TITLE OF THE INVENTION

MSS TRANSMITTER(TX)-RECEVIER(RX) TERMINAL FOR AIRBORNE PLATFORM

Technical Field of the Invention:
[001] The present invention generally relates to the field of wireless signal communication. More particularly the present invention relates to Mobile Satellite Services (MSS) transmitter-receiver terminal configured to provide essential communication to and from an airborne platform to a ground based control station also referred as hub stations within the footprint of Satellite. The invention is more primarily focused on using mobile satellite service (MSS) for Indian terrain.
Background of the Invention:
[002] Terrestrial VHF / UHF networks have made use of high power transmitters covering broad services, which enable one-way broadcast of content to user equipment such as televisions and radios. By contrast, wireless telecommunications networks have made use of low power transmitters, which cover relatively small areas. Unlike broadcast networks, wireless networks may be adapted to provide two-way interactive services between user equipment such as telephones and computer equipment.
[003] Wireless networks (e.g., wide-are a-net works (WANs)) ac cellular networks (e.g. global system for mobile communications (GSM) networks, universal mobile telecommunications system (UMTS) networks, etc) are not fully covered by network operators especially in geographical areas like India. The wireless network coverage in these areas has limited reception of wireless signals and therefore there is no possibilities to make a voice or data call using a mobile phone.
[004] Use of wireless telephone service is widespread, However, wireless telephone service
may be interrupted when wireless base stations providing wireless telephone service become
inoperable. In some situations, a wireless service provider may quickly restore wireless
telephone service by repairing an inoperable base station.
However, in other situations, natural disasters or other events may prevent the wireless service provider from restoring service for an extended period. During these times of service outage, people might not be able to call an emergency operator using a wireless phone. Consequently, loss of property, severe injury, and/or death may result.

[005] Communication is central to managing situations in a hostile environment, especially in context of a military operation or any emergency situation. Lack of communications and situational awareness paralyzes command and control. Accordingly, there is a need for real¬time data that is driving the integration of radio and satellite technology into both commercial and military communication systems,
[006] Communication over an unreliable public network, however, can provide certain advantages. Public networks such as the Internet, provide an inexpensive and ubiquitous for communication, enabling an entire host of users to communicate directly with each other in a way unmatched by any private network. However, since the communications are public, any party can intercept and read the messages sent, which leads to insecurity of communicated data.
[007] Today's armed forces are fast, mobile, tightly integrated and closely coordinated, which requires the ability to quickly and freely communicate across territorial boundaries as well as international boundaries. Hence there is a need to provide such MSS network with a number of ground-based, shipboard, and airborne terminals, which essentially provide communication to and from remote areas, where there is no communication available. This enables seamless communication to/from the mobile platforms within the foot print of Indian satellite.
Summary of the Invention:
[008] The MSS Tx- Rx Terminals are used for signal communication to send short messages from any stationary/ moving platforms to a stationary hub station through MSS transponder of Indian Satellite is disclosed. According to first aspect of the present invention, the MSS Transmitter (Tx) - Receiver (Rx) terminals operates in S X C and C X S links.
[009] According to the first aspect, the MSS terminal for communication enables from the mobile Tx terminal where the data is transmitted in S-band to the Satellite, which in turn, sends this data in C-Band to the ground based hub station. The reporting terminal has a built-in GPS receiver working in L-band frequency. Location information (Coordinates) of the mobile platform received from the GPS Satellites and the same is stored in the memory, and retransmitted in S-band to Indian Satellite. The Satellite transmits the same to the ground based hub station in C- band. This data enables the user to continuously monitor the location of the

