vswr.vswr

Source code: vswr/vswr.py

VSWR measures the efficiency of the transmission line.

Description

SWR (Standing Wave Ratio) is the ratio of the amplitude of a partial standing wave at an antinode (maximum) to the amplitude at an adjacent node (minimum). SWR is usually defined as a voltage ratio called the VSWR, but it is also possible to define the SWR in terms of current, resulting in the ISWR, which has the same numerical value. The power standing wave ratio (PSWR) is defined as the square of the VSWR.

Why do we need VSWR?

A problem with transmission lines is that impedance mismatches in the cable tend to reflect the radio waves back to the source, preventing the power from reaching the destination. SWR measures the relative size of these reflections. An ideal transmission line would have an SWR of 1:1, with all the power reaching the destination and none of the power reflected back. An infinite SWR represents complete reflection, with all the power reflected back down the cable.

Test Procedure

Please see https://chromium.googlesource.com/chromiumos/platform/factory/+/HEAD/py/test/pytests/vswr/README.md

Dependency

This test measures VSWR value using an Agilent E5071C Network Analyzer (ENA).

Examples

For the format of vswr_config.yaml, please check https://chromium.googlesource.com/chromiumos/platform/factory/+/HEAD/py/test/pytests/vswr/vswr_config.sample.yaml.:

{
  "pytest_name": "vswr",
  "args": {
    "event_log_name": "vswr_prepressed",
    "config_path": "/usr/local/factory/config/vswr_config.yaml"
  }
}

Test Arguments

Name	Type	Description
event_log_name	str	Name of the event_log, like “vswr_prepressed” or “vswr_postpressed”.
config_path	str, None	(optional; default: None) Configuration path relative to the root of pytest vswr folder. E.g. path/to/config_file_name. Can use download_from_factory_drive pytest for downloading latest config files.
timezone	str	(optional; default: 'Asia/Taipei') Timezone of shopfloor.
serial_number_key	str	(optional; default: 'serial_number') The key referring to the serial number in question. This key will be used to retrieve the serial number from the shared data. Default key is serial_number.
keep_raw_logs	bool	(optional; default: True) Whether to attach the log by Testlog