US2342875A - Wave filter - Google Patents

Wave filter Download PDF

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Publication number
US2342875A
US2342875A US446479A US44647942A US2342875A US 2342875 A US2342875 A US 2342875A US 446479 A US446479 A US 446479A US 44647942 A US44647942 A US 44647942A US 2342875 A US2342875 A US 2342875A
Authority
US
United States
Prior art keywords
lattice
filter
capacitances
capacitors
branches
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
US446479A
Other languages
English (en)
Inventor
George H Lovell
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.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
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
Priority to NL134514D priority Critical patent/NL134514B/xx
Priority to BE473973D priority patent/BE473973A/xx
Priority to NL83190D priority patent/NL83190C/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US446479A priority patent/US2342875A/en
Application granted granted Critical
Publication of US2342875A publication Critical patent/US2342875A/en
Priority to CH265654D priority patent/CH265654A/de
Priority to FR948264D priority patent/FR948264A/fr
Priority to GB17026/47A priority patent/GB624292A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/0023—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns, or networks having balanced input and output
    • H03H9/0095—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns, or networks having balanced input and output using bulk acoustic wave devices
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B15/00—Drawing glass upwardly from the melt
    • C03B15/02—Drawing glass sheets
    • C03B15/08—Drawing glass sheets by means of bars below the surface of the melt
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; 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

  • This invention relates to wave transmission networks and more particularly to wave filters of the lattice type.
  • An object of the invention is to reduce the number of component elements required to build wave filters of the lattice typ especially thosev using piezoelectric crystals.
  • Another object 01 the invention is to increase the stability of filters of this type.
  • these capacitances will be of approximately the same value.
  • the practice has been to take part of each of these capacitances outside of the lattice and connect it inshunt at the ends of the network.
  • the rest of the required capacitances are furnished by two fixed capacitors connected in shunt, respectively, with the crystal impedances of one pair, and two variable capacitors connected in shunt, respectively, with the crystal impedances of the otherpair.
  • Inductances may be added at the ends of the lattice to increase the width of the transmission band, if desired.
  • all four of the capacitors within the lattice are replaced by a single diil'erential capacitor which furnishes two variable capacitances, one of which increases in value as the other is decreased.
  • One of these capacitances is connected in shunt with a crystal impedance in oneof the pairs and the other capacitance is connected in shunt with a crystal impedance in the other pair.
  • Adjustment oi the dlflerential capacitor permits a very accurate placement of the peaks of at tenuatlon in the filter characteristic.
  • a single differential capacitor crystals in one of the pairs of impedances are resonant at a common frequency and ant-1- resonant at a. higher common frequency:
  • the crystals in the other pair 01' impedances are antiresonant at or near the resonant frequency of the crystals in the one pair and resonant at. a lower common frequency.
  • Equal capacitors 9 and iii are connected in shunt at the ends oi the lattice. These are preferably made variable, as indicated, primarily to provide for an adjustment of the width of the transmission band. In order to widen the band four equal inductors l5, I6, I!
  • each capacitance has a range above and below C.
  • One of these variable capacitances is connected in shunt with a crystal impedance in one of the pairs and the other capacitance is connected in shunt with a crystal impedance in the other pair.
  • these crystal impedances are l and 4. They could as well be I and 3, 2 and 3 or 2 and 4. It is unnecessary to find by trial across which crystal impedance the capacitances should be connected.
  • the peaks of attenuation in the transmission characteristic of the filter may be accurately placed at the desired frequencies.
  • the lattice may be slightly unbalanced, since there is no corresponding adjustment of the capacitances associated with /the other two crystal impedances.
  • practical experience with the filter has shown that the height of the attenuation peaks is decreased by a meshgible amount since, ordinarily, an adjustment of only a few micromicrofarads is involved. Material savings are effected in the number of component elements required, cost and size of the filter and adjusting time. In addition, the filter is more stable.
  • a wave filter comprising four impedance branches and a diflerential capacitor, each of said branches including a piezoelectric crystal impedance, said branches being arranged to form a lattic network, said capacitor providing two variable capacitances one of which increases in value as the other is decreased and said capacitances being associated, respectively, with two of said impedancebranches which are adjacent to each other.
  • each of said capacitances is connected in shunt with its associated impedance branch.
  • a wave filter comprising four piezoelectric crystal impedances arranged to form a lattice network, said filter including two variable capacitances connected, respectively, in parallel with two of said impedances which are in adjacent branches or said lattice network and one of said capacitances increasing in value as the other is decreased.
  • a wave filter of the lattice type comprising two series'impedance branches and two diagonal impedance branches, each of said branches including a piezoelectric crystal impedance, said filter including a differential capacitor providing two variable capacitances one of which increases in value as the other is decreased, one 01 said capacitances being connected in parallel with one of said series branches and the other of said capacitances being connected in parallel with one of said diagonal branches.
  • a wave filter comprising two pairs of piezoelectric crystal impedances and a differential capacitor, said crystal impedances being connected to form a lattice network, said differen- 6.
  • a filter in accordance with claim 5 whichincludes variable capacitors connected in shunt at the ends of said lattice network.
  • a filter in accordance with claim 5' which includes inductors connected in series at the ends of said lattice network.
  • a filter in accordance with claim 5 which includes shunt capacitors and series inductors connected at the ends of said lattice network.
  • a wave filter comprising two pairs of terminals, four impedance branches and a differential capacitor, .each of said branches comprising a piezoelectric crystal impedance, said branches being connected between said terminals to form a lattice network, said capacitor comprising two fixed plates and a movable plate, said movable plate being connected to a terminal in one of said pairs and said fixed plates being connected, respectively, to the terminals in the other of said pair.

