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这是关于dBC中的IM测量,使用PXA频谱分析仪模式进行6载波GMSK调制。
选择的检测器是“平均值”。 我正在比较“Log_Power”和“Power”的平均类型之间的IM(以dBc为单位)。 选择跟踪平均,计数为100.当平均类型为“功率”时,计算桶中所有样本的RMS值并以dBm(My dsiplay scale为dBm)显示。 由于激活跟踪平均值为100,因此扫描中的桶值以W为平均值,转换为dBm并显示为最终跟踪(我假设为单次扫描)。 当平均类型为“Log_Power”时,计算桶中所有样本的平均值,并以dBm为单位显示。由于激活跟踪平均值100,扫描中的桶值在对数模式下平均,转换为dBm并显示 作为最终的痕迹(我假设单次扫描)。 此处显示的数字将比实数小约2.5 dB(以“电源”模式显示的数字将是实数)。 因此,每当我将“Log_Power”的平均类型更改为“Power_RMS”时,载波和IM产品都应该达到2.5dB,而dBc中的IM不应该改变。 但在我的情况下,载波幅度变化2dB,IM产物变化2.9 dB,IM dBc降低了0.9 dB。 以下是我得到的数字==>载波IM IM(DBC)Log_Power -6.33 dBm -77.91 dBm -71.58 Power_RMS -4.32 dBm -75.04 dBm -70.72为什么载波和IM产品在不同的平均类型下表现不同? IM产品靠近PXA Noise Floor。 这有贡献吗? 以上来自于谷歌翻译 以下为原文 This is regarding IM measurements in dBC using PXA spectrum analyzer mode for 6 carriers GMSK modulation. The detector selected is "Average". I am comparing the IM (in dBc) between the Average types of "Log_Power" and "Power". Trace averaging is selected with count of 100. When the average type is "Power", RMS value of all the samples in a bucket is calculated and displayed in dBm ( My dsiplay scale is dBm). Since trace averaging with 100 is activated, the bucket values in the sweeps are averaged in W , converted to dBm and displayed as final trace (I am assuming single sweep). When the average type is "Log_Power", average of log of all samples in the bucket is calculated and displayed in dBm.Since trace averaging with 100 is activated, the bucket values in the sweeps are averaged in log mode , converted to dBm and displayed as final trace (I am assuming single sweep). Here the numbers displayed will be around 2.5 dB less than the real numbers (The numbers displayed with "Power" mode will be the real numbers). So, whenever I change sthe average type for "Log_Power" to "Power_RMS", both carriers and IM products should chnage by 2.5dB and the IM in dBc should not change. But in my case, the carrier amplitudes are changing by 2dB and the IM products by 2.9 dB and the IM dBc is degrading by .9 dB. Following are the numbers I am getting==> Carrier IM IM (DBC) Log_Power -6.33 dBm -77.91 dBm -71.58 Power_RMS -4.32 dBm -75.04 dBm -70.72 Why the carrier and IM products are behaving differently with different average type?. The IM products are close to PXA Noise Floor. Is this contributing? |
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对于IM产品,您有多接近本底噪声?
众所周知(至少对于一些老人来说)噪声对数的平均值将比噪声平均值的对数低1.1 dB。 如果IM产品噪声较大,则日志中的平均值将显示较低的数字。 当然,在当天,SA模式只有日志检测器,因此只能读取日志功率。 今天你有一个选择。 这种差异的原因是日志中有些嘈杂的数字远远小于(更负面)相同的噪音。 最极端的例子是,如果噪声完全取消信号并产生零功率...记录下来并将其添加到你的平均值,你仍然得到-infinity! 以上来自于谷歌翻译 以下为原文 how close to the noise floor are you for the IM products. It is well known (at least to some oldsters) that the avg of the log of noise will give 1.1 dB lower reading than the log of average of noise. If the IM products are vary noisy, averaging in log will show a lower number. Of course, back inthe day, SA modes only had log detectors, so only log power could be read. Today you have a choice. The reason for the discrepency is that some numbers in log that are noisy go much smaller than (more negative) than the same noise going positive. And the extreme example is if the noise cancels exactly the signal and generates a zero power...take the log of that and add it to your avg and you still get -infinity! |
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脑洞大赛9 发表于 2019-7-16 09:28 嗨 - 来自MicroWaves的一篇非常好的文章& 有关此主题的RF,请访问:http://mwrf.com/contributors/techniques-making-measurements-noise-signals-spectrum-analyzer您可能还对以下内容感兴趣:http://mwrf.com/contributors/optimize- 频谱分析仪设置toi-measurements问候 - 以上来自于谷歌翻译 以下为原文 Hi - A very good article from MicroWaves & RF on this topic is available at: http://mwrf.com/contributors/techniques-making-measurements-noise-signals-spectrum-analyzer You may also be interested in: http://mwrf.com/contributors/optimize-spectrum-analyzer-settings-toi-measurements Regards - |
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