JP6606211B2 - Spread spectrum clock generator, pulse pattern generator, spread spectrum clock generation method and pulse pattern generation method - Google Patents

Description

  The present invention relates to a spread spectrum clock generator and a spread spectrum clock generation method for spreading a spectrum of a signal to generate a spread spectrum clock signal, and a pulse for generating a desired pulse pattern signal using the spread spectrum clock signal and a data signal. The present invention relates to a pattern generator and a pulse pattern generation method.

  In recent years, a spread spectrum clock (SSC) that spreads the spectrum of a signal and generates a spread spectrum clock signal has been adopted as a countermeasure for electromagnetic compatibility (EMC: Electro-Magnetic Compatibility) in computer buses and the like. There are an increasing number of standards. For example, Universal Serial Bus (USB) 3.0, which is one of serial bus standards for connecting peripheral devices to information devices such as computers, and PCI Express (I / O serial interface) 3. There is zero.

  By the way, in recent years, various digital communication devices are required to have a larger transmission capacity with the increase in the number of users and the spread of multimedia communication. For example, a bit error rate (hereinafter abbreviated as an error rate) defined as a comparison between the number of received code errors and the total number of received data is known.

  When these digital communication devices are set as devices under test (DUT: Device Under Test) and the error rate of the devices under test is measured, for example, a bit error rate measuring device disclosed in Patent Document 1 below is disclosed. Used. In this type of bit error rate measurement device, in order to measure how much electrical stress can be tolerated by the device under test, an electrical stress signal of a known pattern is applied as a test signal from the pulse pattern generator, and this test is performed. The error rate is measured by looping back the signal inside or outside the object to be measured, receiving it by the error detection device, and comparing the test signal with the test signal to determine whether there is an error with respect to the applied amount of stress.

  Here, in this type of bit error rate measuring apparatus, when performing a margin test on a device under test, it is necessary to generate a data signal using the above-described spectrum spread clock signal and input it to the device under test. . Therefore, there is a demand for a spread spectrum clock generator and a pulse pattern generator that can generate a spread spectrum clock signal by a desired spread method.

  In order to generate the spread spectrum clock signal, a triangular wave having a predetermined modulation frequency is generated inside the spread spectrum clock generator or the pulse pattern generation device, and a predetermined wave based on the reference clock signal is generated by the triangular wave. A spread spectrum clock signal is generated by performing frequency modulation by sweeping a carrier signal having a carrier frequency. For example, in the conventional PCI Express standard, it is necessary to generate a triangular wave within a modulation frequency range of 30 to 33 kHz. Specifically, in the Gen1 generation of the PCI Express standard, a synthesizer built in the pulse pattern generator is generated in order to generate a triangular wave whose modulation frequency of the spread spectrum clock signal specified in this communication standard is 31.25 kHz. For example, a 5 MHz reference clock signal is input to a DAC (Digital to Analog Converter), and an amplitude per 1 bit in the period of the reference clock signal by a control unit configured by, for example, an FPGA (Field Programmable Gate Array) with respect to the DAC. The 5 MHz reference clock signal is divided by 160 to generate a triangular wave having a modulation frequency of 31.25 kHz which is a 1 / 160th frequency. It had been realized. This conventional operation is shown in FIG.

  FIG. 9 is a schematic configuration diagram of a conventional bit error rate measuring apparatus disclosed in Patent Document 1 below. As shown in the figure, a bit error rate measuring apparatus 100 includes a data storage unit 101 configured by a memory such as a RAM, a comparison data storage unit 102, a position information storage unit 103, and a signal transmission unit configured by an integrated circuit or the like. (Pulse pattern generation device) 104, signal reception unit (error detection device) 105, synchronization detection unit 106, comparison unit 107, display control unit 108, display device 109 such as a CRT or liquid crystal display, and operation unit 110 such as a keyboard In the bit error rate measuring apparatus 100 that measures the error bit by comparing the input data received from the measurement target 500 and the known data to be received from the measurement target 500, a comparison data storage unit 102; One or more detected by a predetermined detection condition by comparing the received input data with known data A comparison unit 107 that sequentially stores comparison data of a bit string including detection bits in the comparison data storage unit 102 in response to detection, and each bit string obtained from the comparison data stored in the comparison data storage unit 102, And a display control unit 108 configured to display on the display device 109 side by side with respect to a position according to a predetermined arrangement condition.

JP 2007-274474 A

  By the way, from the Gen2 generation of the PCI Express standard, the frequency of the triangular wave in the compliance test required for the bit error rate measuring apparatus has been defined as 33 kHz. However, for example, to generate a frequency of a triangular wave specified by Gen2 of the PCI Express standard using a reference clock signal fixed at 5 MHz, that is, 33 kHz of the modulation frequency of the spread spectrum clock signal, 151.5151. However, since it becomes a circulation decimal, a fraction will come out. Here, the frequency division ratio of the DAC must be a natural number and an even number because the triangular wave having the shape shown in FIG. 8 is generated by stepping up and down a predetermined amount of amplitude displacement per bit. In the case of an even number in the vicinity, for example, divided by 152, when the reference clock signal is 5 MHz, the modulation frequency is 32.8947. Therefore, the frequency shifts from a modulation frequency of 33 kHz defined by the PCI Express standard Gen2 to a value about 0.3% smaller. As a result, a spread spectrum clock signal generated from a triangular wave using this modulation frequency is undermodulated. Depending on the spectrum or the division ratio, the spectrum may be excessively modulated. When a device under test is measured using a data signal generated using such a spread spectrum clock signal, there is a problem that the reliability of the measurement result is lowered.

  Furthermore, providing a DDS (Direct Digital Synthesizer), a function generator IC, etc. separately for generating a triangular wave having an arbitrary frequency as a modulation frequency makes the measuring device cost more complicated and makes the device configuration easier. Therefore, it is required to cope with low cost and a simple apparatus configuration.

  Further, the pulse pattern generation device and the pulse pattern generation method in the bit error rate measurement device to which the present invention is applied flexibly correspond to communication standards of a plurality of generations including future generations and old generations. Therefore, it is required to generate a spread spectrum clock signal and a data signal complying with the regulations.

  Therefore, the present invention has been made in view of the above problems, and when a reference clock signal having a fixed frequency is used inside a pulse pattern generator using a spread spectrum clock signal, Even when the modulation frequency is changed or added according to the regulations, the frequency shift with respect to the modulation frequency specified in the communication standard is sufficiently reduced so that the spectrum spread clock signal is modulated in accordance with the communication standard. A spread spectrum clock generator and a spread spectrum clock generation method capable of improving the reliability of measurement results by measuring a device under test using the spread spectrum clock signal, a spread spectrum clock signal and a data signal Pulse pattern generation to generate a desired pulse pattern signal using And its object is to provide a location and a pulse pattern generating method.

In order to achieve the above object, a spread spectrum clock generator according to claim 1 is controlled by a control unit (11) to generate a spread spectrum clock (SSC) defined by a communication standard. A spread spectrum clock having a modulation section (12) for generating a spread spectrum clock signal by frequency modulating a reference clock signal having a predetermined frequency based on a triangular wave having a modulation frequency defined by the communication standard In vessel (1)
The frequency of the reference clock signal fc, the frequency of the triangular wave and fd, first frequency dividing ratio a first number of occurrences of the triangular wave R ₁ times with D _1, a second having a second division ratio D ₂ When a set of waveforms is formed by combining (R ₁ + R ₂ ) triangular waves with the number of occurrences of the triangular wave of R ₂ times, an average frequency averaged as the set of waveforms is Δfd, and the triangular wave The first frequency division ratio D ₁ , the second frequency division ratio D _2, and the number of occurrences of the first triangular wave so that the difference between the frequency fd and the average frequency Δfd is within 0.1%. Frequency division ratio calculating means (11a) for calculating R ₁ times and the number of occurrences R ₂ of the second triangular wave, respectively,
The modulation unit is configured to calculate the first frequency division ratio D ₁ , the second frequency division ratio D ₂ , the number of occurrences R ₁ of the first triangular wave, and the number of occurrences R of the second triangular wave. _The spread spectrum clock signal is generated by frequency-modulating the reference clock signal based on the set of waveforms obtained by the frequency division ratio and the number of occurrences respectively set twice. .

In order to achieve the above object, the spread spectrum clock generator according to claim 2 is controlled by the control unit (11) in order to generate a spread spectrum clock (SSC) defined by a communication standard. A spread spectrum clock having a modulation section (12) for generating a spread spectrum clock signal by frequency modulating a reference clock signal having a predetermined frequency based on a triangular wave having a modulation frequency defined by the communication standard In vessel (1)
The frequency of the reference clock signal is fc, the frequency of the triangular wave is fd, the number of occurrences of the first triangular wave having the first frequency division ratio D ₁ is R ₁ time,..., The nth frequency division ratio D _n. The number of occurrences of the n-th triangular wave having R _n is (R ₁ +... + R _n ) and a set of waveforms combining a triangular wave (n is an integer of 2 or more). The average frequency averaged as the waveform is Δfd, and the first frequency division ratio D ₁ ,... Is set so that the difference between the frequency fd of the triangular wave and the average frequency Δfd is within 0.1%. the frequency dividing ratio D _n of the n, the first triangular wave of occurrences R ₁ times, ... the frequency division ratio calculation means for calculating the number of occurrences R _n times of the triangular wave of the first n respectively ( 11a)
The modulation unit is configured to calculate the first frequency division ratio D ₁ ,..., The nth frequency division ratio D _n, and the number of occurrences of the first triangular wave R ₁ time,. The spread spectrum clock signal is obtained by frequency-modulating the reference clock signal based on the set of waveforms obtained by the frequency division ratio and the number of occurrences set by the number of occurrences Rn of the _nth triangular wave, respectively. It is characterized by generating.

