WO2011072144A1 - Systèmes et procédés de modulation harmonique à impulsions - Google Patents

Systèmes et procédés de modulation harmonique à impulsions Download PDF

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Publication number
WO2011072144A1
WO2011072144A1 PCT/US2010/059723 US2010059723W WO2011072144A1 WO 2011072144 A1 WO2011072144 A1 WO 2011072144A1 US 2010059723 W US2010059723 W US 2010059723W WO 2011072144 A1 WO2011072144 A1 WO 2011072144A1
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Prior art keywords
pulse
resonant circuit
modifying
harmonic modulation
data
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PCT/US2010/059723
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English (en)
Inventor
Maysam Ghovanloo
Farzad Inanlou
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Georgia Tech Research Corporation
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Priority to US13/521,123 priority Critical patent/US8774291B2/en
Publication of WO2011072144A1 publication Critical patent/WO2011072144A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/372—Arrangements in connection with the implantation of stimulators
    • A61N1/37211—Means for communicating with stimulators
    • A61N1/37252—Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data
    • A61N1/3727—Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data characterised by the modulation technique
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/372—Arrangements in connection with the implantation of stimulators
    • A61N1/37211—Means for communicating with stimulators
    • A61N1/37217—Means for communicating with stimulators characterised by the communication link, e.g. acoustic or tactile
    • A61N1/37223—Circuits for electromagnetic coupling

Definitions

  • the various embodiments of the present disclosure relate generally to modulation systems and methods. More particularly, the various embodiments of the present invention are directed to pulse harmonic modulation systems and methods.
  • Near-field inductive links have been extensively used in conventional methods for short- range data and power transmission.
  • An inductive link between two magnetically-coupled coils is now one of the most common methods to wirelessly send power and data from the external world to an Implantable Medical Device ("IMD") that requires relatively high data transmission bandwidth.
  • IMD Implantable Medical Device
  • Conventional inductive links include two adjacently coupled LC tank resonant circuits - one on a receiver-side and one on a transmitter side. By tuning these LC tank circuits at a wireless carrier frequency, the amplitude of a transmitted signal on the receiver-side can be increased significantly while attenuating the out-of-bound interference.
  • IMDs that can use inductive links to receive data and power include, but are not limited to, neuromuscular stimulators, cochlear implants, visual prostheses, and the like.
  • RFID Radio-Frequency Identification
  • Some biomedical implants particularly those that interface with the Central Nervous System (“CNS”), such as cochlear and visual prostheses, need relatively large amounts of data to simultaneously interface with a large number of neurons through multiple channels.
  • CNS Central Nervous System
  • a minimum of 625-1000 pixels are needed in a visual prosthesis to enable a patient to read text with large fonts.
  • Every stimulation command in such prostheses can require ten bits for addressing the stimulating sites, six to eight bits for stimulation pulse amplitude levels, and two to four bits for polarity, parity-checking, and sequencing. This would suggest at least 20- bits per command frame are required for site selection and stimulus amplitude information.
  • the maximum carrier frequency for biomedical implants is limited to a few tens of MHz (generally 20 ⁇ 30 MHz) due to the coupled coils' self-resonance frequency, increased power loss in the power transmission circuitry at higher carrier frequencies, and excessive power dissipation in the tissue, which increases as the carrier frequency squared (f r 2 ). Therefore, a goal of conventional inductive coupling systems and methods is to transmit/receive each data bit with a minimum number of
  • Implantable devices that record the neural activity and send the information out of the body also need wide bandwidth data links. This is because neural signals have a wide bandwidth (0.1 Hz ⁇ 10 kHz) and recording from a large number of electrodes generates a large volume of data.
  • Conventional systems have employed different modulation schemes for transmitting data outside the body. A goal of these systems is to use modulation circuitry that is very low power, capable of handling high data rates, and very small. Also, because power and data are often transmitted simultaneously, the data link must be robust in the presence of the power carrier interference, which can be orders of magnitude larger than the data carrier.
  • ASK Amplitude Shift Keying
  • OOK On-Off Keying
  • FSK Frequency Shift Keying
  • PSK Phase Shift Keying
  • PPM Pulse Position Modulation
  • ASK has been commonly used in conventional systems and methods because of its simple modulation and demodulation circuitry. This method of modulation represents digital data as variations in the amplitude of a carrier signal.
  • ASK is not robust against coupling variations and faces major limitations for high-bandwidth data transmission. High-bandwidth ASK needs high order filters with sharp cut-off frequencies. This requires large capacitors that cannot be easily integrated in the low-frequency end of RF applications.
