Hubbry Logo
RectennaRectennaMain
Open search
Rectenna
Community hub
Rectenna
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Rectenna
Rectenna
Rectenna
View on Wikipedia
from Wikipedia

A rectenna (rectifying antenna) is a special type of receiving antenna that is used for converting electromagnetic energy into direct current (DC) electricity. They are used in wireless power transmission systems that transmit power by radio waves. A simple rectenna element consists of a dipole antenna with a diode connected across the dipole elements. The diode rectifies the AC induced in the antenna by the microwaves, to produce DC power, which powers a load connected across the diode. Schottky diodes are usually used because they have the lowest voltage drop and highest speed and therefore have the lowest power losses due to conduction and switching.[1] Large rectennas consist of arrays of many power receiving elements such as dipole antennas.

A printed rectenna lighting an LED from a Powercast 915 MHz transmitter, flexible meshed antenna bent with a red LED light
A printed meshed rectenna lighting an LED from a Powercast 915 MHz transmitter

Power beaming applications

[edit]

The invention of the rectenna in the 1960s made long distance wireless power transmission feasible. The rectenna was invented in 1964 and patented in 1969[2] by US electrical engineer William C. Brown, who demonstrated it with a model helicopter powered by microwaves transmitted from the ground, received by an attached rectenna.[3] Since the 1970s, one of the major motivations for rectenna research has been to develop a receiving antenna for proposed solar power satellites, which would harvest energy from sunlight in space with solar cells and beam it down to Earth as microwaves to huge rectenna arrays.[4] A proposed military application is to power drone reconnaissance aircraft with microwaves beamed from the ground, allowing them to stay aloft for long periods.

A wearable millimeter-wave textile rectenna fabricated on a textile substrate for harvesting power in the 5G K-bands (20–26.5 GHz)

In recent years, interest has turned to using rectennas as power sources for small wireless microelectronic devices. The largest current use of rectennas is in RFID tags, proximity cards and contactless smart cards, which contain an integrated circuit (IC) which is powered by a small rectenna element. When the device is brought near an electronic reader unit, radio waves from the reader are received by the rectenna, powering up the IC, which transmits its data back to the reader.

Radio frequency rectennas

[edit]

The simplest crystal radio receiver, employing an antenna and a demodulating diode (rectifier), is actually a rectenna, although it discards the DC component before sending the signal to the headphones. People living near strong radio transmitters would occasionally discover that with a long receiving antenna, they could get enough electric power to light a light bulb.[5]

However, this example uses only one antenna having a limited capture area. A rectenna array uses multiple antennas spread over a wide area to capture more energy.

Researchers are experimenting with the use of rectennas to power sensors in remote areas and distributed networks of sensors, especially for IoT applications.[6]

RF rectennas are used for several forms of wireless power transfer. In the microwave range, experimental devices have reached a power conversion efficiency of 85–90%.[7] The record conversion efficiency for a rectenna is 90.6% for 2.45 GHz,[8] with lower efficiency of about 82% achieved at 5.82 GHz.[8]

Optical rectennas

[edit]
Main article: Optical rectenna

In principle, similar devices, scaled down to the proportions used in nanotechnology, can be used to convert light directly into electricity. This type of device is called an optical rectenna (or "nantenna").[9][10][11] Theoretically, high efficiencies can be maintained as the device shrinks, but to date efficiency has been limited, and so far there has not been convincing evidence that rectification has been achieved at optical frequencies. The University of Missouri previously reported on work to develop low-cost, high-efficiency optical-frequency rectennas.[12] Other prototype devices were investigated in a collaboration between the University of Connecticut and Penn State Altoona using a grant from the National Science Foundation.[13] With the use of atomic layer deposition it has been suggested that conversion efficiencies of solar energy to electricity higher than 70% could eventually be achieved.

The creation of successful optical rectenna technology has two major complicating factors:

  1. Fabricating an antenna small enough to couple optical wavelengths.
  2. Creating an ultra-fast diode capable of rectifying the high frequency oscillations, at frequency of ~500 THz.

Below are a few examples of potential paths to creating diodes that would be fast enough to rectify optical and near-optical radiation.

A promising path towards creating these ultrafast diodes has been in the form of "geometric diodes".[14] Graphene geometric diodes have been reported to rectify terahertz radiation.[15] In April 2020, geometric diodes were reported in silicon nanowires.[16] The wires were shown experimentally to rectify up to 40 GHz, that result was the limit of the instrument used, and the wires theoretically may be able to rectify signals in the terahertz region as well.

