Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/26—Systems using multi-frequency codes
  • H04L27/2601—Multicarrier modulation systems
  • H04L27/2647—Arrangements specific to the receiver only
  • H04L27/2649—Demodulators
  • H04L27/26532—Demodulators using other transforms, e.g. discrete cosine transforms, Orthogonal Time Frequency and Space [OTFS] or hermetic transforms
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D3/00—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups
  • G01D3/02—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups with provision for altering or correcting the law of variation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
  • G01R23/16—Spectrum analysis; Fourier analysis
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
  • G06F17/10—Complex mathematical operations
  • G06F17/14—Fourier, Walsh or analogous domain transformations, e.g. Laplace, Hilbert, Karhunen-Loeve, transforms
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
  • H04L25/06—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
  • H04L27/06—Demodulator circuits; Receiver circuits
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/06—Receivers
  • H04B1/16—Circuits
  • H04B1/30—Circuits for homodyne or synchrodyne receivers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L27/00—Modulated-carrier systems
  • H04L27/26—Systems using multi-frequency codes
  • H04L27/2601—Multicarrier modulation systems
  • H04L27/2626—Arrangements specific to the transmitter only
  • H04L27/2627—Modulators
  • H04L27/2639—Modulators using other transforms, e.g. discrete cosine transforms, Orthogonal Time Frequency and Space [OTFS] or hermetic transforms

Definitions

• the invention relates to a method, a Signalverarbei ⁇ processing unit for processing a modulated with a variable Trä ⁇ gerfrequenz signal and a sensor array with a signal processing unit according to the invention.
• the Goertzel algorithm determines a complex, valid for a selected carrier frequency coefficients of a dis ⁇ kreten Fourier transform (DFT) and is therefore often referred to as "DFT for a frequency.”
• DFT dis ⁇ kreten Fourier transform
• the reason for the use is the lower computational complexity compared to DFT if the The number of coefficients to be calculated is small For the measurement of sensor signals of the type described above, the calculation of a single coefficient is sufficient
• the Goertzel algorithm is therefore numerically more efficient than the DFT.
• the algorithm has variants which determine the magnitude and phase or even only one of the two components instead of the complex coefficient. These variants differ only in details and are depending on the application chosen that objective measurement of ⁇ . Both in the prior art and in the invention, the variants may be considered as an algorithm in terms of all essential features.
• the amplitude modulation and the Goert cell algorithm have the disadvantage that they are susceptible to certain interference frequencies interfering with the signal or modulation frequency. If a narrow-band, strong interference is in the used frequency band of Amplitudenmo ⁇ dulation whose frequency and phase are unknown, the measurement error caused thereby can exceed every barrier. A reasonable maximum tolerance of the measuring system can not be specified. The use of the amplitude modulation or the maximum permissible amplitude of interference are limited by this property. In particular, within the scope of security-related Au ⁇ tomobilkomponenten, such as braking systems or Len ⁇ kung systems, such probability of failure of the sensor signals is not acceptable even if these failures occur only with low probability.
• the object of the invention is therefore a method to show a Sig ⁇ nal kausaku or a sensor arrangement, which make it possible with a minimum of computational effort to implement a modulation that is substantially less sensitive to external noise.
• the object is achieved according to a first aspect of the invention by means of a method according to claim 1.
• the invention is based on the basic idea of carrying out the modulation with a variable carrier frequency instead of a fixed carrier frequency and to use a coefficient for the demodulation, which is determined on the basis of the carrier frequencies used. In this way, a spectral distribution of the signal or useful signal over the carrier frequencies is achieved.
• the use of a variable carrier frequency has the advantage that the actual signal or useful signal is modulated in different frequencies and therefore the susceptibility to strong interference frequencies, which falsify the signals outside permissible tolerance ranges, is substantially excludable. In turn, the frequency of random effects of spurious frequencies increases in response to the signals. However, the extent of the impairment is not a problem.
• the demodulation in discrete form takes place with the aid of coefficients , which are calculated as a function of the carrier frequencies.
• the effort for demodulating the sensor signal increases in comparison to the already known Goert cell algorithm only in so far that the coefficients must be calculated in dependence on the carrier ⁇ frequencies.
