X-Band Planar Rectenna Giuppina Monti,Luciano Tarricone,and Michele Spartano
Abstract—This letter prents a novel X-band planar rectenna (i.e.,a rectifying antenna).The propod device consists of a slot antenna and a microstrip rectifying circuit.A realization on a low-cost FR4substrate,using a surface-mount Schottky barrier diode (the HSMS-8202diode by Avago Technologies)as the rectifying el-ement,is propod.Measurements performed at9.3GHz demon-strate that an RF-to-DC conversion efficiency of about21%can be obtained with an input power density of245W/cm.
Index Terms—Conversion efficiency,planar antennas,rectenna, wireless power transmission.
I.I NTRODUCTION
W IRELESS Power Transmission(WPT)is a promising technology[1]–[4].There are veral potential areas of application.Among the,WPT can be ud to power battery-less nsors for noninvasive monitoring systems,or to power smart material actuators for applications in vehicle systems.The key component of WPT systems is the rectifying antenna(rectenna),which is a device designed to convert a propagating electromagnetic wave into direct current(dc) power[1]–[14].A schematic reprentation of a rectenna is given in Fig.1.The basic architecture consists of three esntial comp
onents:the antenna,the rectifying element(generally a diode),and the load.In order to improve the conversion efficiency,two additional blocks can be added:a passband filter and a low-passfilter,positioned before and after the diode,respectively.Thefilters accomplish two major tasks:filtering and matching.More specifically,the passbandfilter (positioned between the antenna and the diode)is ud to ob-tain a good impedance matching between the antenna and the rectifying circuit and to prevent the antenna from reradiating the high-order harmonics generated by the diode.
As for the dcfilter,positioned between the load and the diode, it is ud for matching and ensuring that only the direct compo-nent of the signal reaches the load.
In the last years,veral rectenna designs have been propod[6]–[11].Among the,in[6],a circularly polar-ized rectenna working at5GHz is prented.The achieved conversion efficiency is57%when the incident power is 2.55mW/cm.Similarly,in[7],experimental results referring劳务合同电子版
Manuscript received July13,2011;revid September02,2011;accepted September28,2011.Date of publication October10,2011;date of current ver-sion October20,2011.
The authors are with the Department of Innovation Engineering,University of Salento,73100Lecce,Italy(i@unisalento.it;luciano. tarricone@unisalento.it).
Color versions of one or more of thefigures
形容文笔好的词语
in this letter are available online at
Digital Object Identifier10.1109/LAWP.2011.2171029Fig.1.General architecture of a rectenna.
to a C-band circularly polarized rectenna are reported demon-strating a conversion efficiency greater than70%when the input power is between30and135mW.In[8],bad on the u of an annular ring-slot antenna,a planar rectenna is prented; the measured conversion efficiency is about25%when the input power is1mW and about17%when the input power is 316W.In[9],the antenna and the rectifying circuit have been realized on different substrates coupled by apertures,resulting in a two-la
yer rectenna;the achieved conversion efficiency is 30%at47mW input power.In[10],an ultrawideband rectenna array is propod;the measured conversion efficiency is about 20%for an88array when the incident power density is 62W/cm.
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In this letter,we propo a planar low-profile rectenna for X-band applications.The device has been realized on a low-cost FR4substrate;the rectifying element is a Schottky barrier diode by Avago Technologies.Experimental results referring to a single rectenna and to a three-element array are reported and discusd.In both cas,a conversion efficiency of about21% was measured with a power density incident on the antenna of 245W/cm.
The letter is structured as follows.The architecture of the pro-pod antenna is briefly described in Section II,experimental results for a single rectenna element and a three-element array are given in Section III,and some conclusions are drawn in Section IV.
II.R ECTENNA G EOMETRY
The layout of the X-band rectenna prented here is illus-trated in Fig.2.The substrate is a low-cost FR4laminate( ,)with a thickness of1.6mm.The corre-sponding lumped-element equivalent circuit is given in Fig.3. The radiating element is a micircular slotted antenna[14]fed by a micircular mono
pole.The slot has been applied on the feeding monopole to reduce the antenna dimensions and to im-prove the matching condition.In order to obtain higher values of the gain,the antenna has been optimized in its cond working frequency band.
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Fig.2.Layout of the propod rectenna.All dimensions are in
millimeters.
Fig.3.Lumped element equivalent circuit of the propod
rectenna.
Fig.4.Scattering parameters of the step-impedance low-pass filter illustrated in Fig.2.Results obtained by means of full-wave simulations.
From Figs.2and 3,it can be noticed that the remaining part of the device consists of a matching line,a low-pass filter (LPF),a diode,and a distributed dc pass filter.
More speci fically,the diode is a surface-mount HSMS-8202Schottky barrier diode by Avago Technologies [15].As for the LPF,it is a step-impedance Butterworth filter of 5th order;it was optimized in order to have an attenuation lower than 0.2dB in [9GHz,10GHz],which is the operating frequency range of the propod rectenna,and an attenuation greater than 15dB for frequencies above 18GHz.This way,the LPF rejects the high-order harmonics generated by the diode.The corresponding scattering parameters calculated by means of full-wave simulations are given in Fig.
4.
