EP0373028B1 - Passives Bandpassfilter - Google Patents

Passives Bandpassfilter Download PDF

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Publication number
EP0373028B1
EP0373028B1 EP89403257A EP89403257A EP0373028B1 EP 0373028 B1 EP0373028 B1 EP 0373028B1 EP 89403257 A EP89403257 A EP 89403257A EP 89403257 A EP89403257 A EP 89403257A EP 0373028 B1 EP0373028 B1 EP 0373028B1
Authority
EP
European Patent Office
Prior art keywords
filter
impedance
microstrips
input
substrate
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.)
Expired - Lifetime
Application number
EP89403257A
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English (en)
French (fr)
Other versions
EP0373028A1 (de
Inventor
Henri Budan
Patrick Algani
Alain Grosjean
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.)
Thomson Hybrides
Original Assignee
Thomson Hybrides
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Filing date
Publication date
Priority claimed from FR8815664A external-priority patent/FR2639776B1/fr
Application filed by Thomson Hybrides filed Critical Thomson Hybrides
Publication of EP0373028A1 publication Critical patent/EP0373028A1/de
Application granted granted Critical
Publication of EP0373028B1 publication Critical patent/EP0373028B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • H01P1/203—Strip line filters
    • H01P1/20327—Electromagnetic interstage coupling
    • H01P1/20336—Comb or interdigital filters

