Classifications

• • 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
  • H04B1/69—Spread spectrum techniques
  • H04B1/7163—Spread spectrum techniques using impulse radio
  • H04B1/71637—Receiver aspects
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
  • H04L25/40—Transmitting circuits; Receiving circuits
  • H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
  • H04L25/4902—Pulse width modulation; Pulse position modulation
• • 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
  • H04B1/69—Spread spectrum techniques
  • H04B1/707—Spread spectrum techniques using direct sequence modulation
  • H04B1/709—Correlator structure
• • 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
  • H04B1/69—Spread spectrum techniques
  • H04B1/7163—Spread spectrum techniques using impulse radio
  • H04B1/7183—Synchronisation

Definitions

• the present invention relates to a demodulator of signals modulated by pulse position, and to a receiver equipped with such a demodulator. It also relates to a corresponding demodulation method.
• the transmission of data by means of a signal modulated by pulse position comprises the emission of a carrier signal with pulses of very short duration and a very low duty cycle.
• the pulses received are analog pulses. Depending on the applications, this received signal can then be processed either analogically, or be digitized, sampled, etc.
• the pulses generally have a duration less than a nanosecond and have a duty cycle of less than 1%.
• the average time between two pulses is around 100 nsec, which corresponds to a frequency of 10 MHz.
• the information carried by the signal is coded by the position, that is to say the temporal occurrence of the pulses. More precisely, the information is coded in the form of slight time lags ⁇ which affect the pulses or not. In other words still, the information transmitted is coded by the fact that certain pulses are emitted slightly in advance or in delay with respect to their normal time of occurrence.
• the bandwidth of the signals modulated by pulse position is very wide, of the order of 1 to 5 GHz.
• the signals modulated by pulse position are also known under the name of "UB signals" (Ultra-Wide Bandwidth).
• the invention finds applications in the field of signal transmission and in particular in the transmission of signals over the radio.
• FIG. 1 very briefly represents a signal receiver modulated by position of pulses.
• It includes an amplifier 10 connected to an antenna 12.
• the reception signal r (t) is directed to a first input 22 of a correlator 20.
• a second input 24 of the correlator receives a decoding signal v (t) which is used to determine the time positions of the pulses of the reception signal.
• the correlator performs an inter-correlation between the reception signal and the decoding signal.
• the decoding signal v (t) is supplied by a pulse generator 30 clocked by a clock 32.
• a synchronization unit 34 connected to the processing unit 26 is provided for synchronizing the decoding signal.
• the device according to Figure 1 poses a number of problems. These are essentially linked to the generation of a decoding signal and to the synchronization of the signal, clocked by a local clock, with the reception signal.
• Another difficulty is linked to a sensitivity of the receiver to disturbing signals from competing transmitters, and to noise.
• the object of the invention is to propose a demodulator and a signal receiver which do not present the difficulties mentioned above.
• Another object is to propose a simplified demodulator and receiver, not containing a local clock, and which does not require the synchronization of a decoding signal, generated from a local clock, with the reception signal.
• Another aim is also to propose a demodulator and a receiver that are not very sensitive to noise and are not very sensitive to signals from competing transmitters.
• Another aim is to propose devices of low cost, comprising a low number of components and which have a low electrical consumption.
• Another object of the invention is to propose a demodulation method corresponding to the devices.
• the invention more specifically relates to a signal demodulator modulated by pulse position, comprising a correlator.
• the correlator is an autocorrelator provided with means for generating a decoding signal from a reception signal modulated by pulse position. Thanks to the characteristics of the invention, the same reception signal is used as the vector signal of the coded information and as a source for generating a decoding signal (demodulation). However, since it is the same signal, the problems of synchronization with a local clock are eliminated. A local reference clock is also unnecessary.
• the autocorrelator comprises a first delay unit to form a first delayed reception signal and, a multiplier to multiply the first delayed reception signal by the decoding signal.
• the first delayed reception signal is affected by a delay substantially equal to an average pulse repetition time.
• the average pulse repetition time noted ⁇ in the following text, in fact corresponds to an average duration separating two successive pulses.
• An average repetition time is considered, insofar as it can be affected by the delay or the advance ⁇ of the individual pulses.
