CN101667672A - Substrate integrated waveguide directional filter - Google Patents

Abstract

The invention relates to a substrate integrated waveguide directional filter, in particular to a combining filter which can be applied to the design of microwave and millimeter wave monolithic circuits and microwave and millimeter wave integrated circuits. The filter is widely applied in microwave and millimeter wave wireless communication systems, satellite communication systems, test instrumentation systems and the like. An upper layer metal copper-clad surface (1) and a lower layer metal copper-clad surface (2) of the filter are respectively arranged at the front side and the reverse side of a medium substrate (3); a plated-though-hole (4) is connected with the upper layer metal copper-clad surface (1) and the lower layer metal copper-clad surface (2) after passing through the medium substrate (3) to form a first substrate integrated waveguide directional coupler (51), a second substrate integrated waveguide directional coupler (52), a third substrate integrated waveguide directional coupler (53), a first substrate integrated waveguide loop (61) and a second substrate integrated waveguide loop (62), thereby enabling the filter to be directly integrated with a radio-frequency circuit. The filter has the characteristics of low insertion loss, high selectivity characteristic, low processing cost, feasible mass production and the like.

Description

Substrate integrated waveguide directional filter

Technical field

The present invention relates to a kind of combining filter that can be applicable to microwave and millimeter wave monolithic integrated circuit, microwave and millimeter wave integrated circuit (IC) design, it has a wide range of applications in systems such as microwave and millimeter wave radio communication, satellite communication, electronic countermeasures, test instrumentation.

Background technology

The microwave combining filter is to be used for handle covers separately becomes a few frequency ranges with the signal spectrum of big frequency range microwave device.The main performance index of Microwave Multiplexer is channel isolation and channel differential loss.The design problem of multiplexer is the problem that often runs in the microwave engineering, and at first glance, little as difficulty, directly linking together with some band pass filters gets final product.But in fact, because the interaction between the filter can make the device performance variation, until not working.

Directional filter is one four port devices, remains the good isolation degree between two input ports.When signal when an input port enters, the frequency response characteristic of an output port is a band pass filter, the frequency response characteristic of another one output port is a band stop filter.In various directional filters, a class that is fit to the planar circuit design and has a better performance is the loop directional filter.This directional filter is made of the loop of several directional couplers and integral multiple wavelength.Each loop is a toroidal cavity resonator, and resonance frequency is needed operating frequency.Increase the number in loop, can improve the selectivity of directional filter, but be cost with the insertion loss that increases directional filter; With the direct cascade of a plurality of directional filters, the good isolation degree makes does not almost have influence between them, can realize high performance multiplexer.

Substrate integration wave-guide not only has the circuit structure of complanation, has the characteristic of low-loss, low-cross coupling, high Q value simultaneously, therefore can be used for designing high performance directional filter.

Summary of the invention

Technical problem: the objective of the invention is to utilize directional filter of substrate integration wave-guide design, make it can be directly mutually integrated, have low insertion loss, high selectivity characteristic, hang down processing cost, be easy to characteristics such as production in enormous quantities with radio circuit.

Technical scheme: substrate integrated waveguide directional filter of the present invention is the double loop directional filter, comprise that the upper strata metal applies copper face, lower metal applies the positive and negative both sides that copper face lays respectively at dielectric substrate, plated-through hole passes dielectric substrate and is connected and forms first substrate integrated waveguide directioning coupler, second substrate integrated waveguide directioning coupler, the 3rd substrate integrated waveguide directioning coupler, the first substrate integration wave-guide loop, the second substrate integration wave-guide loop with the deposited copper face of upper strata metal, the deposited copper face of lower metal; Wherein, the first substrate integration wave-guide loop, the second substrate integration wave-guide loop are respectively the rectangle that is surrounded by plated-through hole, the centre and the outside in the first substrate integration wave-guide loop, the second substrate integration wave-guide loop are respectively equipped with two row's plated-through holes, between the row's plated-through hole of first substrate integrated waveguide directioning coupler two outside the first substrate integration wave-guide loop and in first substrate integration wave-guide loop; Between the row's plated-through hole of second substrate integrated waveguide directioning coupler two in the first substrate integration wave-guide loop and in second substrate integration wave-guide loop; Between the row's plated-through hole of the 3rd substrate integrated waveguide directioning coupler two in the second substrate integration wave-guide loop and outside second substrate integration wave-guide loop; First delivery outlet that first input port of substrate integrated waveguide directioning coupler connects substrate integrated waveguide directional filter first input end mouth, substrate integrated waveguide directioning coupler connects first output port of substrate integrated waveguide directional filter, first input port of substrate integrated waveguide directioning coupler connects substrate integrated waveguide directional filter second input port, and second delivery outlet of substrate integrated waveguide directioning coupler connects second output port of substrate integrated waveguide directional filter.

