MINOR PROJECT REPORT RECTENNA-(Rectifying Antenna) Submitted in partial fulfilment of the requirements for the award of degree of Bachelor of Technology in Electronics and Communication
Guide: Mr. S K Kundu
Submitted By: Stanley K Varkey (1331152808) Satya Deep Chatterjee (1371152808) Kunal Jain (1381152808) Richa Daga (2171152808)
BHARATI VIDYAPEETH’S COLLEGE OF ENGINEERING A-4, PASCHIM VIHAR, ROHTAK ROAD, NEW DELHI- 110063 AFFILIATED TO GURU GOBIND SINGH INDRAPRASTHA UNIVERSITY, DELHI-1100006 (2008-2012)
CERTIFICATE This is to certify that the minor project report titled “RECTENNA (Rectifying Antenna)” done by ‘Mr. STANLEY K VARKEY (1331152808)’ ,‘Mr. SATYA DEEP CHATTERJEE (1371152808)‘, ‘Mr. KUNAL JAIN (1381152808)’, ‘Ms. RICHA DAGA(2171152808)’ is an authentic work carried out by them at Bharati Vidyapeeth’s College of Engineering affiliated to GGSIP University, Dwarka, Sector-16, Delhi, under my guidance. The matter embodied in this project work has not been submitted earlier for the award of any other degree to the best of my knowledge and belief.
DATE: NOVEMBER 21st , 2011
Mr. S.K. Kundu Assistant Professor
ACKNOWLEDGEMENT We would like to articulate our profound gratitude and indebtedness to our project guide Mr. S.K. Kundu, who has always been a constant motivation and guiding factor throughout the project time in and out as well. It has been a great pleasure for us to get an opportunity to work under him and complete the project successfully. We wish to extend our sincere thanks to Prof. Anuradha Basu, Head of Department, for approving our project work with great interest. An undertaking of this nature could never have been attempted with our reference to and inspiration from the works of others whose details are mentioned in references section. We acknowledge our indebtedness to all of them.
Satya Deep Chatterjee (1371152808)
Richa Daga (2171152808)
Kunal Jain (1381152808)
Stanley K Varkey (1331152808)
ABSTRACT The work focuses on designing, measuring and testing an antenna and rectifier circuit (RECTENNA) optimized for incoming signals of low power density. The rectenna is used to harvest electric energy from the RF signals that have been radiated by communication and broadcasting systems at ISM band centred in 2.4 GHz., This work contains methods to simulate rectennas with Harmonic Balance and electromagnetic full-wave Momentum by Agilent Advanced Design Software. An RF energy harvesting device consists of three primary subsystems. 1. The Receiving Antenna 2. Low Pass Filter circuit 3. The rectification circuitry Motivation: The work is motivated by two types of applications: 1. Powering of low-power sensor 2. RF energy recycling being aware of the energy consumption and effect to the natural environment. Goal: The goal of this work is to determine the usefulness of low-power rectification.
