Patent Publication Number: US-2022216894-A1

Title: Graduated frequency response non-contacting slip ring probe

Description:
TECHNICAL FIELD 
     The present invention relates to a slip ring probe, and more particularly to a slip ring having a segmented graduated frequency response probe. 
     BACKGROUND ART 
     Devices for conducting electrical signals between two members that are rotatable relative to one another are well known in the art. Such devices, generically known as rotary joints or rotary electrical interfaces, include slip-rings and twist capsules, inter alia. Slip-rings are typically used when unlimited rotation between the members is required, while twist capsules are typically used when only limited rotation between the members is required. 
     A slip ring allows the transmission of power and signals, including data, from a stationary to a rotating structure or otherwise between two structures that are rotating relative to each other. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals. A slip ring can also improve mechanical performance, simplify system operation, and eliminate damage-prone wires dangling from movable joints. Traditionally, slip ring designs only conveyed data over a very small portion of the slip ring area. 
     Conventional slip-rings typically employ sliding electrical contacts between the members. These work well in certain applications, but they have inherent weaknesses that constrain electrical performance at higher frequencies. Non-contacting slip-rings are also known in the prior art. Such rotary joint systems enable the transmission of high-frequency electrical signals between a rotor and stator without sliding electrical contacts. Such non-contacting systems include devices to recover electromagnetic energy transmitted across space between a signal source and a signal receiver. In radio frequency (“RF”) communications systems, such devices are called antennas (or antennae), and typically operate in the classical far-field electromagnetic radiation of free space. In contrast, rotary joints that utilize the electromagnetic near-field to effect electrical communications across very short distances and that recover energy from the electromagnetic near-field are termed “field probes,” or simply “probes.” 
     Devices intended to function in the reactive near-field of an electromagnetic source take different forms than their far-field counterparts, with magnetic loops, voltage probes, and resistively-loaded dipoles being known in the prior art. Near-field applications include RF ID tags and secure low-speed data transfer, which utilize magnetic induction in the near-field. As used herein, a “probe” is a structure that operates in the near-field of an electromagnetic source, and an “antenna” is reserved for those radiation structures that are intended to be predominantly far-field devices. The subject of the present disclosure includes electromagnetic field probes that operate in the near-field of non-contacting rotary joints such as slip rings. 
     Conventional antennas and near-field probes exhibit a variety of behaviors that preclude or compromise their use in non-contacting rotary joint systems when operating at greater than 1 Gbps data transmission rates. Such rotary joint systems require ultra-wideband (“UWB”) frequency response to pass the necessary frequency components of multi-gigabit digital data, as well as exhibiting high return loss and low distortion impulse response to preserve the time-domain characteristics of the signal. In addition, non-contacting rotary joints exhibit characteristics that complicate the design of antennas and field probes required to capture the energy transmitted across a rotary gap. Typically, non-contacting rotary joints exhibit field strength variations with rotation between the rotor and stator, exhibit directional behavior as the signals travel as waves in transmission lines from the signal source to the transmission line terminations, and may even be discontinuous in the near-field. High-frequency non-contacting rotary joints present a unique set of challenges for the design of near-field probes. 
     Most prior art antennas and probes are narrowband standing-wave devices that lack both the frequency response and time-domain response to accommodate the wideband energy of multi-gigabit data streams. Small near-field voltage and current probes may exhibit reasonable frequency and impulse response, but often lack a sufficient capture area for an acceptable signal-to-noise ratio. 
     U.S. Pat. No. 10,033,074 discloses non-contacting rotary joints for the transmission of electrical signals across an interface defined between two relatively-movable members that addresses some of the shortcomings of prior rotary joint solutions. U.S. Pat. No. 10,033,074 discloses a non-contacting rotary joint that broadly includes a signal source operatively arranged to provide a high-speed digital data output signal, a controlled-impedance differential transmission line having a source gap and a termination gap, a power divider operatively arranged to receive the high-speed digital data output signal from the signal source, and to supply it to the source gap of the controlled-impedance differential line, a near-field probe arranged in spaced relation to the transmission line for receiving a signal transmitted across the interface, and receiving electronics operatively arranged to receive the signal received by the probe. 
     U.S. Pat. No. 7,142,071 discloses a velocity compensated contacting ring system that includes a first dielectric material, a plurality of concentric spaced conductive rings and a first ground plane. The first dielectric material includes a first side and a second side. The plurality of concentric spaced conductive rings are located on the first side of the first dielectric material. The conductive rings include an inner ring and an outer ring. The first ground plane is located on the second side of the first dielectric material. A width of the inner ring is greater than a width of the outer ring and the widths of the inner and outer rings are selected to substantially equalize electrical lengths of the inner and outer rings. 
     U.S. Pat. No. 6,956,445 discloses a contacting probe system that includes at least one flat brush contact and a printed circuit board (PCB). The PCB includes a feedline for coupling the flat brush contact to an external interface. The flat brush contact is located on a first side of the PCB and the PCB includes a plated through eyelet that interconnects the flat brush contact to the feedline. 
     BRIEF SUMMARY 
     With parenthetical reference to corresponding parts, portions or surfaces of the disclosed embodiment, merely for the purposes of illustration and not by way of limitation, a non-contacting rotary joint ( 115 ,  215 ) for transmission of electrical signals ( 30 ) across a non-contacting interface ( 60 ) defined between two relatively-movable members is provided, comprising: a transmitter ( 16 ) configured to transmit a signal ( 30 ) across a non-contacting interface ( 60 ); a near-field probe ( 18 ) arranged in spaced relation to the transmitter and operatively arranged to receive the signal transmitted across the interface; the near-field probe having a signal capture area ( 100 ,  200 ,  300 ) for receiving the signal transmitted across the interface; the signal capture area comprising a segmented signal receiving strip ( 110 ,  130 ,  210 ,  230 ,  310 ,  330 ) having a length sized for a desired low frequency signal content of the signal and configured to receive a range of frequency signal content of the signal that includes the desired low frequency signal content of the signal, the segmented signal receiving strip comprising: a first signal receiving segment ( 119 ,  219 ,  319 ) having a first frequency response; a second signal receiving segment ( 111 A,  211 A,  311 A) having a second frequency response and electrically coupled to the first signal receiving segment; a third signal receiving segment ( 111 B,  211 B,  311 B) having a third frequency response and electrically coupled to the first signal receiving segment; the second frequency response of the second signal receiving segment being less than the first frequency response of the first signal receiving segment; and the third frequency response of the third signal receiving segment being less than the first frequency response of the first signal receiving segment; and receiving electronics ( 28 ) operatively arranged to receive the range of frequency signal content received by the segmented signal receiving strip via the first signal receiving segment ( 119 ,  219 ,  319 ). 
