EP0844683A1 - Microstrip circuits - Google Patents

Microstrip circuits Download PDF

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Publication number
EP0844683A1
EP0844683A1 EP97203985A EP97203985A EP0844683A1 EP 0844683 A1 EP0844683 A1 EP 0844683A1 EP 97203985 A EP97203985 A EP 97203985A EP 97203985 A EP97203985 A EP 97203985A EP 0844683 A1 EP0844683 A1 EP 0844683A1
Authority
EP
European Patent Office
Prior art keywords
transmission line
diode
microstrip
microwave
microwave diode
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Withdrawn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
EP97203985A
Other languages
German (de)
French (fr)
Inventor
David Patrick
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.)
Matra Bae Dynamics UK Ltd
Original Assignee
Matra Bae Dynamics UK 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 Matra Bae Dynamics UK Ltd filed Critical Matra Bae Dynamics UK Ltd
Publication of EP0844683A1 publication Critical patent/EP0844683A1/en
Withdrawn legal-status Critical Current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
    • H01P1/24—Terminating devices

Definitions

  • This invention relates to microstrip circuits suitable for microwave applications and to matched loads therefor.
  • a number of microwave microstrip circuits require matched loads in order to function correctly; a hybrid microstrip ring coupler, for example.
  • a matched load is designed to terminate a transmission line and absorb all of the microwave energy, reflecting as little as possible.
  • One known method of providing a matched load is to apply a drop of absorbing material over the end of the line.
  • this could be a tapered piece of carbon-loaded epoxy resin.
  • This is applied in liquid form and then subsequently hardens to produce the required load.
  • the shape of the applied load is important for its performance and it becomes increasingly difficult to achieve a consistently good performance at higher microwave frequencies (millimetric for example). This results in very variable circuit performance which may not be acceptable.
  • the process of applying this type of load to a microstrip is labour intensive and difficult to automate.
  • a microstrip circuit includes a microstrip transmission line which is terminated by a microwave diode arranged to have substantially the same impedance as the transmission line.
  • the microwave diode may be a PIN, mixer or varactor diode, for example.
  • the microwave diode acts like a resistive termination, absorbing incident power.
  • any residual reflections from the diode can be cancelled out by incorporating a matching stub connected to the transmission line.
  • the microwave diode is used purely as a matched load and not for its normal function, e.g. detecting power.
  • microwave diode is attached to the microstrip transmission line automatically, using thermosonic bonding techniques. This has the advantage of giving more repeatable results.
  • Means may be provided for applying a bias current to the microwave diode.
  • the diode's microwave characteristics can be modified after attachment by varying the amplitude of the bias current.
  • performance can be optimised.
  • Varying the bias current will vary the impedance of the diode and hence its matching properties.
  • Figures 1 and 2 are schematic plan and side views respectively of a microstrip circuit in accordance with the invention.
  • a microstrip line 1 is mounted on an insulating substrate 2 (such as ptfe) which, on its reverse side, is provided with a copper ground plane 3.
  • the microstrip line 1 is terminated by a microwave PIN diode 4 whose anode is connected to the line 1 and whose cathode is connected to a conducting pad 5.
  • a bias current is supplied to the diode 4 by connecting a supply 6 thereto.
  • a matching stub 7 connected to the line 1 ensures that any residual reflections from the diode 4 are cancelled out.
  • the performance of the complete microwave circuit can be optimised by adjusting the diode bias current supply 6 whilst observing the relevant parameters on the appropriate test equipment (not shown).
  • the optimum overall circuit performance may not necessarily coincide with the optimum load performance ie the impedance values of the microstrip line and the diode not being exactly matched.
  • the reflections from the diode can be used to interact with other unwanted reflections in the circuit to benefit the overall performance.
  • the amplitude and phase of the diode reflections are not independently variable but this is not usually a disadvantage. However, by employing some form of electronically-controlled phase shifter, complete control of load performance should be achievable.
  • the electronic nature of the load matching process lends itself to automation of the optimisation process with computer controlled test equipment.

Abstract

A means of terminating a microstrip transmission line (1) comprises a microwave diode (4) employed as a matched load. The matching characteristics of the diode (4) can be optimised by varying a bias current from a supply (6). This method of optimising load performance lends itself to automation with computer controlled test equipment.

