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university:tools:pluto:users:amp [15 May 2018 01:44] – [Measurements] Travis Collinsuniversity:tools:pluto:users:amp [21 Jan 2019 14:13] (current) – [Peak to Average] Robin Getz
Line 60: Line 60:
 ^ Power in mW | Power in dBm | ^ Power in mW | Power in dBm |
 |  0.1 mW |  -10 dBm | |  0.1 mW |  -10 dBm |
 +|  0.3 mW |   -5 dBm |
 |    1 mW |    0 dBm | |    1 mW |    0 dBm |
 +|  3.2 mW |    5 dBm |
 |   10 mW |   10 dBm | |   10 mW |   10 dBm |
 +|   32 mW |   15 dBm |
 |  100 mW |   20 dBm | |  100 mW |   20 dBm |
 +|  316 mW |   25 dBm |
  
 A doubling of output power (from 1mW to 2mW) is only +3dBm. A gain of +20dBm, is output power increasing by a factor of 100 times in mW. A doubling of output power (from 1mW to 2mW) is only +3dBm. A gain of +20dBm, is output power increasing by a factor of 100 times in mW.
Line 73: Line 77:
  
 whether expressed in percent in dB, PAPR is dimensionless quantity. whether expressed in percent in dB, PAPR is dimensionless quantity.
 +
 +When dealing with signals and amplifiers, it is the peak that we need to be concerned about, not the average power in the signal. Different types of modulation schemes have different peak to average power, and this needs to be taken into account.
  
  
Line 125: Line 131:
 |   15 |  31.6 |     1.257 V |     3.556 V | |   15 |  31.6 |     1.257 V |     3.556 V |
 |   20 |   100 |     2.236 V |     6.324 V | |   20 |   100 |     2.236 V |     6.324 V |
 +|   25 |   316 |     3.976 v |    11.246 V | 
 + 
 The question is, how do we get +20dBm (6.324V <sub>peak-peak</sub>) out of a system, when the power supply is limited to 5V? The trick is in how we connect the output stage. The output stage (RFOUT) is connected to Vcc through the inductor L1. From a DC perspective, inductors become short circuits, and RFOUT is setting at 5.0V, allowing a 10V<sub>peak-peak</sub> swing from the amplifier. This is also why it is AC-coupled by the output capacitor before it attaches to the antenna. The question is, how do we get +20dBm (6.324V <sub>peak-peak</sub>) out of a system, when the power supply is limited to 5V? The trick is in how we connect the output stage. The output stage (RFOUT) is connected to Vcc through the inductor L1. From a DC perspective, inductors become short circuits, and RFOUT is setting at 5.0V, allowing a 10V<sub>peak-peak</sub> swing from the amplifier. This is also why it is AC-coupled by the output capacitor before it attaches to the antenna.
  
Line 195: Line 202:
 where the autocorrelation of our process or signal <m>X(t)</m> is: where the autocorrelation of our process or signal <m>X(t)</m> is:
  
-<m>R_{XX}(t_1,t_2)&=E[X(t_1)X^{ast}(t_2)]</m>.+<m>R_{XX}(t_1,t_2) = E[X(t_1)X^{ast}(t_2)]</m>.
  
 In the case of AWGN this autocorrelation is simply: In the case of AWGN this autocorrelation is simply:
Line 214: Line 221:
  
 where <m>R</m> is the input resistance of the device.  For an SDR I/Q values will be based on some uncalibrated ADC values and we typically define them of unit dBFS. Resulting in a power calculation that is not relatable to Watts.  If it was desired to use an SDR an a instrument we would need to relate each output of the ADC to a specific input voltage at the antenna.  This mapping would allow us to accurate measure quantities in SI units instead of relative units. where <m>R</m> is the input resistance of the device.  For an SDR I/Q values will be based on some uncalibrated ADC values and we typically define them of unit dBFS. Resulting in a power calculation that is not relatable to Watts.  If it was desired to use an SDR an a instrument we would need to relate each output of the ADC to a specific input voltage at the antenna.  This mapping would allow us to accurate measure quantities in SI units instead of relative units.
 +
 +==== S Parameters ====
 +
 +This data was taken on a [[https://www.keysight.com/en/pdx-x202208-pn-E5080A/ena-vector-network-analyzer?|Keysight ENA E5080A]]:
 +
 +First we calibrate things with a cable, and connector, to make sure we see what is happening. We expect this to be a flat line, with 0dB of gain. (it is a cable after all).
 +
 +{{:university:tools:pluto:users:cal_s21.png?600|E5080A Calibration}}
 +
 +Then we can look at the S12 of the amplifier board. Here we can see gain between 2 and 3 GHz, with the flat part being between 2.4 and 2.5 GHz, just like we hope.
 +
 +{{:university:tools:pluto:users:c419_s21.png?600|}}
 +
 +{{:university:tools:pluto:users:c419_s21_zoom.png?600|}}
 +
 +If we vary the amplitude at a constant frequency, we can see the P1dB point at +5dBm. In order to keep things operating in the linear region, we should make sure not to drive the amplifer board with more than +5dBm.
 +
 +{{:university:tools:pluto:users:c419_p1db.png?600|}}
 +
 +==== Results====
 +
 +The yellow line is an antenna, the red line is with the same antenna and the amplifier. You can see the +20dB of transmission at 2.4GHz.
 +
 +{{:university:tools:pluto:users:c419_s21_ant_amp.png?600|}}
 +
 +
 +
 +
university/tools/pluto/users/amp.txt · Last modified: 21 Jan 2019 14:13 by Robin Getz

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