SatCOM Lab Experiments ______________________________________________________________________________ Experiment 2 1 First Edition Revision level: 12/2018 By the staff of SpectraTronix © 57A, El-Tesseen St., 11835, New Cairo, Cairo, Egypt Internet: www.SpectraTronix.com E-mail: info@SpectraTronix.com Printed in Egypt All rights reserved @ 2017 The buyer shall receive a single right of use of this experiment which is non-exclusive, non-time-limited and limited geographically to use at the buyer’s site/location as follows. The buyer shall be entitled to use this work to train his/her audience at the buyer’s site/location and shall also be entitled to use parts of the copyright material as the basis for the production of his/her own training documentation for the training of his/her audience at the buyer’s site/location with acknowledgement of source and to make copies for this purpose. 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SpectraTronix disclaims any proprietary interest in trademarks and trade names other than its own. 2 ● Objective: - To establish an Audio-Video Satellite Link between Ground Station - Transmitter and Receiver through transponder station. ● Setup Required:● Ground Station – Transmitter & Receiver - o o o Vector Signal Modulator Module – address : 0x 23A Vector Signal Demodulator Module – address : 0x 444 PLL Module –address : 0x123 o Synchronization Module 3 o o ● USB Control Module Caps – 3 qty Transponder Station – Transmitter & Receiver o o o Vector Signal Modulator Module – address : 0x 23B Vector Signal Demodulator Module – address : 0x 446 PLL Module –address : 0x124 o Synchronization Module 4 o o o ● ● USB Control Module SOC2S : secondary controller module. Caps – 2 qty Windows machine preloaded with: o Application Softwares: SatCOM_VidStream_GUI_EXE_ext.exe for Ground Station and Transponder Transponder_GUI.exe for Transponder Station, you will find them located in the compressed folders “SatCOM Lab Experiments\Experiment 1\Applications\SatCOM_VidStream_GUI_EXE_ext.zip” and “SatCOM_SOC_EXE_ext.zip”, unzip the files then go inside the folders to find them. RF Front-end: o BeeWave Modules: ▪ BeeWave: ● Power Amplifier ● Bandpass Filters -2 qty ● Low Noise Amplifier 5 ▪ ▪ o Accessories: SMA to SMA long cables: Black ones, 8 qty. o Antennas (4 qty) SMA to SMA short cables: Blue ones, 8 qty. ● Brief Theory:In this experiment we will transmit video (and audio) through an RF link. the video is captured from a camera using VLC (a well known application for playing and streaming media), we will use VLC version 2.1.5 (you may use another version but this is the version that is verified to work smoothly without problems like compatibility issue). VLC will incode the captured video using MPEG-2 standard into TS container, TS stands for Transport Stream, the container used in digital media broadcasting like IPTV and DVB applications, audio is encoded with MPGA, an MPEG-1 Layer 3 compression, a lossy compression that maintains most of the original sound quality. The generated TS data streamed to C700 through a dedicated application which routes it to the ground station transmitter and also gets the acquired data from the GS receiver. This application manages the operations with the C700 system, including initialization of the GS, and routing the data to and from the GS. The next step is that the GS streaming application sends the received data bits to another VLC instance which in turn reverses the operation, it decodes the Transport Stream data and displays the video. The communication between GS application and VLC instances is done using open ports on the windows operating system running the experiment. 6 The RF link between ground station transmitter and receiver is a digitally modulated signal based on DBPSK (Differential Binary Phase Shift Keying) . Digital modulation: In modern communication systems data is sent in digital representation form i.e. bits, and this data bits are used to modulate an RF carrier properties, this modulation is then detected at the receiver and used to extract the information bits back, one of the most used properties that modulate is the carrier phase, in which data bits are represented by shifting the phase of the carrier, for example bit 1 is represented by shifting the carrier by 180 degrees while bit 0 is represented by not shifting the phase, this is called BPSK (Binary Phase Shift Keying) and is shown in the next figure. 7 What is used in our system is a special version of this modulation type called DBPSK (Differential Binary Phase Shift Keying), in this version we don’t send the data bits directly, we send the difference or the change between the current bit and the last or previous bit, meaning we actually send either “there is a change” or “no change” information, this can be achieved simply by passing our data bits into an XOR circuit as in the next figure. In the receiver this process is reversed by XOR the data again. Transponder Station: After signal is transmitted from the GS transmitter it passes to the transponder station which retransmits it back to the ground station, this transponder station emulates a satellite link, this station is operated through a separate application. RF front-ends: During transmission signal loses its strength due to attenuation specially if wireless transmission, this causes degradation to signal