Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/04—Distributors combined with modulators or demodulators
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
  • H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
  • H03D3/007—Demodulation of angle-, frequency- or phase- modulated oscillations by converting the oscillations into two quadrature related signals
  • H03D3/008—Compensating DC offsets
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/14—Monitoring arrangements
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/16—Time-division multiplex systems in which the time allocation to individual channels within a transmission cycle is variable, e.g. to accommodate varying complexity of signals, to vary number of channels transmitted
  • H04J3/1676—Time-division multiplex with pulse-position, pulse-interval, or pulse-width modulation

Definitions

• the invention relates to a method for correcting a useful signal falsification in the receiving part of a message transmission system, in particular operating according to the TDD or TDMA method, and a device for carrying out this method.
• Time division multiplexing Frequency, time, and code division multiplexing are known as basic multiple access methods, and all three methods are practically used in cellular networks.
• time division multiplexing methods which are practiced as TDD (Time Division Duplex) or TDMA (Time Division Multiple Access) have found widespread use in digital mobile radio networks, often using frequency division multiplexing methods
• FDMA Frequency Division Multiple Access
• Time division multiplexing techniques are also increasingly being used for cordless telephones, a combination of FDMA and TDMA also being provided here.
• FDMA frequency division multiplexing
• TDMA time division multiplexing technique
• Up to ten frequency channels are used for cordless phones, each of which is divided into twelve time slots for uplink and downlink.
• the receivers in TDD or TDMA systems can be constructed according to the direct conversion principle.
• adjacent channel interference as a result of quadratic components which arise in the analog part of the receiver, in particular in the receiving mixer, results in rectangular interference which, in the case of the usual digital modulation, brings about an increase in the bit error rate.
• the bit error rate specified in the system protocols for example the GSM system, very high demands have to be made on the transmission properties of the mixer, which cannot currently be met with established circuit technologies.
• the invention is therefore based on the object of specifying an improved, computational and energy-saving method of the generic type and an apparatus for carrying out this method.
• the invention includes the essential idea of first determining the time of the onset of a malfunction and then using this knowledge to carry out a correction process in a manner which is less complex and thus energy-saving with regard to the calculation processes. By using an analog correction method you can do almost no computation (in the narrower sense).
• a differentiation of the overall signal and then a threshold value discrimination of the first derivative with a predetermined threshold value are first carried out to determine the time of the onset of the disturbance.
• This threshold value corresponds to the maximum possible steepness of the useful signal, in order to avoid false detections multiplied by an appropriately chosen safety factor.
• a special detector element for example a detector diode
• a circuit of a corresponding function for example a so-called RSSI circuit
• the actual correction process carried out using the information about the time of use of the disturbance can be designed as a calculation process based on digitized values of the signal amplitude or alternatively also as an analog "subtraction".
• a (digital) averaging of the overall signal takes place in the period from the rising edge of the useful signal to the point in time of the fault on the one hand and in the period from the point in time of the fault to the falling edge of the useful signal on the other and then a subtraction of the two calculated mean values. It is also possible to determine the interfering signal energy when the interferer is detected and to subtract it from the total signal energy from the time of the interruption. In this latter case, too, a subtraction in the sense of a real calculation is possible after the corresponding energy values have been digitized.
• a device for carrying out the method according to the invention in accordance with the characterization of the method according to the invention given above - detection means are provided for determining the point in time of the fault and correction means connected on the input side with these detection means for carrying out the offset correction.
• Execution options for the recording means have already been mentioned above. If a detector element or a detector circuit is used, this is followed in particular by a correction stage to take the detector characteristic curve into account for the output signal shape and / or a pulse shaper stage.
• the actual correction means can have an analog subtraction device in an analog design; in the case of a digital calculation of the offset or correction amount, a reference value memory and a digital subtraction stage and in particular an average value calculation stage upstream of these units are provided.
• FIG. 2 shows a schematic illustration of a first embodiment in the form of a block diagram
• FIG. 3 shows a schematic illustration of a second embodiment in the form of a block diagram
• FIG. 4 shows a schematic illustration of a third embodiment in the form of a block diagram
• Fig. 5 is a schematic representation of a fourth embodiment in the form of a block diagram.
• FIG. 1 a shows separately the time profile of a useful signal with a carrier frequency fl and a level P1 and an interference signal with a carrier frequency f2 and a level P2, as would occur in an ideal receive mixer.
• t A is the start time (the rising edge) of a useful signal pulse
• t E the end time (falling edge)
• Rising edge of the useful signal pulse starting - interference pulse is designated.
• FIG. 1b A corresponding output signal of a real receive mixer as a function of time is shown in FIG. 1b, the same time axis as in FIG.
• FIG. 2 shows an arrangement 100 comprising a mixer 101, an amplifier stage 102 connected downstream, a low-pass filter 103 connected downstream, and a downstream CO col ⁇ ) M P> P 1
• the arrangement shown last has the particular advantage of increasing the dynamics, since the interference signal is already corrected in the baseband.

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• 2000
  • 2000-05-12 WO PCT/DE2000/001491 patent/WO2001005025A1/de not_active Application Discontinuation
  • 2000-05-12 JP JP2001509147A patent/JP2003504927A/ja not_active Withdrawn
  • 2000-05-12 CN CN00810035A patent/CN1360751A/zh active Pending
  • 2000-05-12 KR KR1020027000201A patent/KR20020025184A/ko not_active Application Discontinuation
  • 2000-05-12 EP EP00938548A patent/EP1195001A1/de not_active Withdrawn
  • 2000-05-12 HU HU0201819A patent/HUP0201819A2/hu unknown

Non-Patent Citations (1)

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