WO2012164273A1 - Filtre à micro-ondes - Google Patents

Filtre à micro-ondes Download PDF

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Publication number
WO2012164273A1
WO2012164273A1 PCT/GB2012/051195 GB2012051195W WO2012164273A1 WO 2012164273 A1 WO2012164273 A1 WO 2012164273A1 GB 2012051195 W GB2012051195 W GB 2012051195W WO 2012164273 A1 WO2012164273 A1 WO 2012164273A1
Authority
WO
WIPO (PCT)
Prior art keywords
resonators
filter
microwave filter
microwave
resonator
Prior art date
Application number
PCT/GB2012/051195
Other languages
English (en)
Inventor
John David Rhodes
Original Assignee
Filtronic Wireless Ltd
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 claimed from US13/150,966 external-priority patent/US20120306596A1/en
Priority claimed from GBGB1109196.4A external-priority patent/GB201109196D0/en
Priority claimed from GBGB1111729.8A external-priority patent/GB201111729D0/en
Application filed by Filtronic Wireless Ltd filed Critical Filtronic Wireless Ltd
Publication of WO2012164273A1 publication Critical patent/WO2012164273A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/03—Frequency selective two-port networks comprising means for compensation of loss
    • 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
    • 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
    • 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
    • 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
    • H01P1/205—Comb or interdigital filters; Cascaded coaxial cavities
    • 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
    • H01P1/207—Hollow waveguide filters
    • H01P1/208—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure

Definitions

  • the present invention relates to a microwave filter. More particularly, but not exclusively, the present invention relates to a microwave filter comprising a plurality of single resonators and a frequency independent coupling connected in parallel between input and output ports, a subset of the resonators having Q factors which are sufficiently higher than that of the remaining resonators to achieve low loss across the entire passband.
  • each resonator couples loss into the system.
  • at least 25dB rejection has to be provided over a band in excess of several MHz whilst the loss at 0.5MHz into the passband has to be less than 0.5dB.
  • Qs of greater than 20,000 are required resulting in the necessity, at microwave frequencies, to use ceramic resonators for all of the cavities resulting in a physically large, heavy and expensive filter.
  • the filter according to the invention seeks to overcome the problems of the prior art.
  • the present invention provides a microwave filter for filtering a microwave signal, the microwave filter having at least one band edge at a band edge transition frequency, the filter comprising an input port; an output port; and, a plurality of single resonators connected in parallel between the input and output ports; the filter further comprising a frequency independent electrical coupling between input and output ports connected in parallel with the resonators; a subset of the resonators having Q values each of which are at least a factor of three higher than the Qs of each of the remaining resonators.
  • the microwave filter according to the invention requires only one high Q resonator per band edge to achieve low loss across the entire filter passband.
  • the number of resonators in the subset is equal to the number of band edges.
  • the Q values of the resonators in the subset are at least four times, more preferably five times that of the Qs of each of the remaining resonators.
  • the filter can have only one band edge.
  • the filter may consist of two resonators in parallel.
  • the filter may comprise at least three, preferably four resonators in parallel.
  • At least one resonator comprises a cavity resonator.
  • the filter may comprise at least one impendence inverter.
  • the filter may further comprise an electrical signal generator connected to the input port of the filter.
  • the input port can comprise a further resonator.
  • the output port can comprise a further resonator.
  • FIG. 2 shows a further known microwave filter
  • Figure 3 shows an embodiment of a filter according to the invention
  • Figure 4 shows a further embodiment of a filter according to the invention
  • Figure 5 shows a further embodiment of a filter according to the invention.
  • Figure 6 shows the transmission and reflection of a filter according to the invention
  • Figure 7 shows an equivalent circuit for a filter according to the invention.
  • Figure 8 shows a further embodiment of a filter according to the invention.
  • Shown in figure 1 is a known microwave filter 1.
  • the filter 1 comprises a plurality of resonators 2 connected together in series.
  • the resonators 2 have different resonant frequencies producing a composite filter having a passband.
  • Each resonator 2 couples loss into the system. Accordingly, to meet typical rejection requirements each resonator 2 must be of high Q. This results in a filter 1 which is expensive to manufacture and which may be large and heavy.
  • a partial solution to this problem requiring only one high Q cavity per band edge is known.
  • This solution comprises a reflection mode filter 3 connected to a circulator 4 as shown in figure 2.
  • the limitation of this arrangement is that a circulator 4 is required. This has limited isolation and introduces additional loss.
  • a microwave filter 5 for filtering a microwave signal according to the invention.
  • the filter 5 has a single band edge at a band edge transition frequency, so defining a passband.
  • the filter 5 is either a high pass or low pass filter 5.
  • the filter 5 comprises an input port 6 and an output port 7. Connected between the input port 6 and output port 7 in parallel is a plurality (in this case four) of single resonators 8. Also connected between the input port 6 and output port 7 in parallel with the resonators 8 is a frequency independent electrical coupling 9.
  • Each of the resonators 8 has a Q value.
  • the Q value of one of the resonators 8 has a Q value which is at least four times that of the Q values of each of the other resonators 8.
  • the microwave filter 5 according to the invention has low loss over the entire passband, even though only one of the resonators 8 is a 'high' Q resonator 8, relative to the other resonators 8.
  • FIG 4 Shown in figure 4 is a further embodiment of a microwave filter 5 according to the invention.
  • This embodiment comprises a filter 5 having two band edges defining a passband therebetween.
  • the filter 5 comprises four resonators 8 connected in parallel between the input and output ports 6,7.
  • a frequency independent coupling 9 is connected in parallel with the resonators 8.
  • two of the resonators 8 are 'high' Q resonators 8, each of the resonators 8 having a Q value which is at least a factor of four larger than the Q values of the remaining resonators 8.
  • FIG. 5 shows a further embodiment of a microwave filter 5 according to the invention.
  • the filter 5 has one band edge at a band edge transition frequency.
  • the filter comprises two resonators 8 connected in parallel between input and output ports 6,7.
  • a frequency independent coupling 9 also extends between the ports 6,7 in parallel with the resonators 8.
  • one of the resonators 8 has a Q value which is a factor of five higher than that of the other resonator 8.
  • a subset of the resonators 8 of filters 5 according to the invention have Q values which are each a factor of at least three larger than the Q values of the remaining resonators 8. More preferably the Q values are a factor of four, more preferably a factor of five larger than the Q values of the remaining resonators 8. It is preferred that the number of resonators 8 in this subset is equal to the number of band edges as shown in the examples above.
  • the filter 5 is a lossless second degree filter 5 with a finite passband and infinite stopband designed with 10dB return loss and 10dB reflection.
  • the ration of the bandwidths for the two resonators 8 is close to 8:1.
  • the network can be realised as a symmetrical structure and can be decomposed into even and odd mode admittances Y e (p) and Y 0 (p)
  • the low Q resonator can have a Q factor which is (V2 - l) 2 less than the high Q resonator.
  • the high Q resonator has Q value which is a factor of the order (72 4- l) 2 higher than the low Q resonator then the loss of the filter is substantially determined by that of the high Q filter only.
  • the even and odd mode admittances can always be formed and expressed as partial fraction expansions of the form

