JPH0621781A - Multichannel false random pattern generator - Google Patents

Abstract

PURPOSE:To increase the number of channels and to form false random pattern generators in the same constitution by selecting the time interval of false random generation the number of stages of a shift register, and a clock period so as to satisfy specific relation. CONSTITUTION:The false random pattern generator of (m) channel is comprised of EXOR with the shift register provided with (n) shift stages so as to generate false random patterns by the same n-th order generating function. A false random pattern calculation part computes data X(t1),..., X(tm),... X(tpm) generated at every time t1, t2,..., tm..., tpm of time interval Zk when the false random pattern with the same constitution of every channel is generated, and stores them as initial values in an initial table. A set of initial values out of P sets of initial values are set on the pattern generator of each channel. At this time, they are selected so as to satisfy equation 15 by the clock periods Tc, (n), and Zk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel pseudo random pattern generator, and more particularly to an increase in the number of channels and a common circuit configuration of pseudo random pattern generators for each channel.

[0002]

2. Description of the Related Art The basic circuit of a pseudo random pattern generator (hereinafter also simply referred to as RP generator) is composed of a shift register and at least one XOR (exclusive OR circuit). FIG. 4 is a diagram showing an example thereof, in which the generator polynomial is F
It is represented by (X) = X ⁵ + X ² +1 and is composed of 5 stages of D-FF (D-type flip-flop circuit) and one XOR. In this way, the pseudo random pattern (PRBS:
Pseudo Random Binary Sequence) is generated by using a feedback shift register. For example, the final stage output and the output of any intermediate shift stage are input to the XOR, and the output is fed back to the input of the shift register. Every time one clock pulse (CK) is input to this circuit, one or more bits of P are output from any one or more shift stages.
RBS data is generated.

As is well known, a pseudo random pattern generator having a generator polynomial F (X) of degree n is generally known.
The PRBS generated by each shift stage is composed of consecutive 2 ⁿ -1.
The pattern of bits is repeated. The outputs of all the shift stages have the same sequence pattern, and the phases are shifted from each other. Therefore, when the PRBS is output from the pseudo random pattern generator, it may be output from any shift stage. Further, the output from any of the plurality of shift stages may be used as the random pattern data.

As shown in FIG. 5, a conventional m-channel pseudo-random pattern generator generates RPs having generator polynomials F ₁ (X), F ₂ (X), ..., F _m (X) different from each other. It is composed of vessels 1 ₁ to 1 _m . Since the generator polynomials F _i (X) (i = 1 to m) are different from each other, the cross correlation of PRBS of each channel CH _i can be made low.

[0005]

[Problems to be Solved by the Invention] Conventional multi-channel P
The RBS generator has a large number of channels m (for example, 10
0 or more), the currently existing generator polynomial F _i (X)
Since there are about 100 types, there is a risk that they will not be realized. Further, since the RP generators of the respective channels are constructed based on different generator polynomials, the circuit configurations are naturally different, and the circuit configurations of the RP generators of the respective channels cannot be made common. It is difficult to make IC.

An object of the present invention is to solve these conventional drawbacks and to provide a multi-channel PRBS generator capable of increasing the number of channels m as compared with the prior art and making the circuit configuration of the RP generator of each channel common. Is.

[0007]

Multi-channel according to the present invention
The channel PRBS generator has an initial value set and a clock
Driven by signals and based on a common generator polynomial
So that a pseudo-random pattern is generated.
First to m-th (m
Is an integer of 2 or more)
Temporary with a living instrument and one of the pseudo-random pattern generators
When a pseudo-random pattern is generated in
Time specified by the number of clock pulses of the clock signal
Interval z_kN pseudo-random pattern generators for each
The initial value is the n-bit data output from the shift stage
The n-th shift stage of the pseudo-random pattern generator
From the n-bit data output from
The first set of m initial values {I
₁ , I₂ ,…, I_m}, The subsequently obtained second set of m
Initial values {I_{m + 1} , I_{m + 2} ,…, I_{m + m}}, And so on
M of the p-th set (p is an integer of 1 or more) obtained by
Initial value of {I_{(p-1) m + 1}, I_{(p-1) m + 2},…, I _{(p-1) m + m}}
Desired initial set of m initial values out of p sets up to
From the initial value generation means for generating
M initial values of the pseudo random number of the m channels
Set them in a pattern generator and put them in a pseudo-random pattern
Control to start and stop the operation of the generator.
And a control means for controlling the time interval z._kFrom the pattern
Each channel is selected to be sufficiently larger than the actual usage time.
The number of shift stages n of the pseudo random pattern generator of
Where Tc is the clock period of the clock signal,
n> log₂[{Σz_k/ Tc} +1], k is 1 to mp
Selected to satisfy -1.

