MICROWAVE ARRANGEMENT AND METHOD RELATING TO SWITCHING

Abstract: The present invention relates to a microwave arrangement which comprises a device including a number of dielectric substrates, electrodes arranged on either side of said dielectric substrate(s) and microwave transmission means for coupling microwaves into and out of said arrangement. The substrate comprises SrTiO3 crystals or a dielectric material with similar properties and first and second connection means connected to each of the electrodes for application of a voltage, temperature regulating means for cooling down the device so that through application of a voltage or external electrical pulses the dielectric constant of the substrate can be switched between a first stable state and a second stable state giving a digital, switchable arrangement.

Description: Title: MICROWAVE ARRANGEMENT AND METHOD RELATING TO SWITCHING FIELD OF THE INVENTION The present invention relates to microwave switching arrangements comprising a device including electrodes arranged on a dielectric substrate. The invention also relates to methods of switching a microwave device between a first and a second state. STATE OF THE ART Various switches for microwaves are known. Generally they are of two different categories, namely mechanical or based on pin diodes or transistors. Mechanical devices are for example disclosed in Kunes M.A., and Connor G.G., "A Digitally Controlled Tunable High Power Output Filter for Space Applications", Proc. European Microwave Conference, pp. 681-686, 1989. Mechanical switches however suffer the drawbacks of being bulky and slow. Pin diode based switches suffer among others from the drawbacks of the pin diodes consuming large control currents. Passive and active microwave circuits are illustrated in Helszajn J., "Passive and Active Microwave Circuits" (J. Wiley, 1978). Microwave devices are known which are based on ferroelectric substrates, c.f. Lancaster M., Powell J, and Porch A, "Thin Film Ferroelectric Microwave Devices", Supercondt. Sci . Tecnol . , Vol. 11, pp. 1323-1334, 1998. Advantages of such devices are that they can be made to have a small size and they offer a large tuning ability and their control power consumption is low. At microwave frequencies the dielectric constant of the ferroelectrics can be tuned continuously and analog switches, phase shifters and other components based on ferroelectric materials are known. A switch which is based on the known voltage dependence of the dielectric constant however suffer from the drawback of showing a large temperature and voltage sensitivity since the dielectric constant itself is temperature and voltage dependent. Moreover, the well known switching mechanisms based on a low speed reorientation of ferroelectric domains is not observed at microwave frequencies and can thus be used for the development of microwave switches. In US-A-5 329 261 a limiter/switch is disclosed which is based on the non-linear property of a ferroelectric material. A new design of a device based on the well known properties of ferroelectric materials is shown. However, the non-linearity appears only at high microwave powers and it is not characterized by any bi- stability. The operation of the device is based on the monotonous dependence of the dielectric constant of the dielectricum on applied DC and microwave field. It is also disadvantageous that the microwave power has to be high. In "Tunable microwave devices based on bulk and thin film ferroelectrics", Integrated Ferroelectrics 1998, Vol. 22, No. 1-4, pp. 245-257 by Gevorgian et al . Double hysteresis loops, i.e. dielectric switching, is disclosed. No practical implementation are however deemed realistic among others since it is established that for analog, tunable filter application the produced switching is disadvantageous in that it causes uncertainities in the electrical control of the filter center frequency. Moreover the microwave loses in STO crystals increase drastically with an applied DC field which is a serious drawback for practical implementations of STO in analog, electrically tunable filters for which voltage independent tuning of the center frequency of the filter is required. SUMMARY OF THE INVENTION What is needed is therefore a microwave switching arrangement which can be made small, which has a low DC power consumption (control power) , operates at high microwave power levels and which has a high quality factor (Q-factor) . Still further a microwave switching arrangement is needed which is fast. An arrangement is also needed which is cheap and easy to fabricate. A method of switching a microwave device is also needed for which the above mentioned objects can be achieved. Therefore a microwave arrangement is provided which comprises a device with a dielectric substrate, electrodes arranged on the dielectric substrate and microwave transmission means for coupling microwaves in to and out of said arrangement. The substrate comprises SrTi0 3 crystals, particularly single crystals, or a dielectric material which has the same or similar properties. The switching arrangement is digitally switched. First and second connection means are connected to each of the electrodes