     The first signal receiving segment may have a first length; the second signal receiving segment may have a second length greater than the first length; and the third signal receiving segment may have a third length greater than the first length. The segmented signal receiving strip may comprise: a first dissipation element ( 121 A,  221 A,  314 A) positioned between the first signal receiving segment and the second signal receiving segment and configured to isolate the first signal receiving segment from the second signal receiving segment; and a second dissipation element ( 121 B,  221 B,  314 B) positioned between the first signal receiving segment and the third signal receiving segment and configured to isolate the first signal receiving segment from the third signal receiving segment. 
     The second signal receiving segment ( 311 A) may comprise an electrically coupled resistor (R) and capacitor (C) arranged to provide a signal filter ( 321 A) and the third signal receiving segment ( 311 B) may comprise an electrically coupled resistor and capacitor arranged to provide a signal filter ( 321 B). The first signal receiving segment ( 319 ) may have a first length; the second signal receiving segment ( 311 A) may have a second length equal to the first length; and the third signal receiving segment ( 311 B) may have a third length equal to the first length. The segmented signal receiving strip ( 310 ) may comprise: a first dissipation element ( 314 A) positioned between the first signal receiving segment ( 319 ) and the second signal receiving segment ( 311 A) and configured to isolate the first signal receiving segment from the second signal receiving segment; and a second dissipation element ( 314 B) positioned between the first signal receiving segment ( 319 ) and the third signal receiving segment ( 311 B) and configured to isolate the first signal receiving segment from the third signal receiving segment. 
     The first signal receiving segment, the second signal receiving element and the third signal receiving element may each comprise copper. The first dissipation element and the second dissipation element may each comprise a resistor. The first signal receiving segment ( 119 ,  219 ,  319 ) may comprise a center tap ( 61 ) communicating with the receiving electronics ( 28 ). 
     The first frequency response of the first signal receiving segment may correspond to a first frequency subrange of the range of frequency signal content of the signal; and the second frequency response of the second signal receiving segment may correspond to a second frequency subrange of the range of frequency signal content of the signal; and the first frequency subrange may be greater than the second frequency subrange. 
     The signal transmitted across the non-contacting interface by the transmitter may be a high-speed digital data output signal. The transmitter may comprise a signal source ( 20 ) operatively arranged to provide a high speed digital data output signal, a controlled-impedance differential transmission line ( 162 ) having a source gap ( 23 ) and a termination gap ( 24 ), a power divider ( 21 ) operatively arranged to receive the high-speed digital data output signal from the signal source, and to supply the high-speed digital data output signal from the signal source to the source gap of the controlled-impedance differential transmission line; and the near-field probe may be arranged in spaced relation to the controlled-impedance differential transmission line and may be operatively arranged to receive the signal transmitted across the non-contacting interface by the transmitter. 
     The segmented signal receiving strip may comprise at least two additional signal receiving segments ( 112 A,  112 B,  113 A,  113 B,  311 ), with each of the additional signal receiving segments having a frequency response and being electrically coupled to the first signal receiving segment; and wherein the frequency response of each additional signal receiving segment decreases the further the additional signal receiving segment is from the first signal receiving segment. The segmented signal receiving strip may comprise at least one dissipation element ( 121 A,  122 A,  123 A,  121 B,  122 B,  123 B,  221 A,  222 A,  223 A,  221 B,  222 B,  223 B,  314 A,  314 B,  314 ) positioned between each of the second signal receiving segment, the third signal receiving segment, and the additional signal receiving segments, and the dissipation elements may be configured to isolate the respective signal receiving segments from each other. 
     The length of each additional signal receiving segment ( 112 A,  112 B,  113 A,  113 B) may increase the further the additional signal receiving segment is from the first signal receiving segment ( 119 ,  219 ). The second signal receiving segment ( 311 A), the third signal receiving segment ( 311 B), and the additional signal receiving segments ( 311 ) may comprise an electrically coupled resistor (R) and capacitor (C) arranged to provide a signal filter ( 321 ). 
     The signal capture area may comprise a second segmented signal receiving strip ( 130 ,  230 ,  330 ) orientated parallel to the first segmented signal receiving strip ( 110 ,  210 ,  310 ); the second segmented signal receiving strip comprising: a first signal receiving segment ( 139 ,  239 ,  339 ) having a first frequency response; a second signal receiving segment ( 131 A,  231 A,  331 A) having a second frequency response and electrically coupled to the first signal receiving segment; a third signal receiving segment ( 131 B,  231 B,  331 B) having a third frequency response and electrically coupled to the first signal receiving segment; the second frequency response of the second signal receiving segment being less than the first frequency response of the first signal receiving segment; and the third frequency response of the third signal receiving segment being less than the first frequency response of the first signal receiving segment, and the receiving electronics ( 28 ) may be operatively arranged to receive signal content received by the second segmented signal receiving strip ( 130 ,  230 ,  330 ) via the first signal receiving segment ( 139 ,  239 ,  339 ) of the second segmented signal receiving strip ( 130 ,  230 ,  330 ). 
     In another aspect, a probe is provided having a length sized for a desired low frequency signal content, the probe comprising: a plurality of signal receiving strips ( 110 ,  130 ,  210 ,  230 ,  310 ,  330 ) configured to receive low and high frequency signal content, each of the plurality of signal receiving strips comprising: a center tap ( 61 ,  62 ,  119 ,  139 ,  219 ,  239 ,  319 ,  339 ) connected to a processor ( 28 ); a first signal receiving segment ( 111 A,  211 A,  311 A) including a length for receiving a high frequency signal; a second signal receiving segment ( 111 B,  211 B,  311 B) including a length for receiving the high frequency signal; a first dissipation element ( 121 A,  221 A,  314 A) positioned between the center tap and the first signal receiving segment to isolate the center tap and the first signal receiving segment; and a second dissipation element ( 121 B,  221 B,  314 B) positioned between the center tap and the second signal receiving segment to isolate the center tap and the second signal receiving segment. 
     The plurality of signal receiving strips may further comprise: at least one first additional signal receiving segment ( 112 A,  113 A,  212 A,  213 A) including a length for receiving the high frequency signal, the at least one first additional signal receiving segment being electrically coupled to the first signal receiving segment; and at least one second additional signal receiving segment ( 112 B,  113 B,  212 B,  213 B) including a length for receiving the high frequency signal, the at least one second additional signal receiving segment being electrically coupled to the second signal receiving segment. The plurality of signal receiving strips may further comprise a plurality of dissipation elements ( 122 A,  123 A,  222 A,  223 A) positioned between the signal receiving segments to isolate the center tap and the signal receiving segments. The length of each respective signal receiving segment ( 112 A,  113 A,  212 A,  213 A,  112 B,  113 B,  212 B,  213 B) may increase the further the signal receiving segment is from the center tap. Each of the signal receiving segments may correspond to a range of frequency signal content. The first signal receiving segment and the second signal receiving segment may comprise copper conductive material. The first signal receiving segment ( 311 A) and the second signal receiving segment ( 311 B) may be electrically coupled to a resistor (R) and a capacitor (C) filter ( 321 ). The first signal receiving segment and the second receiving segment may be 0.11 inches by 0.075 inches. 
