EP0068345A1 - Filter bestehend aus symmetrischen gekoppelten Koplanarleitungen - Google Patents

Filter bestehend aus symmetrischen gekoppelten Koplanarleitungen Download PDF

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Publication number
EP0068345A1
EP0068345A1 EP82105340A EP82105340A EP0068345A1 EP 0068345 A1 EP0068345 A1 EP 0068345A1 EP 82105340 A EP82105340 A EP 82105340A EP 82105340 A EP82105340 A EP 82105340A EP 0068345 A1 EP0068345 A1 EP 0068345A1
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EP
European Patent Office
Prior art keywords
conductors
filter
coplanar waveguide
conductor
waveguide filter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP82105340A
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English (en)
French (fr)
Inventor
Ronald E. Stegens
Gary G. Hawisher
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Comsat Corp
Original Assignee
Comsat Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Comsat Corp filed Critical Comsat Corp
Publication of EP0068345A1 publication Critical patent/EP0068345A1/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/2013—Coplanar line filters

Definitions

  • This invention is directed to microwave filters, and more particularly to such filters having a co- planar waveguide (CPW) construction.
  • CPW co- planar waveguide
  • Edge-coupled bandpass filters of the stripline or microstrip variety are. well-known. These may typically comprise a configuration as shown in figures 1 and 2 in which first and second stripline conductors 10 and 12 are deposited on the upper surface of a dielectric substrate 14 having a ground plane 16 on the lower surface thereof. In such a filter configuration, a signal on one of the conductors, for example conductor 10, will be coupled across a gap 18 to the other conductor 12, and these filters perform substantially as desired even when the transmission lines are asymmetrical.
  • the design techniques for microstrip filters are well-known and are described, for example, in Design of Microwave Filters, Impedance-Matching Networks, and Coupling Structures, by Matthaei et al, Section 8.09. The synthesis procedure generally begins from a low pass prototype, and yields required values for even and odd mode impedances Z oe and Z oo' respectively, for each coupled section.
  • the odd mode impedance Z can be considered the impedance of either conductor when both conductors have opposite potentials (i.e., +1 and -1 volt), while the even mode impedance Z oe can be considered the impedance of either conductor when both have the same potential.
  • the input and output conductors and the ground plane are all coplanar.
  • conductors 20 and 22 are disposed on the upper surface of the dielectric 24 in a configuration similar to that of Figure 1, and the ground plane 16 in Figure 2 is replaced by a pair of grounded conductors 26 on the upper surface of the dielectric and on either side of the conductors 20 and 22.
  • CPW edge-coupled filters as shown in Figure 3 using two edge-coupled lines exhibiting the desired Zoe and Z 00 values perform poorly due to their asymmetrical construction.
  • the conductor 20 will be closer than the conductor 22 to the upper ground conductor 26, and conversely the conductor 22 will be closer than the conductor 20 to the lower ground conductor 26.
  • This asymetrical coupling of the conductors 20 and 22 to the different ground conductors can cause field asymmetry about the center line of transmission 28, and this may result in the excitation of an odd mode of propagation between the ground planes.
  • This odd mode of propagation tends to cause unwanted transmission responses which are difficult to predict, and some type of suppression, e.g. the use of bond wires placed over the line from one ground plane to the other, is usually required to obtain even partially satisfactory performance.
  • CPW coplanar waveguide
  • the CPW filter according to the present invention comprises first and second conductors and first and second ground planes all disposed on the same surface of a dielectric substrate, the first conductor having an enlarged coupling portion and the second conductor having a bifurcated coupling portion interposed between said first conductor and each of said ground planes.
  • the first and second conductors are symmetrical with respect to the transmission center line at all points.
  • the filter according to the present invention is based on the recognition that the odd mode propagation resulting in spurious filter response characteristics in known CPW filters could be substantially eliminated by utilizing a filter structure which is symmetrical about the center line of transmission.
  • Figure 5 illustrates a "threefinger" CPW filter construction utilizing symmetrical interleaved transmission lines.
  • a first conductor 30 and second conductor 32 are disposed on a dielectric substrate 34 between ground planes 36.
  • the conductors 30 and 32 are each provided with coupling portions 38 and 40, respectively, and the coupling portion 40 is bifurcated and extends around either side of the portion 38.
  • the conductors 30 and 32 and their respective coupling portions 38 and 40 are symmetrically disposed with respect to the center tine of transmission 42 so that all electric and magnetic fields will have even field symmetry about the center line 42. Due to the symmetrical construction, the filter shown in Figure 5 will not tend to excite unwanted transmission modes, and no mode suppression is required.
  • the dimensions of the interleaved portions 38 and 40 of the transmission lines are chosen so that the total capacitances from each line to the CPW grounds planes 36 will be equal. Since the bifurcated portion 40 is much closer than the inner portion 38 to each of the ground planes 36, the dimensions of the bifurcated portions will generally be much narrower than the enlarged portion 38, i.e., the dimension (C-B) will be much less than the dimension A in Figure 5.
  • the line structure shown in Figure 5 can be designed using conformal mapping techniques for a zero conductor thickness, infinite dielectric and equal line capacitance for the pair of coupled lines.
  • the design can be implemented according to the following procedure which can be used to map the three-finger structure of Figure 5 from a coupled stripline model.
  • the symmetric coupled line problem revolves around the conformal mapping of a cross sectional capacitance problem, using elliptic integrals.
  • the cell in Figure 6 represents the capacitance problem as a part of a stripline model of the coupled transmission lines in cross section.
  • the cell, shown on the complex plane, is in reality part of a structure periodic along both real and imaginary axes. This is mapped into the coupled CPW line shown in Figure 7.
  • the steps used to solve the symmetric coupled CPW line problem are summarized below.
  • the dimensions of the coupled line are determined from the desired even and odd mode impedances.
  • (K(k)/K'(k)) Ce/ ⁇ can be solved for k by simultaneously solving Equations (6) and (7) and k can be plugged back into each of equations (6) and (7) to obtain K(k) and K'(k) corresponding to K 2e and K' 2e , respectively.
  • a two-pole filter utilizing two of the filter sections of Figure 5 coupled in cascade and designed for a 1 GHz bandwidth and centered at 5.0 GHz was built by first utilizing prior art filter synthesis techniques to determine the required even and odd-mode impedances for each filter section and then utilizing the conformal mapping techniques of the above- described program to calculate the pattern dimensions. After the proper dimensions were calculated, the filter was fabricated using gold conductors on a 50 mil thick alumina substrate. The filter layout and dimensions are shown in Fig. 8. A 100 mil thickness of resistive material was added to the bottom of the substrate for further odd mode suppression, and the measured filter response agrees very closely with theoretical calculations as shown in Figure 9.
  • the filter according to the present invention may have either semi-infinite or finite ground planes on either side of the center conductors, and it should be appreciated that patterns other than that shown in Figure 5 may be used as long as symmetry is preserved. Other modifications could also be made to the disclosed filter structure without departing from the spirit and scope of the invention as defined in the following claims.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
EP82105340A 1981-06-25 1982-06-18 Filter bestehend aus symmetrischen gekoppelten Koplanarleitungen Withdrawn EP0068345A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US27746681A 1981-06-25 1981-06-25
US277466 1981-06-25