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Rectenna

View on Grokipedia
from Grokipedia
A rectenna, short for rectifying antenna, is a specialized device that efficiently converts , typically in the (RF) or range, into (DC) electricity by integrating an antenna with a circuit. The antenna captures incoming electromagnetic waves and converts them to (AC), while the —often employing diodes—transforms this AC into usable DC power, with additional components like low-pass filters and networks optimizing performance and achieving conversion efficiencies up to 90% at frequencies such as 2.45 GHz. First demonstrated in 1964 by engineer William C. Brown at Company, who powered a model remotely via , the rectenna originated as a key enabler for long-distance wireless power beaming. Rectennas have since evolved beyond microwave applications to include ambient RF energy harvesting for low-power sensors and Internet of Things (IoT) devices, as well as experimental optical rectennas operating at infrared, terahertz, and visible light frequencies for solar energy conversion, potentially surpassing the efficiency limits of traditional photovoltaic cells due to the absence of the Shockley-Queisser constraint. Notable developments include NASA's 1993 Microwave Energy Transmission in Space (METS) experiment, which tested rectenna arrays in orbit for space-based power systems, and nanoscale designs using metal-insulator-metal diodes to address higher-frequency challenges. More recent advancements as of 2025 include flexible and implantable rectennas for wearable electronics and biomedical applications. These devices are pivotal in advancing sustainable energy solutions, from satellite-to-ground power transmission to compact, self-powered electronics.

Fundamentals

Definition and Principle of Operation

A rectenna, short for rectifying antenna, is a passive device that integrates an antenna for capturing electromagnetic (EM) radiation with a circuit to convert the induced (AC) signal into usable (DC) electricity. This combination enables the efficient harvesting of EM energy from sources such as (RF) signals or , without requiring mechanical components or external power supplies. The principle of operation begins with the antenna intercepting incident EM waves, which generate oscillating electric currents proportional to the wave's strength. These AC currents, oscillating at the of the incoming , are then directed to the , typically employing diodes that conduct current preferentially in one direction, thereby converting the bidirectional AC signal into a unidirectional DC output. This rectification process relies on the nonlinear impedance characteristics of the diodes, which clip the negative voltage cycles and allow positive ones to pass, producing a pulsating DC that can be further smoothed for practical use. A basic rectenna schematic consists of the antenna connected directly or via a to the circuit—often a in a half-wave or full-wave bridge configuration—followed by a to eliminate residual AC harmonics and a load to consume the DC power. between the antenna and is essential to achieve maximum power transfer, as mismatches cause reflections that reduce the delivered energy; this is commonly accomplished using lumped elements or stubs to equate the complex impedances. The overall rectification efficiency is quantified by the equation η=PDCPincident×100%,\eta = \frac{P_{\mathrm{DC}}}{P_{\mathrm{incident}}} \times 100\%, where PDCP_{\mathrm{DC}} is the output DC power and PincidentP_{\mathrm{incident}} is the incident RF power absorbed by the device. Rectennas primarily function in the far-field regime, where the separation from the EM source exceeds several s, enabling radiative propagation and long-range power transfer through plane-wave-like fields. Near-field operation, by contrast, occurs at distances comparable to or less than the and involves evanescent fields better suited for tightly coupled systems rather than broad harvesting. Additionally, effective capture demands alignment between the polarization of the incident EM waves—linear, circular, or elliptical—and the antenna's orientation, as perpendicular polarizations result in near-zero coupling and minimal induced current.