The spread spectrum clock generator according to claim 3 is the spread spectrum clock generator according to claim 1, wherein the frequency division ratio calculating means uses the calculation formula of the following formula (2). the ratio D _1, and the second division ratio D _2, the first triangular wave of occurrences R ₁ times, the number of occurrences R ₂ times the second triangular wave are calculated respectively,
The modulation unit is configured to calculate the first frequency division ratio D ₁ , the second frequency division ratio D ₂ , the number of occurrences R ₁ of the first triangular wave, and the number of occurrences R of the second triangular wave. _The spectrum spread is performed by dividing the frequency by the frequency division ratio set by the number of times and the number of occurrences, and modulating the frequency based on the average frequency obtained by using the calculation formula of the following formula (2). A clock signal is generated.
fd≈Δfd = fc / ((D ₁ × R ₁ + D ₂ × R ₂ ) / (R ₁ + R ₂ )) (2)
However, D ₂ > D ₁ ,
D ₁ and D ₂ are even numbers,
R ₁ and R ₂ are positive integers,
D ₂ = D ₁ + (2 × i) (i = 1 to any integer from 1 to 5)

The spread spectrum clock generator according to claim 4 is the spread spectrum clock generator according to any one of claim 1 or claim 3, wherein the control unit includes amplitude correction means (11e),
When said second frequency dividing ratio D ₂ the first of the larger division ratio D _1, wherein the amplitude correcting means, per 1bit the second triangular wave having the second frequency dividing ratio D ₂ of the amplitude A predetermined amount of displacement is V _a , a predetermined amount of amplitude displacement per bit after correction of the first triangular wave having the first frequency division ratio D ₁ is V _b , and a triangular wave for obtaining a desired modulation degree is obtained. when the maximum voltage is V _delta, with respect to the displacement of a predetermined amount of the amplitude of the per 1bit before correction of the first triangular wave with a frequency division ratio D ₁ of the first, using a formula of the following formula (3) Then, a predetermined amount of displacement _Vb of the amplitude per bit after correction is obtained and corrected.
_{V b = V a × D 2} / D 1 ... Equation (3)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂

The spread spectrum clock generator according to claim 5 is the spread spectrum clock generator according to any one of claim 1 or claim 3, wherein the control unit includes amplitude correction means (11e),
When said second frequency dividing ratio D ₂ the first of the larger division ratio D _1, wherein the amplitude correcting means, per 1bit the second triangular wave having the second frequency dividing ratio D ₂ of the amplitude A predetermined amount of displacement is V _a , a predetermined amount of amplitude displacement per bit after correction of the first triangular wave having the first frequency division ratio D ₁ is V _d , and a triangular wave for obtaining a desired modulation degree is obtained. when the maximum voltage is V _delta, in the first division ratio D ₁ first uncorrected amplitude of a predetermined amount of displacement per 1bit triangular wave with, and only with respect to bit in the apex, the following and correcting seeking displacement V _d of a predetermined amount of amplitude per 1bit after the correction using the equation of formula (4).
_{V d = V a × ((} (D 2 -D 1) / 2) +1) ... Equation (4)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂

The spread spectrum clock generator according to claim 6 is the spread spectrum clock generator according to any one of claim 1 or claim 3, wherein the control unit includes amplitude correction means (11e),
When said second frequency dividing ratio D ₂ the first of the larger division ratio D _1, wherein the amplitude correcting means, per 1bit the second triangular wave having the second frequency dividing ratio D ₂ of the amplitude Generation of a first triangular wave having a predetermined amount of displacement V _a , _a first triangular wave having the first frequency division ratio D ₁ of R _{1 and a} second triangular wave having the second frequency division ratio D ₂ A predetermined amount of displacement of the amplitude of each bit after correction of the entire waveform combined as a triangular wave with R ₂ times is set as V _f , and the maximum voltage of the triangular wave for obtaining a desired modulation degree is set as V _Δ . In this case, a predetermined amount of displacement _Vf of the amplitude of each bit after correction of the entire waveform is obtained and corrected for all of the bits before correction of the entire waveform using the following formula (5). It is characterized by.
_{V f = V a × D 2} × (R 1 + R 2) / (D 1 × R 1 + D 2 × R 2) ... (5)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂

In order to achieve the above object, a spread spectrum clock generation method according to claim 7 is a reference clock having a predetermined frequency for generating a spread spectrum clock (SSC) defined by a communication standard. In a spread spectrum clock generation method for generating a spread spectrum clock signal by frequency-modulating a signal based on a triangular wave having a modulation frequency defined by the communication standard ,
The frequency of the reference clock signal fc, the frequency of the triangular wave and fd, first frequency dividing ratio a first number of occurrences of the triangular wave R ₁ times with D _1, a second having a second division ratio D ₂ When a set of waveforms is formed by combining (R ₁ + R ₂ ) triangular waves with the number of occurrences of the triangular wave of R ₂ times, an average frequency averaged as the set of waveforms is Δfd, and the triangular wave The first frequency division ratio D ₁ , the second frequency division ratio D _2, and the number of occurrences of the first triangular wave so that the difference between the frequency fd and the average frequency Δfd is within 0.1%. A frequency division ratio calculating step (S303) for calculating R ₁ times and the number of occurrences R ₂ of the second triangular wave, respectively;
The calculated first frequency division ratio D ₁ , second frequency division ratio D ₂ , first triangular wave generation number R ₁ , and second triangular wave generation number R ₂ , respectively. A frequency dividing step (S304) for dividing by the set frequency dividing ratio and the number of occurrences;
A spread spectrum clock signal generating step (S305) for generating the spread spectrum clock signal by frequency modulating the reference clock signal based on the set of the obtained waveforms;

To achieve the above object, the spread spectrum clock generation method according to claim 8 is a reference clock having a predetermined frequency for generating a spread spectrum clock (SSC) defined by a communication standard. In a spread spectrum clock generation method for generating a spread spectrum clock signal by frequency-modulating a signal based on a triangular wave having a modulation frequency defined by the communication standard ,
The frequency of the reference clock signal is fc, the frequency of the triangular wave is fd, the number of occurrences of the first triangular wave having the first frequency division ratio D ₁ is R ₁ time,..., The nth frequency division ratio D _n. The number of occurrences of the n-th triangular wave having R _n is (R ₁ +... + R _n ) and a set of waveforms combining a triangular wave (n is an integer of 2 or more). The average frequency averaged as the waveform is Δfd, and the first frequency division ratio D ₁ ,... Is set so that the difference between the frequency fd of the triangular wave and the average frequency Δfd is within 0.1%. the division ratio and D _n of the n, the first triangular wave of occurrences R ₁ times, ... the frequency division ratio calculation step of calculating a number of occurrences R _n times of the triangular wave of the first n respectively ( S303)
The calculated first frequency division ratio D ₁ ,..., The nth frequency division ratio D _n , the number of occurrences of the first triangular wave R ₁ time,. A frequency _dividing step (S304) for _{dividing the} frequency by the frequency _dividing ratio and the number of times of occurrence set respectively for the number of times of occurrence Rn;
A spread spectrum clock signal generating step (S305) for generating the spread spectrum clock signal by frequency modulating the reference clock signal based on the set of the obtained waveforms;

The spread spectrum clock generation method according to claim 9 is the spread spectrum clock generation method according to claim 7, wherein the first frequency division ratio D ₁ , the division ratio D _2, the first triangular wave of occurrences R ₁ once, the frequency division ratio calculation step of calculating the second triangle wave generation number R ₂ times and each (S303),
The calculated first frequency division ratio D ₁ , second frequency division ratio D ₂ , first triangular wave generation number R ₁ , and second triangular wave generation number R ₂ . A frequency dividing step (S304) for dividing the frequency by the set frequency dividing ratio and the number of occurrences,
A spread spectrum clock signal generating step (S305) for generating the spread spectrum clock signal by performing the frequency modulation based on the average frequency obtained by using the calculation formula of the following formula (2). And
fd≈Δfd = fc / ((D ₁ × R ₁ + D ₂ × R ₂ ) / (R ₁ + R ₂ )) (2)
However, D ₂ > D ₁ ,
D ₁ and D ₂ are even numbers,
R ₁ and R ₂ are positive integers,
D ₂ = D ₁ + (2 × i) (i = 1 to any integer from 1 to 5)

