CN104425860A - Substrate integrated waveguide bandpass filter with wide stop-band characteristic - Google Patents

Abstract

The invention discloses a substrate integrated waveguide bandpass filter with a wide stop-band characteristic. The filter comprises a substrate integrated waveguide and a feed part, wherein the substrate integrated waveguide adopts rectangular substrate integrated waveguide cavities and is commonly defined by a plurality of metal through holes penetrating through a medium substrate and a metal patch on the upper surface of the medium substrate; four rectangular substrate integrated waveguide cavities with the same sizes and a distribution form like the Chinese character 'tian' are formed and comprise a first cavity, a second cavity, a third cavity and a fourth cavity in sequence from the beginning of an input end along the clockwise direction; the output end of the substrate integrated waveguide is connected with the fourth cavity; the feed part comprises a microstrip impedance transition line, an input end, an output end and a coplanar waveguide; the first cavity and the fourth cavity are respectively transited to the microstrip impedance transition lines at corresponding sides through the coplanar waveguide; the microstrip impedance transition lines on the outer sides of the first cavity and the fourth cavity are respectively connected with the input end and the output end. The whole structure of the filter is in an axisymmetric structure about a common side of the second cavity and the third cavity. The filter has the advantages of wide stop-band characteristic and smaller in-band return loss.

Description

A kind of substrate integration wave-guide band pass filter of broad stop-band

One technical field

The present invention relates to the technical field of microwave filter, particularly a kind of substrate integration wave-guide band pass filter of broad stop-band.

Two background technologies

The main way of realization of microstrip filter has lamped element and transmission line type, and the basic structure of transmission line type filter has waveguide, coaxial line, strip line and micro-band etc.The microwave filter of coaxial type has that capability of electromagnetic shielding is good, loss is low and the advantage such as size is little, but there will be the difficulty in the too little processing brought of physical size when operating frequency is higher; Waveguide type microwave filter has the advantage that loss is low, quality factor are high and power capacity is large, but its maximum shortcoming to be size comparatively large, be unfavorable for the miniaturization of system and integrated; In planar circuit, modal microstrip filter has little, the easy processing of size, is easy to the advantage such as integrated with other circuit elements, but its radiation loss is larger.

Substrate integration wave-guide (SIW) is a kind of new waveguiding structure, and it inherits the advantages such as the loss of waveguide is low, quality factor are high, power capacity is large, and low section, the size of also having gathered micro-band be little simultaneously, be easy to the advantage such as integrated with other planar circuits.When adopting substrate integrated waveguide technology to carry out designing filter, compared with the processing cost of traditional waveguide form microwave and millimeter wave device, the processing cost of substrate integration wave-guide microwave and millimeter wave device is very cheap, do not need anything post debugging work, be applicable to very much the Integrated design of microwave and millimeter wave circuit and making in enormous quantities.But owing to often comprising by large metal flat and plated-through hole in SIW structure, himself loss disperses.The substrate integration wave-guide band pass filter of traditional direct cascade, stopband characteristic is undesirable; In order to improve stopband characteristic, increase transmission path by the cross-linked mode of physical structure, but cross-coupled filter complex structure, be not easy to realize.

Three summary of the invention

The object of the present invention is to provide the substrate integration wave-guide band pass filter of a kind of structure broad stop-band that is simple, that easily realize, this filter had both achieved very wide stopband characteristic, had again return loss in very little band simultaneously.