Historical Development

The concept of the rectenna emerged in the through the work of William C. Brown at Company, who developed it for power conversion in support of initiatives on wireless energy transmission. Brown's innovations focused on integrating antennas with rectifying elements to efficiently convert signals into (DC) electricity, laying the groundwork for practical applications in beamed power systems. A landmark demonstration occurred in October 1964, when powered a model using a of 28 elements, enabling sustained flight 60 feet above a transmitter; this event, broadcast on national television, highlighted the technology's potential for mobile power delivery. Building on this, Peter E. Glaser patented a system in 1968 that incorporated rectennas on to receive microwave-beamed energy from , envisioning gigawatt-scale transmission for global energy needs. In 1975, NASA's (JPL) conducted the Goldstone demonstration, successfully transmitting 30 kW of power at 2.388 GHz over 1.54 km to a 24.5 m² , achieving over 80% DC conversion efficiency and validating long-distance . The 1990s saw renewed focus on rectenna arrays driven by studies on (SBSP), including NASA's 1993 Microwave Energy Transmission in Space (METS) experiment, which tested rectenna arrays in orbit for space-based power systems; these efforts built on prior NASA-DOE assessments to improve efficiency and integration for potential orbital . Concurrently, theoretical extensions to optical frequencies gained traction, with early proposals like Robert L. Bailey's 1972 concept evolving into nanoscale designs for and visible rectification, aiming to surpass photovoltaic limits in solar energy capture. Experimental progress in optical rectennas accelerated in the , culminating in the 2015 demonstration by Georgia Institute of Technology researchers of a device using multiwall carbon nanotubes as antennas paired with metal-insulator-metal diodes, which rectified visible light (530 nm) into DC current at low power levels, marking the first functional optical prototype. In the 2020s, advancements have pushed RF rectenna efficiencies beyond 90% in optimized prototypes, such as those reported in 2023 achieving up to 90% at 0.9 GHz under low input power.

Design and Components

Antenna Configurations

Antenna configurations in rectennas are critical for efficiently capturing electromagnetic waves across a range of frequencies, from radio to optical scales. The choice of antenna influences the rectenna's bandwidth, gain, and integration with rectifying elements, with dimensions typically scaled to the operating for optimal resonance. Common single-element types include antennas, which provide reception suitable for capturing ambient RF signals over wide bands, such as at 2.45 GHz for industrial applications. Patch antennas are favored for their compact, planar structure, enabling easy fabrication on substrates and forming the basis for arrayed systems in space-constrained environments. Slot antennas, often etched into substrates, offer advantages in integration with lines and support operation, as demonstrated in designs for RFID . To enhance power handling and , rectennas frequently employ configurations. Linear of dipoles or patches increase the effective for higher power collection, while circular provide isotropic coverage, reducing sensitivity to the orientation of the incoming wave. , incorporating phase shifters, enable in directed wireless power transmission systems, allowing focused energy reception from specific sources. For instance, a circularly polarized patch has been shown to achieve improved gain for rectenna applications at frequencies. Scaling considerations are fundamental, with dipole lengths often set to half-wavelength (λ/2) for , as in classical designs operating at 5.8 GHz. techniques address size constraints in portable or integrated systems; meandering the antenna arms or employing geometries reduces the physical footprint while maintaining , enabling compact rectennas for IoT devices. Slotting within patches can further shrink dimensions by up to 35%, preserving bandwidth for multiband operation. Polarization sensitivity is a key factor, with linear polarization common in simple dipole or patch designs but prone to losses if the incident wave is misaligned; circular polarization, achieved through truncated corners or stacked elements, mitigates this by capturing energy regardless of orientation. Typical materials include conductive metals like or gold for the radiating elements, deposited on low-loss substrates such as Rogers RT/duroid (with around 2.2) to minimize losses and support high-frequency performance.

