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TECHNICAL PROPOSAL Gil, this is what I have as of Monday at 5pm. This is generally a mess, I will have time tomorrow to finish it. Indoor Positioning Systems 1. Introduction We are developing a local positioning sytem (LPS) that is capable of operating indoors. The advent of Global Positioning Systems (GPS) has revolutionized navigation. However, the GPS network does not function inside most structures, i.e. office buildings, factories, etc. The reason is that GPS uses radio waves to operate. However, radio waves from GPS satellites, which are a form of electromagnetic radiation, do not propagate in very well inside a building. The main reason for this deficiency is that GPS signals are low power (-130dBm outside, sea level), and are so severely attenuated inside buildings that GPS receivers cannot detect them. Furthermore, even if the satellite’s carrier signal could be detected, the attenuation is so large that the GPS receiver could not lock onto the modulation due to prohibitively low signal to noise ratios. The main factors that contribute to the attenuation of EM inside buildings can be traced to the conducting and dielectric properties of building walls. If the GPS system could greatly increase the power output from their orbiting satellites, indoor positioning would be much more likely. However, there are two fundamental reasons why this is highly unlikely. One is that orbiting satellites can not output significant power without being quickly depleted. The second reason is that GPS operates with continuous wave (CW) propagation, and transmitting high power continuously could have harmful effects on people and the environment. We are developing technology that enables indoor positioning. The indoor positioning technology is based on a new method for positioning. Furthermore, the new technology is being developed with the aid of a unique CAD tool for electromagnetics. This new EM CAD tool, was developed by our design team, and is not available anywhere else. The LPS system will be able to transmit much more power to the receiver than the satellite system. In addition, instead of transmitting continuously with CW, we employ pulsed power with EM waves propagating for time scales that are on the order of nanoseconds. This pulsed technique obviates the need for the receiver to lock onto the modulation scheme of a transmitter. It also avoids the potential problem of harming people and the environment because the EM signal is only present for nanoseconds, and therefore transmits negligible total energy. To achieve this new LPS technology for indoor positioning, we are combining our expertise in three fields: Radio Frequency Very Large Scale Integration (RF VLSI) Electronics; Electromagnetics (EM); and Statistics. Our experience in RF VLSI facilitates the design and fabrication of the necessary microelectronics hardware. The team’s expertise in electromagnetics will enable the optimized design and fabrication of antennas specific to the LPS applications, as well as the enhancement of our new state of the art EM modeling code for predicting the propagation of RF signals inside structures. Finally, by drawing on our work on statistics, we are developing techniques that extract the correct location information based on an overly determined data set. The products we plan to bring to market include: A local distance determination system capable of indoor operation. A local absolute positioning system capable of indoor operation. Software for predicting the path of electromagnetic wave propagation with applications to positioning. Description of Proposed Solution 2.1 Local Positioning System: Underlying Theory Below we describe the basic operating principle of our LPS system. We start by explaining how we use electronics and RF to measure absolute distance. We then explain how we extend the principle to measure precise location. 2.1. Measuring Absolute Distance To measure absolute distance we use ultra-fast clocks along with the speed of light. Inexpensive ultra-fast clocks are now possible to build as a result of the microelectronic revolution. Complementary Metal Oxide Semiconductor (CMOS) Transistors are the basic building blocks of most modern integrated circuits (chips). Technology has moved so quickly that it is now possible to routinely build chips with millions of transistors that have critical dimensions of less than 0.2 microns. In addition to packing a large number of transistors on a chip, their small size allows these basic building blocks to operate on time scales of less than 0.1 nanosecond. It is now possible for even the small business to build chips using these state-of-the-art transistors. We design our circuit, and then contract out the fabrication to the manufacturer. (The manufacturer we use is the MOSIS facility, which specializes in small volumes.) This enables even a small business to develop products based on the most modern technology. We have used ultra-small transistors to build ultra-fast clocks. In fact, with such small devices we have designed, and had electronic clocks fabricated that operate so fast that we can use them to measure the speed of light. For example, we have designed electronic clocks that can measure times as small as 0.1 nanosecond. By knowing that the speed of light is 3 X 1010 cm/sec, we can use our clocks, in conjunction with electromagnetic wave propagation, to measure distances with a resolution of 3cm [(3 X 1010 