166 lines
6.2 KiB
Python
166 lines
6.2 KiB
Python
from tests.TestBase import TestBase
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from libreCAL import libreCAL
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import time
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import math
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class TestCalibration(TestBase):
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def cal_measure(self, number, timeout = 3):
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self.vna.cmd(":VNA:CAL:MEAS "+str(number))
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# wait for the measurement to finish
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stoptime = time.time() + timeout
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while self.vna.query(":VNA:CAL:BUSY?") == "TRUE":
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if time.time() > stoptime:
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raise AssertionError("Calibration measurement timed out")
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time.sleep(0.1)
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def test_dummy_calibration(self):
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# This test just iterates through the calibration steps. As no actual standards
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# are applied to the ports, the calibration result is just random data
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# Set up the sweep first
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self.vna.cmd(":DEV:MODE VNA")
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self.vna.cmd(":VNA:SWEEP FREQUENCY")
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self.vna.cmd(":VNA:STIM:LVL -10")
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self.vna.cmd(":VNA:ACQ:IFBW 50000")
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self.vna.cmd(":VNA:ACQ:AVG 1")
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self.vna.cmd(":VNA:ACQ:POINTS 501")
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self.vna.cmd(":VNA:FREQuency:START 1000000")
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self.vna.cmd(":VNA:FREQuency:STOP 6000000000")
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self.vna.cmd(":VNA:CAL:RESET")
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# No measurements yet, activating should fail
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_1"), "ERROR")
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# Load calibration kit
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self.assertEqual(self.vna.query(":VNA:CAL:KIT:LOAD? DUMMY.CALKIT"), "TRUE")
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# Lets take the measurements for port 1 first
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self.vna.cmd(":VNA:CAL:ADD OPEN")
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self.vna.cmd(":VNA:CAL:ADD SHORT")
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self.vna.cmd(":VNA:CAL:ADD LOAD")
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self.vna.cmd(":VNA:CAL:PORT 0 1")
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self.vna.cmd(":VNA:CAL:PORT 1 1")
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self.vna.cmd(":VNA:CAL:PORT 2 1")
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self.cal_measure(0)
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self.cal_measure(1)
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self.cal_measure(2)
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# SOLT_1 should now be available
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_1"), "")
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# SOLT_2 and SOLT_12 should still be unavailable
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_2"), "ERROR")
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_12"), "ERROR")
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# Take measurements for SOLT_2
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self.vna.cmd(":VNA:CAL:ADD OPEN")
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self.vna.cmd(":VNA:CAL:ADD SHORT")
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self.vna.cmd(":VNA:CAL:ADD LOAD")
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self.vna.cmd(":VNA:CAL:PORT 3 2")
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self.vna.cmd(":VNA:CAL:PORT 4 2")
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self.vna.cmd(":VNA:CAL:PORT 5 2")
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self.cal_measure(3)
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self.cal_measure(4)
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self.cal_measure(5)
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# SOLT_1 and SOLT_2 should now be available
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_1"), "")
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_2"), "")
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# SOLT_12 should still be unavailable
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_12"), "ERROR")
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# Take the final through measurement for SOLT_12
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self.vna.cmd(":VNA:CAL:ADD THROUGH")
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self.vna.cmd(":VNA:CAL:PORT 6 1 2")
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self.cal_measure(6)
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# SOLT_1, SOLT_2 and SOLT_12 should now be available
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_1"), "")
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_2"), "")
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_12"), "")
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def assertTrace_dB(self, trace, dB_nominal, dB_deviation):
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for S in trace:
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dB = 20*math.log10(abs(S[1]))
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self.assertLessEqual(dB, dB_nominal + dB_deviation)
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self.assertGreaterEqual(dB, dB_nominal - dB_deviation)
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def test_SOLT_calibration(self):
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# This test performs a 2-port SOLT calibration with a connected LibreCAL
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# Afterwqrds, the calibration is checked with a 6dB attenuator
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# Set up the sweep first
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self.vna.cmd(":DEV:MODE VNA")
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self.vna.cmd(":VNA:SWEEP FREQUENCY")
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self.vna.cmd(":VNA:STIM:LVL -10")
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self.vna.cmd(":VNA:ACQ:IFBW 1000")
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self.vna.cmd(":VNA:ACQ:AVG 1")
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self.vna.cmd(":VNA:ACQ:POINTS 501")
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self.vna.cmd(":VNA:FREQuency:START 50000000")
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self.vna.cmd(":VNA:FREQuency:STOP 6000000000")
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self.vna.cmd(":VNA:CAL:RESET")
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# Load calibration file (only for standard and measurement setup, no
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# measurements are included)
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self.assertEqual(self.vna.query(":VNA:CAL:LOAD? LIBRECAL.CAL"), "TRUE")
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# Take the measurements
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cal = libreCAL()
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# Connections:
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# LibreVNA -> LibreCAL
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# 1 -> 3
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# 2 -> 1
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cal.reset()
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cal.setPort(cal.Standard.OPEN, 1)
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cal.setPort(cal.Standard.OPEN, 3)
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self.cal_measure(0, 15)
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self.cal_measure(3, 15)
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cal.setPort(cal.Standard.SHORT, 1)
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cal.setPort(cal.Standard.SHORT, 3)
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self.cal_measure(1, 15)
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self.cal_measure(4, 15)
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cal.setPort(cal.Standard.LOAD, 1)
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cal.setPort(cal.Standard.LOAD, 3)
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self.cal_measure(2, 15)
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self.cal_measure(5, 15)
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cal.setPort(cal.Standard.THROUGH, 1, 3)
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self.cal_measure(6, 15)
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# activate calibration
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self.assertEqual(self.vna.query(":VNA:CAL:ACT SOLT_12"), "")
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# switch in 6dB attenuator
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cal.setPort(cal.Standard.THROUGH, 1, 2)
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cal.setPort(cal.Standard.THROUGH, 3, 4)
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# Start measurement and grab data
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self.vna.cmd(":VNA:ACQ:SINGLE TRUE")
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while self.vna.query(":VNA:ACQ:FIN?") == "FALSE":
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time.sleep(0.1)
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cal.reset()
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# grab trace data
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S11 = self.vna.parse_VNA_trace_data(self.vna.query(":VNA:TRACE:DATA? S11"))
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S12 = self.vna.parse_VNA_trace_data(self.vna.query(":VNA:TRACE:DATA? S12"))
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S21 = self.vna.parse_VNA_trace_data(self.vna.query(":VNA:TRACE:DATA? S21"))
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S22 = self.vna.parse_VNA_trace_data(self.vna.query(":VNA:TRACE:DATA? S22"))
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# Attenuation is frequency dependent, use excessively large limits
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# TODO: use smaller limits based on frequency
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self.assertTrace_dB(S12, -13, 5)
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self.assertTrace_dB(S21, -13, 5)
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# Reflection should be below -10dB (much lower for most frequencies)
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self.assertTrace_dB(S11, -100, 90)
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self.assertTrace_dB(S22, -100, 90)
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