US3316510A - Electrical ladder-type filter - Google Patents

Electrical ladder-type filter Download PDF

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Publication number
US3316510A
US3316510A US556778A US55677866A US3316510A US 3316510 A US3316510 A US 3316510A US 556778 A US556778 A US 556778A US 55677866 A US55677866 A US 55677866A US 3316510 A US3316510 A US 3316510A
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Prior art keywords
circuit
disposed
branch
circuits
transverse
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US556778A
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English (en)
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Poschenrieder Werner
Gotz Gerhard
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Siemens and Halske AG
Siemens AG
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Siemens AG
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/542—Filters comprising resonators of piezoelectric or electrostrictive material including passive elements

Definitions

  • the invention disclosed herein is concerned with an electrical ladder-type filter, comprising at least one transverse branch containing an electromechanical oscillator at which appears, as seen in theladder at the terminals of the transverse branch, in addition to the series resonance of the electromechanical oscillator, which produces an attenuation pole, at least one parallel resonance frequency (repetition frequency) lying in the filter barrier range, the action of which is compensated by an attenuation produced in preceding and/or succeeding filter elements.
  • a ladder circuit of particular construction is frequently being used at the present time for making low pass filters and band pass filters with quartzes or other electromechanical oscillators. It is important in connection with these ladder circuits, on the one hand, that an electromechanical oscillator for the production of an attenuation pole is used in the transverse branch of the filter, and on the other hand, that so-called repetition poles appear directly adjacent to both sides of the branch containing the oscillator, that is, barrier points with substantially the same resonance frequency which produce, however, only one operating attenuation pole which coincides at least approximately with the parallel resonance appearing in the transverse branch and lying in the filter barrier range.
  • the result obtained by this ladder circuit resides in that the structure of the electromechanical oscillator, especially the oscillator quartz, appears in the electrical equivalent or analog filter circuit in the desired manner.
  • the problem and object of the invention reside in improving the properties of such ladder circuits, primarily so as to produce a particularly favorable ratio of static to dynamic capacity of the oscillator used, which may be a piezoelectric oscillator.
  • an advantageous embodiment for the realization of a low pass filter or of a band pass filter with steeply rising attenuation flanks is obtained by using in the transverse branch, as an electromechanical oscillator, a piezoelectric element, preferably an oscillating quartz.
  • Further advantageous embodiments of the invention are obtained by effecting the compensation by two parallel resonance circuits with identical intrinsic resonance fre quency, whereby one such resonance circuit is allocated to a preceding and the other to a succeeding longitudinal branch, or by effecting the compensation by two series resonance circuits with identical intrinsic resonance frequency, which resonance circuits are arranged in transverse branches, whereby one such series resonance circuit is disposed ahead of the transverse element containing the oscillating quartz while the other in disposed following this transverse element.
  • an advantageous embodiment is obtained by using in the transverse branch, with the aid of a dual circuit, a magnetostrictive element in place of the piezoelectric element.
  • FIG. 1 shows a portion of a known ladder-type band pass filter
  • FIG. 2 indicates equivalent circuits for transforming elements shown in FIG. 1;
  • FIG. 3 represents the result of the transformation according to FIG. 2;
  • FIG. 4 indicates another ladder-type circuit obtained by transformation of elements shown in FIG. 3;
  • FIG. 5 shows equivalent circuits for effecting a trans forrnation with respect to FIG. 4;
  • FIG. 6 illustrates a circuit obtained by transformation with the aid of the elements shown in FIG. 5;
  • FIGS. 7 to 10 illustrate embodiments of the invention in which two-port nets are connected between the transverse branch containing the mechanical oscillator and respective resonance circuits which may be either parallel resonance circuits or series resonance circuits.
  • FIG. 1 shows, as noted above a portion of a known ladder-type band pass filter, wherein an attenuation pole is produced at the point jm of the attenuation diagram, by the series resonance of the piezoelectric oscillator indicated by a straight arrow.
  • quartz is represented by its electrical equivalence or analog circuit, namely, by the element L C and G In the transverse branch of this circuit, in which the piezoelectric oscillator is disposed in parallel with an inductance L there appears a parallel resonance frequency f,-
  • the parallel circuits 1 and 2 which produce the repetition pole are di- 7 mensioned so that their intrinsic resonance frequency f coincides approximately with the parallel resonance frequency f of the transverse branch referred to (f f whereby the apparent input resistance of the circuit assumes at the point 3:12. again approximately the value infinity, thereby avoiding an attenuation break-through at this point.
  • the arrangement also contains in the longitudinal branch, the parallel resonance circuits 3 and 4, such circuits producing further attenuation poles at the frequencies fw and f as Well as the parallel resonance circuits 5 and 6 in transverse branches, which aredimensioned according to further requirements posed for the filter.
  • the dash lines indicate that there may be provided further circuit elements at the respec.
  • the repetition frequency fwQ of the parallel resonance circuits 1 and 2 coincide in the circuit according to FIG. 3 at least substantially with the parallel resonance frequency f lying in the filter barrier range of the transverse branch containing the oscillation quartz (fx mg).
  • the circuit transformation entailed addition of the capacitor C and C and of the ideal transformers A and B.
  • the transformers are placed at'the input or the output I of the circuit, which as is known merely signifies respectively a multiplication of all inductivities or a division of all capacitances of the respective circuit section, with the value u.
  • the parallel resonance circuits land 2, which produce the repetition pole, are not affected by the transformation and the intrinsic resonance frequency lies now as before at the frequency fa
  • the 7 addition of capacitors C7 to C capacitors C and C likewise appear in the circuit.
  • the capacitors C and C are added by the transformation.
  • the parallel circuits 3 and 4 with the intrinsic frequencies fm and fa also appear again in the longitudinal branch of the circuit.
