FR2746988A1 - Phase setting method for emitted signal and received signal - Google Patents

Abstract

The method involves receiving a signal and setting the phase of a clock signal (3), which is generated at a frequency which is a multiple of the emitted frequency. The rank (23) pulse of the setting-in-phase clock signal, which is approximately coincident with the pulse of the emitted, transmitted and received clock signal (2), is determined for each period (Te) of the clock, over several such periods. The mean of these ranks is determined, and the reception clock signal (4) is generated at the same frequency as the emission signal, but shifted into phase. The rank of the pulse, nearest to the first emission signal pulse received, defines a median rank value.

Description

Method for phasing, for data transmission, a transmitted signal and a corresponding transmitted and received signal, and system for implementing the method.

In the field of digital data transmissions, the transmission of signals carrying said data, generally grouped together in packets for rapid transmission, takes place at the rate of an electrical signal from a transmission clock comprising clock ticks which s 'perform at a given frequency.

A reception of the data thus transmitted requires a prior recovery of the rhythm of the transmission clock and more particularly of the instants at which the tops of the transmission clock occur and depending on a physical quantity called phase.

In general, the transmission of signals introduces noise which is superimposed on the transmitted signal and disturbs the received signal, which is then equal to the transmitted signal but noisy. This disturbance results in particular in a slight random shift of the phase of the received signal with respect to the phase of the transmitted signal.

In this case, in order to correctly recover the transmitted data, you may want to readjust the phase of the signal received after transmission to the phase of the signal sent for transmission. To this end, certain synchronization data, intended to be transmitted before the useful data of the transmitted signal1 can supply, on the reception side, an electronic phasing device, comprising a phase-locked loop system operating at the frequency of 1 'transmission clock. This phase the transmitted signal and the corresponding received signal using non-useful synchronization data, but after a transient step. As a result, the synchronization process is slow. However, the speed of transmission, especially in packets, imposes a much shorter phasing time.

Another solution consists in using two Hem and Hrec clocks, respectively associated with the transmitting and receiving apparatus, and operating at the same frequency.

The reception apparatus comprises a narrow band filter, an electronic device intended to eliminate the frequency components of a signal included in a narrow predetermined frequency domain, and a phase loop system, capable of putting two signals into phase by slaving.

For the phasing, after transmission, of the transmitted signal and the corresponding received signal, a signal from the transmission clock is transmitted to the reception device and passes through the narrow band filter, which has the effect of to reduce the noise superimposed on the clock signal during its transmission by elimination of annoying frequency components.

The signal from the emission clock Hem thus denoised after transmission and reception, as well as the signal from the reception clock Hrec are then introduced into the loop system which puts the two signals in phase by slaving.

This solution gives a satisfactory result but it is also very time consuming.

The present invention provides a faster solution for resetting, after transmission, the phase of the transmitted and received signal to the phase of the corresponding transmitted signal.

To this end, the invention relates to a method for phasing, for a data transmission, a transmitted signal and a corresponding transmitted and received signal, in which the transmission is effected using a clock signal at a transmission frequency Fe, the phase difference between this transmission clock signal and the transmission clock signal transmitted and received on reception is determined, and a reception signal is generated on reception reception clock at a reception frequency Fr equal to the transmission frequency Fe with tops out of phase with those of the clock signal transmitted, transmitted and received of the determined phase shift and therefore in phase with those of the clock signal d 'program.

Advantageously, in order to generate the reception clock signal in phase with transmission clock signal, - a reception clock signal for phasing at a frequency multiple of the transmission frequency Fmp = is generated. nFe, - it is determined, over several periods Te of the transmission clock signal, transmitted and received, and for each of these periods Te, the rank in the period of the top of the phasing clock signal substantially concomitant with a top of the transmission clock signal, transmitted and received, - the ranks thus determined are averaged and - a reception clock signal is generated on reception at a reception frequency Fr equal to the transmission frequency Fe, with tops aligned with those of the average rank and therefore in phase with the transmission clock signal.

Preferably, the frequency of the phasing clock signal Fmp is equal to n times the frequency of the transmit clock signal Fe (Fmp = n
Fe), n being an integer.

Preferably also, when a first top of the transmission clock is received on the reception side, the phasing clock top substantially coinciding in time with the first top received from the transmission clock is assigned , a rank of median value.

Thanks to this, the averaging is realistic.

The invention also relates to a phasing system, for data transmission, of a transmitted signal and of a corresponding transmitted and received signal, comprising, on the transmission side, a transmission clock and, on the reception side, means for determining the phase shift, between the transmission clock signal, transmitted and received and the transmission clock signal, and a reception clock signal generator controlled by said means for determining the phase shift.

Preferably, said means for determining the phase shift comprise a counter, incremented by a clock at the clocking frequency of phasing Fmp, means for determining the state of the counter at the instants of reception of the clock signal tops transmission transmitted and received, and therefore determining the rank of the top of the phasing clock signal substantially concomitant with a top of the transmission clock signal, transmitted and received, an averager, controlled by said means of determination, and a comparator connected at input, to the averager and to the counter for, at output, generating the reception clock signal.

The present invention will be better understood with the aid of the following description of a preferred embodiment of the method of the invention and of the device for implementing the method, with reference to the appended drawing in which - FIG. 1 represents the steps of the phasing process of the invention and - Figure 2 shows a functional block diagram of the device of the invention.

The phasing device of the invention (FIG. 2) is provided, on the transmission side, with an emission clock 5 emitting a signal 1 (FIG. 1) characterized by tops emitted at an emission frequency Fe, otherwise says at a period Te.