mobile platform, in addition to receiving short message from the mobile platform, the communication from the hub station to the moving platform; a high sensitivity receiver in S-band is used to receive the data from the satellite. In this case, a message from the hub is first sent to the satellite in C - band, which in turn, sends the message in S-band to the moving platform.
[0010] According to the first aspect, the MSS terminal is programmable to operate either in Aloha or TDMA modes, which are suitable for sending low-density messages. Each transmit terminal with unique ID code operates in S-band and transmits messages at multiple bits per second (bps) speed.
Brief Description of the Drawings:
[0011] Other objects and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments, in conjunction with the accompanying drawings, wherein like reference numerals have been used to designate like elements, and wherein:
[0012] Referring to FIG. 1 is a block diagram of system and process of present invention.
[0013] Referring to FIG. 2 is a block diagram of MSS Tx- Rx Terminal
[0014] Referring to FIG. 3 is a block diagram of antenna unit of the MSS terminal.
[0015] Referring to FIG. 4 is a block diagram of the Transmitter section of the MSS terminal.
[0016] Referring to FIG. 5 is a block diagram of the receiver section of the MSS terminal
[0017] Referring to FIG. 6 is a block diagram of the Interface to processor of the MSS terminal
Detailed Description of the Invention:
[0018] Exemplary embodiments of the present invention are directed towards a MSS terminal and a method for signal communication to and from an airborne platform to a ground based control (Hub) station within the footprint of Indian satellite is disclosed. According to a first aspect of the present invention, the MSS terminal for communication enables from the mobile Tx terminal where the data is transmitted in S-band to the Satellite, which in turn, sends this data in C-Band to the ground based hub station. The reporting terminal has a built-in GPS

receiver working in L-band frequency, Location information (Coordinates) of the mobile platform (Airborne) received from the GPS Satellites and the same is stored in the memory, and retransmitted in S-band to Indian Satellite. The Satellite transmits the same to the ground based hub station in C- band. This data enables the user to continuously monitor the location of the aircraft, in addition to receiving short message from the mobile platform, the communication from the hub station to the moving platform; a high sensitivity receiver in S-band is used to receive the data from the satellite. In this case, a message from the hub is first sent to the satellite in C - band, which in turn, sends the message in S-band to the moving platform.
[0019] FIG 1. illustrates a block diagram of system and process of present invention, the System 100 comprises a GSAT- 2 (CXS & SXC Transponders) 101. an aircraft 102, a C-Band Hub Station 103, MSS Tx- Rx Terminal 104 and a Computer 107 having Processor 108.
[0020] According to the first aspect of the invention, the system comprises the following modules.
[0021] Antennas (Tx, Rx & GPS) 105
[0022] Tx Rejection Filter 120
[0023] Low Noise Amplifier (LNA) 121
[0024] Intermediate frequency IF Down Converter 122
[0025] Demodulator & Decoder 123
[0026] Synthesized!3
[0027] Base Band Control Card 119
[0028] BPSK Modulator U 4
[0029] Solid State Power Amplifier (SSPA) 115
[0030] Tx Band Pass Filter 116
[0031] DC- DC Converter 112
[0032] Computer 107
[0033] As described above in the MSS Tx- Rx Terminal 104 comprises, an antennas -
Transmitter (Tx) 110, Receiver (Rx) 111 and Global positioning system (GPS) 109 which are
structured in rectangular patch used for transmitting and receiving S-band signals. Provision is
created for placing the Tx and Rx antennas separately on the antenna plate along with the GPS

