How to prevent signal loss on a GPS/GNSS system?
GNSS signals are typically weak by the time they reach Earth and are vulnerable to attenuation on their final journey between antenna and receiver. Receivers require a minimum GNSS signal strength (Gain) to operate which, if not achieved, can severely impact on their performance.
Losses along coaxial cable can reduce the Gain and the longer the distance of coaxial cable then the higher the Gain loss. Losses are caused by a multitude of factors impacting the cable, such as signal interference, internal resistance, loss due to moisture entry, cable loss due to flexing and cable degradation. All these factors cause Gain losses which impact the ability of the receiver to provide accurate PNT data.
This can be managed through the use of high quality, more expensive cable but the simplest and most cost-effective solution is the use of amplification to increase the Gain from the antenna before the signal enters the cable run. The amplified Gain still experiences the same level of cable loss but can complete the journey to the receiver with the sufficient Gain required for operation.
Alternatively, if amplification cannot provide sufficient Gain for longer cable runs, there are methods of changing signal characteristics that enable passage over distances of up to 1.5km.
Placing amplification as close to the antenna as possible results in a higher gain entering the coaxial cable run therefore, despite the impact of the signal loss along the cable, a high enough Gain still reaches the receiver unit. The Inline amplifiers are capable of amplifying all GNSS frequencies and will improve performance on receivers with cable lengths of over 15 metres.
Lower frequencies generate less loss! The GPS DOWN/UP Converter comprises of two units, a GPS antenna/DOWN-converter and an UP-converter. The DUC-1 DOWN antenna receives the signal and converts it into a lower frequency, this lower frequency can then travel along a longer length of coaxial cable. Before the gain is sent to the receiver, the DUC-1 UP converter converts the signal back to the original frequency. The system makes it possible for long cable runs of up to 450 metres.
Fiber-optic solution for extremely long cable requirements, the RVL-1 unit converts the antenna gain signal into light, this is then sent down the multimode fiber cable resulting in minimal Gain losses. Consisting of a transmitter and receiver, the RVL-1 kit covers frequency ranges from 800 MHz to 1800 MHz and passes all the GNSS frequencies.