Rectifying Circuits and Diodes

The rectifying circuit in a rectenna serves as the core component for converting received radiofrequency (RF) (AC) signals into (DC) power, primarily through nonlinear -based rectification. These circuits must operate efficiently at high frequencies while minimizing losses from diode forward and parasitic effects, enabling applications in and . Typically, the is integrated directly with the antenna via to maximize power transfer, and it often includes filtering elements to isolate the DC output from RF harmonics. Schottky diodes are the most commonly employed in rectifying circuits due to their low forward (typically 0.2–0.3 V) and rapid switching speeds, which arise from majority carrier conduction without minority carrier storage, making them suitable for RF rectification up to microwave frequencies. Gallium arsenide (GaAs)-based Schottky diodes, in particular, offer enhanced performance with reported efficiencies up to 92% at 2.45 GHz, attributed to their higher and lower series resistance compared to variants. For high-power applications, (SiC)-based Schottky diodes, such as those incorporating junctions, provide robustness with cutoff frequencies exceeding 100 GHz and zero-bias of 0.14 A/W at 90 GHz, outperforming traditional metal/SiC diodes by orders of magnitude in THz regimes. Zero-bias Schottky diodes, with threshold voltages around 150 mV and junction capacitances as low as 0.18 pF, are particularly advantageous for passive, low-power harvesting scenarios, enabling operation without external and efficiencies around 30% at input powers of 10 mW. Common circuit topologies balance simplicity, output voltage, and efficiency. The single-series configuration offers straightforward implementation and optimal efficiency at low input powers (-10 to 20 dBm), producing outputs like 11.23 V at 20 dBm across a 2 kΩ load at 2.45 GHz, though it yields lower voltages inherently. topologies, combining series and shunt elements, enhance output voltage (e.g., 10.75 V at 22 dBm with 71.5% efficiency) but exhibit reduced conversion efficiency at lower powers due to increased losses. Greinacher circuits, a form of symmetrical using two half-wave rectifiers, achieve high efficiencies such as 74.38% at 10 dBm and 5.8 GHz, providing a compact solution for moderate power levels. Bridge rectifiers enable full-wave conversion for improved utilization of the AC waveform, delivering 3.64 V and 52% efficiency at 10 dBm in modified designs, albeit at the cost of requiring multiple diodes. A critical limitation in these circuits is the diode cutoff frequency, defined as fc=12πRCf_c = \frac{1}{2\pi RC}, where RR is the series resistance and CC the junction , restricting Schottky diodes to practical operations up to 100 GHz without specialized materials. Parasitic capacitance from the diode junction degrades high-frequency performance by increasing the , which is mitigated through networks that transform the antenna's (often ~50–100 Ω) to match the diode's complex impedance, thereby minimizing reflections and enhancing power delivery. Additionally, low-pass filters, typically comprising capacitors and inductors, are integrated post-rectification to suppress RF harmonics and isolate the DC output, ensuring clean power for load applications while preventing re-radiation.

Radio-Frequency Rectennas

Performance Characteristics

Radio-frequency rectennas exhibit high RF-to-DC conversion efficiencies, with demonstrated values reaching up to 90% at 2.45 GHz under ideal laboratory conditions using optimized arrays and matching networks. This peak performance is achieved in controlled environments where input is suitably high and losses are minimized, such as through precise between the antenna and . Key influencing factors include the incident , which is optimal in the range of 1-10 kW/m² for applications like space-based power systems, as lower densities reduce diode forward and increase relative losses, while excessive densities can lead to degradation. Load matching further enhances efficiency by maximizing power transfer to the , often targeting conjugate impedance to minimize reflections and achieve over 80% conversion in designs. Rectennas for RF applications typically operate across frequencies from 900 MHz to 35 GHz, encompassing ISM bands like 902-928 MHz, 2.4-2.5 GHz, 5.8 GHz, and 24 GHz for and . Bandwidth limitations stem from the resonant nature of antennas and the frequency-dependent characteristics of rectifying , often restricting effective operation to 10-20% fractional bandwidth without specialized designs like multi-band patches. Harmonic suppression is critical to performance, as second- and third-order harmonics generated by nonlinear diode rectification can re-radiate power and reduce ; integrated filters or antenna structures with rejection notches mitigate this by attenuating harmonics beyond the fundamental band. The theoretical power conversion efficiency for an ideal half-wave rectifier in a rectenna is expressed as η=8π2×VoutVin,\eta = \frac{8}{\pi^2} \times \frac{V_\text{out}}{V_\text{in}}, where VoutV_\text{out} and VinV_\text{in} represent the output DC voltage and input RF voltage, respectively; this assumes lossless components and perfect matching. In practice, real-world efficiencies are lower due to losses from diode series resistance, which introduces voltage drops and heating, particularly at low input powers, where parasitic capacitances further degrade performance. Environmental factors significantly affect rectenna operation in practical deployments. Power density decreases according to the with distance from the source, limiting effective range to tens of meters for kilowatt-scale transmitters at frequencies and necessitating configurations for longer distances. Multipath interference from reflections in urban or indoor settings can cause signal , but this is mitigated through designs that maintain consistent reception across varying propagation paths, improving overall harvested power stability in multipath-rich environments.