patch antenna. GPS antenna is also a square patch in structure. Tx-Rx antennas are compact in size and have wide beam width +45°.
[0034] As shown in Fig 2, the MSS Tx- Rx Terminal 104 further comprises, TRE Section 124, Antenna Section 105. The TRE Section further comprises: the MSS Transmitter 110, the MSS Receiver 111, GPS receiver 109 sections and Processor 108.
[0035] The MSS Rx Section 111 further comprises Tx-Reject filter 120 prevents the Tx frequency (2670MHz to 2690MHz) signal from entering into the receiver with a rejection of 35 dB min. It passes the Rx frequency band of 2510MHz ±10MHz with minimum loss. It is a 3-section cavity filter. LNA section 121 consists of a low-noise amplifier (LNA ST1), Image rejection filter, Mixer 1, LNA ST2 and an IF-Amplifier (IF1-A1). The S-Band signal passes through LNA ST1, Image reject filter & LNA ST 2 and gets down converted to 70.01 MHz by the Mixer 1. The LNA module gives a gain of 51 dB (45 dB min), according to an exemplary embodiment of the present invention.
[0036] As described above in the system further comprises, IF down converter section 112 converts IF-1 (70,010MHz) to IF-3 (9 KHz with double down conversion) with a gain of 65dB approx. It consists of two sub sections called LO block and Down converter. The LO block generates required LOs for down conversion. In the first stage of conversion, the incoming 70.01 MHz signal is down converted to 455KHz using a LO of 69.555MHZ(LO~2). In the second stage, the 455 KHz is down converted to 9 KHz using LO of 464 KHz (LO-3). The LO-2 and LO-3 are DDS based LOs. A micro controller is incorporated in LO block to generate necessary controls for frequency generation. The LO block also generates S band LO (LO-1) for S to 70 MHz down conversion which is performed in LNA section 121. LO-] is a PLL synthesizer and it is a separate PCB in LO block. This section requires +5V and ±12V DC supply, which is supplied from the DC-DC converter section 112, Output of current sense amplifiers (for indication of current drawn by the subsystem) of all subsystems are terminated at analog ports of the micro-controller incorporated in LO block for BITE operation. The IF OUT (IF-1) from LNA section is applied as input to this section. This signal passes through an IF amplifier with a gain of 15 dB min. Output of U3 passes through a BPF 117 with an insertion loss of 15dB approx. Out put of BPF passes through 2 stage IF amplifiers with a gain of 20 dB each. This amplified 70.01MHz signal is down converted to 455 KHz by Mixer 2

with a conversion loss of 6dB approx, Then this 455 KHz signal is amplified, filtered through 455 KHz BPF with an insertion loss of 4dB approx. This 455 KHz signal is amplified and subsequently down converted to 9 KHz by using Mixer3. This down converted 9 KHz signal passes through a low pass filter. Later this 9 KHz signal is amplified, according to an exemplary embodiment of the present invention.
[0037] As described above, the MSS Rx Terminal 111 further comprises demodulator and decoder 123 which accepts 9KHz±5KHz signal from down converter section with a level of -20dBm (1.3 V peak-peak). The signal is digitized and is inputted to DSP processor, which demodulates the BPSK modulated signal and gives out hard decision data along with synchronized clock. This hard data and clock goes to FPGA that performs UW Detection, Differential Decoding, FEC (Forward Error Correction) and descrambling. Data and clock from FPGA goes to Micro Controller, which perform reverse ITB and sends serial asynchronous data (RS-232 level) to processor board.
[0038] As described above, the MSS Tx Terminal 110 comprises a said module a Frequency synthesizer 113 with external Reference from TCXO and frequency of oscillations from external VCO. The over all function of this module is to make VCO stable at the programmed frequency, which will be in the required frequency channel. The synthesizer 113 comprises of VCO, PLL IC and LOOP FILTER, The VCO produces a RF output, which is fed back to the PLL chip. Phase detector in the PLL compares the RF output from the VCO and reference input from external TCXO and takes the difference between the two outputs and produces a constant output when the two phases are equal. The constant output from the phase detector is applied as input to loop filter, which produces voltage that is fed to VCO. The VCO produces a constant RF output. Under the locked condition PLL produces a lock detect output which is of voltage level depending on the power supply input to the PLL chip. The synthesizer output is fed to a BPSK modulator 114. The other end of the modulator is fed from a bipolar circuit.
[0039] As described above, the MSS Tx Terminal further comprises a base band control card 119 which functionally includes reception of GPS Position and transmission of Text/GPS messages through serial port communication. Application interface is provided to the user to configure the frequency and ID from which the data is be transmitted. In Aloha mode, the message is transmitted three times randomly. In TDMA mode, the terminal waits for its time