The initial value may be generated by reading from the initial value table, may be generated by an operation by providing an initial value calculation unit, or may have the same structure as the pseudo random pattern generator of each channel. The initial value may be generated using the pseudo random pattern generator of. In the latter case, the frequency of the clock pulse supplied to the pseudo random pattern generator for generating the initial value is selected to be sufficiently higher than the frequency of the clock pulse supplied to the pseudo random pattern generator for each channel.

[0009]

[Example] According to the purpose of use, PRBS can be used within the actual usage time.
So that the autocorrelation value of
Chosen to have a turn sequence and a repeating period
There is. For example, a pseudo random pattern having 61 shift stages
Drives the turn generator with a 19.44 MHz clock signal
If so, the pattern length of PRBS is about 2.3 × 10. ¹⁸B
And its repetition cycle is more than 3000 years.
It In case of multi-channel PRBS generator,
Value of cross-correlation value of PRBS of all channels
Must be: By the way, on two channels
Generate PRBS of the same pattern with a shift of time t
If the cross-correlation value is different from the time t within the same PRBS,
It becomes equal to the autocorrelation value. All multi-channel PRBS
The cross-correlation value is less than the auto-correlation value
If so, there is no problem in practical use.

Therefore, it is only necessary to generate PRBSs of the same pattern in multiple channels with a sufficiently long time offset from each other so that the cross-correlation values will not cause any practical problems within the actual use time. However, in that case, the PRBS starts to occur on one channel and then the PRB starts on the next channel.
This is not practical because it is necessary to wait a time sufficiently longer than the actual use time before the generation of S starts.

In the present invention, multi-channel PRBS generation that satisfies the above conditions is realized by two methods.
The first method is based on the finding that a pattern generated after a time t that satisfies the above condition can be calculated in advance, and the time intervals t ₁ and t are calculated in advance.
₂ , the state values of the shift register of the pseudo random pattern generator after operation are calculated, and those values are set as initial values in the pseudo random pattern generator of each channel, and then the generation of PRBS is started.

Another method is to operate one pseudo-random pattern generator with a high-speed clock to sequentially generate state values corresponding to the time intervals t ₁ , t ₂ , ... Within a time period sufficiently shorter than the actual use time. Then, these are set as initial values in the pseudo random pattern generator of each channel, and then the generation of PRBS is started by the normal clock signal.

Before describing the embodiments of the present invention, first, as a method of obtaining the state value of the shift register after an arbitrary time, which is the basis of the above-mentioned first method, by using the pseudo random pattern generator of FIG. This will be explained as an example. Time t
Each output of the D-FF of the shift stage in X ₁
(T), X ₂ (t), X ₃ (t), X ₄ (t), X ₅
Assuming that (t), the output of each shift stage of the D-FF at time t + 1 after a delay of one clock is expressed by equation (1).

X ₁ (t + 1) = X ₂ (t), X ₂ (t + 1) = X ₃
(T), X ₃ (t + 1) = X ₄ (t), X ₄ (t + 1)
= X ₅ (t), X ₅ (t + 1) = X ₁ (t) + X ₃
(T) ··· (1) However, X ₁ (t) and X ₃ in the fifth line in the equation (1)
The addition operation with (t) is a modulo-2 addition operation (that is, exclusive OR). If the above equation is expressed as a matrix,

[0015]

[Equation 1] Becomes Here, A becomes the formula (3).