Fabrication and Optimization

Fabrication of radio-frequency rectennas typically involves a range of techniques tailored to the desired frequency range, cost constraints, and application scale. For low-cost prototypes, etching on substrates like is widely employed due to its simplicity and affordability, enabling the creation of or patch antennas integrated with rectifying circuits. This method supports frequencies up to several GHz and is common in ambient devices. For high-frequency arrays operating in the millimeter-wave regime, provides the necessary precision to pattern fine features, such as sub-wavelength antenna elements and connections, ensuring minimal losses and accurate alignment. Emerging approaches like facilitate conformal designs on flexible or curved surfaces, using conductive filaments to build multilayer structures directly, which is advantageous for wearable or integrated systems. Recent advances as of include flexible textile-based rectennas for wearable applications, achieving efficiencies over 70% at 2.45 GHz. Optimization of rectenna performance focuses on enhancing , bandwidth, and compactness through computational and structural strategies. Genetic algorithms are frequently applied to automate between the antenna and , iteratively evolving circuit parameters to minimize and maximize power transfer, as demonstrated in dual-band designs achieving reflection coefficients around -20 dB at 2.45 GHz and 5.8 GHz. Multi-layer stacking of antenna elements and circuits reduces overall size by up to 50% compared to single-layer configurations, allowing while maintaining operation. For high-power density applications, such as exceeding 1 kW/m², cooling systems like water-cooled wafer carriers are incorporated to dissipate heat generated in the , preventing degradation and enabling sustained operation at power densities up to 4 kW/cm². Advanced materials integration further refines rectenna capabilities; for instance, embedding metamaterials beneath the antenna extends operational bandwidth by manipulating electromagnetic wave propagation, achieving fractional bandwidths over 70% in designs. considerations are critical for scalable deployment, with mass-produced rectennas for RFID tags leveraging PCB etching and simple integration to achieve unit costs below $0.15, making them viable for billions of low-power sensors. Key challenges in fabrication include achieving high yield rates during diode placement, where misalignment can reduce rectification efficiency by up to 20% in dense arrays, necessitating precise or automated assembly. Scalability to large arrays, such as km²-scale rectenna farms for , demands modular designs to manage uniformity and thermal loads across expansive areas covering several square kilometers.

Optical Rectennas

Operating Principles at Optical Frequencies

At optical frequencies, rectennas rely on plasmonic nanoantennas to capture incident from visible and , converting the electromagnetic energy into localized surface plasmons—collective oscillations of free electrons at the metal-dielectric interface. These nanoantennas, often structured as metallic nanoparticles or patterned films, overcome the diffraction limit of by confining the to nanoscale dimensions, typically tens to hundreds of nanometers, where the antenna resonance matches the . For example, or bowtie geometries enable efficient coupling to incoming , generating oscillating currents at terahertz to petahertz rates. Rectification in optical rectennas occurs through metal-insulator-metal (MIM) tunnel diodes integrated at the nanoantenna feed point, where the high-frequency AC voltage drives quantum mechanical tunneling of electrons across an ultrathin insulator (1-5 nm thick), producing a net DC current. Unlike Schottky or p-n junction diodes used at radio frequencies, MIM structures exploit field-induced tunneling, which operates without carrier diffusion delays and supports cutoff frequencies exceeding 100 THz, essential for visible light rectification. The diode's asymmetry, achieved via differences between metals or insulator doping, ensures nonlinear I-V characteristics for efficient half-wave or full-wave rectification. Operating at optical frequencies presents unique challenges, including the need for ultrafast response times on the order of femtoseconds to match the ~2.5 fs period of visible light oscillations, which MIM diodes address through tunneling but with limitations in quantum efficiency due to photon energies exceeding 1 eV for visible wavelengths. Thermal generation-recombination currents can mask the rectified signal, requiring low-temperature operation or advanced insulator engineering to enhance tunneling selectivity. Additionally, the nanoscale junction size imposes theoretical efficiency limits governed by the Landauer formalism for quantum transport conductance as quantized channels, where G=2e2hMG = \frac{2e^2}{h} M (with MM the number of modes) bounds the maximum current and thus rectification efficiency by ballistic transport and scattering losses. A key performance metric is the rectenna R=IDCPopticalR = \frac{I_\mathrm{DC}}{P_\mathrm{optical}}, where IDCI_\mathrm{DC} is the output DC current and PopticalP_\mathrm{optical} is the incident , ideally approaching the of one per but typically achieving values below 1% in demonstrated devices, such as 2.3 × 10^{-4}% at 1064 nm, due to decay and tunneling probabilities. Optical rectennas enable hot electron harvesting, where non-equilibrium "hot" electrons excited by plasmon decay are collected across the MIM barrier, circumventing the bandgap restrictions of traditional photovoltaics and allowing energy conversion from sub-bandgap photons. Broadband operation is facilitated by bowtie or dipole nanoantennas, whose tapered geometry supports a wide resonance bandwidth spanning visible to near-infrared spectra, enhancing capture efficiency over narrowband alternatives.