• the duration ⁇ is small compared to ⁇ . Thanks to the first delay unit, the correlation takes place, as it were, between the reception signal and the delayed reception signal.
• the demodulator may include a delay-locked loop connected between the output of the correlator and a control input of the first delay unit.
• the delay lock loop can be connected to the correlator output via a low pass filter. The role of this low-pass filter and the operation of the loop are described later.
• the means for generating a decoding signal are capable of supplying a decoding signal and may include a second delay unit and an adder / subtractor to form the decoding signal by combination of the delayed reception signal and the non-delayed reception signal, the delayed signal having a delay substantially equal to a signal coding time shift.
• signal coding time offset is understood to mean a time offset ⁇ which corresponds to the advance or possibly the delay of the individual pulses and which codes the information carried by the signal.
• the delay introduced by the second delay unit is equal to, or close to, the offset value ⁇ . This value is known for a given type of coding and is substantially constant.
• the offset value ⁇ is around a hundred picoseconds, for example.
• the formation of a decoding signal by subtraction from the reception signal of the delayed reception signal makes the decoding signal asymmetrical and thus allows a distinction between pulses in advance and pulses in delay.
• the invention also relates to a receiver, and in particular a radio receiver, provided with a demodulator as indicated above.
• the receiver may further comprise an antenna, an antenna amplifier and a unit for shaping the demodulated signal supplied at the output of the correlator.
• the invention relates to a method for demodulating a signal modulated by pulse position, in which a decoding signal is formed from the modulated reception signal, and in which a correlation is effected between the decoding signal and the delayed reception signal.
• FIG. 2 is a summary and schematic representation of a receiver of signals modulated by pulse position, according to the invention.
• FIG. 3 is a simplified diagram illustrating a particular embodiment of a demodulator usable in a receiver in accordance with Figure 2.
• FIG. 4 is a timing diagram illustrating a possible operation of a demodulator in accordance with Figure 3.
• FIG. 5 is a timing diagram illustrating another possible operation of the demodulator.
• the receiver for signals modulated by pulse position in FIG. 2 comprises an antenna 112, an antenna amplifier 110, a demodulator 120 and a signal shaping unit 140.
• the demodulator basically consists of: to an autocorrelator. It has no autonomous means for forming a local decoding signal.
• the signal r (t) delivered to the output of the amplifier is applied to an input 122 of the demodulator.
• the reception signal is directly used by the demodulator as signal vector of information and as a basis for the formation of a decoding signal.
• the output 123 of the demodulator delivers a demodulated signal.
• This signal can be used directly or, as shown in FIG. 2, be directed to the signal shaping unit 140.
• This unit can be, for example, an electronic, analog or digital circuit, making it possible to put the signal in the form of logic pulses. More simply, the unit 140 can be summarized as a low-pass integrator filter.
• Reference 130 designates a delay lock loop allowing optimized operation of the demodulator.
• FIG. 3 shows in more detail a possibility of making the demodulator 120.
• a section of the demodulator includes a first delay unit 154 which also receives the reception signal r (t).
• the first delay unit affects the modulated signal for receiving a delay ⁇ equal to, or close to, an average pulse repetition time. It is equal, for example to 100 nanoseconds.
• the first delay unit provides a signal of the form r (t- ⁇ ).
• the demodulator comprises another section for forming a decoding signal v (t) from the reception signal r (t) applied to the input 122.
• the section comprises a second delay unit 150 capable of affecting the signal of reception r (t) of a delay ⁇ .
• the delay ⁇ is for example of the order of a tenth of a nanosecond to a nanosecond. It is adjusted to be equal to, or close to the time offset coding of the signal pulses.
• the delayed signal is applied to an input of an adder / subtractor 152.
• the adder / subtractor 152 also receives the non-delayed reception signal to combine it with the delayed signal.
• the combination is a simple subtraction of the delayed signal from the non-delayed signal.
• One thus obtains a non-symmetrical decoding signal of the type v (t) r (t- ⁇ ) -r (t).
• the variable t simply indicates the time dependence of the signal.
• the decoding signal and the delayed modulated signal from the first delay unit are supplied to a multiplier 160.
• the multiplier which constitutes the heart of the autocorrelator, provides a product of the input signals. This product is zero when in particular one of the signals is zero at a given time t. This probability is linked to the duty cycle of the normally received signal, which is very low. This product can also be close to zero, on average, in the case of non-zero signals but having no correlation property. This characteristic makes it very easy to eliminate unwanted noise or competing signals.
