CN1302483A

CN1302483A - Method for determining start of pulse in spread spectrum system

Info

Publication number: CN1302483A
Application number: CN00800762A
Authority: CN
Inventors: O·帕维奥
Original assignee: Koninklijke Philips Electronics NV
Current assignee: Serlon
Priority date: 1999-05-04
Filing date: 2000-05-01
Publication date: 2001-07-04
Also published as: KR20010053361A; JP2002543734A; WO2000067387A1; TW503630B; EP1095466A1

Abstract

This station comprises a system in which information is transmitted in the form of symbols appearing in symbol periods. The station comprises a receiving circuit in which a synchronizing circuit is provided for producing an indication of the start of a symbol. This synchronizing circuit comprises a measuring circuit for measuring the energy of the transmitted signal, a first integration circuit for integrating this energy measurement, a second integration circuit for integrating this energy measurement as a function of the output signal of the first integration circuit. Finally, a threshold circuit produces a start-of-received-symbol signal based on the output signal of the second integration circuit.

Description

In spread spectrum communication system, determine the pulse method of the zero hour

The present invention relates to be suitable for the station with a receiving circuit of the system of symbol form transmission information a kind of comprising, this receiving circuit comprises a synchronous circuit, is used for producing an indication that the beginning of a code element is described.

The invention still further relates to a kind of method for synchronous, be used for determining the time started of code element.

The present invention can be applied to adopt the cellular radio telephone net industry of spread spectrum, particularly cdma network industry.

The problem that this system brings is how synchronous receiver is.Want received code element to keep Phase synchronization with local clock.Like this, just can determine the time started of the code element of emission with very high precision.About this point, can consult United States Patent (USP) No. 5712869.In this patent documentation, realize synchronous with pilot signal.

The present invention proposes to simplify the method for synchronization of receiving platform widely, thereby no longer needs the pilot signal synchronizing sequence.

Therefore, a kind of is characterised in that like this, and described synchronous circuit comprises:

A measuring circuit of-measurement transmit signal energy,

-this energy measure is carried out first integrating circuit of integration,

-first integrating circuit output signal is carried out second integrating circuit of integration,

-produce a threshold circuit of the signal of the code element time started that receives according to the output signal of second integrating circuit.

By non-limiting instance, with reference to following embodiment, these aspects of the present invention and others will be seen that and illustrated simultaneously.

In these accompanying drawings:

Fig. 1 is a schematic diagram that comprises the emission system of a platform among the present invention,

Fig. 2 is the schematic diagram of the filter of the coupling of working together with differential ference spiral device,

Fig. 3 illustrates two integrator stage joint group spares among the present invention,

Fig. 4 shows the shape of first integrator input end signal,

Fig. 5 shows the shape of this first integrator output terminal signal,

Fig. 6 show second integrator output terminal signal shape and

Fig. 7 illustrates the schematic diagram of setting up synchronous treatment circuit.

Fig. 1 represents an emission system, it comprise among the present invention with 2 communications of second platform first 1.

Platform

1 and 2 comprises a

radiating portion

11 and 12 respectively, also comprises a receiving unit 14 and 15.Interested in the link of radiating portion 11 and receiving unit 15 foundation especially.This link transmit symbol and use be 3 paths T1, T2 and T3 for example.Each code element is all formed by a binary element or one group of binary element, and the spread spectrum codes C S that is formed by some chips finishes.This yard produced by a code generator 21 at transmitting terminal.This yard CS represents with a filter 22 that is fit to this yard in receiving unit 15, is placed on the output of this receiving unit first order 23.These filter 22 back are differential ference spiral devices.In following article, can find discussion to these unit 22 and 25:

" spread spectrum anti-multipath technology and the application brief introduction in the city digital radio telephone ", the author is G.L.TURIN, this piece article be published in March, 1980 the 68th the volume the 3rd phase the IEEE collection of thesis in 328～353 pages on.

" the integrated digital diversity receiver of spread spectrum communication on the multidiameter fading channel ", its author is C.MOULEC etc., this piece article VTC 1994 367～370 on deliver.

The structure of in Fig. 2, drawing these unit again.Matched filter 22 is to form with two

transversal filters

30 and 31, and each in them is all distributed to path I and Q respectively, and they are relevant with the quadrature phase data with homophase, and these data are from the first order 23.Only describe filter 30 in detail.It comprises cascade delay cell 32a, 32b, 32c ..., each delay cell is all brought the delay that equals a chip period.In this delay cell all use

multiplier

35a, 35b, 35c ..., 35d is with coefficient C _L-1, C _L-2, C _L-3C ₀Adder 38 with

multiplier

35a, 35b, 35c ..., 35d the amplitude of output add up.The value of these coefficients is represented the value of spread spectrum codes C S.These two filters produce in-phase signal x2I and orthogonal signalling x2Q, and they are given the differential ference spiral device 25 that is formed by a

delay line

40 and 41 respectively, are used to produce the delay that equals a code-element period.Two multipliers 45 and 46 are finished multiplying each other of value that the length of delay manservant of an official divides demodulator 25 inputs respectively.With adder 49 result that these multipliers produce is added together then, produces signal A,, it is write as in order to summarize:

A (n)=x2I (n-N) x2I (n)+x2Q (n-N) x2Q (n) is in this formula, and " n " represents current time, and " N " represents the length of

delay line

40 and 41, equals the length of spreading code, thereby equals the perdurabgility of a code element.On the basis of the data that demodulator 25 produces, after handling, in subscriber line circuit 26, produce useful data.