Publications (1)

Publication Number Publication Date
EP0068345A1 true EP0068345A1 (de) 1983-01-05

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP82105340A Withdrawn EP0068345A1 (de) 1981-06-25 1982-06-18 Filter bestehend aus symmetrischen gekoppelten Koplanarleitungen

Country Status (3)

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EP (1) EP0068345A1 (de)
JP (1) JPS586601A (de)
IL (1) IL66092A0 (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2153155A (en) * 1984-01-24 1985-08-14 Secr Defence Improvements on or relating to microwave filters
EP0589704A1 (de) * 1992-09-24 1994-03-30 Matsushita Electric Industrial Co., Ltd. Mikrowellenfilter
GB2295277A (en) * 1994-11-16 1996-05-22 Philips Electronics Uk Ltd RF circuits with microstrip coupler
EP1562255A1 (de) * 2004-02-03 2005-08-10 NTT DoCoMo, Inc. Koplanares Filter
EP1691443A1 (de) * 2005-02-09 2006-08-16 NTT DoCoMo INC. Koppelstruktur, Resonatoranregungsstruktur und Filter für eine koplanare Schaltung
DE102007041125B3 (de) * 2007-08-30 2009-02-26 Qimonda Ag Sensor, Verfahren zum Erfassen, Messvorrichtung, Verfahren zum Messen, Filterkomponente, Verfahren zum Anpassen eines Transferverhaltens einer Filterkomponente, Betätigungssystem und Verfahren zum Steuern eines Betätigungsglieds unter Verwendung eines Sensors
US7782066B2 (en) 2007-08-30 2010-08-24 Qimonda Ag Sensor, method for sensing, measuring device, method for measuring, filter component, method for adapting a transfer behavior of a filter component, actuator system and method for controlling an actuator using a sensor

