EP0208441A2 - Schaltbares Hochfrequenzdämpfungsglied - Google Patents

Schaltbares Hochfrequenzdämpfungsglied Download PDF

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Publication number
EP0208441A2
EP0208441A2 EP86304728A EP86304728A EP0208441A2 EP 0208441 A2 EP0208441 A2 EP 0208441A2 EP 86304728 A EP86304728 A EP 86304728A EP 86304728 A EP86304728 A EP 86304728A EP 0208441 A2 EP0208441 A2 EP 0208441A2
Authority
EP
European Patent Office
Prior art keywords
attenuator
network
input
substrate
output connections
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Withdrawn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
EP86304728A
Other languages
English (en)
French (fr)
Other versions
EP0208441A3 (de
Inventor
Robert Owen Bristow
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.)
Pascall Electronics Ltd
Original Assignee
Viavi Solutions UK Ltd
Pascall Electronics 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
Application filed by Viavi Solutions UK Ltd, Pascall Electronics Ltd filed Critical Viavi Solutions UK Ltd
Publication of EP0208441A2 publication Critical patent/EP0208441A2/de
Publication of EP0208441A3 publication Critical patent/EP0208441A3/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/22—Attenuating devices
    • H01P1/227—Strip line attenuators

Definitions

  • This invention relates to a high - frequency switched attenuator.
  • An object of the invention is to provide a switched attenuator for use at high frequencies, for example in a transmission line, for the purpose of introducing selectively, under control of a switch, a predetermined degree of attenuation.
  • Attenuators for use at high frequencies and for connection to coaxial transmission lines. Such attenuators are used, for example, in instrument calibration.
  • One known such attenuator is described in U.S. Patent Specification 4330765 (Patukonis) and consists of a number of attenuator stages carried on a common substrate and controlled by individual relay switches with associated change-over contacts. When the associated relay is in one state an input signal is routed through an associated attenuation network to impart a predetermined degree of attenuation to the signal, while with the relay in its other state the signal by-passes the attenuation network. By selectively energising the relays it is possible to cascade attenuator stages with different attenuation factors to provide a variety of overall attenuation values.
  • the problem associated with high-frequency attenuators is that of maintaining an accurate predetermined attenuation over a wide frequency range.
  • the switch contacts associated with each attenuation stage define between them an inherent capacitance which, in the higher attenuation stages, is a significant source of error.
  • the switch capacitance presents a secondary path by-passing the associated attenuator network to an extent which increases as the frequency of the signal increases.
  • the problem is aggravated where there is a difference in the electrical lengths of the primary path through the attenuator network and the secondary path presented by the switch capacitance: a path length difference of only a few millimetres can cause a dip in the frequency response of the attenuator at the upper end of the frequency band for which the attenuator is designed.
  • a switched attenuator with a path length in the attenuation network which can be adjusted, for example, by selective removal of a conductive track on an insulating substrate. Adjustment of the path length in this way has the disadvantage that it is irreversible. Moreover, the method is capable only of correcting for a steady increase of attenuation with increase in frequency, and is not ideally suited to compensating for a dip in the frequency response.
  • the present invention aims to provide a high-frequency switched attenuator with a readily adjustable means for compensating for frequency-dependent parasitic effects introduced by the switch.
  • a high-frequency switched attenuator comprising input and output connections, a signal by-pass path, an attenuator network, and a relay switch having a first condition in which the input and output connections are interconnected by the by-pass path and a second condition in which the input and output connections are interconnected through the attenuator network, wherein the attenuator farther includes a compensation network connected betweem the input and output connections and comprising an imductive component and a variable capacitive component.
  • the attenuator may be embodied with others as a part of a programmable Step attenuator unit.
  • the attenuator network is preferably formed on a substrate of dielectric material and is constituted by layers or coatings selectively deposited on the substrate.
  • the compensation network may be carried on a substrate of dielectric material.
  • the substrate carrying the compensation network is physically separate and distinct from the susbtrate carrying the attenuation network. This enables different compensation networks to be fitted to and connected electrically to a given attenuator network.
  • the variable capacitance preferably includes a rotary trimmer capacitor.
  • the capacitance preferably also includes fixed capacitive components formed, for example, by layers deposited on opposite faces of the substrate carrying the compensation network.
  • the inductive component of the attenuator network may similarly comprise inductive strip elements carried on the substrate of the compensation network.
  • two inductive strip elements may be carried on the same substrate as the capacitance and may connect the latter to the respective input and output connections.
  • the variable capacitance may be connected electrically in series with the two inductive strip elements, while in another embodiment the variable capacitance may form part of an earth connection between the two inductive strip elements.
  • the inductive component of the compensation network may be constituted by the spurious self-inductance of the trimmer capacitor. This may be the case, for example, where the compensation network is associated with an attenuator network having a low attenuation factor.
