DESIGN GALLERY
DESIGN GALLERY
INTERFERENCE CALCULATION AND RF RADIO-MAPPING
Cognitive Radio systems are designed capable of sensing spectrum availability and sharing spectrum with legacy wireless systems. Knowledge and good characterization of the RF environment and Interference are crucial for network studies of such spectrum sharing radios and Spectrum Utilization Efficiency (SUE). NEBENS is developing a software tool, RadMap, which calculates the Interference at various propagation environments given a distribution of transmitters.
The Waterfall diagram (spectogram) at a specific observation point. The interference is caused by a distribution of WiFi Access Points (AP's) as shown by the stars in the contour figure of the right.
The contour plot of the Interference power spectral density over a 400m x 500m area due to a distribution of WiFi Access Points (indicated by the stars).
ANTENNA ANALYSIS AT THE THROUGHPUT LEVEL
Antenna design is investigated through analyses of the resultant throughput and its statistics. The intermediate performance metrics of antenna gain, impedance, bandwidth, efficiency, etc. are indicative of performance, but remain "intermediate" metrics.
The Cumulative Distribution Function (CDF) of a crossed dipole antenna system under various average SNR circumstances in a WiMAX 2x2 system operating in a TGn-B like propagation environment.
The Cumulative Distribution Function (CDF) of various antenna designs of a WiMAX 2x2 system operating in a TGn-B like propagation environment and at an average SNR of 25 dB.
RF PLANNING AND SYSTEM ANALYSIS
Frequency reuse patterns are investigated and their performance is assessed through analyses of the resultant throughput, cell size, etc.
A 4-2-2 frequency reuse pattern. The base station at the origin transmits at frequency F2 and its signals are interfered by the signals of the same frequency from all the surrounding base stations. The Signal to Interference plus Noise Ratio (SINR) is calculated for all the points in the 90o sector.
The SINR results from the previous analysis are used with link simulations to determine the Throughput Rate for all the locations in the sector. Furthermore, statistics of the throughput are obtained by analyzing its values at all the points in the cell.
ANTENNA DESIGN AND PLACEMENT FOR VEHICULAR APPLICATIONS
Installed antenna performance on large platforms is a challenging problem due to the electrical size of the resultant problem. Additionally, while one could get by with simplistic analysis approaches for single antenna systems, such luxury is not afforded when Multiple Input Multiple Output (MIMO) antenna systems are employed, or when several different communication systems coexist on the same platform. In a strong partnership with professor Jin-Fa Lee of the Ohio State University (OSU) a "Domain Decomposition" approach employing a number of different solvers (i.e. solvers based on different numerical methods) has been used to solve the problem of installed antenna performance.
A typical Humvee
The antenna module installed on the Humvee
The domains into which the problem is decomposed for analysis using a hybrid approach of several computational methods.
ANTENNA PLACED AT THE ROOF OF THE HUMVEE PLATFORM
The currents on the surface of the Humvee. Note that the tires have been modeled as lossy dielectrics.
Details of the current on and near the antenna (albeit at a different scale from that depicted on the figure at the left). Also shown is the pattern of the isolated antenna (blue smooth curve) and the effect of the Humvee platform (red curve).
ANTENNA PLACED AT THE FRONT OF THE HUMVEE PLATFORM
The currents on the surface of the Humvee. Again, the tires have been modeled as lossy dielectrics. Notice the interference pattern on the hood caused by the reflections from the windshield and the edges of the Humvee. Contrast this with the smoother current distribution in the previous case where the antenna was placed in the middle of the Humvee roof.
Details of the current on and near the antenna (again at a different scale from that depicted on the figure at the left). Also shown is the pattern of the isolated antenna (blue smooth curve) and the effect of the Humvee platform (red curve). Notice the "null" created at the back of the Humvee due to the shadowing effect of the windshield in this antenna position.
IEEE 802.11n Set-Top Box
This set-top box was originally designed with high gain external dipole antennas. Cost and mechanical reliability were concerns. Using the techniques described in the NEBENS cross-layer design page the product was redesigned with internal antennas that performed slightly better in the indoor environments of interest. The three antenna module is shown on the green PCB at the detail of the picture to the right. Cost, reliability and aesthetics were significantly improved.
TRI-BAND ACCESS POINT FOR MESH NETWORKS
The product to the left of the figure is the traditional "stick" version with multiple external dipole antennas to accommodate three bands and achieve diversity. The product to the right, "integrated" has been optimized for performance in urban environments and size, not to mention cost, using the Cross Layer Design methodology. Arrays of internal, printed antennas have been used to achieve at least equal performance to that of the traditional design in a much smaller, cheaper and higher reliability product.
HIGH GAIN PLANAR ARRAY (ETSI SS2)
The layout
The simulated results
The measured results (elevation pattern)
Simulated and measured radiation patterns of the array.
Modeling and simulation work is always done before prototyping. This is an inexpensive design of a planar dipole antenna array and its feed network (single SMA connector at the center of the board) to meet the ETSI SS2 pattern specification.
WIRELESS ADAPTER FOR GAMEBOY
The final product in the market
Extensive modeling and simulation work is undertaken before prototyping. Many aspects of the design are considered and engineering trade-offs are assessed in terms of performance and cost for optimum impact
This work was performed at Motorola (Freescale) for Nintendo.