Definitions

  • the present invention relates to a passive bandpass filter, produced using hybrid circuit technology.
  • the structure of this passive filter makes it possible to adapt it, in the microwave domain, to the desired central frequency with a good rate of rejection of the lower frequencies. It is produced in the form of microstrips on a ceramic substrate.
  • FIG. 1 An example is given in FIG. 1, on which two combs of interdigitated microstrips 1 and 2 are deposited on a substrate 3.
  • the microstrips have a length ⁇ g / 4, ⁇ g being the wavelength guided in a microstrip, and their point common is joined to the ground plane which is on the rear face of the substrate 3.
  • the signal input E is applied to a free end of the first microstrip of a first comb, and the filtered output S is collected at one end free of the last microstrip of a second comb.
  • These known filters have two types of drawbacks. First, they occupy a relatively important place.
  • hybrid circuit techniques are influenced by the density of integrated circuits that are reported on a hybrid circuit substrate, especially VLSIs with very high integration density, and the components reported on a hybrid circuit must also be densified, especially if they operate at microwave frequencies.
  • the passive bandpass filter according to the invention eliminates these two drawbacks. It occupies only a small surface on a dielectric substrate, and its response curve is clear: outside the bandwidth, it virtually cuts outside frequencies, especially lower frequencies.
  • microstrip line It consists of a plurality of microstrip lines, mutually parallel, all the ends of which on the same side are joined to the ground plane carried by the opposite face of the dielectric substrate.
  • the signal input E is applied to the first microstrip and the output S of the filtered signal is collected on the last microstrip.
  • at least two non-neighboring microstrip lines therefore not coupled by electromagnetics, are coupled by an impedance, self or capacitance, reported on the substrate.
  • the distances from the ground points, to which the input, output and impedance connections are connected, are used to adjust the input and output impedances and to modify the shape of the filter response curve. .
  • This type of bandpass filter makes it possible to obtain a response curve for the passband whose flanks are relatively steep, because the coupling impedance cancels a term from the denominator of the equation of transfer through the filter.
  • a first improvement to this bandpass filter consists in providing it with an additional impedance, at its input, which cancels a second term in the transfer equation, and makes the sides of the response curve more abrupt.
  • a second improvement consists in folding the band-pass filter over itself, in the same way as one closes a book. This makes it a smaller component, the dimensions of which are in accordance with its environment of integrated circuits or miniaturized components.
  • the invention relates to a passive bandpass filter, produced by means of microstrips deposited on one face of a dielectric substrate, comprising at least three microstrips, parallel to each other, one end of which is joined by means appropriate to the ground plane carried by the second face of the substrate, at least two of said microstrips, not neighboring on the substrate, being coupled by a coupling impedance Z, which is a self or a capacitance, this filter being characterized in that, with a view to reducing its bulk, it is folded back on itself along a median line perpendicular to the microstrips, and jumpers allowing the passive filter to be fixed by its access and ground plane connections.
  • the passive filter according to the invention is supported by a substrate 4, one face of which is metallized at 5 to form a ground plane.
  • This substrate is made of ceramic, alumina or materials with a high dielectric constant (9 ⁇ ⁇ ⁇ 100), and its thickness is between 0.3 and 1 mm approximately.
  • microstrip lines On the non-metallized face of this substrate 4 are deposited a plurality of microstrip lines, parallel to each other. At least three microbands 6, 7, 8 are required so that at least two of them are not neighboring. By one of their ends, but on the same side for all the microstrip lines, these are joined to the ground plane 5: in the figure, this connection is made by means of metallized holes 9, but other known means are possible.
  • These lines microstrips are produced either by thick film technology, by screen printing, or by thin film technology, by vacuum evaporation.
  • the input E of the signal to be filtered is applied laterally to the first band 6 of the series by means of a metallization 10 which, generally, is oriented towards the edge of the substrate 4, or towards the signal generator if the latter is integrated on the same substrate.
  • the filtered output signal S is collected on a metallization 11, lateral on the last strip of the series.
  • the metallizations 10 and 11 are, respectively, at distances x1 and x2 from the ends to the mass of the two microstrip lines considered.
  • two non-neighboring microstrip lines are coupled by an impedance Z 12, joined by two wires or metallizations 13 and 14 at two points, respectively, of the first strip 6 and the second band 8 not neighboring.
  • the impedance Z is either a self or a capacitor, deposited on the substrate 4 in the form of a discrete component or in the form of thick layers.
  • the wires or metallizations 13 and 14 are fixed on the two non-neighboring microstrip lines at distances x3 and x4, respectively, from the ends to the mass of the two microstrip lines considered.
  • the displacement of the input metallization 10, by varying x1, makes it possible to adapt the impedance to 75 or 100 ohms, or to some other value.
  • the distance x2 makes it possible to adjust the output impedance of the passive filter.
  • the central frequency of the bandpass filter is adjusted by the length L of the microstrip lines.
  • the bandwidth of the filter is adjusted by the width "l" of the lines, and by the spacing "d” between lines.
  • the spacing "d” plays the same role as the width "l” but more important.
  • microstrips and / or narrow spacings give wide bandwidths and low TOS.
  • Narrow microstrips and / or wide spacings give narrow bandwidths and high TOS.
  • the distances x3 and x4 make it possible to optimize the coupling between two non-neighboring microstrips: they define the input impedance and the output impedance linked to the capacitance or self Z 12, and are calculated according to the specifications required for the filtered.
  • a filter according to the invention of one or more uncoupled microstrips improves the rejection of frequencies outside the central frequency, and makes the response curve more "square"".
  • a filter according to the invention can comprise more than three microstrips as shown in FIG. 2. Let us take the case of a filter with 4 microstrips, which will be called A, B, C, D. Different couplings can be carried out: A-D coupling or A-C and B-D coupling. The choice is made according to the specifications imposed on the filter.
  • FIG. 4 A first improvement to the filter according to the invention is shown in FIG. 4. They consist in adding to the input E of the filter a double impedance Z1 and Z2.
  • the impedance Z1 is provided by a microstrip 17, finer and of higher impedance than the microstrips 6,7,8 of the filter. Typically, it is about 200 micrometers wide, and a length equal to ⁇ / 4. Unlike other microstrips, it has no end joined to the ground plane 5.
  • this impedance Connected in parallel on the input circuit, this impedance resonates for the rejection frequency. It cancels a second term in the filter transfer equation, which completes the action of the impedance 12 of the filter, which cancels a first term.
  • Impedance 17 can also be achieved by a line and a capacity.
  • Impedance Z2 corrects the deterioration of the input impedance, brought by Z1. Placed in series between the input E of the filter, and the connection point on the first microstrip 6, it can be performed either by a line 18, or by a line and a capacitor.
  • the characteristic impedances of 17 and 18 are interactive, and calculated to obtain the desired slope and rejection level, on the response curve of the filter.
  • the second improvement makes it possible to produce a bandpass filter even smaller than that of the main invention.
  • a filter according to the invention only the substrate 4 is reported with its ground plane 5, and three microstrips 6,7,8 with an input E and an output S.
  • this filter could comprise more than three bands , and the impedances 17 and 18 of the first improvement.
  • the second improvement consists in cutting the filter along a line 19 which, perpendicular to the microstrips 6,7,8, separates it into two equal parts, in the direction of the length of the substrate 4. The two parts are then, as shown on the right of the figure, brazed one on the other, by their faces supporting the ground plane 5.
  • microstrips 6,7,8, the halves of which are now carried by the upper and lower faces of a sandwich including in its center a ground plane 5, are reformed by means of jumpers or metallizations 20, on the side of the sandwich: the electrical continuity of each microstrip is thus ensured.
  • microstrips must be slightly shorter in length than ⁇ g / 4: the length of the jumpers 20, equal to twice the thickness of the substrate 4, reduces this length to ⁇ g / 4.
  • jumpers 21, or other suitable external connections are fixed to the edges of the sandwich.
  • a minimum of three jumpers 21 is required, corresponding to the input E, the output S and the ground plane 5.
  • These jumpers are provided with means 22 for either implanting the component in the holes of a substrate, or mounting it in SMD (surface mountable components).
  • SMD surface mountable components
  • This type of passive filter is used in information processing systems, for example in radio telephones, in the range 0.5 to 10 GHz, with a bandwidth of 0.9 to 1 GHz.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
  • Filters And Equalizers (AREA)
  • Networks Using Active Elements (AREA)

Claims (4)

