Single fed low profile cavity backed crossed slot antennas for dual frequency dual linear polarization and circular polarization applications are first presented in this paper. By employing the substrate integrated waveguide (SIW) technique in the antenna designs, the low profile backed cavity structure can be realized by using only a single layer of low cost printed circuit board (PCB) substrate. A single grounded coplanar waveguide (GCPW) is employed as the feeding element to excite the TE 120 and TE 210 modes in the SIW cavity. A crossed slot structure is used as the radiating element in order to radiate the desired dual linearly or circularly polarized wave. From the measurement results, it is seen that these novel antennas retain the advantages of conventional metallic cavity backed antennas, including high gain, high front-to-back ratio (FTBR), and low cross polarization level (CPL). Furthermore, the proposed antennas also possess the advantages of low profile, light weight, low fabrication cost, and easy integration with planar circuits.

Development of Low Profile Cavity Backed Crossed Slot Antennas for Planar Integration

A compact microstrip line-fed ultrawideband (UWB) tapered-shape slot antenna is presented. The proposed antenna comprises a tapered-shape slot and rectangular tuning stub. The antenna is fabricated onto an inexpensive FR4 substrate with an overall dimension of 22 × 24 mm2. The experiment shows that the proposed antenna achieves good impedance matching constant gain, stable radiation patterns over an operating bandwidth of 3-11.2 GHz (115.5%) that covers the entire UWB. The nearly stable radiation pattern with a maximum gain of 5.4 dBi makes the proposed antenna suitable for being used in UWB communication applications.

Compact Tapered-Shape Slot Antenna for UWB Applications

A novel design is described for a circularly polarized square slot antenna (CPSSA). Circular polarization (CP) operations can be attained using a lightening-shaped feedline protruded from the signal line of the feeding coplanar waveguide (CPW). The CP bandwidth can be significantly enhanced by implanting a pair of inverted-L grounded strips into the slot and adjusting the dimensions of the lightening-shaped feedline, whereas the impedance bandwidth can be greatly enlarged through tuning embedded vertical and horizontal stubs. The designed antenna was measured to exhibit a CP bandwidth of as high as 48.8%.

Broadband CPW-Fed Circularly Polarized Square Slot Antenna With Lightening-Shaped Feedline and Inverted-L Grounded Strips

This letter presents a new design for a circularly polarized square slot antenna (CPSSA). The proposed single-layer antenna composed of a square ground plane embedded with two unequal-size inverted-L strips around two opposite corners is capable of generating a resonant mode for exciting two orthogonal E vectors. In this model, compared to the previous CPSSA structures, the impedance bandwidth and the axial ratio bandwidth of antenna are increased, which is four times wider than the impedance bandwidth of previous similar designs. The designed CPSS antenna with size 60 × 60 × 0.8 mm3 operates over the frequency band between 2.67 and 13 GHz (4.74:1, 132%) for VSWR <; 2, exhibiting a 32.2% (4.9-6.9 GHz, 1.5:1) circular polarization (CP) bandwidth. Throughout this letter, the improvement process of the axial ratio (AR) and S\\ properties are presented and discussed in detail.

Broadband CPW-Fed Circularly Polarized Square Slot Antenna With Inverted-L Strips for UWB Applications

Wireless Sensor Networks (WSNs) can be defined as a self-configured and infrastructureless wireless networks to monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants and to cooperatively pass their data through the network to a main location or sink where the data can be observed and analysed. A sink or base station acts like an interface between users and the network. One can retrieve required information from the network by injecting queries and gathering results from the sink. Typically a wireless sensor network contains hundreds of thousands of sensor nodes. The sensor nodes can communicate among themselves using radio signals. A wireless sensor node is equipped with sensing and computing devices, radio transceivers and power components. The individual nodes in a wireless sensor network (WSN) are inherently resource constrained: they have limited processing speed, storage capacity, and communication bandwidth. After the sensor nodes are deployed, they are responsible for self-organizing an appropriate network infrastructure often with multi-hop communication with them. Then the onboard sensors start collecting information of interest. Wireless sensor devices also respond to queries sent from a “control site” to perform specific instructions or provide sensing samples. The working mode of the sensor nodes may be either continuous or event driven. Global Positioning System (GPS) and local positioning algorithms can be used to obtain location and positioning information. Wireless sensor devices can be equipped with actuators to “act” upon certain conditions. These networks are sometimes more specifically referred as Wireless Sensor and Actuator Networks as described in (Akkaya et al., 2005).