     In another aspect, a method of receiving low and high frequency signal content is provided, the method comprising: providing a probe including a length sized for a desired low frequency signal content, the probe comprising: a plurality of signal receiving strips configured to receive low and high frequency signal content, each of the plurality of signal receiving strips comprising: a center tap connected to a processor; a first signal receiving segment including a length for receiving a high frequency signal; a second signal receiving segment including a length for receiving the high frequency signal; a first dissipation element positioned between the center tap and the first signal receiving segment to isolate the center tap and the first signal receiving segment; and a second dissipation element positioned between the center tap and the second signal receiving segment to isolate the center tap and the second signal receiving segment; and receiving, by the first signal receiving segment and the second signal receiving segment, the low and high frequency signal content. 
     Each of the plurality of signal receiving strips may further comprise: at least one first additional signal receiving segment including a length for receiving the high frequency signal, the at least one first additional signal receiving segment being electrically coupled to the first signal receiving segment; and at least one second additional signal receiving segment including a length for receiving the high frequency signal, the at least one second additional signal receiving segment being electrically coupled to the second signal receiving segment. Each of the plurality of signal receiving strips may further comprise a plurality of dissipation elements positioned between the signal receiving segments to isolate the center tap and the signal receiving segments. The length of each respective signal receiving segment may increase the further the signal receiving segment is from the center tap. Each of the signal receiving segments may correspond to a range of frequency signal content. The first signal receiving segment and the second signal receiving segment may be made of a copper conductive material. The first signal receiving segment and the second signal receiving segment may be electrically coupled to a resistor and a capacitor. The first signal receiving segment and the second receiving segment may be 0.11 inches by 0.075 inches. 
     In another aspect, a slip ring probe ( 100 ,  200 ,  300 ) is provided comprising a plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ) arranged in spaced relation to a transmitter ( 162 ) of a slip ring ( 115 ,  215 ) for receiving a signal ( 30 ) transmitted across an interface ( 60 ) of the slip ring ( 115 ,  215 ), each of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ) having a center-tap ( 61 ,  62 ,  113 ,  123 ,  219 ,  239 ,  319 ,  330 ) and a length ( 132 ,  252 ) capable of providing a coupling capacitance across the whole length of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ) between the transmitter ( 162 ) and the probe ( 100 ,  200 ,  300 ) of the slip ring ( 115 ,  215 ). 
     The probe may be a graduated frequency response probe ( 100 ,  200 ,  300 ). Each of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ) may comprise a variable loss tangent ( 131 ,  251 ) across the respective lengths ( 132 ,  252 ) of each of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ). The variable loss tangent ( 131 ,  251 ) across the respective lengths ( 132 ,  252 ) of each of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ) may increase towards outer regions of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ). The variable loss tangent ( 131 ,  251 ) may be minimal at the center-tap ( 61 ,  62 ,  113 ,  123 ,  219 ,  239 ,  319 ,  339 ) of each of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ). The respective lengths ( 132 ,  252 ) of each of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ) may be selected based on a frequency of the signal ( 30 ). Each of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ) may comprise a signal capture area. The signal capture area may correspond to a coupling capacitance, the larger the signal capture area the larger the coupling capacitance. Each of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ) may comprise a plurality of discontinuous attenuation filters ( 111 A,  111 B,  112 A,  112 B,  113 A,  113 B,  211 A,  211 B,  212 A,  212 B,  213 A,  213 B). Lengths of each of the plurality of discontinuous attenuation filters may increase away from the center-tap ( 61 ,  62 ,  113 ,  123 ,  219 ,  239 ) of the probe ( 100 ,  200 ). Lengths of each of the plurality of discontinuous attenuation filters ( 111 A,  111 B,  112 A,  112 B,  113 A,  113 B,  211 A,  211 B,  212 A,  212 B,  213 A,  213 B) may correspond to a frequency bandwidth. The probe ( 100 ,  200 ,  300 ) may comprise resistors ( 121 A,  122 A,  123 A,  121 B,  122 B,  123 B,  221 A,  222 A,  223 A,  221 B,  222 B,  223 B,  314 A,  314 B,  314 ) arranged between adjacent attenuation filters of the plurality of discontinuous attenuation filters. The probe ( 100 ,  200 ) may further comprise pads ( 115 A,  115 B,  135 A,  135 B,  215 A,  215 B,  235 A,  235 B) at ends of each of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ) to attenuate frequencies. The probe ( 100 ,  200 ,  300 ) may be a straight probe or a curved probe. The length ( 132 ,  252 ) of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ) may be proportional to a wavelength of the electrical signals ( 30 ) across the interface ( 60 ) of the slip ring ( 115 ,  215 ), wherein a lower frequency of the signal ( 30 ) corresponds to a longer length of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ) to increase a coupling capacitance of the probe ( 100 ,  200 ). The receiver may be configured to receive low frequencies of the signal across a majority of the length ( 132 ,  252 ) of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ) and high frequencies in an area proximate to the center-tap ( 113 ,  123 ,  219 ,  239 ,  319 ,  339 ) of the plurality of conductive strips ( 110 ,  120 ,  210 ,  230 ,  310 ,  330 ). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a first embodiment of an improved non-contacting rotary joint, and in particular shows a non-contacting rotary joint (“NCRJ”) system diagram for transmission of a transmitter (TX) signal from a DATA TRANSMIT side to a DATA RECEIVE side. Conventional positive (+) and negative (−) symbols are shown to denote differential signaling and transmission lines. 
         FIG. 2  is a top plan view of the circular platter circuit board transmitter of the slip ring shown in  FIG. 1 , with transmit tracks in a circular configuration. 
         FIG. 3  is a top plan view of the circular platter circuit board receiver and probe of the slip ring shown in  FIG. 1 , with conductive strips in a circular-curved platter configuration. 
         FIG. 4  is an enlarged top plan view of a pair of the conductive strips of the probe shown in  FIG. 3 . 
         FIG. 5  is a perspective view of a second embodiment of a non-contact slip ring transmitter and receiver, with transmit tracks and conductive strips in a linear configuration. 
         FIG. 6  is an enlarged plan view of the conductive strips of the probe shown in  FIG. 5 , with a corresponding loss tangent graph. 
         FIG. 7  is a view of received eye diagrams for the slip ring probe of  FIG. 4  at different frequencies. 
         FIG. 8  is an enlarged top plan view of an alternative embodiment of the probe shown in  FIG. 4 . 
         FIG. 9  is a schematic circuit diagram of the 10-segment probe shown in  FIG. 8 . 
