CN104466320B

CN104466320B - Ka wave band broadband band-pass filter utilizing cut-off waveguide

Info

Publication number: CN104466320B
Application number: CN201410789086.0A
Authority: CN
Inventors: 汪灏; 武华锋; 张思明; 杨斐; 雷国忠
Original assignee: Xian Electronic Engineering Research Institute
Current assignee: Xian Electronic Engineering Research Institute
Priority date: 2014-12-18
Filing date: 2014-12-18
Publication date: 2017-05-10
Anticipated expiration: 2034-12-18
Also published as: CN104466320A

Abstract

The invention relates to a Ka wave band broadband band-pass filter utilizing a cut-off waveguide. According to the Ka wave band broadband band-pass filter, the design method combining the cut-off waveguide theory, the low-pass filter theory and the waveguide gradual change theory is adopted, and a Ka wave band 32-40GHz waveguide broadband filter is designed by the adoption of the design method. When a broad side of a waveguide port is selected, under the condition that the length is fixed, it needs to be guaranteed that the cut-off frequency is smaller than the band-pass low-frequency point of the filter, and low-frequency out-of-band rejection also needs to be guaranteed. According to linear gradual change transition of the wide and narrow sides of the waveguide, when the frequency is higher than and approximate to the cut-off frequency of the waveguide, the wavelength of the waveguide approaches infinite length, and ratio between the waveguide impedance and standard waveguide outlet impedance approaches approximately infinite. The Ka wave band broadband band-pass filter utilizing the cut-off waveguide achieves the filter performance in a broadband transmitter and a broadband transmitting-receiving assembly in an electronic countermeasure.

Description

Using the Ka band broadband bandpass filters of cut-off waveguide

Technical field

The invention belongs to ECM field, and in particular to a kind of Ka band broadbands band logical filter of application cut-off waveguide Ripple device.

Background technology

In Millimeter wave countermeasure equipment, the generation of broadband millimeter-wave transmission signal comes from the frequency multiplication of low frequency signal and mixes Frequently, therefore various spurious signals have been attached, in wideband transmitter, broadband transmitting-receiving subassembly, it would be desirable to adopt broadband filter Harmonic wave and spurious signal are suppressed.In millimeter wave frequency band, wave filter has the structures such as micro-strip, SIW, waveguide.Microstrip filter It is excessive due to being lost with SIW wave filters (substrate integral wave guide filter), it is not suitable for millimeter wave broadband emitter, broadband transmitting-receiving The output filtering of component；Waveguide filter has the advantages that power capacity is big, little, passband width is lost, and is suitable for millimeter wave broadband The wideband filtered application of emitter, broadband transmitting-receiving subassembly.In waveguide bandpass filter, traditional structure is waveguide resonator and coupling The mode that structure combines is closed, this fabric bandwidths are maximum up to 15% or so, when bandwidth is wide, because difficulty of processing crosses senior general very Hardly possible is realized.For the waveguide broad-band bandpass filter of design bandwidth 22%, it is proposed that using cut-off waveguide theory, LPF The method for designing design millimeter wave broadband waveguide filter that theoretical and waveguide gradual change theory combines.

The content of the invention

The technical problem to be solved

In order to avoid the deficiencies in the prior art part, the present invention proposes a kind of Ka band broadband band logicals of application cut-off waveguide Wave filter, realizes electronic countermeasure middle width strip emitter and the filtering performance in the transmitting-receiving subassembly of broadband.

Technical scheme

A kind of Ka band broadband bandpass filters of application cut-off waveguide, it is characterised in that including waveguide lowpass and Waveguide transition line；Connect waveguide transition line at the two ends of waveguide lowpass, the broadside size Selection of connectivity port must expire Sufficient condition once：Basic mode TE₁₀Mould cut-off frequency is less than filter passband low frequency point, and basic mode TE₁₀Mould cut-off frequency is outer higher than band Low frequency inhibition point；And higher mode TE₂₀Mould cut-off frequency is higher than band logical high frequency points, basic mode TE₁₀Mould cut-off frequency is logical less than wave filter Band low frequency point；The narrow side size Selection of connectivity port must is fulfilled for condition：Higher mode TE₁₁Mould cut-off frequency is higher than band passband High-frequency suppressing point, and meet the requirement of working ability；The size of another port of waveguide transition line and the standard ripple being connected The bore led matches.

The broadside size of the waveguide transition line and narrow side size are converted simultaneously, and waveguide width side linear gradient formula is such as Under：

Wherein：A, b, be conversion before waveguide port, a₀,b₀, be conversion after waveguide port, L₀For waveguide transition line Length, λ is frequency f₀The air wavelength at place.

The waveguide transition line is provided with chamfering r with waveguide lowpass connecting portion.

Chamfering r is 0.5mm.

The filter passband low frequency point is 32GHz.

The outer low frequency inhibition point 30GHz.

The band passband high-frequency suppressing point 40GHz.

The length of the waveguide transition line is 25mm.

