Patent Description:
IRE is a soft tissue ablation technique that applies short pulses of strong electrical fields to create permanent and hence lethal nanopores in the cell membrane, thus disrupting the cellular homeostasis (internal physical and chemical conditions). Cell death following IRE results from apoptosis (programmed cell death) and not necrosis (cell injury, which results in the destruction of a cell through the action of its own enzymes) as in all other thermal or radiation-based ablation techniques. IRE is commonly used in tumor ablation in regions where precision and conservation of the extracellular matrix, blood flow and nerves are of importance. Some examples of systems using IRE are provided below.

<CIT> shows examples for coupling a power source to a set of voltage sources (a capacitor stack), with independent outputs available at a plurality of different levels.

<CIT>, describes an electrical signal generator that is stated to apply between one or more pairs of electrodes signals of first and second types in alternation. The signals of the first type comprise a sequence of bipolar pulses having an amplitude sufficient to cause irreversible electrophoresis in tissue contacted by the electrodes.

<CIT>, to Viswanathan, describes a generator that may include a set of electrode channels coupled to a set of electrodes during use. Each electrode channel from the set of electrode channels may include a first switch from a first set of switches and a second switch from a second set of switches. A set of energy sources may be coupled to a third set of switches. The third set of switches may be configured to switch from an off state to an on state to couple the set of energy sources to the set of electrodes.

Chinese Patent Application <CIT>, describes an irreversible electroporation circuit that comprises an energy storage circuit, a first DC AC conversion circuit, an isolation transformation circuit, and an AC DC conversion circuit, which are connected in turn.

European Patent Application <CIT>, describes a pulse generator that is stated to be adapted to produce a series of electrical pulses having a voltage of between <NUM> and <NUM> Volts and a duration of between <NUM> and <NUM> microseconds. The pulses may be applied to trat tissue.

An article titled "High-Voltage Pulse Source for Cell Electroporation," by Červinka et al. , in the <NUM> proceedings of the 12th International Conference on Mechatronics, describes a development and test process of impulse power source for the purpose of delivering short high-voltage pulses into the treated tissue.

The foregoing and other features and advantages of the disclosure will be apparent from the following, more particular description of preferred embodiments of the disclosure, as illustrated in the accompanying drawings.

The invention is defined in appended independent claims <NUM> and <NUM>. Further embodiments are defined in appended dependent claims. The short electrical pulses that are used for IRE (irreversible electroporation) ablation are typically high voltage pulses, of the order of <NUM>-<NUM> kV, e.g., <NUM> kV, that transfer high currents, typically in the approximate range of <NUM> - <NUM> amperes, to tissue being ablated. The current transferred depends on the load, which typically ranges between <NUM> - <NUM> ohms. The pulses may be transferred between a pair of electrodes of a catheter, where each electrode is a single electrode. Alternatively, one or both electrodes may comprise multiple "sub-electrodes. " Both electrodes are typically in proximity to the tissue being ablated, although in some cases only one electrode is proximate to the tissue, and the other electrode of the pair is distant from the tissue. For example, if the tissue being ablated is in the heart of a patient, the other electrode may be on the skin of the patient.

For the case where both electrodes are in proximity to the tissue being ablated, an IRE ablation procedure typically needs to have pulses transferred between multiple pairs of electrodes in different physical locations, so as to efficiently ablate a selected target region of the tissue. Where there are a large number of electrodes, this becomes problematic if the IRE generator has fewer channels than the number of electrodes, as may be the case in legacy situations. Consequently, the pulse delivery needs to be switched, or multiplexed, between the multiple pairs sequentially in time. While theoretically possible, such switching using switches is expensive, since the switches need to be rated for transferring high powers, i.e., need to be able to transfer, without being damaged, the high voltages and high currents referred to above. Typical low-cost relay switches are only rated for up to <NUM> kV. Devices that are rated for transferring high powers are also termed herein high-rated devices.

Examples of the present disclosure provide a multiplexer that may be used to efficiently switch high voltage/current IRE pulses between channels. The multiplexer comprises a controller controlling a plurality of switching assemblies, each assembly being comprised of multiple relays. Each relay in an assembly needs only to be rated for transferring low powers, i.e., only needs to be rated for a voltage and a current that are a fraction of the IRE pulse voltage and current. Devices that are rated for transferring low powers are also termed herein low-rated devices. Herein a low-rated device is assumed to be able to operate at no more than <NUM> kV, and to transfer no more than <NUM> amperes.