slot. This control circuit also monitors the status of the synthesizer and SSPA 115. In the power ON condition, the terminal will be working with the default settings loaded in to it such as, synthesizer frequency and the transmission mode will be TDMA.
[0040] The Terminal further comprises SSPA 115 which comprises a driver amplifier which operates in the frequency range of 2670 - 2690 MHz. It is a two-stage amplifier. Both stages offer gain of 18 dB each. The matching circuit is realized using micro strip technology. Power output of the Driver amplifier is 18 dBmt Pre-matched and low current consumption devices are used to realize requisite gain. Both these stages operate on single 5V supply and a final Amplifier which operates in the frequency range of 2670-2690 MHz. It is a two stage amplifier and offers total gain of 22 dB. Directional coupler at the output produces DC voltage corresponding to the RF output power. The DC voltage available at directional coupler is used to generate a TTL command for the health status of the final amplifier (SSPA). The final amplifier (SSPA) operates on -5V&+10V supply. The SSPA is operational only during bursts. The SSPA 115 operates in the S-band frequency. It is a linear amplifier comprising of 4 stages. In first two stages, which together constitute driver stage, give a total output of 35dB gain. The first two used high performance SiGe HBT MMIC amplifier. The third and final stages use GaAs FETs providing gain of 23 dB. A directional coupler at the output produces DC voltage corresponding to the RF output. The DC voltage available at directional coupler is used to generate a TTL command for the health status of the SSPA 115. It converts detected RF signal to DC voltage and the same voltage fed to comparator circuit as one of input. The isolator 116 provides isolation protection of SSPA against high VSWR.
[0041] As described above the terminal further comprises Tx BPF 117 which is a 4-Section cavity filter passes Tx frequency only and has a rejection of 60dB and for Rx band to eliminate saturation of high sensitive LNA.
[0042] As described above the MSS Tx terminal further comprises a sequential card 118 which generates -5V, +5V &+10V for SSPA 115 from input supply voltage of +12V. It operates in burst mode. This card has SSPA status monitoring circuit. The reference voltage comes from SSPA, with reference to this voltage, the circuit generates TTL command and it goes to Base band control card 119 for monitoring health status of SSPA. LM 29502 low drop

voltage regulator is used for getting optimum performance, as it is a switching regulator, according to an exemplary embodiment of the present invention.
[0043] As described above, the system comprises of processor 108. The processor board has on-board CPU with sufficient memory to run Windows based applications. The processor board has an Ethernet interface, KVM (Keyboard-Video-Mouse) interface, USB and RS232 interfaces. The MSS Trans-Receive Electronics unit 104 is connected to Processor board over two RS232 interfaces, one for message transmission and another for message reception. Ethernet connector provides interface between the processor and MCDS. 2 RS-422/485 ports are provided for futuristic use of introducing encryption feature, if required. Interface to processor are shown in figure 6.
[0044] The processor board is installed with Windows server operating system, which provides full windows API and supports full range of device drivers written for Microsoft windows, Tx-Rx Server and Tx-Rx Client applications are installed. In addition, for database, My SQL Server 5,0 is also installed. Tx-Rx Server is configured to run as windows services on Windows start-up. Tx-Rx Server utilizes the MySQL database for storing messages,
A) Windows Server Embedded version with Remote Desktop Services and Test
Software for MSS are initially loaded in compact flash memory at Avantel and the same is inserted in the processor board, which is part of TRE-P 3 24, TRE-MCDS Interface diagram is shown in figure 6,
B) Client Software will be loaded into the TRE-P using File Transfer Protocol. The
Ethernet cable connected between TRE-P and MCDS will be opened and the same
will be used to load software/application into the TRE-P,
[0045] As described above, the system further comprises, MSS Transmit-Receive Messaging Client software/application is installed on the processor board using File Transfer Protocol. The Ethernet cable connected between TRE-P and MCDS will be used to load software into the TRE-P. The client software/application provides a GUI interface to the user for performing the various functions of the system. The software interfaces the Transmit and Receive Units for sending and receiving messages.
[0046] The MSS Air-borne system receives the packets sent by Hub and processes the data, reconstructs the packets to messages. These messages are then stored in a database.