Spread spectrum clock generating method according to claim 10, wherein, in the spectrum spread clock generating method according to any one of claims 7 or claim 9, wherein the second frequency dividing ratio D ₂ the first divider when greater than the ratio D _1, the second frequency dividing ratio second per 1bit triangular wave amplitude of a predetermined amount of displacement of the V _a with D _2, the first division ratio first with D ₁ When the displacement of a predetermined amount of amplitude per bit after correction of the triangular wave is V _b and the maximum voltage of the triangular wave for obtaining a desired modulation degree is V _Δ , the first having the first frequency division ratio D ₁ . For the predetermined amount of displacement of the amplitude per 1 bit before correction of the triangular wave, the displacement V _b of the predetermined amount of amplitude per 1 bit after correction is calculated and corrected using the following equation (3). 1 further including an amplitude correction step (S308). Features.
_{V b = V a × D 2} / D 1 ... Equation (3)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂

Spread spectrum clock generating method according to claim 11, wherein, in the spectrum spread clock generating method according to any one of claims 7 or claim 9, wherein the second frequency dividing ratio D ₂ the first divider when greater than the ratio D _1, the second frequency dividing ratio second per 1bit triangular wave amplitude of a predetermined amount of displacement of the V _a with D _2, the first division ratio first with D ₁ When the displacement of a predetermined amount of amplitude per bit after correction of the triangular wave is V _b and the maximum voltage of the triangular wave for obtaining a desired modulation degree is V _Δ , the first having the first frequency division ratio D ₁ . A predetermined amount of amplitude per 1 bit before correction of the triangular wave and a predetermined amount of amplitude per 1 bit after correction using the following formula (4) for only the bit at the apex. Second correction step (S ₎ for obtaining and correcting the displacement Vd 309).
_{V d = V a × ((} (D 2 -D 1) / 2) +1) ... Equation (4)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂

Spread spectrum clock generating method according to claim 12, wherein, in the spectrum spread clock generating method according to any one of claims 7 or claim 9, wherein the second frequency dividing ratio D ₂ the first divider when greater than the ratio D _1, the second frequency dividing ratio second per 1bit triangular wave amplitude of a predetermined amount of displacement of the V _a with D _2, the first division ratio first with D ₁ Each bit after correction of the entire waveform, which is a combination of a triangular wave having a number of occurrences of R ₁ times and a second triangular wave having the second frequency dividing ratio D ₂ of R _2. The following equation (5) is calculated for all the bits before correction of the entire waveform, where V _f is the displacement of a predetermined amount of the amplitude of V _f and V _Δ is the maximum voltage of the triangular wave for obtaining the desired degree of modulation. Predetermined amount of amplitude of each bit after correction of the entire waveform using an equation Seeking displacement V _f, characterized in that it further comprises a third amplitude correction step of correcting (S310).
_{V f = V a × D 2} × (R 1 + R 2) / (D 1 × R 1 + D 2 × R 2) ... (5)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂

  A pulse pattern generation device according to claim 13 generates a pulse pattern signal using a spread spectrum clock signal generated by the spread spectrum clock generator according to any one of claims 1 to 6. Features.

  The pulse pattern generation method according to claim 14 includes a step of generating a pulse pattern signal using the spread spectrum clock signal generated by the spread spectrum clock generation method according to any one of claims 7 to 11. It is characterized by including.

  According to the spread spectrum clock generator and spread spectrum clock generation method of the present invention, the pulse pattern generation device and the pulse pattern generation method for generating a desired pattern signal using the spread spectrum clock signal and the data signal, the spread spectrum clock signal When a reference clock signal with a fixed frequency is used inside a pulse pattern generator that uses, even if the modulation frequency is changed or added according to the communication standard, it is specified in the communication standard. By making the frequency shift with respect to the modulation frequency sufficiently small, the spectrum spread clock signal is modulated in accordance with the communication standard, and measuring the device under test using this spectrum spread clock signal ensures the reliability of the measurement results. It becomes possible to improve the property.

1 is a block diagram of a pulse pattern generator including a spread spectrum clock generator according to the present invention. It is a block block diagram which shows an example of the modulation | alteration part of FIG. It is explanatory drawing which shows an example of operation | movement of the frequency division ratio calculation means which concerns on this invention. It is explanatory drawing which shows an example of operation | movement of the amplitude correction means which concerns on this invention. It is explanatory drawing which shows an example of other operation | movement of the amplitude correction means which concerns on this invention. It is explanatory drawing which shows an example of other operation | movement of the amplitude correction means which concerns on this invention. 6 is a flowchart showing an example of a processing operation for generating a spread spectrum clock according to the present invention. It is explanatory drawing which shows an example of the operation | movement of the conventional frequency division. It is a schematic block diagram which shows the apparatus structure of the conventional bit error rate measuring apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited by this embodiment, and all other forms, examples, operational techniques, etc. that can be implemented by those skilled in the art based on this form are included in the scope of the present invention. .

[Device configuration]
First, the apparatus configuration of the pulse pattern generator according to the present invention will be described with reference to FIGS.

  As shown in FIG. 1, a pulse pattern generation device 200 according to the present embodiment generates a desired pulse pattern signal using a spread spectrum spread clock signal, and includes a spread spectrum clock generator 1, a frequency It is schematically configured to include a multiplication unit 13 and a pulse pattern generation unit 14.

  The spread spectrum clock generator 1 spreads a spectrum by frequency-modulating a reference clock signal having a predetermined frequency based on a triangular wave having a predetermined frequency obtained by dividing the reference clock signal by a predetermined division ratio. A clock signal is generated, and includes a modulation unit 12, a setting unit 15, a display unit 16, and a storage unit 17.

  As shown in FIG. 2, the modulation unit 12 includes a frequency divider 12a, a phase comparator 12b, a charge pump 12c, a loop filter 12d, a modulation generation unit 12e, a triangular wave generation unit 12f, an adder 12g, a voltage controlled oscillator (VCO: (Voltage Controlled Oscillator) 12h.

  The frequency divider 12a sets the center frequency of the spread spectrum clock signal that is spread spectrum and output from the voltage controlled oscillator 12h so that the center frequency of the spread spectrum clock signal is double that of the reference clock signal, and the spectrum output from the voltage controlled oscillator 12h. The spread clock signal is divided as a feedback signal, and the frequency of the divided feedback signal is matched with the frequency of the reference clock signal.

  The phase comparator 12b compares the phases of the reference clock signal and the feedback signal divided by the frequency divider 12a, and outputs a phase difference signal having a pulse width corresponding to the phase difference.

  The charge pump 12c supplies charge / discharge current to the loop filter 12d by the phase difference signal input from the phase comparator 12b.

  The loop filter 12d converts the current supplied from the charge pump 12c into a voltage, and outputs a signal from which the high frequency component of the converted voltage is removed to the adder 12g.

  The modulation generation unit 12e performs frequency modulation by controlling the modulation control signal from the modulation unit control unit 11d in the control unit 11 based on the spread method, carrier frequency, modulation frequency, and modulation degree set by the setting unit 15. Modulation signal is generated, and the generated modulation signal is output to the adder 12g. The modulation generation unit 12e includes a triangular wave generation unit 12f that generates a triangular wave.

  The triangular wave generator 12f generates a triangular wave having a predetermined frequency by controlling the division ratio calculation signal from the division ratio calculation means 11a in the control unit 11 based on the modulation frequency set by the setting unit 15. . That is, the triangular wave generation unit 12f included in the modulation generation unit 12e generates a modulation signal by performing frequency modulation by sweeping the carrier signal having a predetermined carrier frequency based on the reference clock signal by the triangular wave having the predetermined frequency. is doing.

The triangular wave generator 12f is realized by, for example, a general-purpose DAC that operates by controlling the frequency division ratio calculation signal, and outputs a stepped waveform as shown in FIG. This stepped waveform, for example, when the frequency of the reference clock signal is 5 MHz, based on 200nsec of one period, so as to lower the displacement _{V a} predetermined amount of amplitude per 1bit stepwise every 200nsec ing.

Displacement V _a predetermined amount of amplitude per this 1bit is controlled by controlling the amplitude correction signal from the amplitude correcting means 11e in the control unit 11, for obtaining a desired modulation factor set by the setting unit 15 the maximum value V _delta voltage of the triangular wave, the first division ratio D ₁ is a frequency division ratio of a plurality of triangular wave which will be described _later, the second of the division ratio D _2, the first division ratio D ₁ or It has become equally divided voltage by the number of one-half of the second division ratio or larger division ratio of D _2. Here, when the second frequency division ratio D ₂ is set to a frequency division ratio larger than the _first frequency division ratio D ₁ , the size of the plurality of frequency division ratios is expressed by D ₂ > D ₁ , and desired modulation is performed. triangular wave voltage for obtaining the degrees maximum value V _delta of calculating the following equation (1). Incidentally, the relationship between the maximum value V _delta modulation of the triangular wave voltage for obtaining the desired degree of modulation, when performing frequency modulating a carrier signal having a predetermined carrier frequency based on the reference clock signal with a frequency sweep , the peak value of the desired degree of modulation is made to correspond to the maximum value V _delta voltage of the triangular wave. Within the bit error rate measuring device and is designed such that the relationship uniquely determined and the maximum value V _delta modulation of the peak value of the triangular wave of the voltage to obtain a desired degree of modulation. In the communication standard, the modulation degree is defined by this peak value.

