Electronics-Lab.com Community  # RF Burns

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1. Hello, Say if I have two amplifiers connected in cascade with the following specifications: Apmlifier 1: Gain Noise Figure OIP3 15 dB 3 dB 15 dbm Apmlifier 2: Gain Noise Figure OIP3 15 dB 5 dB 20 dbm Note: OIP3 = third order intercept point. I calculated the overall gain, the overall noise figure and the overall third order intercept point. Overall gain = 30 dB Overall noise figure = 3.146 dB Overall OIP3 = 19.586 dBm (= -10.414 dB) My question is: What does this level of OIP3 mean? I know how to calculate it etc., but not what it actually means. For example, what happens if my RF input was greater than 19.586 dBm?? Any details you can impart will be much appreciated. RF Burns
2. Dear all, I generated a 50 MHz, -10 dBm sine-wave using a Rhode & Schwarts RF signal generator. I checked this using an Agilent spectrum analyser and, as you'd expect, I get my tone at 50 MHz with peak amplitude of -10 dBm. However, when I input my RF signal to a TDS 210 Tecktronix Digital Oscilloscope, the peak-to-peak voltage is 336 mV and the Cyc RMS voltage is 117 mV. Now, on the TDS210, Cyc RMS calculates the RMS voltage over one complete cycle of the waveform. When I tried to calculate this I got a different answer: P = -10 dBm, which is equivalent to 100 uW Now, P = V^2 / R I've taken R = 50 ohms Therefore Vrms = sqrt(P x R) That is: Vrms = sqrt(100 uW x 50 ohms) So, Vrms = 70.7 mV This is different to the 117 mV measured on the oscilloscope??
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