# A Low-Cost CPW-Fed Multiband Frequency Reconfigurable Antenna for Wireless Applications
## 1 Introduction  
The antenna is considered a vital component for every wireless communication system nowadays. To meet the requirements of different applications in one device, multiband antennas, wideband antennas, and reconfigurable antennas have served this purpose. These individual devices can have many uses, e.g., for global positioning systems (GPS), global system for mobile communication (GSM), Bluetooth, wireless local area network (WLAN), etc. Antenna size and cost are two significant factors when designing any sort of antenna. Reconfigurable antennas are found to be the best solution, as they can be reconfigured to resonate on different frequencies to provide various functions. Reconfigurable antennas also offer unique advantages, such as flexibility and compactness. Reconfigurable antennas can modify their properties such as frequency, polarization, and radiation pattern with changing environmental conditions or varying system requirements in a controlled manner [1]. A comprehensive and detailed review regarding microstrip reconfigurable antennas has been provided by [PERSON] et al. [2]. Different modern techniques for reconfiguration have been analyzed and the pros and cons are discussed. Methods of improving the switching capability and achieving operation at different frequency bands are discussed and investigated. Frequency reconfigurable antennas are advantageous for diverse applications, as the need for the bandwidth of spread-spectrum signals is decreased. This is because all operating frequencies are not supposed to be covered by a wireless application simultaneously. As a result, the functionality of the antenna is improved by keeping the size small and less complicated [3]. In frequency reconfigurable antennas, low cost, miniaturized size, and use for various applications are other necessary characteristics that result in their incorporation in maximum modern wireless communication systems [4]. Many types of techniques for feeding have been reported, but the coplanar waveguide (CPW) feeding technique has been the most preferable. It reduces the complexity in design by employing the antenna patch and the ground plane on the same side of the substrate. Several researchers have attained frequency reconfiguration by changing the operative length of the antenna by removing or adding part of its length by using various approaches, such as varactors or variable capacitors [5]. Varactor diodes are used to redirect surface current, therefore letting a smooth change in frequency with altering capacitance [6]. The authors presented a varactor-based reconfigurable antenna with the capability to operate in the tuning range from 890 to 1500 MHz with good impedance matching [7]. This antenna is very promising because the multiple smaller patches are connected by means of varactors which permit polarization agility, frequency tuning, and phase shifting. Likewise, [PERSON] et al. [8] presented a different multisubpatch microstrip antenna loaded with varactors for solving the reconfiguration problem. A cedar-shaped reconfigurable antenna was designed for operation in WiMAX, Bluetooth, GPS, and WLAN bands [9]. Both PIN and varactor diodes are used in combination to achieve the reconfigurability. Three pairs of varactor diodes were utilized for achieving such an objective. Due to the utilization of so many varactor diodes with different variations, it becomes very lossy as the varactors used were from two different manufacturers, including SMV1211 from SKYWORKS and 1 SV325 from TOSHIBA. Also, the overall size of the antenna is very bulky, and the total board size is \(6.5\times 6\) cm\({}^{2}\). However, varactor diodes are considered undesirable as they are nonlinear and exhibit a narrow tuning range [10]. Likewise, the authors proposed a varactor-based antenna with a tuning range from 2.34 to 2.68 GHz [11]. Such tuning is achieved by changing the varactor diode capacitance between 12.33 pF (0 V) to 1.30 pF (15 V). [PERSON] et al. [12] reported a tunable wideband frequency with polarization reconfiguration.