## 1 Introduction  
Since 2002, the Federal Communication Commission (FCC) has permitted its commercial ultra-wideband (UWB) systems to operate within the 3.1 GHz to 10.6 GHz frequency range [1; 2]. UWB technology has attracted much attention from researchers because of wide impedance bandwidth, high-speed data rate, and good time domain resolution [3; 4]. In sensing applications, UWB antennas are used in short-range transmission [5], medical applications [6; 7], surveillance systems [8], Internet of things (IoT) [9], and wireless body area networks (WBANs) [10]. In medical sensing applications and microwave imaging sensing, UWB radar has been in the spotlight owing to its high accuracy and robustness in a multipath environment. The authors of [6] implemented UWB sensors for detecting microscopic malignant breast tumors and checked their feasibility using multilayered breast phantoms. The authors of [8] designed two different UWB antennas for the solution of pulsed asset tag devices. For portable IoT sensors and WBANs, the compact-sized antenna has received much interest, and can be easily embedded in IoT devices [11; 12; 13]. However, owing to the extremely broadband of operation for UWB systems, there exists an inevitable overlap between UWB communication systems and many narrowband wireless communication systems such as Worldwide-Interoperability for Microwave-Access (WiMAX) operating at 3.30-3.60 GHz, the Indian National Satellite (INSAT) operating at 4.50-4.80 GHz, the wireless local area network (WLAN) operating at 5.15-5.35 GHz and 5.725-5.825 GHz, X-band satellite communication operating at 7.2-7.65 GHz, and the International Telecommunication Union (ITU 8-GHz) frequency band operating at 7.95-8.55 [14]. Hence, we aim to design a compact-sized antenna for IoT applications which can achieve multiple-notched bandsto avoid the potential interferences caused by these narrow-band communication systems within the UWB frequency band [15]. Also, the antenna structure should be simple enough to be fabricated at low cost. The concept of introducing frequency notched bands within UWB antennas was initially proposed in [16; 17]. After these early works, different methods and techniques were developed for designing band-notched UWB antennas, including tuning stubs, the addition of parasitic resonators [18; 19; 20; 21], and etching slots [22; 23; 24; 25; 26; 27; 28; 29]. In other works [22; 23; 24], single band-notched UWB antennas were reported for suppressing interference from the WLAN frequency band. Dual band-notched UWB antennas were reported in [25; 26; 27; 28; 29] to avoid the interference from both the WiMAX and WLAN frequency bands. However, all of these antennas have only single and dual notched bands. Moreover, the frequency selectivity of the embedded notch is not good enough that it rejects the entire WLAN (5-6 GHz) frequency band, though the desired rejection bands are from 5.15 to 5.35 GHz for lower WLAN band and the upper WLAN frequency band operating at 5.725-5.825 GHz. Thus, any useful data within the range of 5.35-5.725 GHz will also be lost, resulting in the severe degradation of the quality of the received UWB signal. To reject the lower and upper WLAN frequency bands along with the WiMAX frequency band, researchers had worked on triple band-notched UWB antennas. However, designing triple band-notched UWB antenna is a difficult task since controlling the notched frequency bandwidth in a limited space creates an undesired and complicated coupling between the resonators. In [29], the authors achieved a sharp rejection of the upper and lower WLAN frequency bands by using independently controllable strips. In [30], a combination of complementary split ring resonators (CSRRs) and DGS resonators was used to achieve the tri-band notching behavior with rejection frequency bands at 3.3-4.0, 5.15-5.40, and 5.80-6.15 GHz.