However, when configured as described hereinbelow, each assembly is high rated, i.e., taken together, the components of the assembly are able to transfer, without being damaged, the high voltages and currents associated with IRE pulses.

Each switching assembly is formed of sets of low-rated components. In one example, described hereinbelow, there are two sets, each set comprising a pair of double-pole single throw (DPST) low-rated relays connected in parallel. Each relay comprises respective first and second contacts, so that in each set all first contacts are connected together, and all second contacts are connected together. In each set a capacitor is connected in parallel with the pair of relays.

The switching assembly is formed by connecting the two sets in series, so that the second contacts of the first set connect to the first contacts of the second set. A first assembly terminal is connected to the first contacts of the first set, and a second assembly terminal is connected to the second contacts of the second set.

As is explained below, the switching assembly acts as a high-rated single pole single throw (SPST) relay, wherein the first and second assembly terminals are either connected or disconnected. Assembly terminals that are connected are also herein described as terminals that are closed, and assembly terminals that are disconnected are herein also described as terminals that are open.

Within the switching assembly the first set and the second set comprise respective power supplies driving the DPST relays of the set. The multiplexer controller activates the power supplies to connect all first and second contacts of the first set and all first and second contacts of the second set, so connecting the first and second assembly terminals. When the power supplies are deactivated, all first and second contacts of the first set and all first and second contacts of the second set disconnect so that the first and second terminals are disconnected. Relay contacts that are connected are also herein described as contacts that are closed, and relay contacts that are disconnected are herein also described as contacts that are open.

Typically, to maintain the high rating of the switching assembly the power sources of the first and second sets of components are isolated from each other. Electrodes on the catheter are isolated from the power sources to avoid unexpected surges in voltage and/or current from the power supply input.

In operation, power transferring between the first and the second assembly terminals is distributed between all the relays of the assembly. Because of the distribution, the current through each relay contact is a fraction, typically approximately <NUM>% because of the four parallel current paths, of the IRE pulse current. Also because of the distribution and because of the capacitors, the voltage between each relay's first and second contacts is a fraction of the IRE pulse voltage; if the capacitors across each set of the assembly are equal, and if the impedance of the capacitors is significantly less than that of the relays, the voltage is approximately <NUM>% of the IRE pulse voltage.

The example above assumes that DPST relays are used in the switching assembly. An alternative example uses two low rated SPST relays in place of each DPST relay, and those having ordinary skill in the art will be able to adapt the above description, mutatis mutandis, for forming the switching assembly using SPST relays.

To operate as a multiplexer, for example for a catheter having <NUM> electrodes, each electrode is connected to a respective switching assembly, and the assemblies are individually controlled by a controller.

Reference is now made to <FIG>, which is a schematic pictorial illustration of a multi-channel IRE (irreversible electroporation) system <NUM> used in an IRE ablation procedure. In the pictured example, a physician <NUM> performs a multi-channel IRE ablation procedure using IRE system <NUM>. Physician <NUM> performs the procedure on tissue <NUM> in a heart <NUM> of a subject <NUM>, using an ablation catheter probe <NUM> having a distal end <NUM>, herein by way of example assumed to comprise a basket catheter <NUM>. Basket catheter <NUM> comprises multiple ablation electrodes <NUM> arranged along lengths of spines <NUM> of the catheter.

IRE system <NUM> comprises a processor <NUM> and an IRE module <NUM>, and the IRE module comprises an IRE generator <NUM> and an IRE controller <NUM>. An IRE generator similar to generator <NUM> is described in <CIT>. As is detailed below, IRE generator <NUM> generates trains of electrical pulses, which are directed to selected electrodes <NUM> so as to generate currents <NUM> therebetween, for performing an IRE procedure. The waveforms (timing and amplitude) of the trains of electrical pulses are controlled by IRE controller <NUM>. A controller similar to controller <NUM> is also described in the above-referenced U. Patent Application.