quality and decrease in SNR (Signal to Noise Ratio), to reduce this effect and maximize signal quality we increase the power of the transmitted and the received signals using amplifiers, also in wireless transmission signals share the same media so there is a possibility of signals interference, either intentionally by transmitting in the same band or unintentionally by e.g. non linearity of the RF components like amplifiers, this can happen either ways, meaning other systems can interfere on ours or we can also cause interference on other wireless systems, so using RF filters is very importance in both transmitting and receiving ends. So the systems include separate modules for these tasks, which are modular so they can be modified or upgraded to suit different needs e.g. changing the operating frequency of the filters to operate in a new 8 band, or adding more amplification stages to increase the transmission range, this subsystem is called BeeWave system. ● Block Diagram:The following figure demonstrates the building blocks of the Ground station, the figure contains only the blocks related to RF link functionality, it does not show the connection protocol to the PC for example. There are three main blocks that form our system: 1. VSM : which is the transmitter module, this block is realized by the VSM module colored green. In ground station this modules gets data bits from PC through the specified application and performs the modulation operation and transmits the created signal through its RF output port. 2. VSD : which is the receiver module, this block is realized by the VSD module colored orange. In ground station this modules receives the RF signal through its RF input port then demodules the signal to get and send the recovered bits to the application on PC. 3. PLL : which acts as the LO for the system, this block is realized by the PLL module colored red. Other modules are USB (blue) that is the communication bridge to the PC, and the SYNC module (yellow) which provides synchronization clock to the system, all modules are shown in the next figure. 9 For transponder station modules will serve for different functionality, the receiver (VSD) will acquire the RF signal and rout it to the transmitter (VSM), after applying some effects on the signal if required like delay or doppler. So the integration of the two system will be like this figure. ● Precaution:● Connections should be tight, screw the cables with your hand till they don’t go any more. 10 ● ● ● ● To save time, please make sure that Ground Station and Transponder respective modules and its chassis are already installed. During modules installation or removals power should be off. Switch off power supply after performing the experiments. Procedure:- ● ● Ground and Transponder Station Before proceeding for the experiment make sure that Ground Station and Transponder Station (GS & TS) fans and modules are connected as per below figure. Also the RF connections should be done the same way in the picture above: o Connect LO IN of VSM1e to RF OUT 1 of PLL1 (any output will do). o Similarly connect LO IN of VSD2e to RF OUT 2 of PLL1 (any output will do). o Connect GS-VSM1e RF output to BeeWave1 VGA6000 RF input. o Connect BeeWave1 VGA6000 RF out to BeeWave1 BPF1 input. o Connect BeeWave1 BPF1 output to TS-VSD2e RF input. o o o Connect TS-VSM1e RF output to BeWave2 LNA6000 RF input. Connect BeeWave2 LNA6000 RF out to BeeWave2 BPF2 input. Connect BeeWave2 BPF2 output to GS-VSD2e RF input. 11 ● If no then install GS and TS as mentioned figure. While connecting modules to chassis connector, make sure that module pins and mounting hole should be matched with the chassis, see the following figure ● If yes then connect Power adaptor cable to the power connector available on the rear right side of the chassis of both stations (GS and TS), as in this figure. ● Before Power-on make sure that programming/experiment switch (black) available on the right side of the chassis (on both GS & TS) is in release position. As in the previous figure. Connect USB cable between USB Mini-B connector of USB module and the USB port of Laptop/PC, do this for GS and TS. Now you are ready with the setup. For each station power-on the setup, meaning connect the AC/DC power adaptor to the AC power source and to the DC power input socket on the rear side of the C700 chassis, doing so you will see the red LED of the C700-USB Module will ● ● 12 be turned on. ● ● ● Start VLC program and configure it as a Video-Audio streaming source (TX) as mentioned in the document “Configuring VLC”. Open another VLC program to work as a Video-Audio streaming receiver (Rx) as mentioned in the document “Configuring VLC”. Open (double-click) the application C700_streaming.exe and wait till it is fully loaded, it will show the following widow. A brief description of the GUI sections is depicted below: ➔ Source: Source streaming configuration ◆ VLC1 port: the port on which the Tx VLC will send the stream for transmission, you may put it anything, just make sure this port is not used by any other program (if you are not sure you can consult your IT department) typically 1234 is OK. ◆ Status: Number of bits sent. ➔ Destination: ◆ Destination IP: 127.0.0.1 to stream to same PC. 13 ◆ Destination port: the port on which the Rx VLC will get the received stream, you may put it anything, just make