Abstract During the last decade, the wireless communications industry has grown rapidly. Driven by market demand, service providers are continuously looking for better systems.
An FPGA platform for demonstrating embedded vision systems
The main focus of continued research has been to increase the quality of services and system capacity. A great deal of research has been conducted to develop receiver structures useful for CDMA systems. Traditional receivers such as the correlation and RAKE receivers are vulnerable to the near-far problem, i.
This problem is common in mobile environments.
If the calibration is poor, then the beam will become incoherent and nulls will be shallow. These values indicate the beamformers' statistically estimated confidence in the phase calibration, and tend to be overestimators of the phase error. In most cases, Beamformer number 1 obtained a mean confidence within two degrees of phase. Beamformer number 2 was somewhat worse at about five to ten degrees of phase.
It is noteworthy that these calibrations used the same antennas and were performed nearly concurrently and it is expected that the two beamformers should obtain calibrations at the same level of accuracy. Differences may arise from slightly different DDC designs used by the two beamformers. The impact of these differing designs has not been fully evaluated, but it is known that they can affect the calculated confidence level without necessarily worsening the actual calibration.
A summary of the expected phase errors from various systems is shown in Table 3. However, phase errors such as those from the fine delay filter are deterministic and periodic with time as the array is scanned, and may have a greater impact on the sensitivity of the resulting beam by amplitude modulating the array pattern. Most of the challenges encountered in the design stem from the limited device resources in the FPGA, and the distributed nature of the instrument.
Calibration might also be improved by extending the calibration processing beyond the point source model, allowing the use of stronger, but spatially resolved, calibrators. This approach is planned for the next generation of instruments e. Parsons et al.
This research was funded by the National Science Foundation, awards and Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries other than missing content should be directed to the corresponding author for the article.
Volume 46 , Issue 1. If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account.
If the address matches an existing account you will receive an email with instructions to retrieve your username. Open access. Radio Science. Free Access. William C. Barott E-mail address: barottw erau. Tools Request permission Export citation Add to favorites Track citation. Share Give access Share full text access.
Real‐time beamforming using high‐speed FPGAs at the Allen Telescope Array
Share full text access. Please review our Terms and Conditions of Use and check box below to share full-text version of article. Figure 1 Open in figure viewer PowerPoint.
Antenna positions are marked. The rectangular region indicates the signal processing building, which houses the beamformers. Figure 2 Open in figure viewer PowerPoint. Amplification stages have been removed for clarity.
- fpga correlation thesis.
- during pregnancy uterine decidua synthesises?
- dar american history essay contest.
- hilliard darby high school persuasive essay rubric.
- essay of my school in french?
Wideband Time Domain Beamforming 2. Mathematically, for any set of samples in time, the narrowband beamformer performs the calculation. Figure 3 Open in figure viewer PowerPoint. Linear array of antennas. The geometric delays indicated on the plot are unique to each antenna, and depend on the scanning angle.
Figure 4 Open in figure viewer PowerPoint.
fpga correlation thesis
Time Versus Frequency Domain: Computational Complexity  It is known that wideband beamforming can be applied in either the frequency domain by applying unique phase corrections to each channel , or in the time domain by combining a time delay with a phase shift [e. The approximate complexities are equal when neither beamformer is clearly more efficient, as in. Time Domain Beamforming  The time domain process for wideband beamforming, implemented at base band, consists of a time delay and a phase adjustment.
First, the time domain outputs from two antennas are defined as. Hardware Implementation 3. Figure 5 Open in figure viewer PowerPoint. Detailed view of a BEE2. The unit is sized for a standard 19" rack. Five FPGAs are distributed as shown. The center FPGA is used strictly for command and control. Data Flow  The three completed beamformers are shown in Figure 6. Figure 6 Open in figure viewer PowerPoint. Image of the ATA beamforming racks.
Due to space constraints, several images have been stitched together to create this picture. Beamformer number 1 is the leftmost rack. Beamformer number 2 is the middle rack.
The rightmost rack is for the DACs and Beamformer number 3. Figure 7 Open in figure viewer PowerPoint. The corporate beamforming architecture used in the ATA beamformers. Generally, the left 42 are x polarization inputs and the right 42 are y polarization inputs. The first tier applies beamforming corrections in leaf nodes.
fpga correlation thesis
The dashed boxes represent the implementation of these nodes within each BEE2. Figure 8 Open in figure viewer PowerPoint. View of the three beamformer firmware models, including the leaf node, branch node, and circular branch node. All beamforming corrections occur in the leaf node. Other nodes provide subbeam calibration and combination, as well as some enhanced output processing. Leaf Node Beamformer  With an understanding of the entire system now in mind, we continue to a detailed description of the beamformer processing architecture, beginning with the leaf node. Figure 9 Open in figure viewer PowerPoint.
The current ATA filters use a default bandwidth of 0. Figure 10 Open in figure viewer PowerPoint. Phase Corrections  Leaf node phase corrections are applied in a complex multiplier fed by a complex oscillator, as indicated in Figure 8a.