V _a = 2 × V _Δ / D ₂ Formula (1)
However, D ₂ > D ₁

When the maximum value V _Δ of the triangular wave voltage for obtaining a desired modulation degree is 1 V, for example, and the second frequency division ratio D ₂ is, for example, 152, the displacement Va of _a predetermined amount of amplitude per bit is a 0.013157 ··· V obtained by equally dividing the 1V from equation (1) in the second division ratio _D 1 of the number 76 of the half of _2.

Further, by controlling the frequency division ratio calculation signal from the frequency division ratio calculation means 11a in the control unit 11, the displacement of the amplitude of the stepped waveform is a first frequency division that is a frequency division ratio of a plurality of triangular waves described later. The displacement direction is turned upside down by a half of each of the ratio D ₁ and the second frequency division ratio D ₂ . When the maximum value V _Δ of the triangular wave voltage for obtaining a desired modulation degree is 1 V, for example, and the second frequency division ratio D ₂ is, for example, 152, for example, when the frequency of the reference clock signal is 5 MHz, After a predetermined amount of displacement V _a (+0.013157... V) of the amplitude per bit in the upward direction 76 times with 200 nsec of one cycle as a break for every 1 bit, the amplitude per bit in the downward direction 76 times A predetermined amount of displacement V _a (−0.013157... V) is made. Thus, if the frequency is 5MHz, for example the reference clock signal, it is realized that the basis of the one period of 200 nsec, raise or lower the displacement _{V a} predetermined amount of amplitude per 1bit stepwise every 200 nsec. By this operation, the stepped waveform forms a substantially triangular wave with a predetermined frequency dividing ratio as one cycle. This stepped waveform is smoothed by a low-pass filter (not shown) included in the triangular wave generator 12f, and is output as a linear triangular wave from the triangular wave generator 12f to the adder 12g. Note that the present invention can be applied to a triangular wave consisting of a straight line or a curve as a linear triangular wave, and can also be applied to a signal for generating a waveform such as Hershey Kiss modulation which is a kind of spread spectrum clock signal.

The first frequency dividing ratio D ₁ in the above has been described with two division ratios in combination with a second division ratio D _2, it is not limited to a combination of the two, three minutes and combinations of division ratios, the first division ratio D _1, · · ·, the division ratio D _{n (where} n is an integer of 3 or more) of the n may be a combination of n division ratio consisting of.

  The triangular wave generator 12f corrects the amplitude of the triangular wave generated by the triangular wave generator 12f by controlling the amplitude correction signal from the amplitude corrector 11e in the controller 11.

  The adder 12g adds the signal input from the loop filter 12d and the modulation signal input from the modulation generation unit 12e, and outputs the added signal to the voltage controlled oscillator 12h.

  The voltage controlled oscillator 12h operates so that the output (spread spectrum clock signal) is fed back to the phase comparator 12b, the input clock and the feedback signal have the same frequency, and the frequency is controlled according to the modulation signal input from the adder 12g. Spread spectrum spread clock signal is output.

  The setting unit 15 uses a spread method (down spread method, center spread method, or upper spread method) as setting information necessary for generating a spread spectrum clock signal subjected to a desired spread spectrum. Selection, modulation frequency (for example, 33 kHz), carrier frequency (for example, 25 MHz) of the selected spread system, and modulation factor (modulation ratio with respect to carrier frequency) are set.

  Moreover, the setting part 15 is comprised with a touchscreen provided with the touch sensor for detecting the contact position by the contact operation to the input surface corresponding to the display screen of the display part 16, for example. The setting unit 15 allows the position detected by the touch sensor on the screen to match the position of the item when the user touches the position of a specific item on the screen displayed on the display unit 16 with a finger or a stylus. And a signal for executing the function assigned to each item is output to the control unit 11.

  The display unit 16 includes a display device such as a liquid crystal display or a CRT. Based on display control (not shown) of the control unit 11, the display unit 16 displays a setting item screen related to the spread spectrum clock generator 1, a screen display related to the pulse pattern generation unit 14, and a pulse. Display contents related to driving of the pattern generator 200 and various controls are displayed.

  The control unit 11 includes a microcomputer such as a CPU, ROM, RAM, and FPGA, for example. The control unit 11 controls the modulation unit 12, the frequency multiplication unit 13, and the pulse pattern generation unit 14 based on the setting information set by the setting unit 15. The control unit includes a frequency division ratio calculation unit 11a, a frequency multiplication unit control unit 11b, a pulse pattern generation unit control unit 11c, a modulation unit control unit 11d, and an amplitude control unit 11e. That is, the modulation unit control unit 11d spreads the spectrum of the reference clock signal according to the selected spread method (spread method of any one of the down spread, center spread, and upper spread), the carrier frequency, the modulation frequency, and the modulation degree. The modulator 12 (modulation generator 12e) is controlled to generate a spread spectrum clock signal. In addition, display control of the display unit 16 and drive control of each unit constituting the pulse pattern generation device 200 are performed.

  The frequency division ratio calculating means 11a calculates a plurality of frequency division ratios for generating the frequency of the triangular wave generated by the triangular wave generation section 12f and the number of times each frequency division ratio is generated, and the frequency division ratio calculation signal is used as the triangular wave generation section. To 12f. The frequency division ratio calculating means 11a generates a plurality of triangular waves according to the plurality of frequency division ratios and the number of occurrences of each frequency division ratio to form a set of waveforms, which are averaged by the set of waveforms. The difference between the average frequency and the modulation frequency specified by the communication standard is set to be within 0.1%.

  The amplitude correcting unit 11e outputs an amplitude correction signal for correcting the amplitude of the triangular wave generated by the triangular wave generating unit 12f to the triangular wave generating unit 12f.

  The storage unit 17 corrects and controls the amplitude of the triangular wave when calculating and controlling a plurality of frequency division ratios for generating the frequency of the triangular wave generated by the triangular wave generation unit 12f and the number of occurrences of each frequency division ratio. The calculation formula (formula (1)-(5)) used for this is memorize | stored.

  The frequency multiplier control unit 11b outputs a spread spectrum clock signal having a frequency that is twice the frequency of the spread spectrum clock signal output from the spread spectrum clock generator 1 (where k is a positive integer). The frequency multiplier 13 is controlled.

  The pulse pattern generation unit control means 11c generates a pulse pattern signal having a desired repetitive pattern from the spread spectrum clock signal multiplied in frequency by the frequency multiplication unit 13 and the data signal input from the outside. The generator 14 is controlled.

  The frequency multiplication unit 13 controls the spread spectrum clock signal having a frequency that is k times the frequency of the spread spectrum clock signal generated by the spread spectrum clock generator 1 (for example, 20 times the frequency) under the control of the control unit 11. Output.

  The pulse pattern generation unit 14 is controlled by the control unit 11, and the spread spectrum clock signal frequency doubled by the frequency multiplication unit 13 and a data signal (low level voltage: “0” and high level) input from the outside. Voltage: “1” data) is input, and a pulse pattern signal having a desired repetition pattern obtained by modulating the data signal with the spread spectrum clock signal is generated. For example, when used as a pattern generator of an error rate measuring apparatus that performs a margin test of a device under test, the pattern generator 14 uses a spread spectrum clock signal as a pulse pattern signal (test signal) of a known pattern input to the device under test. A programmable PRBS (Pseudo-random bit sequence) pattern, a continuous pattern of 0 and 1 as a repetitive signal, and a programmable pattern including an arbitrary pattern are generated.

  When the spread spectrum clock signal is generated from the spread spectrum clock generator 1 of the pattern generator 200 configured as described above by any spread method from the down spread method, the center spread method, and the upper spread method, The setting unit 15 selects the spread method (down spread method, center spread method, or upper spread method) and sets the modulation frequency, carrier frequency, and modulation degree.

(Division operation example)
Here, with reference to FIG. 3, for example, an operation for generating a modulation frequency of 33 kHz defined in Gen2 of the PCI Express standard using a reference clock signal fixed at 5 MHz will be described. In the prior art, in order to obtain a natural number that is a frequency division ratio required by the DAC and an even number, a frequency near the modulation frequency of 33 kHz can be obtained as an even number in the vicinity of the 151 frequency division, for example, a frequency division of 152, The modulation frequency is 32.8947... KHz, and a deviation of about 0.3% occurs with respect to the prescribed modulation frequency of 33 kHz. On the other hand, for example, when generating a modulation frequency of 31.25 kHz as defined in Gen1 of the PCI Express standard from a reference clock signal fixed at 5 MHz, since the fraction is not obtained at 160 division as described above, the reference clock signal is not generated. Since a triangular wave frequency can be generated from a single frequency with a single frequency division ratio, a spread spectrum clock signal may be generated by a conventional technique.