  • OOK On- Off Keying
  • FSK and PSK operate by modulating data in the frequency or phase of a sinusoidal carrier wave, respectfully.
  • a limitation with FSK is that it occupies a relatively wide bandwidth (>5 MHz).
  • PSK has fewer limitations compared to ASK, OOK, and FSK.
  • the dependence of all of these methods on a carrier signal results in high power consumption, particularly on the transmitter side of the transmissions system.
  • VCO Voltage Controlled Oscillators
  • LSK Load Shift Keying
  • LSK is limited because of its requirement for strong coupling between coils, a switch across the IMD power coil, and an ASK receiver outside of the body. Although the switch is relatively simple to implement and consumes little power, the switch entirely shuts off the power transfer to the IMD when it is closed. Hence, a fundamental problem with LSK is reducing the IMD received power by the switching duty cycle, which is not desired in high performance IMDs.
  • UWB Ultra-Wide Band
  • IR Impulse Radio
  • UWB Ultra-Wide Band
  • BAN Body Area Networks
  • Conventional IR-UWB systems are able to consume small amounts of power because they are carrier- less, which means they do not require any continuously on power- consuming, high-frequency oscillators or frequency stabilization circuitry. These characteristics make IR-UWB look like an attractive choice for the uplink in IMDs.
  • the ordinary IR-UWB which is intended for far-field interactions in the 3.1 ⁇ 10.6 GHz band, is highly absorbed in water; thus, it cannot penetrate or pass through a tissue volume conductor.
  • UWB modulation schemes such as OOK and PPM have been used in conventional systems by coding data in the presence and/or location of the pulses.
  • One of the benefits of UWB is the use of discrete pulses for data transmission instead of continuous carrier signals. This eliminates the use for power consuming components such as oscillators, PLLs, and mixers, and, therefore, contributes to the design of low power and low complexity transmitters.
  • the power carrier interference can dominate the data carrier on the receiver side, such that data recovery becomes nearly impossible.
  • a possible solution to the bandwidth limitation is lowering the coils' quality factor, Q, by adding series or parallel resistors to the coils.
  • Q quality factor
  • on-chip coils Unlike coils used in IMDs, on-chip coils inevitably have low Qs due to their high parasitic resistance. Low Q, however, has the undesirable effect of decreasing the range of the inductive link, i.e. the maximum coil separation. This occurs because the amplitude of the received signal decreases and the noise and interference due to lowering the receiver selectivity increases, which, consequently, degrades the Rx Signal-to-Noise Ratio ("SNR").
  • SNR Signal-to-Noise Ratio
  • the present invention relates to pulse harmonic modulation systems and methods.
  • An exemplary embodiment of the present invention provides a pulse harmonic modulation method. The method comprises transmitting a first data initiation pulse to an input of a first resonant circuit thereby creating an oscillating waveform at an output of a second resonant circuit. The method further comprises transmitting a first modifying pulse to the input of the first resonant circuit, wherein the first modifying pulse reduces the inter-symbol interference at the output of the second resonant circuit by modifying a first portion of the oscillating waveform at the output of the second resonant circuit.
  • the first modifying pulse has a predetermined first amplitude and first time-delay.
  • transmitting the first modifying pulse dampens or decreases the amplitude of the first portion of the oscillating waveform.
  • the transmitting the first modifying pulse maintains or increases the amplitude of the first portion of the oscillating waveform.
  • the first resonant circuit and/or the second resonant circuit can be located substantially within the body of a user.
  • the first resonant circuit and/or the second resonant circuit can be located substantially outside the body of the user.
  • Some embodiments of the pulse harmonic modulation method further comprise transmitting a second modifying pulse to the input of the first resonant circuit, wherein the second modifying pulse modifies a second portion of the oscillating waveform at the output of the second resonant circuit. Additionally, some embodiments of the present invention can transmit data from the input of the first resonant circuit to the output of the second resonant circuit at a rate of at least five megabits per second.
  • the present invention relates to pulse harmonic modulation systems.
  • An exemplary embodiment of the present invention provides a pulse harmonic modulation system.
  • the pulse harmonic modulation system can comprise a
  • first resonant circuit in communication with a second resonant circuit, wherein the first resonant circuit is enabled to receive a first data initiation pulse, which causes an oscillating waveform at an output of the second resonant circuit, and the first resonant circuit is enabled to receive a first modifying pulse to reduce inter-symbol interference at the output of the second resonant circuit by modifying a first portion of the oscillating waveform.
