A SYSTEM AND METHOD FOR DESIGNING AN IMPROVED SWIPT ANTENNA FOR A RELAY NODE

Abstract

ABSTRACT Disclosed herein is a system and method for designing an improved simultaneous wireless information and power transfer antenna for a relay node. The system shown in FIG. 1 comprises plurality of antenna elements (101) arranged in a radially symmetric configuration on a substrate (200), a proximity-coupled WIT feed (201) for exciting the plurality of antenna elements (101), a reconfigurable feed network (202) integrated with the proximity-coupled WIT feed (201) for selectively switching between various combinations of antenna elements (101) to achieve reconfigurable pattern and polarization wireless information transfer, a full-wave rectification circuit integrated within each antenna element for harvesting RF energy from a dedicated RF energy transmitter (RF-Tx), a parallel DC combining circuit for combining the DC outputs of the full-wave rectification circuits and a circuit for frequency splitting technique and dual polarization configuration in order to achieve high isolation between the wireless information transfer and wireless power transfer signals.

Specification

Description:FIELD OF THE INVENTION:

[0001] The present invention generally relates to improved antenna systems for wireless communication. More particularly, the present invention relates to a system and method for designing an improved simultaneous wireless information and power transfer antenna (SWIPT) for a relay node in cooperative relay communication.

BACKGROUND:

[0002] Communication technology has witnessed extraordinary progress in recent years. Especially, 5G and beyond 5G (B5G) wireless communication has been the latest trend in the field of communication. For good communication, these wireless communication networks need to achieve energy-efficient green communication with high data rates and spectral efficiency. Also, there should be minimum losses in the network to achieve efficiency in communication. To reduce the adverse effects of path loss, signal fading, and enhance the coverage area and system capacity, the Cooperative Relaying (CoR) technique is utilized in communication networks. This technique extends the range, spectral efficiency, and system capacity of wireless communication.

[0003] To achieve a highly reliable and efficient CoR, the antenna system in a communication network at energy-constrained Relay Nodes (RN) should provide a wider coverage area with the capability to replenish its battery. The relay nodes in CoR receive a communication signal from the transmitter and forward the signal to the designated receiver after processing. In general, a relay node either performs amplify and forward (AF) or decode and forward (DF) operation on the signal received from the transmitter or receiver. To realize energy-efficient green communication wireless power transfer (WPT) and simultaneous information and power transfer (SWIPT) have emerged as promising techniques to recharge battery-assisted relay nodes (RNs) in IoT applications.

[0004] Researchers have extensively studied SWIPT-enabled RNs from a theoretical perspective to achieve sustainable CoR communication for IoT applications. Time Splitting (TS), power Splitting (PS), and Antenna Switching (AS) techniques were considered for integrated receiver architecture to realize a realistic SWIPT system. Significant attention is also given to maximizing the data rate by optimizing the power and time interval allocation for information and power transfer. Moreover, relay selection is investigated in multi-relay IoT systems based on leftover power and power splitting ratio. Further, the reliability of ultra-reliable low-latency communication is analyzed by optimizing various design parameters of TS and PS schemes.

[0005] There are many prior art relating to systems and methods for simultaneous wireless information and power transfer. For example, a non-patent literature reference entitled "Highly-Isolated RF Power and Information Receiving System Based on Dual-Band Dual-Circular-Polarized Shared-Aperture Antenna" to Jun-Hui Ou et. al., relates to a highly integrated RF power and information receiving system. The system comprises of an antenna, a rectifier, and an information receiving module. The information receiving module acts as part of the dc load. The antenna used is a dual-band, dual-circular-polarized shared- aperture antenna and it is implemented for realizing high integration.

[0006] United States Patent Number 11322978 entitled "Reconfigurable heterogeneous energy harvester for SWIPT receiver and method of energy harvester reconfiguration" to Dong In Kim et. al., relates to a method of energy harvester reconfiguration. The method comprises the steps of receiving an input power from an RF signal, determining whether a Nblock-th energy block is activated based on a condition for operating the Nblock-th energy block having a maximum valid input power, in response to the Nblock-th energy block being determined activated, determining a number of energy harvesting circuits that are activated and reconfiguring power input in the Nblock-th energy block and the plurality of energy harvesting circuits included in the Nblock-th energy block, based on the determination and result of determination.