<FIG> is a schematic illustration of a voltage vs. time graph <NUM> of trains of bipolar electrical pulses generated by IRE generator <NUM>, according to an example of the present disclosure. Typically, pulses are conveyed between electrodes <NUM>, comprising a transmit and a return electrode that are selected by multiplexer <NUM>, and are in the form of one or more bursts <NUM> of pulses. Herein a burst comprises one or more trains <NUM> of individual bipolar pulses <NUM>. In the figure, train <NUM> comprises eight individual pulses, but a train may comprise other than eight individual bipolar pulses.

Each pulse <NUM> has an amplitude of approximately <NUM> V, <NUM> V, or approximately <NUM> V. , for an amplitude of 3000V the potential V+ of a positive section of the bipolar pulse is +<NUM> V and the potential V- of a negative section of the pulse is - <NUM> V. In one example, the pulses from IRE generator <NUM> have a frequency of <NUM>; in another example the frequency is <NUM>. Typical ranges of values of pulse parameters, including values for the pulse amplitude and frequency, in pulses from IRE generator <NUM>, are given in Table I below. From the values for the pulse amplitude it will be understood that the rating of multiplexer <NUM> needs to be at least <NUM> V.

Returning to <FIG>, processor <NUM> and IRE controller <NUM> each typically comprise a programmable processor, which is programmed in software and/or firmware to carry out the functions that are described herein. Alternatively or additionally, the processors and the controller may comprise hard-wired and/or programmable hardware logic circuits, which perform at least some of these functions. Although processor <NUM> and IRE controller <NUM> are shown in the figures, for the sake of simplicity, as separate, monolithic functional blocks, in practice some of these functions may be combined in a single processing and control unit. In some examples, IRE controller <NUM> resides within IRE module <NUM>, since typically high-speed control signals are transmitted from the IRE controller to IRE generator <NUM>. However, provided that signals at sufficiently high speeds may be transmitted from processor <NUM> to IRE generator <NUM>, IRE controller <NUM> may reside within the processor.

Processor <NUM> and IRE module <NUM> typically reside within a console <NUM>. Console <NUM> comprises input devices <NUM>, such as a keyboard and a mouse, operated by physician <NUM>. A display screen <NUM> is located in proximity to console <NUM>. The screen <NUM> may be utilized to display an image of the heart <NUM>. Display screen <NUM> may optionally comprise a touch screen, thus providing another input device.

IRE system <NUM> may additionally comprise one or more of the following modules (typically residing within console <NUM>) :.

A method of position tracking using external magnetic fields is implemented in the CARTO™ system, produced by Biosense Webster Inc. (Irvine, Calif. ) and is described in detail in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>, in <CIT>, and in <CIT>, <CIT> and <CIT>.

Alternatively or additionally, module <NUM> may use a tracking system based on currents transferred through, or impedances seen by, electrodes <NUM>. In such a system module <NUM> estimates the position of a given electrode <NUM> in response to currents or impedances between the given electrode and a plurality of surface-electrodes <NUM> that are attached to the skin of subject <NUM>. An Advanced Current Location (ACL) system, made by Biosense-Webster (Irvine, California), which is described in <CIT>, is such a tracking system.

Probe <NUM> is coupled to console <NUM> via an electrode multiplexer <NUM>, described in more detail with respect to <FIG> and <FIG>. IRE signals are thus transferred between IRE generator <NUM> and electrodes <NUM> of basket catheter <NUM> via multiplexer <NUM>. Similarly, other signals from electrodes <NUM>, such as ECG signals, and/or those that may be used for tracking the position of the electrodes of basket catheter <NUM> using an ACL system referred to above, may be received by processor <NUM> via multiplexer <NUM>.

An external electrode <NUM>, or "return patch", may be additionally coupled externally between subject <NUM>, typically on the skin of the subject's torso, and IRE generator <NUM>. While IRE signals are typically generated so that IRE current flows between electrodes <NUM>, in some cases the IRE current may be configured to flow between one or more electrodes <NUM> and external electrode <NUM>.