  1. Passives Bandpaßfilter in Hybridtechnologie mit wenigstens drei zueinander parallelen, von einer Seite eines dielektrischen Substrats (4) getragenen Mikrobändern (6, 7, 8), von denen ein Ende durch geeignete Mittel (9) mit der von der zweiten Seite des Substrats (4) getragenen Masseebene (5) verbunden ist, wobei wenigstens zwei Mikrobänder (6, 8), die auf dem Substrat (4) nicht benachbart sind, durch eine Kopplungsimpedanz Z (12) gekoppelt sind, die eine Selbstinduktivität oder eine Kapazität ist, wobei das Filter dadurch gekennzeichnet ist, daß es zur Verringerung seines Platzbedarfs längs einer zu den Mikrobändern (6, 7, 8) senkrechten Mittellinie (19) in sich gefaltet ist, wobei Stecker (21) die Befestigung des passiven Filters durch seine Zugangs- (E-S) und Masseebene-Anschlüsse (5) ermöglichen.
  2. Passives Filter nach Anspruch 1, dadurch gekennzeichnet, daß es ferner parallel zu dem Eingang (E) des Filters eine erste Impedanz (17) mit hohem Wert und in Reihe mit dem Eingang (E) eine zweite Impedanz (18) zur Korrektur der Eingangsimpedanz aufweist.
  3. Passives Filter nach Anspruch 1, dadurch gekennzeichnet, daß die erste Impedanz (17) durch ein Mikroband mit einer Länge λg/4, wobei λg die Wellenlänge bei der Arbeitsfrequenz des Filters ist, und mit geringer Breite zur Erhöhung der Impedanz gebildet ist.
  4. Passives Filter nach Anspruch 1, dadurch gekennzeichnet, daß die zweite Impedanz (18) durch ein Mikroband gebildet ist.
EP89403257A 1988-11-30 1989-11-24 Passives Bandpassfilter Expired - Lifetime EP0373028B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
FR8815664 1988-11-30
FR8815664A FR2639776B1 (fr) 1988-11-30 1988-11-30 Filtre passif passe-bande
FR898908017A FR2648641B2 (fr) 1988-11-30 1989-06-16 Filtre passif passe-bande
FR8908017 1989-06-16

Publications (2)

Publication Number Publication Date
EP0373028A1 EP0373028A1 (de) 1990-06-13
EP0373028B1 true EP0373028B1 (de) 1994-05-18

Family

ID=26227020

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89403257A Expired - Lifetime EP0373028B1 (de) 1988-11-30 1989-11-24 Passives Bandpassfilter

Country Status (6)

Country Link
EP (1) EP0373028B1 (de)
AT (1) ATE105976T1 (de)
CA (1) CA2004184A1 (de)
DE (1) DE68915408T2 (de)
FI (1) FI895714A0 (de)
FR (1) FR2648641B2 (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2669476A1 (fr) * 1990-11-21 1992-05-22 Valtronic France Filtre passif passe-bande.
DE19652799C2 (de) * 1996-12-18 1999-05-20 Siemens Ag Mikrowellenfilter
ES2143964B1 (es) * 1998-09-15 2000-12-01 Univ Catalunya Politecnica Diplexor dual para telefonia celular gsm y dcs.
KR100392682B1 (ko) * 2001-02-26 2003-07-28 삼성전자주식회사 주파수 차단회로를 가지는 콤라인 구조의 무선필터 및 그구현 방법
US10862185B2 (en) 2017-12-01 2020-12-08 Semiconductor Components Industries, Llc Integrated circuit with capacitor in different layer than transmission line

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1906059A1 (de) * 1969-02-07 1970-08-13 Licentia Gmbh Kammfilter
JPS49119170A (de) * 1973-03-19 1974-11-14
DE2407313A1 (de) * 1974-02-15 1975-08-21 Kathrein Werke Kg Resonatoranordnung
US4253073A (en) * 1978-08-17 1981-02-24 Communications Satellite Corporation Single ground plane interdigital band-pass filter apparatus and method
US4706050A (en) * 1984-09-22 1987-11-10 Smiths Industries Public Limited Company Microstrip devices
FR2578104B1 (fr) * 1985-02-27 1987-03-20 Alcatel Thomson Faisceaux Filtre passe-bande pour hyperfrequences
US4740765A (en) * 1985-09-30 1988-04-26 Murata Manufacturing Co., Ltd. Dielectric filter
JPS62260401A (ja) * 1986-05-02 1987-11-12 Murata Mfg Co Ltd ストリツプラインフイルタ
FR2613557A1 (fr) * 1987-03-31 1988-10-07 Thomson Csf Filtre comportant des elements a constantes reparties associant deux types de couplage

Also Published As

Publication number Publication date
DE68915408D1 (de) 1994-06-23
FR2648641B2 (fr) 1994-09-09
CA2004184A1 (en) 1990-05-31
ATE105976T1 (de) 1994-06-15
FI895714A0 (fi) 1989-11-29
FR2648641A2 (fr) 1990-12-21
EP0373028A1 (de) 1990-06-13
DE68915408T2 (de) 1994-09-08

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