The centerline length in the first substrate integration wave-guide loop and the second substrate integration wave-guide loop should be the integral multiple of the guide wavelength of substrate integration wave-guide; Each 90 ° of corner in the first substrate integration wave-guide loop and the second substrate integration wave-guide loop are equipped with a perceptual Metallic rod to realize good coupling.

The first input end mouth and second input port remain good isolation; In the time of in substrate integrated waveguide directional filter works in working band, from first input end mouth feed, signal passes through substrate integrated waveguide directioning coupler one, substrate integration wave-guide loop one, substrate integrated waveguide directioning coupler two, substrate integration wave-guide loop two, substrate integrated waveguide directioning coupler three successively, finally all export from second output port, and the first output port no-output; In the time of outside substrate integrated waveguide directional filter works in working band, from first input end mouth feed, signal can only pass through substrate integrated waveguide directioning coupler one, substrate integration wave-guide loop one, substrate integrated waveguide directioning coupler two, can't enter substrate integration wave-guide loop two, substrate integrated waveguide directioning coupler three, finally all export from first output port, and the second output port no-output.

Beneficial effect: the present invention has the following advantages:

1 :) according to design objective, can accurately design to have and be with four port networks logical and band stop filter frequency individual features.

2 :) increase the number in loop, can improve the selectivity characteristic of directional filter effectively.

3 :) with the direct cascade of the directional filter of a plurality of different operating frequency ranges, can realize the high-performance multiplexer, can not interact between these directional filters, be convenient to design and realization.

4 :) the insertion loss is low, the circuit mutual coupling is little, the Q value is high, can realize the high-performance filtering characteristic.

5 :) work in the microwave and millimeter wave frequency range with the form of planar circuit, be made on the dielectric substrate by common PCB technology, have the integrated convenience of active circuit, cost is low, precision is high, good reproducibility, is fit to advantages such as production in enormous quantities.Compare with the circuit that stereochemical structure such as metal waveguide realizes, performance is approaching, and volume is little, in light weight, processing is easy.

Description of drawings

Fig. 1 is the cross-sectional view of substrate integrated waveguide directional filter of the present invention,

Fig. 2 is the planar structure schematic diagram of substrate integrated waveguide directional filter of the present invention,

Have among the above figure: the upper strata metal applies copper face 1, lower metal applies copper face 2, dielectric substrate 3, plated-through hole 4, first substrate integrated waveguide directioning coupler 51, second substrate integrated waveguide directioning coupler 52, the 3rd substrate integrated waveguide directioning coupler 53, the first substrate integration wave-guide loop 61, the second substrate integration wave-guide loop 62, first input end mouth 71, first output port 72, second input port 73, second output port 74, perceptual Metallic rod 8.