INDEX ABSTRACT Chapter 1: INTRODUCTION
1
1.1
History: Previous Power Transfer Technologies
2
1.2
Recent Technologies of Rectenna
2
1.3
General Block Diagram
3
1.4
Application in the ISM band (2.4-2.5 GHz)
4
Chapter 2: RECTENNA DESIGN
5
2.1 Brief Background on Simulation tools used
5
2.1.1 Harmonic Balance Simulation 2.1.2 Momentum Simulation 2.1.3 LineCalc Tool
5 6 6
Chapter 3: ANTENNA
7
3.1 Brief Introduction 3.2 Some Important Performance Parameters
7 8
3.2.1 Antenna Efficiency 3.2.2 VSWR 3.2.3 Bandwidth
3.3 FEED TECHNIQUES 3.3.1 MICROSTRIP LINE FEED
8 8 8
9 9
3.4 Formulas Used in the Design of Patch Antenna 3.5 Design a rectangular patch
10 11
Chapter 4: LOW PASS FILTER
13
4.1 MICROWAVE FILTERS
13
4.1.1 Distributed Element Filter 4.1.2 RICHARD’S TRANSFORMATION 4.1.3 KURODA’S IDENTITIES
13 14 15
Chapter 5: RECTIFIER
17
5.1 Rectifying Circuit
17
Chapter 6: Simulation Results
19
6.1 Microstrip Patch Antenna
19
6.1.1 Patch Antenna 3-D Geometry 6.1.2 Simulation Results
19 19
6.2 Rectifying Circuit 6.2.1 Circuit Diagram 6.2.2 Input v/s Output Graphs
22 22 22
Conclusion
23
REFERENCES
24
Chapter 1: INTRODUCTION Power, when talking about wireless communications, is a feature that is really important to take into account because of the influence it has on the autonomy, weight and size of portable devices. Therefore, energy harvesting techniques have been proposed to try to give solution to this problem: we can have a variety of alternative energy sources that are less harmful to the environment. This kind of environmental friendly energy sources include energy harvesting from rectennas, passive human power, wind energy and solar power. Power we can extract from those techniques is limited by regulations and free-space path loss. As a general idea, small dimensions are a basic feature of portable devices, so the rectenna should be the same way.[17] Small sizes result in the received power to be low. As a conclusion, we can say that wireless power transfer is better suitable for low-power applications, e.g., a low-power wireless sensor. The way technology advance every year allow the decrease of certain characteristics in digital systems, like size and power consumption, that will lead to the gain of new ways of computing and use of electronics, as an example we have wearable devices and wireless sensor networks. Currently, these devices are powered by batteries, however, they present many disadvantages such as: the need to either replace them or recharge them periodically and their big size and weight compared to high technology electronics. A solution proposed to this problem was stated before: to extract (harvest) energy from the environment to either recharge a battery, or even to directly power the electronic device. [2] Harvesting wireless power techniques are mostly based on radio-frequency identification, or RFID. Basically, the transmission part sends RF signals that carries information to a chip to convert it to DC electricity to power the application. Then, a tag composed by an antenna and a microchip responds by sending back data about the object it is attached to. In order to be able to transfer power wirelessly an efficient rectenna is needed. Therefore, we present a rectenna design modelled with numerical analysis and harmonic balance simulation. This provides a good insight in the effect of the several parameters on the performance of the rectenna.
1.1 History: Previous Power Transfer Technologies Over 100 years ago, the concept of wireless power transmission began with the patented ideas and demonstrations by Tesla [1][2], he describes a method for utilizing effects transmitted through natural media. In this patent, Tesla first describes several ways of transmitting electrical disturbances through the natural media: One of these ways consists of producing by a suitable apparatus rays or radiations that is disturbances which are propagated in straight lines through space, directing them upon a receiving or recording apparatus at a distance, and thereby bringing the latter into action. This method has been brought particularly into prominence in recent years through investigations by Heinrich Hertz." Power transmission by radio waves dates back to the early work of Heinrich Hertz around 1880, who demonstrated the electromagnetic wave propagation in free space using parabolic reflectors at both ends (transmitting and receiving) of the system. Though described in somewhat confusing legal language, it is obvious that the disturbances in Tesla's patent are electromagnetic waves. Claim 11 of this patent specifies that the patented method of utilizing effects or disturbances transmitted through the natural media from a distant source, which consists in storing in a condenser electrical energy derived from an independent source, and using, for periods of time predetermined as to succession and duration, the accumulated energy so obtained to operate a receiving device. What is described above is wireless transmission of energy, storage of the energy in a capacitor and energy management over time. [1]
1.2 Recent Technologies of Rectenna The word rectenna is composed of rectifying circuit and antenna. The rectenna and its word were invented by W. C. Brown in 1960's. The rectenna can receive and rectify a microwave power to DC, is passive element with a rectifying diode, operated without any power source. The antenna of rectenna can be any type such as dipole, Yagi-Uda antenna, microstrip antenna, monopole, coplanar patch, spiral antenna, or even parabolic antenna. The rectenna can also take any type of rectifying circuit such as single shunt full-wave rectifier, full-wave bridge rectifier, or other hybrid rectifiers. The circuit, especially diode, mainly determines the RF-DC conversion efficiency, rectennas with FET [19] or HEMT [11] appear in recent years. (The rectenna using the active devices is not passive element).The world record of the RF-DC conversion efficiency among developed rectennas is approximately 90% at 8W input of 2.45 GHz microwave.
