Skew generating device and skew generating method

Abstract

To allow a skew amount of a PAM signal to be changed without performing a mechanical operation.SOLUTION: A skew generation device 1 includes: a clock oscillator 2 for oscillating and outputting a clock signal; and a plurality of signal generators 4A and 4B for outputting positive signals and negative signals having mutually opposite phases at timing of a signal obtained by IQ-modulating the clock signal and adjusting a phase angle. The plurality of signal generators 4A and 4B operate synchronously, control by allocating an integer unit of UI of a skew amount to be set to a transmission timing shift and allocating a fractional unit to IQ modulation, and combine the positive signals and the negative signals at the same desired amplitude ratio and output the combined signals.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a skew generator and a skew generation method for generating a skew in a signal that is the basis for generating a ternary or higher PAM signal. [Background technology]

[0002] While increasing the modulation rate is one way to improve communication speeds, there are limitations to this approach alone due to factors such as the operating speed of semiconductors and loss along the transmission path. Therefore, in recent high-speed serial communications, in addition to increasing modulation rates, a multi-level modulation technique called "PAM" is being used, which transmits multiple bits per symbol by expressing the amplitude direction using multiple gradations. For example, PCIe Gen6 employs 32 Gbaud PAM4, which transmits two bits of information per symbol by expressing the amplitude direction using four levels, achieving a transmission capacity of 64 Gbps with the same frequency bandwidth as 32 Gbps. However, PAM has the disadvantage of significantly degrading the S / N ratio by dividing the amplitude direction into multiple parts, which places stricter requirements on distortion, reflection, and noise.

[0003] There are several methods for generating PAM signals, including combining multiple NRZ signals. Figure 9 shows the simplest example, a PAM4 signal configuration, where the two original NRZ signals are called the MSB and LSB. In the example shown in Figure 9, the LSB is attenuated by a desired amount using attenuator 21, and then combined with the MSB using combiner (power divider) 22 to generate a combined signal (PAM4 signal). This method requires that the arrival timing of the MSB and LSB be synchronized. However, because the original signal sources and transmission paths are different, there is a possibility of timing discrepancy (skew). Since the skew between the MSB and LSB significantly distorts the combined PAM4 waveform, a measurement system must have a mechanism to adjust for this. There may also be demand for intentionally introducing skew to evaluate the impact of MSB / LSB skew or for margin testing. Patent Document 1 below discloses a technology related to skew adjustment.

[0004] Incidentally, one method for varying the skew between the MSB and LSB is to use a mechanical delay adapter, which is a device that mechanically varies the line length of a coaxial line. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-096760 Summary of the Invention [Problem to be solved by the invention]

[0006] However, because mechanical delay adapters are operated mechanically, they have limitations in repeatability, resolution, and variable range, making them unsuitable for automation. While there are types with wider variable ranges, there is a trade-off between variable range and resolution, making it difficult to achieve both. Furthermore, simply inserting a mechanical delay adapter affects transmission characteristics, so the person performing the measurement must carefully examine the measurement results to determine whether the effect is due to the mechanical delay adapter or skew. While the effects of the frequency characteristics and insertion loss of a mechanical delay adapter can be largely eliminated by performing calibration at the end face of the mechanical delay adapter, the calibration end face changes depending on the operation of the mechanical delay adapter, making it difficult to precisely maintain phase calibration.

[0007] Therefore, the present invention has been made in consideration of the above problems, and aims to provide a skew generating device and a skew generating method that can vary the amount of skew of a PAM signal without performing any mechanical operation. [Means for solving the problem]

[0008] In order to achieve the above object, a skew generating device according to claim 1 of the present invention comprises: a clock oscillator 2 that oscillates and outputs a clock signal; The clock signal is IQ modulated and a positive signal and a negative signal of opposite phases are output at the timing of the signal whose phase angle is adjusted. The IQ modulators 13A and 13B, the pattern generating units 14A and 14B, and the control units 15A and 15B are included. Multiple Signal Generators 4A, 4B and The plurality of signal generators operate in synchronization with each other, and are configured to shift the transmission timing of the signals by an integer unit of UI of the set skew amount. to , the fractional unit of the UI of the set skew amount is applied to IQ modulation. each Allocation 、 The control unit of the plurality of signal generators determines the necessary skew amount when the skew amount in UI units is set. IQ modulation amount and The amount of the transmission timing shift is divided into the IQ modulator and the pattern generator. Controlling at least one of the It is characterized by multiplexing positive signals and negative signals at the same desired amplitude ratio to output a PAM signal with three or more levels.

[0009] A skew generating device according to claim 2 of the present invention comprises a clock oscillator 2 that oscillates and outputs a clock signal; The clock signal is IQ modulated and the phase angle is adjusted to output the upper positive and negative signals in opposite phases. The first IQ modulator 13A, the first pattern generating unit 14A, and the first control unit 15A are included. a first signal generator 4A; The clock signal is IQ modulated and the phase angle is adjusted to output the lower positive and negative signals in opposite phases. The second IQ modulator 13B, the second pattern generating unit 14B, and the second control unit 15B are included. a second signal generator 4B; The first signal generator and the second signal generator operate in synchronization with each other, and a transmission timing shifter is configured to shift the transmission timing of the signal by an integer unit of UI of the set skew amount. to , the fractional unit of the UI of the set skew amount is applied to IQ modulation. each Allocation 、 When the skew amount in units of UI is set, the first control unit divides it into a necessary IQ modulation amount and a transmission timing shift amount and controls the first IQ modulator and the first pattern generation unit. Controlling at least one of the the second control unit, when a skew amount in units of UI is set, controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; The upper positive signal and the lower positive signal, and the upper negative signal and the lower negative signal are multiplexed at the same desired amplitude ratio to output a PAM3 signal.