Embodiment

Substrate integrated waveguide directional filter among the present invention is the double loop directional filter, the upper strata metal applies copper face 1, lower metal applies the positive and negative both sides that copper face 2 lays respectively at dielectric substrate 3, and plated-through hole 4 passes dielectric substrate 3 and is connected and forms first substrate integrated waveguide directioning coupler 51, second substrate integrated waveguide directioning coupler 52, the 3rd substrate integrated waveguide directioning coupler 53, the first substrate integration wave-guide loop 61, the second substrate integration wave-guide loop 62 with the deposited copper face 1 of upper strata metal, the deposited copper face 2 of lower metal; Wherein, the first substrate integration wave-guide loop 61, the second substrate integration wave-guide loop 62 are respectively the rectangle that is surrounded by plated-through hole 4, the centre and the outside in the first substrate integration wave-guide loop 61, the second substrate integration wave-guide loop 62 are respectively equipped with between two row's plated-through hole 4, the first substrate integrated waveguide directioning couplers 51 two outside the first substrate integration wave-guide loop 61 and in first substrate integration wave-guide loop 61 row's plated-through holes; Between the row's plated-through hole of second substrate integrated waveguide directioning coupler 52 two in the first substrate integration wave-guide loop 61 and in second substrate integration wave-guide loop 62; Between the row's plated-through hole of the 3rd substrate integrated waveguide directioning coupler 53 two in the second substrate integration wave-guide loop 62 and outside second substrate integration wave-guide loop 62; First delivery outlet that first input port of substrate integrated waveguide directioning coupler 51 connects substrate integrated waveguide directional filter first input end mouth 71, substrate integrated waveguide directioning coupler 51 connects first output port 72 of substrate integrated waveguide directional filter, first input port of substrate integrated waveguide directioning coupler 53 connects substrate integrated waveguide directional filter second input port 73, and second delivery outlet of substrate integrated waveguide directioning coupler 53 connects second output port 74 of substrate integrated waveguide directional filter.The centerline length in the first substrate integration wave-guide loop 61 and the second substrate integration wave-guide loop 62 should be the integral multiple of the guide wavelength of substrate integration wave-guide; Each 90 ° of corner in the first substrate integration wave-guide loop 61 and the second substrate integration wave-guide loop 62 are equipped with a perceptual Metallic rod 8 to realize good coupling.

The coupling coefficient of first substrate integrated waveguide directioning coupler 51, second substrate integrated waveguide directioning coupler 52, the 3rd substrate integrated waveguide directioning coupler 53 can determine that method is as follows according to required operating frequency, relative bandwidth, filtering characteristic:

At first determine the form and the parameter of lowpass prototype filter: g according to design objective ₀, g ₁..., g _N+1, and ω ₁The central task frequency is f ₀, absolute bandwidth is that W is (from f ₁To f ₂), have

$f_0=\frac{f_1+{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="A2009100358250007H1.png"\; state="\{\{state\}\}">f</figure-callout>}}_2}{2}---\left(1\right)$

$W=\frac{f_2-f_1}{f_0}---\left(2\right)$

Can get:

${\left(Q_e\right)}_A=\frac{g_0{\mathrm{<figure-callout\; id="1"\; label="g"\; filenames="A2009100358250007H1.png"\; state="\{\{state\}\}">g</figure-callout>}}_1{\mathrm{\&omega;}}_1}{W}---\left(3\right)$

$k_{i,i+1}{|}_{i=2~n-1}=\frac{W}{{\mathrm{\&omega;}}_1\sqrt{g_i{g}_{i+1}}}---\left(4\right)$

${\left(Q_e\right)}_B=\frac{g_n{g}_{n+1}{\mathrm{\&omega;}}_1}{W}---\left(5\right)$

The voltage coupling coefficient C of each directional coupler then _{I, i+1}Can be calculated:

$C_{01}=\frac{1}{\sqrt{\frac{{\left(Q_e\right)}_{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="A2009100358250007H1.png"\; state="\{\{state\}\}">A</figure-callout>}}}{2\mathrm{\&pi;n}}{\left(\frac{\mathrm{\&lambda;}}{{\mathrm{\&lambda;}}_g}\right)}^2+\frac{1}{2}}}---\left(6\right)$

C _i，i+1＝nπk _i，i+1 (7)

$C_{n,n+1}=\frac{1}{\sqrt{\frac{{\left(Q_e\right)}_{\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="A2009100358250007H1.png"\; state="\{\{state\}\}">B</figure-callout>}}}{2\mathrm{\&pi;n}}{\left(\frac{\mathrm{\&lambda;}}{{\mathrm{\&lambda;}}_g}\right)}^2+\frac{1}{2}}}---\left(8\right)$

Wherein, λ _gBe the substrate integration wave-guide guide wavelength, λ is the operation wavelength in this structure.