[0007] Though there are many prior art relating to systems and methods for SWIPT, none of them disclose the design of antenna system for effectively performing SWIPT. Also, the existing solutions are only limited to theoretical analysis without any experimental validation. There are also several SWIPT antenna systems which have been proposed for practical implementation. However, only a few works have evaluated the performance of the system in terms of signal-to-noise ratio (SNR), bit error rate (BER), and power conversion efficiency (PCE) without considering any practical application scenario. This has made the necessity to design a SWIPT antenna array system for RNs to realize realistic CoR communication.

OBJECTIVES OF THE INVENTION:

[0008] The primary objective of the present invention is to provide an improved simultaneous wireless information and power transfer antenna system for a relay node that can efficiently and reliably transmit and receive data while simultaneously harvesting ambient RF energy.

[0009] Another objective of the present invention is to provide a method for designing an improved simultaneous wireless information and power transfer antenna for a relay node.

[0010] Yet another objective of the present invention is to provide a method for determining the isolation between the information and power signal in a conjugate-matched design.

[0011] Still another objective of the present invention is to achieve reconfigurable pattern and polarization wireless information transfer (WIT) to improve communication link quality and mitigate the effects of polarization mismatch and signal fading.

[0012] Still another objective of the present invention is to enhance active WPT coverage by exploiting the WIT port of the antenna array.





SUMMARY:

[0013] The present invention discloses a system and method for designing an improved simultaneous wireless information and power transfer antenna for a relay node.

[0014] According to the present invention, the system comprises of plurality of antenna elements arranged in a radially symmetric configuration on a substrate, a proximity-coupled WIT feed for exciting the plurality of antenna elements, a reconfigurable feed network integrated with the proximity-coupled WIT feed for selectively switching between various combinations of antenna elements to achieve reconfigurable pattern and polarization wireless information transfer, a full-wave rectification circuit integrated within each antenna element for harvesting RF energy from a dedicated RF energy transmitter (RF-Tx), a parallel DC combining circuit for combining the DC outputs of the full-wave rectification circuits; and a circuit for frequency splitting technique and dual polarization configuration in order to achieve high isolation between the wireless information transfer and wireless power transfer signals.

[0015] In accordance with the present invention, the method comprises the steps of arranging plurality of antenna elements in a radially symmetric configuration on a substrate, incorporating a proximity-coupled WIT feed in the substrate for exciting the plurality of antenna elements, integrating a reconfigurable feed network with the proximity-coupled WIT feed for selectively switching between various combinations of antenna elements to achieve reconfigurable pattern and polarization wireless information transfer; integrating a full-wave rectification circuit within each antenna element for harvesting RF energy from a dedicated RF energy transmitter (RF-Tx), integrating a parallel DC combining circuit for combining the DC outputs of the full-wave rectification circuits and integrating a circuit for frequency splitting and dual polarization configuration to achieve high isolation between the wireless information transfer and wireless power transfer signals.

[0016] In the present invention, the antenna harvests the incident RF energy and utilizes the generated DC power to replenish its battery for sustainable operation. The present invention also has the feature to parallel combine the harvested DC power from each antenna element within the system. The sequentially rotated design feature enables the polarization misalignment tolerant WPT operation and, in collaboration with the reconfigurable feed network, provides polarization and pattern reconfigurable radiation patterns for WIT.

[0017] To summarize, the present invention provides a novel, completely integrated antenna design utilizing conjugate impedance matching and parallel DC combining circuits to reduce circuit losses and implement the full wave rectification of the incident ultra-low power RF waves with enhanced power conversion efficiency.

[0018] Also, the present invention achieves reconfigurable pattern and polarization wireless information transfer (WIT) to improve communication link quality and mitigate the effects of polarization mismatch and signal fading. This enhance active WPT coverage by exploiting the WIT port of the antenna array.