1.3 General Block Diagram
In the figure we can see how our system works: 1. First, the antenna is in charge of capturing all the RF signals; 2. Then the rectifier circuit will “extract” the power from those signals and convert it in DC voltage efficiently. 3. The Low Pass filter circuit helps in removing unwanted frequencies. Several operating frequencies for the rectenna have been investigated in the literature. Traditionally the 2.4 GHz Industrial Scientific and Medical (ISM) band has been utilized due to the presence of Wi-Fi networks; additionally the 5.8 GHz ISM band has also been considered which implies a smaller antenna aperture area than that of 2.4 GHz. Both frequency bands present similar advantages because they have comparably low atmospheric loss, cheap components availability, and high conversion efficiency. [4][8] The frequency bands corresponding to mobile telephone systems such as 800 MHz, 900 MHz and 1800MHz also present good alternatives for electromagnetic energy harvesting systems, although they require a larger antenna size. A starting point is to ask ourselves if there is an efficient way to power active devices. Along the previous years, there have been some methods proposed and implemented: microwave power transmission, bio-batteries, RFID, surface acoustic wave devices, piezoelectric generators, differential-heat generators, solar cells, and so on. [2] This work has two goals: 1. Powering of low-power applications 2. RF energy recycling. If we consider that the use of batteries has some disadvantages like the limited life period they have, plus the pollution generated from their disposal, it is very encouraging to think that if every wireless sensor in the world have the kind of power source presented in this work, it would be a great progress in the way we try to keep our planet clean.
1.4 Application in the ISM band (2.4-2.5 GHz) 2.4-2.5 GHz emerged as the transmitting frequency of choice due to its advanced and efficient technology base, location at the center of an industrial, scientific, and medical (ISM) band, and its minimal attenuation through the atmosphere even in heavy rainstorms, then the conversion efficiency of the rectenna continued to increase from the 1960's through the 1970's at this frequency. A important application for wireless power transmission is to identification tags. Invented in 1980, in recent years, there has been a trend to take RFID (Radio Frequency Identification) technology from labs to commercial applications.[6][7] In this application, the system must maximize reading distance and robustness to collisions with cheap tag fabrication. Tags can be used to keep track on some retail products for inventory control, automatic selling systems, intelligent systems at home, and so on. RF-ID is the first commercial wireless power transmission application system in the world Rectennas are used for converting wireless RF power into DC power. The challenge lies in maximizing the power conversion efficiency for low input power and – at the same time– minimizing the dimensions of the rectenna. By conjugate matching a rectifying circuit directly to a micro strip patch antenna, a matching and filtering network between the antenna and rectifying circuit can be avoided[6][13]. With the aid of analytical models for the antenna and the rectifying circuit, single-layer, internally matched and filtered PCB rectennas may be designed for low input power. An efficiency of 52% for 0 dBm input power has been realized at 2.45 GHz for a rectenna on a standard PCB material. A series connection of these rectennas is able to power a standard household electric wall clock.
