CN207719373U - Bicyclic mode filter is coupled based on the cascade all-wave length of parallel coupled line head and the tail - Google Patents
Bicyclic mode filter is coupled based on the cascade all-wave length of parallel coupled line head and the tail Download PDFInfo
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- CN207719373U CN207719373U CN201721874831.7U CN201721874831U CN207719373U CN 207719373 U CN207719373 U CN 207719373U CN 201721874831 U CN201721874831 U CN 201721874831U CN 207719373 U CN207719373 U CN 207719373U
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Abstract
The utility model discloses one kind coupling bicyclic mode filter based on the cascade all-wave length of parallel coupled line head and the tail, which is made of two cascade toroidal cavity resonators of head and the tail.Two head and the tail cascade coupling rings are formed by two pair of 3/4 guide wavelength parallel coupled line and a pair of 1/4 guide wavelength parallel coupled line, head and the tail grade is associated in the both ends of that intermediate a pair of parallel coupling line to the two pairs of parallel coupled lines in left and right respectively, to ensure that two toroidal cavity resonators are satisfied by all-wave length coupling.The filter construction can theoretically generate 8 transmission zeros outside passband, since input and output load cross-linked form using source, 1 transmission zero can be additionally generated, so actually the filter construction inhibits with 9 transmission zeros of outer generation to effectively realize high stop band.21.2% bandwidth and Wide stop bands may be implemented in whole circuit structure, simple in structure, only single layer structure, small, are easy to and the integrated use of other planar circuits.
Description
Technical Field
The utility model belongs to microwave millimeter wave mixes planar integrated circuit, concretely relates to full wavelength coupling double loop filter based on parallel coupling line end to end cascades.
Background
While microwave circuits are being developed toward complexity and integration in modern radio and mobile communication systems, filters play a very important and indispensable role therein, and filters of such a structure are favored by extensive researchers because they can be manufactured using printed circuit technology, and they are more suitable for commercial applications due to their compact structure, small size and low cost. In addition, the filter designed by using the parallel coupled line structure has the characteristics of simple structural design, small circuit size and high performance, thereby arousing the interest of extensive researchers. In recent years, more and more researchers have been working on filter studies with high selectivity and high stopband rejection, however, the ring filter structures of the existing designs have the following disadvantages: (1) although the out-of-band rejection is good, the in-band performance is poor, the passband edge is slowly reduced, and the in-band selectivity is poor; (2) the passband of the filter is narrow; (3) the whole circuit structure is complex, large in size, complex in design, poor in out-of-band inhibition and incomplete.
SUMMERY OF THE UTILITY MODEL
In view of this, an embodiment of the present invention provides a full-wavelength coupled dual-ring filter based on end-to-end cascading of parallel coupled lines, which has a simple structure and a small volume; the stop band rejection is improved.
The embodiment of the utility model provides a full wavelength coupling double loop filter based on parallel coupling line end to end cascades, include:
the device comprises a first port, a second port, a first parallel coupling line (3), a second parallel coupling line (4) and a third parallel coupling line (5);
the first parallel coupling line (3) comprises a first coupling microstrip line and a second coupling microstrip line;
the second parallel coupling line (4) comprises a third coupling microstrip line and a fourth coupling microstrip line;
the third parallel coupling line (5) comprises a fifth coupling microstrip line and a sixth coupling microstrip line;
the first coupling microstrip line is connected with the first port;
the sixth coupling microstrip line is connected with the second port;
the second coupling microstrip line and the third coupling microstrip line form a first closed ring;
the fourth coupling microstrip line and the fifth coupling microstrip line form a second closed loop.
Further, the lengths of the first parallel coupling line and the third parallel coupling line are both 3/4 guided wave wavelengths; the second parallel coupled line has a length of 1/4 guided wave wavelengths.
Further, the widths of the second coupling microstrip line and the fifth coupling microstrip line are smaller than the widths of the third coupling microstrip line and the fourth coupling microstrip line.
Further, the first port and the second port are located on the same side.
Further, still include: the first zigzag microstrip line and the second zigzag microstrip line; the first port is connected with one end of the first coupling microstrip line through the first zigzag microstrip line; the second port is connected with one end of the third coupling microstrip line through the second zigzag microstrip line.
Furthermore, the filter is of a bilateral symmetry structure, and a symmetry center line is a center line of the second parallel coupling line.
Further, the first parallel coupled line is reversely arched; the third parallel coupled line is arcuate.
Further, the coupling gaps of the first parallel coupling line and the third parallel coupling line are the same and are 0.15mm, and the coupling gap of the second parallel coupling line is 0.42 mm.
Further, the dielectric constant of the dielectric substrate is 2.65, and the height of the dielectric substrate is 1 mm.