[0019] These objectives and advantages of the present invention will become more evident from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0020] The objective of the present invention will now be described in more detail with reference to the accompanying drawing, wherein:

FIG. 1 shows the complete design layout of the SWIPT antenna array disclosed in the present invention;

FIG. 2A and 2B shows the design layout of the top layer of the SWIPT antenna array disclosed in the present invention;

FIG. 2C shows the bottom layer of the SWIPT antenna array disclosed in the present invention;

FIG. 2D shows the middle layer of the SWIPT antenna array disclosed in the present invention;

FIGS. 3A and 3B shows the equivalent circuit diagram of an SWIPT antenna element (SAE) in the disclosed SWIPT antenna array (SAA) for WPT operation and Parallel DC combining of ??????1-4 respectively;

FIGS. 4A and 4B shows the reflection coefficient of the various WIT modes of the disclosed SWIPT antenna array;

FIG. 5 shows the 3D WIT radiation patterns in A1, B1, C1, D1 and E1 modes at edge frequencies of 5 GHz WiFi band;

FIG. 6 shows the application scenario for the disclosed SWIPT antenna array;

FIG. 7 shows the experimental setup for WPT performance measurement;

FIGS. 8A, 8B and 8C show the normalized DC patterns of the proposed SWIPT antenna array in (a) ?? = 00, (b) ?? = 900, and (c) ?? = 450 plane;

FIGS. 9A and 9B show the percentage PCE and output voltage versus output load and input RF power respectively; and

FIG. 10 shows the fabricated prototype of the disclosed SWIPT antenna array.




REFERENCE NUMERALS:

101 - Circular Patch Antenna
102, 207 - WPT Feed
103 - Inductor Connection
104 - Low Pass Filter
105 - Shorting Via to DC Connection Line
106 - Top Substrate
200 - Bottom Substrate
201 - WIT Feed
202 - Reconfigurable Feed Network
203 - Reconfigurable Circuit for a Single Element
204 - DC Biasing Lines
205 - Antenna Feed Point
206 - Schottky Diode
208 - DC Connection Line
209 - DC Output Terminals
300 - Ground

DETAILED DESCRIPTION OF THE INVENTION:

[0021] The present invention discloses a system and method for designing an improved simultaneous wireless information and power transfer antenna for a relay node. The present invention for enhances energy efficiency and sustainability of a cooperative communication network using battery-assisted relay nodes.

[0022] According to the present invention, the system comprises of plurality of antenna elements arranged in a radially symmetric configuration on a substrate, a proximity-coupled WIT feed for exciting the plurality of antenna elements, a reconfigurable feed network integrated with the proximity-coupled WIT feed for selectively switching between various combinations of antenna elements to achieve reconfigurable pattern and polarization wireless information transfer, a full-wave rectification circuit integrated within each antenna element for harvesting RF energy from a dedicated RF energy transmitter (RF-Tx), a parallel DC combining circuit for combining the DC outputs of the full-wave rectification circuits and a circuit for frequency splitting technique and dual polarization configuration in order to achieve high isolation between the wireless information transfer and wireless power transfer signals.

[0023] In accordance with the present invention, the method comprises the steps of arranging plurality of antenna elements in a radially symmetric configuration on a substrate, incorporating a proximity-coupled WIT feed in the substrate for exciting the plurality of antenna elements, integrating a reconfigurable feed network with the proximity-coupled WIT feed for selectively switching between various combinations of antenna elements to achieve reconfigurable pattern and polarization wireless information transfer; integrating a full-wave rectification circuit within each antenna element for harvesting RF energy from a dedicated RF energy transmitter (RF-Tx), integrating a parallel DC combining circuit for combining the DC outputs of the full-wave rectification circuits and integrating a circuit for frequency splitting and dual polarization configuration to achieve high isolation between the wireless information transfer and wireless power transfer signals.

[0024] The present invention discloses a 2×2 simultaneous wireless information and power transfer SAA for the relay node. The antenna array comprises four antenna elements which are excited using a reconfigurable feed network (RFN) to achieve pattern reconfigurable wireless information transfer (WIT) in the 5 GHz WiFi band (5.15 GHz - 5.825 GHz). To realize polarization reconfigurability, the antenna elements within the array are excited such that the adjacent have a spatial phase difference of 90o. Further, the WPT operation is implemented at 5 GHz, utilizing a completely integrated conjugate impedance-matched full wave rectification circuit. Moreover, the DC outputs of all four SWIPT antenna elements are combined in parallel to enhance the overall harvested DC power with negligible circuit losses.