As multipath T1, T2, T3 ... with the result of other interference, it is synchronous with the local spreading code that produces with the data of receiving to be difficult in receiving terminal.In order to realize that this synchronous circuit comprises (Fig. 1) synchronously:

-this energy measure is carried out first integrating circuit 52 of integration,

-first integrating circuit output signal is carried out second integrating circuit 54 of integration,

-produce a threshold circuit 26 of the signal of the code element time started that receives according to the output signal of second integrating circuit.

Like this, on the basis of this pulse start time signal, just might guarantee that receiver is synchronous with a treatment circuit 58.

Integrator

52 and 54 structure illustrate in Fig. 3.The value that these two integrators will produce is with the value integration of demodulator 25.The structure of only having drawn integrator 52 is because the structure of integrator 54 can be identical.Integrator 52 comprises adder 60 and the accumulator that accumulative register 62 forms.Integrator 52 can reinitialize, and under the control of signal SY memory 62 is arranged to 0 then.In order to reinitialize this integrator 54, also adopted signal SY, but this to reinitialize be the output valve of utilizing first integrator, carry out active margin, per two active margins of signal SY.Signal SY is handled by a treatment circuit 58 (Fig. 1), to produce synchronizing signal.

In Fig. 4, the shape of demodulator 25 output end signal A is described.Each paths T1, T2 and T3 provide relevant peaks P1, a P2 and P3 respectively.Obviously propagation parameter can not change too soon.To be reproduced as the structure that previously described peak P1, P2 that the code element SB1 of first value produces and P3 form at the heel code element SB2, this code element SB2 has identical polarity, and meanwhile code element SB2 has identical value with code element SB1.Because code element SB3 subsequently has a different value, therefore a negative peak structure is arranged.

Fig. 5 illustrates the signal B of first integrator 52 outputs, and this integrator all resets to 0 in each code-element period, just as this being introduced the front.Signal C on integrator 54 outputs illustrates in Fig. 6.The accumulator of this integrator 54 is reset 0 at per second code-element period, and this accumulator increases the output valve of first integrator 52 between this two cycles.Therefore, the change of the polarization at peak can cause the slope of a curve of representation signal C to change.This represents with mark BEG in Fig. 6.This signal is handled (Fig. 1) by threshold circuit 56.

Fig. 7 illustrates the structure of treatment circuit 58.This circuit forms around a counter 80, and this counter is counted the signal that clock 81 produces from D/2+In to-D/2+In.Value In allows synchronous variable, explains below that just as meeting D is counter capacity and the function of wishing the synchronization accuracy of acquisition.When the content of counter through 0 the time, the synchronizing signal SY of appearance activity.In fact be exactly the validity of these contents, and examine reinitializing of integrator in these code elements of prompting.When detecting the variation of slope BEG, the value Ibt of counter is sent to processing unit 90 through register 91.A value Ibtt has been determined in this unit in first step, thereby makes: Wherein, the b representative indicates that a latent period of storage before appears in first expection peak that a code element begins.

According to a formula of following type, this value Ibtt can be become an amplitude Ibttf by subsequent filtration, as the function of the value Ibbtf behind the previously filtered (1):

Ibttf=Ibtt α+(1-α) Ibttf (1) α wherein be one less than 1 filter constants.

Calculated value In then, it is exactly the correction value that will count in the downward counter:

In = \frac{IbttfxΓ}{b} + Γ

Wherein Γ is can be with a comparable value of loop gain that forms synchronously.

If do not carry out this filtering, In just can get following value:

This value In is placed in the register 95, and the ending of downward count cycle at it that is to say, when it reaches D/2-1, refills counter 80.

Claims

1. platform, comprise a receiving circuit that is suitable for a kind of system, information is to launch with the form that appears at the code element in the code-element period in this system, in this receiving circuit, a synchronous circuit is arranged, be used to produce a signal, the beginning of a code element be described, it is characterized in that this synchronous circuit comprises:

Measure a measuring circuit of transmit signal energy,

This energy measure is carried out first integrating circuit of integration,

Second integrating circuit is used for this energy measurements is carried out integration, as the function of first integrating circuit output signal,

Produce a threshold circuit of the signal of the code element time started that receives according to the output signal of second integrating circuit.

2. the platform of claim 1 is characterized in that the variation of this threshold circuit detected slope.

3. claim 1 or 2 platform is characterized in that this first integrating circuit all is reset to zero in each code-element period.

4. claim 1 or 2 platform is characterized in that second integrating circuit is reset to 0 in per at least second code-element period, between these reset to 0 operation, recharge with the output valve of first integrating circuit.

5. determine a kind of method of a code element definition pulse start time, be used for the platform of one of claim 1～4, it is characterized in that it may further comprise the steps:

Measure the received energy of exomonental signal,

In a code-element period, this energy is carried out the integration first time,

In at least two code-element periods, this energy is carried out the integration second time,

By the variation of detection, determine the zero hour of pulse by the slope of the output signal of the integration acquisition second time.

6. the method for claim 5, it is characterized in that it comprises that reinitializes a step, be used for periodically reinitializing first integration, also be used in the cycle that reinitializes of first different integrations, reinitializing the integration second time this first integrated value.

7. a kind of emission system of platform that comprises one of claim 1～4.