JPS586601A - Coplanar waveguide filter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to microwave filters, and more particularly to microwave filters having a coplanar waveguide (OPW) structure.

Various stripline or microstrip edge-coupled bandpass filters are known. Alternatively, as shown in FIGS.
The electrical material 14 has a ground surface 16 on its lower surface. In such filter structures, the signal on one of the conductors, for example that on conductor 10, is coupled to the other conductor 12 in parallel with the gap 18, and these filters maintain the desired characteristics even when the transmission line is asymmetric. This microstrip filter design technique, which shows The desired open impedances Zoe and ZooO are calculated from the low-pass filter prototype, respectively.

For a friend, when both conductors are at opposite potentials (i.e. +1 and -1 volts), the odd mode
It is assumed that the impedance ZooFi is either impedance, and when both have the same potential, the even-impedance impedance Zoe is either impedance. In order to obtain the desired filter characteristics, it is important that each of conductors 10 and 12 have the same even mode impedance Zoe and odd mode impedance.

This is not difficult in a microstrip structure since each of the conductors 10 and 12 is separated from the same ground plane by the same thickness of conductive material 14.

In an OPW structure, the input/output conductors and ground plane are all in the same plane. 5flJ and 4mK, the conductors 20 and 22 are coated with a dielectric material 240, similar to the configuration shown in FIG. 1, and the ground plane 16 shown in FIG. conductor 20 or 2 on the top surface of the material
The ground conductors 26 are replaced by an even pair of ground conductors 26. In the CPW edge-coupled filter shown in FIG. 3, the desired Zoo and Zoo values could hardly be obtained due to the light of their asymmetric structure. Paying attention to the central coupling portion of the filter shown in FIG. 3, conductor 20 is closer to the top ground conductor than conductor 22; It's approaching 26.

This asymmetric coupling of conductors 20 and 22 to different ground conductors is asymmetric with respect to the transmit centerline 28 field, which causes excitation in even modes of propagation between the ground planes. This even mode of propagation is prone to unfavorable transmission characteristics that are difficult to predict, and some type of suppression, e.g. when coupled by wires from one plane to another, usually results in some It is only required that the tube have satisfactory properties.

Considering the above-mentioned problems, the application range of the CPW filter is limited when a high-performance filter is not required, and it is necessary to improve the CPW filter technology.

Therefore, the object of the present invention is to provide a highly satisfactory filter that does not involve the above-mentioned difficulties and is highly efficient when a high-performance filter is required.
An object of the present invention is to provide a IIi wave tube (CPf) filter.

The O/W filter according to the present invention is basically the first
and a second conductor, 1IL1, and a second conductor surface, all of which are coated on the same surface of a dielectric material. The connecting portion is inserted into each connection of the ground plane and then branched. These first and second conductors are symmetrical in all respects with respect to the transmitting center II.

The present invention will now be described in detail with reference to the accompanying drawings.

The filter according to the present invention is based on the idea that the odd mode propagation that causes the spurious filter response characteristic of an omniscient 0PWy filter can be almost solved by providing a filter structure symmetrical with respect to the transmit centerline. ing. Figure 5 shows a 9"
A six-finger" cpw filter structure is shown. In this filter structure, a first conductor 60 and a second conductor 62 are coated on the sieve material 34 between the grounds Iji 36.

Conductors 60 and 62 have coupling portions 38 and 4°, respectively, with coupling portion 40 branching and extending to one side of portion 38. Since the conductors 50 and 32 and their coupling portions 68 and 4o are sheathed symmetrically about the centerline of transmission 42, all electric and magnetic fields are directed to the center 1!
42 and are symmetrical and equal fields.

Due to its symmetrical structure, the filter shown in FIG. 5 does not excite unwanted transmission modes and mode suppression is not required.

Equal even and odd modes in each conductor 60 and 32
To maintain the impedance Zoe and Zoot, the transmission line inserts 38 and 400 dimensions are CP from each line.
Since the 0 branch 40, which is chosen so that the total capacitance to the W ground plane 36 is equal, is closer to the ground plane 36 than the inner part 58, the branch can usually be made much narrower than the enlarged part 68. be. That is, in FIG. 5, dimension (C-B) is much smaller than dimension A.