  • the first modifying pulse has a predetermined first amplitude and first time-delay.
  • the first modifying pulse modifies the first portion of the oscillating waveform by dampening or decreasing the amplitude of the first portion of the oscillating waveform.
  • the first modifying pulse modifies the first portion of the oscillating waveform by maintaining or increasing the amplitude of the first portion of the oscillating waveform.
  • the first resonant circuit and/or the second resonant circuit is located substantially within the body of a user.
  • the first resonant circuit and/or the second resonant circuit is located substantially outside the body of a user. In an additional exemplary embodiment of the present invention, the distance between the first resonant circuit and the second resonant circuit is less than about 20 millimeters.
  • the first resonant circuit is enabled to receive a second modifying pulse to modify a second portion of the oscillating waveform. Additionally, some embodiments of the present invention are configured to transmit data from the first resonant circuit to the second resonant circuit at a rate of at least five megabits per second.
  • Figure 1 provides a circuit model schematic of an exemplary embodiment of a pulse harmonic modulation system of the present invention.
  • Figure 2 provides an illustrative waveform example of the effect of a sequence of data initiation pulses and modifying pulses transmitted to the input of a first resonant circuit on an oscillating waveform at the output of a second resonant circuit in an exemplary embodiment of the present invention.
  • Figure 3B illustrates a solid oscillating waveform at the output of the second resonant circuit caused by a data initiation pulse and a dashed oscillating waveform caused by a modifying pulse at the output of the second resonant circuit in an exemplary embodiment of the present invention.
  • Figure 3C provides an illustration of the envelope of the solid oscillating waveform, resulting from the data initiation pulse, and the dashed oscillating waveform, resulting from the modifying pulse, in an exemplary embodiment of the present invention.
  • Figure 3D provides an illustration of a final oscillating waveform at the output of the second resonant circuit in an exemplary embodiment of the present invention.
  • Figure 4 provides a comparison of the frequency response and quality factor of an exemplary pulse harmonic modulation system of the present invention with the frequency responses and quality factors of conventional systems.
  • Figure 5 provides another simplified exemplary embodiment of a pulse harmonic modulation system of the present invention.
  • Figure 6 provides a block diagram of an exemplary pulse patter generator of the present invention.
  • Figure 7 provides an illustration of an exemplary 3-D model of a figure-8 coil in the HFSS field solver, which can be used in the exemplary resonant circuits of the present invention.
  • Figure 8 provides a simplified block diagram of an exemplary receiver of the present invention.
  • Figure 9 provides an illustration of a measurement setup to test an exemplary embodiment of the present invention.
  • Figure 10A illustrates an exemplary data initiation pulse transmitted to the input of the first resonant circuit causing a data initiation oscillating waveform at the output of the second resonant circuit in an exemplary embodiment of the present invention.
  • Figure 10B illustrates an exemplary modifying pulse transmitted to the input of the first resonant circuit causing a modifying oscillating waveform at the output of the second resonant circuit in an exemplary embodiment of the present invention.
  • Figure IOC illustrates an exemplary data initiation pulse followed by a modifying pulse transmitted to the input of the first resonant circuit causing a pulse harmonic modulated oscillating waveform at the output of the second resonant circuit in an exemplary embodiment of the present invention.
  • Figure 11 illustrates measured inputs and outputs using exemplary pulse harmonic modulation systems and methods of the present invention.
  • Figure 12A provides the measured BER at different data rates of exemplary embodiments of the present invention when d is changed from 8 to 20 mm.
  • Figure 12B provides the measured changes in BER due to coil misalignments along X and Y axes in exemplary embodiments of the present invention.
  • Figure 13 provides an exemplary embodiment of a pulse harmonic modulation method.
  • Embodiments of the present invention may be applied to systems or methods for transmitting data via an inductive link. Embodiments of the invention, however, are not limited to use in systems and methods for transmitting data via an inductive link described herein. As those of ordinary skill in the art would understand, embodiments of the invention can be used by any systems or methods for transmitting data via an inductive link, including, but not limited to, IMD systems, RFID systems, contactless smartcards, MEMS, and the like. Additionally, embodiments of the present invention can be used to transmit data in both near-field and far-field applications.
  • An exemplary embodiment of the present invention provides a pulse harmonic modulation method 1300.
  • the pulse harmonic modulation method 1300 can comprise transmitting a first data initiation pulse to an input of a first resonant circuit thereby creating an oscillating waveform at an output of a second resonant circuit 1305.