The technical solution realizing the object of the invention is: a kind of substrate integration wave-guide band pass filter of broad stop-band, comprise substrate integration wave-guide and feed part, concrete structure is: cover lower surface metal layer completely at the lower surface of dielectric substrate, is provided with metal patch, co-planar waveguide, micro-band impedance tapered line, input and output at the upper surface of dielectric substrate;

Described substrate integration wave-guide adopts rectangle substrate integrated waveguide chamber, the sidewall that rectangle substrate integrated waveguide chamber is formed by the multiple metal throuth holes through dielectric substrate and upper surface metal patch thereof surrounds jointly, formed four measure-alike and in matrix pattern distribution rectangle substrate integrated waveguide chamber, the first cavity, the second cavity, the 3rd cavity and the 4th cavity is followed successively by along clockwise direction from input position, the wherein long limit of the first cavity and the broadside limit altogether of the second cavity, the long limit of the 4th cavity and the broadside of the 3rd cavity limit altogether, output connects with the 4th cavity; Wherein be equipped with coupling window between the first cavity and the second cavity, between the second cavity and the 3rd cavity, between the 3rd cavity and the 4th cavity;

Described current feed department divides and comprises micro-band impedance tapered line, input, output and the rectangle substrate integrated waveguide chamber co-planar waveguide to micro-band impedance tapered line transition, wherein co-planar waveguide is made up of microstrip line and gap, first cavity and the 4th cavity are respectively by the micro-band impedance tapered line transition of co-planar waveguide to corresponding side, micro-band impedance tapered line outside first cavity connects input, and the micro-band impedance tapered line outside the 4th cavity connects output; The total of this broad stop-band substrate integration wave-guide band pass filter is about the common edge place straight line structure axisymmetricly of the second cavity and the 3rd cavity.

The present invention compared with prior art, its remarkable advantage is: (1) adopts the higher mode in substrate integration wave-guide chamber and being coupled of basement membrane, add transmission path, when not changing this body structure of filter, achieve the cross-couplings of band pass filter, the stopband characteristic that band pass filter is had is very wide; (2) both ensure that the stopband characteristic that filter is wider, return loss in passband can be made again enough little; (3) structure is simple, easily realizes.

Four accompanying drawing explanations

Fig. 1 is the plan structure schematic diagram of the substrate integration wave-guide band pass filter of broad stop-band of the present invention.

Fig. 2 is the S parameter figure of substrate integration wave-guide band pass filter in the embodiment of the present invention.

Five embodiments

Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail.

Composition graphs 1, broad stop-band substrate integration wave-guide band pass filter of the present invention, comprise substrate integration wave-guide 1 and feed part 2, concrete structure is: cover lower surface metal layer completely at the lower surface of dielectric substrate 12, is provided with metal patch 11, co-planar waveguide, micro-band impedance tapered line 23, input 24 and output 25 at the upper surface of dielectric substrate 12;

Described substrate integration wave-guide 1 adopts rectangle substrate integrated waveguide chamber, the sidewall that rectangle substrate integrated waveguide chamber is formed by the multiple metal throuth holes 13 through dielectric substrate 12 and upper surface metal patch 11 thereof surrounds jointly, formed four measure-alike and in matrix pattern distribution rectangle substrate integrated waveguide chamber, the first cavity 15 is followed successively by along clockwise direction from input 24 position, second cavity 16, 3rd cavity 17 and the 4th cavity 18, the wherein long limit of the first cavity 15 and the broadside limit altogether of the second cavity 16, the long limit of the 4th cavity 18 and the broadside of the 3rd cavity 17 limit altogether, output 25 connects with the 4th cavity 18, wherein between the first cavity 15 and the second cavity 16, coupling window 14 is equipped with between the second cavity 16 and the 3rd cavity 17, between the 3rd cavity 17 and the 4th cavity 18,

Described feed part 2 comprises micro-band impedance tapered line 23, input 24, output 25 and the rectangle substrate integrated waveguide chamber co-planar waveguide to micro-band impedance tapered line 23 transition, wherein co-planar waveguide is made up of microstrip line 21 and gap 22, first cavity 15 and the 4th cavity 18 are respectively by micro-band impedance tapered line 23 transition of co-planar waveguide to corresponding side, micro-band impedance tapered line 23 outside first cavity 15 connects input 24, and the micro-band impedance tapered line 23 outside the 4th cavity 18 connects output 25; The total of this broad stop-band substrate integration wave-guide band pass filter is about the common edge place straight line structure axisymmetricly of the second cavity 16 and the 3rd cavity 17.Described micro-band impedance tapered line 23, input 24 and output 25 are the microstrip line that characteristic impedance is 50 Ω.The coupling of employing turning, described rectangle substrate integrated waveguide chamber formula, achieves being coupled of basement membrane and higher mode, adds transmission path, make band pass filter have very wide stopband characteristic by non-physical structure cross-couplings.