The centerline length in the first substrate integration wave-guide loop 61, the second substrate integration wave-guide loop 62 is set at the guide wavelength integral multiple of substrate integration wave-guide, and n is the ratio of loop centerline length and guide wavelength.

The design's example is selected the double loop structure for use, to obtain better choice.Operating frequency is set at 12GHz, and bandwidth is 250MHz, and n=6, substrate select Rogers Duroid 5880 for use, and its dielectric constant is 2.2, and thickness is 0.254mm.Lowpass prototype filter is selected the Butterworth type, and its relevant parameters is selected as follows: g ₀=g ₃=1, g ₁=g ₂=1.414, utilize formula (1)-(8), can obtain the voltage coupling coefficient C of substrate integrated waveguide directioning coupler 51, substrate integrated waveguide directioning coupler 53 ₀₁=C ₂₃=0.8195, the voltage coupling coefficient C of substrate integrated waveguide directioning coupler 52 ₁₂=0.5055.Substrate integrated waveguide directioning coupler 51, substrate integrated waveguide directioning coupler 53 are the close coupling device of 3.46dB, so adopt continuous coupled form to realize; Substrate integrated waveguide directioning coupler 52 is the moderate strength filter of 11.85dB, so adopt the form of multistage coupling to realize.

During actual measurement, the frequency deviation of 60MHz appears in the centre frequency of substrate integrated waveguide directional filter, is 11.94GHz.In the working frequency range of 250MHz, insert loss and be lower than 3.2dB (minimum Insertion Loss is 1.5dB), reflection coefficient is less than-21.7dB, and isolation all is better than 17.8dB.

Claims (2)

1. substrate integrated waveguide directional filter, it is characterized in that the upper strata metal applies copper face (1), lower metal applies the positive and negative both sides that copper face (2) lays respectively at dielectric substrate (3), plated-through hole (4) passes dielectric substrate (3) and is connected and forms first substrate integrated waveguide directioning coupler (51), second substrate integrated waveguide directioning coupler (52), the 3rd substrate integrated waveguide directioning coupler (53), the first substrate integration wave-guide loop (61), the second substrate integration wave-guide loop (62) with the deposited copper face (1) of upper strata metal, the deposited copper face (2) of lower metal; Wherein, the first substrate integration wave-guide loop (61), the second substrate integration wave-guide loop (62) are respectively the rectangle that is surrounded by plated-through hole (4), be respectively equipped with two row's plated-through holes (4) in the centre in the first substrate integration wave-guide loop (61), the second substrate integration wave-guide loop (62) and the outside, first substrate integrated waveguide directioning coupler (51) is positioned at that the first substrate integration wave-guide loop (61) is outer arranges between the plated-through holes with two of the first substrate integration wave-guide loop (61); Second substrate integrated waveguide directioning coupler (52) is positioned between two row's plated-through holes in the first substrate integration wave-guide loop (61) and the second substrate integration wave-guide loop (62); The 3rd substrate integrated waveguide directioning coupler (53) is positioned at two outside the second substrate integration wave-guide loop (62) and the second substrate integration wave-guide loop (62) and arranges between the plated-through holes; First delivery outlet that first input port of substrate integrated waveguide directioning coupler (51) connects substrate integrated waveguide directional filter first input end mouth (71), substrate integrated waveguide directioning coupler (51) connects first output port (72) of substrate integrated waveguide directional filter, first input port of substrate integrated waveguide directioning coupler (53) connects substrate integrated waveguide directional filter second input port (73), and second delivery outlet of substrate integrated waveguide directioning coupler (53) connects second output port (74) of substrate integrated waveguide directional filter.

2. substrate integrated waveguide directional filter according to claim 1 is characterized by: the centerline length in the first substrate integration wave-guide loop (61) and the second substrate integration wave-guide loop (62) should be the integral multiple of the guide wavelength of substrate integration wave-guide; Each 90 ° of corner in the first substrate integration wave-guide loop (61) and the second substrate integration wave-guide loop (62) are equipped with a perceptual Metallic rod (8) to realize good coupling.

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