[0016]

[Equation 2] The output of each shift stage at time t + 2 is

[0017]

[Equation 3] Therefore, the output of each shift stage at time t + z _k (z _k clocks after time t) is obtained by the equation (5).

[0018]

[Equation 4] From equation (5), the output of all shift stages after an arbitrary clock time z _k from time t, that is, the internal data of the shift register (hereinafter referred to as state value) is obtained. Therefore, the PRBS data after an arbitrary clock time z _k can be calculated. An embodiment of the present invention will be described with reference to FIG. In this embodiment, the initial value calculation unit 2 sequentially calculates the state values that will reach the shift register of the pseudo random pattern generator at each time interval z _k designated by the control unit 3, and m One for each of the RP generators 1 ₁ to 1 _m of m channels CH _{1 to} CH _m .
As the initial value of the set, the initial value of the p set is obtained and stored in the initial value table 4 under the control of the control unit 3.
The m-channel RP generators 1 ₁ to 1 _m have the same structure as each other, and therefore have shift registers having the same number of shift stages inside.

Initial value table 4 for generating PRBS
A desired one set of initial values designated by the control unit 3 is read from and the initial values are set in the shift registers in the RP generators 1 ₁ to 1 _m , respectively. RP generator 1 ₁ ~
By applying the shift clock CK to 1 _m , each of the RP generators 1 ₁ to 1 _m sequentially outputs the PRBS data from one or more predetermined shift stages thereof. The sequence of the generated PRBS can be changed by selecting another set of initial values from the initial value table 4 as necessary and setting them in the RP generators 1 ₁ to 1 _m .

The initial value calculation unit 2 uses a generator polynomial F of degree n.
If PRBS is temporarily generated by a pseudo random pattern generator having the same configuration as the pseudo random pattern generator (D-FF × n stages configuration) of each channel having (X), n at an arbitrary time t ₁ Shift stage data X _{1 to} X
_Based on the n-bit state value X (t ₁ ) (called the first initial value) which is n, the state value X (t ₂ ) (called the second initial value) after an arbitrary z ₁ hour is set to (5) Similar to the formula, it is calculated from the following formula.

[X (t ₂ )] = [X (t ₁ + z ₁ )] = A ^z1 [X (t ₁ )] t ₂ = t ₁ + z ₁ (6) In the above formula, [] is It represents a matrix, and A is also represented by a matrix. Next, an n-bit state value X (t ₃ ) (referred to as a third initial value) after z ₂ hours from time t _{2 is obtained} from the following equation.

[X (t ₃ )] = [X (t ₂ + z ₂ )] = A ^z2 [X (t ₂ )] t ₃ = t ₂ + z ₂ (7) Similarly, the time ( obtaining by the following formula t _m-1) from the z _m-1 hour after the state value X (t _m) (m-th initial value).

[0023] [X (t _m)] = _{[X (t m-1 + z} m-1) ] = A ^zm-1 [X (t _{m-1)] t m = t m-1 +} z m-1 · (8) In this way, the initial value {X} for the m-channel pseudo-random pattern generator of the first set (first group) is set.
(T ₁ ), X (t ₂ ), ..., X (t _m )} are calculated (see FIG. 1B). The i-th initial value X (t _i ) is also referred to as I _i for simplification.

Similarly, initial values {X (t _{m + 1} ), X (t _{m + 2} ), ..., X for the second set of m channels are obtained.
(T _{m + m} )} is obtained, and similarly, the initial value {X (t) of the m channels of the p-th set (p is an integer of 1 or more)
_{(p-1) m + 1} ), X (t _{(p-1) m + 2} ), ..., X
(T _{(p-1) m + m} )} is obtained. The first to p-th initial value sets thus obtained are sequentially written in the initial value table 4.