Beneficial effect

A kind of Ka band broadband bandpass filters of application cut-off waveguide proposed by the present invention, propose with reference to cut-off waveguide reason By the Novel Filter method for designing that, LPF is theoretical and waveguide gradual change is theoretical.When theoretical using cut-off waveguide, control non- The size of mark waveguide port, the waveguide lowpass using LPF Theoretical Design, and by waveguide width sideline property gradually Structure changes transform to standard waveguide mouth.The present invention, in the timing of length one, should ensure cutoff frequency when waveguide port broadside is selected Rate is less than filter passband low frequency point, and low frequency Out-of-band rejection need to be ensured again.In the property gradual transition of waveguide width sideline, in frequency Higher than and during close waveguide cutoff frequency, the close endless of waveguide wavelength, waveguide impedance is close to standard waveguide mouth impedanoe ratio It is infinitely great.A kind of Ka wave bands 32-40GHz waveguide broad-band wave filters of the present invention, realize electronic countermeasure middle width strip emitter and broadband Filtering performance in transmitting-receiving subassembly.

Description of the drawings

Fig. 1：Waveguide broad-band bandpass filter structures figure

1- standard waveguides, 2- waveguide transition lines, 3- waveguide lowpasses.

Fig. 2：Waveguide width sideline property graded junction composition

Fig. 3：Waveguide low-pass filter structure figure

Fig. 4：Waveguide broad-band bandpass filter simulation result figure

Specific embodiment

In conjunction with embodiment, accompanying drawing, the invention will be further described：

In the present invention, waveguide broad-band bandpass filter includes waveguide port selection, waveguide transition line transition, waveguide low pass Three aspects of filter structure.Waveguide port will ensure that the outer low frequency of bandpass filter band suppresses, therefore theoretical using cut-off waveguide, if The cut-off frequency of guarantee waveguide is higher than and away from the outer low frequency inhibition point of band during meter waveguide mouth broadside size；When signal is entered and waveguide During the broadside identical waveguide segment of port, will pass through higher than cut-off frequency signal, less than cut-off frequency signal, waveguide will be showed Going out forceful electric power resistance has serious mismatch, and reflection causes greatly most of power to transmit and decay very much.And decay size and biography The size for broadcasting constant imaginary part is related to the length of cut-off waveguide.Propagation constant imaginary part is bigger, waveguide length is longer, in fixed frequency Upper decay is bigger.When waveguide port broadside is less, propagation constant imaginary part is bigger；Waveguide port broadside is less, waveguide cutoff frequency It is bigger.Therefore, when waveguide port broadside is selected, in the timing of length one, should ensure that cut-off frequency is low less than filter passband Frequency, need to ensure low frequency Out-of-band rejection again.

It is higher than and during close waveguide cutoff frequency that waveguide wavelength connects in frequency in the property gradual transition of waveguide width sideline Nearly endless, waveguide impedance is close to infinity with standard waveguide mouth impedanoe ratio.Therefore in this regard, waveguide cutoff frequency needs remote The low frequency point in filter passband.The design of waveguide port broadside will consider the aspect of the above three.In waveguide width sideline, property is gradually In becoming transition, waveguide width side converts simultaneously during waveguide transition, and waveguide width side linear gradient formula is as follows：

By theory deduction pole location and simulation optimization transition length designed in conjunction, it is ensured that the feasibility of transition.

When according to low pass filter Theoretical Design low pass filter, can be realized by inductance capacitance.In waveguide low pass filtered These can go out waveguide lowpass by the high low-impedance line Approximate Design of waveguide in ripple device.It is now high in low pass filter waveguide It is the approximate reactance component of impedance using basic mode when Low ESR is approximate, therefore the maximum on Narrow Wall of Waveguide side, minimum dimension is suitable, Ensure that the impact of higher mode is unlikely to various numerical value and far deviates using evaluation during waveguide basic mode, ensure that processing will again Ask.Therefore in the case where reactance original cost numerical value determines, used as normalized impedance value, the narrow side of waveguide port selects to need to protect for waveguide port impedance More than card two aspect.In the case where port is suitable, suitable waveguide lowpass is designed.

Specific embodiment：

If Fig. 1 is Ka wave band waveguide broad-band bandpass filter structures.Its structure includes the Ka wave band standard waveguide mouths at two ends, Size is a × b, and interconnection is realized with outside by this standard waveguide mouth.It is L by length₀Waveguide width side linear transformation reality Existing standard waveguide mouth transforms to nonstandard waveguide mouth, and size is a₀×b₀, as shown in Figure 2.Cut-off frequency is designed with this nonstandard waveguide mouth For the waveguide lowpass of 40GHz, as shown in Figure 3.

Nonstandard waveguide mouth broadside a₀Design synthesis considers following aspect：

1 is theoretical according to cut-off waveguide, basic mode TE₁₀Mould cut-off frequency less than filter passband low frequency point, i.e. here be less than 32GHz。

2 is theoretical according to cut-off waveguide, basic mode TE₁₀Mould cut-off frequency is higher than and the TE with outer low frequency inhibition point 30GHz₁₀Mould Cut-off frequency selects to ensure that low frequency suppresses index request.Higher by frequency, low frequency inhibition is better.