Chapter 2: RECTENNA DESIGN The design and simulation results of a single rectenna working at ISM band 2.4 GHz will presented in the following pages. The software used to design and simulate the micro strip patch antenna was IE3D[21] while the design for the rectifying circuit was accomplished in Advanced Design Systems(ADS) by Agilent.[14] The antenna was chosen to be a micro strip square patch with inset feed matched to a 50 Ω transmission line The antenna was simulated using the Method of Moments technique in IE3D while the Rectifying circuit was simulated using the Harmonic Balance method in Advanced Design Systems Simulator.[14][15]
2.1 Brief Background on Simulation tools used 2.1.1 Harmonic Balance Simulation For analyzing nonlinear circuits, two major techniques are known: the time domain based large signal - small signal and the frequency domain based harmonic balance analysis. The Harmonic Balance method has the advantage of avoiding time constants, which are much greater than the inverse of the excitation frequency and require integration over many periods.[14] These can differ from each other by several orders of magnitude, which would cause problems for numerical solvers of the nonlinear differential equations. HB analysis is performed in the frequency domain Fourier space, thus avoiding differential equations.[14][17] The entire circuit is split up into a linear and a nonlinear sub-circuit connected by N ports. Because the nonlinear devices create harmonics, the port-voltages must not only be known for the sinusoidal fundamental frequency of the excitation, but for all harmonics k = 1 ::: K, up to a given cut-off. For the entire circuit, assuming it is an M-port, the following systems scan be written:
where Um;k and Im;k are k-th harmonics of port voltages, or respective currents, and Ylin and ^ Ynlin are the admittance matrices of the sub-circuits. The hat notation relates to the nonlinear sub-circuit, whereas letters without hats belong to the linear subcircuit. For the N connecting ports, In;k = -I’n;k, i.e. Kirchhoff's current law, and Un;k = -U’n;k, i.e. Kirchhoff's voltage law, must be satisfied for all n = 1 ::: N. To solve for the entire circuit, port-voltages Un;k have to be found, that solve both equations, so that In;k = -I’n;k. As soon as those voltages are found, the circuit is analyzed. 2.1.2 Momentum Simulation Agilent Momentum is based on the Method-of-Moments (MoM) which is a numerical method to solve Maxwell’s equations for planar structures in multilayer dielectric substrates [18]. The conducting surfaces of a given antenna structure are meshed into different cells and the currents flowing on them are discretized and expanded in a set of basic functions according to the mesh structure and subsequently determined numerically. In addition to simulating antenna structures, this type of simulation is used to accurately determine the electromagnetic behavior of planar transmission lines and interconnects. Compared to a circuit simulator such as Agilent S-parameter simulator, it additionally accounts for radiation, as well as coupling among adjacent circuit components. In the simplest case, the basic functions are rectangular approximations to the Dirac delta function. Because the widths of the rectangular sections are non-zero, only a finite (reasonably small) number of them are needed to cover the antenna wire structure. The next more complicated basis functions are triangular in shape. This gives a smoother approximation to the current distribution, in which the current distribution is piecewiselinear between the matching points. In general, the “n-th moment” is obtained by integrating the product of the Green’s function with the n-th basis function.[15] 2.1.3 LineCalc Tool The dimensions of the various transmission lines used in the antenna and rectenna design were obtained using the tool LineCalc of Agilent ADS. [14][15] Given the physical dimensions and material properties, LineCalc accurately computes and for microstrip as well as for a large number of other planar waveguides. Conversely, it can synthesize a land width given the other parameters such as and frequency. An example of the graphical interface of LineCalc is shown[17]
Chapter 3: ANTENNA
(Square Patch Microstrip Antenna) 3.1 Brief Introduction A microstrip patch antenna consists of a very thin metallic patch (usually gold or copper) placed a small fraction of a wavelength above a conducting ground plane, separated by a dielectric substrate. [17][18] Microstrip antennas have numerous advantages such as 1. They are light weight, they can be designed to operate over a large range of frequencies (1- 40 GHz.) 2. They can easily be combined to form linear or planar arrays, and they can generate linear, dual, and circular polarizations. 3. These antennas are inexpensive to fabricate using printed circuit board etching, which makes them very useful for integrated active antennas in which circuit functions are integrated with the antenna to produce compact transceivers. 4. Microstrip antennas can be in various shapes and configurations but for the purpose of this work a square patch microstrip antennas was used.