  • the method can further comprise transmitting a first modifying pulse to the input of the first resonant circuit, wherein the first modifying pulse reduces the inter-symbol interference at the output of the second resonant circuit by modifying a first portion of the oscillating waveform 1310.
  • the pulse harmonic modulation system 100 can comprise a first resonant circuit 105 in communication with a second resonant circuit 110, wherein the first resonant circuit 105 is enabled to receive a first data initiation pulse, which causes an oscillating waveform at an output of the second resonant circuit 110, and the first resonant circuit 105 is enabled to receive a first modifying pulse to reduce inter-symbol interference at the output of the second resonant circuit 110 by modifying a first portion of the oscillating waveform.
  • the use of narrow pulses for data transmission significantly reduces the consumption of power by the circuitry of a data transmitter. If a narrow pulse is transmitted through an inductive link having resonant circuits tuned to a particular carrier frequency, the inductive link will act as a filter and
  • the pulse causes a sinusoidal oscillating waveform with frequency f r .
  • the oscillating waveform will have a dampening trail due to the natural resistance of the resonant circuit. The rate of damping depends on the Q of the resonant circuits used in the wireless link.
  • Some of the pulse harmonic modulation systems and methods of the present invention can achieve a high data transmission rate by causing the oscillating waveform caused by a first pulse to dampen very quickly so that the next pulse, which represents the following data bit, can be easily detected.
  • an exemplary embodiment of the present invention enables the oscillation on the receiver side due to the previous data bit to be dampened significantly before the new data bit is detected. If the oscillating waveform is not dampened quickly enough, Inter-Symbol Interference ("ISI”) can result between the oscillations caused by first data pulse and oscillations caused by the second data pulse.
  • ISI Inter-Symbol Interference
  • the receiver may detect a "0" for the current bit period although a "1" was intended.
  • the receiver may detect a "1" for the current bit period although a "0" was intended.
  • a conventional approach to minimizing ISI is to reduce the Q of the resonant circuits.
  • Figure 1 provides an exemplary embodiment of a pulse harmonic modulation system 100.
  • Some embodiments of the pulse harmonic modulation system comprise a first resonant circuit 105 and a second resonant circuit 110.
  • the resonant circuits can be any resonant circuits known in the art.
  • each resonant circuit comprises an inductor
  • Some embodiments of the pulse harmonic modulation system 100 further comprise a pulse pattern generator 115 in communication with the first resonant circuit 105 and a receiver 120 in communication with the second resonant circuit 110.
  • the pulse pattern generator 115 can transmit a sequence of pulses to the input of the first resonant circuit 105, which results in an oscillating waveform at the output of the second resonant circuit 110. Some of the pulses can be indicative of data bits.
  • the receiver 120 can detect the pattern of the oscillating waveform to determine the intended data bit values transmitted by the pulse pattern generator 115. To ensure that ISI is minimal at the output of the second resonant circuit 110, the oscillating waveform can be continually modified with modifying pulses so that the receiver 120 can correctly detect the intended data bit values that are transmitted.
  • FIG. 13 provides a flowchart of an exemplary pulse harmonic modulation method 1300 of the present invention.
  • the pulse harmonic modulation method 1300 comprises: transmitting a first data initiation pulse to an input of a first resonant circuit 105 thereby creating an oscillating waveform at an output of a second resonant circuit 110 1305; and transmitting a first modifying pulse to the input of the first resonant circuit 105, wherein the first modifying pulse reduces ISI at the output of the second resonant circuit 110 by modifying a first portion of the oscillating waveform 1310.
  • the pulse harmonic modulation method 1300 can further comprise transmitting additional modifying pulses to the input of the first resonant circuit 105, wherein the additional modifying pulses modify additional portions of the oscillating waveform at the output of the second resonant circuit 110.
  • the modifying pulses enable the oscillation pattern in the oscillating waveform to be modified, such that a receiver can more accurately detect the value of the data bits being transferred by the data initiation pulse.
  • the desired modification of the oscillating waveform can be obtained by transmitting modifying pulses with predetermined amplitudes and time-delays. For example, in order to transmit a data bit with a value of "1," a combination of narrow pulses can be transmitted to the input of the first resonant circuit.
  • first pulse in the combination of pulses can be a data initiation pulse, which creates an oscillating waveform on the output of the second resonant circuit.
  • a modifying pulse can be transmitted that continues the oscillating waveform if the following data bit to be transmitted is a "1.”
  • a modifying pulse can be transmitted that dampens the oscillating waveform if the following data bit to be transmitted is a "0.”