• the multiplier delivers a pulse.
• the pulse delivered by the multiplier is either positive, or negative, or zero, on average.
• the sign of the pulse is dictated by the fact that the pulses of the decoding signal v (t) are early, late, or synchronized with those of the delayed modulated signal r (t- ⁇ ).
• the sign of the pulses delivered by the multiplier thus already constitutes a demodulated signal.
• the signal available at the output of the autocorrelator can be put in a more usual form of logic pulses with a succession of high and low states. This conversion is carried out very simply, in the example illustrated, by a low-pass filter 140.
• the integration constant of this filter is chosen, preferably greater than ⁇ .
• the demodulated signal available at the output of the filter 140, is the output signal. It can be directed, for example, to various playback devices, such as sound playback devices, depending on the destination of the demodulator.
• FIG. 3 shows that the second delay unit 154 has an adjustment input 156.
• This input can advantageously be used for fine adjustment of the delay ⁇ .
• a precise adjustment of the value of ⁇ makes it possible to finely adapt the demodulator for the demodulation of signals with very short pulses and allows good elimination of parasites.
• the delay is adjusted by a delay locking loop 130 which connects the output of the low-pass filter 140 to the adjustment input 156.
• FIG. 4 corresponds to the demodulation of a signal for which the pulses coding a first logic value (1) is assigned a positive time offset + ⁇ and the pulses encoding a second logic value (0) are assigned a negative offset - ⁇ .
• a first line A in FIG. 4 indicates the logic values corresponding to different successive pulses considered. These values are 1, 0, 0, and 1.
• Line B represents the pulses of the reception signal r (t).
• r reception signal
• the reference P indicates a parasitic pulse which is not in phase with the pulses of the reception signal.
• Line C represents the pulses of the delayed signal r (t- ⁇ ) from the second delay unit (154 in Figure 3). It can be observed that the delay ⁇ is not always exactly the same for all the pulses. It undergoes very slight variations while remaining equal to or close to the time ⁇ 0 of average repetition of the pulses.
• Line D represents the decoding signal v (t) available at the output of the adder / subtractor 152. For reasons of simplification, the parasitic pulses are not shown on line D of FIG. 4.
• line E represents the product r (t- ⁇ ) Xv (t) supplied by the multiplier 160.
• the last line F in FIG. 4 shows the signal formed by the low-pass filter 140 provided downstream of multiplier 160.
• the low-pass filter acts here as an integrator.
• a negative signal pulse at the output of the multiplier results in a low output level Nb.
• a positive pulse of the signal at the output of the multiplier results in a high output level Nh.
• a pulse of zero mean value has the effect of maintaining the low or high level previously reached.
• the delay locking loop 164 described with reference to FIG. 3 makes it possible to apply the high or low output states to the control input 156 of the second delay unit 154.
• the unit, in this example of setting work is designed to be applied to the reception signal a ⁇ delay when the level applied to its control input is low level and for supplying the received signal the ⁇ delay b when the level applied to its control input is the level high.
• the passage from ⁇ a to ⁇ b simply amounts to adding or subtracting from the delay a value ⁇ .
• FIG. 5 shows another possible operation of the demodulator for a signal having a different logic coding.
• the coding is based on the fact that a first logic state (0) results in a zero offset of the pulses relative to their temporal position of normal occurrence and that a second logic state (1) results in a + offset ⁇ pulses with respect to their normal occurrence time position.
• the different parts A to F of FIG. 5 correspond to the same types of signals as those shown in Figure 4, so that they can be compared two by two.
• Parts D, ⁇ and F of Figure 5 do not differ fundamentally from the same parts of Figure 4. We can thus refer to the preceding figure.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Synchronisation In Digital Transmission Systems (AREA)
• Dc Digital Transmission (AREA)
• Radar Systems Or Details Thereof (AREA)
• Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)

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• 2002
  • 2002-05-22 FR FR0206217A patent/FR2840130A1/fr not_active Withdrawn
• 2003
  • 2003-05-20 JP JP2004506202A patent/JP2005531945A/ja active Pending
  • 2003-05-20 EP EP03752838A patent/EP1514362A2/de not_active Withdrawn
  • 2003-05-20 US US10/515,107 patent/US20050220187A1/en not_active Abandoned
  • 2003-05-20 WO PCT/FR2003/001517 patent/WO2003098824A2/fr not_active Application Discontinuation

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