Further, the widths of the first coupling microstrip line, the second coupling microstrip line, the fifth coupling microstrip line and the sixth coupling microstrip line are all 0.54mm, and the widths of the third coupling microstrip line and the fourth coupling microstrip line are 1.05 mm.
The filter provided by the embodiment is only composed of three sections of parallel coupling lines, and has a simple structure and a small volume compared with a traditional edge-coupled double-ring resonator; compared with the traditional side-coupled double-ring resonator structure, the full-wave coupled double-ring resonator structure can generate more transmission zeros, so that stop band rejection is greatly improved; the bandwidth and the position of the transmission zero point can be easily changed by adjusting the length, the width and the coupling distance of the parallel coupling lines.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive effort.
Fig. 1 is a top view of a filter according to an embodiment of the present invention.
Fig. 2 is an ideal circuit model diagram of the filter according to the embodiment of the present invention.
Fig. 3 is an ideal circuit frequency response diagram of the filter according to the embodiment of the present invention.
Fig. 4(a) is a frequency response diagram of the filter according to the embodiment of the present invention in the case where the coupling coefficient k1 is changed.
Fig. 4(b) is a frequency response diagram of the filter according to the embodiment of the present invention in the case where the coupling coefficient k2 is changed.
Fig. 5 is a simulation graph of a filter according to an embodiment of the present invention.
Fig. 6 is a frequency response diagram of a filter according to an embodiment of the present invention when the input-output coupling length is changed.
Fig. 7 is a frequency response diagram of the filter according to the embodiment of the present invention under the condition that the widths of the second and fifth coupling microstrip lines are changed.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
Fig. 1 is a schematic structural diagram of a full-wavelength coupled dual-ring filter based on end-to-end cascading of parallel coupled lines according to an embodiment of the present invention. In this embodiment, the filter includes: a first parallel coupling line 3, a second parallel coupling line 4 and a third parallel coupling line 5; the lengths of the first parallel coupling line and the third parallel coupling line are both 3/4 guided wave wavelengths; the second parallel coupled line has a length of 1/4 guided wave wavelengths.
The first parallel coupling line 3 comprises a first coupling microstrip line and a second coupling microstrip line; the second parallel coupling line 4 comprises a third coupling microstrip line and a fourth coupling microstrip line; the third parallel coupled line 5 includes a fifth coupled microstrip line and a sixth coupled microstrip line. The second coupling microstrip line and the third coupling microstrip line form a first closed ring; the fourth coupling microstrip line and the fifth coupling microstrip line form a second closed ring. The widths of the second coupling microstrip line and the fifth coupling microstrip line are smaller than the widths of the third coupling microstrip line and the fourth coupling microstrip line. The first parallel coupling line is in an inverse arch shape; the third parallel coupled line is arcuate.
The first port and the second port are located on the same side. The first coupling microstrip line is connected with the first port; the sixth coupling microstrip line is connected with the second port; the first port is connected with one end of the first coupling microstrip line through the first zigzag microstrip line; the second port is connected with one end of the third coupling microstrip line through the second zigzag microstrip line.
In fig. 1, three pairs of parallel coupling lines are cascaded to form two full-wave coupling closed loops, and the position of the zero point can be easily adjusted by adjusting the width, coupling gap, etc. of the parallel coupling lines to change the coupling coefficient of the parallel coupling lines. The whole circuit is in a bilateral symmetry structure, the symmetric center line is the center line of the second parallel coupling line, the size of the second parallel coupling line is 38mm 26.44mm 1mm, the dielectric constant of the dielectric substrate is 2.65, and the thickness of the dielectric substrate is 1 mm. In fig. 1, the microstrip lines 1 and 2 have a length of 18mm and a width of 2.7mm, the first coupling microstrip line, the second coupling microstrip line, the fifth coupling microstrip line and the sixth coupling microstrip line included in the first parallel coupling line 3 and the third parallel coupling line 5 have a width of 0.54mm, the coupling pitches have a length of 0.15mm and a length of 78.3mm, the third coupling microstrip line and the fourth coupling microstrip line included in the second parallel coupling line 4 have a width of 1.05mm, the coupling pitches have a width of 0.42mm, and the lengths have a length of 25.6 mm.