and temperature regulating means are provided for cooling down the device through appropriate application of a voltage or external electric pulses the dielectric constant of the substrate can be switched between a first stable state and a second stable state, thus providing for bistability. The quality factors (Q-factors) are high and substantially equal for both states, i.e. an "on"- state and an "off-state. In one implementation the connecting means are so arranged that the electrodes are short circuited or equivalent thereto. The temperature regulating means are used to cool down the device when the DC voltage source is on but no voltage applied. This constitutes an equivalence of short- circuiting the electrodes and cooling. In a particular implementation the connecting means are connected to a DC voltage source. After cooling to below 80K, a DC-field is applied, for which a threshold value is given, Et r 0,35 . [l+CT/lO) 1 - 35 ] [kV/cm], in order to make the STO crystal undergo a paraelectric-to-antiferroelectric phase transition. In an alternative implementation if the electrodes are open circuited while the crystal is cooled; i.e. not short-circuited, again a DC voltage above a given threshold value is applied to make the STO crystal undergo a phase transition to an antiferroelectric state as discussed above. Particularly the electrodes are electrode plates which particularly are arranged to form a resonator. In a particularly advantageous implementation, the resonator plates are arranged to form a parallell-plate resonator which may be circular, rectangular, square-shaped or of any other appropriate shape, regular as well as irregular. In an alternative implementation the electrodes are arranged to form a parallell-plate capacitor. The electrodes may also be arranged to form a section of a transmission line. Particularly the temperature regulating means comprises cooling means for cooling the device to a temperature of substantially 80K or lower. In a particular implementation the device is cooled to a temperature of 77°K or below that when applying a DC voltage above a given threshold value, i.e. the temperature of liquid Nitrogen (N), i.e. 77°K. The device may also be cooled to a temperature of about 60-62°K or below that. The first state of the dielectric constant corresponds to a first resonant frequency whereas the second state of the dielectric constant corresponds to a second resonant frequency corresponding to a switching "on"-frequency and a switching "off"- frequency respectively. For a circular parallell-plate resonator f orL is proportional to —== ■ whereas the off frequency f 0 ---- is proportional to Co r ^ To provide for switching, an external applied voltage can be changed in a given manner using the double hysterises loop of the dielectric constant so that switching is provided between said first and said second state. External electrical pulses may also be applied in an appropriate manner to provide for the switching. Particularly the applied voltage is superimposed on a biasing voltage. In a particular implementation the electrodes comprise YBCO. The electrodes may be superconducting, high temperature superconducting or normally conducting. Particularly the voltage for which switching occurs is given by the thickness of the STO single crystal substrate and the temperature of operation. At the operation temperature a constant DC biasing voltage V DC is applied (on which the switching voltage or electrical pulses are super imposed) . In a most advantageous implementation cooling down is done to 77°K or similar, and the temperature is kept to be lower than 100°K keeping the crystal in the antiferroelectric state allowing switching. Particularly the arrangement comprises a digital microwave switch. In an alternative embodiment it comprises a digital phase shifter. Still further it may comprise a digitally switched filter such as a band reject filter or a band pass filter. The arrangement finds one advantageous use in wireless communication systems. Therefore also a method of switching a microwave device comprising a dielectric substrate on which a number of electrodes are arranged, between a first state and second state is disclosed. The dielectric substrate comprises SrTi0 3 single crystals and the method comprises the steps cooling the device to a temperature of about 77°K or below that, and applying a voltage in a given manner or external electrical pulses to switch the dielectric constant of the substrate material between a first and a second state. The device is digital. Alternatively the method comprises the steps of activating DC supply means without applying a voltage, cooling the device ro a temperature of about 80°K or to a lower temperature and applying a voltage in a given manner or external electrical pulses to switch the dielectric constant of the substrate material between a first and second state. In one implementation the electrodes are short-circuited before cooling to about 80°K or lower. In another implementation the electrodes are open-circuited, cooling down need only be done to 77°K (or below that) and a voltage is applied to stimulate a phase transition from a paraelectric state not allowing