In the case of simultaneously generating multi-channel PRBS, an arbitrary set designated by the control unit out of a plurality of initial value sets written in the initial value table 4,
For example, the first to m-th initial values X (t ₁ ), X of the first set
(T ₂ ), ..., X (t _m ) are set in the RP generators 1 ₁ to 1 _m , respectively, and the PRBS generation operation is simultaneously started at the timing designated by the control unit 3. The state values of the m RP generators after t hours from the start are X (t ₁ + t), X (t ₂ + t), ..., X (t _m + t), respectively.
Becomes Since data is output as PRBS from one or more predetermined shift stages among the n shift stages of the RP generator of each channel, the symbols X (t ₁ + t), X (t ₂ ) representing these state values are output. + T), ..., X (t _m +
Let t) represent PRBS data generated by each channel after t hours from the start.

Output PRBS data X of RP generator 1 _i
(T _i + t) output PRBS data X of RP generator 1 _j
The cross-correlation coefficient for (t _j + t) is X (t _i + t)
Time difference (phase difference) t _j −t _i = Σz _k
(K is from i to j) becomes equal,
Let's explain it next. Autocorrelation is data X at a certain time
Represents the general dependence of the value of on other time values. Time t
And the autocorrelation coefficient R of the data X (t) at t + τ
_X (τ) is obtained by taking the product of each value at two times and averaging over the observation time T.

[0027]

[Equation 5] In PRBS, when the number of shift stages of the shift register constituting each RP generator is n and the shift clock cycle is Tc,
Generally, it has a period of (2 ⁿ −1) Tc, and this autocorrelation coefficient R _X (τ) is shown in the graph of FIG. Therefore, in the autocorrelation coefficient R _X (τ) of PRBS, τ is (2 ⁿ
-1) It becomes 1 when it is an integral multiple of Tc, and becomes almost 0 otherwise.

The cross-correlation represents the general dependence of one time value of one data X (t) on the other time value of another data Y (t), and the cross-correlation coefficient R _XY (τ ) Is the average of the product of the value of the data X (t) at the time t and the value of the data Y (t) at the time t + τ.

[0029]

[Equation 6] PRBS data X (t) and X (t + t _a ) with time difference t _a
= Y (t), the cross-correlation coefficient R _XY (τ) is (1
By substituting _{X (t + t a + τ} ) to 0) equation Y (t + τ),

[0030]

[Equation 7] (11) the cross-correlation coefficient R _XY (tau) of the expression (9) below the autocorrelation coefficients R _X (tau), equal to the replaced τ → τ + t _a. From this, PRBS data X
Cross correlation coefficient between the (t) and Y (t) = X (t + t a) is the autocorrelation coefficient of X (t), it is understood that the same value with the time difference t _a. Therefore, as described above, RP
PRBS data X (t _i +) output from the generator 1 _i
The cross-correlation coefficient between t) and the PRBS data X (t _j + t) output from the RP generator 1 _j is X (t _i +
the autocorrelation coefficients of t), it can be said that equal with (11) the time difference t corresponding to the time difference _{t a j -t i = Σz k} (k is from i to j).

The autocorrelation coefficient of the PRBS having the generator polynomial F (X) is a sufficiently small value within the period, and as is well known, it is a value that does not pose a practical problem in general. Also in PRBS cross-correlation of any two channels where the phase difference is at a minimum relationship (e.g. adjacent channel CH _i and CH i _{+ 1),} the minimum value z _k of the time difference t _a or t _{i + 1} -t _i Greater than the actual usage time of the PRBS generator (for example, about 100 times), and (2 ⁿ -1) Tc / mp
If you choose a smaller one, PR of each channel in actual use
The cross-correlation coefficient R _XY (τ) of BS is the auto-correlation coefficient R
It never matches _X (τ). Therefore, within such a range, the phase difference (time difference) z _k between the initial values can be selected to any value. And because the cross-correlation coefficient R _XY (τ) is of only staggered tau autocorrelation coefficients R _X (τ) to τ + t _a, the cross-correlation coefficient of PRBS of each channel autocorrelation coefficients Similarly, the value is sufficiently small and does not pose a practical problem.