[0010] A skew generating device according to claim 3 of the present invention comprises a clock oscillator 2 that oscillates and outputs a clock signal; The clock signal is IQ modulated and the phase angle is adjusted to output the positive and negative MSB signals in opposite phases. The first IQ modulator 13A, the first pattern generating unit 14A, and the first control unit 15A are included. a first signal generator 4A; The clock signal is IQ modulated and the phase angle is adjusted to output LSB positive and negative signals in opposite phases. The second IQ modulator 13B, the second pattern generating unit 14B, and the second control unit 15B are included. a second signal generator 4B; The first signal generator and the second signal generator operate in synchronization with each other, and a transmission timing shifter is configured to shift the transmission timing of the signal by an integer unit of UI of the set skew amount. to , the fractional unit of the UI of the set skew amount is applied to IQ modulation. each Allocation 、 When the skew amount in units of UI is set, the first control unit divides it into a necessary IQ modulation amount and a transmission timing shift amount and controls the first IQ modulator and the first pattern generation unit. Controlling at least one of the the second control unit, when a skew amount in units of UI is set, controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; The positive signal of the MSB and the positive signal of the LSB, and the negative signal of the MSB and the negative signal of the LSB are multiplexed at the same desired amplitude ratio to output a PAM4 signal.

[0011] The skew generating device according to claim 4 of the present invention is the skew generating device according to any one of claims 1 to 3, When the skew amount is set in units of time, the skew amount set in the units of time Tobi The method is characterized by multiplying the bit rate by the amount of skew in UI units.

[0012] A skew generation method according to claim 5 of the present invention comprises the steps of: oscillating and outputting a clock signal; A plurality of signal generators 4 including IQ modulators 13A and 13B, pattern generation units 14A and 14B, and control units 15A and 15B The clock signal is IQ modulated to adjust the phase angle, and the positive and negative signals are generated in opposite phases at the timing of the signal. Exit and A transmission timing shifter that synchronizes the operation of the plurality of signal generators and shifts the transmission timing of the signals by an integer unit of UI of the set skew amount. to , the fractional unit of the UI of the set skew amount is applied to IQ modulation. each Allocation and When the skew amount in UI units is set, the control units of the plurality of signal generators allocate the necessary IQ modulation amounts and transmission timing shift amounts to the IQ modulators and the pattern generation units. performing at least one of the control steps; and a step of multiplexing the positive signals and the negative signals at the same desired amplitude ratio to output a ternary or higher PAM signal.

[0013] A skew generating method according to claim 6 of the present invention comprises the steps of: oscillating and outputting a clock signal; The first signal generator 4A includes a first IQ modulator 13A, a first pattern generating unit 14A, and a first control unit 15A. The clock signal is IQ modulated and the phase angle is adjusted to generate the upper positive and negative signals, which are out of phase with each other. Exit and A second signal generator 4B including a second IQ modulator 13B, a second pattern generating unit 14B, and a second control unit 15B The clock signal is IQ modulated and the phase angle is adjusted to generate the lower positive and negative signals, which are out of phase with each other. Exit and a transmission timing shifter that synchronizes the first signal generator and the second signal generator and shifts the transmission timing of the signal by an integer unit of UI of the set skew amount; to , the fractional unit of the UI of the set skew amount is applied to IQ modulation. each Allocation and When the skew amount in UI units is set, the first control unit divides it into a required IQ modulation amount and a transmission timing shift amount, and controls the first IQ modulator and the first pattern generation unit. performing at least one of the control steps; When the skew amount in UI units is set, the second control unit controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; and a step of multiplexing the upper positive signal and the lower positive signal together, and the upper negative signal and the lower negative signal together at the same desired amplitude ratio, and outputting a PAM3 signal.

[0014] A skew generating method according to claim 7 of the present invention comprises the steps of: oscillating and outputting a clock signal; The first signal generator 4A includes a first IQ modulator 13A, a first pattern generating unit 14A, and a first control unit 15A. The clock signal is IQ modulated and the phase angle is adjusted to generate the positive and negative MSB signals, which are out of phase with each other. Exit and A second signal generator 4B including a second IQ modulator 13B, a second pattern generating unit 14B, and a second control unit 15B The clock signal is IQ modulated and the phase angle is adjusted to generate LSB positive and negative signals in opposite phases. Exit and a transmission timing shifter that synchronizes the first signal generator and the second signal generator and shifts the transmission timing of the signal by an integer unit of UI of the set skew amount; to , the fractional unit of the UI of the set skew amount is applied to IQ modulation. each Allocation and When the skew amount in UI units is set, the first control unit divides it into a required IQ modulation amount and a transmission timing shift amount, and controls the first IQ modulator and the first pattern generation unit. performing at least one of the control steps; When the skew amount in UI units is set, the second control unit controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; and a step of multiplexing the MSB positive signal and the LSB positive signal together, and the MSB negative signal and the LSB negative signal together at the same desired amplitude ratio, to output a PAM4 signal.

