AnsweredAssumed Answered

Antenna transmission measurement problems.

Question asked by dhamilton on Jul 18, 2013
Latest reply on Jul 23, 2013 by Dr_joel
I am having an issue in the simple measurement of an antenna transmission measurement.   I have two log periodic antennas 2 meters apart.    The antenna's have a gain of 6dBi each.   Based on theoretical calculations the loss of the system should be approximately 27.7 dB.  This based on 39.7 dB loss in free space air + 12 dB gain.   I have three analyzers measuring this set up.   8720B/001/010, 8720ES/010/012/089, and an E8364B/010/014/016/080/081/083/UNL.   I am using 2 meter low loss Gore network analyzer cables.  All three units have been fully calibrated per MFR specifications.  The antenna has a VSWR of 1.5 @ 1 GHz.  The 8720B measures the corrected loss of the antenna system @ 29.7 dB.  The PNA measures the corrected loss @ 27.6 dB.  The 8720ES measures the loss @ 49.3 dB.   All units are set to default power, -10 dBm for the 8720B, +5 dBm for the 8720ES, +10 dBm for the PNA.  All units are set to the same IF BW, data points and any other relevant parameter for comparison.  I checked the 8720ES for raw coupler return loss and source match to see if this is could be a problem as this unit measures low on both ports (S12,S21)and within .3 dB of each other.   All units were also tested for noise floor and were well within expected parameters.   Is there a hardware difference in the ES model that would cause this problem?  Is there a setting in the ES that I missed?  In the transmission correction, I just did a simple thru calibration at the ends of the cable system before the antennas.  There are no amplifiers or other devices in line except the cables to the test ports only.  Dr. Joel, I hope you can help explain this one. 

Thanks, Dave