  • the step of transmitting the first modifying pulse 1310 increases the amplitude of the first portion of the oscillating waveform (reinforcement pulse).
  • the step of transmitting the first modifying pulse 1310 decreases the amplitude of the first portion of the oscillating waveform (suppression pulse).
  • Figure 2 provides an illustrative example of the effect of a sequence of data initiation pulses and modifying pulses transmitted to the input of a first resonant circuit 105 on an oscillating waveform 215 at the output of a second resonant circuit 110.
  • a first data initiation pulse 205 indicative of a data bit with a value of "1" is transmitted to the input of the first resonant circuit 105.
  • the first data initiation pulse 205 causes an oscillating waveform 215 at the output of the second resonant circuit 110.
  • a first modifying pulse 210 which has a predetermined amplitude based on an amplitude ratio P, is transmitted to the input of the first resonant circuit 105, which causes the oscillating waveform to dampen in accordance with an exemplary embodiment of the present invention.
  • a second data initiation pulse 206 indicative of a data bit with a value of "1" is transmitted to the input of the first resonant circuit 105.
  • the second data initiation pulse 206 causes an oscillating waveform 215 at the output of the second resonant circuit 110.
  • a second modifying pulse 211 which has a predetermined amplitude based on an amplitude ratio P, is transmitted to the input of the first resonant circuit 105, which can cause the oscillating waveform to dampen.
  • no data initiation pulses or modifying pulses are sent to indicate a data bit value of "0.”
  • a third data initiation pulse 207 indicative of a data bit with a value of "1" is transmitted to the input of the first resonant circuit 105.
  • the third data initiation pulse 207 causes an oscillating waveform 215 at the output of the second resonant circuit 110.
  • third data initiation pulse 207 a third modifying pulse 212, which has a predetermined amplitude based on an amplitude ratio "P" is transmitted to the input of the first resonant circuit 105, which can cause the oscillating waveform to dampen.
  • the sequence of data initiation pulses 205, 206, and 207 and modifying pulses 210, 211, and 212 transmitted to the input of the first resonant circuit can result in a final oscillating waveform 215 at the output of the second resonant circuit 110 indicative of the data sequence "1101."
  • each data initiation pulse 205, 206, or 207 follows each data initiation pulse 205, 206, or 207 with a single modifying pulse 210, 211, or 212 during a specific bit period.
  • Other embodiments of the present invention can follow each data initiation pulse with multiple modifying pulses during each bit period.
  • the use of multiple modifying pulses during each bit period can result in the minimization of ISI and the facilitation of robust data demodulation with low Bit-Error Rate ("BER").
  • a sharp pulse is applied to the input of the first resonant circuit 105, Vs, a lowpass filtered version of that pulse can pass as current 7 ? through a resistor Rj and an inductor L of the first resonant circuit 105.
  • Vo can have an oscillatory nature at a frequency close to the secondary resonance, f r - , and decays exponentially.
  • the amplitude of the Vo oscillations (envelope) drops below 4% of its initial value after Q 2 cycles where Q 2 is the quality factor of the second resonant circuit 110,
  • modifying pulses with a width, t pw , is transmitted in every "1" data bit.
  • P and t d are dependent on/ r , ⁇ 2 , t pw , T, and N, which can be the desired number of cycles at the output of the second resonant circuit 110 for a reliable, low-BER data detection before the oscillating waveform is suppressed.
  • the coupling coefficient, k may change due to misalignments or mechanical vibrations at a rate much slower than l/T in some embodiments, because the distance affects all pulses within the bit period in substantially the same way, the pulse harmonic modulation systems and methods can be substantially unaffected.
  • the resistance, R s of a pulse pattern generator 115 can be included in the first resonant circuit 105.
  • the pulse pattern generator 115 can be considered an ideal voltage pulse generator.
  • the values of in the first resonant circuit 105 and R 2 in the second resonant circuit 110 are small, unlike chip stacking, because data coils can have a small number of turns that can be either planar and embedded in the Printed Circuit Board ("PCB”) or wire-wound and embedded in the IMD packaging.
  • PCB Printed Circuit Board
  • the effect of the second resonant circuit 110 on the first resonant circuit 105 can be safely neglected by an exemplary embodiment of the present invention, which simplifies equations used to compute the pulse harmonic modulation parameters.