The parameter designing process of substrate integration wave-guide band pass filter of the present invention is as follows:

(1), according to centre frequency f ₀determine width W and the length L in rectangle substrate integrated waveguide chamber in substrate integration wave-guide band pass filter, concrete formula is as follows:

$f_0=\frac{c_0}{2\sqrt{{\mathrm{\ϵ}}_r}}\sqrt{\frac{1}{W_{\mathrm{eff}}^2}+\frac{1}{L_{\mathrm{eff}}^2}}$

Wherein,

$W_{\mathrm{eff}}=W-\frac{d^2}{0.95s}$

$L_{\mathrm{eff}}=L-\frac{d^2}{0.95s}$

In formula, f ₀for the centre frequency of filter, W _efffor the equivalent width in rectangle substrate integrated waveguide chamber, W is the developed width in rectangle substrate integrated waveguide chamber, L _efffor the equivalent length in rectangle substrate integrated waveguide chamber, L is the physical length in rectangle substrate integrated waveguide chamber, c ₀for the speed that light is propagated in a vacuum, ε _rfor the dielectric constant of dielectric substrate 12, d is the diameter of metal throuth hole 13, and s is the distance between adjacent metal through hole 13 center of circle; In actual design, in order to reduce variable, the width W of fixed substrate integrated waveguide rectangular cavity;

(2) the transition portion co-planar waveguide between rectangle substrate integrated waveguide chamber and micro-band impedance tapered line 23, is optimized, co-planar waveguide comprises the gap 22 of microstrip line 21 and both sides thereof, wherein co-planar waveguide gap 22 is deep into the external sort factor of the effect length filter in rectangle substrate integrated waveguide chamber, regulates the length in gap 22 just can be met the quality factor of requirement;

(3), optimize micro-band impedance tapered line 23, the impedance in substrate integration wave-guide chamber is mated with 50 Ω input and output micro-strip line impedance in the working band of filter;

(4) after, respectively the transition portion of rectangle substrate integrated waveguide chamber, rectangle substrate integrated waveguide chamber and micro-band impedance tapered line 23 and micro-band impedance tapered line 23 being optimized, finally overall filter be optimized and debug, making its performance requirement meet design objective.

Embodiment 1

Composition graphs 1 substrate integration wave-guide band pass filter of the present invention, devises a centre frequency f ₀for 12.25GHz, bandwidth BW is the substrate integration wave-guide band pass filter of 500MHz, and in band, return loss is less than-20dB, is with outer Insertion Loss to be less than-60dB.The material of dielectric substrate 12 is Roger RT5880, DIELECTRIC CONSTANT ε _r=2.2, dielectric substrate 12 thickness H=0.508mm; Diameter d=the 0.5mm of metal throuth hole 13, the spacing in adjacent metal through hole 13 center of circle is s=1mm.

Fig. 2 is the S parameter figure of substrate integration wave-guide band pass filter of the present invention, and as can be seen from the figure in free transmission range 12GHz ~ 12.5GHz, return loss is less than-20dB; Be with outer Insertion Loss to be less than-60dB, and there is very wide stopband characteristic: within the scope of 4GHz ~ 11GHz and 13.5GHz ~ 17.3GHz, be with outer Insertion Loss to be all less than-60dB.

