如果不深入研究您的应用和波形,这很可能是33120A成为DDS发生器的结果。
DDS对波形进行采样,不会每个点都输出,因此您将不时地在波形上看到+/-一个时钟周期。
以下是用户手册中的一节,我认为描述了您所看到的内容:在频域中可见的另一种类型的波形错误是相位截断错误。
该错误是由输出波形的时间量化引起的。
每当波形被有限数量的水平点(长度)描述时,它就会被及时采样(或量化),从而导致相位截断误差。
相位截断引起的杂散信号会在输出波形中引入抖动。
这可以被视为输出零交叉的时间(和相位)位移。相位截断导致输出信号的相位调制,这导致寄生谐波(参见下面的等式)。
对于较低的输出频率,相位累加器周期性地不提前RAMaddresses,导致DAC提供与前一个时钟周期记录的电压相同的电压。
因此,在继续向前推进之前,阶段“滑回”360 /点。
当RAM地址增量在输出的每个周期相同时,相位截断误差(和抖动)基本上为零。
33120A中的所有标准波形均产生至少16,000个波形点,从而产生低于DAC宽带本底噪声的激励信号。相位截断谐波-20 x log10(P)dBc其中“P”是RAM中波形点的数量
。
以上来自于谷歌翻译
以下为原文
Without digging to deeply into your application and waveform this is most likely a result of the 33120A being DDS generator. DDS samples the waveform, it does not output every point necessarily, so you are going to see +/- a clock cycle on your waveforms from time to time. Here is a section from the user's manual that I think describes what you are seeing:
Another type of waveform error visible in the frequency domain is
phase truncation error. This error results from time quantization of the
output waveform. Whenever a waveshape is described by a finite number
of horizontal points (length), it has been sampled in time (or quantized)
causing a phase truncation error. Spurious signals caused by phase
truncation introduce jitter into the output waveform. This may be
regarded as time (and phase) displacement of output zero crossings.
Phase truncation causes phase modulation of the output signal which
results in spurious harmonics (see the equation below). For lower output
frequencies, the phase accumulator periodically does not advance RAM
addresses, causing the DAC to deliver the same voltage as recorded on
the previous clock cycle. Therefore, the phase “slips” back by 360 / points
before continuing to move forward again. When RAM address increments
are the same on each cycle of the output, phase truncation error (and
jitter) are essentially zero. All standard waveshapes in the 33120A are
generated with at least 16,000 waveform points which results in
spurious signals below the wide-band noise floor of the DAC.
Phase Truncation Harmonics –20 x log10 (P) dBc
where “P” is the number of waveform points in RAM.
如果不深入研究您的应用和波形,这很可能是33120A成为DDS发生器的结果。
DDS对波形进行采样,不会每个点都输出,因此您将不时地在波形上看到+/-一个时钟周期。
以下是用户手册中的一节,我认为描述了您所看到的内容:在频域中可见的另一种类型的波形错误是相位截断错误。
该错误是由输出波形的时间量化引起的。
每当波形被有限数量的水平点(长度)描述时,它就会被及时采样(或量化),从而导致相位截断误差。
相位截断引起的杂散信号会在输出波形中引入抖动。
这可以被视为输出零交叉的时间(和相位)位移。相位截断导致输出信号的相位调制,这导致寄生谐波(参见下面的等式)。
对于较低的输出频率,相位累加器周期性地不提前RAMaddresses,导致DAC提供与前一个时钟周期记录的电压相同的电压。
因此,在继续向前推进之前,阶段“滑回”360 /点。
当RAM地址增量在输出的每个周期相同时,相位截断误差(和抖动)基本上为零。
33120A中的所有标准波形均产生至少16,000个波形点,从而产生低于DAC宽带本底噪声的激励信号。相位截断谐波-20 x log10(P)dBc其中“P”是RAM中波形点的数量
。
以上来自于谷歌翻译
以下为原文
Without digging to deeply into your application and waveform this is most likely a result of the 33120A being DDS generator. DDS samples the waveform, it does not output every point necessarily, so you are going to see +/- a clock cycle on your waveforms from time to time. Here is a section from the user's manual that I think describes what you are seeing:
Another type of waveform error visible in the frequency domain is
phase truncation error. This error results from time quantization of the
output waveform. Whenever a waveshape is described by a finite number
of horizontal points (length), it has been sampled in time (or quantized)
causing a phase truncation error. Spurious signals caused by phase
truncation introduce jitter into the output waveform. This may be
regarded as time (and phase) displacement of output zero crossings.
Phase truncation causes phase modulation of the output signal which
results in spurious harmonics (see the equation below). For lower output
frequencies, the phase accumulator periodically does not advance RAM
addresses, causing the DAC to deliver the same voltage as recorded on
the previous clock cycle. Therefore, the phase “slips” back by 360 / points
before continuing to move forward again. When RAM address increments
are the same on each cycle of the output, phase truncation error (and
jitter) are essentially zero. All standard waveshapes in the 33120A are
generated with at least 16,000 waveform points which results in
spurious signals below the wide-band noise floor of the DAC.
Phase Truncation Harmonics –20 x log10 (P) dBc
where “P” is the number of waveform points in RAM.
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