• the coefficients can be calculated in advance to be used spinach ⁇ sequences are known. Alternatively, the calculation can be made when performing the demodulation. In the former case, there is no difference in terms of computational effort compared to the known Goert cell algorithm. But even in the latter case, the additional computational effort with computational ⁇ units is manageable, which are, for example, used in sensors.
• the determination of carrier frequencies may fail un ⁇ differently as needed. Some options are described in the following. It may be left open how these carrier frequencies are determined. For demodulation it is only necessary that the ones used for modulation Carrier frequencies are also used to calculate the coefficients.
• the demodulation of the modulated signal comprises two phases.
• the first phase of the modulated signal is processed by means of the calculated in dependence of the carrier frequencies coefficients or filtered and Girge ⁇ stores intermediate values.
• the process is repeated for a number of scan ⁇ steps repeated with the re-calculation process is performed on the basis of the previous intermediate values.
• the actual useful signal is then calculated on the basis of coefficient and intermediate values to be selected. An embodiment of this will be explained in more detail below.
• the result is a value of the signal.
• the method as ⁇ derholt is to be performed for each signal or for each signal value.
• the process is characterized crizos ⁇ advantageously that the coefficient depending on the instantaneous frequency of the carrier frequencies is calculated.
• the process is characterized crizos ⁇ advantageously that at least a bandwidth of the carrier frequencies is predefined, wherein the bandwidth is outside predictable interference frequencies. If, depending on the application, certain frequencies have proven to be particularly susceptible to interference, their influence on the useful signal can be further reduced in this way. Alternatively, it is also conceivable, a Bandwidth excluding the known interference frequencies, ie discontinuous frequency bands to use.
• a bandwidth of the carrier frequencies is predefined, the bandwidth being determined as a function of a frequency or frequency bandwidth of the signal.
• the frequency or frequency band width of the signal may also be referred to as a working ⁇ frequency. It defines the frequencies under which the information of the signal is generated. For the application of frequency-dependent sensor impedances, the bandwidth would be defined so that it harmonizes with the operating frequencies of the respective Sensorimpendanz. It must be checked for each application for which frequency is a particularly advantageous transmission ⁇ functioning of the overall system frequency range is established. In this way, on the one hand achieves a reduction of the influences of Störfre ⁇ frequencies which is better the greater the bandwidth, while ensuring that the demodulation of the signal reliably be carried out.
• the process is characterized lodgege ⁇ forms in an advantageous manner that the signal is mo ⁇ duliert by means of a modulation unit, and that the processing of the modulated signal by means of a signal processing unit, wherein the carrier frequencies or instantaneous frequencies between the modu ⁇ lationsaku and the signal processing unit synchroni ⁇ Siert become.
• a simple and secure transmission or transmission of the carrier or instantaneous frequencies to the signal processing unit can be carried out in this way in order to ensure correct demodulation of the signal si ⁇ .
• the process is characterized doctorge ⁇ forms in an advantageous manner that the values of the coefficient or coefficients before modulation of the signal, in particular complete for all carrier frequencies, is calculated. In this way, the additional computational effort for the calculation of the coefficients can be advanced to the method for this purpose, but it is necessary that the carrier frequencies to be used are known.
• the method is advantageously further developed by storing the values of the coefficient in a non-volatile memory.
• the coefficients must then only be retrieved from the memory and thus require no additional calculation.
• n sampling step
• f_sample sampling frequency
• n_max total number of sampling steps for one
• the intermediate values s, sl and s2 points n the intermediate values of the current sample value or of the preceding Abtas ⁇ processing steps n-1 and n-2.
• a filtering of the modulated signal using the adjusted coefficient c (n) which can then be used to calculate the searched signal.
• the inventive method is further developed in that an amplitude of the signal A by means of the equation
• A 2 * sqrt (s2 * s2 + sl * sl - c (n_max) * s 1 * s2) / n_max is calculated. It has been found to be advantageous for the calculation of the amplitude of the signal A the value of Ko ⁇ efficient at the last scanning step n_max to use. However, it is conceivable to use other coefficient values.