[0015] The skew generation method according to claim 8 of the present invention is the skew generation method according to any one of claims 5 to 7, When the skew amount is set in units of time, the skew amount set in the units of time Tobi The method is characterized by multiplying the bit rate by the amount of skew in UI units. [Effects of the Invention]

[0016] According to the present invention, the amount of skew of a ternary or higher PAM signal can be varied using multiple synchronized signal generators, which not only improves convenience compared to using a mechanical delay adapter, but also enables measurements with excellent variable width, reproducibility, and resolution. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram showing a schematic configuration of a skew generation device according to the present invention when generating a PAM4 signal. FIG. [Figure 2] 2 is a block diagram showing the internal configuration of a first signal generator and a second signal generator of the skew generating device of FIG. 1. FIG. [Figure 3] 1 is a block diagram showing a schematic configuration of a skew generator according to the present invention when generating a PAM3 signal. FIG. [Figure 4] 1 is a block diagram showing a schematic configuration of a skew generator according to the present invention when generating a PAM8 signal. FIG. [Figure 5] FIG. 1 is an explanatory diagram of a method for multiplexing PAM2N signals. [Figure 6] FIG. 10 is an explanatory diagram of a method for multiplexing a PAMN+1 signal. [Figure 7] FIG. 7 is an explanatory diagram of bit correspondence in USB4 Version 2.0 as an example using PAM3 generated by the multiplexing method of FIG. 6. [Figure 8] FIG. 10 is an explanatory diagram illustrating a case where a multiplexing method for PAM2N signals and a multiplexing method for PAMN+1 signals are combined. [Figure 9] FIG. 1 is an explanatory diagram of a conventional method for generating a PAM4 signal. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0019] The skew generation device and method according to the present invention generate PAM skew (the individual skews of the signals that are the basis for generating the PAM signal) for ternary or higher-level PAM signals using positive and negative signals that are repetitive signals of opposite phases to each other. The skew generation device 1 (1A) shown in Fig. 1 enables the amount of skew of a PAM4 signal using positive and negative signals that are repetitive signals of opposite phases to each other and that are input to an object W (device under test or measuring instrument), and is generally configured with a clock oscillator 2, a setting unit 3, multiple signal generators 4 (a first signal generator 4A, a second signal generator 4B), and a PAM encoder 5.

[0020] The skew generating device 1A synchronizes the operation of the first signal generator 4A and the second signal generator 4B, manipulates the internal delay amounts of the first signal generator 4A and the second signal generator 4B, varies the PAM4 signal to a desired skew amount (eye phase), and outputs positive and negative signals with arbitrary delay amounts 1 and 2.

[0021] 1 to 4, a positive signal is represented as Pos and a negative signal as Neg. In addition, in Fig. 1 to 3, the first signal generator 4A and the second signal generator 4B are illustrated as separate block configurations, and in Fig. 4, the first signal generator 4A, the second signal generator 4B, and the third signal generator 4C are illustrated as separate block configurations, but these can also be configured as a single module.

[0022] The clock oscillator 2 oscillates and outputs a clock signal of a required frequency using a square wave signal or a sine wave signal. The clock signal oscillated and output from the clock oscillator 2 is input to an IQ modulator 13A (described later) of the first signal generator 4A and an IQ modulator 13B (described later) of the second signal generator 4B.

[0023] The setting unit 3 is a GUI that the user operates to input information, and sets the type of pattern (positive signal and negative signal) to be input to the evaluation object W, the bit rate, and the amount of skew for each of the first signal generator 4A and the second signal generator 4B, as information necessary to generate PAM skew.

[0024] Here, the skew amount can be input in UI (unit interval) or time (sec). However, in this embodiment, as in the skew amount varying method described below, the skew amount is varied by IQ modulation and transmission timing shift, so it operates in the dimension of phase ≈ UI rather than time (sec). Note that transmission timing shift means shifting the transmission timing of signal bits (symbols in PAM3 or higher) by an integer unit of UI of the skew amount to be set: N bits (symbols). Therefore, when the skew amount is input and set by the setting unit 3 in units of time (sec), the skew amount is converted into UI units in the control unit 15A (described later) of the first signal generator 4A and the control unit 15B (described later) of the second signal generator 4B, based on the formula UI = skew amount time (sec) × bit rate, and set.

[0025] In this embodiment, since the resolution of the skew is in units of 2 mUI, rounding may be necessary depending on the input value in units of time (sec) input and set by the setting unit 3, as it does not correspond to 2 mUI units. In this case, the control unit 15A of the first signal generator 4A and the control unit 15B of the second signal generator 4B, which will be described later, calculate the time (sec) of the closest skew amount that can be realized in units of 2 mUI, and perform processing to overwrite and set the input value by the setting unit 3.

[0026] The first signal generator 4A has a first output terminal 11A that outputs a positive signal Pos1 of the MSB (Most Significant Bit) and a second output terminal 12A that outputs a negative signal Neg1 of the MSB, and operates in synchronization with the second signal generator 4B. As shown in FIG. 2, the first signal generator 4A is configured with an IQ modulator 13A, a pattern generating unit 14A, and a control unit 15A.

[0027] The IQ modulator 13A performs IQ modulation on the clock signal from the clock oscillator 2 using the input I and Q signals based on the decimal unit of the skew amount set by the setting unit 3 under the control of the control unit 15A.

[0028] Under the control of the control unit 15A, the pattern generation unit 14A generates a positive signal Pos1 and a negative signal Neg1 of the MSB of the desired pattern based on the type of pattern and bit rate set by the setting unit 3, shifts the transmission timing of the generated positive signal Pos1 and negative signal Neg1 of the MSB based on the integer unit of the skew amount set by the setting unit 3, and outputs the positive signal Pos1 of the MSB of the transmission timing-shifted signals from the first output terminal 11A and the negative signal Neg1 of the MSB from the second output terminal 12A.

[0029] The control unit 15A outputs a timing synchronization signal to a control unit 15B (described later) of the second signal generator 4B so that the first signal generator 4A operates in synchronization with the second signal generator 4B, and controls the IQ modulator 13A and the pattern generation unit 14A in an integrated manner.

[0030] Specifically, the control unit 15A outputs I and Q signals corresponding to the decimal unit of the skew amount set by the setting unit 3 to the IQ modulator 13A, and adjusts and controls the phase angle of the clock signal from the clock oscillator 2. The control unit 15A also generates a positive signal Pos1 and a negative signal Neg1 of a desired pattern based on the type of pattern and bit rate set by the setting unit 3, and controls the pattern generation unit 14A to perform a transmission timing shift based on the integer unit of the skew amount set by the setting unit 3. Furthermore, when the skew amount is input and set by the setting unit 3 in units of time (sec), the control unit 15A converts it into units of UI based on the formula UI = skew amount time (sec) × bit rate, and if rounding is necessary, calculates the closest skew amount time (sec) that can be achieved in 2mUI units, and performs processing to overwrite and set the value input by the setting unit 3.