Fig.5.(a),(b)Photographs of the realized rectenna.(c)Realization ud to measure the re flection coef ficient illustrated in Fig.6.(d)Single-element rectenna.(e)Three-element rectenna array.
As highlighted in the int of Fig.2,a microstrip gap capac-itor in shunt con figuration with the resistive load was also de-signed.This capacitor works as a dc filter,so that only the dc current reaches the load.From Figs.2and 3,it can be also no-ticed the prence of a microstrip line working as an inductance (of Fig.3);the aim of this inductance is to short-circuit to ground the dc component
of the signal improving the RF-to-DC conversion ef ficiency.
In the ction of the diode,the input impedance of the pro-pod layout calculated by means of full-wave simulations is ().According to the equivalent circuit reported in the data sheet,this value should guarantee a good level of matching with the HSMS-8202diode.
Some photographs of the realized rectenna are given in Fig.5.More in detail,Fig.5(a)shows the realization ud to mea-sure the re flection coef ficient of the ries of the antenna and the LPF (the SMA connector is placed at the end of the step impedance LPF).Corresponding results are reported in Fig.6(a)and compared to full-wave simulations;a re flection coef ficient lower than 10dB has been measured in the frequency range [8.6GHz,10.7GHz].In the same frequency band,values of the antenna gain greater than 5.5dB have been calculated by means of full-wave simulations [e Fig.6(b)].
III.E XPERIMENTAL R ESULTS
The experimental tup adopted to perform measurements is illustrated in Fig.7.In order to generate the microwave power incident on the antenna,an X-band microwave system with a Klystron oscillator has been ud.The transmitting antenna is a standard linearly polarized horn antenna with a gain of
10dB and an aperture of (57,5)cm .
Measurements were performed by placing the propod rectenna at a distance of 45cm from the transmitting horn antenna,thus guaranteeing with a good approximation that both antennas were operating in their far-field region.
Fig.6.(a)Re flection coef ficient of the propod rectenna measured by using the realization illustrated in Fig.5(a)and (b).The SMA connector is placed at the end of the step impedance LPF.(b)Gain of the propod rectenna calculated by means of full-wave
simulations.
Fig.7.Experimental tup adopted to measure the conversion ef ficiency of the propod rectenna.
We u the following de finition of the RF-to-DC conversion ef ficiency ():
(1)
where
is the power density incident on the antenna,雨伞手工
is the dc output voltage,and is the resistive
鲁雨亭load.is the effective area of the antenna calculated by using the Gain ()obtained by means of full-wave simulations
(2)
According to (1),
was measured as function of with our transmitting system working at the maximum output power.By using this con figuration,
we measured a power density incident on the rectenna ()equal to
Fig.8.Measurements of the conversion ef ficiency.(a)Conversion ef ficiency as function of the load when the input power density is 245W/cm in the ca of a single rectenna and in the ca of a three-elements array.(b)Conversion
ef ficiency as function of the input power density when the load is 300
in the ca of a single rectenna.(c)Conversion ef ficiency calculated by means of circuital simulations.
W/cm .More speci fically,in order to measure ,the
PMM 8053A broadband field meter with the EP-183isotropic probe was ud.
Results are given in Fig.8(a).It can be noticed that a max-imum of about 21%has been measured when the load is 300,the corresponding output voltage being 220mV.The measured values of as function of the input power density are illustrated in Fig.8(b).It is important to under-line that greater values of are expected when using greater values of .Indeed,according to circuital simula-tions bad on the Harmonic Balance (HB)method,values of
greater than 50%can be obtained when is greater
than 1,25mW/cm [e Fig.8(c)].
In circuital simulations,the input impedance of the antenna and its effective area have been taken into account.Similarly,full-wave simulation results have been ud for the LPF,the gap capacitor,and the distributed inductor.
An array of three rectennas connected in ries was also realized [e Fig.5(d)and (e)][10]–[13].This con figuration sums the dc signal generated by each rectenna of the array.The corresponding measured conversion ef ficiency is shown in Fig.8(a).As expected,the conversion ef ficiency is substantially
Fig.9.Conversion efficiency measured for different frequencies of the input signal.A resistive load of300has been ud in all measurements.
the same measured for the single rectenna.However,in this ca the output voltage corresponding to the maximum is about 375mV.This result is in agreement with the voltage expected from(1).Indeed,we have
-
element array
-element array
于谁流光之火single element
-element array
single element
-element array
single element
It is worth to underline that,as demonstrated in[10],this result can be improved by means of an accurate optimization of the dc connections and their realization. Measurements of the conversion efficiency versus frequency were also performed,and results are illustrated in Fig.9(the input power density was approximately equal to245W/cm for all measurements).It can be noticed that values higher than 17%were obtained in the frequency range[8.7–10]GHz.
清蒸鲈鱼最简单的做法
IV.C ONCLUSION
A low-profile,low-cost X-band rectenna has been pre-nted.The propod architecture compris a step-impedance low-passfilter and a dc-pass distributed capacitor,whereas the rectifying circuit consists of a single surface-mount HSMS-8202Schottky barrier diode.
Measurements performed on a single rectenna and on a three-element array show a conversion efficiency of about 21%when the power density incident on the antenna is 245W/cm.The results demonstrate that the propod device is well suited for low-power applications and can be easily arranged in array configurations.十五岁的重新开始
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