<FIG> is a schematic diagram of multiplexer <NUM> and its connections to IRE generator <NUM> and electrodes <NUM>. In the following description IRE generator <NUM> is assumed to comprise <NUM> channels <NUM>, each of which may be configured to transmit or receive IRE signals from the generator. As is explained below, the <NUM> channels are multiplexed to <NUM> electrode channels C1 - C30 connected to electrodes <NUM> that are located on spines <NUM>. Hereinbelow, individual elements of entities in the figure are identified, as necessary, by having an added subscript. For example, different channels <NUM> are identified with an added subscript <NUM>n, where n is an integer from <NUM> to <NUM>, and different electrodes <NUM> are identified with an added subscript <NUM>m, where m is an integer from <NUM> to <NUM>.

While for simplicity and clarity multiplexer <NUM> is assumed to multiplex the <NUM> channels of the IRE generator to the <NUM> electrodes of catheter <NUM>, those having ordinary skill in the art will be able to adapt the description, mutatis mutandis, for multiplexers that operate on numbers of channels that are larger or smaller than <NUM>, and/or that connect to numbers of electrodes that are larger or smaller than <NUM>, and all such multiplexers are assumed to be comprised within the scope of the present disclosure.

Multiplexer <NUM> comprises <NUM> switching assemblies <NUM>, each of which acts as a single pole single throw (SPST) relay that is high rated. In the description and in the claims, the term high-rated when applied to an electrical element is assumed to mean that the element is rated to transfer high power IRE pulses, i.e., is able to transfer and operate with, without being damaged, the high voltages of at least <NUM> kV, typically up to <NUM> kV, and currents of up to <NUM> amps associated with IRE pulses.

Each switching assembly <NUM> has two terminals, a first terminal <NUM> and a second terminal <NUM>, that are switched between an open state, when the two terminals do not connect, and a closed state, when the two terminals connect. Each second terminal <NUM> is connected to a respective electrode <NUM>. For example, terminal <NUM><NUM> of switching assembly <NUM><NUM> is connected to electrode <NUM><NUM>.

In the example illustrated in <FIG>, first terminals <NUM> of groups of three assemblies <NUM> are connected to a single channel <NUM> of IRE generator <NUM>. Thus, terminals <NUM><NUM>, <NUM><NUM>, and <NUM><NUM> are connected to channel <NUM><NUM>; terminals <NUM><NUM>, <NUM><NUM>, and <NUM><NUM> are connected to channel <NUM><NUM>;. and terminals <NUM><NUM>, <NUM><NUM>, and <NUM><NUM> are connected to channel <NUM><NUM>.

Multiplexer <NUM> also comprises a controller <NUM>, which has processing capability and which is configured to operate each of assemblies <NUM>, typically according to an IRE ablation protocol that is chosen by professional <NUM>. The protocol typically selects assemblies <NUM> so as to activate electrodes connected to the assemblies, and the selection is according to the tissue being ablated. Alternatively or additionally, at least some of the functions of controller <NUM> may be performed by processor <NUM>.

Typically, during an IRE procedure, generator <NUM> is configured to use at least two channels <NUM> for a given set of IRE pulses, one as a transmit channel and one as a receive channel. Since the channels are connected to electrodes <NUM>, which are in proximity to tissue of the patient, in this configuration the IRE pulses from the generator perform bipolar ablation. In some examples, the IRE generator may be configured to use its channels only as transmit channels, and a return path for the pulses in this case is via external electrode <NUM> which is connected to the ground of generator <NUM>. In this configuration the IRE pulses perform unipolar ablation.

It will be understood that the example depicted in <FIG>, wherein three electrodes <NUM> on one spine <NUM> are multiplexed together, is but one example of electrodes that are multiplexed, and that other arrangements of three electrodes being multiplexed together will be apparent to those having ordinary skill in the art, and are comprised within the scope of the present disclosure. For example, each of the three electrodes may be on different spines, or two of the electrodes may be on one spine and the third electrode may be on a second spine. It will also be understood that combinations and sub-combinations of such arrangements are comprised within the scope of the present disclosure. For example one set of three multiplexed electrodes may be on one spine, and a second set may have two electrodes on another spine and a third electrode on yet another spine.