3.2 Some Important Performance Parameters
3.2.1 ANTENNA EFFICIENCY The efficiency of an antenna relates the power delivered to the antenna and the power radiated or dissipated within the antenna. A high efficiency antenna has most of the power present at the antenna's input radiated away. A low efficiency antenna has most of the power absorbed as losses within the antenna, or reflected away due to impedance mismatch.[18] The antenna efficiency (or radiation efficiency) can be written as the ratio of the radiated power to the input power of the antenna:
The total efficiency of an antenna is the radiation efficiency multiplied by the impedance mismatch loss of the antenna, when connected to a transmission line or receiver (radio or transmitter). This can be summarized in the following equation
where et= total efficiency Ml=loss die to mismatch er=antenna radiation efficiency
3.2.2 VSWR An antenna's impedance is important for minimizing impedance-mismatch loss. A poorly matched antenna will not radiate power. This can be somewhat alleviated via impedance matching, although this doesn't always work over a sufficient bandwidth. A common measure of how well matched the antenna is to the transmission line or receiver is known as the Voltage Standing Wave Ratio (VSWR). VSWR is a real number that is always greater than or equal to 1. A VSWR of 1 indicates no mismatch loss (the antenna is perfectly matched to the Tx line). Higher values of VSWR indicate more mismatch loss. Practically antenna design aims to reduce achieve a VSWR of less than 2.[17][18] 3.2.3 Bandwidth Bandwidth is typically quoted in terms of VSWR. For instance, an antenna may be described as operating at 100-400 MHz with a VSWR<2. This statement implies that the reflection coefficient is less than 0.2 across the quoted frequency range. Hence, of the power delivered to the antenna, only 4% of the power is reflected back to the transmitter. Alternatively, the return loss S11=20*log10(0.2)=-13.98 dB.
3.3 FEED TECHNIQUES Microstrip patch antennas can be fed by a variety of methods.
These methods can be classified into two categories- contacting and non-contacting. In the contacting method, the RF power is fed directly to the radiating patch using a connecting element such as a microstrip line. In the non-contacting scheme, electromagnetic field coupling is done to transfer power between the microstrip line and the radiating patch. The four most popular feed techniques used are:1. The microstrip line, 2. Coaxial probe (both contacting schemes), 3. Aperture coupling and 4. Proximity coupling (both non-contacting schemes). In our antenna design we have used the Microstrip line feed technique (Inset feed) to couple power power captured by the antenna to a rectifying circuit.[5][18] 3.3.1 MICROSTRIP LINE FEED In this type of feed technique, a conducting strip is connected directly to the edge of the microstrip patch as shown in figure. The conducting strip is smaller in width as compared to the patch and this kind of feed arrangement has the advantage that the feed can be etched on the same substrate to provide a planar structure.
The purpose of the inset cut in the patch is to match the impedance of the feed line to the patch without the need for any additional matching element. This is achieved by properly controlling the inset position. Hence this is an easy feeding scheme, since it provides ease of fabrication and simplicity in modelling as well as impedance matching.