In sum, substrate integration wave-guide band pass filter of the present invention, under the prerequisite not changing filter physical structure, the main mould adopting substrate integration wave-guide chamber to encourage and the coupling of higher mode increase transmission path, realize the cross-couplings of non-physical structure, make filter have very wide stopband characteristic; This filter physical structure does not need to change, and form passband by the cascade of rectangle substrate integrated waveguide chamber, the cascade of turning formula achieves the coupling of higher mode, has both achieved very wide stopband characteristic, has again return loss in enough little band simultaneously.

Claims (4)

1. the substrate integration wave-guide band pass filter of a broad stop-band, it is characterized in that, comprise substrate integration wave-guide (1) and feed part (2), concrete structure is: cover lower surface metal layer completely at the lower surface of dielectric substrate (12), is provided with metal patch (11), co-planar waveguide, micro-band impedance tapered line (23), input (24) and output (25) at the upper surface of dielectric substrate (12);

Described substrate integration wave-guide (1) adopts rectangle substrate integrated waveguide chamber, the sidewall that rectangle substrate integrated waveguide chamber is formed by the multiple metal throuth holes (13) through dielectric substrate (12) and upper surface metal patch (11) thereof surrounds jointly, formed four measure-alike and in matrix pattern distribution rectangle substrate integrated waveguide chamber, the first cavity (15) is followed successively by along clockwise direction from input (24) position, second cavity (16), 3rd cavity (17) and the 4th cavity (18), the wherein long limit of the first cavity (15) and the broadside limit altogether of the second cavity (16), the long limit of the 4th cavity (18) and the broadside of the 3rd cavity (17) limit altogether, output (25) connects with the 4th cavity (18), wherein be equipped with coupling window (14) between the first cavity (15) and the second cavity (16), between the second cavity (16) and the 3rd cavity (17), between the 3rd cavity (17) and the 4th cavity (18),

Described feed part (2) comprises micro-band impedance tapered line (23), input (24), output (25), and rectangle substrate integrated waveguide chamber is to the co-planar waveguide of micro-band impedance tapered line (23) transition, wherein co-planar waveguide is made up of microstrip line (21) and gap (22), first cavity (15) and the 4th cavity (18) are respectively by micro-band impedance tapered line (23) transition of co-planar waveguide to corresponding side, micro-band impedance tapered line (23) in the first cavity (15) outside connects input (24), micro-band impedance tapered line (23) in the 4th cavity (18) outside connects output (25), the total of the substrate integration wave-guide band pass filter of this broad stop-band is about the common edge place straight line structure axisymmetricly of the second cavity (16) and the 3rd cavity (17).

2. the substrate integration wave-guide band pass filter of broad stop-band according to claim 1, is characterized in that, the width W in described rectangle substrate integrated waveguide chamber and length L, determines according to following formula:

$f_0=\frac{c_0}{2\sqrt{{\mathrm{\ϵ}}_r}}\sqrt{\frac{1}{W_{\mathrm{eff}}^2}+\frac{1}{L_{\mathrm{eff}}^2}}$

Wherein,

$W_{\mathrm{eff}}=W-\frac{d^2}{0.95s}$

$L_{\mathrm{eff}}=L-\frac{d^2}{0.95s}$

In formula, f ₀for the centre frequency of filter, W _efffor the equivalent width in rectangle substrate integrated waveguide chamber, W is the developed width in rectangle substrate integrated waveguide chamber, L _efffor the equivalent length in rectangle substrate integrated waveguide chamber, L is the physical length in rectangle substrate integrated waveguide chamber, c ₀for the speed that light is propagated in a vacuum, ε _rfor the dielectric constant of dielectric substrate (12), d is the diameter of metal throuth hole (13), and s is the distance between adjacent metal through hole (13) center of circle.

3. the substrate integration wave-guide band pass filter of broad stop-band according to claim 1, is characterized in that, employing turning, described rectangle substrate integrated waveguide chamber formula is coupled.

4. the substrate integration wave-guide band pass filter of broad stop-band according to claim 1, is characterized in that, described micro-band impedance tapered line (23), input (24) and output (25) are the microstrip line that characteristic impedance is 50 Ω.