It will also be understood that while the example depicted in <FIG> shows ten sets of three electrodes that are multiplexed together, the scope of the present disclosure comprises sets of any plurality of two or more electrodes that are multiplexed together. For example, the thirty electrodes illustrated in <FIG> may be grouped into three sets of four electrodes, four sets of three electrodes, and three sets of two electrodes. In this case multiplexer <NUM> is configured so that the electrodes in each set are multiplexed together, by having terminals <NUM> of the respective sets connected to each other, and to a channel of the generator. , terminals <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, and <NUM><NUM> may be connected to channel <NUM><NUM>.

<FIG> is a schematic diagram illustrating the internal structure of switching assembly <NUM>. As shown in the figure first terminal <NUM> of the assembly is connected externally to a channel <NUM> of the IRE generator, and second terminal <NUM> of the assembly is connected externally to an electrode <NUM> of probe <NUM>.

The assembly comprises a first pair of double pole single throw (DPST) relays 110A, 110B, herein also termed DPST 110A and DPST 110B. DPST 110A is formed of two single pole single throw (SPST) relays 110A1, 110A2, herein just termed relays, activated by a single coil. Both relays have two contacts: first relay 110A1 comprises a first contact 110A1C1 and a second contact 110A1C2; second relay 110A2 also comprises a first contact 110A2C1 and a second contact 110A2C2. Both relays 110A1 and 110A2 of DPST 110A are activated by a coil <NUM>.

DPST 110B is substantially similar to DPST 110A, having a first relay 110B1 comprising a first contact 110B1C1 and a second contact 110B1C2, and a second relay 110B2 having a first contact 110B2C1 and a second contact 110B2C2. Both relays 110B1 and 110B2 of DPST 110B are activated by a coil <NUM>.

DPST 110A and 110B are connected to each other in parallel, so that all first contacts 110A1C1, 110A2C1, 110B1C1, and 110B2C1 are connected together and so that all second contacts 110A1C2, 110A2C2, 110B1C2, and 110B2C2 are connected together. First contacts 110A1C1, 110A2C1, 110B1C1, and 110B2C1 are also connected to first terminal <NUM> of the switching assembly. In addition, coils <NUM> and <NUM> are connected to a common power source <NUM> which operates DPST 110A and 110B. Power source <NUM> may be any convenient power source that can be operated by controller <NUM>. Herein, power source <NUM> is assumed to derive its power from a positive voltage rail and to be coupled via a switching transistor <NUM> to ground. The transistor may be activated and de-activated by controller <NUM>.

A capacitor C1 is connected in parallel with first pair of DPST relays 110A, 110B. DPST relays 110A, 110B, together their parallel capacitor C1 are herein termed a first set <NUM> of components of assembly <NUM>.

In the example illustrated relays 110A1, 110A2, 110B1, and 110B2 are all normally open. Thus, on activation of power source <NUM> all second contacts of the relays connect to the first contacts of the relays, and thus to terminal <NUM>. On deactivation of power source <NUM> terminal <NUM> disconnects from the second contacts of the relays.

The assembly also comprises a second pair of substantially similar DPST relays 130A, 130B. DPST relays 130A, 130B are also termed DPST 130A and 130B. DPST 130A has two relays each having two contacts: a first relay 130A1 comprises a first contact 130A1C1 and a second contact 130A1C2; a second relay 130A2 also comprises a first contact 130A2C1 and a second contact 130A2C2. Both relays 130A1 and 130A2 of DPST 110A are activated by a coil <NUM>.

As stated above DPST 130B is substantially similar to DPST 130A, having a first relay 130B1 comprising a first contact 130B1C1 and a second contact 130B1C2, and a second relay 130B2 having a first contact 130B2C1 and a second contact 130B2C2. Both relays 130B1 and 130B2 of DPST 130B are activated by a coil <NUM>.

As for DPST 110A and 110B, DPST 130A and 130B are connected to each other in parallel, so that all first contacts 130A1C1, 130A2C1, 130B1C1, and 130B2C1 are connected together and so that all second contacts 130A1C2, 130A2C2, 130B1C2, and 130B2C2 are connected together. Second contacts 130A1C2, 130A2C2, 130B1C2, and 130B2C2 are also connected to second terminal <NUM> of the switching assembly. In addition, coils <NUM> and <NUM> are connected to a common power source <NUM>. As for power source <NUM>, power source <NUM> is assumed to derive its power from the positive voltage rail and to be coupled via a switching transistor <NUM> to ground. Transistor <NUM> may be activated and de-activated by controller <NUM>.