cm/sec)(1 X 10 –10 sec )=3cm]. To understand how we measure distances using fast clocks and electromagnetic (EM) waves, consider the following. At location ‘A’ we have a transceiver that is capable of sending and receiving electromagnetic signals. Connected to the transceiver is a very high frequency clock that is operating at a known frequency of say 10GHz. At location ‘B’ we have another transceiver. To measure the distance between points A and B, the transceiver at point A sends an EM signal to B, at the same time the clock at A starts. After a finite amount of time, transceiver B receives the signal and transmits it back to A. When A receives the signal the number of periods on the clock is recorded, which is the time it has required for the EM wave to go to from A to B and back to A. By multiplying this time by the speed of light, we can determine the distance between A and B. Intrinsic delays due to the electronics response times for the electronics will be easily measured and calibrated. 2.2. Measuring Precise Location Suppose we want to measure the location of a point B. We achieve this by extending the above methodology by using two more transceivers. We place transceivers A1, A2 and A3 at three known locations. Each transceiver has its own clock. Using the algorithm discussed above, we can find the distance between point B and A1, A2, A3. By knowing the distance between B and the three positioned transceivers, a simple geometric relationship will give the precise location of point B relative to A1, A2 or A3. (This is analogous to the GPS triangulation methodology.) 3. Core Hardware Design The LPS system will be composed base stations and personal LPS devices. The base stations will be mobile, but their positions will remain fixed once they are put into service for a specific LPS event. The personal LPS devices are mobile and worn by safety workers (firemen, or any other individual that we want to track). The personal LPS device is mainly a transceiver. The base station consists of a transceiver, a GHz clock, a counter, and digital logic for converting counts to distance. (Of course there is additional circuitry identifying individual personnel. This is described below.) The personal LPS transceiver consists of a low noise input amplifier that is tuned to a specific very narrow band frequency range. The output signal is generated by voltage controlled oscillator that is mixed with a square wave of very low duty cycle. The resulting output will be an amplitude shift key modulated (ASK) carrier wave (pulsed sinusoidal) which is then fed into an RF amplifier to achieve power levels on the order of several watts. The output of the amplifier will then be impedance matched to drive the output antenna. The LPS system components include contain transceivers, counters and antennas as their basic components. We will develop two different designs. The first system we develop will use already existing integrated circuits. A second system, using on our own chips that are tailored specifically for the LPS system, will subsequently be developed. By developing our own IC’s we will optimize We will first design these transceiver chips, and then have them fabricated using the MOSIS chip fabrication facility. Our transceivers will be designed and fabricated using CMOS technology. The transceivers will consist of a receiver and a transmitter. The transmitter will use an generated with a frequency synthesizer that is based on a phase-locked loop. The transmitter output will be a tuned, common source-type power amp matched to a 50ohm patch antenna. We will operate at several frequencies. These frequencies will be in the ISM bands and are likely to include 433MHz, 900MHz, and 2.47GHz. (Below we describe that our prototype operates at 433MHz.) The advantage of using high frequencies is that it allows use of passive components that are small, and thus pocket size transceivers. This frequency is accessible using inexpensive CMOS components from a 0.25micron feature length process, available through MOSIS. The basic design of our transceivers is illustrated in Fig. 1, which is a layout of an FSK transmitter chip that we already have had fabricated using MOSIS. The receiver section will also be based on the phase-locked loop (PLL) topology. The input stage will consist of a low noise tuned amplifier, which feeds the PLL. The PLL will drive a voltage-controlled oscillator that will be used to demodulate the FSK signal. The high speed clock, used to calculate the time required for signals to travel, will be a will be a three stage ring oscillator that inputs an asynchronous counter. The clock frequency will be approximately 10GHz in our prototype. Into the chip will also be designed the digital circuit that will convert the clock values into distances and location. The circuits will be designed with the aid of the circuit simulator SPICE, and laid-out using the Cadence IC development software. We have recently designed several test chips using MOSIS to establish design parameters and fabricated several of our circuit building blocks, including PLLs, clocks and counters[1-3]. We are developing a lower frequency prototype of this system using off-the-shelf components. Schematics and circuit board layouts for this system are shown in Figures 2 and 3. 