Paragon-neo: 1PPS Input Accuracy

Paragon-neo has unbalanced and balanced 1PPS measurement and reference ports as illustrated in the simplified diagram below. Paragon-neo software selects the 1PPS signal source, either using an API call or GUI selection.

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Paragon-neo balanced and unbalanced 1PPS inputs are accurately calibrated during manufacturing meaning the constant latency of the converter IC is compensated for. However, dynamic latency variation through the converter IC up to 3ns cannot be compensated out, but can be avoided by using the unbalanced 1PPS input instead of the balanced input. The dynamic latency is due to operating temperature variation and input signal voltage.

The diagram below shows four connection configurations for 1PPS signals into Paragon-neo reference inputs. Configurations 1 and 2 also apply to Paragon-neo measurement inputs.

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Configuration 1 (any Paragon-neo software release)

This configuration is applicable in three test scenarios:

1. During BC, TC and subordinate tests, Paragon-neo is required to measure 1PPS and ToD outputs from the DUT.
   The DUT outputs an unbalanced 1PPS signal and an RS232 ToD signal. The Opt. 133 converter unit converts the signals and merges them into one cable for connection to a Paragon-neo RJ48 measurement port. The 1PPS signal passes through two conversions: one in the Opt. 133 converter box and another in Paragon-neo.
   
   

2. When testing PRTC and APTS devices, Paragon-neo requires 1PPS and ToD reference signals.
   A GNSS simulator provides 1PPS and ToD reference signals into Paragon-neo that align with the GNSS RF signal to the device under test.
   
   The Opt. 133 converter unit converts the reference signals and merges them into one cable for connection to a Paragon-neo RJ48 reference port. In this case, the propagation delay through the Opt 133 converter unit and cables must be compensated for. Please refer to https://calnexsolutions.atlassian.net/wiki/spaces/KB/pages/1807122433/Paragon-neo+Option+133+how+to+measure+1pps+propagation+delays. Later versions of the Opt. 133 converter unit have a calibration sticker showing the propagation delay measured at room temperature before shipping from Calnex.
   
   The 1PPS signal passes through two conversions: one in the converter box and another in Paragon-neo.
   Consider using configuration 3 or 4 to avoid using the Opt. 133 Converter in line with the 1PPS reference signal.
   
   

3. During BC, TC and Subordinate tests when a Calnex Opt. 132 Rubidium reference source is used.
   The Opt. 132 Rubidium device outputs RS232 ToD and 1PPS signals that can be merged into one cable using the Opt.133 converter and connected to the Paragon-neo RJ48 reference port. In this case, there is no need to compensate for the Opt.133 converter propagation delay because the device under test is referenced to the Paragon-neo output signals, not the Opt. 132 reference signal or other external reference source.
   Consider using configuration 4 instead of configuration 1.

Configuration 2 (any Paragon-neo software release)

This is recommended over Configuration 1 because the 1PPS signal connects directly to Paragon-neo without any conversion. Configuration 2 allows accurate 1PPS phase measurement but no ToD measurement.

Configurations 3 & 4 (Paragon-neo software release R11 and later)

These configurations enable a ToD reference to be used along with the more accurate unbalanced 1PPS reference connected to the BNC port. Paragon-neo can accept an RS422 ToD input directly, or an RS-232 ToD signal via the Opt.133 converter.

Configuration 4 also applies when the Calnex Opt.132 Rubidium reference source provides the reference signals into Paragon-neo. The 1PPS reference is connected directly from the Opt.132 device to Paragon-neo while the ToD signal passed through the Opt.133 converter for RS232 to RS422 conversion.