[0047] Messaging Interfaces are provided for different types of messages (Text, GPS, and Standard Messages) using which, the user can edit and transmit messages. The messages can be typed in and submitted for delivery even when the system is in offline mode. These messages will be transmitted by the system after it goes online. The messages are broken down to packets and these packets are then transmitted in random order to a MSS Hub. These packets are received by the NMS at the Hub. The NMS analyzes the packet and broadcasts it to the destination Transmit-Receive System (Aircrafts). At the destination, the Transmit-Receive Messaging Client holds the packet in memory until all the packets in the message is received. The message is then reconstructed from these packets and stored in a database. A Graphical user interface (GUI) is provided for viewing the various messages and reports on the data received from aircraft / hub.
[0048] In accordance with an exemplary embodiment of the present invention, MSS tx- Rx terminal can be used for airborne platform
[0049] Exemplary specifications of the MSS terminal are listed below:

Parameter Specification
Frequency band Transmit frequency Receive Frequency 2670-2690 MHz 2500-2520 MHz
Step Size 10 kHz
Frequency Stability ±0.5ppm
Transmit Parameters
Transmitter Power out put 8W±ldB
Message length 200 Characters max.
Message transmission TDMA or ALOHA
Transmission rate 600 bps
Information rate 300 bps
Format HDLC
Error protection I6bitCRC

Error correction Rate Vi FEC
Modulation BPSK
Harmonics -30dBc min,
SSB Phase noise
Offset From carrier SSB Phase noise
@ 100 Hz -60dBc / Hz max
@1000 Hz ~65dBc / Hz max
GPS Receiver Built-in
Receiver Parameters
Type Heterodyne Multi-stage, Down Conversion
Input S-Band Signal of-136dBm Minimum
Output Serial Data
Modulation BPSK
Coding Rate Vi FEC
Information Rate 300bps
Antennas
Transmit Antenna
Frequency 2670-2690 MHz
■ Type Patch
■ Gain 6dBi (typ)
■ 3.0 dB Beam Width 90°
■ Connector SMA(F)
Receive Antenna
■ Frequency 2500-2520 MHz
■ Type Patch
■ Gain 6dBi (typ)
■ 3.0 dB Beam Width 90°

Error correction Rate Vi FEC
Modulation BPSK
Harmonics -30dBc mii\.
SSB Phase noise
Offset From carrier SSB Phase noise
@ 100 Hz -60dBc / Hz max
@1000 Hz -65dBc / Hz max
GPS Receiver Built-in
Receiver Parameters
Type Heterodyne Multi-stage, Down Conversion
Input S-Band Signal of-136dBm Minimum
Output Serial Data
Modulation BPSK
Coding Rate Vi FEC
Information Rate 300bps
Antennas
Transmit Antenna
Frequency 2670-2690 MHz
■ Type Patch
■ Gain 6dBi (typ)
■ 3.0 dB Beam Width 90°
■ Connector SMA (F)
Receive Antenna
■ Frequency 2500-2520 MHz
■ Type Patch
• Gain 6dBi (typ)
■ 3.0 dB Beam Width 90°

■ Connector SMA (F)
L-Band (GPS)
■ Frequency 1575.42 MHz
- Type Patch
■ Connector SMA (F)
Processor board
Processor Atom N270 1.6 GHz
Chipset Intel QG82945GSE+NH82801GBM
Memory 1GB RAM
Onboard video Support VGA/18/24-bit TFT LCD and EL screen
Network 2x 10/100/1000 Mbps Ethernet controller
10 interface 4x USB, 2 RS232,2 RS 422/485
Flash storage Ix Compact Flash socket, 2x SATA
Power Supply Input
Input voltage 28 V DC
Power consumption < 128 W in transmission mode
< 100 W in non-transmission mode
[0050] As will be appreciated by a person skilled in the art, the present invention provides a wide variety of advantages. Firstly, the system is suitable for working on multiple platforms, Secondly the antennas are designed for all environments and meet mission requirements that demand flexibility and mobility. Thirdly the antennas are light in weight. Finally the system has a facility to monitor and control the terminal through remote interface.
[0051] While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims:
1. A satellite-based communications system wherein communications between a user terminal and a hub station occur using an uplink band of frequencies between the user terminal to at least one satellite and in a downlink band of frequencies between the at least one satellite and the user terminal, comprising: a MSS (Mobile satellite Services) transceiver used for signal communication to send short messages from any stationary/ moving platforms to a stationary hub station through MSS transponder of a satellite,
2. The satellite-based communication system as in claim I, wherein uplink band is configured to operate in S X C links and downlink band is configured to operate in C X S links.
3. The satellite-based communication system as in claim 1, wherein the data is transmitted in S-band to the Satellite and then sends the data in C-Band to the ground based hub station.
4. The satellite-based communication system as in claim 1, wherein the transceiver comprises a built-in GPS receiver working in L-band frequency, where the coordinates of the mobile platform received from the GPS Satellites are stored in a memory, and transmitted in S-band to the Satellite, the transmitted data enables the user to continuously monitor the location of the mobile platform.
5. The satellite-based communication system as in claim 1, the MSS terminal is programmed to operate in Aloha mode, configured to send low-density messages, each having a unique ID code operating in S-band and transmitting messages at multiple bits per second (bps) speed.
6. The satellite-based communication system as in claim 1, the MSS terminal is programmed to operate in TDMA modes, configured to send low-density messages, having a unique ID code operating in S-band and transmitting messages at multiple bits per second (bps) speed.
7. The satellite-based communication system as in claim 1, the MSS transceiver system comprises an antenna unit and a Trans-receive electronic (TRE-P) unit; the TRE-P further comprises MSS transmit chain, MSS receiver chain and a Processor loaded with Tx-Rx client application for sending/receiving messages; serial communication (RS-

