technology. In recent years, on the basis of sufficient research on the transmission characteristics of substrate integrated waveguide structures, magnetron devices such as ferrite tunable filters based on substrate integrated waveguide technology have been realized, which has greatly promoted the development of substrate integrated waveguide technology. new development. Currently, reconfigurability and miniaturization are the main development directions of filters.

The traditional waveguide tunable bandpass filter is large in size, complex in processing, high in cost, and difficult to integrate with planar circuits. Band-pass filters can be divided into two types as a whole: electric modulation type and magnetic modulation type. The ESC type mainly uses the varactor to load the bandpass filter, and controls the filter operating frequency by controlling the voltage at both ends of the varactor. However, subject to the operating frequency and power capacity of the varactor, the ESC can It is difficult for the tuned filter to work to a very high frequency; the magnetic tuned type mainly uses ferrite to load the bandpass filter, and the filter operating frequency is changed by changing the DC bias added to the ferrite, because the ferrite belongs to A type of material with low high-frequency loss, the magnetically modulated tunable filter can achieve very high frequencies.

Currently, the literature "Simultaneous electric and magnetic two-dimensionally tuned parameter-agile SIW devices," (S.Adhikari, A.Ghiotto, and K.Wu, IEEE Trans.Microw.Theory Tech.,vol.61,no.1,pp .423-435, Jan.2013.) It is disclosed that the substrate integrated waveguide tunable bandpass filter is realized by jointly loading ferrite and varactor to control the resonant cavity frequency. Its working principle is to change the resonant frequency of the resonant cavity by changing the applied DC magnetic bias, and at the same time adjust the resonant frequency of the resonant cavity by changing the voltage across the varactor, and then realize the working frequency range of the bandpass filter through the coupling between the resonant cavities. Change. Although this structure realizes the adjustable frequency of the filter, it requires the joint control of DC bias and voltage, that is, the combination of electric control and magnetic control, the structure is complex, and because the substrate integrated waveguide is an equipotential body, the bias voltage cannot be directly applied , requires an additional separate circuit for voltage control.

Literature "Magnetically Tunable Ferrite-Loaded Half-Mode Substrate Integrated Waveguide" (S.Adhikari, S.Hemour, A.Ghiotto, and K.Wu, IEEE Micro.Wireless Comp. Lett., vol.25, no.3, pp. 172-174, March 2015." Publication of substrate-integrated waveguide tunable band-pass filter uses ferrite and lumped capacitors loaded on the half-mode substrate-integrated waveguide to realize band-pass filter bandwidth adjustable, but there are the following problems: 1) The half-mode substrate integrated waveguide filter is a semi-open structure, which is easily interfered by other signals in the circuit and has poor electromagnetic compatibility; 2) It only realizes the adjustable bandwidth, and does not realize the adjustment of the operating frequency under the same bandwidth; 3 ) The adjustment of the capacitance value needs to replace the capacitance, which is not feasible in actual use.

At present, there is no suitable solution for the design of ferrite-loaded tunable bandpass filters based on substrate-integrated waveguides.

Contents of the invention

The object of the present invention is to provide a ferrite tunable bandpass filter based on substrate integrated waveguide, realize ferrite loaded substrate integrated waveguide tunable bandpass filter, to meet the requirement of adjustable bandpass filter in substrate integrated system pass filter requirements. In order to achieve the above object, technical scheme of the present invention is:

A substrate-integrated waveguide ferrite tunable bandpass filter, comprising an upper metal copper-clad layer 1, a dielectric layer 3, narrow-side metallized through-holes 4, a lower metal-clad copper layer 5, and a central inductive metallized through-hole 6 Wherein, the dielectric substrate 3 and the upper metal copper layer 1 are sequentially arranged on the lower metal copper layer 5, and the upper metal copper layer 1 and the lower metal copper layer 5 are connected through two rows of narrow-side metallized through holes 4 parallel to each other. conduction, together with the dielectric layer 3 to form a substrate integrated waveguide; a row of central inductive metallized through holes 6 is opened in the center of the substrate integrated waveguide, and it is characterized in that the dielectric layer 3 is close to the two rows of narrow sides The metallized through holes 4 are respectively embedded with ferrite blocks 2 , and the upper and lower surfaces of the ferrite blocks 2 are metallized and connected to the upper and lower metal copper clad layers.

Further, the surface of the ferrite block 2 adjacent to the narrow side metallized through hole is metallized, thereby replacing the narrow side metallized through hole at its corresponding position.

Further, the length of the ferrite block 2 is greater than or equal to the total length of the central inductive metallized through-holes 6 , that is, the distance between the two farthest through-holes in the central inductive metallized through-holes.

It should be noted that the above-mentioned ferrite block 2 is located close to the narrow-side metallized through hole 4 , and "close to" refers to being as close as possible within the range allowed by the processing technology, but not connected.