2.4. CAD with State-of-the-Art Electromagnetic Modeling To help determine the frequency, polarization, and power level of the EM signals, along with base station location and propagation within walled structures we have developed a state of the art electromagnetic wave propagation computer aided design tool (CAD). Our novel CAD tool predicts the velocity and power of an electromagnetic RF pulse as it propagates from a base station to the receiver and back. In addition, the CAD tool can tell us if there is any deviation from the straight line path of propagation. Accurate modeling of modern signal propagation inside structures usually requires a fullwave solution to Maxwell’s equations. However, such a solution is difficult because our system uses EM waves of very short duration. Therefore, frequency domain analyses are not appropriate for our applications, so we must rely on time-domain numerical solutions to Maxwell’s equations. However, Maxwell equation Finite-Difference-Time-Domain (FDTD) conventional solvers employ methods are limited by the Courant condition. This restriction requires very small time steps, and therefore prohibitively long simulation times are required to analyze the details of EM propagation inside buildings. To overcome this problem, we have developed a new state-of-the-art simulator that uses the Alternating-Direction-Implicit (ADI) method [1, 2]. In this new FDTD-ADI method. Maxwell’s equations are discretized with the electric and magnetic fields on different grids [1, 2]. By manipulating Maxwell’s equations, we transform the differential equations to a system of tri-diagonal algebraic equations. Each matrix of the system corresponds to one specific dimension [1, 2]. We then solve the tri-diagonal systems at each time step for the EM fields in 3D. We have developed this software over the past two years. The software is extremely well suited to model the electromagnetic wave propagation for our location system because it efficiently operates in the time domain. We have already presented its capabilities at two different conferences, where it was very well received[REF]. to calculate distances, we will power levels necessary in order to send signals into buildings we Measuring distance and location out of doors has less chance of being complicated by multi-path possibilities. However, inside structures multi-path propagation of EM waves is likely to occur. In any case, the methodologies we describe below for discerning the direct path can be applied to internal as well as external environments. To account for multi-path propagation we will combine our expertise in VLSI circuit design with our recent work in modeling electromagnetic wave propagation. By understanding the details of EM wave propagation, we expect to be able to predict the path of the EM wave between the various location transceivers. To achieve this we will model the propagation of EM waves between transceivers in edifices composed of standard building materials and designs. Modeling the propagation of EM waves is achieved by solving Maxwell’s equations, which are the fundamental mathematical equations that describe electromagnetism. Maxwell’s equations are a system of four 3dimensional, time-dependent partial differential equations. The solution of these equations describes the characteristics of electric and magnetic fields. These equations are very complicated, and thus especially difficult to solve. In fact, before the advent of powerful computers, solutions of these equations were only obtained for the simplest cases. We have recently developed a new numerical method for solving these equations for investigating EM effects in computer chips[4]. We plan to extend this method to modeling EM wave propagation that occurs between transceivers both inside and outside buildings. The new method employs the alternating direction implicit (ADI) technique. This technique has the advantage of being able to resolve both large and small objects simultaneously. This will enable us to simulate the propagation of EM waves between positioning transceivers, and therefore help determine the path our EM waves are taking. Once we have adapted our computer chip field solvers for modeling electric fields inside structures, we plan to simulate wave propagation inside typical buildings to calibrate the simulator, as well as determine the optimal locations for our stationary transceivers. Antenna Design Type of antenna for base station: Major considerations: 1. Directivity. Since the base station is intended to be mobile, good efficiency can be achieved by using directional antennas that span half-space. 2. Polarization. Circular or Elliptic polarized field has advantages over linearly polarized field in that it can penetrate through fog, moisture, or other gases that are potentially present in the fire scene. 3. Profile: Wire vs. Surface patches. Microstrip patch antennas, which come in a wide variety of shape are ideal for such application because of their low profile, cost effectiveness, and ease of manufacturing. Wire antennas, on the other hand, have an en extended profile that allows for increased efficiency but at the cost of volume. Microstrip antennas will be the first choice. Increasing the efficiency of these antennas can be made possible by increasing thickness of the substrate and using low-loss material. 