  • the switched attenuator of the present invention and its associated compensation network constitutes an attenuator pad or cell which may in turn form a modular component of an a programmable step attenuator unit.
  • an attenuator unit in accordance with another aspect of the invention may comprise a number of high frequency switched attenuator pads or cells, each individually compensated. This renders the task of fault rectification much simpler and more economical, since individual attenuator pads or cells can be replaced as required, in contrast to known card attenuators in which a number of attenuator cells are carried on a single substrate.
  • an attenuator network is connected to input and output connectors 1, 2 through respective changeover switches 3, 4 associated with a relay 5.
  • the electrical signal path between the switches 3, 4 and the attenuator network is represented by resistive connector elements 6, 7.
  • the relay 5 has a first condition in which the switches 3, 4 (shown by broken lines) connect the input and output connectors 1, 2 to a signal shunt or by-pass path 8 and a second condition in which the switches 3, 4, shown by full lines, connect the input and output connectors 1, 2 to the attenuator network A.
  • the leakage capacitance C s across the relay switch contacts when the switches 3, 4 are in their second condition becomes a major source of error, particularly when the attenuator network A has a high attenuation factor.
  • the leakage capacitance C s constitutes a secondary path by-passing the attenuator network A.
  • the compensating inducator Lg would be of the order of 0.25 nanoHenry.
  • the inductor Lg would normally be formed by a short conductive track on an insulating substrate, the inductance value being adjusted by trimming the cross-section of the track. This method of compensation is specific to a particular critical path length such that the dip in the frequency response is placed above the upper end of the working frequency range of the attenuator.
  • the present invention provides a compensation network, identified LC in Figure 1, which is connected across the attenuator network A.
  • the equivalent electrical circuit shown in Figure 1 can be analysed using a computer program.
  • the relay 5 can be represented electrically as an ideal switch of zero electrical length.
  • the connector elements 6, 7 are each taken as equivalent to a 50 ohm transmission line, and the attenuator circuit A is assumed to be a perfect 30dB attenuator section with a 50 ohm terminating impedance. Using this model the different methods of compensation of the attenuator can be compared. Four different cases are considered, the electrical length of the equivalent resistive connector elements 6, 7 being identified "T" in each case:
  • L and C in the compensation network would in practice be about 40nH and 0.05pF respectively for a 30dB attenuator section, and about 5nH or less and 0.3pF respectively for a 20dB attenuator section.
  • FIG 3 A practical embodiment of a high-frequency attenuator according to the invention is illustrated in Figure 3, and its electrical equivalent circuit in Figure 2.
  • the attenuator forms a single section or pad of a multiple-section step attenuator unit.
  • the attenuator network A is formed by resistive elements 9 deposited on a substrate 10 of high dielectric constant, preferably alumina.
  • the input and output connectors 1 and 2 comprise respective microstrip lines deposited on the substrate 10 and connectable to respective microstrip lines constituting the connector elements 6 and 7 through the respective relay switches 3 and 4 when the associated relay 5 is in its second condition.
  • the relay 5 is attached to the substrate 10 on the side opposite the connectors 1, 2, 6 and 7.
  • the by-pass path 8 to which the switches 3 and 4 are connected in the first condition of the relay 5 consists of a further microstrip line section deposited on the substrate 10.
  • the input and output signal path lengths of the attenuator must be kept as short as possible.
  • the path length can be longer (typically 14 mm for a 30dB attenuator section) than that necessary (e.g. 5.06mm) if the critical length compensation technique is used.
  • the LC compensation network comprises inductive and capacitive components carried on a substrate 11, also of alumina, separate from and mounted on the substrate 10.
  • the compensation network is connected across the attenuator network by connector pins 12, 13 which make contact with the connector elements 6, 7 respectively.
  • the LC compensation network comprises two thin microstrip tracks L 1 , L 2 on the underside of the substrate 11 ( Figure 6) connected in series with respective fixed parallel plate capacitive elements C 1 , C 2 formed by respective pairs of coatings 14, 15 and 16, 17 deposited on the opposite faces of the substrate 11.
  • a variable capacitor C 3 interconnects the two fixed capacitances C 1 , C 2 .
  • the variable capacitor C 3 comprises a rotary trimmer capacitor carried on the opposite face of the substrate 11 from the inductive tracks L 1 , L 2 and connected electrically to the conductive coatings 14, 16 of the fixed capacitances.
  • the trimmer capacitor C 3 allows adjustment of the capacitive component over a small tuning range.
  • the inductive component L 1 , L 2 of the compensation network is nominally about 40nH while the capacitive component C 1 , C 2 , C 3 , is nominally 0.05pF.
  • the compensation network of Figures 8-11 may be used in which the variable capacitor C 3 forms part of a ground connection between the two fixed capacitances C 1 , C 2 .
  • the trimmer capacitor C 3 introduces a variable capacitance between the two fixed capacitances C 1 ; C 2 , and the addition of the capacitance to ground is offset by reducing the series inductive components L 1 . L 2 .
  • the compensation networks shown in Figures 4 to 7 and 8-11 are intended for use with attenuator sections of about 30dB attenuation.
  • attenuator sections of about 30dB attenuation.
  • attenuation steps of about 20dB value
  • a trimmer capacitor can be used alone with no additional inductive components, because the required inductance is of the same order as the trimmer capacitor's spurious self-inductance.