3 is theoretical according to cut-off waveguide, higher mode TE₂₀Mould cut-off frequency is higher than band passband high frequency points 40GHz, it is ensured that in passband For single mode.And higher mode TE₂₀Mould cut-off frequency is higher, and single mode transport frequency band is wider, and effect is better.

4 according to waveguide width sideline property gradual transition, because operating frequency is the closer to by frequency, waveguide wavelength closer to Endless, waveguide impedance is closer to infinity.To ensure transition smoothly, basic mode TE₁₀Mould cut-off frequency need to be less than filter passband Low frequency point, i.e. here are that, less than 32GHz, and cut-off frequency is less, and transition effect is better in passband.

The narrow side b of nonstandard waveguide mouth₀Design synthesis considers following aspect：

1 requires according to single mode transport, and the narrow side of any waveguide segment ensures higher mode TE₁₁Mould cut-off frequency be higher than and away from band logical Band high-frequency suppressing point 40GHz.

The narrow side of 2 any waveguide segments meets working ability.

It is long by theory deduction pole location and simulation optimization transition designed in conjunction in the side linear transformation of waveguide width Degree L₀, it is ensured that the feasibility of transition.

The nonstandard waveguide mouth a of here₀×b₀During design cut-off frequency is for the waveguide lowpass of 40GHz, according to Chebyshev comprehensively combines the high Low ESR reactance principle of equal effects, and concrete size is 17 ranks.Size per rank is as shown in Figure 3.

Using Ansoft HFSS electromagnetic simulation softwares, using the form of waveguide broad-band bandpass filter shown in Fig. 1 to every ginseng Number carries out simulation optimization, and parameter optimization result is as shown in table 1.

Such as Fig. 4, simulation result shows：Filter passband bandwidth 32-40GHz, echo S11 in passband band<- 20dB, f= During 30GHz, degree of suppression >=38dB, during f=42GHz, degree of suppression >=23dB.

The Ka band broadband filter parameters of table 1

a	b	a₀	b₀	L₀	r	b₁	b₂	b₃	b₄	b₅	b₆
												7.112	3.556	4.85	1	25	0.5	0.74	2.5	0.4	2.5	0.4	2.5
b₇	b₈	b₉	l₁	l₂	l₃	l₄	l₅	l₆	l₇	l₈	l₉
												0.4	2.5	0.4	0.77	1.02	0.82	1.35	0.98	1.40	1.04	1.39	1.06

Unit is mm.

Claims

1. Ka band broadband bandpass filters of a kind of application cut-off waveguide, it is characterised in that including waveguide lowpass and ripple Lead transition line；The two ends of waveguide lowpass connect respectively a port of waveguide transition line, the broadside size of connectivity port Selection must is fulfilled for condition：Basic mode TE₁₀Mould cut-off frequency is less than filter passband low frequency point, and basic mode TE₁₀Mould cutoff frequency Rate is higher than with outer low frequency inhibition point；And higher mode TE₂₀Mould cut-off frequency is higher than band logical high frequency points, basic mode TE₁₀Mould cut-off frequency is low In filter passband low frequency point；The narrow side size Selection of connectivity port must is fulfilled for condition：Higher mode TE₁₁Mould cut-off frequency Higher than band passband high-frequency suppressing point, and meet the requirement of working ability；The size of another port of waveguide transition line be connected The bore of the standard waveguide for connecing matches；The broadside size of the waveguide transition line and narrow side size are converted simultaneously, waveguide width Side linear gradient formula is as follows：

Wherein：A, b, be conversion before waveguide port, a₀,b₀, be conversion after waveguide port, L₀For the length of waveguide transition line, λ is frequency f₀The air wavelength at place,For frequency f₀Reflectance factor, Z₀For standard waveguide port identity impedance, z is from waveguide Mouth arrives length of the nonstandard waveguide port along transmission direction.

2. according to claim 1 using the Ka band broadband bandpass filters of cut-off waveguide, it is characterised in that：The waveguide Transition line is provided with chamfering r with waveguide lowpass connecting portion.

3. according to claim 2 using the Ka band broadband bandpass filters of cut-off waveguide, it is characterised in that：The chamfering R is 0.5mm.

4. according to claim 1 using the Ka band broadband bandpass filters of cut-off waveguide, it is characterised in that：The filtering Device passband low frequency point is 32GHz.

5. according to claim 1 using the Ka band broadband bandpass filters of cut-off waveguide, it is characterised in that：It is described outer low Frequency inhibition point 30GHz.

6. according to claim 1 using the Ka band broadband bandpass filters of cut-off waveguide, it is characterised in that：The band logical Band high-frequency suppressing point 40GHz.

7. according to claim 1 using the Ka band broadband bandpass filters of cut-off waveguide, it is characterised in that：The waveguide The length of transition line is 25mm.