In the present invention, the SWIPT antenna array has the following features:

• A battery-assisted relay node in cooperative communication
• Pattern and polarization reconfigurable WIT operation with a wide beam coverage for WPT in the boresight direction suitable for a multipath environment.
• Integrated rectification and parallel DC combining circuit within each element for realizing full waver rectification under ultra-lower input RF power (<= -10 dBm) conditions
• A hybrid design technique utilizing both Frequency Splitting and Dual Polarisation to achieve high isolation between the WIT and WPT signals
• A measurement technique to validate the simulated isolation measurement results between WIT and WPT signals for integrated SWIPT antenna design
• Capability to achieve both passive and active WPT. The passive WPT operation is achieved through the designed integrated full wave rectifier circuit within each antenna element. On the other hand, active WPT is achieved for any WIT radiation mode by activating the required p-i-n diodes and connecting the WIT port to a non-symmetric hybrid coupler utilizing the power splitting technique for SWIPT operation

The detailed working of the present invention is explained below:

The complete design layout of the SWIPT antenna array disclosed in the present invention is shown in FIG. 1.

WIT Design Configuration:

[0025] The array comprises of four SWIPT antenna elements (??????1-4) which are excited by a proximity-coupled WIT feed as shown in FIGS. 2A and 2B.

[0026] The SAEs are arranged radially such that each adjacent pair of SAEs has a spatial phase difference (????????) of 900. Moreover, the corresponding WIT feeds (201) are integrated with a reconfigurable feed network (RFN) (202) for switching between various combinations of excited SAEs. The fusion of ???????? with RFN gives rise to fifteen different modes of operation. This enables the realization of pattern, polarization, and spatial diversity for WIT, which consequently helps in improving the communication link quality. The various design features and circuit components utilized in the RFN are outlined in FIGS. 2A and 2B respectively.

[0027] The RFN comprises a center coaxial feed that excites four reconfigurable feed lines (??????1-4), each feeding an SAE. The RFL comprises of two P-i-N diodes (SMP1345-079LF) (depicted as ??1,2) to enable switching between different modes of operation, and two microstrip feed lines (????1-2) to achieve necessary impedance matching. The P-i-N didoes are biased using a DC biasing circuit (204) consisting of two inductors (??2,3 = 5.1????), two capacitors (??2,3 = 100????), and two DC biasing lines (204) for connecting DC supply through terminals ??1 and ??2. The ?? and ?? pairs (??2, ??2) and (??3, ??3) are connected to DC terminals ??1 and ??2, respectively to provide necessary lowpass filter operation for isolating RF signal from the biasing circuit. In addition, the coaxial feed is connected to each RFL through a DC blocking capacitor (??1 = 1????) for isolating the center feed from the biasing circuit. The RFL is configured to work either in high-impedance or SAE excitation mode by switching the P-i-N diode state. It acts as a high impedance line when ??1 is ON and ??2 is OFF. This is achieved by connecting ??1 to the positive terminal of the DC supply and shorting (105) ??2 to the ground. It can be switched to SAE excitation mode by swapping ??1 and ??2 terminals, which changes the state of ??1 to OFF and ??2 to ON state. The P-i-N diode is equivalent to a 1.5O during the ON state and acts as 0.2???? in the OFF state. Since each RFL has two states, a total of 16 modes are possible, one being an idle mode where no SAE is excited resulting in a total of 15 radiation modes.

WPT Design Configuration:

[0028] The various WPT design features of the disclosed SAA are shown in FIGS. 2B and 2C respectively.