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  • Attenuators (AREA)
EP86304728A 1985-07-06 1986-06-19 Schaltbares Hochfrequenzdämpfungsglied Withdrawn EP0208441A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB858517180A GB8517180D0 (en) 1985-07-06 1985-07-06 High frequency switched attenuator
GB8517180 1985-07-06

Publications (2)

Publication Number Publication Date
EP0208441A2 true EP0208441A2 (de) 1987-01-14
EP0208441A3 EP0208441A3 (de) 1988-08-03

Family

ID=10581918

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86304728A Withdrawn EP0208441A3 (de) 1985-07-06 1986-06-19 Schaltbares Hochfrequenzdämpfungsglied

Country Status (3)

Country Link
EP (1) EP0208441A3 (de)
DE (1) DE208441T1 (de)
GB (1) GB8517180D0 (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1043593A1 (de) * 1999-04-09 2000-10-11 Agilent Technologies Inc Dioden-Mikrowellenleistungssensor mit geschaltetem Dämpfungsglied
JP2002525951A (ja) * 1998-09-22 2002-08-13 クゥアルコム・インコーポレイテッド 高効率スイッチド利得パワー増幅器
WO2005002072A1 (de) * 2003-06-27 2005-01-06 Rohde & Schwarz Gmbh & Co. Kg Eichleitungs-anordnung
EP1798856A1 (de) * 1998-09-22 2007-06-20 QUALCOMM Incorporated Leistungsverstärker mit bypass-pfad
CN102053172A (zh) * 2009-11-10 2011-05-11 北京普源精电科技有限公司 一种高阻宽带衰减电路及使用该电路的示波器
CN102646669A (zh) * 2011-02-16 2012-08-22 台湾积体电路制造股份有限公司 利用调谐电感器的电容式临近通信
WO2012146952A1 (en) 2011-04-29 2012-11-01 Terra, Uab Radio-frequency circuit assembly

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3449697A (en) * 1967-10-19 1969-06-10 Ohmega Lab Attenuator wherein shunt capacitive loading cancels series capacitive signal leak at higher frequencies
US3900711A (en) * 1973-05-17 1975-08-19 Tektronix Inc Electrical contactor assembly for high frequency applications
US4330765A (en) * 1980-02-26 1982-05-18 Weinschel Engineering Co., Inc. Switchable microwave step attenuator with compensation for linear operation over wide frequency range

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3449697A (en) * 1967-10-19 1969-06-10 Ohmega Lab Attenuator wherein shunt capacitive loading cancels series capacitive signal leak at higher frequencies
US3900711A (en) * 1973-05-17 1975-08-19 Tektronix Inc Electrical contactor assembly for high frequency applications
US4330765A (en) * 1980-02-26 1982-05-18 Weinschel Engineering Co., Inc. Switchable microwave step attenuator with compensation for linear operation over wide frequency range

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002525951A (ja) * 1998-09-22 2002-08-13 クゥアルコム・インコーポレイテッド 高効率スイッチド利得パワー増幅器
EP1798856A1 (de) * 1998-09-22 2007-06-20 QUALCOMM Incorporated Leistungsverstärker mit bypass-pfad
EP1043593A1 (de) * 1999-04-09 2000-10-11 Agilent Technologies Inc Dioden-Mikrowellenleistungssensor mit geschaltetem Dämpfungsglied
WO2005002072A1 (de) * 2003-06-27 2005-01-06 Rohde & Schwarz Gmbh & Co. Kg Eichleitungs-anordnung
US7457593B2 (en) 2003-06-27 2008-11-25 Rhode & Schwarz Gmbh & Co. Kg Attenuator system
CN102053172A (zh) * 2009-11-10 2011-05-11 北京普源精电科技有限公司 一种高阻宽带衰减电路及使用该电路的示波器
CN102646669A (zh) * 2011-02-16 2012-08-22 台湾积体电路制造股份有限公司 利用调谐电感器的电容式临近通信
CN102646669B (zh) * 2011-02-16 2016-05-04 台湾积体电路制造股份有限公司 利用调谐电感器的电容式临近通信
WO2012146952A1 (en) 2011-04-29 2012-11-01 Terra, Uab Radio-frequency circuit assembly

Also Published As

Publication number Publication date
DE208441T1 (de) 1987-05-21
GB8517180D0 (en) 1985-08-14
EP0208441A3 (de) 1988-08-03

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