FIG. 2 is an idealized circuit diagram of a full wavelength coupled double loop filter in which the parallel coupled lines are cascaded end to end, where θ represents the electrical length of the second parallel coupled line and Z represents the electrical length of the second parallel coupled line0e2And Z0o2The first parallel-coupled line 3 and the third parallel-coupled line 5 have an electrical length of 3 theta and an odd-even mode characteristic impedance of Z0e1And Z0o1. By analyzing the circuit by adopting an impedance network matrix method, the voltage and current conditions of each port can be obtained: v2＝V5，I2＝-I5，V3＝V8，I3＝-I8，V6＝V9，I6＝-I9，V7＝V12，I7＝-I12And I4＝I11＝0，[Z]aAn impedance matrix representing the first 3 and third 5 parallel coupled lines, [ Z ]]bDefined as the impedance matrix of the first parallel coupled lines 2. Thus, we can calculate the impedance matrix of the whole ideal circuit as:
wherein
According to the relation between the impedance matrix and the S parameter, we can obtain the transmission coefficient S21Expression (c):
by making S21At 0, we can obtain the expression of 8 transmission zeros as follows:
ftz1＝0 (10)
ftz8＝2f0(17)
wherein,
F＝4Z0e1Z0e2+2Z0e1Z0o1+4Z0e1Z0o2+4Z0e2Z0o1+4Z0e2Z0o2+4Z0o1Z0o2(18)
fig. 3 shows the ADS simulation results of the ideal circuit model (fig. 2), where the filter has eight transmission zeros outside the passband to suppress the stopband, which is exactly in line with the theoretical calculation results. Eight transmission zeros 4 (f)tz1、ftz3、ftz6、 ftz8) Are fixed and are respectively positioned at 0 and 2f0/3，4f0/3，2f0Position, and four other transmission zeros (f)tz2、ftz4、ftz5、 ftz7) Is the characteristic impedance (Z) of the three parallel coupled lines0e1、Z0o1、Z0e2、Z0o2) Regarding this, expressions of eight transmission zeros are shown in equations (10) to (20). In general, we use k to represent the coupling coefficient of a segment of coupled line, which is defined as: k ═ Z0e-Z0o)/(Z0e+Z0o) FIGS. 4(a) - (b) depict S, respectively21Simulation result and coupling coefficient k of first parallel coupling line and third parallel coupling line1(k1＝(Z0e1-Z0o1)/(Z0e1+Z0o1) K) and the second parallel coupled line2(k2＝(Z0e2-Z0o2)/(Z0e2+Z0o2) ) of the other. F can be obtained by solving the formula and ADS simulation results (FIG. 4)tz2、ftz4、ftz5、ftz7And Z0e1、Z0o1、Z0e2、Z0o2Related, i.e. to k1And k2Is related to, thus following k1And k2Change of (a), (b), (c) and (d)tz2、ftz4、ftz5、ftz7Offset occurs, the theory and ADS simulation diagram are just satisfied, which shows that the four transmission zero points are controllable, and ftz1、ftz3、ftz6、ftz8Is not following k1And k2Is changed. This conclusion can also be drawn from equations (10) - (20). As can also be seen from fig. 4(a) - (b), the bandwidth of the passband is mainly determined by the coupling coefficient k of the first parallel coupling line and the third parallel coupling line1Determination of k1The larger, the wider the bandwidth; and the coupling coefficient k of the second parallel coupled line2Mainly controlling the amplitude of suppression of transmission zeros, k2The smaller the out-of-band rejection. Fig. 1 is an actual circuit diagram of the parallel coupled line end-to-end cascaded full-wavelength coupled dual-ring filter, and a source-load cross coupling form is adopted at an input end and an output end, and 1 transmission zero can be additionally generated, so that in practice, the filter structure can generate 9 transmission zeros out of band, as shown in fig. 5, a simulation curve diagram of an actual circuit of the parallel coupled line end-to-end cascaded full-wavelength coupled dual-ring filter is shown, and the center frequency of the designed filter is 2.08 GHz. The figure clearly shows 9 transmission zeros, which verifies our theory and also shows that filters with other center frequencies are designed.
In fig. 6, as the preferred embodiment provided by the present invention, when the electrical lengths of the first coupling microstrip line and the sixth coupling microstrip line of the filter are 3/4 guided wave wavelengths, that is, the input and output ends are three-quarter wavelength coupling, the number of out-of-band transmission zero points is up to 9, which effectively improves the out-of-band rejection capability of the filter. When the electrical lengths of the first coupling microstrip line and the sixth coupling microstrip line of the filter are both 1/4 guided wave wavelengths, that is, the input end and the output end are both coupled by a quarter wavelength, the out-of-band transmission zero point of the filter is significantly reduced, which results in significant deterioration of the out-of-band rejection capability of the filter. Obviously the utility model provides an embodiment of preferred adopts two pairs of 3/4 guided wave wavelength parallel coupling lines and a pair of 1/4 guided wave wavelength parallel coupling lines to form the cascade ring, because whole loop configuration cascades by the parallel coupling line and forms, and two rings all satisfy full wave coupling, and input and output end adopts is the form of source-load cross coupling, so can restrain some resonance modes that do not need, produces 9 transmission zeros, has improved the stop band suppression widely.