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)

Abstract

L'invention concerne un filtre à micro-ondes destiné à filtrer un signal de micro-ondes, le filtre à micro-ondes possédant au moins une limite de bande à une fréquence de transition de limite de bande, le filtre comportant un port d'entrée ; un port de sortie ; et une pluralité de résonateurs individuels connectés en parallèle entre les ports d'entrée et de sortie ; le filtre comprenant en outre un couplage électrique indépendant de la fréquence entre des ports d'entrée et de sortie connectés en parallèle avec les résonateurs ; un sous-ensemble des résonateurs possédant des valeurs Q qui sont chacune supérieures d'au moins un facteur trois par rapport aux valeurs Q de chacun des résonateurs restants.
PCT/GB2012/051195 2011-06-01 2012-05-25 Filtre à micro-ondes WO2012164273A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
GB1109196.4 2011-06-01
US13/150,966 US20120306596A1 (en) 2011-06-01 2011-06-01 Microwave Filter
GBGB1109196.4A GB201109196D0 (en) 2011-06-01 2011-06-01 A microwave filter
US13/150,966 2011-06-01
GB1111729.8 2011-07-08
GBGB1111729.8A GB201111729D0 (en) 2011-07-08 2011-07-08 A microwavew filter

Publications (1)

Publication Number Publication Date
WO2012164273A1 true WO2012164273A1 (fr) 2012-12-06

Family

ID=46456928

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2012/051195 WO2012164273A1 (fr) 2011-06-01 2012-05-25 Filtre à micro-ondes

Country Status (2)

Country Link
GB (1) GB2491460B (fr)
WO (1) WO2012164273A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020118081A1 (en) * 2000-11-14 2002-08-29 Xiao-Peng Liang Hybrid resonator microstrip line filters
US6525630B1 (en) * 1999-11-04 2003-02-25 Paratek Microwave, Inc. Microstrip tunable filters tuned by dielectric varactors
US6532377B1 (en) * 1999-09-29 2003-03-11 Kabushiki Kaisha Toshiba Planar filter and filter system using a magnetic tuning member to provide permittivity adjustment

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2682037A (en) * 1950-09-08 1954-06-22 Bell Telephone Labor Inc Equalizer
JPH0812961B2 (ja) * 1989-05-02 1996-02-07 株式会社村田製作所 並列多段型帯域通過フィルタ
US5760667A (en) * 1995-07-12 1998-06-02 Hughes Aircraft Co. Non-uniform Q self amplitude equalized bandpass filter
JP4303272B2 (ja) * 2006-09-15 2009-07-29 株式会社東芝 フィルタ回路
GB201000228D0 (en) * 2010-01-06 2010-02-24 Isotek Electronics Ltd An electrical filter

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6532377B1 (en) * 1999-09-29 2003-03-11 Kabushiki Kaisha Toshiba Planar filter and filter system using a magnetic tuning member to provide permittivity adjustment
US6525630B1 (en) * 1999-11-04 2003-02-25 Paratek Microwave, Inc. Microstrip tunable filters tuned by dielectric varactors
US20020118081A1 (en) * 2000-11-14 2002-08-29 Xiao-Peng Liang Hybrid resonator microstrip line filters

Also Published As

Publication number Publication date
GB2491460A (en) 2012-12-05
GB2491460B (en) 2017-09-06
GB201209215D0 (en) 2012-07-04

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