As a premise, in this example, n = 2, the number of occurrences of the first triangular wave having the first division ratio D ₁ is R ₁ and the number of occurrences of the second triangular wave having the second division ratio D _2. A set of waveforms is formed by combining (R ₁ + R ₂ ) triangular waves each consisting of R ₂ times. Further, the frequency of the reference clock signal is fc, the modulation frequency defined by the communication standard, that is, the triangular wave frequency is fd, and the average of a set of waveforms whose frequencies are averaged by a combination of the first triangular wave and the second triangular wave Let the frequency be Δfd. The frequency division ratio calculation means 11a uses the following equation (2) to calculate the first frequency division ratio D ₁ and the second frequency division ratio D so that the difference between Δfd and fd is within 0.1%. ₂ and the first triangular wave generation frequency R ₁ and the second triangular wave generation frequency R ₂ are respectively calculated to generate a division ratio calculation signal, which is included in the modulation unit 12 and the modulation generation unit 12e. Output to the triangular wave generator 12f. If the difference between the frequency fd of the triangular wave and the average frequency Δfd is within 0.1%, the reliability of the measurement result can be sufficiently ensured. In the present invention and the following formula (2), the symbol of ≒ includes the symbol of = indicating coincidence.

fd≈Δfd = fc / ((D ₁ × R ₁ + D ₂ × R ₂ ) / (R ₁ + R ₂ )) (2)
However, D ₂ > D ₁ ,
D ₁ and D ₂ are even numbers,
R ₁ and R ₂ are positive integers,
D ₂ = D ₁ + (2 × i) (i = 1 to any integer from 1 to 5)

For example, the frequency of the reference clock signal is fc = 5 MHz, and the frequency of the triangular wave is fd = 33 kHz. Here, the frequency division ratio calculating means 11a uses the above equation (2) to set the first frequency division ratio so that the difference between the average frequency Δfd and the triangular wave frequency fd = 33 kHz is within 0.1%. D ₁ , second frequency division ratio D ₂ , first triangular wave generation frequency R ₁ and second triangular wave generation frequency R ₂ are calculated. As calculation processing, since fc / fd is at 151 near estimates that the second division ratio _{D 2} there is a desired value to an even number in the vicinity of 151, for example, after determining a _D 2 = 152, the D ₁ , R ₁ , and R ₂ are respectively determined by a method of trying based on the condition of Expression (2). Thus, for example, in the case of i = 1, the first division ratio _{D 1} week 150 minutes, once occurrences _{R 1} once the first triangular wave, a second division ratio _{D 2} peripheral 152 minutes, A frequency division ratio calculation signal is generated by calculating that the number of occurrences R2 of the _second triangular wave is 3 times, and output to the triangular wave generation unit 12f included in the modulation unit 12 and the modulation generation unit 12e.

Then, the triangular wave generation part 12f has a dividing ratio D ₁ of the first the calculated and peripheral 150 minutes, and once the occurrences R ₁ once the first triangular wave, the second division ratio D ₂ Is divided by 152, and the number of occurrences R of the _second triangular wave R is calculated three times to calculate the average frequency Δfd. Specifically, using the above-described equation (2), Δfd = 5 MHz / ((150 × 1 + 152 × 3) / (1 + 3)). As a result, the average frequency Δfd is Δfd = 33.00330033... KHz. This is a deviation of about 0.01% with respect to the prescribed modulation frequency of 33 kHz, and the modulation frequency deviation can be sufficiently reduced. By measuring the device under test using this spread spectrum clock signal, it is possible to minimize the error in the measurement result.

Also, and the first triangular wave with a frequency division ratio D ₁ of the i = 1 if the first, the difference between the frequency division ratio of the second triangular wave having a second frequency division ratio D ₁ is 2 and the difference between the minimum Therefore, the frequency fluctuation of a set of waveforms combining these triangular waves is minimized, and a triangular wave with a small amount of jitter can be generated. On the other hand, i = 5 If a first triangular wave with a first frequency division ratio D _1, the difference of the frequency division ratio of the second triangular wave having a second frequency division ratio D ₁ is 10, and the error rate This is a range in which a triangular wave with a jitter amount that does not hinder the use of the signal as a spread spectrum clock signal of the measuring apparatus can be generated. i = is possible 6 can be operated using the above values, the second triangular wave having a first triangular wave with a first frequency division ratio D _1, the second division ratio D ₁ When the difference in the frequency division ratio becomes large, the fluctuation of the frequency when these triangular waves are combined to form a set of waveforms increases the amount of jitter, so it is desirable that i = 5 or less.

Incidentally, in this dividing operation example, in order to simplify the description, the first division ratio D ₁ of the peripheral 150 minutes, once occurrences R ₁ once the first triangular wave is calculated, the second minute the division ratio _{D 2} peripheral 152 minutes, have been described occurrences _{R 2} times the second triangular wave as three times, the first division ratio _{D 1} of the peripheral 150 minutes, the first triangular wave of occurrences _{R 1} times eight times, the second division ratio D ₂ peripheral 152 minutes, the occurrence count R ₂ times the second triangular wave if 25 times, can generate the modulation frequency that matches the 33kHz prescribed modulation frequency. In this case, the second generation of the division ratio D ₂ after repeating the first occurrence of the division ratio D ₁ 8 times may be repeated 25 times, the first division ratio D ₁ once second frequency dividing ratio as a whole a first frequency dividing ratio generation of D ₁ is 8 second division ratio D ₂ generated for the times by repeating 3-4 times the occurrence of D ₂ each generate Is preferably 25 times.

Further, in the above example, the first frequency dividing ratio D _1, has been described in two division ratios in combination with a second division ratio D _2, it is not limited to a combination of the two, 3 A combination of two or more division ratios, a first division ratio D ₁ ,..., An nth division ratio D _n, and these first,. The number of occurrences of a plurality of triangular waves may be a combination of n (where n is an integer of 3 or more) triangular waves each having R ₁ times,..., R _n times. It should be noted that the number of occurrences of the triangular wave having the first frequency division ratio D ₁ is R ₁ times, the number of generations of the triangular wave having the _second frequency division ratio D ₂ is R ₂ times, and has the third frequency division ratio D ₃ . The triangular waves are combined so that each triangular wave is paired so that the number of triangular waves generated is R ₃ times,..., And the number of triangular waves having the _nth frequency division ratio D _n is R _n times.

Incidentally, as described above, a plurality of a set of waveforms that combine a triangular wave, the first triangular wave of occurrences R ₁ once with peripheral 150 minutes, for example, as a first division ratio D ₁ of the single triangular wave, The generation frequency R ₂ of the second triangular wave having a frequency division of 152 as the _second frequency division ratio D ₂ is generated as three triangular waves, so that a sufficient deviation from the modulation frequency of 33 kHz specified in the communication standard can be obtained. Can be small. However, as shown in FIG. 3, the maximum voltage of the triangular wave having the frequency of the first triangular wave having a frequency division of 150 is the maximum voltage of the triangular wave having the frequency of the frequency of the second triangular wave having a frequency of 152 divided. Since the amplitude is lower than the voltage, the amplitude when these triangular waves are combined into a set of waveforms is reduced, resulting in an undermodulated spectrum of the spread spectrum clock signal. When measuring an object to be measured using this under-modulated spread spectrum clock signal, a margin test is performed with a small amount of modulation relative to the amount of modulation specified in the standard, resulting in an error in the measurement result and a defective product. May be determined as non-defective.

  Therefore, in this embodiment, an operation example is described in which the spectrum spread clock signal is converted into a properly modulated spectrum by solving the problem that the amplitude of a set of waveforms combining the above-described triangular waves is reduced. In the apparatus to which the present invention is applied, any one of a first amplitude correction operation example, a second amplitude correction operation example, and a third amplitude correction operation example, which will be described later, is selected by design or setting. Behave as if

(First amplitude correction operation example)
A first amplitude correction operation example will be described. Amplitude correction means 11e, as shown in FIG. 4, when the second division ratio _{D 2} is first greater than the division ratio _{D 1,} triangular wave frequency dividing ratio is _small, D 2> _{D 1} if _{D 1} Amplitude correction is performed using the following equation (3) for a predetermined amount of displacement of the amplitude per 1 bit before correction of the first triangular wave having. Note that a displacement of a predetermined amount of amplitude per 1 bit of the second triangular wave having the second frequency division ratio D ₂ is V _a , and per 1 bit after correction of the first triangular wave having the first frequency division ratio D _1. Let V _b be a predetermined amount of displacement of the amplitude. V _Δ is the maximum voltage of a triangular wave for obtaining a desired modulation degree. V _a is expressed as V _a = 2 × V _Δ / D ₂ from the above-described equation (1).

_{V b = V a × D 2} / D 1 ... Equation (3)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂

For a set of waveforms obtained by combining a plurality of triangular waves, for example, a first triangular wave having a frequency division of 150 as a _first frequency division ratio D ₁ is a triangular wave having a single frequency of generation, and a second frequency division ratio D _2. It is assumed that a triangular wave having three times the number of occurrences of the second triangular wave having a frequency of 152 is generated. The maximum value V _delta, for example 1V triangular wave voltage, the second triangular wave displacement V _a predetermined amount of amplitude per 1bit of having a second division ratio D ₂ are, 1V from the above equation (1) the becomes 0.013157 ··· V was divided equally 76 is the number of one-half of the second division ratio _{D 2} second triangular wave division ratios 152 with. Here, using the above equation (3), the displacement of a predetermined amount of amplitude per bit after the correction of the first triangular wave having the first frequency division ratio D ₁ is V _b = 0.013157... V * (152/150) = 0.0133333 ... V * 1.013333 ... = 0.0133333 ... V It is calculated. Only when the first triangular wave having a frequency division of 150 as the _first frequency division ratio D ₁ is generated once, the displacement of the predetermined amount of amplitude per bit after correction V _b = 0.0133333 · .. Correct to V. As a result of this correction, the maximum value of the voltage of the first triangular wave having a frequency of 150 divided as the _first frequency division ratio D ₁ is V _b = 0.013333. 0.99999999 ... V. Thus, the maximum value of the triangular wave voltage with the frequency of generation of the first triangular wave having the frequency division of 150 as the _first frequency division ratio D1 is the maximum value of the triangular wave voltage for obtaining a desired modulation degree. is corrected to a very close voltage 1V is V _delta, while reducing the modulation frequency deviation from the prescribed modulation frequency, it is possible to generate a triangular wave having a desired modulation factor.

