TECHNICAL SUPPORT NOTE. Recommended Settings. On VR5-HD for Automatic Phase Calibration

Transcription

1 TECHNICAL SUPPORT NOTE Recommended Settings On VR5-HD for Automatic Phase Calibration 1

2 Recommended Settings on VR5-HD For Automatic Phase Calibration This document describe when you are going to use external attenuators/long cables with large attenuate values to include into the calibration process of the MB5 system, several important parameters need to be considered to have a validate phase calibration results: Attenuators maybe used to protect the VR5 s input circuit when the enodeb transmit high output power, in this document, a 30dB attenuator will be taking into consideration. As you know, there are two stage for the phase calibration, initial calibration (initial setup of the new system, unless any cables/adaptors change, there is no need to do it over again), single/sweep calibration (this will be done at every time after each reboot of VR5). Initial Calibration: For initial calibration, we use VNA to do a S21/S12 measurement for the phase and calculate the delay value for all of the external cables include enodeb cables and UE cables, the VNA s port1 output power level setting is around 0dBm, when doing the calibration, the signals arrived at input port of VR5 is around -25~-30dBm, while the input expected power level is set by default -10dBm (this is fixed according to the design). when VR5 trying to pass the signal through the specific path, the measurement of the signal from input port becomes difficult as it is far away from the input expected power, in this situation, you will see below error : 2

3 When this error happens: 1, Check the cabling is correct from the instructions, check all the cable connections between VR5 and VR according to MB5 Setup Guide from HELP->Manuals->MB5 Setup Guide 2, As explained in the previous section, if the set input expected power level is far away from measured input power level, VR5 will not have a valid measurement, in order to improve the measurement, following below instructions to include the cable loss into the input port section as below: 3

4 When you want to introduce 30dB attenuation for the downlink, from our current design, if you input 30dB cable loss, the primary VR5 will be overloaded, and the measurement data will be distorted, this will not give you stable results, until we have a consolidated solution, the recommended value for Crest Factor and Cable Loss: - Cable loss, if you have 30dB attenuator, use 20dB at most, more than 20dB will make the primary VR5 became Overload. - Crest Factor, set this value to 25. Single or Sweep Calibration: After you finish the initial calibration, for single or sweep calibration: - If you load the Hybrid 8x2/1x8 topology, the cable loss will be reset to 0; in this case, you will not need to remove the 20dB cable loss. - If you keep the same topology, you will need to remove the cable loss and set it to 0, otherwise you will see overload on primary of the VR5. 4

5 - Leave the Crest Factor to 25dB. Better way to observe the VNA measurement result: As the VNA is under the bottom of the rack, you can use ENA web control functionality to observe the VNA measurement data from the same controller PC with VR5 in real time fashion. Instructions: 1. Open a new IE window, input the VNA s IP address by default: , you will see below window: 5

6 2. Click ENA Web Control : 6

7 3. Click Ok to accept the settings. 7

8 4. Press Enter 8

9 5. You will see the measurement data in a real time: 9

10 Cable loss setting when you are doing the verification of phase: After phase calibration process, if you want to verify the phase calibration results, better to put 20dB cable loss back to ensure the VR5 have better measurement result when there is 20~30dB attenuator connected at the enodeb cable end. After all the measurement is done, remove 20dB loss from cable loss column. Summary: Initial calibration Input the 20dB cable loss. Single /Sweep calibration remove the 20dB cable loss. Phase verification Input 20dB cable loss. Testing Remove 20dB cable loss. 10