The line structure shown in FIG.
) can be designed using technology.

The design can be carried out according to the following method of drawing the six-finger structure shown in FIG. 5 from the combined stripline model.

This problem can be solved by constructing a conformal diagram of the capacitance of the cross section using the problem line of the symmetrical coupling line and the ellipse integral. The cell shown in FIG. 6 illustrates the capacitance problem that is part of the stripline model of the coupled transmission line in the cross section. The cells shown on the composite plane are in the real part of a periodic structure in both the real and imaginary axes. This is the bond C shown in Figure 7.
Plotted on the PW line.

The analysis steps of the symmetric bond line problem can be summarized as follows. The dimensions of the coupling line are adjusted according to the desired even and odd modes.
Determined from impedance.

1) Calculate the normal line capacitance oe7 and the even and odd mode impedances for ac7g using equations (1), (2) and (3)t-.

However, Zoe and 200 are even and odd impedances, V'd stone/g O- is free space impedance, g
rFicPW@Specific-Electric Materials.

2) Using equations (4) and (5), 087g and Co/
a L#) K 2 e/to'26 and K 20/to'
Determine 20.

Kze Ce = ++ (4)
K'2θ a K2OG.

= - (51 to '20 g 6) Equations (6) and (7) K Using the general formula 1) of the complete ellipse integral shown in 2e/ to 'ze and 20/ to'
215 and 20 are calculated from 2Q. This calculation is based on the book published by Dover Publ in 1950, M.

Milne-ThOmas @Jacobi and
requires the numerical techniques described in "Elliptic Functions".

K′(6)=to/1−k”) (7
) Basically, for example, (to K)/K/(6))=G
e/@ for k by simultaneously solving equations (6) and (7), where k corresponds to 26 and '26'.
(k) Equations (6) and (7) to obtain 'GOt'
be inserted into each.

4) Determine kze and ktt using equation (8).

5) k using the full elliptical integral of equations (6) and (7).

Calculate 1 from and to .

6) Using equation (9), and from 'l to KO/KO
'Determine.

Ko K/ 1=2- (9) K'o
K, / 7) Determine Ko and ko from Ko7Ko' using the complete elliptic integral shown as equations (6) and (7).

8) Determine the quantity i (shown in FIG. 1) from , k, and 2o using the incomplete elliptic integral shown as equation (g) and equation (b).

9) Figure 5 and all! The last dimension shown in Figure 7, A
.

B and C are Ko using the equations as, On, (b) and (to).

Calculated from kO and C/a. It is the reciprocal of Jacobi's interelliptic function. This relationship is shown in Fi style.

A=sn(Ko ++, ko) Q1a -1as x= 5n(F(x, k), k) @
Table 5 shows the expression data output by the computer grograph using this method.

However, RR is the dielectric coefficient of the dielectric material, and zm is the even mode.
The impedance Zoe, zO is the odd mode end impedance Z00, and is shown in FIG.

E R= 10 Telh General & Dielectric Materials (Alto
The results of n) are as follows.

table ! 5QRT(ZO*ZIi:)=30.0
gR=10. o.