[0029] The RF power incident over the circular patch (101) within an SAE is extracted using two copolarized capacitively coupled WPT feeds (102, 207). The input impedance (?????? = ???? + ?????? O) at corresponding WPT feeds (102, 207) are conjugate matched with the shunt Schottky diode (SMS7630079LF) (206) impedance (???? = ???? - ?????? O) for maximum RF power transfer from the circular patch (101) and reduce insertion losses. Moreover, the harvested DC backflow into the patch is blocked by the capacitive coupling, eventually enhancing the PCE of the WPT operation. The equivalent circuit diagram of an SAE for the WPT function is shown in FIG. 3A. The RF wave incident over the circular patch (101) excites ????110 mode current which alters its polarity in every half cycle. The two RF sources ????1 and ????2 represent respective half cycles of the incident RF wave, exciting respective shunt Schottky Diodes (206) ??????1 and ??????2, realizing FWR of captured RF energy. The ???? and ???? denote parasitic packaging parameters of the Schottky diode (206), ????1,2 represents the impedance of the antenna and ???? depicts the capacitive coupling between the antenna and WPT feed (102, 207). Moreover, an inductor ??1 = 1.5???? along with a stepped high impedance line acting as a low pass filter (104) is utilized as a choke to impede RF signal flow through DC load. The DC output terminals (209) from each SAEs are connected in parallel as shown in FIG. 3B, enhancing the total harvested output DC power with negligible combining losses.

[0030] The radially opposite pairs of SAEs (??????1, ??????3) and (??????2, ??????4) are vertically (?? = 900) and horizontally (?? = 00) polarized, respectively. Hence, the disclosed SAA has dual-linear polarized WPT capability, providing tolerance for angular and polarization misalignment with the RF-Tx.

[0031] The simulation and measurement for the present invention is conducted in the lab and the respective results are presented. The disclosed antenna system is designed in Ansys HFSS on an FR4 substrate (200) (???? = 4.4, ???????? = 0.02) having 1.6 mm thickness and 1 oz copper deposit. The Keysight Advanced Design System (ADS) software is used for the analysis of the rectifier circuit. The geometrical dimensions of the disclosed antenna are recorded in Table 1.




Circuit and Design Simulation Setup:

[0032] The harmonic balance and large signal s-parameter technique in Advanced Design System (ADS) software is used for the analysis of the non-linear rectifier circuit. The SPICE parameters of the Schottky diode (206) enabled the modeling by accounting for the parasitic packaging parameters ???? = 0.7???? and ?? = 0.16????. The analysis is done for an input RF power of -10 dBm at 5GHz frequency and 1??O output load, resulting in the Schottky diode (206) impedance of ???? = 46 - ??115. The disclosed SAA is optimized in Ansys HFSS with WPT port impedance matched to ????* and achieved WIT impedance matching in 5 GHz WiFi band.

[0033] In an embodiment, the Effective Isotropic Radiated Power (EIRP) is less than or equal to 36 dBm.

[0034] In one embodiment, the WIT frequency range is but not limited to 5 GHz WiFi band (5.15 GHz - 5.35 GHz, 5.725 GHz - 5.825 GHz.

[0035] In another embodiment, the WPT frequency range is but not limited to 5 GHz for passive WPT and 5 GHz WiFi band for active WPT

[0036] In a preferred embodiment, the output DC power and power conversion efficiency is measured using an anechoic chamber, Tx horn antenna, multimeter, and signal generator.

[0037] In a preferred embodiment, the impedance matching of the WIT port used for measuring is Vector Network Analyzer (VNA).


Impedance Matching and Radiation Characteristics:

[0038] WIT Impedance Matching:

[0039] The disclosed SAA is capable of generating 15 WIT radiation modes depending upon the excitation state of the four RFLs. The various modes are segregated into five groups (A to E) based on the numbers and relative position of excited SAEs. The single SAE excitation is represented by A1-A4, B1-B4 (C1-C2) denoting two adjacent (opposite) elements, three-element excitation is indicated by D1-D4 and E1 designates excitation of all four elements. The detailed description of SAEs excited in each mode is presented in Table 1, where (v) and (×) represent the excited and non-excited state of the SAE, respectively. The simulated and measured reflection coefficient (??11) results for all the modes are plotted in FIGS. 4A and 4B respectively. The results demonstrate impedance matching in the entire 5 GHz WiFi band for all the radiation modes, confirming the wide band WIT capability of the design. Further, the isolation between the WIT and WPT ports is >=20 dB for all the WIT radiation modes in the entire 5 GHz WiFi band.