[0031] The second signal generator 4B has the same configuration as the first signal generator 4A, and has a first output terminal 11B that outputs a positive signal Pos2 of the LSB (least significant bit) and a second output terminal 12B that outputs a negative signal Neg2 of the LSB, and operates in synchronization with the first signal generator 4A. As shown in FIG. 2, the second signal generator 4B is configured with an IQ modulator 13B, a pattern generating unit 14B, and a control unit 15B.

[0032] The IQ modulator 13B performs IQ modulation on the clock signal from the clock oscillator 2 using the input I and Q signals based on the decimal unit of the skew amount set by the setting unit 3 under the control of the control unit 15B.

[0033] Under the control of the control unit 15B, the pattern generation unit 14B generates an LSB positive signal Pos2 and a negative signal Neg2 of a desired pattern based on the type of pattern and bit rate set by the setting unit 3, shifts the transmission timing of the generated LSB positive signal Pos2 and negative signal Neg2 based on the integer unit of the skew amount set by the setting unit 3, and outputs the LSB positive signal Pos2 of the transmission timing-shifted signals from the first output terminal 11B and the LSB negative signal Neg2 from the second output terminal 12B.

[0034] The control unit 15B outputs a timing synchronization signal to the control unit 15A of the first signal generator 4A so that the second signal generator 4B operates in synchronization with the first signal generator 4A, and controls the IQ modulator 13B and the pattern generation unit 14B in an integrated manner.

[0035] Specifically, the control unit 15B outputs I and Q signals corresponding to the decimal unit of the skew amount set by the setting unit 3 to the IQ modulator 13B, and adjusts and controls the phase angle of the clock signal from the clock oscillator 2. The control unit 15B also generates a pattern (positive signal Pos2 and negative signal Neg2) based on the type of pattern and bit rate set by the setting unit 3, and controls the pattern generation unit 14B to perform a transmission timing shift based on the integer unit of the skew amount set by the setting unit 3. Furthermore, when the skew amount is input and set by the setting unit 3 in units of time (sec), the control unit 15B converts it into units of UI based on the formula UI = skew amount time (sec) × bit rate, and if rounding is necessary, calculates the closest skew amount time (sec) that can be achieved in 2mUI units, and performs processing to overwrite and set the value input by the setting unit 3.

[0036] The PAM encoder 5 outputs a combined signal (PAM4 signal) that is generated by combining the positive signals and negative signals output by the first signal generator 4A and the second signal generator 4B at a desired amplitude ratio and encoding them, and is equipped with attenuators 5a (5a1, 5a2) and combiners (power dividers) 5b (5b1, 5b2).

[0037] The attenuator 5a1 attenuates the LSB positive signal Pos2 output from the first output terminal 11B of the second signal generator 4B by a desired attenuation amount. The attenuator 5a2 attenuates the LSB negative signal Neg2 output from the second output terminal 12B of the second signal generator 4B by the same desired attenuation amount as the LSB positive signal Pos2. Note that if the control unit 15B of the second signal generator 4B varies the amplitudes of the LSB positive signal Pos2 and the LSB negative signal Neg2 at a desired amplitude ratio set by the setting unit 3, the attenuators 5a (5a1, 5a2) can be omitted.

[0038] Combiner 5b1 combines MSB positive signal Pos1 output from first output terminal 11A of first signal generator 4A with LSB positive signal Pos2 attenuated by attenuator 5a1, and outputs the combined signal (PAM4 signal) of positive signals with a desired amplitude ratio to object W (device under test or measuring instrument). Combiner 5b2 combines MSB negative signal Neg1 output from second output terminal 12A of first signal generator 4A with LSB negative signal Neg2 attenuated by attenuator 5a2, and outputs the combined signal (PAM4 signal) of negative signals with the same desired amplitude ratio as positive signal Pos1 to object W (device under test or measuring instrument).

[0039] Next, a method for varying the amount of skew using the skew generating device 1A configured as above will be described.

[0040] First, the setting unit 3 sets the type of pattern (positive signal, negative signal) to be input to the object W (object under test or measuring instrument), the bit rate, and the amount of skew for each of the first signal generator 4A and the second signal generator 4B.

[0041] Here, the skew amount can be input in UI or time (sec). If the skew amount is input and set in units of time (sec), the control unit 15A of the first signal generator 4A and the control unit 15B of the second signal generator 4B convert it into UI units and set it based on the formula UI = skew amount time (sec) × bit rate.

[0042] Furthermore, if the input value in units of time (sec) input and set by the setting unit 3 does not match 2 mUI units and rounding is required, the control unit 15A of the first signal generator 4A and the control unit 15B of the second signal generator 4B calculate the time (sec) of the closest skew amount that can be achieved in 2 mUI units, and perform a process of overwriting the input value by the setting unit 3.

[0043] Then, when the skew amount in UI units is set, the control unit 15A of the first signal generator 4A and the control unit 15B of the second signal generator 4B allocate the necessary IQ modulation amount and transmission timing shift amount to control at least one of the IQ modulators 13A, 13B and the pattern generation units 14A, 14B.

[0044] Here, transmission timing shift can only manipulate the amount of skew in 1 UI increments, but the maximum variation is large (for example, ±64 UI). In contrast, IQ modulation can vary the amount of skew in decimal units (for example, 2 mUI), but the maximum variation is small (±360° = ±1000 mUI). For this reason, in this embodiment, the integer unit portion of the required skew amount (UI) is allocated to transmission timing shift, and the decimal unit portion is allocated to IQ modulation, and both are controlled.