         FIG. 10  is an enlarged top plan view of a slip ring probe with an ideal corresponding loss tangent graph. 
         FIGS. 11A and 11B  illustrate signal conveyance of the probe for low frequency content and high frequency content, respectively. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     At the outset, it should be clearly understood that like reference numerals are intended to identify the same structural elements, portions or surfaces consistently throughout the several drawing figures, as such elements, portions or surfaces may be further described or explained by the entire written specification, of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this invention. As used in the following description, the terms “horizontal”, “vertical”, “left”, “right”, “up” and “down”, as well as adjectival and adverbial derivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly”, etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate. 
     Non-contact slip ring probe structures used for data transfer respond differently at different data rates. Probes designed to perform at a particular data transfer rate and protocol do not perform well for other data rates and protocols. Additionally, even optimized probes present waveform distortion as the probe moves along a rotary or linear data source track, and especially at locations where the tracks are discontinuous. This results in reduced received signal quality at a detector and an increase in signal (bit) error rates (BER). 
     Referring now to the drawings, and more particularly to  FIGS. 1-4  thereof, a slip ring is provided, of which a first embodiment is generally indicated at  115 . Slip ring  115  is a non-contacting rotary joint for the transmission of high-speed data signals across an intervening interface between two relatively movable members, without the use of sliding electrical contacts in the signal path. The joint includes a split differential microstrip transmission line driven by a signal source through a power divider and resistively terminated at a far end, and a receiver that includes a planar differential field probe that senses the near-field of the transmitter differential microstrip and that delivers recovered signal energy to an electronic receiver for detection. This high-speed non-contacting rotary joint may be implemented with printed circuit board (“PCB”) technology, and may support multi-gigabit data transmission rates, with frequency-domain bandwidths. 
     As shown in  FIG. 1 , signal source  20  serves to deliver a high-speed digital data signal to power divider  21  (which can be active or passive), where the signal transits through source gap  23  and into controlled-impedance differential transmission line  162 . The signal then propagates as a transverse electromagnetic wave (“TEM”) on the differential transmission line ring structure of line  162  of transmitter circuit board  16  to where the signal is terminated at far-end termination gap  24  by wideband termination techniques  25 . The TEM signal traveling on ring transmission line  162  is sampled in the near-field by ultra-wideband planar segmented GFR near-field probe signal capture area  100  of receiver circuit board  18 , which is suspended at some distance over transmitter  16  and ring structure  162  to allow free rotation of the rotary joint, without physical contact. Thus, as shown, probe signal capture area  100  is suspended at a distance over controlled-impedance differential transmission line  162 . The signal  30  recovered across air gap  60  by near-field probe  100  is delivered to receiver electronics  28  of receiver  18 , where the signal can be detected, amplified, and its data recovered. 
     Data source driver  20  may be any of a number of technologies capable of the desired data rate, including a current-mode logic (“CML”), a field-programmable gate array (“FPGA”), a low-voltage differential signaling (“LVDS”) device, and other discrete devices. The data signal is divided into two equal-amplitude phase-inverted signals for feeding the differential ring system, a function that can be done by passive resistive dividers or by active techniques (e.g., CML fan-out buffer). Power divider  21  can be implemented as a discrete assembly or, as in this embodiment, incorporated onto PCB structures of transmitter  16  with discrete or integrated components, or embedded passive components implemented in planar PCB geometry. The technology employed to implement the power divider imposes a constraint to high frequency operation of the data channel due to parasitic reactances of the component package introducing signal reflections that become progressively more pronounced at higher frequencies. The driving electronics, power divider, and transmission line terminations can be implemented using a variety of technologies (e.g., thru-hole or surface mount components on PCB structures, integrated components, or embedded passive components implemented in planar PCB geometry), with high frequency performance capabilities determined by decreasing parasitic reactances. 
     The ring structure  162  of transmitter  16  in non-contacting rotary joint  115  is a controlled-impedance differential transmission line that is non-resonant, discontinuous, and typically implemented in microstrip multilayer printed circuit board technology. The nature of ring transmission line  162  is such that the bulk of the signal energy is contained in the near-field of the conductors. Energy radiated from the structure tends to cancel in the far-field, an aid to electromagnetic interference (EMI) suppression. The propagating signal on the ring system has directional properties, 
     Near-field probe  100  of receiver  18  is designed to have an ultra-wideband near-field response, while meeting the specific requirements of the high-speed data transmission on ring transmission lines  162 . Receiver  18  is shown as broadly including a PCB having on one side multiple pairs of parallel segmented conductive strips  100 . Each pair of segmented conductive strips  100  comprises first segmented conductive strip  110  and second segmented conductive strip  130 . First conductive strip  110  and second conductive strip  130  each have a length corresponding to the desired low frequency domain of the receiver and are configured to receive signals from transmitter  160  across air gap  60  of rotary joint  115 . 
     First conductive strip  110  comprises center conductive pad  119 , conductive pads  111 A,  112 A and  113 A extending towards end  116  from center pad  119 , end capacitive element  115 A defining end  116 , conductive pads  111 B,  112 B and  113 B extending towards end  118  from center pad  119 , and end capacitive element  115 B defining end  118 . Center conductive pad  119  has a center via or tap  61  connecting to the first stage amplifier of signal receiving electronics  28  of receiver board  18 . Each of center conductive pad  119 , conductive pads  111 A,  112 A and  113 A, end capacitive element  115 A, conductive pads  111 B,  112 B and  113 B, and end capacitive element  115 B are separated from each other by resistors  121 A,  121 B,  122 A,  122 B,  123 A,  123 B,  124 A and  124 B, respectively. 
     Similarly, second conductive strip  130  extends from first end  136  to second end  138 . Second conductive strip  130  comprises center conductive pad  139 , conductive pads  131 A,  132 A and  133 A extending towards end  136  from center pad  139 , end capacitive element  135 A defining end  136 , conductive pads  131 B,  132 B and  133 B extending towards end  138  from center pad  139 , and end capacitive element  135 B defining end  138 . Center conductive pad  139  has a center via or tap  62  connecting to the first stage amplifier of signal receiving electronics  28  of receiver board  18 . Each of center conductive pad  139 , conductive pads  131 A,  132 A and  133 A, end capacitive element  135 A, conductive pads  131 B,  132 B and  133 B, and end capacitive element  135 B are separated from each other by resistors  141 A,  141 B,  142 A,  142 B,  143 A,  143 B,  144 A and  144 B, respectively. 