Assuming that the output continuation time of the multi-channel PRBS generator is T _M , the time difference (phase difference) z _k of the initial value has been described above. Therefore, for example, z _k ≧ 100 × T _M (12) Is set to. If the order of the generator polynomial F (X), and hence the number of stages of the shift register of the pseudo-random pattern generator, is n, in order to maintain the randomness of each RP generator 1 _i , the period of the generated PRBS (2 ⁿ -1) x Tc
(Tc is a clock cycle) is a required time Σz _k (k is 1) when it is assumed that p sets of initial values stored in the initial value table 4 are sequentially generated from the same RP generator 1 _i.
To mp-1). Therefore, (2 ⁿ −1) Tc> Σz _k , k is from 1 to mp−1 (13) 2 ⁿ > {Σz _k / Tc} +1 (14) By taking the logarithm of both sides, the following equation is obtained.

N> log ₂ [{Σz _k / Tc} +1] (15) As an example, clock cycle Tc = 3 μs, PRBS generator usage time T _M = 36000 s (= 100 hours), number of generated channels When m = 40 and the initial value set number p = 16, the number of stages of the pseudo random pattern generator n> 50. In the above description, the initial value stored in the initial value table 4 is set in the RP generator 1 _i for m channels, but in some cases, the initial value calculated by the initial value calculation unit 2 is set to the initial value table. 4 may be simultaneously written to the RP generators 1 ₁ to 1 _m at the same time.

The RP generators 1 ₁ to 1 _m have the same generator polynomial, and their circuit configurations are of course all the same. Further, the place where the output is taken out may be the output of any one or a plurality of shift stages. In the embodiment of FIG. 3, according to the second method, the initial value calculation unit 2 is not used, but a pseudo random pattern generator having the same configuration as the RP generator 1 _i of each channel is operated, and times t ₁ , t ₂ , ... , T _m , t _{m + 1} , ..., t _pm (time interval z
_The state value generated in _k ) is written as an initial value for p sets in the initial value table 4. However,
In this embodiment, R, which is one of the channels CH _{1 to} CH _m , is used as a pseudo random pattern generator for generating an initial value.
A case in which shared with P generator 1 _1, the selector 5 according to a selection signal from the control unit 3 selects and outputs either the normal clock CK with high-speed clock rCK the frequency of the r times, RP generated It is supplied to the vessel 1 _1.

When generating the initial value of the p set, the selector 5 selects the high-speed clock rCK to select the RP generator 1.
₁ , the initial values of p sets are sequentially generated within a time sufficiently shorter than the actual use time of the device, the control unit 3 has a high-speed counter (not shown) inside, and the count value is a predetermined clock time. A write command is given to the initial value table 4 each time To generate PRBS, a desired set of initial values is read from the initial value table 4, and the RP generators 1 ₁ to
1 _m , the normal clock CK is selected by the selector 5 and given to the RP generator 1 _1, and the normal clock CK is also given directly to the other RP generators 1 ₂ to 1 _m.
Start to occur. If the high-speed clock rCK is used, the initial value generation time can be reduced to 1 / r.

In the configuration of FIG. 3, the initial value generated from the RP generator 1 ₁ may be directly set to the other RP generators 1 ₂ to 1 _m without using the initial value table 4. In that case, m-1 initial values are sequentially generated in the order of generation, and the RP generators 1 ₂ to 1
_It is set to _m, and the supply of the high-speed clock rCK is stopped with the m-th initial value generated last. In the configuration of FIG. 3, when the RP generator 1 ₁ as the initial value generator only,
Although it is necessary to provide another channel pseudo-random pattern generator, the selector 5 is not necessary, and the high speed clock rCK may be directly applied to the initial value generating RP generator 1 ₁ .

[0037]

As described above, according to the present invention, the number of PRBS generation channels m and the same generator polynomial F
Since the relationship of equation (15) is established with the number n of shift registers of the RP generator of each channel having (X), the number m of channels is increased by increasing the number n of shift registers. be able to.

Further, since the RP generator of each channel has the same generator polynomial F (X) and therefore has the same circuit configuration, it is easier to design and manufacture as compared with the conventional case where the generator polynomial is different for each channel. In addition, the circuit becomes suitable for IC.

