Description:1 Title of the Invention
Radio Frequency Aircraft Interface System for Reception and Uniform Distribution of Multi Frequency GNSS Signals.

2 Field of the Invention
The invention relates to design and development of Radio Frequency (RF) aircraft interface system comprising GNSS Active Antenna, GNSS Active RF power splitter and GNSS Passive RF power splitter for reception of multi frequency Global Navigation Satellite System (GNSS) signal and provisioning for uniform distribution to multiple receivers for airborne application.

3 Background of the Invention
Various global navigation satellite systems (GPS,GLONASS etc.) have been used extensively for providing navigation, positioning and time information across the world for air vehicles, ships, missiles and Geographic Information System (GIS). After operationalization of Indian regional satellite constellation known as IRNSS, majority of aircraft flying over the Indian airspace may utilize IRNSS for better availability and accuracy. To acquire multi-constellations i.e. GPS, GLONASS, and IRNSS RF band signals, the Airworthy standard Antenna and Splitters are developed, which can acquire and feed the RF signals to the Navigation signal receivers onboard to air vehicles, ships and other assets. The GNSS Antenna is capable of receiving GPS,GLONASS and IRNSS band RF signals. The signal received through GNSS Antenna is fed to Active RF power splitters and further Passive RF power splitters for uniform distribution to various RF consumers installed on Air Vehicle. The compositional items are qualified for Airborne applications.

4 Brief Summary of the Invention
The invention relates to design and development of RF network compositional items for reception of multi frequency GNSS signals and provisioning for uniform distribution to multiple receivers. The RF network compositional items comprises, GNSS (GPS+GLONASS+IRNSS) band airborne Antenna, Active and Passive Splitters. The developed product fulfils all the airworthy qualification requirements and it can be used for Aircraft, Helicopter, UAVs and other airborne applications. The GNSS antenna is used to receive the RF signals in the operating bands of GPS, GLONASS and IRNSS of standard accuracy. It is an active antenna which provides amplification to the received RF signals. The active Splitter, splits an input RF signal coming from GNSS antenna evenly into four outputs connected to four different receiving units. Receiving units can be any RF processing or navigation receiver units. The active splitter provides amplification to the incoming RF signal and also provides +5V DC supply to an active GNSS antenna through input RF port. Similarly, the passive splitter can also splits an input RF signal evenly into four outputs connected to four different receiving units. The GNSS entire network ensures phase and amplitude imbalance within acceptable levels for all consumers. Further, the network is designed in a way to ensure the minimum return loss and required strength even at nearest and farthest point of distribution network.

5 Detail Description of the Drawings
Figure 1: It shows the interconnection diagram for GNSS RF network. The network comprises GNSS Antenna (1), GNSS Active Splitter (2), GNSS Passive Splitter(s) (3). The RF signal (4) is received through GNSS Antenna and distributed to consumers through active and passive splitters via interconnecting cables (5),(6),(7),(8),(9),(10).
Figure 2: It shows the outline diagram for GNSS Antenna. The top view (11) and side view (12) (13) of the same is indicated in figure. The RF connector (14) on antenna is also indicated.
Figure 3 It shows the outline diagram for Active RF Power Splitter. The top view and side view of the same is indicated in figure. The Power connector (15), input signal RF connector (16) , output signal RF connector (17),(18),(19),(20) and mounting screw (21) are also indicated.
Figure 4 It shows the outline diagram for Passive RF Power Splitter. The top view and side view of the same is indicated in figure. The input signal RF connector (22) , output signal RF connector (23),(24),(25),(26) and mounting screw (27) are also indicated.

6 Detail Description of the Invention
This invention involves the design and development of GNSS Antenna (1), Active (2) and Passive Splitters (3) of airworthy standard. The developed product fulfils all the airworthy requirements of high performance aircraft. The technical details of each product is described as follows:

GNSS Active Antenna
The GNSS antenna is used to receive the RF signals (4) in the operating bands of GPS, GLONASS and IRNSS of standard accuracy. The GNSS antenna (1) is designed with three layer Stacked Patch Antenna works in the frequency range of 1160-1190MHz, 1217-1238MHz, 1240-1252MHz, 1565-1610MHz, 1598-1606MHz and 2482-2502MHz. The GNSS antenna includes an in-built Low Noise Amplifier (LNA) with low Noise Figure (NF=2.5dB) and Gain of 35dB and 30dB in L & S bands respectively. The active antenna is energized by the 5V DC voltage. It supplies RF signal to active power splitter via interconnected cable (5)..

GNSS Active RF Power Splitter
The Active Splitter is a one input, four output device. It operates in the frequency band of 1150MHz-1620MHz and 2400MHz-2600MHz. It splits an input RF signal (5) coming from GNSS antenna evenly into four outputs (6),(7),(10). An active splitter provides amplification to the incoming RF signal and also provides 5±0.1V DC supply to energize the active GNSS antenna. The Active Splitter is designed with 4-way microstrip mode. It has in-built LNA to amplify the RF input signal and splits equally in 4-output ports. The LNA has Low Noise Figure (NF<1.7dB) and having gain of 20dB.The 4-way microstrip design having Low Amplitude Imbalance (0.5dB) & phase imbalance (4 º) and having good return loss (15dB).

GNSS Passive RF Power Splitter
The passive splitter is a one input, four-output device. It operates in the frequency band of 1150MHz-1620MHz and 2400 MHz-2600 MHz. It splits an input RF signal coming from Active Splitter (6) evenly into four outputs (8),(9).The passive splitter is designed with 4-way microstrip mode. The passive splitter designed for low insertion loss (<7dB). It also has low amplitude imbalance (0.5dB), phase imbalance (4 º) and having good return loss (15dB).

Architecture for uniform distribution to multiple GNSS receivers
The GNSS Antenna (1) is capable of receiving GPS,GLONASS and IRNSS band RF signals. The signal received through GNSS Antenna is fed to Active RF power splitters (2) and further Passive RF power splitters (3) for distribution to RF consumers installed on Air Vehicle. The compositional items are qualified for Airborne applications. The pictorial representation of interconnected set is shown in Figure-1. As described in the figure, the RF signal (4) is received from Satellite to GNSS Antenna (1). The received signal is passed to Active RF power splitter (2) and passive power splitter (3). The RF power consumers can take these signals from output ports of splitters.
, Claims:We Claim:

1. A Radio frequency (RF) aircraft interface system for reception of multi frequency signals for Air vehicle applications comprising:
a GNSS active antenna (1);
a GNSS active RF power splitter (2) connected to GNSS active antenna (1) by means of RF cable; and
a GNSS passive RF power splitter (3) connected to GNSS active RF power splitter (2) by means of RF cable.