  • the relationship between the voltages and currents in the first resonant circuit 105 and the second resonant circuit 110 can be shown by,
  • V 1 L x — l - + M— -
  • V 2 L 2 — - + M— 1
  • the series R and R 2 resistors can be changed to their parallel equivalents R P and using,
  • Equation 4 The significance of Equation 4 is that by applying an inverse Laplace transform, the wireless link impulse response can be obtained. Also, the first and second parentheses in the denominator of Equation 4 can be related to the first resonant circuit 105 and second resonant circuit 110, respectively, while the numerator can be related to the coils inductive coupling. In some embodiments, once the parametric values are plugged in to Equation 4, the terms can be separated and the transfer function can be rewritten as,
  • A, cii, ci 2 , B, bi, and 3 ⁇ 4 can be functions of the resonant circuits' components.
  • the numerator in Equation 5 is a differentiation function and the following transformation,
  • Equation 6 e fll ' sin(a 2 i)
  • h(t) can be the subtraction of two exponentially decaying oscillations at a 2 ⁇ b 2 ⁇ 27tf r , one with a long time constant of ⁇ 2R 2 C 2 , and the other one with a short time constant of ⁇ 2R lps C 1 .
  • the result can be an oscillating waveform Vo at the output of the second resonant circuit 110.
  • H env (t) can be the envelope of the wireless link time response in Equation 7
  • Equation 9 h env ⁇ t
  • the oscillating waveform resulting from the modifying pulse be out of phase with respect to oscillating waveform caused by the data initiation pulse, some of these embodiments, the time delay t d can be an integer plus a half a cycle,
  • the predetermined time delay, t d can be calculated by,
  • F 0 can be the resonance frequency of the second resonant circuit 110 or the resonance frequency of both first 105 and second 110 resonant circuits
  • BRF can be the data rate
  • N can be the number of oscillations at the output of the second resonant circuit 110 before the oscillating waveform is modified.
  • the choice of N can not only depend on the oscillation build up time (4/ai) and the data rate (1/7) on the lower and upper ends, respectively, but it also can depend on the receiver 120 bandwidth and other specifications.
  • a larger value of N can allow more time before the oscillating waveform is modified and can make it easier for the receiver 120 to detect data bits at the cost of slowing down the data rate.
  • a smaller value of ⁇ can allow for achieving wider bandwidth and higher data rates.
  • a sharp square pulse for example, may not change the shape of h(t).
  • Figures 3A-3D illustrate data obtained from exemplary embodiments of the present invention.
  • the resonant circuit parameters of the pulse harmonic modulation system 100 embodiment, relied upon to generate the graphs in Figures 3A-3D, are provided in Table 1.
  • Figure 3B illustrates a solid oscillating waveform 315 at the output of the second resonant circuit 110, Vo, caused by a data initiation pulse 305 in an exemplary embodiment of the present invention.
  • Figure 3B provides an illustration of a dashed oscillating waveform 320 at the output of the second resonant circuit 110 by the modifying pulse 310.
  • the solid oscillating waveform 315 caused by the data initiation pulse 305 and the dashed oscillating waveform 320 caused by the modifying pulse 310 can be out of phase with each other and reach the same magnitude around to, which depends on the modifying pulse amplitude ratio, P.
  • the amplitude of the modifying pulses is chosen to be one that will effectively cause the oscillating waveform to be suppressed when the following data bit is a "0" and will effectively cause the oscillating waveform to be maintained when the following data bit is a "1.”
  • Some embodiments of the present invention find the modifying pulse amplitude ratio, P, by using Equation 9 to consider the envelopes of the received waveforms.
  • Figure 4 provides a comparison of the frequency response of an exemplary pulse harmonic modulation system 100 of the present invention 405 with frequency responses of conventional systems 410 and 415.
  • the higher quality factor in the exemplary pulse harmonic modulation system 100, particularly g 2 can result in a higher gain, higher SNR, and better selectivity, which can lead to longer range and more robustness against external interference and coil misalignments, which can be crucial in safe IMD applications.
  • FIG. 5 provides another exemplary embodiment of a pulse harmonic modulation system 100.
  • the exemplary pulse harmonic modulation system 100 can comprise a first resonant circuit 505 and a second resonant circuit 510.
  • the first resonant circuit 505 can comprise a first capacitor, C ⁇ , connected in parallel with a first inductor, L .
  • the second resonant circuit 510 can comprise a second capacitor, C 2 , connected in parallel with a second inductor, L 2 .
  • the first resonant circuit 505 and the second resonant circuit 510 can be coupled with a coupling coefficient, k, due to their distance from each other.
  • the voltage across the first resonant circuit 505 can be denoted by V ⁇
  • the voltage across the second resonant circuit 510 can be denoted by V 2 .
