US3346824A - Microwave switch - Google Patents

Microwave switch Download PDF

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Publication number
US3346824A
US3346824A US483251A US48325165A US3346824A US 3346824 A US3346824 A US 3346824A US 483251 A US483251 A US 483251A US 48325165 A US48325165 A US 48325165A US 3346824 A US3346824 A US 3346824A
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US
United States
Prior art keywords
switch
diode
waveguide
loop
impedance
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
US483251A
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English (en)
Inventor
Jr William C Jakes
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
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US483251A priority Critical patent/US3346824A/en
Priority to GB33944/66A priority patent/GB1148193A/en
Priority to FR71776A priority patent/FR1488577A/fr
Priority to DE19661541723 priority patent/DE1541723B2/de
Priority to NL6611318A priority patent/NL6611318A/xx
Application granted granted Critical
Publication of US3346824A publication Critical patent/US3346824A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/03—Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
    • G01S7/034—Duplexers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/10—Auxiliary devices for switching or interrupting
    • H01P1/15—Auxiliary devices for switching or interrupting by semiconductor devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/74—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of diodes

Definitions

  • a high power microwave -switch having external ON-OFF control.
  • the switch consists of a plurality of sections of diode switching elements coupled to a waveguide through a resonant loop.
  • the diode elements are ixed an odd number of 1A wevelengths from the loop in a transmission line having a short circuited stub which antiresonates with the diode impedance.
  • This invention relates to microwave frequency switching devices and more particularly to externally controlled high power microwave switches having an adjustable attenuation.
  • a switching element to decouple one portion of the circuit from another during a specied interval.
  • a switching element to decouple one portion of the circuit from another during a specied interval.
  • a transmit-receive or so-called TR switch is inserted in the receiver channel near the point of juncture of the common transmit and receive paths.
  • TR switch is inserted in the receiver channel near the point of juncture of the common transmit and receive paths.
  • an antitransmit-receive or ATR device inserted in the transmitter path near the junction point.
  • microwave switches including those functioning as TR and ATR switches exist in the art.
  • Some such switches commonly found in the art operate through the use of some breakdown means such as a gaseous atmosphere which ionizes a resonant cavity during the transmission of a high power pulse.
  • Others have various other breakdown means included within a cavity or have a specially structured cavity which breaks down upon receipt of a high energy pulse to cause a reliection of transmitted energy and thus an attenuation of power in the direction of transmission.
  • a common problem occurring in prior art switches lies in the diiculty of constructing a device which has both the capability of passing high power "with a minimum of switching loss and the ability lto introduce a high attenuation in the transmission path when the switch is OFF. While some switches provide a high attenuation they do not etliciently pass high power energy when in the OFF condition.
  • many of the prior art switches are constructed in a manner that would require for installation special and extensive modification of existing waveguide structures.
  • many of the existing switches have no provision for externally controlling the switching action and no ability to vary the attenuation introduced.
  • a switch consisting of a diode switching element externally coupled to a waveguide transmission path through a resonant loop.
  • a diode switching element externally coupled to a waveguide transmission path through a resonant loop.
  • 'Ihe coupling between the diode switch and the terminals of the loop is external to the waveguide and consists of a transmission line having a length sufficient to present the diode impedance maximum and minimum at the loop terminals.
  • an adjustable tuning stub providing an impedance which antiresonates with the backbiased diode impedance.
  • the bias on the diode switching element is controlled by a bipolar control voltage which acts to either back-bias or forward-bias the diode switch to obtain, respectively, a very high impedance or a very low impedance.
  • the diode impedance appears transformed at the loop terminals either as an approximate short or as an approximate open circuit by virtue of the transmission line interconnecting the loop with the diode switching elements.
  • a very high impedance loop termination, or open circuit permits the transmission of energy within the waveguide (dened as the ON condition for the switch), while a very low impedance, or short, at the loop terminals causes a reection of transmitted energy and consequently an attenuation (defined as the switch OFF condition).
  • the magnitude of attenuation can be controlled by adjusting the angle the loop plane makes with a reference plane in the waveguide.
  • a plurality of such switches can be arranged consecutively along the length of the waveguide transmission line so that mutual coupling exists between adjacent resonant loops. It the loops are separated by an ascertainable optimum distance, the total attenuation introduced by the composite group switches will exceed the attenuation introduced by summing the contribution of each switch. Furthermore, the power capabilities of the composite switch can be increased by increasing the number of individual switch sections.