     Thus, first conductive strip  110  of probe  100  is not continuous and instead is formed from a plurality of segments  119 ,  111 A,  111 B,  112 A,  112 B,  113 A and  113 B, a plurality of resistors  121 A,  121 B,  122 A,  122 B,  123 A,  123 B,  124 A and  124 B, a first capacitive end  115 A, and a second capacitive end  115 B. As shown in  FIG. 4  and as further described below with respect to embodiment  200 , in this embodiment segments  111 A and  111 B,  112 A and  112 B, and  113 A and  113 B, vary in length, with the segment length increasing with the increase in distance from center segment  119  and center via  61 . Thus, center segment  119  has a center length, segments  111 A and  111 B have a first length greater than the center length of center segment  119 , segments  112 A and  112 B have a second length greater than the first length of segments  111 A and  111 B, and segments  113 A and  113 B have a third length greater than the second length of segments  112 A and  112 B. Because of this difference in length, conductive segments  111 A and  111 B,  112 A and  112 B, and  113 A and  113 B have different frequency responses as a function of their position relative to center segment  119 . Such conductive segments have a frequency response that decreases as a function of their distance from or location relative to center segment, such that segments  113 A and  113 B have the lowest response to high frequency signal components, and center segment  119  has the highest response to high frequency signal components. The overall strip length, individual segment lengths, and the number of segments of conductive strip  110  may be varied depending on the frequency range desired for receiver  18 . 
     As shown in  FIG. 4  and as further described below with respect to embodiment  200 , in this embodiment resistors  121 A,  121 B,  122 A,  122 B,  123 A,  123 B,  124 A and  124 B also vary in length, with the resistor length increasing with the increase in distance from center tab  119  and center via  62 . Thus, resistors  121 A and  121 B between center segment  119  and segments  111 A and  111 B, respectively, have a first length, resistors  122 A and  122 B between segments  111 A and  111 B and segments  112 A and  112 B, respectively, have a second length greater than the first length of resistors  121 A and  121 B, and resistors  123 A and  123 B between segments  112 A and  112 B and segments  113 A and  113 B, respectively, have a third length greater than the second length of resistors  122 A and  122 B. Resistors  124 A and  124 B between segments  113 A and  113 B and the small end capacitance of ends  115 A and  115 B, respectively, help dissipate high frequency signal components propagated towards ends  116  and  118  of conductive strip  110 . Resistors  121 A,  121 B,  122 A,  122 B,  123 A, and  123 B are configured to have values that are set to attenuate the frequencies of interest at their locations along strip  110 . In this embodiment, resistors  123 A and  123 B are configured such that low frequency signal components can pass from conductive segments  113 A and  113 B to conductive segments  112 A and  112 B, respectively, while higher frequency signal components do not. In turn, dual resistors  122 A and  122 B are configured such that medium high frequency signal components can pass from conductive segments  112 A and  112 B to conductive segments  111 A and  111 B, respectively, while higher frequency signal components do not. In turn, resistors  121 A and  121 B are configured such that medium frequency signal components can pass from conductive segments  111 A and  111 B to conductive segment  119 , respectively, while higher frequency signal components do not. The resistor values, individual resistor lengths, and the number of resistors may be varied depending on the frequency range and attenuation desired for receiver  18 . 
     Similarly, second conductive strip  130  of probe  100  is not continuous and instead is formed from a plurality of segments  139 ,  131 A,  131 B,  132 A,  132 B,  133 A and  133 B, a plurality of resistors  141 A,  141 B,  142 A,  142 B,  143 A,  143 B,  144 A and  144 B, a first capacitive end  135 A, and a second capacitive end  135 B. As shown in  FIG. 4  and as further described below with respect to embodiment  200 , in this embodiment segments  131 A and  131 B,  132 A and  132 B, and  133 A and  133 B, vary in length, with the segment length increasing with the increase in distance from center segment  139  and center via  62 . Thus, center segment  139  has a center length, segments  131 A and  131 B have a first length greater than the center length of center segment  139 , segments  132 A and  132 B have a second length greater than the first length of segments  131 A and  131 B, and segments  133 A and  133 B have a third length greater than the second length of segments  132 A and  132 B. Because of this difference in length, conductive segments  131 A and  131 B,  132 A and  132 B, and  133 A and  133 B have different frequency responses as a function of their position relative to center segment  139 . Such conductive segments have a frequency response that decreases as a function of their distance from or location relative to center segment, such that segments  133 A and  133 B have the lowest response to high frequency signal components, and center segment  139  has the highest response to high frequency signal components. The overall strip length, individual segment lengths, and the number of segments of conductive strip  130  may be varied depending on the frequency range desired for receiver  18 . 
     As shown in  FIG. 4  and as further described below with respect to embodiment  200 , in this embodiment resistors  141 A,  141 B,  142 A,  142 B,  143 A,  143 B,  144 A and  144 B also vary in length, with the resistor length increasing with the increase in distance from center segment  139  and center via  62 . Thus, resistors  141  and  141 B between center segment  139  and segments  131 A and  131 B, respectively, have a first length, resistors  142 A and  142 B between segments  131 A and  131 B and segments  132 A and  132 B, respectively, have a second length greater than the first length of resistors  141 A and  141 B, and resistors  143 A and  143 B between segments  132 A and  132 B and segments  133 A and  133 B, respectively, have a third length greater than the second length of resistors  142 A and  142 B. Resistors  144 A and  144 B between segments  133 A and  133 B and the small end capacitance of ends  135 A and  135 B, respectively, help dissipate high frequency signal components propagated towards ends  136  and  138  of conductive strip  130 . Resistors  141 A,  141 B,  142 A,  142 B,  143 A, and  143 B are configured to have values that are set to attenuate the frequencies of interest at their locations along strip  130 . In this embodiment, resistors  143 A and  143 B are configured such that low frequency signal components can pass from conductive segments  133 A and  133 B to conductive segments  132 A and  132 B, respectively, while higher frequency signal components do not. In turn, dual resistors  142 A and  142 B are configured such that medium high frequency signal components can pass from conductive segments  132 A and  132 B to conductive segments  131 A and  131 B, respectively, while higher frequency signal components do not. In turn, resistors  141 A and  141 B are configured such that medium frequency signal components can pass from conductive segments  131 A and  131 B to conductive segment  139 , respectively, while higher frequency signal components do not. The resistor values, individual resistor lengths, and the number of resistors may be varied depending on the frequency range and attenuation desired for receiver  18   
     Thus, slip ring  115  comprises a longer transmit strip  162  of PCB material and a shorter differential conductive receiver probe signal capture area  100 . The transmit strip and the receiver probe  100  are placed in proximity and signals placed on transmit strip  162  are typically capacitively coupled across air gap  60  to receiver probe  100 . The signals are amplified by first stage amplifier  50  and sent to communication receiver circuit  28  Traces are typically organized as differential tracks to reduce EMC effects, but single tracks are envisioned as well. 