ZIC20A/D B/D C/D 35.025.70.8800.9860.9?740
．． 022.50.8620.9520.98845.0
20.00.8540.9070.97550.018
．． 00.8010.8560.95155.016.4
0.7620.8030.922 table 厘5QRT(ZO*ZK)=40.0 11i:R
=10.00Zg ZOA/D E/D O/D 45.055.60.7040.9840.99250
．． 032.00.6B90.9450.97155.0
29.10.6670.8880.94060.026
．． 70.6400.8270.90265.024.6
0,6090.7650.85870.022.90.
5760.7000.81275.021.30.54
10.6400.765 table 厘5QRT (zOshinZIC) = 40.0
gR=10. oOZIC20A/D g/D O/D 55.045.50.5200.9B50.98860
．． 041.70.5090.9590.95565.0
58.50.4950.8800.91170.055
．． 70.4740.8130.85875.055.5
0.4520.7430.80280.031.50.
4290.6750.74585.029.40.40
50.6100.689?0.027.80.5800
．． 5500.65595.026.50.3550.4
960.584 table W SQRT (2012g) = 40.0
1cR=10. oOzii; zom/D K/D C
/D65.055.40.3670.9B50.985
70.051.40.5600.9380.94675
．． 0 48.0 0.549 0.875 0
．． 89280.045.00.5570.8050.8
29B5,042.40.5220.7510.764
90.040.00.5070.6600.69995
．． 037.90.2900.5930.637100.
056.00.2740.5300.579105.0
34.30.2570.4740.525110.05
2.70.2400.4230.476 Table V SQRT(ZO*ZE)=40.0 1i:R=
10. oOZE ZOA/D Ii:/D O/D75
．． 0 65.5 0.255 0.982 0.984
80.0 61.3 0.249 0.936 0.9
40?0.0 54.4 0.254 0.799 0
．． 81195.0 51.6 0.225 0.723
0.740100.049.00.2140.650
0.670105.046.70.2040.5800
．． 603110.0 44.5 0.19!1 0.5
17 0.542115.0 42.6 0.182
0.459 0.487120.040.80.171
0.4070.436 A two-pole filter designed to have a bandwidth of 5 GH2 centered at 1 GHz using two cascaded filter sections t shown in Figure 5 was first constructed using the known filter synthesis technique [ r is used to determine the desired even and odd mode impedances in each sector: iI7, and the pattern dimensions are calculated using the programmatic conformal drawing technique described above. Once the proper dimensions have been calculated, the filter is fabricated using gold conductors on 50 mil (nil) thick alkaline material.

The layout and dimensions of the filter are shown in FIG. On the back side of the material, a resistive material with a thickness of 9 100ξ for odd mode suppression is added, and the measured filter response of this filter is approximately #1 in agreement with the theoretical value, as shown in Figure 9. did.

Since the filter according to the invention preferably has a semi-indeterminate or indeterminate ground plane on one side of the central conductor,
Not limited to the pattern shown in FIG. 5, it is preferable that the symmetrical shape of the pattern is as long as possible.

It goes without saying that the filter structure of the present invention can be modified without departing from the spirit and scope of the claims.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a conventional strip twin microwave filter, Fig. 2 is a cross-sectional view of the line drawing in Fig. 1, and Fig. 3 is a known coplanar waveguide microwave filter. FIG. 4 is a cross-sectional view of the casing shown in FIG. 5, FIG. 5 is a plan view of a coplanar waveguide filter according to the present invention, and FIGS. 6 and 7 are is a diagram for explaining the design of the filter according to the present invention, FIG. 8 is a plan view of the 6-sex rose filter according to the present invention, and FIG. 9 is a diagram showing the measurement and theory of the filter shown in FIG. 8. It is a figure which shows a response. F-6,6 ze1111 -nee-ni 11. □： ＾
BCD □

Claims (1)

[Claims] 1) at least one filter section coated on the substrate surface (64) and formed on nine pairs of ground conductors (36); and a filter section coated on the substrate surface between the ground conductors; A coplanar waveguide filter having a first (30) and a second (32) conductor, wherein: a) said pair of ground conductors are provided at equal distances from transmitter center #(42); and b) A coplanar waveguide filter, wherein the first and second conductors are each coated symmetrically with respect to the transmission center line. 2) The first and second conductors have ends (
38, 40) The coplanar waveguide filter according to claim 1, characterized in that it has: 3) The first and second conductors have inserted ends (38, 4
0) A coplanar waveguide filter according to claim 1, characterized in that the coplanar waveguide filter has: 4) The first conductor (60) has an end (38), and the second conductor (32) is coated on one side between the first conductor and the ground conductor, respectively. Coplanar waveguide filter according to claim 1, characterized in that it has at least a first and a second end (40) t-. 5) The device according to any one of claims 1 to 4, characterized in that each of the first and second conductors has the same overall capacitance with respect to ground. . 6) The total width of the second conductor (2(0-B)) is shorter than the total width of the first conductor (2), and each width is measured in a direction along the substrate surface perpendicular to the transmission center line. 7. The coplanar waveguide filter according to claim 6, wherein the coplanar waveguide filter is a coplanar waveguide filter. 7) Any one of claims 1 to 6, characterized in that at least one filter section comprises a plurality of filter sections connected in a skin-like cascade as shown in FIG. Coplanar waveguide filters as described in Section.