In the present invention, the ferrite tunable bandpass filter is mainly made of the magnetic anisotropy when the electromagnetic wave propagates in the ferrite, that is, by changing the magnitude of the external DC magnetic bias, the ferrite loaded in the substrate integrated waveguide The relative magnetic permeability of ferrite will change accordingly, which will cause the cut-off frequency of the substrate integrated waveguide loaded with ferrite to change, and the coupling of the middle row of metal through holes will cause the filter's working frequency band to change.

Beneficial effects of the present invention:

The present invention combines substrate integrated waveguide technology with ferrite materials to design a ferrite adjustable bandpass filter, which is cheaper than traditional metal waveguide ferrite bandpass filters, and is easy to planarize and integrate At the same time, compared with the existing substrate-integrated waveguide band-pass filter, when achieving a considerable adjustment of the working frequency band, the working frequency band of the band-pass filter can be controlled only by applying a DC magnetic bias, without the need to apply a bias at the same time Pressure control varactor. In addition, since lumped capacitor elements are not used, the filter is not limited by the operating frequency and rated power of these elements, so the filter can be designed to a higher frequency and be applied to a higher power. The main advantages are as follows:

(1) The present invention provides a ferrite tunable bandpass filter based on a substrate-integrated waveguide. Compared with traditional metal waveguide-type tunable bandpass filters and common substrate-integrated waveguide tunable bandpass filters, the former is retained. While the power capacity is large, the working frequency band is higher than the latter, and the power capacity is larger;

(2) Compared with the ordinary ferrite embedded substrate integrated waveguide tunable filter, since the present invention mainly relies on the external magnetic bias to adjust the working frequency band of the filter, it does not need to control the bias voltage at the same time, and in the planarized circuit Easier to integrate.

Description of drawings

Fig. 1 is a three-dimensional schematic diagram of the structure of a substrate-integrated waveguide ferrite tunable bandpass filter in Embodiment 1;

Figure 2 is a cross-sectional schematic diagram of the structure in Figure 1; where, 1 is the upper metal copper clad layer, 2 is the three-sided metallized ferrite block, 3 is the dielectric layer, 4 is the narrow side metallized through hole, and 5 is the lower metal clad copper Layer 6 is the central inductive metallized through hole.

Fig. 3 is a top view of the structure of the substrate-integrated waveguide ferrite tunable bandpass filter in Embodiment 2.

Fig. 4 is a schematic cross-sectional view of the structure in Fig. 3; wherein, 7 is a metallized ferrite block on both sides.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments and accompanying drawings.

The operating frequency band of the ferrite tunable bandpass filter based on the substrate integrated waveguide provided in the present invention mainly depends on the width of the substrate integrated waveguide and the diameter and spacing of a row of metal through holes in the center. Its specific design steps:

1) Select the substrate material, and select the appropriate substrate integrated waveguide width (two rows of narrow-side metallized through holes 4 spacing) according to the filter operating frequency band;

2) According to the formula:

$\frac{1+\cos [2\mathrm{\π}{f}_c(W_2-2W_f)\sqrt{{\mathrm{\μ}}_{\mathrm{the\; s}}{\mathrm{\ϵ}}_{\mathrm{the\; s}}}}{1-\cos [2\mathrm{\π}{f}_c(W_2-2W_f)\sqrt{{\mathrm{\μ}}_{\mathrm{the\; s}}{\mathrm{\ϵ}}_{\mathrm{the\; s}}}}=\left(\frac{\left|{\mathrm{\μ}}_f\right|{\mathrm{\ϵ}}_{\mathrm{the\; s}}}{{\mathrm{\μ}}_{\mathrm{the\; s}}{\mathrm{\ϵ}}_f}\right)\mathrm{the\; tan}{h}^2\left[2\mathrm{\π}{f}_c{W}_f\sqrt{\left|{\mathrm{\μ}}_f{\mathrm{\ϵ}}_f\right|}\right],$ Among them, f _c is the cut-off frequency, W _f is the width of the ferrite block, W ₂ is the width of the substrate integrated waveguide, μ _s and ε _s are the cut-off substrate permeability and permittivity, respectively; μ _f and ε _f are respectively Ferrite effective permeability and permittivity;

Determine the cut-off frequency of the substrate-integrated waveguide loaded with ferrite, and then calculate the equivalent dielectric constant of the substrate-integrated waveguide. The width of the ferrite block should be as wide as possible to ensure a wide adjustable frequency band, but it should not greater than twice the diameter of the narrow side metallized through hole 4;

3) Reasonably select the number of central inductive metallized through holes 6 according to the isolation degree of the bandpass filter to be designed. The more the number of through holes 6, the better the isolation degree, but at the same time the insertion loss will increase accordingly:

4) Determine the hole spacing of the central inductive metallized through hole 6, the initial value of the spacing is λ _g /2, λ _g is the wavelength of the substrate integrated waveguide waveguide, and the specific value is further appropriately optimized;

5) Determine the equivalent lumped parameter value required by the filter by the bandwidth of the bandpass filter to be designed, and then determine the diameter of the central inductive metallized through hole 6 by the classic metallized through hole equivalent circuit model; in general , this structure mainly realizes the adjustable bandpass filter design by first selecting the number of central inductive metallized through holes 6, then determining the size of the ferrite block to be loaded, and finally selecting the diameter of the inductive metallized through holes 6.