  • the apparent resistance depending upon the frequencywhereby the input and the output of the filter can be terminated with real resistances, the value of which issuitably equal to the wave impedance of the filterthere will appear zero points and infinity points in the course of the apparent resistance.
  • One of the infinity points corresponds to the repetition frequency fang, to which are tuned the parallel resonance circuits 1 and 2 which are disposed in the longitudinal branch and produce the repetitionpole.
  • the circuit transformation results in the addition of capacitors C and C as well as the coils L and L Since the capacitances C and C are due to the parallel connection to the original quartz capacitance C additive, the ratio of the static capacitance which now consists of C +C +C to the dynamic capacitance C is increased, which is extraordinarly advantageous for the realization of the oscillation quartz.
  • the newly added elements C C and L which are disposed parallel with the original quartz, effect moreover a shifting of the original parallel resonance frequency f of the transverse branch containing the oscillation quartzconsidering such transverse branch by itselfto a new value f which is in FIG. 4 again indicated by a semicircular arrow.
  • the parallel resonance frequency 3 lies as a rule adjacent to the repetition frequency or adjacent to one of the other pole frequencies 12. or fa so that the finite attenuation based upon these attenuation that the repetition pole can also be realized with the aid ofseries resonance circuits which are disposed in transverse branches of the arrangement.
  • the bracketed twoport nets VPV and VPVI which consist of half-elements comprising respectively the, capacitor C and parallel circuit 1 and the capacitor C and parallel circuit 2, are for this purpose transformed with the aid of known equivalent circuits according to FIG. 5. The corresponding transformation results in the circuit shown in FIG. 6;
  • the capacitors C and C; as well as the parallel resonance circuits 3 and 4 remain unchanged by the transformation, that is, they remain as they also appear in FIG. 4.
  • the capacitances C C and C of FIG. 4 are combined to form the static quartz capacitance C and there applies the relation
  • the inductivities L L and L of FIG. 4 are combined to form the inductivity L according to the relation
  • the parallel resonance frequency f appearing in the transverse branch containing the oscillation-quartz thus remains preserved.
  • the transformation effects formation of the repetition pole at the point ja by the series resonance circuits 9' and 10 which lie in transverse branches of the arrangement and cause at the frequency n practically a shunt, such con-v dition being indicated by straight arrows.
  • each of these circuits there is provided in a transverse branch an electromechanical oscillator Q, whereby an inductivity L and a balancing capacitor C, which may be connected in parallel therewith.
  • Two-port nets D and E are respectively disposed at the sides of the transverse branch which contains the quartz.
  • the repetition pole is in FIG. 7 produced by the parallel resonance circuits 1 and 2 (see also FIG. 4), which are disposed in the longitudinal branch of the circuit.
  • the parallel oscillation circuit 1 is connected ahead of the two-port net D and the parallel oscillation circuit 2 is disposed serially following the two-port net E.
  • the repetition ole is produced by two series resonance circuits 9 and which are disposed in transverse branches (see also FIG. 6).
  • the series oscillation circuit 9 is disposed ahead of two-port net D and the series oscillation circuit 10 is disposed serially following the two-port net E.
  • the repetition pole is produced by the series resonance circuit 11 lying in a transverse branch and by a arallel resonance circuit 12 lying in a longitudinal branch.
  • the series circuit 11 is disposed ahead of the two-port net D while the parallel circuit 12 is disposed serially following the two-port net E.
  • the two oscillation circuits 11 and 12 are tuned to the identical resonance frequency fraz-
  • the repetition pole is produced by a parallel oscillator circuit 13 disposed ahead of the two-port net D and by a series oscillation circuit 14 disposed serially following the two-port net E.
  • At least one attenuation pole is produced with an electromechanical oscillator in ladder circuit.
  • FIGS. 4 and 6 Two band pass filter circuits (FIGS. 4 and 6) have been explained to bring out the invention more clearly, such circuits having, disposed in a transverse branch, an oscillating quartz, and being obtained by circuit transformation with the aid of equivalence circuits.
  • the circuits according to FIGS. 4 and 6 as well as those accord- 6 ing to FIGS. 7 to 10 can 'be respectively calculated or designed according to the image parameter theory or according to the insertion loss theory, by a corresponding analysis of the circuit elements of a matrix according to the principle of the repetition poles.
  • An electrical ladder-type filter circuit having an electromechanical oscillator disposed in a transverse branch which generates an attenuation pole in the blocking range of the filter, a circuit element disposed in parallel with the electromechanical oscillator, as a result of which a parallel resonance frequency lying in the filter blocking range occurs in said transverse branch, a two-port net disposed in said circuit preceding said transverse branch and a twoport net disposed in said circuit following said transverse branch, said two-port nets each containing at least one longitudinal branch and one transverse branch, with a longitudinal branch of each disposed adjacent the transverse branch containing the electromechanical oscillator, a resonance circuit connected ahead of the first mentioned two-port net which is disposed in a branch thereat of said filter circuit, and a resonance circuit connected behind said second mentioned two-port net which is disposed in a branch thereat of said filter circuit, the resonance frequency of said last mentioned resonance circuits disposed ahead of and behind said two-port nets corresponding, at least approximately, to the parallel resonance frequency occurring in the filter
  • a filter according to claim 1 wherein said resonance circuits disposed ahead of and following said two-port nets are like resonance circuits with identical intrinsic resonance frequency, disposed in like branches ahead of and following the transverse branch containing said electromechanical oscillator.
  • a filter according to claim 2, wherein said resonance circuits are parallel resonance circuits disposed in respective longitudinal branches.
  • a filter according to claim 2, wherein said resonance circuits are series resonance circuits disposed in respective transverse branches.
  • a filter according to claim 1 wherein, of said resonance circuits disposed ahead of and following said twoport nets, one of said circuits is a series resonance circuit disposed in a transverse branch, and the other circuit is a parallel resonance circuit disposed in a longitudinal branch.
  • a filter according to claim 5 wherein the resonance circuit disposed ahead of the preceding two-port branch.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
  • Oscillators With Electromechanical Resonators (AREA)
US556778A 1962-04-05 1966-06-10 Electrical ladder-type filter Expired - Lifetime US3316510A (en)