However as the thickness of the dielectric substrate being used, increases, surface waves and spurious feed radiation also increases, which hampers the bandwidth of the antenna. The feed radiation also leads to undesired cross polarized radiation.[17][18]
3.4 Formulas Used in the Design of Patch Antenna The Micro strip patch antenna was designed to work in the ISM range centred around 2.4 GHz. For this purpose the following design aspects and parameters were used/calculated. Because of the fringing effects, electrically the patch of the antenna looks larger than its physical dimensions; the enlargement on L is given by ∆L = 0.412d(εreff + 0.3)(W/h + 0.264)/[(εreff − 0.258)(W/h + 0.8)] Where the effective (relative) permittivity is
The effective length of the patch is now Leff = L + 2 ∆L For a given resonance frequency fo, the effective length is given by as
An optimized width for an efficient radiator is
Based on these simplified formulas, we can adopt the following design procedure to design the antenna:
3.5 Design a rectangular patch The three essential parameters for the design of a rectangular Microstrip Patch Antenna are: • Frequency of operation ( fo ) : 2.4 GHz. • Dielectric constant of the substrate ( εr ) : 4.22 • Height of dielectric substrate ( h ) : 1.6 mm. Following the design procedure suggested above and using the formulas to write code in MATLAB we obtain: •
Width of the antenna (W)
:
38.7 mm
•
Length of the antenna (L)
:
30.1 mm
•
Effective Dielectric Constant (εreff)
:
3.9262
A linearly polarized microstrip patch antenna (30.1 mm x 38.7 mm) has been associated with the rectifier to obtain the complete rectenna. The antenna simulation was carried out using the electromagnetic simulator IE3D (Version 14.1)[15]. The antenna has been achieved and measured in a first time. It showed a good input matching level at 2.4 GHz. The input impedance behaviour for a coaxial probe-fed patch antenna has been studied analytically by means of various models, including the transmission-line model and the cavity model, and by means of full-wave analysis. Experimentally and theoretically, it has been found that an inset fed-patch antenna's input impedance exhibits behavior that follows the trigonometric function:
Zin(x0) = Zin(0) cos2[π(y0/L)]
where: Zin(y0) = Input Impedance at distance y0 from the edge Zin(0) = Impedance at the edge L = the length of the patch and x0 = the position of the feed from the edge along the direction of the patch length L.
Zin(0) =
We can find that the recessed distance (the length cutting into the patch) is
The width of the microstrip line feed of 50 ohm calculated using line calculator is
wo = 3.071 mm
Patch antenna with dimensions
Chapter 4: LOW PASS FILTER The rectifier has a nonlinear characteristic and converts RF power into useful dc power. A rectifier is often made up of a combination of Schottky diodes, an input HF filter, an output bypass capacitor and a resistive load. Usually, the input HF filter is a low pass filter (LPF) which rejects harmonics created by the diode. It also acts as a matching circuit between the antenna and the rectifying circuit. This low pass filter can be directly included on the radiating element by using harmonic-rejecting antennas.
4.1 MICROWAVE FILTERS Radio frequency (RF) and microwave filters represent a class of electronic filter, designed to operate on signals in the megahertz to gigahertz frequency ranges (medium frequency to extremely high frequency). This frequency range is the range used by most broadcast radio, television, wireless communication (cellphones, Wi-Fi, etc...), and thus most RF and microwave devices will include some kind of filtering on the signals transmitted or received. Such filters are commonly used as building blocks for duplexers and diplexers to combine or separate multiple frequency bands.[7] In our design the Filter system implemented is a low pass filter to help reject harmonics generated by the non linear diodes used for rectification. Various Filter technologies are available like Lumped Element LC filters, Distributed element filters, Coaxial Filters, Cavity filters etc. For our project, we have implemented the filter circuit using the Distributed Element Filter approach. 4.1.1 Distributed Element Filter A distributed element filter is an electronic filter in which capacitance, inductance and resistance (the elements of the circuit) are not localised in discrete capacitors, inductors and resistors as they are in conventional filters. The distributed element model applies at all frequencies, and is used in transmission line theory; many distributed element components are made of short lengths of transmission line. The filter design is usually concerned only with inductance and capacitance, but because of this mixing of elements they cannot be treated as separate "lumped" capacitors and inductors. There is no precise frequency above which distributed element filters must be used but they are especially associated with the microwave band (wavelength less than one metre). Distributed element filters, cause a discontinuity on the transmission line. These discontinuities present a reactive impedance to a wavefront travelling down the line, and these reactances can be chosen by design to serve as approximations for lumped inductors, capacitors or resonators, as required by the filter. The most noticeable difference in behaviour between a distributed element filter and its lumped-element approximation is that the former will have multiple passband replicas