(Second amplitude correction operation example)
A second amplitude correction operation example will be described. Amplitude correction means 11e, as shown in FIG. 5, when the second division ratio D ₂ is first greater than the division ratio D _1, corrected for only bit in the apex of the triangular wave frequency dividing ratio is small I do. D _{2> D 1} if the first pre-correction of the amplitude of a predetermined amount of displacement per 1bit triangular wave with _{D 1,} and, only to bit in a first vertex of the division ratio _{D 1,} below Amplitude correction is performed using equation (4). Note that a displacement of a predetermined amount of amplitude per 1 bit of the second triangular wave having the second frequency division ratio D ₂ is V _a , and per 1 bit after correction of the first triangular wave having the first frequency division ratio D _1. Let V _d be a predetermined amount of displacement of the amplitude of. V _Δ is the maximum voltage of a triangular wave for obtaining a desired modulation degree. V _a is expressed as V _a = 2 × V _Δ / D ₂ from the above-described equation (1).

_{V d = V a × ((} (D 2 -D 1) / 2) +1) ... Equation (4)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂

For a set of waveforms obtained by combining a plurality of triangular waves, for example, a first triangular wave having a frequency division of 150 as a _first frequency division ratio D ₁ is a triangular wave having a single frequency of generation, and a second frequency division ratio D _2. It is assumed that a triangular wave having three times the number of occurrences of the second triangular wave having a frequency of 152 is generated. Further, the maximum value V _Δ of the triangular wave voltage for obtaining a desired modulation degree is, for example, 1V, and a displacement Va of _a predetermined amount of amplitude per 1 bit of the second triangular wave having the second frequency division ratio D ₂ is: 0.013157 ··· V obtained by equally dividing the 1V from the above equation (1) in the second frequency dividing ratio second number a is 76 one-half of the frequency dividing ratio 152 of the triangular wave with _{D 2} It becomes. Here, using the above equation (4), the displacement of a predetermined amount of amplitude per bit after correction of the first triangular wave having the first frequency division ratio D ₁ is V _d = 0.013157... V X (((152-150) / 2) +1) = 0.026315... V is calculated. Then, the first number of occurrences is one of the triangular wave of the triangular wave with a 150 division first as a frequency division ratio D _1, and, for bit only at the first vertex of the division ratio D _1, Correction is made so that the displacement V _d = 0.026315... V of a predetermined amount of amplitude per bit after correction. With this correction, the maximum value of the voltage of the first triangular wave having the first frequency division ratio D ₁ of 150 divided by 150 is V _a = 0.013157. to the 0.973684 ··· _V, addition of V d = 0.026315 ··· V, a 0.999999 ··· V. Thus, the maximum value of the triangular wave voltage with the frequency of generation of the first triangular wave having the frequency division of 150 as the _first frequency division ratio D1 is the maximum value of the triangular wave voltage for obtaining a desired modulation degree. it is corrected to a very close voltage 1V is V _delta, while reducing the modulation frequency deviation from the prescribed modulation frequency, and it is possible to generate a triangular wave having a desired modulation factor.

(Third amplitude correction operation example)
Next, a third amplitude correction example will be described. Amplitude correction means 11e, as shown in FIG. 6, the second division ratio D ₂ is when the first larger division ratio D _1, the first triangular wave with a first frequency division ratio D ₁ generated Each of the triangular waveforms having the number of times R ₁ and the second triangular wave having the second frequency division ratio D ₂ having the number of occurrences R ₂ is the triangular wave having the number of occurrences R _2. For all of the bits, amplitude correction is performed using the following equation (5). It should be noted that the displacement of a predetermined amount of amplitude per bit of the second triangular wave having the second frequency division ratio D ₂ is V _a , and the number of occurrences of the first triangular wave having the first frequency division ratio D ₁ is R _1. times of the triangular wave, a predetermined amount of displacement of the amplitude of each of the second bit after division ratio the number of occurrences of the second triangular wave with D ₂ is the entire waveform as one set in combination as a triangular wave of _twice R correction Let V _f . V _Δ is the maximum voltage of a triangular wave for obtaining a desired modulation degree. V _a is expressed as V _a = 2 × V _Δ / D ₂ from the above-described equation (1).

_{V f = V a × D 2} × (R 1 + R 2) / (D 1 × R 1 + D 2 × R 2) ... (5)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂

For a set of waveforms obtained by combining a plurality of triangular waves, for example, a first triangular wave having a frequency division of 150 as a _first frequency division ratio D ₁ is a triangular wave having a single frequency of generation, and a second frequency division ratio D _2. It is assumed that a triangular wave having three times the number of occurrences of the second triangular wave having a frequency of 152 is generated. Further, the maximum value V _Δ of the triangular wave voltage for obtaining a desired modulation degree is, for example, 1V, and a displacement Va of _a predetermined amount of amplitude per 1 bit of the second triangular wave having the second frequency division ratio D ₂ is: 0.013157 ··· V obtained by equally dividing the 1V from the above equation (1) in the second frequency dividing ratio second number a is 76 one-half of the frequency dividing ratio 152 of the triangular wave with _{D 2} It becomes. Here, using the above equation (5), the displacement of a predetermined amount of the amplitude of each bit of the entire corrected waveform is V _f = 0.013157... V × 152 × (1 + 3) / (150 × 1 + 152 × 3) = 0.013333... V × 1.00330033... = 0.013201. The number of occurrences of the first triangular wave having a frequency division of 150 as the _first frequency division ratio D1 is one triangular wave, and the number of occurrences of the second triangular wave having the frequency division of 152 as the _second frequency division ratio D2. Is a three-time triangular wave, and for each bit of the entire waveform that is a combination of these triangular waves, a predetermined amount of displacement V _f = 0.013201 of the amplitude of each bit of the entire corrected waveform -Correct as V. By this correction, the maximum value of the waveform voltage due to a predetermined amount of displacement of the amplitude of each bit of the entire corrected waveform is V _f in the first triangular wave having a frequency division of 150 as the _first frequency division ratio D _1. = 0.013201 ··· V 75 times the .990099 · · · V, in the second number of occurrences is 3 times of the triangular wave of the triangular wave with a 152 division second as a frequency division ratio _{D 2 V f} = 0.013201 ... V, which is 1.003300 ... V which is 76 times larger. Here, the average voltage of the whole waveform made by combining these triangular waves is verified. When this average voltage is calculated by the equation (0.990099... V × 3 times +1.0003300... V × 1 time) / 4, the average voltage is 0.993399. As a result, the first triangular wave having the frequency division of 150 as the _first frequency division ratio D1 has a maximum frequency of one triangular wave and the frequency division of 152 as the _second frequency division ratio D2. The maximum value of the triangular wave voltage of which the number of occurrences of the second triangular wave is 3 times is corrected to a voltage very close to 1 V, which is the maximum value V _Δ of the triangular wave voltage for obtaining a desired degree of modulation. It is possible to generate a triangular wave having a desired modulation degree while reducing a modulation frequency shift with respect to the modulation frequency.

  As described above, according to the spread spectrum clock generator and the spread spectrum clock generation method of the present invention, the pulse pattern generation device and the pulse pattern generation method for generating a desired pattern signal using the spread spectrum clock signal and the data signal, Since the error in the amplitude of the output triangular wave is corrected, the spectrum spread clock signal becomes a spectrum modulated with the correct amplitude, and the measurement result is obtained by measuring the device under test using this spread spectrum clock signal. It becomes possible to improve the reliability.

[Processing operation]
Next, a processing operation related to the spread spectrum clock generation in the pulse pattern generation device 200 will be described with reference to FIG. In addition, the description which overlaps with the above-mentioned apparatus is abbreviate | omitted suitably.

(Division processing example)
First, a first division ratio D _1, as an example the case of a combination of the two frequency division ratio of the second division ratio D _2, with reference to FIG. 7 for dividing the processing operations of the spread-spectrum clock generator While explaining. First, the modulation frequency (triangular wave frequency fd) set by the setting unit 15 is set (S301).

  Next, whether the set modulation frequency (triangular wave frequency fd) is a single division ratio from the frequency of the reference clock signal fc, that is, whether the number of division ratios is 1 and the triangular wave frequency fd can be generated. Is determined (S302). As a criterion for judgment, when the frequency fc of the reference clock signal is divided by the modulation frequency (triangular wave frequency fd), when a fraction is not obtained and becomes an even number, the frequency of the triangular wave is 1 when the number of division ratios is 1. It is determined that fd can be generated. On the other hand, when dividing by the modulation frequency (triangular wave frequency fd), if a fraction occurs or even if a fraction is not obtained, the number of division ratios is 1, and the triangular wave frequency fd cannot be generated. Is determined.