  • V ⁇ and V 2 can be represented by,
  • I and 7 2 can be represented by,
  • Equation 12 and Equation 13 can be simplified as, Equation 14:
  • Equation 15 For Equation 15 to have real roots, the following condition can be met:
  • Equation 6 defines the resonance frequencies of the first resonant circuit 505 and second resonant circuit 510 for an exemplary embodiment of the present invention.
  • basic circuitry theory such as Kirchhoff's voltage and current laws, can be used.
  • a voltage source with a series resistance, Rs, in parallel with the first capacitor, C ⁇ can be added.
  • the transfer function of the pulse harmonic modulation system 100 can then be shown by,
  • parasitic series resistances of L and L 2 can be added to the resistance of the first and second resonant circuit, respectively. Although this may lead to a more complicated equation for the transfer function than Equation 18, the overall structure of the transfer function can remain the same.
  • the factor of jw(S) in the numerator of Equation 18 is not taken into account.
  • the derivative of the resulting equation in the time domain can be calculated to make up for the S factor in the numerator.
  • such a transfer function can be written in the form of individual first order terms: r , i n 1 A B C D
  • the output Out(t) of the pulse harmonic modulation system 100 for the input In(t) can be defined by,
  • specialized software such as MATLAB, can be used to determine the coefficients for the impulse response in Equation 20.
  • Qualitative observations and basic knowledge of resonant circuits can lead to the conclusion that the oscillation coefficients, a 2 and c 2 , are dependent on L , C ⁇ , L 2 , C 2 , and M, and the decay coefficients, a ⁇ and c ⁇ , are dependent on the parasitic series resistances of L , L 2 , and 3 ⁇ 4.
  • FIG. 6 provides a block diagram of an exemplary pulse patter generator 115.
  • An exemplary embodiment of a pulse pattern generator comprises a first programmable delay element 605, a second programmable delay element 610, a pulse generator 615, and a pulse amplitude control block 620.
  • the pulse pattern generator 115 can be implemented using an Altera Cyclone II Field Programmable Gate Array ("FPGA").
  • FPGA Altera Cyclone II Field Programmable Gate Array
  • Data+Clk can be used as the input to the pulse pattern generator 115.
  • the Data+Clk signal goes low only when the data value is "1" and the clock is "0.”
  • the first programmable delay element 605 and second programmable delay element 610 can be used to allow control of the time delay t d and the pulse width t pw , respectively, of the data initiation pulses and modifying pulses, respectively.
  • the time delay of the modifying pulse is the same if the modifying pulse is increasing or decreasing the amplitude of the oscillating waveform because modifying pulses can each have positive or negative polarity.
  • the modifying pulses all have the same polarity (positive only or negative only), but the time delay of each modifying pulse can change depending on whether the modifying pulse is increasing or decreasing the amplitude of the oscillating waveform.
  • the pulse generator block 615 can combine the input with its delayed version to produce a sharp pulse.
  • the pulse amplitude control block 620 can be implemented using a simple ladder network or a high speed Digital to Analog Converter ("DAC"). In any case, the modifying pulse amplitude ratio P can be digitally controllable.
  • the pulse amplitude control block 620 can use a memory cell to determine the desired amplitude for each modifying pulse, such as an EEPROM, in which there can be a table for the amplitude of each pulse based on a certain number of previous bit values.
  • a table of exemplary modifying pulse amplitudes for a given time delay where the previous bit and the current bit are considered is provided in Table 2.
  • Some embodiments of the present invention comprise a table of modifying pulse amplitudes based on two or more previous bits and the current bit. As the data rate increases, considering a greater number of previous bits to predetermine the amplitude for a current modifying pulse can result in lower ISI and increased system robustness.
  • figure-8 coils can be used on FR4 PCB substrate.
  • Figure 7 provides an illustration of an exemplary 3-D model of a figure-8 coil in the HFSS field solver.
  • One reason why the geometry of this exemplary embodiment is advantageous in IMD applications is its resilience against external magnetic field interference, which is key in a multiband transcutaneous inductive wireless link.
  • the currents induced in the two loops of each coil can cancel out due to their opposing directions of winding, while the two data coils can maintain a decent coupling.
  • Table 1 summarizes the measured specifications of the coils in an exemplary embodiment of the present invention.
  • the first resonant circuit 105 and/or the second resonant circuit 110 can be located substantially within the body
  • the pulse harmonic modulation system 100 comprise a receiver 120.
  • Figure 8 provides a simplified block diagram of an exemplary receiver 120.