Landscapes

  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
US446479A 1942-06-10 1942-06-10 Wave filter Expired - Lifetime US2342875A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
NL134514D NL134514B (en, 2012) 1942-06-10
BE473973D BE473973A (en, 2012) 1942-06-10
NL83190D NL83190C (en, 2012) 1942-06-10
US446479A US2342875A (en) 1942-06-10 1942-06-10 Wave filter
CH265654D CH265654A (de) 1942-06-10 1947-05-28 Kristall-Wellenfilter.
FR948264D FR948264A (fr) 1942-06-10 1947-06-20 Filtre d'ondes
GB17026/47A GB624292A (en) 1942-06-10 1947-06-27 Improvements in wave filters

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US446479A US2342875A (en) 1942-06-10 1942-06-10 Wave filter

Publications (1)

Publication Number Publication Date
US2342875A true US2342875A (en) 1944-02-29

Family

ID=23772747

Family Applications (1)

Application Number Title Priority Date Filing Date
US446479A Expired - Lifetime US2342875A (en) 1942-06-10 1942-06-10 Wave filter

Country Status (6)

Country Link
US (1) US2342875A (en, 2012)
BE (1) BE473973A (en, 2012)
CH (1) CH265654A (en, 2012)
FR (1) FR948264A (en, 2012)
GB (1) GB624292A (en, 2012)
NL (2) NL83190C (en, 2012)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2452114A (en) * 1945-04-26 1948-10-26 Bell Telephone Labor Inc Balanced wave filter
US3051919A (en) * 1958-09-17 1962-08-28 Clevite Corp Filter-transformers
US5499002A (en) * 1994-04-28 1996-03-12 Kinsman; Robert G. Resonator filter utilizing cascaded impedance inverters

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2452114A (en) * 1945-04-26 1948-10-26 Bell Telephone Labor Inc Balanced wave filter
US3051919A (en) * 1958-09-17 1962-08-28 Clevite Corp Filter-transformers
US5499002A (en) * 1994-04-28 1996-03-12 Kinsman; Robert G. Resonator filter utilizing cascaded impedance inverters

Also Published As

Publication number Publication date
CH265654A (de) 1949-12-15
FR948264A (fr) 1949-07-27
GB624292A (en) 1949-06-01
NL83190C (en, 2012)
NL134514B (en, 2012)
BE473973A (en, 2012)

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