[Brief description of drawings]

1A is a block diagram showing an embodiment of the present invention, and FIG. 1B is a block diagram showing an initial value calculated by an initial value calculation unit 2 in FIG. The figure which shows the generation timing when it is assumed that it generated by the pseudo random pattern generator of the same structure as a random pattern generator.

FIG. 2 is a diagram showing a change characteristic of an autocorrelation coefficient of PRBS generated by the pseudo random pattern generator of each channel of FIG. 1A with respect to time τ.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 has a generator polynomial F (X) = X ⁵ + X ² +1 and
FIG. 3 is a circuit diagram showing an example of a pseudo random pattern generator that generates PRBS.

FIG. 5 is a block diagram of a conventional multi-channel pseudo random pattern generator.

Claims (7)

[Claims] 1. An initial value is set, and the first to mth shift registers each of which is configured by n stages of shift registers are configured to shift-drive by a clock signal and generate a pseudo-random pattern based on a common generator polynomial. The channel pseudo-random pattern generator and m are integers of 2 or more, and when one of the pseudo-random pattern generators tentatively generates a pseudo-random pattern, each is defined by the number of clock pulses of the clock signal. Time interval z _k
The n-bit data output from the n shift stages of the pseudo random pattern generator is used as an initial value for each n-bit data output from the n shift stages of the pseudo random pattern generator. The first set of m initial values {I ₁ , I
₂ , ..., I _m }, followed by a second set of m initial values {I _{m + 1} , I _{m + 2} , ..., I _{m + m} }, and the p (p Is an integer greater than or equal to _{1) and p} sets up to m initial values {I _{(p-1) m + 1} , I _{(p-1) m + 2} , ..., I _{(p-1) m + m} } An initial value generating means for generating a desired one set of m initial values, and m initial values from the initial value generating means are set in the m-channel pseudo-random pattern generator, Control means for starting and stopping the operation of the pseudo random pattern generator of, and the time interval z _k is selected to be sufficiently larger than the actual time of pattern generation, and the pseudo random pattern generation of each channel is performed. The number of shift stages n of the converter is n> log ₂ [{Σz _k / Tc, where Tc is the clock period of the clock signal. } +1], k = 1 to mp
A multi-channel pseudo-random pattern generator selected to satisfy -1. 2. The multi-channel pseudo-random pattern generator according to claim 1, wherein the initial value generating means includes a memory means for storing an initial value of the p set, and the control means is selected from the memory means. A set of the initial values is read and set in the m-channel pseudo-random pattern generator. 3. The multi-channel pseudo-random pattern generating device according to claim 1, wherein the initial value generating means includes an initial value calculating means for generating at least one initial value of the p sets by calculation. 4. The multi-channel pseudo-random pattern generating device according to claim 3, wherein the initial value calculating means generates an initial value of the p set by calculation, and the initial value generating means generates the p set. The control means reads out one set of the initial values selected from the memory means and sets them in the m-channel pseudo-random pattern generator. 5. The multi-channel pseudo-random pattern generating device according to claim 1, wherein the initial value generating means is a high-speed pseudo-random pattern generating means having the same configuration as one of the m-channel pseudo-random pattern generators. It is driven by a high-speed clock signal having a frequency higher than that of the clock signal to generate at least one set of the initial values, which is set in the m-channel pseudo random pattern generator. 6. The multi-channel pseudo random pattern generating device according to claim 5, wherein the high speed pseudo random pattern generating means generates the initial values of the p sets, and the initial value generating means generates the generated p sets. The control means includes memory means for storing initial values, and the control means reads out one set of the initial values selected from the memory means and sets them in the m-channel pseudo-random pattern generator. 7. The multi-channel pseudo random pattern generating device according to claim 1, wherein the initial value generating means selects one of the clock signal and the high speed clock, and the m channel pseudo random pattern. One of the generators is included, and the control means selects the high speed clock by the selecting means to generate the at least one set of initial values and supplies the high speed clock to the one pseudo random pattern generator, thereby generating the pseudo random pattern generator. The one set of initial values is set in the m-channel pseudo-random pattern generator, and when the pseudo-random pattern is generated, the clock signal is selected by the selecting means and given to the m-channel pseudo-random generator. .