Design Challenges and Advances

One of the primary design challenges in optical rectennas stems from the need for nanofabrication precision at the sub-10 nm scale to create effective metal-insulator-metal (MIM) diodes and nanoantennas that resonate at optical frequencies. Achieving insulator thicknesses as thin as 0.7 nm, as demonstrated in prototypes using , is essential for tunneling rectification, but variations in layer uniformity can lead to inconsistent performance and increased series resistance. Additionally, losses arise from plasmonic absorption in metallic nanoantennas, where localized surface plasmons generate heat rather than directing energy to the rectifier, limiting overall efficiency in early devices to quantum yields below 1%. Recent advances in the have addressed these hurdles through material innovations and scalable fabrication techniques. For instance, planar-contact MIM (pc-MIM) diodes fabricated via milling have achieved rectification efficiencies of 2.3 × 10^{-4}% at 1064 nm, representing progress in and reduced . –oxide–metal diodes have demonstrated enhanced current density and asymmetry suitable for high-frequency rectification, though full rectenna efficiencies remain below 1%. Self-assembled (CNT) arrays, grown via , offer scalability by forming aligned antennas without complex lithography, mitigating disorder issues in traditional approaches. Key techniques include (EBL) for prototyping bowtie nanoantennas with 50 nm gaps, enabling field enhancements up to 4 × 10^4 at 28.3 THz, and integration with solar concentrators like wideband coherent to boost incident . Hybrid designs combining optical rectennas with , such as stacking MIM diodes atop cells, leverage complementary spectral responses for broader absorption. Theoretically, optical rectennas can surpass the 30% Shockley-Queisser limit of solar cells, with modeled efficiencies exceeding 80% under monochromatic illumination due to non-radiative recombination avoidance. In 2024, (IR) rectenna demonstrations using photon-assisted tunneling in Ag/SiO₂/n⁺-Si structures have shown promise for recovery, achieving zero-bias currents up to 13.93 mA/cm² across 400-2500 nm. As of 2025, ongoing research includes horizontally aligned CNT-based rectennas for selective IR detection.

Applications

Wireless Power Transmission

Wireless power transmission systems employing rectennas facilitate directed energy transfer over significant distances, typically using microwave frequencies for long-range applications. The core setup includes a transmitter equipped with a high-power microwave source, such as a magnetron for moderate power levels or a klystron for higher outputs, which generates and beams focused microwaves toward a large-scale rectenna array on the receiving end. The rectenna array captures the incoming radio-frequency energy and rectifies it into usable direct current electricity, often integrated with DC-DC converters for grid compatibility. A pivotal early demonstration of this technology occurred in 1975 at NASA's Goldstone Deep Space Communications Complex, where a system transmitted 34 kW of microwave power over 1.6 km, achieving an end-to-end DC-to-DC efficiency of 54% and a rectenna conversion efficiency exceeding 82%. Prominent applications of rectenna-based center on (SBSP) initiatives, where orbiting satellites equipped with photovoltaic arrays convert sunlight to and retransmit it via microwaves to terrestrial rectenna sites spanning several square kilometers. has explored SBSP concepts emphasizing scalable rectenna designs for efficient ground reception, while the (ESA) has prototyped rectenna systems to support beamed power from geostationary orbits, potentially delivering continuous baseload energy unaffected by weather or night cycles. Another key use case involves in-flight recharging of unmanned aerial vehicles (UAVs) or drones, where ground-based phased-array transmitters beam power to lightweight rectennas mounted on the aircraft, extending mission durations beyond battery limits without requiring landings. Operational constraints include adherence to safety standards, such as the U.S. Federal Communications Commission's (FCC) maximum of 10 W/m² for uncontrolled environments at frequencies above 1.5 GHz, ensuring minimal risks from beam exposure. Phased-array antennas enable transmission ranges of up to several kilometers by electronically and focusing the beam, minimizing spillover and supporting applications like drone swarms or remote powering. In 2025, reported advancements in its "Chasing Sun" project, including ground-based prototypes for components aimed at eventual GW-scale SBSP deployment by 2050, with initial orbital tests planned to validate rectenna integration at multi-megawatt levels. Significant challenges in these systems arise from atmospheric effects, notably attenuation at common operating frequencies of 2.45 GHz and 5.8 GHz, where , oxygen absorption, and —particularly —can cause losses of several dB per kilometer, reducing overall efficiency. Beam poses another hurdle, as natural spreading of the wavefront over distance necessitates precise control via adaptive phased arrays to maintain at the rectenna without excessive transmitter scaling.