232) is used to send data to/from the MSS Circuits to the Processor, where the client application is configured to opens through remote desktop in MCDS of the aircraft.
8. The satellite-based communication system as in claim 1. wherein the MSS terminal is in shape of rectangular patch configured for transmitting and receiving S-band signals and also for receiving GPS position from the GPS satellites in L-band.
9. The satellite-based communication system as in claim 1, further comprising a processor connected to the two interfaces, one for message transmission and another for message reception; MSS Transmit-Receive Messaging Client application is ported on the processor board using File Transfer Protocol at the destination, the Trans mi t-Receive Messaging Client holds the packet in memory until all the packets in the message are received, and the message is reconstructed from these packets and are stored in a database.
10. In a satellite-based communications system wherein communications between a user terminal and a hub station occur using an uplink band of frequencies between the user terminal to at least one satellite and in a downlink band of frequencies between the at least one satellite and the user terminal, a method comprising steps of: a transceiver for transmitting and receiving data using a uplink and downlink band of frequencies.
11. The method of claim 10, wherein the uplink band is configured to operate in S X C links and the downlink band is configured to operate in C X S links.
12. The method of claim 10, wherein the data is transmitted in S-band to the Satellite and then sends the data in C-Band to the ground based hub station.
13. The method of claim 10, wherein the transceiver comprises a built-in GPS receiver working in L-band frequency, where the coordinates of the mobile platform received from the GPS Satellites are stored in the memory, and transmitted in S-band to the Satellite; the transmitted data enables the user to continuously monitor the location of the mobile platform.
14. The method of claim 10, the MSS terminal is programmable to operate in Aloha mode, configured for sending low-density messages, having a unique ID code operating in S-band and transmitting messages at multiple bits per second (bps) speed.

15. The method of claim 10, the MSS terminal is programmable to operate in TDMA mode, configured for sending low-density messages, having a unique ID code operating in S-band and transmitting messages at multiple bits per second (bps) speed.
16. The method of claim 10, the MSS transceiver system comprises an antenna unit and a Trans-receive electronic (TRE-P) unit; the TRE-P further comprises MSS transmit chain, MSS receiver chain and a Processor loaded with Tx-Rx client application for sending/receiving messages; Serial communication (RS-232) is used to send data to/from the MSS Circuits to the Processor, where the client application is configured to opens through remote desktop in MCDS of the aircraft.
17. The method of claim 10, the MSS terminal is preferably in shape of rectangular patch antennas configured for transmitting and receiving S-band signals and also for receiving GPS position from the GPS satellites in L-band.
18. The method of claim 10, further comprising a processor connected to the two interfaces, one for message transmission and another for message reception, MSS Transmit-Receive Messaging Client Application is ported on the processor board using File Transfer Protocol at the destination, the Transmit-Receive Messaging Client holds the packet in memory until all the packets in the message are received, and the message is reconstructed from these packets and are stored in a database.