WIT Radiation Characteristics:

[0040] The simulated WIT 3-D radiation patterns at the edge frequencies of the 5 GHz WiFi band (5.15 GHz, 5.35 GHz, 5.725 GHz, and 5.825 GHz) are plotted in FIG. 5 for the 1???? mode of each radiation group (A-E). In addition, the corresponding max gain, its direction (??, ??), and HPBW of the 2D pattern comprising the max gain are listed in Table 2. The results show maximum gain variation at each frequency (??) across all the modes and maximum gain variation for each mode in the entire frequency band. In A1 and B1 modes SAA radiates in the boresight direction with a small average elevation tilt angle of ?? = 8o and 2o, respectively. The ?? coverage with variation in ?? is uniform in the case of B1 whereas Gaussian pulse type variation in ?? is observed for A1 with ??. For other remaining modes, SAA radiates its main beam at a larger elevation tilt angle direction with non-uniform ?? coverage with ??. The C1 mode generates two radiation peaks at an average tilt angle of ?? = 23.5o with 27.5o average HPBW with polarization along ?? = 0o plane. Similarly, the D1 mode emanates radiation at an average elevation tilt angle of 22.5o with 34.5o HPBW in the boresight direction. The E1 mode enhances the elevation tilt of the radiation pattern to 31o having a null along broadside direction with a wider HPBW of 47o. The radiation patterns for other modes in each group are 90o shifted in ?? plane from the previous mode due to symmetry in the SAA design along the azimuth plane, providing pattern and polarization diverse WIT.




[0041] The disclosed SWIPT antenna array (SAA) has wide impedance bandwidth, providing WIT operation in both the lower (5.15GHz - 5.35GHz) and upper (5.725GHz-5.825GHz) 5GHz WiFi band. The radiation pattern of the antenna array is reconfigured in the entire WIT band to achieve the desired wide beam coverage in the application region. In addition, the RF power is harvested by each antenna element at 5GHz through a directly integrated conjugate-matched FWR circuit. The DC outputs from each antenna element within the array are connected in parallel to enhance the output power with negligible combining losses. In addition, large isolation between the WIT and WPT is highly desirable since the information signal can leak into the antenna circuit, reducing the strength of the received and transmitted WIT signal. To enhance the desired isolation, FS along with orthogonally polarized feeds are utilized for WIT and WPT signals. A typical application scenario where the disclosed SAA is deployed is shown in FIG. 6, demonstrating multiple SWIPT-enabled RNs equipped with multiple antennas having beam patterns to process data received from the transmitter and forward it to the receiver or vice-versa. In such a scenario to achieve robust communication link RNs with zero information error is activated for relaying the information whereas the ones with errors are only allowed to harvest RF energy to recharge their batteries.

WPT DC Patterns:

[0042] The simulated DC patterns of each antenna element in the SAA along with the measured DC pattern are measured using the experimental setup shown in Fig. 7. The SWIPT antenna array is incident with RF power using a 10 dBi gain horn antenna fed with a 25 dBm input RF power using a signal generator. The output DC voltage across the output load is then measured using a digital multimeter. The measurement results are plotted in FIG. 7 for ?? = 00, 900, and 450 plane. The results indicate that the measured DC pattern is close to the sum of the DC patterns of each element. Moreover, the disclosed antenna array has a wide angular coverage in the boresight direction making it usable in a multipath environment. The power conversion efficiency (PCE) of the proposed SAA for ?? = 00, 900, and 450 orientation of the RF Transmitter with respect to the SAA. The results in FIG. 8A indicate the highest PCE (59% at 300 O) for ?? = 00 and the lowest (33.25% at 225 O) for ?? = 450. The variation of PCE with input RF power is shown in FIG. 8B, illustrating a non-linear increase in PCE and output DC voltage which is due to the non-linear characteristic of the Schottky diode (206). Moreover, by utilizing the power splitting technique (the WIT port can also be connected to the non-symmetrical hybrid coupler for WPT) at the WIT port, WPT is also be implemented in the 5 GHz WiFi band with a wide reconfigurable beam coverage. This is more beneficial when the relay node is idle and not performing any data communication.