Energy Harvesting and Sensing

Rectennas enable the harvesting of ambient radiofrequency (RF) energy from sources such as (2.4–2.5 GHz), cellular networks (0.9 GHz and 1.8 GHz), and television broadcasts (UHF bands), converting it into usable (DC) power for low-energy devices. Multi-band designs, often employing slot or patch antennas tuned to multiple frequencies, facilitate simultaneous capture across these spectra to maximize energy collection in urban environments where signal densities vary. For instance, a quad-band 3D rectenna array operating at 0.58 GHz, 0.92 GHz, 2.14 GHz, and 2.45 GHz achieves harvested powers suitable for (IoT) nodes, with outputs typically ranging from microwatts (μW) to milliwatts (mW) depending on ambient field strengths of 0.1–1 μW/cm². These systems prioritize broad angular coverage and compact form factors to integrate into distributed sensor networks without dedicated power sources. In sensing applications, rectennas power passive RFID tags through backscatter communication, where the tag modulates and reflects incident RF signals to transmit while harvesting via an integrated . This enables batteryless operation in scenarios like inventory tracking or identification, with rectenna efficiencies supporting activation thresholds as low as -20 dBm input power. For (SHM), batteryless sensors embedded in or composites use rectennas to harvest for strain or vibration detection, transmitting via low-power protocols like LoRaWAN. A prototypical SHM rectenna design incorporates far-field powering for sensing nodes, achieving reliable operation for acceleration and in civil infrastructure without batteries. Ultra-low-power rectifiers in these rectennas, often using Schottky diodes like HSMS-2850, deliver efficiencies below 10% at inputs around -20 dBm to accommodate weak ambient signals, with sensitivities reaching -44 dBm (0.00028 μW/cm²). In the 2020s, integrations with wearables for body-area networks have advanced, featuring flexible dual-band rectennas at 3.5 GHz and 4.9 GHz ( bands) that harvest energy from nearby devices, providing up to 53% efficiency at low inputs while maintaining performance under bending for conformal applications like monitoring patches. Enhancements include superstrate metalenses that boost antenna gain from 8 dBi to 19 dBi, increasing harvested power by focusing ambient waves. Hybrid systems pair rectennas with supercapacitors for , enabling burst-mode operation; for example, a multiband design at 0.9–2.45 GHz charges 100–200 mF supercapacitors to 8.3 V with up to 90% efficiency, supporting intermittent sensor duties in IoT wearables.