• the process is characterized lodge forms ⁇ advantageously that the modulation of the signal is carried out by using pre-computed values of the coefficients. Both the modulation and the demodulation then take place on the basis of the coefficients.
• the values of the coefficients may be calculated in advance for the number of sample values, respectively. In this way, it is particularly easy to achieve the synchronization between the modulation unit and the signal processing ⁇ unit.
• the invention is further achieved according to a second aspect of the invention by means of a signal processing unit according to the second independent main claim. Furthermore, the object of the invention is achieved according to a third aspect of the invention by means of a sensor arrangement having the features according to the third independent main claim.
• Figure 2 shows an embodiment of an inventive
• FIG. 3 shows a profile of the values of the coefficients c
• FIG. 4 shows a profile of the amplitude spectrum corresponding to the values of the coefficient from FIG. 3, and FIG.
• FIG. 5 shows a comparison of the susceptibility of the inventive method with respect to the Goert cell algorithm from the prior art.
• Figure 1 shows the schematic structure of a sensor arrangement 1, which can be integrated in known sensors.
• the sensor arrangement 1 comprises a modulation unit 3 for modulating a signal or a sensor signal.
• the sensor signal is generated by means of a sensor element 4.
• the invention can be carried out with different ⁇ union types of sensor elements, for example. Ohmic resistors, capacitors or inductances.
• a signal processing unit 5 demodulates the modulated signal signal (n) or performs a part of the demodulation according to the method of the invention.
• the modulation unit 3 and the signal processing unit 5 are connected to one another via a connection 6, so that a synchronization of the 1
• Carrier frequency instantaneous frequency f_signal (s) or the coefficient coef ⁇ c is possible.
• the modulation unit 2 generates a carrier signal having a carrier frequency or within a selected frequency band ⁇ wide.
• the signal is converted by means of a not shown in the figures, digital to analog converter be ⁇ alsschlagt the sensor. It is also conceivable to execute the modulation unit as an analogue oscillator. On the part of the signal processing unit, the analog signal is again converted by means of an analog-to-digital converter.
• the 2 shows an embodiment of the Signalverarbei ⁇ processing unit 5 is shown schematically. Via the input of the signal processing unit 5, the modulated sensor signal is fed. The signal processing unit 5 processes the modulated input signal over a plurality of iterations corresponding to a number of sampling steps.
• the signal processing unit 5 comprises two latches 50, 51.
• the latches 50, 51 store the intermediate values of different sampling steps n-1 and n-2.
• the buffer 50 is connected on the one hand via a multiplier to a coefficient block 52, in which the different values of the coefficient c (n) are stored.
• the value of the latch 50 is multiplied by the respective n-th coefficient value c (n) and added to the input signal.
• the latch 50 is connected to the second latch 51.
• the preceding intermediate value of the first buffer (s2 or s (n-2)) is stored in the second buffer.
• the value from the second latch 51 is subtracted from the input signal signal (n).
• the first latch is connected to the output of the summation element 53. After every Pass the result of the summation element 53 is stored in the first latch 50.
• This value corresponds to the output value of the signal processing unit 5.
• the coefficient block 52 several variants are provided.
• the coefficient block can be formed as a simple memory in which the values of the coefficient to be used are stored. In particular, this variant is advantageous if the frequencies to be used or the frequency band to be used for the modulation of the signal is known or known.
• f_sample sampling frequency.
• the coefficient block 52 it is possible to make the coefficient block 52 as a computing unit, in which the values of the coef ⁇ coefficients c (n) depending on the input value of the instantaneous frequency or carrier frequency f_signal (n) for each scanning step are continuously calculates n.
• the process is essentially a loop that is traversed for the total number of sampling steps n_max.
• two intermediate values sl and s2 are pre-defined with the values zero.
• another intermediate value s is defined, the intermediate value being defined according to the equation given above.
• the term signal (s) ent ⁇ speaks the modulated signal at the sampling step n, which is present here in discrete form.
• the overall process comprising the calculation of the coefficient c (n), the intermediate values s, sl, s2 and the signal A is performed in each case for demodulating a signal value.
• the overall sequence for each value ascertained and modulated by the sensor is supplied by. Since the measuring rate or a measuring cycle of a sensor in 1
• the modulation of the signal will be performed by means of the following procedure to achieve synchronism of the carrier or instantaneous frequency between the modulation unit and the signal processing unit.