  • FIG. 1 is a schematic representation of a single switch section
  • FIG. 2 is an equivalent circuit of one switch section coupled to a waveguide
  • FIGS. 3 and 3A are cross sectional views of a complete switch showing a number of such switch sections.
  • FIG. 4 is an equivalent circuit of a composite switch having a number of switch sections coupled to the waveguide.
  • the schematic diagram of a single switch section shown in FIG. 1 includes a planar loop conductor 1 having a circumferential length of one wavele-ngth measured in free space at the transmission frequency connected by means of a coaxial line having outer conductor 2 and inner conductor 3 to a strip line of matching impedance having ground planes 5 and 5 and center conductor 4.
  • the ground planes 5 and 5 are both connected to the outer grounded conductor 2 of the coaxial line and the inner strip line conductor 4 is connected to the center conductor 3 of the coaxial line.
  • Located within the strip line is a diode switch consisting of a pair of diodes 6 and 7 brought out from the center strip line conductor 4 through opposite ground planes 5 and 5 to voltage control terminals 14 and 15 decoupled from the transmission line.
  • Each decoupling network consists of a low pass LC lter (such as choke coil 10 and capacitor 11) connected between a terminal and its respective diode.
  • a D.C. control voltage source 19 is connected to terminals 14 and 15 to either forward-bias or back-bias diodes 6 and 7.
  • a D.C. control voltage is applied to bias diode 6 over a circuit path which includes source 19, terminal 14, choke coil 10, diode 6, conductors 4 and 3,
  • a similar circuit can be traced for the bias voltage applied to diode- 7.
  • a coaxial line having outer conductor 16 and inner conductor 17 and an adjustable shorted tuning stub is connected to the strip line with conductors 5 and 5' connected to outer conductor 16 and conductor 4 connected to conductor 17
  • the position of the adjustable short 18 is adjusted so that the reactive impedance presented by the line on theI stub side of the diodes antiresonates with the back-biased reactive impedance of each diode to provide a very high resistive impedance for this condition.
  • Coupling of the switch to a waveguide transmission line is accomplished by inserting only the loop 1 into the interior of the waveguide. All other portions of the switch section including the control source may be located outside of the waveguide.
  • the strip line section of the switch is shown for convenience only and may be replaced by a coaxial line having similar electrical properties.
  • an adjustable shorting stub to antiresonate with the diode back impedance
  • an adjustable open stub may be employed with identical results. Because of considerations to be discussed below, the total length of transmission line between the diode switching elements 6 and 7 and the loop 1 is selected to be three quarters of a wavelength of the transmission signal measured in the coaxial line.
  • the inverse of the -diode impedance is presented at the loop terminals so that when the diodes are forward-biased, a very high impedance appears at the loop terminals and when the diodes are back-biased a very low impedance or a short appears at the loop terminals. Since the planar loop is inserted in the waveguide transmission line the impedance existing at its terminals affects the transmission of energy. The high impedance appearing at its terminals causes the loop to appear as an open circuit to produce virtually no effect on energy transmitted within the guide. On the other hand, a backbiased diode switch produces a short circuit at the loop terminals which in turn produces a reflection of transmitted energy within the waveguide to effectively attenuate the transmitted signal.
  • An odd number of quarter wavelengths is generally desired for the length of transmission line between the loop terminals and diode switch elements so that the diodes will be forward-biased when the switch is in the condition permitting transmission.
  • An even number of quarter wavelengths could theoretically be used instead, but this would curtail the power handling capabilities of the switch since the diodes would have to be back-biased during the time the switch permitted unattenuated transmission and would, therefore, have to withstand high voltages without breaking down.
  • a three-quarter wavelength line was selected rather than a quarter wavelength line in order to provide a line having a dimension at the frequency of operation which permitted easy construction and assembly.
  • FIG. 2 An equivalent circuit for the switch section shown in FIG. l is disclosed in FIG. 2 wherein the line between terminals 21-22 and 23-24 represents the waveguide section in which the switch is inserted.
  • the energy to be transmitted is represented as coming from source 37 having an output impedance 35 equal to the characteristic impedance Z0 of the line.
  • the line is terminated in its characteristic impedance Z0 as represented by resistor 36.
  • the switch may be represented as being coupled to the waveguide dominant mode by an ideal transformer having a primary to secondary turns ratio of 1:a.
  • the inductive element L and capacitive element C connected to the secondary of the transformer represent an equivalent impedance of the resonant loop 1 and have values which are defined by the relationship l LCTTZ 1)