References

  1. https://www.cambridge.org/core/journals/mrs-energy-and-sustainability/article/rectenna-device-from-theory-to-practice-a-review/41348DB2BDD3706FA5B5A3161C3DF586
  2. https://ntrs.nasa.gov/api/citations/19940006885/downloads/19940006885.pdf
  3. https://www.nature.com/articles/s41598-025-09966-0
  4. https://ieeexplore.ieee.org/document/10915138/
  5. https://ieeexplore.ieee.org/document/9512378
  6. https://ntrs.nasa.gov/api/citations/19810008041/downloads/19810008041.pdf
  7. https://patents.google.com/patent/US3781647A/en
  8. https://ntrs.nasa.gov/api/citations/19760004119/downloads/19760004119.pdf
  9. https://phys.org/news/2015-09-optical-rectennacombined-rectifier-antennaconverts-dc.html
  10. https://pmc.ncbi.nlm.nih.gov/articles/PMC9982631/
  11. https://www.mdpi.com/1424-8220/24/21/6804
  12. https://www.researchgate.net/publication/303845511_Rectenna_Designs_for_RF_Energy_Harvesting_System_a_Review
  13. https://www.nature.com/articles/s41598-019-47606-6
  14. https://ieeexplore.ieee.org/document/7909632
  15. https://ntrs.nasa.gov/api/citations/19870010123/downloads/19870010123.pdf
  16. https://ieeexplore.ieee.org/document/7801010
  17. https://pmc.ncbi.nlm.nih.gov/articles/PMC10535291/
  18. https://www.nature.com/articles/s41598-018-33388-w
  19. https://pmc.ncbi.nlm.nih.gov/articles/PMC11548119/
  20. https://www.nature.com/articles/s41598-024-57639-1
  21. https://core.ac.uk/download/pdf/301206397.pdf
  22. https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/joe.2017.0095
  23. https://ims-ieee.org/sites/ims2019/files/content_images/SDC5%2520-%25203D-Printed%2520Rectennas%2520for%2520Energy%2520Harvesting%2520Applications.pdf
  24. https://www.sciencedirect.com/science/article/abs/pii/S143484112300290X
  25. https://pubs.aip.org/aip/acp/article-pdf/664/1/292/11552351/292_1_online.pdf
  26. https://www.sciencedirect.com/science/article/pii/S259012302502239X
  27. https://www.researchgate.net/publication/259175609_Design_of_a_Simple_Low-cost_Rectenna_for_Low_Power_RFID_Wireless_Power_Transmission_Applications
  28. https://www.politesi.polimi.it/retrieve/520727f9-c9c9-4cd3-ad53-e30acf323ab1/2024_07_Bhateja_Thesis_01.pdf
  29. https://www.intechopen.com/chapters/40344
  30. https://www.researchgate.net/publication/320838802_Broadband_bowtie_belt_nanoantennas
  31. https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/aenm.202103785
  32. https://onlinelibrary.wiley.com/doi/10.1155/2012/512379
  33. https://arxiv.org/pdf/2101.03085
  34. https://www.sciencedirect.com/science/article/abs/pii/S0038092X17307156
  35. https://www.nature.com/articles/srep04270
  36. https://repository.gatech.edu/bitstreams/67c2a0a0-8eb2-4a8c-8ec2-f309915df699/download
  37. https://physicsworld.com/a/efficient-optical-rectenna-could-generate-power-from-waste-heat/
  38. https://www.preprints.org/manuscript/202409.1932/v1/download
  39. https://onlinelibrary.wiley.com/doi/full/10.1002/aelm.201600223
  40. https://doi.org/10.1002/aenm.202103785
  41. https://opg.optica.org/abstract.cfm?URI=OSE-2013-RW1D.5
  42. https://www.mdpi.com/1996-1073/18/9/2372
  43. https://opg.optica.org/oe/fulltext.cfm?uri=oe-32-17-29587
  44. https://www.sciencedirect.com/science/article/pii/S2588842025001476
  45. https://ntrs.nasa.gov/citations/19760004119
  46. https://ieeexplore.ieee.org/document/6475357
  47. https://www.nasa.gov/wp-content/uploads/2024/01/otps-sbsp-report-final-tagged-approved-1-8-24-tagged-v2.pdf
  48. https://www.esa.int/ESA_Multimedia/Images/2022/08/Receiving_rectenna_on_the_ground
  49. https://aerocharge.co/rf-power-beaming-drones/
  50. https://www.scmp.com/news/china/science/article/3294091/china-plans-build-three-gorges-dam-space-harness-solar-power
  51. https://arxiv.org/pdf/1401.1779
  52. https://asp-eurasipjournals.springeropen.com/articles/10.1186/s13634-022-00846-7
  53. https://www.mdpi.com/2673-4591/112/1/48
  54. https://ieeexplore.ieee.org/document/11121182
  55. https://doi.org/10.1109/LAWP.2021.3095102
  56. https://www.researchgate.net/publication/4299153_Rectenna_Design_for_Passive_RFID_Transponders
  57. https://pubmed.ncbi.nlm.nih.gov/30301980/
  58. https://hal.science/hal-02919873v1/document
  59. https://www.researchgate.net/publication/340486293_An_Improved_Rectenna_Design_for_Battery-free_Wireless_Sensors_and_Structural_Health_Monitoring
  60. https://doi.org/10.3390/electronics14071314
  61. https://doi.org/10.1109/JIOT.2023.3328209
  62. https://doi.org/10.1016/j.heliyon.2023.e13964
Add your contribution
Related Hubs
User Avatar
No comments yet.