What are the advantages of a dual-band receiver in time synchronization applications where service outages are not tolerated?

Time synchronization, a crucial element of mobile telecommunications and other strategic infrastructures, often falls victim to issues such as jamming that can disrupt the accurate reception of signals. To address these challenges, the world’s best-in-class time stability and robustness are offered in one package by the GT-100 dual band GNSS receiver. Critical infrastructure sectors like telecommunications, financial services, and utilities work around the clock, and disruptions to these services can have significant national security implications. The following is an excerpt from a technical white paper authored by our engineer specializing in time synchronization.

Figure 11 below illustrates the number of positioning satellites received by the GT-100 when configured so that only L1 signals are received in the presence of jamming in the vicinity of 1575 MHz from an external source. In this test, the receiver was able to maintain the number of positioning satellites up to a J/S ratio of about 80 dB thanks to the effectiveness of its anti-jamming function, but it was unable to continue receiving GNSS satellite signals beyond that.

Next, Figure 12 illustrates signal strength when the GT-100 was configured to simultaneously receive both L1 and L5 signals in the presence of L1 band jamming from an external source. The red line indicates the average signal strength of L1 signals, while the blue line indicates the average signal strength of L5 signals. Strong jamming was present in the L1 band while the black dotted line was equal to 1. The results indicate that while the receiver had difficulty receiving L1 signals when strong jamming in the L1 band compromised signal strength, it was able to continue receiving L5 signals without issue. Figure 13 illustrates the number of positioning satellites, indicating that while the number of L1 signal satellites fell to 0, the number of L5 signal satellites remained unchanged. Furthermore, Figure 14 illustrates 1PPS output under the same conditions, depicting stable 1PPS output thanks to the receiver’s ability to continue receiving L5 signals.

In this way, the GT-100 dual band receiver can maintain its time performance in an appropriate manner even when there’s jamming in the vicinity of the L1 band, a task that had been difficult until now, by using L5 signals.

Incidentally, the GT-100 is designed to make the most of this robustness in the face of jamming by allowing L1 and L5 signal searches to be carried out completely independently of each other. In fact, L5 signals have higher resolution than L1 signals, which improves positioning accuracy, but it’s known that the improvement is offset by a more time-consuming search process. Consequently, some available dual band receivers first search for L1 signals, receive navigational messages known as ephemeris and almanac data, and identify those satellite positions before they can start to search for L5 signals. As a result, if L1 signals cannot be received due to jamming, those units are unable to start searching for L5 signals, halving their ability to resist jamming. In contrast, when the GT-100 determines automatically that it is in an environment in which L1 signals can’t be received, it starts searching independently for L5 signals, which it can do because its design doesn’t require L1 signal reception as a precondition for searching for L5 signals.

Above is an excerpt from our technical white paper.
You can view the full white paper by downloading it from the URL below.

https://pages.furuno.com/en-gt100-dualband-robustness-downloadform.html

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