• FIGS. 3 and 4 show a comparison of the deviations from ⁇ the demodulated signal according to the inventive method and according to the already known Goert zel algorithm.
• a sampling rate of 1 MHz (A / D and D / A converter) and a measuring cycle of 1 ms were selected.
• the frequency of the ampli ⁇ tudenmodul investigating carrier and the center frequency of the variable carrier are selected around 200 kHz around.
• the instantaneous frequency should oscillate about the center frequency, therefore the mean value of the Coefficient field cFM (l ... nmax) also cAM. This corresponds formally to a frequency modulation.
• a waveform for the coefficient was selected and the carrier signal was determined as a function of the waveform of the coefficients.
• a curve form for the Frequenzmo ⁇ dulation a triangular wave was chosen because this vibration causes a uniform spectral density of the resultant oscillation.
• the instantaneous frequencies at the ends of the spectrum used would be more frequent than those in the middle, while the uniform distribution among others can be achieved with the triangular shape.
• the triangular shape is by no means a prerequisite for the solution according to the invention, however, the uniform use of the spectrum used is always considered to be advantageous if there is no information about the system (application system, transmission medium, expected disturbances ⁇ etc.), the different metrological Benefit different frequencies in the spectrum used.
• the values of the Koeffizentenfeldes cFM (l ... nmax) can be freely chosen, therefore, the amplitude of the three ⁇ ecksform freely selectable. Higher amplitudes result in the use of a wider spectrum. For the reasons discussed above, a balance must be made between the advantages and disadvantages of a broadband design.
• the compromise chosen for this embodiment is shown graphically in FIG.
• the figure shows the cFM values as a function of the index n.
• the associated amplitude spectrum is shown in FIG. 4. The choice of the coefficient field thus leads to approximately uniform use of a band of about 60 kHz at 200 ⁇ 30 kHz.
• the coefficient field is now used to determine the samples of the excitation function with the aid of the inverse Goert cell algorithm.
• the result is stored and the values are successively fed to a D / A converter.
• the excitation signal is fed to the sensor via an amplifier.
• the sensor can, for example, be given a current as an excitation and a voltage can be tapped, or a voltage can be applied and the current can be measured.
• the sensor-modulated signal is fed to an A / D converter. With the samples, a Goert cell filter is now operated using the same coefficient field.
• both parts are synchronized with respect to their instantaneous frequency as shown in FIG.
• the requirement is met to achieve a reduction of interference with low circuit complexity.
• the benefit can be shown to be by Runaway signal processing steps in a Mon- te Carlo simulation ⁇ expects. For this purpose, a fault is added in each pass to the signal of the sensor, which is determined by a random number generator.
• the perturbation is the sum of white noise (broadband) and a sinusoidal signal (narrow band) whose phase and frequency (between 150 and 250 kHz) are random.
• This signal has an amplitude which is 5% of the amplitude of the sensor signal.
• the noise has an equal effective value.
• the solution E according to the invention has a higher number of deviations in the range up to ⁇ 2%. In the range above ⁇ 2%, the number of deviations approaches zero.
• the Goert cell algorithm G known from the prior art also has a low number of deviations above ⁇ 2%. The deviations range up to approximately ⁇ 6%.
• the invention is not limited to use in sensors, although this field of application is particularly advantageous.

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• Engineering & Computer Science (AREA)
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• Indication And Recording Devices For Special Purposes And Tariff Metering Devices (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
• Transmission And Conversion Of Sensor Element Output (AREA)
• Measuring Frequencies, Analyzing Spectra (AREA)

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• 2014
  • 2014-05-26 DE DE102014210009.7A patent/DE102014210009A1/de active Pending
• 2015
  • 2015-05-20 WO PCT/EP2015/061183 patent/WO2015181031A1/de active Application Filing
  • 2015-05-20 CN CN201580025716.XA patent/CN106574848B/zh active Active
  • 2015-05-20 US US15/313,241 patent/US10181971B2/en active Active
  • 2015-05-20 EP EP15727899.5A patent/EP3149608A1/de not_active Withdrawn
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