  When the triangular wave frequency fd can be generated with a single frequency division ratio, the triangular wave frequency fd is generated with a single frequency dividing ratio (S306). Then, a spread spectrum clock signal is generated based on the frequency fd of the generated triangular wave (S307).

On the other hand, when the number of division ratios is 1 and the triangular wave frequency fd cannot be generated, the above equation (2) is set so that the difference between the triangular wave frequency fd and the average frequency Δfd is within 0.1%. Are used to calculate the first frequency division ratio D ₁ , the second frequency division ratio D ₂ , the number of occurrences of the first triangular wave R ₁ , and the number of occurrences of the second triangular wave R ₂ (S 303). ).

Next, the calculated first frequency division ratio D ₁ , first triangular wave generation number R ₁ , second frequency division ratio D _2, and second triangular wave generation number R ₂ are obtained. And frequency division is performed (S304).

  Next, a spread spectrum clock signal is generated by frequency modulating the reference clock signal based on the average frequency Δfd obtained by frequency division (S305).

  In the apparatus to which the present invention is applied, any one of a first amplitude correction processing example, a second amplitude correction processing example, and a third amplitude correction processing example, which will be described later, is selected according to design or setting. Behave as if

(First amplitude correction processing example)
A first amplitude correction processing example (first amplitude correction step) will be described. When the second division ratio _{D 2} is first greater than the division ratio _{D 1,} frequency waveform division ratio is _small, D 2> of the first triangular wave with _{D 1} if _{D 1} uncorrected per 1bit With respect to the displacement of a predetermined amount of amplitude, the displacement _Vb of the predetermined amount of amplitude per 1 bit after correction is obtained and corrected using the above-described equation (3) (S308).

(Second example of amplitude correction processing)
Next, a second amplitude correction processing example (second amplitude correction step) will be described. When the second division ratio D ₂ is first greater than the division ratio D _1, performs bit only for correction in the apex of the dividing ratio is small waveform. D _{2> D 1} if the first pre-correction of the amplitude of a predetermined amount of displacement per 1bit triangular wave with _{D 1,} and, only to bit in a first vertex of the division ratio _{D 1,} above correcting seeking displacement _{V d} of a predetermined amount of amplitude per 1bit corrected using the formula (4) (S309).

(Third amplitude correction processing example)
Next, a third amplitude correction processing example (third amplitude correction step) will be described. When the second division ratio D ₂ is first greater than the division ratio D _1, the first occurrence number R ₁ of times of the triangular wave of the triangular wave with a first frequency division ratio D _1, second division The number of occurrences of the second triangular wave having the ratio D ₂ is a triangular wave with R ₂ times, and the above formula (5) is applied to all the bits before correction of the entire waveform that is a combination of these triangular waves. A predetermined amount of displacement _Vf of the amplitude per bit after correction is obtained and corrected (S310).

Further, in the above example, the first frequency dividing ratio D _1, has been described in two division ratios in combination with a second division ratio D _2, it is not limited to a combination of the two, 3 A combination of two or more division ratios, a first division ratio D ₁ ,..., An nth division ratio D _n, and these first,. The number of occurrences of a plurality of triangular waves may be a combination of n (where n is an integer of 3 or more) triangular waves each having R ₁ times,..., R _n times. It should be noted that the number of occurrences of the triangular wave having the first frequency division ratio D ₁ is R ₁ times, the number of generations of the triangular wave having the _second frequency division ratio D ₂ is R ₂ times, and has the third frequency division ratio D ₃ . The triangular waves are combined so that each triangular wave is paired so that the number of triangular waves generated is R ₃ times,..., And the number of triangular waves having the _nth frequency division ratio D _n is R _n times.

DESCRIPTION OF SYMBOLS 1 ... Spread spectrum clock generator 11 ... Control part 11a ... Frequency division ratio calculation means 11b ... Frequency multiplication part control means 11c ... Pulse pattern generation part control means 11d ... Modulation part control means 11e ... Amplitude correction means 12 ... Modulation part 12a ... frequency divider 12b ... phase comparator 12c ... charge pump 12d ... loop filter 12e ... modulation generator 12f ... triangular wave generator 12g ... adder 12h ... voltage controlled oscillator 13 ... frequency multiplier 14 ... pulse pattern generator 15 ... Setting unit 16 ... display unit 17 ... storage unit 200 ... pulse pattern generator

Claims (14)