switching into a antiferroelectric state enabling switching. It is an advantage of the invention that a nearly constant and voltage independent dielectric constant (ε on and ε off ) within a wide voltage range is obtained. This makes the choice of a biasing voltage value less crucial in practical devices. It is also an advantage that substantially the same dielectric losses (1/Q ; , Q 0 being the unloaded quality factor of the resonator) result in both states. A further advantage of the invention is that the leakage current is practically zero in both states. Another advantage is that switching occurs at temperatures below 80°K or particularly below 77°K. According to the invention a first step consists in applying a DC- field E > E t hr to make the dielectric substrate antiferroelectric, i.e. the double loop hysteresis is produced. This can be done with open-, or short-circuited electrode cooling. A second step consists in, while the antiferroelectric phase (double loop) is generated, this can be used for switchable operation of e.g. the filter, by applying (superimposing) control voltages (or pulses). BRIEF DESCRIPTION OF THE DRAWINGS The invention will in the following be further described in a non- limiting way with reference to the accompanying drawings in which: Fig 1 is a diagram explaining the principle of operation of one arrangement according to the present invention showing two states of a bulk STO resonator, Fig 2 illustrate experimental data for the frequency response of a single pole rejection filter, Fig 3 illustrates the application of external electric pulses for switching a device according to one embodiment of the invention, shows a switchable band pass filter based on switchable resonators, shows the equivalent electric circuit of the filter of Fig 4A, shows a switchable band reject filter based on a switchable resonator, schematically illustrates the equivalent electric circuit of the filter of Fig. 5A, shows a digital phase shifter comprising a transmission line, shows an another embodiment of a digital phase shifter comprising an alternative transmission line, schematically illustrates a lumped capacitor, shows the equivalent electrical circuit of the capacitor of Fig 8A, shows a first embodiment of coupling in a transmission line, shows a second embodiment of coupling into a transmission line, illustrates the resonant frequencies with short- circuited electrodes, Fig 10B shows resonant frequencies with open-circuited electrodes, and Fig 11 illustrates a STO crystal used as a parallel plate resonator. DETAILED DESCRIPTION OF THE INVENTION The most general device of the present invention can be said to be a digital switch. This switching functionality can be used in resonators, capacitors, transmission lines, many kinds of filters etc. For explaining the operation is therefore, for reasons of simplicity, merely referred to a digital switch. The operation of the switch is based on a double hysteresis loop in the dielectric constant which has been detected at microwave frequencies such as about 1 GHz or 1.5 GHz. The principle of operation of such a switch is explained with reference to the experimental dependence shown in Fig. 1. The illustrated experimental results are obtained with a parallell-plate resonator as disclosed in SE 9502137-4 "Tunable Microwave Devices" which is a Swedish patent application filed by the same applicant and which herewith is incorporated herein by reference. The illustrated resonator comprises a substrate of STO (SrTi0 3 ) plated with YBCO. To obtain switching according to a first embodiment, the resonator is cooled with the DC supply in its "on" state and with V=0. Alternatively the electrodes or electrode plates are short circuited when cooling. This is an equivalent way of providing the same result. A switching in the dielectric constant occurs with two distinct states of the dielectric constant, ε on and ε 0 ff corresponding to the resonant frequencies f on which is proportional to and f off which is proportional to r being the radius of the circular resonator (in case the resonator is circular) and c 0 being the speed of light in vacuum. In the figure the arrows A illustrate what happens when the applied voltage is first increased and then decreased again. f off is as referred to above the resonant frequency of the switch in an off state and the dependence of the resonant frequency can be seen. After reaching a maximum, the voltage is again decreased and another substantially stable state is obtained, corresponding to the "on" frequency f on . The corresponding situation occurs when applying a negative voltage as indicated through the arrows B in the figure. The unloaded Q (quality) factor is illustrated to the right in the figure and the electric field in kV/cm is illustrated on the top. According to the invention the switching arrangement, particularly the dielectric substrate (the ferroelectric) is treated through cooling with particularly short-circuited DC plates or similar producing the equivalent thereof, down to a temperature below 8OK, particularly to 77K or below that, so that the two stable states in the dielectric constant are generated for a certain range of the DC electric