[0043] The percentage PCE and output voltage versus output load and input RF power is shown in FIGS. 9A and 9B respectively.

[0044] The disclosed antenna design is first simulated to determine the radiation characteristics of the array for different switching conditions. Moreover, the Keysight ADS tool is used to determine the rectifier circuit impedance. The design is optimized in Ansys HFSS to achieve conjugate impedance matching between the WPT port and the rectifier impedance. After achieving the desired performance in the simulation tool, the SWIPT antenna array shown in FIG. 10 is fabricated at AMR LAB IIT Ropar using the MITS PCB prototyping matching. The WPT performance of the design is measured in the anechoic chamber using the experimental setup shown in FIG. 7. However, due to equipment constraints in the anechoic chamber, WIT measurements are not possible.

[0045] In one embodiment, the simulation tool is Ansys HFSS simulation tool.

A detailed description of the problems addressed by the present invention is given below:

• Pattern and Polarization Reconfigurable WIT: The received signal (WIT as well as WPT signal) at the relay node can have any polarization, reducing the received signal strength due to polarization mismatch. In addition, the signal is received at any angle from the boresight direction, demanding the requirement of wide beam coverage. To mitigate the polarization mismatch problem with a wide beam coverage the present invention discloses a realistic SWIPT antenna array system. In addition to antenna switching (AS), the antenna elements within the array are radially arranged such that the adjacent elements have a spatial phase difference of 900. This enables the transfer of WIT signals having reconfigurable radiation patterns with different polarizations. The WPT signals received by the opposite elements are in the same phase whereas the adjacent antenna elements have an orthogonal phase, which allows orientation-tolerant WPT operation.

• Integrated full wave rectification at ultra-low input RF power with wider beam coverage for passive WPT: In the existing SWIPT antenna designs impedance-matching circuit between the antenna and the rectifier circuit is utilized which increases the insertion losses. Moreover, the existing antenna systems are designed for high input RF-received power (= -3 ??????). In contrast, the present invention discloses an integrated rectifier circuit in each antenna element capable of harvesting both the half cycles of the incident ultra-low power (-10 ??????) RF waves. The DC outputs of each element are further connected in parallel which increases the total harvested power with negligible circuit losses, thus enhancing the power conversion efficiency. In addition, the presented array structure provides inherent tilt in the radiation pattern of each antenna element along both the ?? = 00 and ?? = 1800 elevation plane, increasing the beam coverage for WPT which is an essential requirement in a multipath environment.

• High Isolation between the WIT and WPT signal: It is required to avoid WIT signal leakage into the WPT circuit. The leakage reduces signal strength, resulting in a low signal-to-noise ratio, which degrades communication link quality. However, achieving high isolation (= 20 ????) in an integrated design is difficult. To overcome this problem a hybrid design technique utilizing both the frequency splitting (FS) and dual polarization (DP) is implemented in the antenna system. In addition, an integrated low pass filter is incorporated as part of the parallel DC combining circuit to implement the full wave rectification within each antenna element.

• Isolation Measurement Technique: Measuring the isolation between the WIT and WPT signals is difficult in integrated design. Hence, in the present invention, the open DC voltage is measured first at various frequencies when the RF power of -10?????? is incident on the antenna aperture from an RF transmitter. In the second step, the WIT port is connected to the RF source, and the input power (?????? ??????) is adjusted such that the open DC voltage across the output DC terminals is equal to the one measured in the first step. The Isolation is (?????? + 10).

• Enhanced active WPT Coverage by exploiting WIT port: The WIT port in the disclosed antenna system is also connected to a non-symmetrical hybrid coupler, whose high output power port can be connected to a rectifier working in the 5 GHz WiFi band. This is beneficial when the relay node is idle and not performing any data communication task.

In the present invention, a single element is used for WPT as well as WIT operation. Also, the present invention discloses the design which is tailor made for ultra-low power IoT devices with received input RF power of around -10 dBm. Further, the present invention does not utilize any metasurface.