Description

This invention relates to microstrip circuits suitable for microwave applications and to matched loads therefor.
A number of microwave microstrip circuits require matched loads in order to function correctly; a hybrid microstrip ring coupler, for example. A matched load is designed to terminate a transmission line and absorb all of the microwave energy, reflecting as little as possible.
One known method of providing a matched load is to apply a drop of absorbing material over the end of the line. For example, this could be a tapered piece of carbon-loaded epoxy resin. This is applied in liquid form and then subsequently hardens to produce the required load. The shape of the applied load is important for its performance and it becomes increasingly difficult to achieve a consistently good performance at higher microwave frequencies (millimetric for example). This results in very variable circuit performance which may not be acceptable. Furthermore, the process of applying this type of load to a microstrip is labour intensive and difficult to automate.
According to this invention, a microstrip circuit includes a microstrip transmission line which is terminated by a microwave diode arranged to have substantially the same impedance as the transmission line.
The microwave diode may be a PIN, mixer or varactor diode, for example.
The microwave diode acts like a resistive termination, absorbing incident power.
Any residual reflections from the diode can be cancelled out by incorporating a matching stub connected to the transmission line.
The microwave diode is used purely as a matched load and not for its normal function, e.g. detecting power.
Preferably the microwave diode is attached to the microstrip transmission line automatically, using thermosonic bonding techniques. This has the advantage of giving more repeatable results.
Means may be provided for applying a bias current to the microwave diode.
The diode's microwave characteristics can be modified after attachment by varying the amplitude of the bias current. Thus by choosing the right bias current, performance can be optimised.
Varying the bias current will vary the impedance of the diode and hence its matching properties.
An embodiment of the invention will now be described, by way of example only, with reference to the drawings of which:
Figures 1 and 2 are schematic plan and side views respectively of a microstrip circuit in accordance with the invention.
With reference to Figures 1 and 2 a microstrip line 1 is mounted on an insulating substrate 2 (such as ptfe) which, on its reverse side, is provided with a copper ground plane 3.
The microstrip line 1 is terminated by a microwave PIN diode 4 whose anode is connected to the line 1 and whose cathode is connected to a conducting pad 5. A bias current is supplied to the diode 4 by connecting a supply 6 thereto.
A matching stub 7 connected to the line 1 ensures that any residual reflections from the diode 4 are cancelled out.
With the circuit of Figures 1 and 2 incorporated in a microwave circuit (not shown), such as a ring coupler or discriminator for example, the performance of the complete microwave circuit can be optimised by adjusting the diode bias current supply 6 whilst observing the relevant parameters on the appropriate test equipment (not shown).
The optimum overall circuit performance may not necessarily coincide with the optimum load performance ie the impedance values of the microstrip line and the diode not being exactly matched. The reflections from the diode can be used to interact with other unwanted reflections in the circuit to benefit the overall performance. The amplitude and phase of the diode reflections are not independently variable but this is not usually a disadvantage. However, by employing some form of electronically-controlled phase shifter, complete control of load performance should be achievable.
Advantageously, the electronic nature of the load matching process lends itself to automation of the optimisation process with computer controlled test equipment.

Claims (6)

  1. A microstrip circuit including a microstrip transmission line (1) characterised in that the transmission line (1) is terminated by a microwave diode (4) arranged to have substantially the same impedance value as the transmission line (1).
  2. A microstrip circuit as claimed in claim 1 in which the microwave diode (4) is attached to the microstrip transmission line (1) by means of thermosonic bonding techniques.
  3. A microstrip circuit as claimed in either preceding claim, further including means (6) for applying a bias current to the microwave diode (4) thereby varying the impedance of the microwave diode (4)
  4. A microstrip circuit according to any preceding claim and including a matching stub (7) connected to the transmission line (1) for cancelling out any reflections from the microwave diode (4).
  5. A microstrip circuit according to any preceding claim in which the transmission line (1) is mounted on an insulating substrate (2) which has a conducting ground plane (3) on its reverse side and in which an anode of the microwave diode (4) is connected to the transmission line (1) and a cathode of the microwave diode (4) is connected to a conducting pad mounted on the substrate (2).
  6. A method of providing an optimised matched load for a microstrip transmission line (1) by connecting a microwave diode (4) to an end thereof and by varying the amplitude of a bias current to the diode (4).
EP97203985A 1996-11-23 1997-11-21 Microstrip circuits Withdrawn EP0844683A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9624477.7A GB9624477D0 (en) 1996-11-23 1996-11-23 Microwave circuits
GB9624477 1996-11-23

Publications (1)

Publication Number Publication Date
EP0844683A1 true EP0844683A1 (en) 1998-05-27

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP97203985A Withdrawn EP0844683A1 (en) 1996-11-23 1997-11-21 Microstrip circuits

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EP (1) EP0844683A1 (en)
GB (1) GB9624477D0 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113109692A (en) * 2021-03-31 2021-07-13 中国电子科技集团公司第十三研究所 Microstrip circuit debugging method and adjusting module

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4301429A (en) * 1979-06-07 1981-11-17 Raytheon Company Microwave diode with high resistance layer
US4301432A (en) * 1980-08-11 1981-11-17 Motorola, Inc. Complex RF weighter
JPS5919406A (en) * 1982-07-22 1984-01-31 Mitsubishi Electric Corp Variable attenuator using reflecting type constant phase diode
US5298793A (en) * 1990-02-08 1994-03-29 Matsushita Electronics Corporation Semiconductor device including an electrode

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4301429A (en) * 1979-06-07 1981-11-17 Raytheon Company Microwave diode with high resistance layer
US4301432A (en) * 1980-08-11 1981-11-17 Motorola, Inc. Complex RF weighter
JPS5919406A (en) * 1982-07-22 1984-01-31 Mitsubishi Electric Corp Variable attenuator using reflecting type constant phase diode
US5298793A (en) * 1990-02-08 1994-03-29 Matsushita Electronics Corporation Semiconductor device including an electrode

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
M.C.R. CARVALHO ET AL.: "FLAT MICROWAVE RESPONSES OF DIRECTLY MODULATED LASER DIODES", 1986 IEEE-MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM-DIGEST, 2 June 1986 (1986-06-02) - 4 June 1986 (1986-06-04), BALTIMORE (US), pages 523 - 526, XP002056128 *
PATENT ABSTRACTS OF JAPAN vol. 8, no. 103 (E - 244)<1540> 15 May 1984 (1984-05-15) *
PEKET-MAY M ET AL: "FD-TD MODELING OF DIGITAL SIGNAL PROPAGATION IN 3-D CIRCUITS WITH PASSIVE AND ACTIVE LOADS", IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, vol. 42, no. 8, 1 August 1994 (1994-08-01), pages 1514 - 1523, XP000456911 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113109692A (en) * 2021-03-31 2021-07-13 中国电子科技集团公司第十三研究所 Microstrip circuit debugging method and adjusting module

Also Published As

Publication number Publication date
GB9624477D0 (en) 1997-01-15

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