     As shown in  FIG. 2 , transmitter  16  has a circular flat platter configuration with  4  channels  162  orientated about a center. As shown in  FIG. 3 , receiver  18  is likewise configured as a circular platter circuit board having four probe channels  100  with curved conductive strips  110 ,  130  orientated about a center. Transmitter  16  and receiver  118  are coaxial such that the receive probe  100  for each channel is radially aligned across air gap  60  from the corresponding channel transmit tracks  162  of slip ring  115 . Signals that propagate about the transmit tracks  162  are capacitively coupled across air gap  60  to the receive probe  100 , where the signals are amplified and conveyed to the communication receiver circuit. 
     While transmit tracks  162  and receiver probe  100  are curved on circular platters (as shown in  FIG. 1-4 ), in the alternative embodiment  200  shown in  FIGS. 5 and 6 , such transmit tracks and receiver probe are constructed as straight parallel tracks. Referring now to  FIGS. 5 and 6 , a second embodiment of an improved slip ring probe is generally indicated at  200 . Other than its straight configuration, probe  200  is similar in construction and operation as curved probe  100 . 
     As shown in  FIG. 5 , slip ring  215  has a longer transmit strip of PCB material  260  and a shorter differential conductive receiver probe  200 . The transmit strip  260  and receiver probe  200  are placed in proximity and signals placed on the transmit strip are typically capacitively coupled across air gap  60  to receiver probe  200 . Thus, receive probe  200  is placed above or adjacent to transmit tracks  262  of slip ring  215  as shown in  FIG. 5 . Signals that propagate down transmit tracks  262  are capacitively coupled across air gap  60  to receive probe  200 , where the signals are amplified via amplifier  50  and conveyed to the communication receiver circuit. 
     As shown in  FIG. 6 , probe  200  is shown as broadly including first conductive strip  210  and a second conductive strip  230 . First conductive strip  210  of the slip ring  200  includes a plurality of segments  219 ,  211 A,  211 B,  212 A,  212 B,  213 A and  213 B, a plurality of resistors  221 A,  221 B,  222 A,  222 B,  223 A,  223 B, and  224 A, a first end  215 A, and a second end  215 B. The plurality of segments  219 ,  211 A,  211 B,  212 A,  212 B,  213 A and  213 B vary in length as shown in  FIG. 6  and in the same manner as described about with respect to probe  100 . Segments  211 A and  211 B,  212 A and  212 B, and  213 A and  213 B increase in length from center segment  219  to first end  215 A and the second end  215 B, respectively, of first conductive strip  210 . 
     The first end  215 A and second end  215 B of first conductive strip  210  each include a first copper pad over a second copper pad that form a small capacitance to ground in series with adjacent resistors  224 A and  224 B, respectively, which is designed to attenuate the frequencies of interest at that particular location. These pads are shown as square having a width larger than the width of the plurality of segments  219 ,  211 A,  211 B,  212 A,  212 B,  213 A and  213 B. However, other shapes and widths, including with respect to the plurality of segments  219 ,  211 A,  211 B,  212 A,  212 B,  213 A and  213 B, are contemplated as suitable for the intended purpose as would be understood by a person of ordinary skill in the art. 
     Again, the plurality of resistors  221 A,  221 B,  222 A,  222 B,  223 A,  223 B,  224 A and  224 B are configured to be positioned between adjacent segments of the plurality of segments  219 ,  211 A,  211 B,  212 A,  212 B,  213 A and  213 B, and end pads  215 A and  215 B of slip ring probe  200 . The value of the plurality of resistors of first conductive strip  210  are selected to attenuate the frequencies of interest at a particular location. This embodiment also includes two resistors between center segment  219  and adjacent segments  211 A and  211 B of the plurality of segments, but only one resistor or more than two resistors is contemplated by this disclosure. Furthermore, the length of the plurality of resistors varies depending on the size of the adjacent segments of the plurality of segments of first conductive strip  210 . 
     Second conductive strip  220  of the slip ring  200  includes a plurality of segments  239 ,  231 A,  231 B,  232 A,  232 B,  233 A and  233 B, a plurality of resistors  241 A,  241 B,  242 A,  242 B,  243 A,  243 B, and  244 A, a first end  235 A, and a second end  235 B. The plurality of segments  239 ,  231 A,  231 B,  232 A,  232 B,  233 A and  233 B vary in length as shown in  FIG. 6  and in the same manner as described about with respect to probe  100 . Segments  231 A and  231 B,  232 A and  232 B, and  233 A and  234 B increase in length from center segment  239  to first end  235 A and the second end  235 B, respectively, of second conductive strip  230 . 
     The first end  235 A and second end  235 B of first conductive strip  230  each include a first copper pad over a second copper pad that form a small capacitance to ground in series with adjacent resistors  244 A and  244 B, respectively, which is designed to attenuate the frequencies of interest at that particular location. These pads are shown as square having a width larger than the width of the plurality of segments  239 ,  231 A,  231 B,  232 A,  232 B,  233 A and  233 B. However, other shapes and widths, including with respect to the plurality of segments  239 ,  231 A,  231 B,  232 A,  232 B,  233 A and  233 B, are contemplated as suitable for their intended purpose as would be understood by a person of ordinary skill in the art. 
     Again, the plurality of resistors  241 A,  241 B,  242 A,  242 B,  243 A,  243 B,  244 A and  244 B are configured to be positioned between adjacent segments of the plurality of segments  239 ,  231 A,  231 B,  232 A,  232 B,  233 A and  233 B, and end pads  235 A and  235 B of slip ring probe  200 . The value of the plurality of resistors of second conductive strip  230  is selected to attenuate the frequencies of interest at a particular location. This embodiment also includes two resistors between center segment  219  and adjacent segments  231 A and  231 B of the plurality of segments, but only one resistor or more than two resistors is contemplated by this disclosure. Furthermore, the length of the plurality of resistors varies depending on the size of the adjacent segments of the plurality of segments of second conductive strip  230 . 
     The outer extremities of slip ring probe  200  (e.g., the first end  215 A and the second end  215 B of the first conductive strip  210  and the first end  235 A and the second end  235 B of the second conductive strip  230 ) have greater high-frequency loss. The center portion of slip ring probe  200 , nearest center segment  219  and center segment  239  and center via  61  and center via  62  of strips  210  and  230 , respectively, has almost no loss at high frequencies. This keeps the highest frequencies feeding amplifier  50  adjacent center via  61  and via  62  of segments  219  and  239  of the slip ring probe  200 , respectively, constraining wavelengths (frequencies) to a length of conductive material (e.g., the plurality of segments of the first conductive strip  210  and the plurality of segments of the second conductive strip  230 ) short enough so as to not form a transmission line. 
     As frequencies of interest decrease, and wavelengths increase, longer and longer lengths of the first conductive strip  210  and second conductive strip  230  of slip ring probe  200  are utilized. This greater signal capture area of slip ring probe  200  used at lower frequencies increases the coupling capacitance to the transmit traces  262 . This is beneficial because higher frequencies couple well with smaller capacitances. To achieve the same coupling at lower frequencies, a larger capacitance is required (assuming impedances are flat across the slip ring probe  200 ). 