field. In this range of electric fields the ferroelectric substrate has different dielectric constants for the same DC field. This relates to a mechanism for reaching of bi-stablity, i.e. two stable states. Alternatively, as will be further discussed below, the electrodes may be open-circuited while cooling the device, i.e. no short-circuiting is required. In both cases (short-circuited or open-circuited electrodes) bistability is achieved at 80(77)K or below that. In Fig. 2 the measured frequency response of a single pole rejection filter is illustrated by the single pole filter as in its two different states at the applied voltage of 70V. As can be seen there is a first dip in reflected power P R , in dB for a first frequency f on corresponding to approximately 1,034 GHz and a second dip in reflected power for a second resonant frequency f off at about 1,06 GHz. This figure thus shows the performance of a single pole switchable STO filter according to the invention which operates as a reflection type filter with resonant frequencies in the on and the off states respectively. To achieve a switching performance, the device is advantageously DC biased as illustrated in Fig. 1. A nearly constant (voltage independent) dielectric constant, f on and f 0ff is obtained in a wide voltage range. This makes the choice of a biasing voltage value much less crucial in practical devices. The dielectric losses (1/Qo, Qo being the unloaded quality factor of the resonator) are almost the same in both states. Furthermore there is practically zero current in both states and switching occurs at temperatures below 60K or particularly below 70K, (or even more particularly at about 77°K as will be discussed below) . As referred to above, it is evident that although the above mentioned mainly refers to a resonator, similar switching can be achieved in parallell-plate capacitors. In both cases the main switching voltage will be given by the thickness of the STO crystal and the temperature of operation. Fig. 3 is a diagram intending to show one embodiment according to which external electrical pulses are applied for switching the device, such as a resonator, a capacitor or generally a switch. The horizontal axis illustrates the applied voltage whereas on the positive vertical axis the frequency is indicated and on the negative vertical axis the time is indicated. As discussed above it is here supposed that the device is cooled to an operation temperature below 60K (70K) with the DC supply on and with the zero voltage. At the operation temperature a constant DC bias is applied, V DC . The turning on and off pulses are superimposed on V DC and again the on and off frequencies are obtained for the same voltage. For switching on, it is supposed that at a pulse is superimposed on V DC to provide a total voltage V=V DC +V max . At t=t 2 , the pulse is removed and the voltage is V=V DC . When switching off, a negative pulse is applied at t=t 2 . The total voltage V will then be V DC -V pu i se =0. At t=t 3 the negative pulse is removed and the total voltage becomes V=V D c. Fig. 4A schematically illustrates a switchable band pass filter 100 based on switchable resonators 10, 20 each comprising a dielectric substrate (e.g. of STO) 1,1' on either sides of which electrode plates 2, 3; 2', 3' are provided. The coupling capacitor C c 4 is shown between the parallelly arranged resonators. Fig. 4B is the equivalent electrical circuit 100A for the filter 100 of fig 4A. In Fig. 5A a switchable band reject filter 200 is illustrated whereas its equivalent circuit 200A is illustrated in Fig. 5B. The band reject filter 200 includes a parallell-plate STO resonator 30 including a substrate 1" on either sides of which electrode plates 2", 3" are arranged. In Fig. 2 above the performance of such a filter is illustrated. Fig. 6 shows a first embodiment of a transmission line 300 comprising an STO substrate 5 on which two transmission lines 6,7 are arranged. A biasing voltage V DC is applied to the transmission line strips 6,7 and the microwave in- and output respectively are illustrated. Fig. 7 shows a second embodiment of a transmission line 400 in which an STO substrate 5' provided with a transmission line strip 6" thereon. The application of the biasing voltage V DC between the strip 6' and the ground plane is illustrated in the figure as the microwave in- and outputs respectively. The length 1 of the devices of Fig. 6 and 7 is larger than or substantially equal to λ g , λ g being the microwave wavelength in the substrate. Fig. 8A is an example of a lumped capacitor, i.e. D π , ax «λ g . In Fig. 8B the equivalent circuit 500A of the lumped capacitor 500 of Fig. 8A is illustrated indicating the C on and C 0 ff capacitances respectively. In Fig. 9A a first embodiment is illustrated merely schematically illustrating the coupling/connecting into a transmission line whereas in Fig. 9B a second alternative of coupling or connecting into a transmission line is illustrated. The elements as illustrated through Figs. 6-8 are examples on different kinds of digital phase shifters according to the present invention. An alternative way of obtaining switching will now be discussed. These are based