What Are The Commonly Used In RF Unit Conversion Formula?

2024-06-17 03:55| 来源: 网络整理| 查看: 265

SolutionThese are the commonly used in RF unit conversion formula: Vpk聽 = sqrt(I2+Q2)Vrms聽= Vpk聽/ sqrt(2)Powerwatts聽= Vrms2聽/ ZohmsPowerdBW聽= 10 * log(Powerwatts)PowerdBm聽= PowerdBW聽+ 30PowerdBmV聽= PowerdBm聽+ 10 * log(100 * Zohms)PowerdBm聽= PSDdBm/Hz聽+ 10 * log(BWHz) Where,聽Zohms聽represents the input impedance of the device, BWHz聽represents the bandwidth range of user interest, and PSDdBm/Hz聽represents the power spectral density.

The following below shown the example of scenario using RF unit conversion formula:聽1. Conversion from Volts to dBmSingle-tone signal generated by vector signal transceiver (VST) has a frequency offset of 500 kHz from the carrier, IQ signal generated at a rate of 120 MS/s and output power is about -20 dBm. The signal is fed back to the VST device via the RF IN port. The I/Q level measurement results are shown in Figure 1 below, and the power measurement results are shown in Figure 2.

Figure 1.聽I/Q Level Measurement Results

Figure 2. Power Measurement Results

聽 Based on the I/Q level measurement results, the signal power can be calculated by the following formula: 聽聽聽聽I = Vpk聽* cos(theta(t)) = 0.03 * cos(theta(t))聽聽聽聽 Vpk聽= 0.03 V聽聽聽聽聽Vrms聽= Vpk聽/ sqrt(2) = 0.03 / sqrt(2) = 0.021213 V聽聽聽聽 Power = Vrms2聽/ Zohms聽 = (0.021213)2聽/ 50 = 9 uW聽聽聽聽 PowerdBm聽= 10 * log(Power) + 30 = 10 * log(9u) +30 = -20.45 dBm聽聽聽or聽聽聽PowerdBm = 20 *聽log(Vpk) + 10 = 20 * log(0.03) +10 = -20.45 dBm聽聽聽From the above conversion equation, we can find out that the time domain measurement results of signal power are basically consistent with the frequency domain calculation results.

2. Conversion from dBm/Hz to dBmSpectrum measurements captured using the NI VST are shown in Figure 3. The power spectral density at marker 1 is -84.50 dBm/Hz.

聽 Figure 3. Spectrum measurements captured using NI VST聽 At a resolution bandwidth of 200 kHz, the signal power can be calculated as follows:PdBm聽= PSDdBm/Hz聽+ 10 * log(BWHz) = -84.50 + 10 * log(2 * 105) = -31.4 dBm

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