of the lumped-element prototype passband, because transmission line transfer characteristics repeat at harmonic intervals.[19] In order to realise a required Filter circuit, it was first designed as a lumped element filter and then converted into a Distributed Element Model. The conversion was carried out using Richard’s Transformation and Kuroda Identities. 4.1.2 RICHARD’S TRANSFORMATION Richards' transformation allows a lumped element design to be taken "as is" and transformed directly into a distributed element design using a very simple transform equation. A lumped low-pass prototype filter can be implemented using λ/8 lines of appropriate Zo to replace lumped L and C elements. Open Circuit and Short Circuited transmission line stubs can be used as replacements for inductors and capacitors since they have reactive impedances as shown.[7][18]
If ‘l’ = λ/8 , the following identities hold for a capacitor and inductor
4.1.3 KURODA’S IDENTITIES The difficulty with Richards' transformation from the point of view of building practical filters was that the resulting distributed element design invariably included series connected elements. This was not possible to implement in planar technologies and was often inconvenient in other technologies. This problem was solved by K. Kuroda who used impedance transformers to eliminate the series elements [7]. He published a set of transformations known as Kuroda's identities Kuroda’s Identities are used for the following: 1. Physically separate transmission line stubs. 2. Transform series stubs into shunt stubs. 3. Change impractical characteristic impedances into more realizable ones
Given Circuit
Kuroda Transformation
Chapter 5: RECTIFIER At low RF frequencies (kilohertz to low megahertz), both p-n diodes and transistors are used as rectifiers. At microwaves (1 GHz and higher), Schottky diodes (GaAs or Si) with shorter transit times are required. For low-power applications, as is the case for collected ambient energy, there is generally not enough power to drive the diode in a high-efficiency mode. The diode is not externally biased in this application, so it is important to use a diode with a low turn-on voltage.
5.1 Rectifying Circuit The forward voltage drop (VF), reverse-recovery time (trr), and junction capacitance (CJ) of Schottky diodes are closer to ideal than the average “rectifying” diode. This makes them well suited for high-frequency applications. Unfortunately, though, Schottky diodes typically have lower forward current (IF) and reverse voltage (VRRM and VDC) ratings than rectifying diodes and are thus unsuitable for applications involving substantial amounts of power. Though they are used in low voltage switching regulator power supplies. The used Schottky diodes are characterized by a low parasitic capacitance CJ0 (0..14 pF) and a low serial resistor RS (20 Ω).. At microwave frequencies, rectifiers are highly nonlinear and difficult to design based upon purely analytic equations. Commercially available harmonic-balance (HB) simulators are useful at low power levels. When looking for a rectifying diode in the context of RF recycling, a diode with a high conversion efficiency, even for very small incident power levels is required.
A glance at the above figure will suggest that two types of single diode detectors be combined into a full wave rectifier [20](known also as a two diode voltage doubler). Such a circuit offers several advantages. First the voltage outputs of two diodes are added in series, increasing the overall value of voltage sensitivity for the network (compared to a single diode detector). Second, the RF impedances of the two diodes are added in parallel, making the job of reactive matching a bit easier. In our Rectifier Circuit we have used the HSMS 2850 Schottky Diode. Agilent’s HSMS-285x family of zero bias Schottky detector diodes has been designed and optimized for use in small signal (Pin <-20 dBm). They are ideal for RF/ID and RF Tag applications where primary (DC bias) power is not available [20].
Chapter 6: Simulation Results 6.1 Microstrip Patch Antenna 6.1.1 Patch Antenna 3-D Geometry
6.1.2 Simulation Results
VSWR
S-Parameter
Efficiency vs. Frequency
Total Field Vs. Frequency
3-D Radiation Pattern
6.2 Rectifying Circuit 6.2.1 Circuit Diagram
6.2.2 Input v/s Output Graphs
Input Power= -10dB
Input Power= 0 dB
Input Power= 10dB
Conclusion In this study, a low cost and efficient rectenna, based on modified bridge configuration, has been accurately designed and optimized by means of ADS Agilent simulation technique. Due to the differential measurements of the output dc voltage, no via-hole connection is required. Also, no input low pass filter is needed due to the no rejection of harmonics at the input (P0) of the rectifier.