on the observations that; with single crystal STO resonators a double loop hysteresis is provided at about 77°K, at a frequency of about 1.5 GHz. As discussed above relating to the proceeding embodiments a double loop hysteresis in field dependent dielectric permittivity appears at e.g. 62°K or below in annealed STO devices cooled with short-circuited electrodes. Experiments have been performed using STO (100) single crystals about 0,5 mm thick and having circular, disk shape c.f. Fig. 11. Two surfaces of the plates are epitaxial grade polished, while the cylindrical surfaces have optical grade polishing. Thin (about 0.3 μm) superconductor YBCO films have been deposited on both faces of the disks by magnetron sputtering, laser ablation, or co-evaporation techniques. Gold films (1.0 μm) provide ohmic contact to the YBCO films and protect them from possible environmental effects. During epitaxial growth of YBCO electrodes the STO crystals have been objected to heating at about 700-800 C in oxygen atmosphere (about 0.6 mbar) during 0.3-3 hours. After the deposition crystals have been cooled down to room temperature with a speed 10-20°/min in oxygen atmosphere (about 1.0 atm) . The STO crystals in the final parallel-plate structure are transparent, without any visible color, indicating that no charged defects have been introduced during electrode fabrication. I-V measurements have been carried out in a wide temperature range (20-300K) to check the levels of leakage currents, their effect on the noise generation. Maximum applied field is E=V/d=40/0.05=800 V/cm. The resonator is a cooper box (resonator package) was placed in a vacuum cryo-cooler. At temperatures below 220 K, the currents were smaller than lpA and not resolvable for the measurement set- up. Microwave measurements are performed by immersing the resonator (parallel-plate STO disk in a copper package) in liquid Nitrogen (77K) . The crystals have been cooled down with open- circuited and short-circuited electrodes. The actual measurements are started after temperature stabilization. No external mechanical stress is applied to the resonator. An external bias tee, Fig. 11 is used to apply DC voltage. Complex reflection coefficient Sn, is used to evaluate the unloaded resonant frequencies and Q-factors of the resonator depending on the DC bias voltage. Figs. 10A, 10B depict the dependencies of the resonant frequencies of STO resonators at 77°K, cooled down with short-circuited. Fig. 10A, and open-circuited, Fig. 10B, plates. In both cases, for applied DC voltages lower then 300 V, the reversal of the applied DC field does not lead to a double hysteresis loop. The resonant frequencies saturate and start decreasing notably where the allied voltage start exceeding 300 V, and then start increasing again above about 400 V. Further voltage cycling (including polarity reversals, c.f. the earlier mentioned document "Tunable ..." by Gevorgian et al . leads to a double loop hysteresis in resonant frequency, f nm without returning to the starting branch of the f nm - curve. Thus, at an application of about 300-400 V a phase transition starts, from curve PI, paraelectric phase, into a antiferroelectric phase, and, once the transition has occurred, if the voltage is lowered again, it will remain in antiferroelectric state, curve Al, and, if the voltage is increased again, it will follow curve A2 (also antiferroelectric phase) and so on, i.e. it will not be returned to curve PI unless the temperature is increased. If the temperature is increased to e.g. room temperature, it will be returned to PI (paraelectric phase) . At least if the temperature is kept quite low, e.g. 100K, it will thus be remained in the antiferroelectric state permitting switching. This is equivalent to having a double loop hysteresis in the dielectric permittivity due to the simple relationship: C θ' C nm Iran — 2ττrSε where Co = 3 x 10 8 m/s is the velocity of light in vacuum, ε' is the real part of the relative dielectric permittivity of STO crystal, r is the radius of the conducting plate, k nm are the roots of Bessel functions first derivatives with mode indexes n and m. The original state, i.e. starting branch in f nm - curve is restored upon heating the resonator to a room temperature. As can be seen the fo-V and tanδ-V performances of the resonator are the same regardless the initial cooling conditions, i.e. whether the resonator was cooled with short-circuited or open-circuited electrodes. In Figs. 10A, 10B the cooled resonant frequencies for the two different embodiments, i.e. the one using short circuited electrodes and the other for which the electrodes need not be short-circuited, versus applied DC voltage are illustrated. The original paraelectric performance below 300V, Figs. 10A, 10B, followed by stabile and repeatable hysteresis loops, after the first time voltage incasing 300 V, indicates that an electric field stimulated paraelectric-to-antiferroelectric phase transition takes place in STO. That switching can be obtained at the temperature of liquid nitrogen (77°K) is extremely advantageous and actually the electrodes need not be short-circuited. According to the present invention are thus a large number of