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2859417A (en) * 1952-05-08 1958-11-04 Itt Microwave filters
US3820041A (en) * 1972-08-28 1974-06-25 J Gewartowski Resonance control in interdigital capacitors useful as dc breaks in diode oscillator circuits

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2859417A (en) * 1952-05-08 1958-11-04 Itt Microwave filters
US3820041A (en) * 1972-08-28 1974-06-25 J Gewartowski Resonance control in interdigital capacitors useful as dc breaks in diode oscillator circuits

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
CONFERENCE PROCEEDINGS OF THE 6th EUROPEAN MICROWAVE CONFERENCE, 14th/17th September 1976, pages 49-53, Sevenoaks (GB); *

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2153155A (en) * 1984-01-24 1985-08-14 Secr Defence Improvements on or relating to microwave filters
EP0589704A1 (de) * 1992-09-24 1994-03-30 Matsushita Electric Industrial Co., Ltd. Mikrowellenfilter
US5461352A (en) * 1992-09-24 1995-10-24 Matsushita Electric Industrial Co., Ltd. Co-planar and microstrip waveguide bandpass filter
CN1050703C (zh) * 1992-09-24 2000-03-22 松下电器产业株式会社 带通滤波器
GB2295277A (en) * 1994-11-16 1996-05-22 Philips Electronics Uk Ltd RF circuits with microstrip coupler
US7378924B2 (en) 2004-02-03 2008-05-27 Ntt Docomo, Inc. Filter with improved capacitive coupling portion
CN100385729C (zh) * 2004-02-03 2008-04-30 株式会社Ntt都科摩 滤波器
EP1562255A1 (de) * 2004-02-03 2005-08-10 NTT DoCoMo, Inc. Koplanares Filter
EP1691443A1 (de) * 2005-02-09 2006-08-16 NTT DoCoMo INC. Koppelstruktur, Resonatoranregungsstruktur und Filter für eine koplanare Schaltung
KR100820285B1 (ko) * 2005-02-09 2008-04-07 가부시키가이샤 엔티티 도코모 코플레너 평면 회로내 결합구조, 공진기 여진구조 및 필터
US7397331B2 (en) 2005-02-09 2008-07-08 Ntt Docomo, Inc. Coupling structure, resonator excitation structure and filter for coplanar-waveguide circuit
CN100466374C (zh) * 2005-02-09 2009-03-04 株式会社Ntt都科摩 共面平面电路内耦合结构、谐振器激励结构以及滤波器
EP2065964A1 (de) * 2005-02-09 2009-06-03 NTT DoCoMo, Inc. Koppelstruktur, Resonatoranregungsstruktur und Filter für eine koplanare Schaltung
DE102007041125B3 (de) * 2007-08-30 2009-02-26 Qimonda Ag Sensor, Verfahren zum Erfassen, Messvorrichtung, Verfahren zum Messen, Filterkomponente, Verfahren zum Anpassen eines Transferverhaltens einer Filterkomponente, Betätigungssystem und Verfahren zum Steuern eines Betätigungsglieds unter Verwendung eines Sensors
US7782066B2 (en) 2007-08-30 2010-08-24 Qimonda Ag Sensor, method for sensing, measuring device, method for measuring, filter component, method for adapting a transfer behavior of a filter component, actuator system and method for controlling an actuator using a sensor

Also Published As

Publication number Publication date
IL66092A0 (en) 1982-09-30
JPS586601A (ja) 1983-01-14

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Inventor name: STEGENS, RONALD E.