In FIG. 7, a second coupled microstrip line andthe width of the fifth coupling microstrip line is always kept equal by W1And (4) showing. When W is1When the width of the microstrip line is smaller than the width of the third coupling microstrip line and the fourth coupling microstrip line, as the preferred embodiment provided by the present invention, preferably, W1At a center frequency of 2.08GHz, the passband bandwidth is about 21.2%, and the filter squareness factor is better, 0.54 mm. When W is1Greater than or equal to the widths of the third and fourth coupled microstrip lines, e.g., W1At 1.05mm or 1.56mm, the bandwidth and rectangular coefficients of the filter deteriorate significantly, even with notches. Obviously the utility model provides an embodiment adopts the design of ladder impedance formula to first closed loop and second closed loop, has improved the passband characteristic of wave filter, has enlarged the bandwidth of wave filter.
The design method and the specific example design of the full-wavelength coupling double-ring filter with the parallel coupling lines cascaded end to end are adopted, two pairs of 3/4 wave guide wavelength parallel coupling lines and one pair of 1/4 wave guide wavelength parallel coupling lines form a cascade ring, the whole ring structure is formed by cascading the parallel coupling lines, both the two rings meet full-wave coupling, and the input end and the output end adopt a source-load cross coupling mode, so that some unnecessary resonance modes can be inhibited, 9 transmission zeros are generated, and stop band inhibition is greatly improved. The 3dB bandwidth of the whole frequency band is about 21.2%, the inhibition amplitude of the upper stop band is better than 30dB, the inhibition amplitude of the lower stop band is better than 20dB, and the high-frequency band has very good stop band inhibition. And the whole working circuit has simple structure and design and stronger practicability, the circuit simulation curve diagram of the filter model at the position of 2.08GHz center frequency is shown in figure 5, the circuit is shown in figure 1, the size is 38mm 26.44mm 1mm, and the weight is light.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention.
Claims (10)
1. A full-wavelength coupling double-ring filter based on end-to-end cascading of parallel coupled lines comprises: the device comprises a first port, a second port, a first parallel coupling line (3), a second parallel coupling line (4) and a third parallel coupling line (5);
the first parallel coupling line (3) comprises a first coupling microstrip line and a second coupling microstrip line;
the second parallel coupling line (4) comprises a third coupling microstrip line and a fourth coupling microstrip line;
the third parallel coupling line (5) comprises a fifth coupling microstrip line and a sixth coupling microstrip line;
the first coupling microstrip line is connected with the first port;
the sixth coupling microstrip line is connected with the second port;
the method is characterized in that:
the second coupling microstrip line and the third coupling microstrip line form a first closed ring;
the fourth coupling microstrip line and the fifth coupling microstrip line form a second closed loop.
2. The filter according to claim 1, characterized in that the first parallel coupled line (3) and the third parallel coupled line (5) are both 3/4 guided wave wavelengths in length; the length of the second parallel coupling line (4) is 1/4 guided wave wavelength.
3. The filter of claim 1, wherein the widths of the second and fifth coupling microstrip lines are smaller than the widths of the third and fourth coupling microstrip lines.
4. The filter of claim 2, wherein the first port and the second port are located on the same side.
5. The filter of claim 4, further comprising: a first zigzag microstrip line (1) and a second zigzag microstrip line (2);
the first port is connected with one end of the first coupling microstrip line through the first zigzag microstrip line (1);
the second port is connected with one end of the third coupling microstrip line through the second zigzag microstrip line (2).
6. A filter according to any of claims 1-5, characterized in that the filter is of a left-right symmetrical structure, the centre line of symmetry being the centre line of the second parallel coupled line (4).
7. A filter according to claim 6, characterised in that the first parallel coupled line (3) is of an inverse arcuate shape; the third parallel coupled line (5) is arcuate.
8. The filter according to claim 6, characterized in that the coupling gaps of the first parallel coupled line (3) and the third parallel coupled line (5) are both 0.15mm and the coupling gap of the second parallel coupled line (4) is 0.42 mm.
9. A filter according to claim 6, wherein the dielectric substrate has a dielectric constant of 2.65 and a height of 1 mm.
10. The filter of claim 6, wherein the widths of the first, second, fifth and sixth coupling microstrip lines are all 0.54mm, and the widths of the third and fourth coupling microstrip lines are 1.05 mm.
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| CN108281738A (en) * | 2017-12-27 | 2018-07-13 | 厦门大学 | Bicyclic mode filter is coupled based on the cascade all-wave length of parallel coupled line head and the tail |
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