digital microwave switchable devices suggested, and they may either be provided through cooling either with short-circuited or with open-circuited electrodes to temperatures below about 80°K if a sufficiently high voltage (DC field) is applied, such that an electrically stimulated phase transition is produced. All the specifically mentioned implementations, e.g. switchable digital filters, phase shifters etc. may be produced one way or the other. The field, E, is equal to V/d, wherein V is the applied voltage, d the thickness of the dielectric substrate e.g. STO. The threshold value E t r = 0,35 . [l+(T/10) 1 - 35 ] [kV/cm] , wherein T is the temperature in ° Kelvin. The electric field-induced paralelectric-to-antiferroelectric phase transition may be associated with the electric field assisted global reduction of the symmetry and polarization of the crystal lattice. It is not related to possible phase transitions at about 60 K. The global phase transition may be accompanied by local ones leading to diffused phase transition. The frequency shifting is less sensitive to electric field and temperature instabilities if a phase transition as discussed above is produced which is very advantageous. Regardless of the cooling conditions (short or open circuit electrodes) the switching at the given temperature is achieved by applying a DC field above some threshold value. Below this threshold value the initial crystal (just after the cooling to the desired temperature) is in paraelectric state and does not have switchable properties. Above this voltage the crystal undergoes phase transition into a antiferroelectric state characterized by high voltage hysteresis loop (i.e. switching) and remains in this phase as far as the temperature does not exceed e.g. 100 K. It is an advantage of the present invention that small switches can be built and in that the DC power consumption is low and in that it enables building of various kinds of microwave devices such as digital phase shifters, digitally switched band pass and band reject filters etc. for high microwave power levels (e.g. above 20 dBm) . Other advantages have already been discussed earlier in the application. It shall also be clear that the invention is not limited to the explicitly shown embodiments but that it can be varied in a number of ways within the scope of the appended claims. The cooling means are not explicitly illustrated in the figures since they can be of any kind and arranged in any appropriate manner.

Claims: CLAIMS 1. A microwave arrangement (100;200;300; 400; 500) comprising a device (10, 20; 30) comprising a dielectric substrate (1;1' ;1";5;5' ;8) , electrodes (2, 3;2' , 3' ;2" , 3" ; 6, 7; 6' ; 9, 9) arranged on said dielectric substrate (1' -1" ; 5; 5' -8' ) , and microwave transmission means for coupling microwaves in to and out of said arrangement, c h a r a c t e r i z e d i n that it is digital, that the substrate (1; 1' ; 1" ; 5; 5' ; 8) comprises SrTi0 3 crystals (STO) or a dielectric material with similar properties, first and second connection means connected to each of said electrodes, temperature regulating means for cooling down said device so that through application of a voltage, a phase transition is produced from a first to a second state in which the dielectric constant of the substrate (1; 1' ; 1" ; 5; 5' ; 8) can be switched between a first stable state and a second stable state. 2. An arrangement according to claim 1, c h a r a c t e r i z e d i n that the connecting means are connected to a DC voltage source and in that the temperature regulating means are used to cool down the device when the DC voltage source is on and zero voltage is applied. 3. An arrangement according to claim 1, c h a r a c t e r i z e d i n that the dielectric substrate (1;1' ; 1" ; 5; 5' ; 8) comprises SrTi0 3 single crystals. 4. An arrangement according to any one of claims 1-3, c h a r a c t e r i z e d i n that the electrodes are electrode plates (2, 3; 2' , 3' ; 2" , 3" ; 9, 9) . 5. An arrangement according to claim 4, c h a r a c t e r i z e d i n that the electrode plates are arranged to form a resonator (10; 20; 30) . 6. An arrangement according to claim 5, c h a r a c t e r i z e d i n that the resonator plates are arranged to form a parallell-plate resonator (10;20;30). 7. An arrangement according to claim 5 or 6, c h a r a c t e r i z e d i n that the resonator is circular (10;20;30) . 8. An arrangement according to claim 5 or 6, c h a r a c t e r i z e d i n that the resonator is rectangular, square-shaped or of any other shape. 9. An arrangement according to claim 5, c h a r a c t e r i z e d i n that the electrodes are arranged to form a parallell-plate capacitor (500) . 10. An arrangement according to any one of claims 1-3, c h a r a c t e r i z e d i n that the electrodes comprise transmission strip lines (6,7;6') arranged to form a section of a transmission line. 11. An arrangement according to any one of the preceding means, c h a r a c t e r i z e d i n that the electrodes are short-circuited and in that the temperature regulating means comprises cooling means for cooling the device to a temperature of 70K or lower. 