     The first conductive strip  210  and the second conductive strip  230  of the slip ring probe  200  may be formed of PCB copper strips or any other conductive material suitable for the intended purpose and understood by a person of ordinary skill in the art. In this embodiment, the plurality of segments  219 ,  211 A,  211 B,  212 A,  212 B,  213 A and  213 B of first conductive strip  210  and the plurality of segments  239 ,  231 A,  231 B,  232 A,  232 B,  233 A and  233 B of second conductive strip  230  are copper tabs whose length corresponds to frequency bandwidths and desired frequency response at that location of the slip ring probe  200  as shown in  FIG. 6 .  FIG. 6  illustrates a loss tangent graph  250  with a loss tangent axis  251  and a probe length axis  252 .  FIG. 6  further illustrates the various degrading frequency responses  253 A,  253 B,  254 A,  254 B,  255 A and  255 B along the length of slip ring probe  200 . For example, segments  211 A and  231 A of first conductive strip  210  and second conductive strip  230 , respectively, correspond to loss tangent values  253 A and  253 B, respectively. Segments  212 A and  232 A of first conductive strip  210  and second conductive strip  230 , respectively, correspond to loss tangent values  254 A and  254 B, respectively. Segments  213 A and  233 A of first conductive strip  210  and second conductive strip  230 , respectively, correspond to loss tangent values  255 A and  255 B, respectively. Segments  219  and  239  of first conductive strip  210  and second conductive strip  230 , respectively, correspond to loss tangent value  256 . 
     As illustrated in  FIG. 11A , at low frequencies, slip ring probe  200  uses a majority of the length of the first conductive strip  210  and the second conductive strip  230  to convey information to amplifier  50 . As illustrated in  FIG. 11B , at higher frequencies, center receiver segments  119  and  139 , as well as other subject interior conductive segments, such as segments  211 A,  211 B and  231 A,  231 B for example, of first conductive strip  210  and second conductive strip  230  of slip ring probe  200  convey signals to amplifier  50 . Higher frequencies towards first ends  215 A and  235 A and second ends  215 B and  235 B of first conductive strip  210  and second conductive strip  230  are dissipated and absorbed as heat. As such, there is no opportunity of propagation to the amplifier pickup area  50 . 
     Referring to  FIG. 7 , various eye diagrams of bit sequences PRBS-7 and PRBS-31 are illustrated for slip ring probe  100 . The test results of slip ring probe  100  correspond to low-end frequency content in a frequency range between 500 Mbps and 10 Gbps. 
     There may be locations across transmit track  262  of the slip ring where the signal performs well, while at other locations along transmit track  262  the signal breaks down. These fluctuations are dependent on the base transmit frequency and resonant structures created as the receive probe  200  changes position relative to transmit tracks  262  of the slip ring, including positions where the tracks are discontinuous (e.g., over air gap  60 ). 
     For example, to convey a signal such as an HD video signal across a slip ring communications channel, a flat channel bandwidth between 33.7 MHz and 8910 MHz is utilized, all without permutations to sinewave amplitudes or phase. These frequencies also correspond to waveform period lengths of roughly 25 mm to 7 meters (estimated at 75% of the speed of light in actual PCB material). These wavelengths are conveyed to the receiver probe  200  via capacitive and/or inductive coupling simultaneously. 
     The longer wavelengths (lower frequencies) impinge energy into the receiving probe  200  capacitively, with no transmission line effects (e.g., electromagnetic interference and noise). This is because the lower frequency wavelengths are much greater than the length of the probe  200 , and the probe  200  responds continuously along its length at these frequencies. These lower frequency signals are easily directed to first stage amplifier  50  without distortion. Low frequencies may impinge on receiver probe  200  with periods that are longer than the length of probe  200 . 
     Higher frequencies are also simultaneously conveyed across the slip ring air gap. As frequencies increase, wavelengths decrease and at some point the receiver probe would otherwise transition from a capacitive structure to a transmission line coupler. For example, if the receiver probe had a length of 100 mm, then the probe might begin to transition into a transmission line device at approximately a 1000 mm wavelength or 220 MHz (at the 75% propagation rate). Higher frequencies impinge on the receiver probe with periods that are shorter than the length of the probe. 
     Slip ring probes  100  and  200  utilize a unique continuous filtering mechanism embedded within the slip ring probe. Probes  100  and  200  show improved probe response over a range of digital data rates and protocols by effectively conveying only the proper component frequencies and waveform phase delays required to properly reconstruct the digital waveform after transition across non-contacting air gap  60 . 
     Probes  100  and  200  are very accurate and may be used with any set of frequency components to reconstruct complex waveforms after transition across air gap  60 , even more complex than a simple binary digital waveform reconstruction (i.e., PAM-4). This topology requires a continuously varying loss tangent in the conductive material. The slip ring probe may be constructed by a 3D printing method using a variable-doped material that increases the loss tangent along the length of the slip ring probe. 
     The slip ring probes  100  and  200  may be utilized for binary encoded digital waveforms. The slip ring probes  100  and  200  may also substantially reduce unwanted out-of-band noise that results in both timing skew and analog quantization errors. As a result, slip ring probes  100  and  200  apply to the accurate reconstruction of more complex communication waveforms across a space-gap, including but not limited to PAM-4 and PAM-8 waveforms and their derivatives. The accuracy of waveforms conveyed using the slip ring probe  100  and  200  also uses modulations other than binary, such as PAM-4 or QAM across rotating interfaces, thereby increasing data transfer rates while using the same channel bandwidth. Moreover, the slip ring probes  100 ,  200  may utilize other digital waveform encoding schemes that use alternative modulations such as PSK, FSK, ASK, QAM,  00 K, CPM, QPSK, FM, AM, and derivatives of these modulation techniques. 
     The slip ring probes  100 ,  200  also improve probe response over a range of digital data rates and protocols by effectively conveying only the proper component frequencies and waveform phase delays required to properly reconstruct the digital waveform after the transition across non-contacting air gap  60 . 
     The slip ring probes  100 ,  200  also improve signal quality of long run-length digital communications (e.g., SMPTE compliant video datastreams) and signal quality of 8b10b communications across rotating non-contacting interfaces. This results in faster data transfer rates across the same bandwidth channel without the increased cost of needing additional channel streams. 
     The slip ring probes  100 ,  200  may further be applied to rotating, linear motion, or stationary non-contacting communication systems. The composition of air gap  60  between the signal source and the slip ring probe  100 ,  200 , though typically air, may be an air-like mixture, a vacuum, or a dielectric material of varying properties. 