  • Resistor Rd represents the effective diode back resistance including circuit losses and is shown connected to the elements representing the equivalent of the resonant loop by means of a transmission line having terminals 31-32 and 33-34. This transmission line has a length equal to an odd number of quarter wavelengths and more particularly three quarters of a wavele-ngth.
  • FIGS. 3 and 3A wherein a length of waveguide transmission line is shown in cross-sectional front and side views, it may be seen that the resonant loop is planar, and in the embodiment shown, makes an angle 0 with a plane parallel to a broad wall of the waveguide (which broad wall plane is also parallel to the plane of the magnetic field propagating within the waveguide).
  • An expre-ssion for the turns ratio ⁇ a of the ideal transformer 30 shown in FIG. 2 may be obtained as a function of this angle 6. This expression is as follows:
  • Equations 5 and 2 are plotted, it is found that both the loss L1 and the turns ratio a are monotonically increasing functions of 9.
  • a number of switches identical with that shown in FIG. l may, in accordance with a feature of the invention, be inserted in a waveguide to provide a composite switch having enhanced attenuation capabilities and a greater power handling capacity.
  • four switches are arranged consecutively along the length of a waveguide 38 so that the planar loop of each switch section is inserted through a narrow wall of the waveguide rat an angle 0 with the broad wall.
  • the spacing between each switch is made to be an odd number of quarter wavelengths so that the impedance presented to a given switch by those adjacent is transformed to a high value, thereby increasing the effectiveness of the switching action in la fashion obvious to those versed in the art.
  • the uniform displacement between adjacent switches is made equal to three-quarters of the wavelength measured within the waveguide and the planar loops ⁇ make alternately positive and negative angles 0 with a plane parallel to the broad wall.
  • An equivalent circuit representation of the composite switch is shown in FIG. 4 wherein the wavegiude transmission line is represented by its lumped parameter equivalent of series inductors and shunt capacitors between terminals 60-61 and 62-63. The line is terminated at both the source and 4load ends by the characteristic impedance Z0 of the transmission line. Coupled to the waveguide line at regular intervals is the switch as represented by the equivalent circuit of FIG. 2 as an ideal transformer having turns ratio 12a feeding the effective diode back resistance RD in series with the lumped capacitive and inductive elements representing the resonant loop. A mutual inductance between adjacent loops is represented by the quantity M. Using conven.
  • the loss of a composite switch having la multiplicity of sections may be calculated.
  • the loss relationship is as follows:
  • the normalized mutual reactance is defined as the voltage E2 induced in one switch section loop by a current I0 flowing in an adjacent switch section loop and normalized as shown.
  • the mutual induct-ance may be further defined qualitatively as resulting from the coupling of evanescent or higher order nontransmitted modes existing beyond cutoff.
  • the properties of a multisection switch may be examined through an analysis of a three-section switch described by Equation 6 Iand other ⁇ supporting equations. If it is assumed all loops are at the same angle 0 and that the loops are spaced far enough apart so that the mutual reactance is negligible, 1(0) as defined by Equation 9 is set to zero in Equation 6 land a monotonically increasing loss function results. If the loops are yall maintained at the same angle 0 and the spacing between loops is made three-quarters of a wavelength so that mutual reactance between adjacent loops exists, a similar monotonically increasing loss function results.
  • the switch elements openated satisfactorily 1and variations in diode parameters were permissibly wide. It is to be noted that the power capability of the switch may be increased by adding addition-al switch sections. Furthermore, an increase in the number of switch sections permits a lighter coupling of each switch to the waveguide (decreasing the valve of a(0)) while simultaneously maintaining a large attenuation by virtue of the mutual coupling effect. Because a lighter coupling is possible, burn-out of the forward-biased diodes may be prevented. While the switch sections are shown coupled through a narrow wall to the electric field in the waveguide, alternative coupling arrangements may of course be employed.
  • a switch for insertion in a waveguide comprising a plurality of sections each having an open-circuited resonant loop conductor mutually coupled within said Waveguide to loops from adjacent sections and means for shorting the ends of said loop to effect an attenuation of energy transmitted through said waveguide including a diode element, a control voltage source connected to said diode element for selectively biasing said diode and a transmission line interconnecting said diode element with said loop ends having sufficient length to transform the impedance of said diode for a selected bias to a short at said loop ends.
  • a microwave frequency switch for insertion in a waveguide comprising a first section having a resonant planar loop with open-circuited ends disposed within said waveguide, control means for actuating said switch to attenuation energy propagated through said waveguide including a diode switch having a forward and Ia reverse bias impedance, a line adjusted to transform said diode impedance to its inverse interconnecting said loop ends with said diode and a source for selectively Abiasing said diode, and a plurality of similar sections each having its resonant loop mutually coupled within said waveguide to adjacent loops.