sure this port is not used by any other program (if you are not sure you can consult your IT department) typically 1235 is OK. ◆ Status: Number of bits received. ➔ C700: Set the USB port number and the center frequency. ◆ Bypass ; check this to stream form Tx port to Rx port directly, without passing to/from RF link (C700), this is mainly for testing and debugging purposes. ● ● Continuing back to the steps, configure each UI control as per mentioned in the GUI description above, click “start”, the ON/OFF indicator should turn to ON and its color should be red. You will notice that the Tx state bit counter is only counting, and video is playing inly in transmitter VLC, that is because receiver does not receive anything for now as the transponder is not running yet. Open (double-click) the application Transpoder_GUI.exe and wait till it is fully loaded, it will show the following widow. A brief description of the GUI sections is depicted below: ➔ Execution buttons: to run and stop the TS. ◆ C700 port: the C700 port, so the application can address the right system. ◆ Run and stop: to run and stop the transponder. ◆ Reset: to reset the transponder state as if it is just opened. 14 ➔ Path: to set the delay of the path between transponder and ground station. ➔ Center frequency: the RF center frequency in MHz. ➔ Path configuration: ◆ Configure path: to apply the changes made in this panel. ◆ Calibrate: This calibrates the output level after applying the effect to avoid internal overflow in the digital domain of the system, if input is too high it will cause overflow even if its power level is within limits of the input module (VSD, which is +10 dBm). ◆ Effect: this chooses what effect to apply, doppler or phase. In case of doppler then the value of doppler shift can be entered in the text box on the right side. ● ● Above it there is a drop-down list above it to choose the unit of dopple, you can choose between , speed (m/s, or Km/hour) or just frequency. ◆ Digital gain: this is the gain value that the button “calibrate” set, you can manually change it here, to increase gain, you have to know what you are doing or overflow will occur. Continuing back to the steps, press “Set paths”, to set and configure TS path. The first time you press this button after opening the application it will take longer to initialize before configuring the station. After it finishes, press “Calibrate”, this will take two seconds, during which you will notice the green LEDs of VSD and SOC modules are on, also VSM lower green LED will be on, as in the 15 next figure. ● ● After calibration is done, press run, you will notice the five LEDs on the three modules are on again like we mentioned in calibration state, also receiver state counter will start to count and video will start to play on the receiver VLC. Results:- As we can see in the picture above, the video appears in the streamer VLC (left), and also appears on the receiver VLC (right), you will notice that there is some delay between Tx and Rx video (in order of 3 second) this is cause by the VLC running the algorithm for video compression to and from TS (MPEG-2 + MPGA). As mentioned in the document “Configuring VLC”. in the middle is the our application with handles the Tx Rx operation with the C700, it shows the number of bits transmitted and received, they are nearly the same (Rx may appear less that Tx). If you press stop in the transponder application, receiver video and counter will stop. 16 ● Conclusion:We managed to perform a successful Video/audio transmit and receive through the RF transponder station. Part 2 : Connection using antennas ● Procedure:● Press “stop” in the TS application. a) Ground Station Connect GS-VSM RF out via long cable to BeeWave1-VGA. Connect BeeWave1-VGA RF out via short cable to BeeWave1-BPF1. Connect BeeWave1-BPF1 RF out via short cable to Antenna1. Connect Antenna2 via long cable to BeeWave1-BPF2. Connect BeeWave1-BPF2 RF out via short cable to BeeWave1-LNA. Connect BeeWave1-LNA RF out via short cable to GS-VSD RF input. b) Transponder Station ● Connect TS-VSM RF out via long cable to BeeWave2-VGA. ● Connect BeeWave2-VGA RF out via short cable to BeeWave2-BPF1. ● Connect BeeWave2-BPF1 RF out via short cable to Antenna3. ● Connect Antenna4 via long cable to BeeWave2-BPF2. ● Connect BeeWave2-BPF2 RF out via short cable to BeeWave2-LNA. ● Connect BeeWave2-LNA RF out via short cable to TS-VSD RF input. SO connection will be : ➔ GS-VSM >long> BW1-VGA> short > BW1-BPF1 > long > ant1 ➔ GS-VSD <long< BW1-LNA <short < BW1-BPF2 < long < ant2 ➔ TS-VSM >long> BW1-VGA >short> BW2-BPF3 > long > ant3 ➔ TS-VSD <long< BW1-LNA <short< BW2-BPF4 < long < ant4 ● ● ● ● ● ● ● ● ● ● Press “Run” on TS application. Check the “Tx Rx frequency separation” checkbox, then click “Configure paths”. In C700 Video streaming application click “stop”. Check the “Frequency Division Duplex” checkbox. 17 ● Click “Run”. ● Results:You will notice the same behavior and results we got in part one of the experiment, here since we use antennas the Tx and Tx of both stations can interfere on each other so we have to separate the frequencies of the two links (GS -> TS and TS -> GS), tht what we did by checking frequency separation boxes in the GUIs. ● Conclusion:We successfully performed a Video/audio transmission and reception through the RF transponder station via a wireless channel.