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DES0078852 1962-04-05

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3530408A (en) * 1966-06-15 1970-09-22 Marconi Co Ltd Dispersive networks
US3613032A (en) * 1970-03-19 1971-10-12 Hughes Aircraft Co Composite crystal filter circuit
US3794938A (en) * 1971-05-03 1974-02-26 Gen Aviat Electronics Inc Coupled bandstop/bandpass filter
US5260675A (en) * 1991-04-12 1993-11-09 Ngk Spark Plug Co., Ltd. Ladder-type electric filter device
US20050132645A1 (en) * 2003-12-19 2005-06-23 Milt Johns Arbor stake

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3530408A (en) * 1966-06-15 1970-09-22 Marconi Co Ltd Dispersive networks
US3613032A (en) * 1970-03-19 1971-10-12 Hughes Aircraft Co Composite crystal filter circuit
US3794938A (en) * 1971-05-03 1974-02-26 Gen Aviat Electronics Inc Coupled bandstop/bandpass filter
US5260675A (en) * 1991-04-12 1993-11-09 Ngk Spark Plug Co., Ltd. Ladder-type electric filter device
US20050132645A1 (en) * 2003-12-19 2005-06-23 Milt Johns Arbor stake

Also Published As

Publication number Publication date
DE1616687A1 (de) 1973-08-23
DE1616687B2 (de) 1975-10-09
SE315962B (xx) 1969-10-13

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