[0045] Specifically, when the skew amount is 1250 (mUI), it is 1 transmission timing shift (1000 mUI) + IQ modulation 90° (250 mUI), and when the skew amount is -2250 (mUI), it is -3 transmission timing shift (-3000 mUI) + IQ modulation 270° (750 mUI).

[0046] In the above examples, IQ modulation is used in the range of 0 to 360° (0 to 2π) = 0 to 1000 mUI, but the point at which the transmission timing shift is advanced is arbitrary. For example, IQ modulation can be used in the range of ±500 mUI with ±180° (±π) = 0 mUI as the center. In this case, if the skew amount is 1250 (mUI), the result is 1 transmission timing shift (1000 mUI) + IQ modulation 90° (250 mUI). Also, if the skew amount is -2250 (mUI), the result is -2 transmission timing shift (-2000 mUI) + IQ modulation -90° (-250 mUI).

[0047] In the above examples, the skew amount is varied by both transmission timing shift and IQ modulation, but depending on the set skew amount, it is also possible to vary the skew amount by either transmission timing shift or IQ modulation. For example, if the set skew amount is 1000 (mUI), the result is 1 transmission timing shift (1000 mUI), and only the transmission timing shift is controlled. Also, if the set skew amount is 250 (mUI), the result is IQ modulation 90° (250 mUI), and only the IQ modulation is controlled.

[0048] In the above-described skew generating device 1A, the first signal generator 4A and the second signal generator 4B operate synchronously, and control at least one of the skew amounts by allocating integer units of UI of the set skew amount to transmission timing shift and decimal units to IQ modulation, and combines positive signals (Pos1 and Pos2) and negative signals (Neg1 and Neg2) at the same desired amplitude ratio, and the combined signal (PAM4 signal) is input to the object W (device under test or measuring instrument).

[0049] That is, when the positive signal Pos1 and the negative signal Neg1 are varied to a desired skew amount (arbitrary delay amount 1) in the first signal generator 4A, and the positive signal Pos2 and the negative signal Neg2 are varied to a desired skew amount (arbitrary delay amount 2) in the second signal generator 4B, the LSB positive signal Pos2 output from the first output terminal 11B of the second signal generator 4B is attenuated by the desired attenuation amount (attenuation amount according to the desired amplitude ratio) in the attenuator 5a1 of the PAM encoder 5, and then combined with the MSB positive signal Pos1 output from the first output terminal 11A of the first signal generator 4A in the combiner 5b1, and input to the object W (device under test or measuring instrument) as a combined signal (PAM4 signal) of positive signals with the desired amplitude ratio.

[0050] Furthermore, the LSB negative signal Neg2 output from the second output terminal 12B of the second signal generator 4B is attenuated by the attenuator 5a2 of the PAM encoder 5 by the same desired attenuation amount (attenuation amount according to the desired amplitude ratio) as the LSB positive signal Pos2, and then combined with the MSB negative signal Neg1 output from the second output terminal 12A of the first signal generator 4A by the combiner 5b2, and input to the object W (object under test or measuring instrument) as a combined signal (PAM4 signal) of negative signals with the desired amplitude ratio.

[0051] A differential signal is generated from a combined signal (PAM4 signal) based on a positive signal input to the target W and a combined signal (PAM4 signal) based on a negative signal. However, if only one signal (single-ended transmission) is required to be input to the target W, the remaining signal can be input to a monitor device (not shown) for monitoring purposes to observe the waveform.

[0052] The pattern generation unit 14A of the first signal generator 4A and the pattern generation unit 14B of the second signal generator 4B described above can generate PRBS patterns or arbitrary patterns, and can control the start timing of the patterns. Specifically, to achieve higher-rate data output from a low-rate pattern generation unit, for example, they can be configured with an FPGA that outputs 1 / N data and multiple MUXes (N:1 MUX for MSB output, N:1 MUX for LSB output, and 2:1 MUX for PAM4 output), or they can be configured with D-FFs, but are not limited to these circuit configurations.

[0053] 1 and 2, a PAM4 signal is generated as a typical example, but the present invention is not limited to this. For example, a PAM3 signal can be generated by multiplexing an upper signal and a lower signal.

[0054] An embodiment of the skew generator 1 (1B) for generating a PAM3 signal will be described below with reference to Fig. 3. Note that components that function in the same way as those in the skew generator 1A of Fig. 1 are given the same numbers, and their description will be omitted.

[0055] The skew generating device 1 (1B) of FIG. 3 is generally configured to include a clock oscillator 2, a setting unit 3, a first signal generator 4A, a second signal generator 4B, and a PAM encoder 5.

[0056] In the skew generating device 1B of Figure 3, the first signal generator 4A and the second signal generator 4B operate synchronously, and the integer unit of the UI of the set skew amount is controlled by a transmission timing shift, and the decimal unit is controlled by allocating IQ modulation, and positive signals and negative signals are multiplexed at the same desired amplitude ratio, and the multiplexed signal (PAM3 signal) is input to the object W (device under test or measuring instrument).

[0057] That is, an Upper signal based on the positive signal Pos1 that has been varied to the desired skew amount (arbitrary delay amount 1) is output from the first output terminal 11A of the first signal generator 4A, and a Lower signal based on the positive signal Pos2 that has been varied to the desired skew amount (arbitrary delay amount 2) is output from the first output terminal 11B of the second signal generator 4B. Then, the Upper signal based on the positive signal Pos1 and the Lower signal based on the positive signal Pos2 are combined by the combiner 5b (5b1) of the PAM encoder 5, and input to the object W (device under test or measuring instrument) as a combined signal (PAM3 signal) based on positive signals with a desired amplitude ratio.