Power source <NUM> delivers its power to DPST 130A and 130B via an isolator <NUM>, typically an opto-isolator. Thus, the power delivered by power source <NUM> is electrically isolated from the power delivered by power source <NUM>, so that coils <NUM> and <NUM> are electrically isolated from coils <NUM> and <NUM>. The isolation prevents the possibility of breakdown between the first and the second sets of low-rated components and protects the basket catheter <NUM> from exposure to an unexpected surge in current or voltage.

A capacitor C2 is connected in parallel with second pair of DPST relays 130A, 130B. DPST relays 130A, 130B, together their parallel capacitor C2 are herein termed a second set <NUM> of components of assembly <NUM>. C1 and C2 have equal capacitances, and in one example C1 and C2 are each <NUM> pF.

DPST 110A and 110B of first set <NUM> and DPST 130A and 130B of second set <NUM> are all rated to convey RMS currents up to <NUM> A, and to support RMS voltages up to <NUM> kV. Compared with the IRE pulses that the assembly may be conveying, having currents of up to <NUM> A and voltages of up to <NUM> kV, the relays of the first and second sets are low rated.

Relays 130A1, 130A2, 130B1, and 130B2 are all normally open. Thus, on activation of power source <NUM> all first contacts of the relays connect to the second contacts of the relays, and thus to terminal <NUM>. On deactivation of power source <NUM> terminal <NUM> disconnects from the first contacts of the relays.

First pair of DPST relays 110A, 110B are connected in series to second pair of DPST relays 130A, 130B by connections <NUM>, <NUM>. Thus contacts 110A1C2, 110A2C2, 110B1C2, and 110B2C2 of the first pair are connected to contacts 130A1C1, 130A2C1, 130B1C1, and 130B2C1 of the second pair.

In assembly <NUM> a capacitor C1 is connected in parallel with first pair of DPST relays 110A, 110B and a capacitor C2 is connected in parallel with second pair of DPST relays 130A, 130B. C1 and C2 have equal capacitances, and in one example C1 and C2 are each <NUM> pF.

In multiplexer <NUM>, each switching assembly <NUM> is activated and deactivated independently by controller <NUM>. The activation of a given assembly <NUM> comprises the controller simultaneously powering PS <NUM> and PS <NUM> of the assembly on, thereby closing the contacts of all the relays of the first pair of DPST relays 110A, 110B and closing the contacts of all the relays of the second pair of DPST relays 130A, 130B. The closing of all the relays connects first terminal <NUM> of the assembly to second terminal <NUM> of the assembly, and thus connects the channel <NUM> and the electrode <NUM> connected to the assembly.

The simultaneous closing of all the contacts, and the parallel configuration of each of the first and second pairs of DPST relays, means that the current of signals transferred through assembly <NUM> is distributed, approximately evenly, between all the SPST relays of the assembly. Thus each DPST relay in each pair may be rated to operate with a fraction, approximately <NUM>%, of the current transferred through the assembly.

The deactivation of a given assembly comprises the controller simultaneously powering source <NUM> and source <NUM> of the assembly off, thereby opening the contacts of all the relays of the first pair of DPST relays 110A, 110B and opening the contacts of all the relays of the second pair of DPST relays 130A, 130B. The opening of all the relays disconnects first terminal <NUM> of the assembly from second terminal <NUM> of the assembly, and thus disconnects the channel <NUM> connected to the assembly from the electrode <NUM> connected to the assembly.

The simultaneous opening of all the contacts, and the series connection of the first pair of relays to the second pair, causes the voltage of signals from channel <NUM> of the IRE generator to be developed between terminals <NUM> and <NUM> of the assembly <NUM>. The signals are alternating current (AC) signals, so that, absent capacitors C1 and C2, the voltage distribution across the relays is proportional to the ratio of the capacities of the open contacts of the relays. The open contact capacity of each of the relays is typically unknown, but is approximately <NUM> pF or less. The possibility of the open capacity capacitances being unequal means that the voltage across one of the pairs may exceed the voltage rating of the relays in the pair, so causing those relays to breakdown.

