GPS Receiver

1.Dual Frequency GPS Receiver

A dual frequency (L1 centred at 1575.42 MHz and L2 centred at 1227.6MHz) GPS receiver make GSV4004B GPS receiver is operational at Gadanki. This receiver is scintillation and TEC monitoring device housed with a low phase noise stable Ovenized Crystal Oscillator (OCXO), and provides true amplitude, single frequency (on L1) carrier phase measurements and TEC measurements from up to 11 GPS satellites in view. It also tracks one SBAS (GAGAN or WAAS) satellite, providing L1 measurements and Scintillation data (but no TEC data). A GSV made chock ring antenna has been installed on roof top with a height adjustable mast to obtain multipath-free signal above 5-7 degree elevation angles that provides Signal-to-Noise density (C/No) levels above about 36 dB-Hz. A 30 meter low loss RF cable (50 ohm) connects the receiver that is rack mounted and connected to a PC via serial port. The receiver records the amplitude scintillation index (S4) per minute at minute and phase scintillationindices (Sigma-Phi) computed over periods of 1, 3, 10, 30, 60 seconds averaged over one minute. The receiver employs 22 hardware channels to track up to 11 GPS satellites and two channels are reserved for SBAS. Phase data and amplitude data are sampled at a 50 Hz rate and can be recorded at any desired rate below this. A Script based data logging has been provided that can be customized by user to control various data logs.

2. Multi-frequency multi-GNSS receiver PolaRxS-PRO of Septentrio make is a multi-frequency and multi-constellation capable GNSS receiver. This receiver provides 136 hardware channels for simultaneoustracking of all visible satellites in GPS, GLONASS and GALILEO constellations besides tracking some of the SBAS satellites in L1/L2/L5/E5abAltBoc range of signals. The receiver is housed with a low phase noise OCXO and on-board multi-frequency tracking engine that provides high accuracy phase measurements for all signals.An intuitive Graphical User Interface is available for data logging and remote control. Specifically for Space Weather and ionosphere monitoring applications, the logging tool is extended for continuous TEC and scintillation indices (ISMR) logging and monitoring. Available ISMR indices include the S4, Sigma-Phi, spectral slope and SI indexes for all satellite constellations and frequency bands. The receiver can be communicated via Serial, USB and Ethernet connections and also provides PPS clock output to synchronize devices with GPS time. On board data logging capacity of 2 GB enhances the field application of the receiver.

3. Software GNSS Receiver A software defined GNSS receiver (IFEN make SX-NSR model) takes the state of the art facility of this laboratory to a new level wherein understanding the futuristic developments in the GNSS research and development arena are at core. The software defined radio receivers are a new class of receivers utilizing the high computation power of new generation CPUs. The multi-core CPU has been used to define real-time software channels when simultaneously tracking all current civil signals of GPS, Galileo, GLONASS, BeiDou and SBAS (GAGAN) systems (using 8 IF input streams at a sample rate of 20 MHz each). Further, adaptable configurations are possible to employ enabling real-time full featured reference station mode on a PC. The data recorder functionality to store data files for later post-processing, entire configurability provided within the graphical user interface (including online configuration parameter description within GUI), live configurability for dedicated parameters as DLL, FLL and PLL bandwidths, dedicated widgets for PVT solution, RF-spectrum, multi-correlator output, GNSS channel output, acquisition output and several other features make this receiver as one of the best tool to study the impact of ionosphere/atmosphere on navigation signal and also to develop strategic support for future corrective measures like the ones during Post Sunset Scintillations and the signal fading etc. The Scintillation index studies with high rate data can be done with pre-recorded IF data. User can develop N number of algorithm and test them in real-time as well as in replay mode for hypothesis testing and finalizing the ideas. Also the multi-path and interference rejection can be achieved in active mode making this as state-of the art instrument.