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Overview of Wireless Sensor Network

This paper presents a new wideband circularly polarized square slot antenna (CPSSA) with a coplanar waveguide (CPW) feed. The proposed antenna features two inverted-L grounded strips around two opposite corners of the slot and a widened tuning stub protruded into the slot from the signal strip of the CPW. Broadside circular-polarization (CP) radiation can be easily obtained using a simple design procedure. For the optimized antenna prototype, the measured bandwidth with an axial ratio (AR) of less than 3 dB is larger than 25% and the measured VSWR les 2 impedance bandwidth is as large as 52%.

Circularly Polarized Square Slot Antenna With a Pair of Inverted-L Grounded Strips

This letter aims at miniaturizing an annular-ring slot antenna that is suitable for the 2.4/5-GHz dual-band operations. The miniaturization purpose was achieved by embedding in the center patch of the antenna a pair of slots to excite three resonant modes. The resonant band of the first excited resonant mode was lowered from that of the unperturbed annular-ring slot antenna, whereas those of the second and third excited resonant modes were combined to form a wide upper operating band by appropriately adjusting the dimensions of the embedded slots. The proposed antenna proves to have very similar copolarization radiation patterns in its two operating bands and have enough antenna gains for practical applications.

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Design of a Compact Dual-Band Annular-Ring Slot Antenna

This letter proposes the design of a new miniaturized circularly polarized (CP) printed square slot antenna (PSSA) fed by a coplanar waveguide (CPW). The characteristics of the design are that the CP operation and impedance matching can be independently achieved. The 3-dB axial-ratio band can be excited by protruding into the slot a halberd-shaped metal strip from the signal line of the CPW, whereas the VSWR ≤ 2 impedance band can be produced by implanting in the slot a grounded asymmetric inverted-T strip. Design rules established for the proposed antenna can effectively reduce the sizes of the ground plane and the slot.

Design of CPW-Fed Circularly Polarized Slot Antenna With a Miniature Configuration

A new easy-to-apply design procedure is proposed in this letter for constructing small wideband circularly polarized (CP) bidirectional and unidirectional square slot antennas. With an asymmetric T-shaped strip protruded from the signal line of the feeding coplanar waveguide (CPW) into the square slot, a reference antenna with a fractional 3-dB axial-ratio bandwidth (abbreviated as CPBW) of about 11% can be obtained. The proposed bidirectional CP slot antenna (BICPSA) can be modified from the reference antenna by stretching the left end of the T-shaped strip upward, by embedding a rectangular metal patch in the square slot, and by implanting a grounded metal strip from the right edge of the slot. The resulting BICPSA has a much larger CPBW of 39.1%, which is about 3.55 times that of the reference antenna. Finally, by placing a simple reflector underneath this BICPSA without changing its structural dimensions, one can obtain unidirectional radiation patterns with a greatly increased gain of 7.6 dBic, but with only a slightly decreased CPBW of 34.3%.

Circularly Polarized Square Slot Antenna With a Largely Enhanced Axial-Ratio Bandwidth

A square slot antenna fed by a coplanar waveguide for dual-band multistandard applications is presented. Printed on the back of the square slot is a composite patch formed by an annular metal ring inscribed by a circular patch. Appropriate design of the composite back-patch resulted in five resonant bands, the first (last) two of which were combined to form a lower (upper) operating band. The ratio of the two operating band centre frequencies can be tuned larger than 2.5. A pair of notches was embedded in the annular metal ring to further broaden the lower (upper) operating band up to a fractional bandwidth of 37% (20%). The measured results indicate that the proposed antenna can cover the frequency bands of the following wireless communication standards: digital communication system, personal communication services, universal mobile telecommunications system and 2.4/5-GHz wireless local-area networks.

Jia-Yi Sze

Papers

Circularly Polarized Square Slot Antenna With a Pair of Inverted-L Grounded Strips

Design of a Compact Dual-Band Annular-Ring Slot Antenna

Design of CPW-Fed Circularly Polarized Slot Antenna With a Miniature Configuration

Circularly Polarized Square Slot Antenna With a Largely Enhanced Axial-Ratio Bandwidth

Dual-broadband multistandard printed slot antenna with a composite back-patch