[0058] Furthermore, an Upper signal based on the negative signal Neg1 that has been varied to a desired skew amount (arbitrary delay amount 1) is output from the second output terminal 12A of the first signal generator 4A, and a Lower signal based on the negative signal Neg2 that has been varied to a desired skew amount (arbitrary delay amount 2) is output from the second output terminal 12B of the second signal generator 4B. The Upper signal based on the negative signal Neg1 and the Lower signal based on the negative signal neg2 are then combined by the combiner 5b (5b2) of the PAM encoder 5, and input to the object W (device under test or measuring instrument) as a combined signal (PAM3 signal) based on negative signals with a desired amplitude ratio.

[0059] In addition, one of the combined signals (PAM3 signal) based on a positive signal and the combined signal (PAM3 signal) based on a negative signal input to the above-mentioned target W can also be input to a monitor device (not shown) for monitoring purposes to observe the waveform.

[0060] Furthermore, in the embodiment of FIGS. 1 and 2, two signal generators (first signal generator 4A and second signal generator 4B) are operated synchronously, but the number of signal generators operated synchronously is not limited to two. For example, it is also possible to operate three signal generators synchronously to generate a PAM8 signal. Below, an embodiment of the skew generation device 1 (1C) in which three signal generators are operated synchronously to generate a PAM8 signal will be described with reference to FIG. 4. Note that components that function in the same way as those in the skew generation device 1A of FIG. 1 are assigned the same numbers, and their description will be omitted.

[0061] 4 is generally configured to include a clock oscillator 2, a setting unit 3, a first signal generator 4A, a second signal generator 4B, a third signal generator 4C, and a PAM encoder 5. The third signal generator 4C has the same internal configuration as the first signal generator 4A and the second signal generator 4B shown in FIG.

[0062] In the skew generating device 1C of FIG. 4, the first signal generator 4A, the second signal generator 4B, and the third signal generator 4C operate synchronously, and control the set skew amount by allocating integer units of UI as a transmission timing shift and decimal units as IQ modulation, and combines positive signals and negative signals at the same desired amplitude ratio, and the combined signal (PAM8 signal) is input to the object W (device under test or measuring instrument).

[0063] That is, a positive signal Pos1 that has been adjusted to a desired skew amount (arbitrary delay amount 1) is output from a first output terminal 11A of a first signal generator 4A, a positive signal Pos2 that has been adjusted to a desired skew amount (arbitrary delay amount 2) is output from a first output terminal 11B of a second signal generator 4B, and then attenuated by a desired attenuation amount (attenuation amount according to a desired amplitude ratio) by an attenuator 5a (5a1) of a PAM encoder 5, and a positive signal Pos3 that has been adjusted to a desired skew amount (arbitrary delay amount 3) is output from a first output terminal 11C of a third signal generator 4C. Then, the positive signal Pos1 and the positive signal Pos2 attenuated by the attenuator 5a (5a1) are combined by a combiner 5b (5b1), and then combined with the positive signal Pos3 by a combiner 5b (5b2), and the combined signal (PAM8 signal) of positive signals with a desired amplitude ratio is input to an object (device under test or measuring instrument) (not shown).

[0064] Furthermore, a negative signal Neg1 that has been changed to the desired skew amount (arbitrary delay amount 1) is output from the second output terminal 12A of the first signal generator 4A, a negative signal Neg2 that has been changed to the desired skew amount (arbitrary delay amount 2) is output from the second output terminal 12B of the second signal generator 4B, and then attenuated by the desired attenuation amount (attenuation amount according to the desired amplitude ratio) by the attenuator 5a (5a2) of the PAM encoder 5, and a negative signal Neg3 that has been changed to the desired skew amount (arbitrary delay amount 3) is output from the first output terminal 11C of the third signal generator 4C. Then, the negative signal Neg1 and the negative signal Neg2 attenuated by the attenuator 5a (5a2) of the PAM encoder 5 are combined by the combiner 5b (5b3) of the PAM encoder 5, and then the negative signal Neg3 and the negative signal Neg3 are combined by the combiner 5b (5b3) of the PAM encoder 5, and the combined signal (PAM8 signal) of negative signals with the desired amplitude ratio is input to the object (object to be measured or measuring instrument) not shown.

[0065] One of the combined signal (PAM8 signal) based on positive signals and the combined signal (PAM8 signal) based on negative signals input to an object (device under test or measuring instrument) (not shown) can be input to a monitor device (not shown) for monitoring purposes to observe the waveform. Also, if the control unit 15B of the second signal generator 4B varies the amplitudes of the positive signal Pos2 and the negative signal Neg2 at a desired amplitude ratio set by the setting unit 3, the attenuator 5a (5a1, 5a2) of the PAM encoder 5 can be omitted.

[0066] In the above-described embodiment, PAM3, PAM4, and PAM8 signals have been described as PAM signals controlled by transmission timing shifts in integer units of UI of the set skew amount and IQ modulation in decimal units. However, the present invention is not limited to these signals and can be applied to any PAM signal. Below, a method for multiplexing any PAM signal will be described with reference to Figures 5 to 8. Note that Figures 5, 6, and 8 illustrate cases in which positive signals are multiplexed to generate a PAM signal, but negative signals can also be multiplexed in the same way to generate a PAM signal.

[0067] Figure 5 shows PAM2 N Fig. 6 is an explanatory diagram of the signal multiplexing method. Fig. 7 is an explanatory diagram of the bit correspondence in USB4 Version 2.0 as an example using PAM3 generated by the multiplexing method in Fig. 6. Fig. 8 is an explanatory diagram of the PAM2 N 5, 6, and 8 show the case where the skew amount is set to 0. The amplitude ratio is adjusted by an attenuator (not shown) or the control unit of the signal generator 4. Here, PAM2 N 2 N indicates a power of 2.