12. An arrangement according to claim 11, c h a r a c t e r i z e d i n that a device is cooled to a temperature of about 62K or lower. 13. An arrangement according to any one of claims 1-10, c h a r a c t e r i z e d i n that the device is cooled to a temperature of about 80K and in that a voltage or an electric field exceeding a given threshold value is applied to produce the phase transition. 14. An arrangement according to claim 13, c h a r a c t e r i z e d i n that the threshold value of the field is E t hr = 0,35 . [ 1+(T/10) 1 - 35 ] [kv/cm] , T being the temperature. 15. An arrangement according to claim 13 or 14, c h a r a c t e r i z e d i n that a phase transition occurs at the application of a voltage of about 300-400 V. 16. An arrangement according to claim 14, 15 or 16, c h a r a c t e r i z e d i n that the electrodes are short-circuited. 17. An arrangement according to claim 14, 15 or 16, c h a r a c t e r i z e d i n that the electrodes are open-circuited. 18. An arrangement according to at least claim 7, c h a r a c t e r i z e d i n that the first state of the dielectric constant corresponds to a first resonant frequency and the second state of the dielectric constant corresponds to a second resonant frequency, f on and f off respectively. 19. An arrangement according to claim 18, c h a r a c t e r i z e d i n that fon is proportional to and f off is proportional to r s off 20. An arrangement according to any one of the preceding claims, c h a r a c t e r i z e d i n that through changing an external applied voltage in a given manner switching is provided when the dielectric substrate is in the antiferroelectric phase. 21. An arrangement according to claim 6, 7 or 8 , c h a r a c t e r i z e d i n that the electrodes (2, 3;2' , 3' ;2" , 3" ; 6, 7; 6' ; 9, 9) comprise YBCO. 22. An arrangement according to any one of the preceding claims, c h a r a c t e r i z e d i n that the voltage for which a phase transition occurs depends on the thickness of the STO single crystal substrate and the temperature of operation. 23. An arrangement according to any one of the preceding claims, c h a r a c t e r i z e d i n that at the operation temperature a constant DC biasing voltage V DC is applied. 24. An arrangement according to any one of the preceding claims, c h a r a c t e r i z e d i n that it comprises a digital microwave switch. 25. An arrangement according to any one of claims 22, c h a r a c t e r i z e d i n that it comprises a digital phase shifter. 26. An arrangement according to any one of the preceding claims, c h a r a c t e r i z e d i n that it comprises a switchable digital filter (300;400). 27. An arrangement according to claim 23, c h a r a c t e r i z e d i n that it comprises a digitally switchable band reject filter (400) . 28. An arrangement according to claim 25, c h a r a c t e r i z e d i n that it comprises a digitally switchable band pass filter (300) . 29. Use of an arrangement according to any one of the preceding claims in a wireless communication system. 30. Method of switching a microwave device between a first state and a second state, which device comprises a dielectric substrate on which a number of electrodes are arranged, c h a r a c t e r i z e d i n that the dielectric substrate comprises SrTi0 3 crystals, the method comprising the steps of: - cooling the device to a temperature of about 80K or to a lower temperature, - applying a voltage above a given threshold value to produce a phase transition into a state allowing dielectric switching, - switching the dielectric constant of the substrate material while in said state. 31. A method according to claim 30, c h a r a c t e r i z e d i n that it comprises the steps of: - applying a voltage or an electric field above a given threshold value such that the crystals undergo an electrically stimulated phase transition from a first parelectric state to a second antiferroelectric state allowing, dielectric switching, - producing dielectric switching through application of a voltage or electric pulses. 32. A method according to claim 30 or 31, c h a r a c t e r i z e d i n that the electrodes are open-circuited. 33. A method according to claim 31 or 32, c h a r a c t e r i z e d i n that the threshold value is about 300-400 V. 34. Method of providing a switchable microwave device, which device comprises a dielectric substrate on which a number of electrodes are arranged, c h a r a c t e r i z e d i n that the dielectric substrate comprises SrTi0 3 crystals, the method comprising the steps of: - activating DC supply means but with a zero biasing voltage, cooling the device to a temperature to about 80K or to a lower temperature, applying a voltage exceeding a threshold value to make the electric substrate undergo a phase transition to a state allowing switching, applying a voltage or external electrical pulses in a way to switch the dielectric constant of the substrate material between a first and a second stable state giving a digitally switched device.

Inventors: CARLSSON ERIK, ERIKSSON ANDERS, GEVORGIAN SPARTAK, WIKBORG ERLAND, CARLSSON, ERIK, ERIKSSON, ANDERS, GEVORGIAN, SPARTAK, WIKBORG, ERLAND
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 2000
Main classification: H01P1
IPC codes: H01P1