REFERENCES [1] Nicolas Tesla. Experiments with Alternate Current of High Potential and High Frequency. McGraw, 1904. [2] William C. Brown. “The history of power transmission by radio waves”. IEEE Trans. MTT, 32(9):1230{1242, 1984. [3] N. Shinohara.”Wireless power transmission for solar power satellite” (sps second draft). 2006. http://www.sspi.gatech.edu/wptshinohara.pdf. [4] W. C. Brown. “An experimental low power density rectenna”. IEEE MIT-S Int. Microwave Symp, 1991. [5] Gianfranco Andi Vera. “Efficient Rectenna Design for Ambient Microwave Energy Recycling” Escola Tecnica Superior d'Enginyeria de Telecomunicaci_o de Barcelona, July2009 [6] Omar André Campana Escala. “Study of the efficiency of rectifying antenna systems for electromagnetic energy harvesting” , Escola Tècnica Superior d‟Enginyeria de Telecomunicació de Barcelona Department de Teoría de Senyal i Comunicacions ,October 2010 [7] David M. Pozar. “Microwave Engineering”, John Wiley &Sons, Inc. 1998 [8] H Takhedmit, B Merabet, L Cirio, B Allard, F Costa, C Vollaire, O Picon “A 2.45-GHz low cost and efficient rectenna”, IEEE Antennas and Propagation EuCAP 2010 Proceedings of the Fourth European Conference on (2010) [9] Zied Harouni, Lotfi Osman and Ali Gharsallah. “Efficient 2.45 GHz Rectenna Design with High Harmonic Rejection for Wireless Power Transmission”, University of Tunis El Manar, 05/UR/11-10: CSEHF, El Manar 2092, Tunisia [10] J. A. G. Akkermans, M. C. van Beurden, G. J. N. Doodeman, and H. J. Visser, “Analytical models for low-power rectenna design,” IEEE Antennas Wireless Propag. Lett., vol. 4, pp. 187–190, 2005. [11] J. Zbitou, M. Latrach and S. Toutain, “Hybrid Rectenna and Monolithic Integrated ZeroBias Microwave Rectifier”, IEEE Trans. on Microw. Theory and Tech., vol. 54, no.1, pp 147152, Jan. 2006. [12] H. Takhedmit, B. Merabet, L. Cirio, B. Allard, F. Costa, C. Vollaire and O. Picon, “Design of a 2.45 GHz rectenna using a global analysis technique,” EuCAP 2009, Berlin, Germany, 23-27, March 2009. Pp 2321-2325. [13] A. Douyere, J.D. Lan Sun Luk and F. Alicalapa, “High efficiency microwave rectenna circuit: modeling and design,” Electronics Letters, vol. 44, no. 24, Nov. 2008. [14] (2009) The Advanced Design System by Agilent [15] IE3D Software Release 14.1 (Zeland Software Inc., Fremont, California,USA [16] Hewlett Packard, Technical Data “Surface Mount Microwave Schottky Detector Diodes”. [17] JAMES J.R., and HALL P.S., ―Handbook of Microstrip Antennas Peter Peregrinus Ltd., London, UK, 1989 [18] Balanis, C.A., ‘Antenna Theory: Analysis and Design’, Third Edition, John Wiley & Sons, Inc, 2005. [19] Qijuan He and Changjun Liu. “An Enhanced Microwave Rectifying Circuit Using HSMS-282”, School of Electronics and Information Engineering, Sichuan Uni versity, Chengdu 610064, China; [20]Agilent Technologies. “Surface Mount Zero Bias Schottky Detector diode” Technical Data Sheet