The advantages of the present invention are listed, but not limited to:

• The existing state-of-the-art SWIPT antennas have broadside radiation patterns which is not suitable for relay node operation. Whereas, the present SWIPT antenna design achieve 15 different radiation modes with different polarization and radiation patterns. This enable the relay node to work efficiently in a multi-path fading environment. Moreover, it enables the relay node to communicate simultaneously with the access point and the receiver at the user equipment.

• The disclosed SWIPT antenna design incorporates a completely integrated rectifier circuit capable of full wave rectification of the incident ultra-low power RF waves (received RF power approximately -10 dBm) with a higher power conversion efficiency than the existing designs in the literature.


• The present invention utilizes the parallel DC combining strategy to enhance the angular coverage of the RF energy harvesting which is beneficial in a multipath and distributed RF energy transmitter application scenario.

• The present invention also discloses a measurement scheme to determine the isolation between the information and power signal in a conjugate-matched design. The conjugate-matched antenna design refers to conjugate impedance matching between the antenna and the WPT feed line.


• A hybrid design technique utilizing both Frequency Splitting and Dual Polarization along with a parallel integrated DC combining network implemented using a conjugate matched rectifier circuit to facilitate full wave rectification of the incident RF waves and achieve high isolation between the WIT and WPT signals

• The capability to achieve both passive and active WPT. The passive WPT operation is achieved through the designed integrated full wave rectifier circuit within each antenna element. On the other hand, active WPT is achieved for any WIT radiation mode by activating the required p-i-n diodes and connecting the WIT port to a non-symmetric hybrid coupler utilizing the power splitting technique for SWIPT operation.

[0046] While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope of the invention as claimed.
, Claims:I / WE CLAIM:

1. A simultaneous wireless information and power transfer (SWIPT) antenna system having reconfigurable pattern and polarization wireless information transfer (WIT) for a relay node in a cooperative communication system, wherein the system comprises of:
a. plurality of antenna elements (101) arranged in a radially symmetric configuration on a substrate (200);
b. a proximity-coupled WIT feed (201) for exciting the plurality of antenna elements; (101);
c. a reconfigurable feed network (202) integrated with the proximity-coupled WIT feed (201) for selectively switching between various combinations of antenna elements (101) to achieve reconfigurable pattern and polarization wireless information transfer;
d. a full-wave rectification circuit integrated within each antenna element for harvesting RF energy from a dedicated RF energy transmitter (RF-Tx);
e. a parallel DC combining circuit for combining the DC outputs of the full-wave rectification circuits; and
f. a circuit for frequency splitting and dual polarization configuration to achieve high isolation between the wireless information transfer and wireless power transfer signals.

2. The system as claimed in claim 1, wherein SWIPT antenna elements (101) have a spatial phase difference of 90 degrees.

3. The system as claimed in claim 1, wherein the reconfigurable feed network (202) comprises a center coaxial feed that excites plurality of reconfigurable feed lines feeding a SWIPT antenna element (101).

4. The system as claimed in claim 1, wherein the system further comprising a hybrid coupler coupled to the antenna array for enabling active wireless power transfer.

5. A method for designing a simultaneous wireless information and power transfer (SWIPT) antenna system having reconfigurable pattern and polarization wireless information transfer (WIT) for a relay node in a cooperative communication system, comprises the steps of:
a. arranging plurality of antenna elements in a radially symmetric configuration on a substrate;
b. incorporating a proximity-coupled WIT feed in the substrate for exciting the plurality of antenna elements;
c. integrating a reconfigurable feed network with the proximity-coupled WIT feed for selectively switching between various combinations of antenna elements to achieve reconfigurable pattern and polarization wireless information transfer;
d. integrating a full-wave rectification circuit within each antenna element for harvesting RF energy from a dedicated RF energy transmitter (RF-Tx);
e. integrating a parallel DC combining circuit for combining the DC outputs of the full-wave rectification circuits; and
f. integrating a circuit for frequency splitting and dual polarization configuration to achieve high isolation between the wireless information transfer and wireless power transfer signals.

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