Connecting capacitors C1 and C2 respectively in parallel to the first and second pairs of relays, selecting the capacitance of the capacitors to be larger, by at least a factor of five, than the capacitance of the open contacts of the pair they are in parallel with, and having the capacitances to be approximately equal, ensures that the voltage across each pair of relays is a fraction, approximately <NUM>%, of the signal voltage. Selecting capacitors C1 and C2 to have capacitances significantly larger than the open contact capacitance of the relays ensures that the capacitor impedance is significantly less than the impedance of the relays. Consequently, the voltage division is determined by the capacitance ratio of C1 to C2. Thus, capacitors C1 and C2 ensure that the relays may have a voltage rating less than that of the signal voltage to prevent the relays from breaking down.

Thus each DPST relay in each pair may be rated to operate with a fraction, approximately at least <NUM>%, of the voltage developed across the assembly. Thus, for relays with a given rating, the pulses transferred by the assembly may have amplitudes significantly greater than the relay rating, typically at least <NUM>% of the rating. This is the case since the pulse voltage is developed across both pairs of relays.

The description of the example switching assembly illustrated in <FIG> assumes two pairs of DPST relays connected in series. However, it will be understood that the scope of the present disclosure includes other types and groups of relays connected in a similar configuration, so as to distribute the total current flowing through, and the overall voltage developed across, an assembly, so that the ratings of the relays in the assembly can be a fraction of the total current and overall voltage.

As a first example, at least one group of relays may comprise two or more SPST relays connected in parallel, and a capacitor may be connected in parallel with the group. As a second example, at least one group of relays may comprise combinations of different types of relays, such as an SPST relay and a DPST relay connected in parallel, with a capacitor also connected in parallel. As a third example, more than two groups of relays may be connected in series.

The description above assumes that single throw relays, i.e., SPST and DPST relays, are used in a switching assembly. It will be understood that double throw relays, such as SPDT (single pole double throw) relays and DPDT (double pole double throw) relays can be configured as single throw relays, and that this is also true of relays having more than two throws. Thus the scope of the present disclosure comprises any relays that may be configured as single throw relays.

As used herein, the terms "about" or "approximately" for any numerical values or ranges of an entity indicate a suitable dimensional tolerance that allows the entity to function for its intended purpose as described herein.

Claim 1:
A switching assembly (<NUM>) for transferring trains of pulses, comprising:
a first assembly (<NUM>) terminal and a second assembly terminal (<NUM>);
a first plurality of first relays (110A, 110B) connected in parallel, whereby the first relays have respective first contacts (110A1C1, 110A2C1, 110B1C1, 110B2C1) connected together and have respective second contacts (110A1C2, 110A2C2, 110B1C2, 110B2C2) connected together, and wherein the respective first contacts are connected to the first assembly terminal;
a first capacitor (C1) connected in parallel with the first plurality of first relays;
a second plurality of second relays (130A, 130B) connected in parallel, whereby the second relays have respective third contacts (130A1C1, 130A2C1, 130B1C1, 130B2C1) connected together and have respective fourth contacts (130A1C2, 130A2C2, 130B1C2, 130B2C2) connected together, and wherein the respective fourth contacts are connected to the second assembly terminal;
a second capacitor (C2) connected in parallel with the second plurality of second relays; and
a connection (<NUM>), having a first termination connected to the respective second contacts and a second termination connected to the respective third contacts, so that the first plurality of first relays and the second plurality of second relays are connected in series,
wherein the pulses have amplitudes of at least <NUM> kilovolts, and
whereby on activation of the first plurality of first relays and the second plurality of second relays the respective first and second contacts connect and the respective third and the fourth contacts connect, thereby connecting the first and second assembly terminals, and on deactivation of the first plurality of first relays and the second plurality of second relays the respective first and second contacts disconnect and the respective third and the fourth contacts disconnect, thereby disconnecting the first and second assembly terminals,
wherein the capacitances of the first (C1) and second (C2) capacitors are equal and larger, by at least a factor of five, than a capacitance of the contacts of the plurality of relays with which they are connected in parallel, when open.