A low profile 916 MHz F-inverted compact antenna (FICA) for wireless sensor networks

Abstract

IntroductionThe antenna size is one of the major limitations in miniaturizing wireless communication equipment. Chip antennas and planar inverted F antennas (PIFAs) already appeared on the market due to their low profile, small size, and effective integration with transceiver chips on circuit boards [1]- [3]. However, these antennas perform well only if a ground plane of proper size is provided. This is because the ground plane acts as an effective radiating structure at the desired communication frequency. Generally, one or more sides of the ground plane must be about λ/4 long. At 900 MHz, this length is 83 mm. Although it is acceptable for cell phone technology application, this size is impractical in low power wireless sensor networks (WSN), where the maximum size of the communication node is limited to 1cm to 3cm [3]. This is especially true for low frequency (433 MHz) applications, where the wave length (λ≈70 cm) is large. In addition, in order to maximize the battery life, the total power consumption of a communication module is about 1 mW. It is essential that the antenna be very efficient if the power available is limited. Fortunately, in contrast to cell phone systems, WSN technology requires only a few meters of communication range. Therefore, in this paper we aim at designing electrically small antennas by carefully balancing the trade offs in terms of communication distance, stringent geometrical size limits, bandwidth, and antenna efficiency.In this paper, a novel low profile F-inverted compact antenna (FICA) is presented. A prototype dielectric loaded FICA has been built and measured through the communication range of custom-integrated application-specific WSN elements at 916 MHz. The design is low profile, small volume and is suitable for WSN. The results presented in this paper indicate a promising potential for the effective use of the novel FICA in WSN where 3-dimensional integration and size reduction are top requirements. Dielectric Loaded FICA Antenna Guidelines and DesignsSeveral fundamental limitations of electrically small antenna [4] must be explored to guide their design. First, the radiation resistance (Rr) decreases with the square of the height of the antenna. For example, the typical radiation resistance of an antenna with a height of λ/20 above a ground plane is only a fraction of an ohm. 5419 1-4244-0878-4/07/$20.00 ©2007 IEEE Without a proper matching network, transferring power into and from a standard 50 Ω port becomes practically impossible. Given this limitation, maximizing the possible height of the antenna proves to be critical for achieving proper power transfer in small antenna design.The small size of an antenna not only limits the radiation resistance (Rr), but also increases the capacitive input reactance, and a large inductive tuning reactance (L) is needed to bring the resonance frequency to the desired value. The quality factor can be expressed as Q = ωL/Rr, where ω is the resonance frequency. With a large L and a small Rr, Q is large, indicating a narrow bandwidth f...

Integration of small antennas for ultra small nodes in wireless sensor networks

“…The antenna is carefully tuned at 916 MHz. The details of the design strategies of the FICA can be found in our previous works [2]. To further optimize the performance of the FICA, we have modified the loop shape.…”

Compact, Low Power Wireless Sensor Network System for Line Crossing Recognition

“…To implement the complete wireless sensor network systembased on the algorithms and protocols discussed in the previous sections -we have developed a streamlined, miniaturized antenna [10], and employed an emerging family of system-on-chip (SoC) devices [8] as an integrated, single-chip device for performing computation and communication tasks as well as a acoustic sensor for sensing tasks. The PCB design of our sensor node prototype includes a 4-layer layout, and provides placement of components for minimizing the board size and enhancing antenna performance.…”

Τεχνολογίες Ενεργειακά Αποδοτικών Ευρυζωνικών Και Συμπαγών Κεραιοσυστημάτων Υψηλών Συχνοτήτων Για Κινητά Τερματικά Και Προηγμένα Ασύρματα Δίκτυα Επικοινωνιών

“…Οι επόμενες πρόσφατες μελέτες δεν αφορούν σε τυπωμένες ή επίπεδες IFAs υπό τη στενή έννοια, αλλά σίγουρα ανήκουν στη βιβλιογραφία των κεραιών για μικρο-αισθητήρες [83,148,315,316]. Οι Yang et al [83,315,316] περιέγραψαν την εφαρμογή νηματοειδούς 3-D IFA σε κόμβους WSN στα 916 MHz. Η κεραία είχε ελικοειδές ανοιχτοκυκλωμένο στέλεχος και ήταν διηλεκτρικά φορτισμένη με κεραμικό μπλοκ.…”

“…Παρ΄ όλα αυτά, η συγκεκριμένη στρατηγική σχεδίασης οδήγησε σε μια κεραία που είναι υπερβολικά επιμήκης για να ενσωματωθεί σε κόμβους αισθητήρων: η μέγιστη διάσταση των κόμβων συχνά περιορίζεται μεταξύ 10 και 30 mm [83,315,316]. Η διζωνική PIFA μεγέθους 24 mm×6.4 mm [300,301] και σε πολύ μεγαλύτερο βαθμό στα δίκτυα αισθητήρων.…”

“…Με βάση τα αποτελέσματα των Σχημάτων 6.8 και 6.9, ο ισχυρισμός των Tan & Erricolo είναι τελείως αβάσιμος. Το στέλεχος τροφοδοσίας των PIFAs συνεισφέρει σημαντικά στην ακτινοβολία με το ισχυρό συντονιζόμενο ρεύμα του, γι΄ αυτό και ο σχεδιαστής πρέπει να επιλέγει προσεκτικά το πλάτος αυτού του αγωγού.Στην περιγραφή της F-inverted compact antenna (FICA), οι Yang et al[83,315,316] παρουσίασαν αποτελέσματα Η/Μ προσομοιώσεων που έδειχναν ότι οι ρευματικές υπο-κατανομές των στελεχών τροφοδοσίας και βραχυκύκλωσης βρίσκονται σε φάση, άρα και τα δύο στελέχη είναι αποδοτικά ακτινοβολούντα τμήματα της κεραίας. Η διαφορά φάσης ανάμεσα στα ρεύματα των δύο στελεχών είναι σημαντικό ζήτημα, λόγω της εγγύτητας των δύο αγωγών, οπότε εξετάστηκε περαιτέρω.…”