Timing Interfaces Card with GNSS Module RF Input Requirements

• For optimal performance, the Timing Interfaces Card with GNSS module requires a GNSS antenna with built-in Low-Noise Amplifier (LNA). The antenna LNA amplifies the received satellite signals for the following two purposes:

  • Compensation of losses on the cable

  • Lifting the signal amplitude to the suitable range for the receiver frontend

  The amplification required is 22dB gain + cable/connector loss + Splitter signal loss.

  The recommended range of LNA gain (- cable/connector loss) is 22–30dB with a minimum of 20dB and a maximum of 35dB, at the connector of the receiver module.

• Timing Interfaces Card with GNSS module provides 5V to the active antenna through the same RF input.

• Surge requirement:

  • Timing Interfaces Card with GNSS modules have built-in ESD protections on all pins, including the RF-input pin. However, extra surge protection may be required if rooftop antennas are to be connected, to meet the regulations and standards for lightning protection of countries where the end-product is installed.

  • A lightning protection must be mounted at the place where the antenna cable enters the building. The primary lightning protection must be capable of conducting all potentially dangerous electrical energy to protective earth (PE).

  • Surge arrestors should support DC-pass and suitable for the Timing Interfaces Card with GNSS frequency range (1.575GHz) with low attenuation.

• Antenna Sky visibility:

  • Timing Interfaces Card with GNSS signals can only be received on a direct line of sight between antenna and satellite. The antenna must have a clear view of the sky. For proper timing, minimum of four satellites should be locked.

    Note	The antenna terminal should be earthed at the building entrance in accordance with the ANSI/NFPA 70, the National Electrical Code (NEC), in particular Section 820.93, Grounding of Outer Conductive Shield of a Coaxial Cable.

• Use a passive splitter if more than one Timing Interfaces Card with GNSS module is fed from a single antenna.

Note	The splitter should have at least one RF port capable of DC-pass, and an antenna should be connected to that port, if the antenna needs to feed power from 8000-TIC-GNSS.

Primary Reference Time Clock

As packet timing requirements emerged, the ITU-T developed the Primary Reference Time Clock (PRTC) standard for time and phase for transport over a packet network and this standard is known as G.8272.

Note	The performance specified in the following table also applies to the output of the combined PRTC and T-GM function when integrated into a single piece of equipment. Therefore, for both the PRTC-A and PRTC-B, there’s no additional (performance) allowance for the inclusion of the T-GM function.

There’s no standardized requirement for holdover, it’s up to the implementation. Some standalone PRTC devices have very-high quality quartz oscillators or even a Rubidium oscillator as an option to allow an option for extended holdover. Redundancy is provided through network design instead of relying on holdover performance from expensive oscillators.

According to the standards, there are only a few differences between the two classes of clock. Meeting those requirements may result in different implementations, which may influence the cost of the device.

To achieve improved performance, PRTC-B is typically implemented with a two-band GNSS receiver instead of a single-band receiver. The “traditional” band for GPS signals in the L1 band, while the newer devices receive signals in the L2 band.

Timing Interfaces Card Ports Specification