FlCntNE/UeYwCG_QHrI/AAAAAAAAAo4/sZT2SYqR9QY/w1200-h630-p-k-no-nu/img7-17-2013-11.15.39+AM.jpg' alt='4 Bit Serial Multiplier Verilog Code' title='4 Bit Serial Multiplier Verilog Code' />Homemade GPS Receiver. Pictured above is the front end, first mixer and IF amplifier of an experimental GPS receiver. The leftmost SMA is connected to a commercial antenna with integral LNA and SAW filter. A synthesized first local oscillator drives the bottom SMA. Pin headers to the right are power input and IF output. The latter is connected to a Xilinx FPGA which not only performs DSP. N frequency synthesizer. More on this later. Spartan6 Family Overview DS160 v2. October 25, 2011 www. Product Specification 3 Spartan6 FPGA DevicePackage Combinations and Available IOs. I was motivated to design this receiver after reading the work 1. Matja Vidmar, S5. Produces analog and digital FPGAs, including the ORCA FPSC assets purchased from Agere formerly Lucent. PSoC 4 PSoC 4200 Family Datasheet Programmable SystemonChip PSoC Cypress Semiconductor Corporation 198 Champion Court San Jose, CA 951341709 408. MV, who developed a GPS receiver from scratch, using mainly discrete components, over 2. His use of DSP following a hard limiting IF and 1 bit ADC interested me. The receiver described here works on the same principle. International Journal of Engineering Research and Applications IJERA is an open access online peer reviewed international journal that publishes research. Using this site ARM Forums and knowledge articles Most popular knowledge articles Frequently asked questions How do I navigate the site ClaimBitcoin is the Bitcoin generator that everyone has been waiting for. Currently it is the only working Bitcoin generator out there, and at the moment it can. Its 1 bit ADC is the 6 pin IC near the pin headers, an LVDS output comparator. Hidden under noise but not obliterated in the bi level quantised mush that emerges are signals from every satellite in view. All GPS satellites transmit on the same frequency, 1. MHz, using direct sequence spread spectrum DSSS. The L1 carrier is spread over a 2 MHz bandwidth and its strength at the Earths surface is 1. Bm. Thermal noise power in the same bandwidth is 1. Bm, so a GPS signal at the receiving antenna is 2. B below the noise floor. That any of the signals present, superimposed one on another and buried in noise. I wrote a simulation to convince myself. GPS relies on the correlation properties of pseudo random sequences called Gold Codes to separate signals from noise and each other. VHDL/samples/bmul_ser.jpg' alt='4 Bit Serial Multiplier Verilog Code' title='4 Bit Serial Multiplier Verilog Code' />Every satellite transmits a unique sequence. All uncorrelated signals are noise, including those of other satellites and hard limiter quantisation errors. Mixing with the same code in the correct phase de spreads the wanted signal and further spreads everything else. Narrow band filtering then removes wideband noise without affecting the once again narrow wanted signal. Hard limiting 1 bit ADC degrades SNR by less than 3 d. B, a price worth paying to avoid hardware AGC. May 2. 01. 3 Update. This is now a truly portable, battery powered, 1. GPS receiver with turnkey software. The complete system below, left comprises 1. LCD display, Raspberry Pi Model A computer, two custom printed circuit boards, commercial patch antenna and Li Ion battery. Total system current consumption is 0. A for a battery life of 5 hours. The Raspberry Pi is powered through the ribbon cable linking its GPIO header to the Frac. FPGA board and requires no other connections. Currently, the Pi is running Raspbian Linux. A smaller distro would shorten time to first fix. After booting from SD Card, the GPS application software starts automatically. On exit, it provides a means to properly shutdown the Pi before powering off. Pi software development was done head less via SSH and FTP over a USB Wi Fi dongle. Source code and documentation can be found towards the bottom of this page. Both custom PCBs are simple 2 layer PTH boards with continuous ground planes on the bottom. Going clockwise around the Xilinx Spartan 3 on the Frac. FPGA board. from 1. VCO, power splitter and prescaler of the microwave frequency synthesizer. JTAG connector and, at 6 oclock, a pin header for the Raspberry Pi ribbon cable. Toyota Navigation