[0068] If the total number of NRZ signals used (number of signal generators 4) is N (N≧2), and the nth signal generator 4 among the N signal generators 4 is n, then PAM2 NIn the signal multiplexing method, as shown in FIG. 5, N NRZ signals generated by the first to Nth signal generators 4 are multiplexed by a combiner 5b to generate PAM2. N In this case, the first to Nth signal generators 4 correspond to the respective digits of the bits, and the amplitude ratio corresponds to the weight (power of 2) of the digit.

[0069] Let N (N≧2) be the total number of NRZ signals used (the number of signal generators 4) and n be the nth signal generator 4 among the N signal generators 4. In the PAMN+1 signal multiplexing method, as shown in FIG. 6, N NRZ signals generated by the first through Nth signal generators 4 are multiplexed by a combiner 5b at the same amplitude to generate the PAMN+1 signal. This PAMN+1 multiplexing method makes it possible to generate any PAM signal other than a power of two, such as a PAM3 signal. Further, referring to FIG. 7, an example of generating a PAM3 signal will be described. As an example of a PAM3 signal, USB4 Version 2.0 transmits three bits in two symbols, as shown in FIG. 7. Specifically, using two signal generators 4, for example, in the case of a bit string of "011" in FIG. 7, the first signal generator 4 generates a 1 and the second signal generator 4 generates a 0 in the first symbol, and the first signal generator 4 generates a 0 and the second signal generator 4 generates a 0 in the second symbol.

[0070] PAM2 N In the combining method that combines the PAM+1 signal combining method and the PAM+1 signal combining method, as shown in FIG. 8, the number of signals from the signal generators 4 that are added together at a power amplitude ratio is N (N≧2), and the number of signals from the signal generators 4 that are added together at the same amplitude ratio is M (M≧1). The NRZ signals generated by each signal generator 4 are combined by a combiner 5b to generate PAM2. N Figure 8 shows the PAM2 signal generator 4 with the number of signals N=2, which are added together at a power amplitude ratio (1 / 2), and the number of signals M=1, which are added together at the same amplitude ratio (1). 2 +1=This is an example of generating a PAM5 signal.

[0071] As described above, according to this embodiment, multiple synchronized signal generators (first signal generator 4A and second signal generator 4B in FIGS. 1 and 3, and first signal generator 4A, second signal generator 4B, and third signal generator 4C in FIG. 4) individually generate positive and negative signals to vary the eye phase with the desired skew amount, which not only improves convenience compared to using conventional mechanical delay adapters, but also enables skew variation with excellent variable width, reproducibility, and resolution. Specifically, a variable width of ±64 UI and a resolution of 2 mUI are achieved, and the operating rate is 2.4 Gbaud to 64.2 Gbaud. Converting this to time units results in a maximum variable width of ±26.6 ns and a minimum resolution of 31.1 fs.

[0072] The skew generator 1 of this embodiment is not configured to generate positive and negative signals from a single signal generator. Instead, as shown in FIG. 1, it is configured to generate positive and negative signals individually from two synchronously operating signal generators (first signal generator 4A and second signal generator 4B). Therefore, each signal can be independently controlled for parameters other than skew. The controllable parameters depend on the functions of the signal generator, but examples include amplitude and Tx equalizer (emphasis). For comparison with FIG. 9, FIG. 1 uses attenuator 5a (5a1, 5a2: 6 dB attenuator) on the second signal generator 4B side, which outputs LSB positive and negative signals. However, the amplitude can be halved within the second signal generator 4B without using an attenuator.

[0073] In addition, the amount of skew can be controlled by inputting it in time units or UI units in the setting unit 3, or by intuitively operating the setting unit 3 while a waveform image with a skew is displayed.

[0074] As described above, according to this embodiment, the skew amount (eye phase) of a ternary or higher PAM signal can be varied using multiple signal generators (at least two signal generators) operated in synchronization. This not only improves convenience compared to using a mechanical delay adapter, but also enables measurements with excellent variable width, reproducibility, and resolution.

[0075] Furthermore, since it does not affect the transmission path characteristics, the evaluator can easily separate and evaluate only the effects of skew.

[0076] Furthermore, since multiple signal generators (4A, 4B, 4C) can be operated independently, it is possible to intentionally break the symmetry of the waveform, making it possible to evaluate skew not only from the perspective of arrival timing but also from the perspective of waveform asymmetry.

[0077] Furthermore, the amount of skew can be controlled by inputting it in time units or UI units in the setting unit 3, or by intuitively operating the setting unit 3 while a skewed waveform image is displayed, making it easier for the user to intuitively grasp what kind of skewed signal is being provided.

[0078] These are useful for compensating for skew between, for example, MSB and LSB that occurs due to the nature of the measurement system, and can also be used for verification that anticipates that skew between, for example, MSB and LSB may occur in devices due to manufacturing variations, and for evaluation when a device receives a skewed PAM signal.

[0079] Although the best mode for the skew generating device and skew generating method according to the present invention has been described above, the present invention is not limited to the description and drawings of this mode. In other words, all other modes, embodiments, and operational techniques that can be realized by those skilled in the art based on this mode are naturally included in the scope of the present invention. [Explanation of symbols]

[0080] 1(1A, 1B, 1C) Skew generator 2 Clock oscillator 3. Settings 4. Signal Generator 4A First Signal Generator 4B Second Signal Generator 4C Third Signal Generator 5 PAM Encoder 5a(5a1,5a2) Attenuator 5b(5b1,5b2,5b3,5b4) combiner 11A, 11B, 11C First output terminal 12A, 12B, 12C Second output terminal 13A, 13B IQ Modulator 14A, 14B Pattern generation section 15A, 15B control section 21 Attenuator 22 Synthesizer W Object (object to be measured or measuring instrument)

Claims

1. a clock oscillator (2) that oscillates and outputs a clock signal; a plurality of signal generators (4A, 4B) including IQ modulators (13A, 13B) for outputting positive signals and negative signals of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle, pattern generating units (14A, 14B), and control units (15A, 15B); the plurality of signal generators operate synchronously, and allocate a fractional unit of UI of the set skew amount to IQ modulation, while shifting the transmission timing of the signal by an integer unit of UI of the set skew amount; a control unit of the plurality of signal generators, when a skew amount in units of UI is set, allocating a necessary IQ modulation amount and a necessary transmission timing shift amount to control at least one of the IQ modulator and the pattern generation unit; A skew generator that combines positive signals and negative signals at the same desired amplitude ratio to output a PAM signal with three or more levels.