Example 1

As shown in Fig. 1 and Fig. 2, the substrate-integrated waveguide ferrite tunable bandpass filter in this embodiment includes a metal-clad copper upper layer 1 and three sides (close to the outer side of the substrate-integrated waveguide narrow edge and the upper and lower surfaces ) Metallized ferrite block 2, dielectric substrate 3, narrow-side metallized through hole 4, metal copper clad lower layer 5, central inductive metallized through hole 6; substrate integrated waveguide consists of metal clad copper upper layer 1 and metal clad copper The lower layer 5 is connected to each other through two rows of parallel narrow-side metallized through holes 4, and is formed together with the corresponding dielectric substrate 3; The side is embedded with three-sided metallized ferrite blocks 2, and the outer surfaces of the two ferrite blocks 2 are respectively close to the two rows of narrow-side metallized through holes 4 axis positions, according to the dielectric constant of the dielectric substrate and ferrite used The position of the ferrite block can be adjusted appropriately, but the length of the ferrite block 2 should not be less than the distance between the two farthest central inductive metallized through holes 6; The vias are then replaced. In addition, the relatively long ferrite blocks on both sides can be changed into multiple pieces, so that the ferrite is easier to process and less likely to be damaged during assembly.

As an example, the substrate-integrated waveguide ferrite tunable bandpass filter of this structure is designed as follows: the dielectric constant of the selected dielectric substrate is 2.2, the thickness is 0.508mm, and the loss tangent is 0.0009; the ferrite sheet is YIG-1850, relative permittivity 14.5, 3dB line width 20Oe, loss tangent 0.0002, saturation magnetization 1850Gs; substrate integrated waveguide width 11.2mm, narrow side metallized through-hole diameter 0.6mm, through-hole spacing 1.2mm; center The diameters of the inductive metallized through holes 6 are 0.6 mm and 2 mm respectively, and the distances between the through holes L1 = 11.6 mm and L2 = 10.4 mm; the thickness of the ferrite block is 0.508 mm, the length is 34 mm, and the width is 1 mm. When the applied DC magnetic bias increases gradually from 0T to 0.2T, the operating frequency of the band-pass filter changes from 12.5GHz to 13.4GHz. The insertion loss is less than 1.6dB, and the return loss is better than 15dB.

Example 2

As shown in Fig. 3 and Fig. 4, the substrate integrated waveguide ferrite tunable bandpass filter in this embodiment includes a metal-clad copper upper layer 1, a ferrite block 7 metallized on the upper and lower surfaces, and a dielectric substrate 3. Narrow side metallized through hole 4, metal copper clad lower layer 5, central inductive metallized through hole 6; the substrate integrated waveguide is composed of metal copper clad upper layer 1 and metal copper clad lower layer 5 through two rows of metallized through holes parallel to each other 4 are connected together and constituted together with the corresponding dielectric substrate 3; the center of the substrate integrated waveguide dielectric layer 3 is a central inductive metallized through hole 6, and the two sides of the substrate integrated waveguide are embedded with metallized ferrite blocks 7 on the upper and lower surfaces. The outer side of the ferrite block 7 should be as close as possible to the narrow side metallized through hole 4 if the processing technology allows.

This design structure does not need to metallize the side of the ferrite. In actual processing, the ferrite block can be embedded in the dielectric substrate first, and then the upper surface is covered with copper as a whole, which reduces the processing complexity; In this filter design, the ferrite block will be relatively small, and it is more difficult to metallize it at this time, so this structure is especially beneficial in high frequency bands.

The above is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless specifically stated, can be replaced by other equivalent or alternative features with similar purposes; all the disclosed features, or All method or process steps may be combined in any way, except for mutually exclusive features and/or steps.

Claims (3)

1. a substrate integration wave-guide ferrite variable band-pass filter, comprises metal copper clad layers (1), dielectric layer (3), narrow limit plated-through hole (4), lower metal copper clad layers (5), center perception plated-through hole (6); Wherein, lower metal copper clad layers (5) sets gradually dielectric layer (3) and upper metal copper clad layers (1), upper metal copper clad layers (1) is arranged by two narrow limit plated-through hole (4) be parallel to each other with lower metal copper clad layers (5) and is connected, forms substrate integration wave-guide together with dielectric layer (3); Form substrate integration wave-guide center offer one row center perception plated-through hole (6), it is characterized in that, embed respectively near described two rows narrow limit plated-through hole (4) in described dielectric layer (3) and be provided with ferrite block (2), the upper and lower surface metalation of ferrite block (2), is connected conducting with upper and lower metal copper clad layers.

2., by substrate integration wave-guide ferrite variable band-pass filter described in claim 1, it is characterized in that, described ferrite block (2) near plated-through hole side, narrow limit surface metalation, and then replaces the narrow limit plated-through hole of its corresponding position.

3. by substrate integration wave-guide ferrite variable band-pass filter described in claim 1,2, it is characterized in that, the length of described ferrite block (2) is more than or equal to the total length at center perception plated-through hole (6).