Maps Download there. Far left is the LCD connector. Near left is a temperature compensated voltage controlled crystal oscillator TCVCXO providing a stable reference frequency, vital for GPS reception. The TCVCXO is good but not quite up to GPS standard when operating un boxed in windy locations. Blowing on it displaces the 1. MHz crystal oscillator by around 1 part in 1. Hz. which is magnified 1. PLL. This is enough to momentarily unlock the satellite tracking loops, if done suddenly. The device is also slightly sensitive to infra red e. TV remotes When first posted in 2. At least four are required to solve for user position and receiver clock bias but greater accuracy is possible with more. In that original version, four identical instances of the tracker module filled the FPGA. But most of the flops were only clocked once per millisecond. Now, a custom soft core CPU inside the FPGA serializes the processing. FPGA fabric is required for an 8 channel receiver or 6. Number of channels is a parameter in the source and could go higher. Positional accuracy is best when the antenna can see 3. Generally, the more satellites in view, the better. Two or more satellites on the same bearing can lead to what is termed bad geometry. The best fix so far was 1 metres at a very open location using 1. September 2. 01. 4 Update. The source code for this project has been re released under the GNU General Public License GPL. Processing is split between FPGA and Pi by complexity and urgency. The Pi handles math intensive heavy lifting at its own pace. The FPGA synthesizes the first local oscillator, services high priority events in real time and tracks satellites autonomously. The Pi controls the FPGA via an SPI interface. Conveniently, the same SPI is used to load the FPGA configuration bitstream and binary executable code for the embedded CPU. The FPGA can also be controlled via a Xilinx Platform USB JTAG cable from a Windows PC and auto detects which interface is in use. L1 frequencies are down converted to a 1st IF of 2. MHz by mixing with a 1. MHz local oscillator on the GPS3 front end board. All subsequent IF and baseband signal processing is done digitally in the FPGA. Two proportional integral PI controllers per satellite, track carrier and code phase. Download Anime Rosario To Vampire Sub Indo 3Gp'>Download Anime Rosario To Vampire Sub Indo 3Gp. NAV data transmitted by the satellites is collected in FPGA memory. This is uploaded to the Pi, which checks parity and extracts ephemerides from the bit stream. When all required orbital parameters are collected, a snapshot is taken of certain internal FPGA counters. Much of the 1. 55. MHz synthesizer is implemented in the FPGA. One might expect jitter problems, co hosting a phase detector with other logic, but it works. Synthesizer output spectral purity is excellent, even though the FPGA core is toggling away furiously and not all on harmonically related frequencies. This approach was taken because a board similar to Frac. Adding a front end was the shortest route to a prototype receiver. But that first version was not portable it had inconvenient power requirements and no on board frequency standard. Signal processing up to and including the hard limiter. The LMH7. 22. 0 comparator has a maximum input offset voltage of 9. V. Amplified thermal noise must comfortably exceed this to keep it toggling. Weak GPS signals only influence the comparator near zero crossingsThey are sampled by the noise To estimate noise level at the comparator input we tabulate gains, insertion losses and noise figures. LNASAWCoax. RFMixer. IFOverall system noise figure. Gain2. 8 1. 5 3. NF0. B. In band noise at the mixer output is 1. Bm or 5. 2V RMS. The mixer is resistively terminated in 5. The discrete IF strip has an overall voltage gain of 1. V RMS. The LMH7. 22. B of gain making a total of 1. B for the whole IF. Deploying so much gain at one frequency was a risk. To minimise it, balanced circuitry over a solid ground plane was used and screened twisted pair carries the output to the FPGA. The motivation was simplicity, avoiding a second conversion. In practice, the circuit is stable, so the gamble paid off. Active decoupler Q1 supplies 5. V for the remote LNA. MMIC amplifier U2 provides 2. B gain not at IF and ensures low overall system noise figure, even if long antenna cables are used.