2. a clock oscillator (2) that oscillates and outputs a clock signal; a first signal generator (4A) including a first IQ modulator (13A), a first pattern generating unit (14A), and a first control unit (15A) for outputting upper positive and negative signals of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle; a second signal generator (4B) including a second IQ modulator (13B), a second pattern generating unit (14B), and a second control unit (15B) for outputting a lower positive signal and a lower negative signal having opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle; the first signal generator and the second signal generator operate synchronously, and allocate a fractional unit of UI of the set skew amount to IQ modulation, and allocate a transmission timing shift that shifts the transmission timing of the signal by an integer unit of UI of the set skew amount, respectively; the first control unit, when a skew amount in units of UI is set, controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; the second control unit, when a skew amount in units of UI is set, controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; A skew generating device characterized in that the upper positive signal and the lower positive signal, and the upper negative signal and the lower negative signal are multiplexed at the same desired amplitude ratio to output a PAM3 signal.

3. a clock oscillator (2) that oscillates and outputs a clock signal; a first signal generator (4A) including a first IQ modulator (13A), a first pattern generating unit (14A), and a first control unit (15A) for outputting positive and negative MSB signals of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle; a second signal generator (4B) including a second IQ modulator (13B), a second pattern generating unit (14B), and a second control unit (15B) for outputting an LSB positive signal and a negative signal of opposite phases at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle; the first signal generator and the second signal generator operate synchronously, and allocate a fractional unit of UI of the set skew amount to IQ modulation, and allocate a transmission timing shift that shifts the transmission timing of the signal by an integer unit of UI of the set skew amount, respectively; the first control unit, when a skew amount in units of UI is set, controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; the second control unit, when a skew amount in units of UI is set, controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; A skew generating device characterized in that the MSB positive signal and the LSB positive signal, and the MSB negative signal and the LSB negative signal are multiplexed at the same desired amplitude ratio to output a PAM4 signal.

4. A skew generating device as described in any one of claims 1 to 3, characterized in that when the skew amount is set in units of time, the skew amount set in units of time is multiplied by the bit rate to convert it into a skew amount in units of UI.

5. oscillating and outputting a clock signal; a step of outputting a positive signal and a negative signal of opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by a plurality of signal generators (4) including IQ modulators (13A, 13B), pattern generating units (14A, 14B), and control units (15A, 15B); a step of synchronizing the operation of the plurality of signal generators, and allocating a fractional unit of UI of the set skew amount to IQ modulation for a transmission timing shift that shifts the signal transmission timing by an integer unit of UI of the set skew amount; When the skew amount in UI units is set, a control unit of the plurality of signal generators controls at least one of the IQ modulator and the pattern generation unit by dividing the necessary IQ modulation amount and transmission timing shift amount; and a step of multiplexing positive signals and negative signals at the same desired amplitude ratio to output a ternary or higher PAM signal.

6. oscillating and outputting a clock signal; a step of outputting upper positive and negative signals of opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by a first signal generator (4A) including a first IQ modulator (13A), a first pattern generating unit (14A), and a first control unit (15A); a step of outputting a lower positive signal and a lower negative signal having opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by a second signal generator (4B) including a second IQ modulator (13B), a second pattern generating unit (14B), and a second control unit (15B); a step of synchronously operating the first signal generator and the second signal generator, and allocating a fractional unit of UI of the set skew amount to IQ modulation for a transmission timing shift that shifts the signal transmission timing by an integer unit of UI of the set skew amount; When the skew amount in units of UI is set, the first control unit controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; When the skew amount in units of UI is set, the second control unit controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; a step of combining the upper positive signal and the lower positive signal, and the upper negative signal and the lower negative signal at the same desired amplitude ratio to output a PAM3 signal.

7. oscillating and outputting a clock signal; a step of outputting a positive signal and a negative signal of an MSB having opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle by a first signal generator (4A) including a first IQ modulator (13A), a first pattern generating unit (14A), and a first control unit (15A); a step of outputting, by a second signal generator (4B) including a second IQ modulator (13B), a second pattern generating unit (14B), and a second control unit (15B), a positive signal and a negative signal of LSB having opposite phases to each other at the timing of a signal obtained by IQ-modulating the clock signal and adjusting the phase angle; a step of synchronously operating the first signal generator and the second signal generator, and allocating a fractional unit of UI of the set skew amount to IQ modulation for a transmission timing shift that shifts the signal transmission timing by an integer unit of UI of the set skew amount; When the skew amount in units of UI is set, the first control unit controls at least one of the first IQ modulator and the first pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; When the skew amount in units of UI is set, the second control unit controls at least one of the second IQ modulator and the second pattern generation unit by dividing the amount into a required IQ modulation amount and a required transmission timing shift amount; and a step of multiplexing the MSB positive signal and the LSB positive signal together, and the MSB negative signal and the LSB negative signal together at the same desired amplitude ratio to output a PAM4 signal.

8. A skew generation method according to any one of claims 5 to 7, characterized in that when the skew amount is set in units of time, the skew amount set in units of time is multiplied by the bit rate to convert it into a skew amount in units of UI.

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