In order to generate a spread spectrum clock signal (SSC) defined by the communication standard , a reference clock signal having a predetermined frequency controlled by the control unit (11) is used as a modulation frequency defined by the communication standard. In a spread spectrum clock generator (1) having a modulation section (12) for generating a spread spectrum clock signal by frequency modulation based on a triangular wave having
The frequency of the reference clock signal fc, the frequency of the triangular wave and fd, first frequency dividing ratio a first number of occurrences of the triangular wave R ₁ times with D _1, a second having a second division ratio D ₂ When a set of waveforms is formed by combining (R ₁ + R ₂ ) triangular waves with the number of occurrences of the triangular wave of R ₂ times, an average frequency averaged as the set of waveforms is Δfd, and the triangular wave The first frequency division ratio D ₁ , the second frequency division ratio D _2, and the number of occurrences of the first triangular wave so that the difference between the frequency fd and the average frequency Δfd is within 0.1%. Frequency division ratio calculating means (11a) for calculating R ₁ times and the number of occurrences R ₂ of the second triangular wave, respectively,
The modulation unit is configured to calculate the first frequency division ratio D ₁ , the second frequency division ratio D ₂ , the number of occurrences R ₁ of the first triangular wave, and the number of occurrences R of the second triangular wave. _The spread spectrum clock signal is generated by frequency-modulating the reference clock signal based on the set of waveforms obtained by the frequency division ratio and the number of occurrences respectively set twice. Spread spectrum clock generator. In order to generate a spread spectrum clock signal (SSC) defined by the communication standard , a reference clock signal having a predetermined frequency controlled by the control unit (11) is used as a modulation frequency defined by the communication standard. In a spread spectrum clock generator (1) having a modulation section (12) for generating a spread spectrum clock signal by frequency modulation based on a triangular wave having
The frequency of the reference clock signal is fc, the frequency of the triangular wave is fd, the number of occurrences of the first triangular wave having the first frequency division ratio D ₁ is R ₁ time,..., The nth frequency division ratio D _n. The number of occurrences of the n-th triangular wave having R _n is (R ₁ +... + R _n ) and a set of waveforms combining a triangular wave (n is an integer of 2 or more). The average frequency averaged as the waveform is Δfd, and the first frequency division ratio D ₁ ,... Is set so that the difference between the frequency fd of the triangular wave and the average frequency Δfd is within 0.1%. the frequency dividing ratio D _n of the n, the first triangular wave of occurrences R ₁ times, ... the frequency division ratio calculation means for calculating the number of occurrences R _n times of the triangular wave of the first n respectively ( 11a)
The modulation unit is configured to calculate the first frequency division ratio D ₁ ,..., The nth frequency division ratio D _n, and the number of occurrences of the first triangular wave R ₁ time,. The spread spectrum clock signal is obtained by frequency-modulating the reference clock signal based on the set of waveforms obtained by the frequency division ratio and the number of occurrences set by the number of occurrences Rn of the _nth triangular wave, respectively. A spread spectrum clock generator characterized by generating The frequency division ratio calculating means calculates the first frequency division ratio D ₁ , the second frequency division ratio D _2, and the number of occurrences of the first triangular wave R ₁ using the following formula (2). Times, and the number of occurrences R ₂ of the second triangular wave,
The modulation unit is configured to calculate the first frequency division ratio D ₁ , the second frequency division ratio D ₂ , the number of occurrences R ₁ of the first triangular wave, and the number of occurrences R of the second triangular wave. _The spectrum spread is performed by dividing the frequency by the frequency division ratio set by the number of times and the number of occurrences, and modulating the frequency based on the average frequency obtained by using the calculation formula of the following formula (2). The spread spectrum clock generator of claim 1, wherein the clock signal is generated.
fd≈Δfd = fc / ((D ₁ × R ₁ + D ₂ × R ₂ ) / (R ₁ + R ₂ )) (2)
However, D ₂ > D ₁ ,
D ₁ and D ₂ are even numbers,
R ₁ and R ₂ are positive integers,
D ₂ = D ₁ + (2 × i) (i = 1 to any integer from 1 to 5) The control unit includes amplitude correction means (11e),
When said second frequency dividing ratio D ₂ the first of the larger division ratio D _1, wherein the amplitude correcting means, per 1bit the second triangular wave having the second frequency dividing ratio D ₂ of the amplitude A predetermined amount of displacement is V _a , a predetermined amount of amplitude displacement per bit after correction of the first triangular wave having the first frequency division ratio D ₁ is V _b , and a triangular wave for obtaining a desired modulation degree is obtained. when the maximum voltage is V _delta, with respect to the displacement of a predetermined amount of the amplitude of the per 1bit before correction of the first triangular wave with a frequency division ratio D ₁ of the first, using a formula of the following formula (3) 4. The spread spectrum clock generator according to claim 1, wherein a predetermined amount of displacement _Vb of amplitude per bit after correction is obtained and corrected.
_{V b = V a × D 2} / D 1 ... Equation (3)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂ The control unit includes amplitude correction means (11e),
When said second frequency dividing ratio D ₂ the first of the larger division ratio D _1, wherein the amplitude correcting means, per 1bit the second triangular wave having the second frequency dividing ratio D ₂ of the amplitude A predetermined amount of displacement is V _a , a predetermined amount of amplitude displacement per bit after correction of the first triangular wave having the first frequency division ratio D ₁ is V _d , and a triangular wave for obtaining a desired modulation degree is obtained. when the maximum voltage is V _delta, in the first division ratio D ₁ first uncorrected amplitude of a predetermined amount of displacement per 1bit triangular wave with, and only with respect to bit in the apex, the following 4. The correction according to claim 1, wherein a predetermined amount of displacement V _d of the amplitude per bit after correction is obtained and corrected using a calculation formula of Formula (4). 5. Spread spectrum clock generator.
_{V d = V a × ((} (D 2 -D 1) / 2) +1) ... Equation (4)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂ The control unit includes amplitude correction means (11e),
When said second frequency dividing ratio D ₂ the first of the larger division ratio D _1, wherein the amplitude correcting means, per 1bit the second triangular wave having the second frequency dividing ratio D ₂ of the amplitude Generation of a first triangular wave having a predetermined amount of displacement V _a , _a first triangular wave having the first frequency division ratio D ₁ of R _{1 and a} second triangular wave having the second frequency division ratio D ₂ A predetermined amount of displacement of the amplitude of each bit after correction of the entire waveform combined as a triangular wave with R ₂ times is set as V _f , and the maximum voltage of the triangular wave for obtaining a desired modulation degree is set as V _Δ . In this case, a predetermined amount of displacement _Vf of the amplitude of each bit after correction of the entire waveform is obtained and corrected for all of the bits before correction of the entire waveform using the following formula (5). The spread spectrum clock generator according to any one of claims 1 and 3.
_{V f = V a × D 2} × (R 1 + R 2) / (D 1 × R 1 + D 2 × R 2) ... (5)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂ In order to generate a spread spectrum clock signal (SSC) defined in a communication standard , a reference clock signal having a predetermined frequency is frequency-modulated based on a triangular wave having a modulation frequency defined in the communication standard. In a spread spectrum clock generation method for generating a spread spectrum clock signal,
The frequency of the reference clock signal fc, the frequency of the triangular wave and fd, first frequency dividing ratio a first number of occurrences of the triangular wave R ₁ times with D _1, a second having a second division ratio D ₂ When a set of waveforms is formed by combining (R ₁ + R ₂ ) triangular waves with the number of occurrences of the triangular wave of R ₂ times, an average frequency averaged as the set of waveforms is Δfd, and the triangular wave The first frequency division ratio D ₁ , the second frequency division ratio D _2, and the number of occurrences of the first triangular wave so that the difference between the frequency fd and the average frequency Δfd is within 0.1%. A frequency division ratio calculating step (S303) for calculating R ₁ times and the number of occurrences R ₂ of the second triangular wave, respectively;
The calculated first frequency division ratio D ₁ , second frequency division ratio D ₂ , first triangular wave generation number R ₁ , and second triangular wave generation number R ₂ , respectively. A frequency dividing step (S304) for dividing by the set frequency dividing ratio and the number of occurrences;
A spread spectrum clock signal generating step (S305) for generating the spread spectrum clock signal by frequency-modulating the reference clock signal based on the set of obtained waveforms; How it occurs. In order to generate a spread spectrum clock signal (SSC) defined in a communication standard , a reference clock signal having a predetermined frequency is frequency-modulated based on a triangular wave having a modulation frequency defined in the communication standard. In a spread spectrum clock generation method for generating a spread spectrum clock signal,
The frequency of the reference clock signal is fc, the frequency of the triangular wave is fd, the number of occurrences of the first triangular wave having the first frequency division ratio D ₁ is R ₁ time,..., The nth frequency division ratio D _n. The number of occurrences of the n-th triangular wave having R _n is (R ₁ +... + R _n ) and a set of waveforms combining a triangular wave (n is an integer of 2 or more). The average frequency averaged as the waveform is Δfd, and the first frequency division ratio D ₁ ,... Is set so that the difference between the frequency fd of the triangular wave and the average frequency Δfd is within 0.1%. the division ratio and D _n of the n, the first triangular wave of occurrences R ₁ times, ... the frequency division ratio calculation step of calculating a number of occurrences R _n times of the triangular wave of the first n respectively ( S303)
The calculated first frequency division ratio D ₁ ,..., The nth frequency division ratio D _n , the number of occurrences of the first triangular wave R ₁ time,. A frequency _dividing step (S304) for _{dividing the} frequency by the frequency _dividing ratio and the number of times of occurrence set respectively for the number of times of occurrence Rn;
A spread spectrum clock signal generating step (S305) for generating the spread spectrum clock signal by frequency-modulating the reference clock signal based on the set of obtained waveforms; How it occurs. Using the following equation (2), the first frequency division ratio D ₁ , the second frequency division ratio D ₂ , the number of occurrences R _{1 of the} first triangular wave, and the second triangular wave A frequency division ratio calculating step (S303) for calculating the number of occurrences R ₂ respectively;
The calculated first frequency division ratio D ₁ , second frequency division ratio D ₂ , first triangular wave generation number R ₁ , and second triangular wave generation number R ₂ . A frequency dividing step (S304) for dividing the frequency by the set frequency dividing ratio and the number of occurrences,
A spread spectrum clock signal generating step (S305) for generating the spread spectrum clock signal by performing the frequency modulation based on the average frequency obtained by using the calculation formula of the following formula (2). The spread spectrum clock generation method according to claim 7.
fd≈Δfd = fc / ((D ₁ × R ₁ + D ₂ × R ₂ ) / (R ₁ + R ₂ )) (2)
However, D ₂ > D ₁ ,
D ₁ and D ₂ are even numbers,
R ₁ and R ₂ are positive integers,
D ₂ = D ₁ + (2 × i) (i = 1 to any integer from 1 to 5) When said second frequency dividing ratio D ₂ is the division ratio D ₁ greater than the first, a predetermined amount of displacement of amplitude per 1bit the second triangular wave having the second frequency dividing ratio D ₂ V _a , a displacement of a predetermined amount of amplitude per bit after correction of the first triangular wave having the first frequency division ratio D ₁ is V _b , and a maximum voltage of the triangular wave for obtaining a desired modulation degree is V _Δ Then, with respect to the displacement of a predetermined amount of amplitude per 1 bit before correction of the first triangular wave having the first frequency division ratio D1, ₁ bit after the correction using the calculation formula of the following formula (3). The spread spectrum clock according to any one of claims 7 and 9, further comprising a first amplitude correction step (S308) for obtaining and correcting a predetermined amount of displacement _Vb of the per-amplitude. How it occurs.
_{V b = V a × D 2} / D 1 ... Equation (3)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂ When said second frequency dividing ratio D ₂ is the division ratio D ₁ greater than the first, a predetermined amount of displacement of amplitude per 1bit the second triangular wave having the second frequency dividing ratio D ₂ V _a , a displacement of a predetermined amount of amplitude per bit after correction of the first triangular wave having the first frequency division ratio D ₁ is V _b , and a maximum voltage of the triangular wave for obtaining a desired modulation degree is V _Δ when, in the first division ratio D ₁ first uncorrected amplitude of a predetermined amount of displacement per 1bit triangular wave with, and only with respect to bit in the apex, the following calculation formula (4) 10. The method according to claim 7, further comprising a second correction step (S 309) for obtaining and correcting a predetermined amount of displacement V _d of the amplitude per bit after correction using an equation. 2. The spread spectrum clock generation method according to item 1.
_{V d = V a × ((} (D 2 -D 1) / 2) +1) ... Equation (4)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂ When said second frequency dividing ratio D ₂ is the division ratio D ₁ greater than the first, a predetermined amount of displacement of amplitude per 1bit the second triangular wave having the second frequency dividing ratio D ₂ V _a, the number of occurrences of the first frequency dividing ratio a first triangular wave with D ₁ is R ₁ times the triangular wave, the number of occurrences of the second triangular wave having the second frequency dividing ratio D ₂ is _twice R Correction of the entire waveform when V _f is a displacement of a predetermined amount of amplitude of each bit after correction of the entire waveform combined as a triangular wave and V _Δ is a maximum voltage of the triangular wave for obtaining a desired modulation degree. A third amplitude correction step for obtaining and correcting a predetermined amount of displacement V _f of the amplitude of each bit after correction of the entire waveform by using the following equation (5) for all the previous bits. The spectrum according to any one of claims 7 and 9, further comprising S310). Lamb diffusion clock generation method.
_{V f = V a × D 2} × (R 1 + R 2) / (D 1 × R 1 + D 2 × R 2) ... (5)
However, D ₂ > D ₁ ,
V _a = 2 × V _Δ / D ₂   A pulse pattern generator (200) for generating a pulse pattern signal using a spread spectrum clock signal generated by the spread spectrum clock generator according to any one of claims 1 to 6. 13. A pulse pattern generation method comprising a step of generating a pulse pattern signal using a spread spectrum clock signal generated by the spread spectrum clock generation method according to any one of claims 7 to 12.

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