  • a microwave frequency switch in accordance with claim 3 further including means for varying the magnitude of said angle to provide a continuously adjustable quantum of attenuation.
  • a microwave frequency switch comprising a plurality of switch sections each having a resonant planar loop with open-circuited ends disposed within said waveguide, means for controlling the attenuation of energy transmitted through said waveguide including a diode switching element having a forward and a reverse bias impedance, tunable means connected to said diode element for antiresonating with said reverse diode impedance, a line of sufficient length to transform said diode impedance to its inverse interconnecting said loop ends with said diode element and means for varying the angle said planar loop makes with a wall of said waveguide to adjust the attenuation introduced, said sections disposed with a distance between loops fixed so that the coupling between adjacent loops by means of the dominant field mode within the waveguide is equal and opposite to coupling between adjacent loops due to evanescent modes in said waveguide.
  • a microwave frequency switch for insertion in a waveguide comprising a first switch section having a resonant planar loop with open-circuited ends disposed within said waveguide, means external to said waveguide for controlling the attenuation of energy transmitted through said waveguide including a diode switching element having a forward and a reverse bias impedance, a first transmission line having an adjustable shorting stub connected to said diode to antiresonate with the reactive component of said reverse diode impedance, a second transmission line having a length equal to an odd number of quarter wavelengths measured within said line interconnecting said loop ends with said diode element, means for selectively biasing said diode element to said forward impedance to permit passage of energy propagating in said waveguide and to said reverse impedance to attenuate said energy and means for varying the angle said planar loop makes with a plane of magnetic field lines of a wave propagating in said waveguide to adjust the quantum of attenuation introduced, and a plurality of other substantially identical switch sections disposed longitudinal
  • a microwave frequency switch in accordance with claim 8 wherein said strip line contains provision for permitting external connection to said diode switching element, said diode switching element comprises a pair of diodes connected from the strip conductor of said strip line to said biasing means and wherein decoupling iilter means are connected between said biasing means and said diode element.
  • a switch comprising a resonant conductive loop with open ends disposed within said waveguide, means for sharply decreasing the impedance existing at said loop ends to attenuate energy transmitted through said waveguide including a diode switching element having a forward and a reverse bias impedance, a control voltage connected to said diode to selectively bias said diode and a transmission line interconnecting said diode switch with said loop ends having a suiicient length to transform the impedance of said diode for a selected bias to a short at said loop ends.
  • a switch for insertion within a waveguide comprising a resonant planar loop with open-circuited ends disposed within said waveguide, means for controlling the attenuation of energy propagated through said waveguide including a diode switching element having a forward and a reversebias impedance, a first transmission iine having an adjustable shorting stub connected to said diode to autiresonate with said diode reverse impedance, a second transmission line having a length equal to an odd number of quarter wavelengths measured within said line interconnecting said loop ends with said diode element, means for selectively biasing said diode to said forward impedance to permit the passage of energy in said waveguide and to said reverse impedance to attenuate said energy and means for varying the angle said planar loop makes with a plane of magnetic iield lines of a wave propagating in said waveguide to adjust the quantum of attenuation introduced.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Waveguide Switches, Polarizers, And Phase Shifters (AREA)
US483251A 1965-08-27 1965-08-27 Microwave switch Expired - Lifetime US3346824A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US483251A US3346824A (en) 1965-08-27 1965-08-27 Microwave switch
GB33944/66A GB1148193A (en) 1965-08-27 1966-07-28 Improvements in or relating to wave guide switches
FR71776A FR1488577A (fr) 1965-08-27 1966-08-02 Elément de commutation pour hyperfréquence
DE19661541723 DE1541723B2 (de) 1965-08-27 1966-08-10 Hochleistungs mikrowellenschalter mit hohem schaltver haeltnis
NL6611318A NL6611318A (OSRAM) 1965-08-27 1966-08-11

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US483251A US3346824A (en) 1965-08-27 1965-08-27 Microwave switch

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US3346824A true US3346824A (en) 1967-10-10

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US483251A Expired - Lifetime US3346824A (en) 1965-08-27 1965-08-27 Microwave switch

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US (1) US3346824A (OSRAM)
DE (1) DE1541723B2 (OSRAM)
GB (1) GB1148193A (OSRAM)
NL (1) NL6611318A (OSRAM)

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
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Publication number Publication date
DE1541723B2 (de) 1971-03-25
GB1148193A (en) 1969-04-10
DE1541723A1 (de) 1970-02-19
NL6611318A (OSRAM) 1967-02-28

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