SU1728904A1 - Microstrip rejection filter - Google Patents

Abstract

The area of use is frequency-selective ultra-high frequency devices. The purpose of the invention is to expand the bandwidth by eliminating the parasitic fringe bands of the microstrip notch filter. The microstrip notch filter contains a dielectric substrate 1, on one side of which a grounding base is applied, and on the other side is a strip conductor 2, the width of which periodically changes according to the law of variation of the impedance of the non-uniform line corresponding to the change in the deduction of the input resistance at the center frequency of the obstacle band. By using a variable width of the strip conductor 2, spurious attenuation bursts are eliminated and the bandwidth is increased. 1 il. (Ls

Description

The invention relates to microwave technology and can be used in frequency selective devices.

The purpose of the invention is to increase the bandwidth by eliminating parasitic obstacle bands.

The drawing shows the design of the microstrip notch filter.

The microstrip notch filter contains a dielectric substrate 1, on one side of which a grounding base is applied (not shown), and on the other a strip conductor 2, the beginning of which is input 3, and the end is output 4. The strip conductor 2 is made with a width X, periodically changing according to the law of change of the impedance of the non-uniform line, corresponding to the change in the deduction of the input impedance at the central frequency of the obstacle band. The number N of periods of change in the wave resistance of the strip conductor 2 is equal to the pole number on the frequency axis in which the change in the deduction is made.

Microstrip notch filter works as follows.

The microwave signal arriving at input 3 passes to output 4 at all frequencies except the frequencies of the barrier band. The barrier strip is formed due to the configuration of the strip conductor 2, selected from the following considerations.

It is known that a segment of a homogeneous line connected to input 3 has a periodic equidistant spectrum in which alternating zeros and poles of the input resistance are located at the same distance on the frequency axis, and the residues in all bands are the same and equal

kfr) w °

t3

where W0 is the characteristic impedance;

t.z - the delay time of a given line segment.

When at least one of these three parameters changes (pole position, zero or deduction value), the homogeneous line becomes non-uniform, in which the characteristic impedance W (r) becomes a function of the g coordinate.

The maximum change in the frequency response, for example, the working decay of such a line segment, is observed in the region of the perturbation of the spectrum.

Consider the case of a change in the deduction in one of the poles of the input resistance of the strip conductor 2. The law of the change in the characteristic impedance can be reduced to the form

+ -3102 /

#P . oh i 2

W (T) W (o) {W (o)

sin 2y) n y

where UE is the resonant frequency (pole) of the input impedance, in which the deduction varies;

2n magnitude change of the deduction.

An analysis of this expression shows that the wave impedance of a line with a strip conductor 2 of variable width W () oscillates relative to the impedance W0 of input 3, and the amplitude of these oscillations is determined by the magnitude of the change in the deduction On and decreases with increasing m. Consider the segment of such a line along which length an integer N of wavelengths W (r) is laid. The idle matrix of this quadrupole has the form

g / zr W0

z

Wocthpts +

Wc

, Wocthpts -shp ta affP

shpta OS + 1) (p2 +)

where p j is the complex frequency;

a 2kft) lw °

t3

 double value

input 3 deduction;

about ®n

H is the ratio of the magnitude of the change in the deduction to the deduction of input 3.

In this case, the impedance at the input 3 and output 4 are the same and equal to the characteristic impedance of input 3:

W (o) W ((ts) W0.

Due to the presence in the equivalent circuit of parallel resonant circuits connected in series, the line segment with the strip conductor 2 has a maximum input resistance at the frequency of the change in cp,

The expression for determining the working attenuation is

0

five

L (gb) +

BUT

re

pt3

2j32p2yhpt3

t308 + 1) (p2 + ft)

one

t50S + 1) (P2 +) 2

Due to the presence of a strip conductor 2 of variable width, spurious fading bursts are eliminated.

Geometrical dimensions of the microbud notch filter taking into account the FAF-4 dielectric thickness; en 2.5) h 1 mm parade UGHZ, / 3 20, the following, mm:

W 50.0; X0 2.82; 0 0;

W 186.99; Xi 0.11; And 2.67;

W 26.31; X2 6.83; g 7.95;

W 76.56; Hz 1.37; H 13.08;

W 36.34; X4 4.47; C 18,29;

W 64.52; Xs 1.87; Is 23.44;

W — 40.43; Xe 3.86; le 28.62;

W 59.98; XT 2.12; I - 33.78;

W 42.64; Xs 3.58; Is 38.96;

W 57.60; Xg 2.26; Ig 44.12;

W 44.02; Huy 3.41; ho 49.3;

W 50.0; Xn 2.82; In 51.87.

Ph o pm lu inventions

Microstrip notch filter containing dielectric sub0

five

0

a spoon, on one side of which a grounding base is applied, and on the other - a strip conductor, the beginning of which. is an input, and the end is an output, characterized in that, in order to broaden the bandwidth by eliminating parasitic obstacle bands, the strip conductor is made with a width varying periodically according to the law of variation of the impedance of a non-uniform line corresponding to the change in the deduction of the input resistance on the central the frequency of the barrier band, and the number of periods of change in the wave resistance of the strip conductor is equal to the pole number on the frequency axis in which the change in deduction is made.

Claims (1)

Claim A microstrip notch filter containing a dielectric under a spoon, on one side of which a grounding base is applied, and on the other a strip conductor, the beginning of which is the input and the end as the output, characterized in that, in order to expand the passband by eliminating spurious barriers , the strip conductor is made with a width periodically changing according to the law of variation of the wave impedance of an inhomogeneous line corresponding to a change in the deduction of the input impedance at the central frequency e barriers, and the number of periods of change in the wave impedance of the strip conductor is equal to the pole number on the frequency axis in which the change in deduction is made.