The signal 1 of the transmission clock 5 is transmitted to a reception equipment, not shown, but the transmission 20 introduces a noise which is superposed on the signal 1 of the transmission clock 5. Therefore, the signal 2 of the transmission clock as transmitted and received, on the reception side, is noisy. In this case, the superimposed noise comprises a phase shift 22 of the transmission clock signal transmitted and received 2 relative to the signal 1 of the transmission clock, that is to say a slight time offset of the tops of signal 2 with respect to the tops of signal 1. Thus, to phase the signal 2 with the signal 1, that is to say to temporally readjust the signal 2 to the signal 1, the noise is eliminated, in other words the phase shift 22 is determined to phase the signal 2 of the determined phase shift 22, here by averaging, as will be more precisely described.

The reception equipment of the phasing device comprises a counter 6 whose states are incremented by a phasing clock 7 generating a signal 3 comprising tops emitted at a phasing frequency Fmp multiple of the frequency of Fe emission, such as
Fmp = n Fe, n being here integer. Thus, during a period Te of the transmission clock and for each of these periods, the counter 6 goes through n successive states with which rows are associated, here the successive integers from 1 to n.

As a result, the tops of the signal of the transmission clock transmitted and received 2 are identified, on the reception side, at times when the counter 6 is in a state of rank r 23 between 1 and n.

An average 8 of the reception equipment of the phasing device is connected to the counter 6. During several periods Te of the transmission clock 5 and for each of these periods Te, it raises the rank r 23 of l 'state of the counter at the instants of reception of the tops of signal 2, in order to calculate an averaged rank m equal to the integer closest to the average of the rows recorded. This averaging amounts to determining the noise superimposed on the signal 1, in other words to determining the phase shift 22 introduced by the transmission and substantially proportional to the recorded rank subtracted from the averaged rank.

In order to avoid calculating an unrealistic average of end ranks (1, n ...), when we receive, on the reception side, a first top of the transmission clock, we assign to the top of phasing clock substantially coinciding in time with the first top received from the transmission clock, a rank of median value. Thus, the tops of the transmission clock signal 2, transmitted and received, during successive transmissions, on states of counter 6 having ranks close to each other are received on the states of counter 6 of rank substantially middle.

Finally, the phasing device comprises a comparator 10 with two inputs, one connected to the counter 6, the other connected to the averager 8. The comparator 10, by comparison between the averaged row m and the rows of the states of the counter 6 , generates at the output a reception clock signal 4 whose tops are here emitted at the instants which correspond to the state of averaged rank m.

Thus, one obtains, at the output of the comparator 10, a reception clock 11 with a signal 4 whose reception frequency Fr is equal to the transmission frequency Fe, and whose tops are set to those of signal 1 of the transmission clock 5: signal 1 of the transmission clock 5 and signal 4 of the reception clock 11 have been put in phase.

Claims (6)

1.- Method for phasing, for a data transmission (20), of a transmitted signal and of a corresponding transmitted and received signal, in which the transmission is effected by means of a signal clock (1) at a transmission frequency Fe, the phase difference (22) is determined between this transmission clock signal (1) and the transmission clock signal, transmitted and received (2) in reception, and a reception signal (4) of a reception clock (11) is generated at a reception frequency Fr equal to the transmission frequency Fe with tops out of phase with those of the clock signal (2 ) transmitted, transmitted and received from the determined phase shift and therefore in phase with those of the transmission clock signal (1). 2. A phasing method according to claim 1, in which, to generate the signal (4) of the reception clock (11) in phase with the signal (1) of the transmission clock (5) , - a signal (3) from a phasing clock (7) is generated on reception at a frequency multiple of the transmission frequency Fmp = nFe, - one determines1 over several periods, Te of the signal (2 ) of the transmission clock (5), transmitted and received, and for each of these periods Te, the rank (23) of the top of the signal (3) of the phasing clock (7) substantially concomitant with a signal (2) signal from the transmission clock (5), transmitted and received, - the ranks (23) thus determined are averaged and - a signal (4) from the reception clock is generated on reception ( 11) at a reception frequency Fr equal to the transmission frequency Fe, with tops calibrated on those of the average rank and therefore in phase with the signal (1) of the transmission clock (5). 3. A phasing method according to claim 2, in which the frequency of the signal (3) of the phasing clock (7) Fmp is equal to n times the frequency of the signal (1) of the clock. emission (1) Fe (Fmp = n Fe), n being an integer. 4. A phasing method according to claim 2, in which when receiving, on the reception side, a first top of the transmission clock, the phasing clock top substantially coincident in time is assigned to the first top received from the transmission clock, a rank of median value. 5.- A phasing system, for data transmission (20), of a transmitted signal and of a corresponding transmitted and received signal, comprising, on the transmission side, a transmission clock (5) and, on the reception, means for determining the phase shift (6, 7, 8), between the transmission clock signal transmitted and received (2) and the transmission clock signal (1), and a generator (10) signal (4) of the reception clock (11) controlled by said means (6, 7, 8) for determining the phase shift. 6. A phasing system according to claim 5, in which said means (6, 7, 8) for determining the phase shift comprise a counter (6), incremented by a clock (7) at the setting clock frequency. in phase Fmp, means for determining the state of the counter (6) at the instants of reception of the tops of the transmission clock signal transmitted and received (2) and therefore of determining the rank of the top of the clock signal phasing (3) substantially concomitant with a top of the transmission clock signal, transmitted and received (2), an averager (8), controlled by said determination means and a comparator (10) connected at input, to the averager (8) and to the counter (6) for, at output, generating the signal (4) of the reception clock (II).