  • the receiver 120 comprises a Low Noise Amplifier ("LNA") 805, a rectifier 810, and a lowpass filter 815.
  • the LNA has a gain of 26 dB.
  • the lowpass filter 815 has a cutoff frequency of 9 MHz.
  • a high speed comparator 820 can compare a LPF output, which can be the envelope of the final oscillating waveform 325 with a reference voltage to sharpen the received pulses and convert them to logic levels.
  • an FPGA board 825 can oversample the received pulses and convert them to a serial data stream.
  • the FPGA board is an Altera Cyclone GPGA board.
  • the FPGA board 825 overs amples the received pulses at 48 MHz.
  • Figure 9 provides an illustration of a measurement setup to test an exemplary embodiment of the present invention.
  • the setup can comprise of Tektronix GB 1400 (GigaBert) on the pulse patter generator 115 side and receiver 120 side, before and after the two FPGA boards, for high speed data bit stream generation and BER analysis, respectively.
  • Tektronix GB 1400 GigaBert
  • Figures 1 OA- IOC illustrate measured waveforms at the input to the first resonant circuit 105 and output of the second resonant circuit 110 in an exemplary embodiment of the present invention.
  • Figure 10A illustrates an exemplary data initiation pulse transmitted to the input of the first resonant circuit 1005 causing a data initiation oscillating waveform at the output of the second resonant circuit 1010.
  • Figure 10B illustrates an exemplary modifying pulse transmitted to the input of the first resonant circuit 1015 causing a modifying oscillating waveform at the output of the second resonant circuit 1020. It can be seen that a high quality factor has led to slow decay in the data initiation oscillating waveform 1010 and modifying oscillating waveform 1020. This slow decay can lead to high ISI if the data initiation pulse is not followed by a modifying pulse to dampen the oscillating waveform at the output of the second resonant
  • Figure IOC illustrates an exemplary data initiation pulse followed by a modifying pulse transmitted to the input of the first resonant circuit 1025 causing a pulse harmonic modulated oscillating waveform at the output of the second resonant circuit 1030.
  • the quick dampening in the exemplary pulse harmonic modulated oscillating waveform 1030 results in a significant reduction of ISI, which allows data rates in excess of 5 Mbps. While some embodiments of the systems and methods of the present invention are capable of transmitting data at rates exceeding 5 Mbps, the embodiments can also be applied to applications requiring slower data transmission rates.
  • Table 3 provides a list of data rates and BER obtained at particular coil sizes and distances with an exemplary embodiment of the present invention (the PHM modulation scheme) and conventional systems.
  • Figure 11 illustrates measured inputs and outputs using exemplary pulse harmonic modulation systems and methods.
  • the intended transmitted data stream 1105 is relayed by transmitting a sequence of data initiation and modifying pulses 1110 to the input of the first resonant circuit 105.
  • the sequence of data initiation and modifying pulses 1110 causes an oscillating waveform 1115 at the output of the second resonant circuit 110.
  • the oscillating waveform 1115 can be processed by the receiver 120 to obtain the received data stream 1120.
  • the distance between the first resonant circuit 105 and the second resonant circuit 110, d can be any distance. In some embodiments of the invention, d is less than or equal to 2 cm. In other embodiments, however, d can have large values depending on the particular application implementing the systems or methods of the present invention.
  • Figure 12A provides the measured BER at different data rates of exemplary embodiments of the present invention when d is changed from 8 to 20 mm.
  • Figure 12B provides the measured changes in BER due to coil misalignments along the
  • X and Y axes as shown in Figure 7 in an exemplary embodiment of the present invention.
  • the data rate and coils' distance are kept constant at 5.2 Mbps and 1 cm, respectively.
  • the curves in Figure 12B illustrate that figure-8 coils can be more robust against misalignments along the Y-axis compared to the X-axis.

Abstract

La présente invention, selon ses différents modes de réalisation, porte de façon générale sur des systèmes et des procédés de modulation harmonique à impulsions. Un mode de réalisation de la présente invention fournit un procédé de modulation harmonique à impulsions, consistant à transmettre une première impulsion de déclenchement de données à une entrée d'un premier circuit résonant, permettant ainsi de créer une forme d'onde oscillante à une sortie d'un second circuit résonant et à transmettre une première impulsion de modification à l'entrée du premier circuit résonant. La première impulsion de modification permet de modifier une première partie de la forme d'onde oscillante.
PCT/US2010/059723 2009-12-09 2010-12-09 Systèmes et procédés de modulation harmonique à impulsions WO2011072144A1 (fr)

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