4. Miniaturization. Microstrip patch antennas are most efficient and effective when they are constructed on a ground plane which is ideal, i.e., extends to infinity. Because of the portability of the base station (small size), we intend to use the novel concept of high-impedance surface (HIS) to produce an effective ground plane that significantly diminishes reflections from the edges of a finite (small) ground plane. The HIS also improves the efficiency of the antenna and the matching potential as it eliminates the ripples in the input impedance. The personal antenna, which will be placed on the protective suite of the fireman (or his protective helmet), needs to be an isotropic radiator, with equal efficiency in all directions. Several options will be considered such as a fat monopole to maximize efficiency. Patch antennas can be considered as an option. Initially, we intend to use offthe-shelf antennas. However, in-house design of such antennas is inevitable, as such antennas need to be mechanically and thermally robust while not sacrificing electrical (radiated) performance). We intended to investigate the effect of coatings on the antenna performance. Antenna testing will be carried out in an anechoic chamber with sufficient absorption range over the frequency band of interest. The antennas will be characterized using a vector network analyzer, and the radiation patterns can be calculated using a spectrum analyzer. Several test antennas covering the frequency range 30MHz to 5GHz are available for pattern measurements. Statistics Possible Alternative Approaches (For MIPS only, response to reviewer) We have also explored alternative approaches to locate lost safety workers inside buildings. Our background investigation and market analysis indicate that there are two possible approaches which may compete with, but are more likely to complement, with our own method. The first is an audio alarm. A downed fireman my activate an audio alarm that can lead other safety personnel to the general location. Of course this approach has applications. However, in the chaotic atmosphere of a conflagration such an alarm may not be discernable. In addition, the alarm itself does not provide the identity of the victim. In addition, the victim may have been incapacitated, and be unable to activate the alarm. Finally, there may be situations where you do not want everyone to know the location of the downed personnel, so sounding an audio alarm would not be appropriate under such circumstances. In any case, this approach is fairly simple so it could be easily added to complement our own LPS design. The other possible approach is to use a GPS receiver that is so sensitive that it is able to function indoors. Motorola Corporation has announced that it plans to bring a new GPS receiver IC to the market. the MG4000. The company claims that the sensitivity of the new MG4000 chip will be as much at -153dBm. The outdoor power of the GPS satellite signal when is reaches the earth is approximately -130dBm. The signal is reduced by another 20dBm once it enters a single story building, and attenuates another 10dBm for each additional building level[REF Saunders]. The conclusion from this information is that this nascent Motorola chip should be able to operate in small (one and perhaps two story structures). We therefore plan to use this chip to complement our proposed system. We will build a system where the person (or object) whose position we want to detect, wears a circuit that contains the single chip GPS receiver. On the board will also be a transmitter that takes this digital word output of the GPS receiver, and inputs it into a transmitter. The location of the transmitter will then be sent to a base station receiver. To develop this technology we will use transceiver multi-chip modules produced by Linx Corporation. These modules are available in 20 pin dual in-line packages, and are capable of transmitting digital words of up to 10 bits. We have already prototyped transmitterreceiver systems based on the Linx module. The major limitation of the Linx module is that it operates at a frequency of 433MHz. While this frequency seems relatively large, it is often not sufficiently high to provide pocket size transceivers for all applications. After prototyping the system with the Linx transmitter module, we plan to raise the operating frequencies using our own transceiver systems based on the PLL-FSK technology we described above. Z. Dilli, and N. Goldsman, MOSIS Design number 65046; Design name: ringosc05; Technology: SCN3ME\_SUBM, lambda = 0.3; (An oscillator-counter chip test chip) 2002. Z. Dilli and N. Goldsman, MOSIS Design number 64639; Design name: diginterf;Technology: SCNA, lambda = 0.8; (An oscillator-counter test chip) 2002. Y. Bai and N. Goldsman, MOSIS Design number: 65008; Design name: FSK; Technology: SCN3ME\_SUBM, lambda = 0.3; (An FSK transmitter test chip) 2002. X. Shao, N. Goldsman, O. Ramahi, P. N. Guzdar, A New Method for Simulation of OnChip Interconnects and Substrate Currents with 3D Alternating-Direction-Implicit (ADI) Maxwell Equation Solver. To be published in 2003 International Conference on Simulation of Semiconductor Processes and Devices. Fig. 1: Layout of microchip FSK transmitter we have designed and developed when we reach the stage of prototyping the location position system using our own integrated circuits. The actual dimensions of the chip are 2 X 2 mm2 Fig 2: Schematic and Printed Circuit Board layout of our prototype distance determination circuit. This circuit is to be worn by the person/object whose distance is to be determined. The actual dimensions are approximately 3 x 2 inches2. Fig. 3: Schematic and Printed Circuit Board layout of base station for determining distance. The actual dimensions are approximately 2 x 2 inches2.