     Referring now to  FIGS. 8 and 9 , a third embodiment of an improved slip ring probe is generally indicated at  300 . As shown, probe  300  has a curved configuration similar to first embodiment probe  100  and may be used in the circular slip ring platter configuration of slip ring  115 . Probe  300  also has a pair of segmented conductive strips  310  and  330 , with first conductive strip  310  and second conductive strip  330  each having a length corresponding to the desired low frequency domain of the receiver and configured to receive signals  30  from trace feeds  362  of transmitter  16  across air gap  60  of the rotary joint. First conductive strip  310  and second conductive strip  330  of probe  300  are also not continuous and instead are formed from center segments  319  and  339  and a plurality of conductive segments or pads extending in either direction therefrom, severally indicated at  311  and  331  respectively, with such segments separated by resistors, severally indicated at  314  and  334  respectively, therebetween. However, probe  300  differs from probe  100  and  200  by using backend resistor R and capacitor C elements, severally indicated at  321  and  341 , coupled to each of segments or pads  311  and  331 , respectively, to decrease the frequency response for each of segments  311  and  331  as a function of their distance from or location relative to center segment  319  and  339 , respectively. Each of conductive copper segments or pads  311  and  331  are thereby provided with a different frequency response and such frequency response decreases as they move away from the probe center and pads  319  and  339 , respectively. Each of conductive segments  311  and  331  and resistors  314  and  334  have the same length. In this embodiment, resistors  314  and  334  are turned ninety degrees to shorten the separation between pads and two smaller resistors are disposed between center pads  319  and  339  and immediately adjacent pads  311  and  334 , respectively. 
     Accordingly, slip ring probe  300  includes first conductive strip  310 , with alternating conductive copper segments or pads  311  and resistors  314  forming the strip and RC elements  321  controlling pad frequency response along the strip, and second conductive strip  330 , with alternating copper segments or pads  331  and resistors  334  forming the strip and RC elements  341  controlling pad frequency response along the strip, to attenuate the highest frequencies received at the extents of slip ring probe  300  and keep them from being transmitted to center copper segments or pads  319  and  339  of the respective first conductive strip  310  and second conductive strip  330  of slip ring probe  300 . R/C frequency filter elements  321  and  341  are attached to the underside of each segment or pad  311  and  331 . In this embodiment, the capacitance of each of capacitors C in filter elements  321  and  341  increases as a function of their distance from or location relative to center segments  319  and  339 , such that the segments  311  and  331  immediately adjacent center pads  319  and  339  have the lowest capacitance and capacitors C at the segments on the ends of strips  310  and  330  have the highest capacitance. Thus, in this embodiment the capacitance at the center segments  319  and  339  is zero and such capacitance increases therefrom for each capacitor C for each segment  311  and  331  as they move away from the center of the probe so such segments respond to lower and lower frequencies as they move away from the center of the probe. Each of conductive copper segments or pads  311  and  331  are thereby provided with a different frequency response and such frequency response decreases as they move away from the probe center and pads  319  and  339 , respectively. In this embodiment, the capacitance of capacitors C of each filter element  321  and  341  varies as a function of the corresponding segment  311 ,  331  distance from the center of the probe, but the resistance of the corresponding resistor R of each filter element  321  and  341  may be the same. Strip  310  is shown as having ten line resistors  314 , line segments  311  and corresponding filter elements  321  on both sides of center segment and via  319 . Strip  330  is shown as having ten line resistors  334 , line segments  331  and corresponding filter elements  341  on both sides of center segment and via  339 . However, more or less line resistors, line segments and filter elements may be utilized depending on a particular frequency range suitable for the intended purpose and understood by a person of ordinary skill in the art. 
     Slip ring probe  300  is a gradient frequency response probe that retains the segmented topology, but the higher frequency components are attenuated at each of conductive sections  311  and  331  by passive resistor R and capacitor C filters  321  and  341  (e.g., low pass filters), respectively, that effectively shunts the higher frequencies through a resistive component to ground plane  322  and  342 . The R-C filters  321  and  341  are electrically coupled underneath each segment  311  and  331  of the respective first conductive strip  310  and the second conductive strip  330 . Thus, in this embodiment, the slip ring probe  300  includes a passive resistive-capacitive multi-pole low-pass filter technique across the length of the probe  300  rather than mis-terminated transmission line segments. In either case, the farther the distance from the center tabs and the center informational taps  61  and  62 , the more the upper frequency regions of signal  30  are attenuated. 
     The resistors R and the capacitors C shown in the circuit representation in  FIG. 9  may be either discrete components, a mixture of discrete components and PCB embedded components, or all PCB embedded components. In addition, increasing the number of gradient frequency response (GFR) section components yields a more concise representation of the original digital waveform because all possible harmonic frequencies contained in a given digital signaling progression are accounted for with no gaps. In further embodiments, a GFR probe with many more and smaller segments will start to behave as an ideal, continuous GFR probe, as shown in  FIG. 10 . 
       FIG. 9  also illustrates the frequency structure resonance range being between 2.6 GHz and 11 GHz. However, a smaller or larger frequency structure resonance range may be utilized by the slip ring probe as suitable for the intended purpose and understood by a person of ordinary skill in the art. 
     In this embodiment, slip ring probe  300  may have an overall length of approximately 2.30 inches. Each receiver pad  311  and  331  may be approximately 0.11 inches long and 0.075 inches wide. The substrate of the slip ring probe  300  may be represented as E R =˜4, with a propagation speed of approximately 50% the speed of light (c). The resistors  314 ,  334  between the pads  311 ,  331  are situated vertically to minimize pad-to-pad spacing. The filter components R, C may be located at each pad and may comprise discrete and/or embedded components. The filter component R, C values are selected to pass the highest frequencies while avoiding structure resonance. 
       FIG. 10  illustrates an ideal loss tangent graph  40  with a loss tangent axis  251  and a probe length axis  252 .  FIG. 10  further illustrates slip ring probe  400  with a continuously degrading frequency response  33  along the length of the slip ring probe. The outer extremities of the slip ring probe, towards the first ends  15 A,  15 B and the second ends  35 A,  35 B of the slip ring probe, have greater high-frequency loss. The inner portion of the slip ring probe, nearest the center-tap or via  61 ,  62  have almost no loss at high frequencies. This allows the higher frequencies to feed the amplifier  50  at the center-tap  61 ,  62  of the slip ring probe and constrain wavelengths (frequencies) to a portion of the conductive material  10 ,  30  of the slip ring probe to be short enough as to not form a transmission line along the length of the slip ring probe. As the conductive segments and resistors between the conductive segments get smaller and smaller, the loss tangent graph for the probe approaches the ideal shown in  FIG. 10 . 
     It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. 
     The present disclosure contemplates that many changes and modifications may be made. Therefore, while forms of the improved probe have been shown and described, and a number of alternatives discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the scope of the invention, as defined and differentiated by the following claims.