A Switchable Filtering Antenna Integrated with U-Shaped Resonators for Bluetooth, WLAN & UWB Applications

co.in A Switchable Filtering Antenna Integrated with U-Shaped ░ ABSTRACT - In this paper, A Switchable Filtering Antenna Integrated With U-Shaped Resonators for Bluetooth, WLAN & UWB Applications is presented. To achieve the UWB operation, a rectangular defect on the ground plane and square slots are etched on the rectangular patch. The selectivity of frequency is achieved by integrating a Hairpin filter. Three switches are connected at the corners of the filter to achieve frequency re-configurability. A total of eight Boolean combinations are possible by controlling ON and OFF these switches. This filtering antenna acts as a band pass filter and picks distinct frequency bands within the UWB frequency. It can be used for wireless applications such as Long-Distance Radio Communication, Aviation Services, WLAN, C-band satellite communication, Wi-MAX, mobile satellite sub-band, radar communications, and space communications. In addition, two inverted U-shaped resonators of differing lengths are engraved on the rectangular microstrip patch to operate at Bluetooth frequency applications with frequencies ranging from 2.4 to 2.458GHz. The maximum gain obtained out of all operating frequencies is 4.82dBi at a frequency of 9.5GHz. The proposed antenna is simulated using the 3D-Simulation tool CST MWS. The performance of the designed antenna is estimated using the parameters like return loss, VSWR, and Far-field Gain characteristics.

Since the FCC opened up the 3.1-10.6 GHz spectrum for ultrawideband (UWB) operation, several protocols have been developed to provide moderate and high-rate short-range communication systems. To fulfill commercial and functional standards, various systems such as wireless-broadband (WiBro), wireless local area network (WLAN), and wireless personal area network (WPAN), must include a compact and portable wideband or multiband antenna [1]. One of the most essential aspects of UWB is that it is a zero-carrier technology, which means that no carrier is required for pulse transmission. This gives insight into future development. Because of its low cost, fast data rate, and superior multipath and jamming resistance, UWB systems have piqued the interest of academics all around the world. [2] discussed about a system, a low power area reduced and speed improved serial type daisy chain memory register also known as shift Register is proposed by using modified clock generator circuit and SSASPL (Static differential Sense Amplifier based Shared Pulsed Latch). This latch based shift register consumes low area and low power than other latches. There is a modified complementary pass logic based 4 bit clock pulse generator with low power and low area is proposed that generates small clock pulses with small pulse width. The vast frequency range for UWB systems between 3.1-10.6 GHz will cause interference with current wireless communication systems, such as IEEE 802.11a WLANs running in the 5.15-5.35 and 5.725-5.825 GHz bands, necessitating the deployment of a UWB antenna with band selective capability [3]. Microstrip patch antennas (MPAs) are gaining popularity in current research due to their smaller patch size, increased bandwidth, and suppression of unwanted crosspolarized radiations. The Defected Ground Structure (DGS) is essential for improving the traditional MPA's features. Based on the shape and size of the ground defect, the DGS introduces a form defect on the ground plane that disrupts shielded dispersion. This has an impact on the antenna's input impedance and current flow [5]. Recently, microwave filters gained a lot of popularity to achieve frequency selective characteristics. A filter is a 2-port network that transmits at frequencies within the filter's pass band and attenuates in the filter's stop band to regulate the frequency response at a given location in a system.
In all communication systems, microstrip band pass filters play a significant role. Microstrip circuits provide benefits over other microwave transmissions such as waveguides, coaxial cables, and strip lines as filters that are realized with wide bandwidth, compact size, easy fabrication, and high reliability and reproducibility. These filters built on printed circuit boards (PCB) have the advantage of being simple and inexpensive to mass-produce in various dielectric constants [6][7][8]. A filter is a 2-port network that transmits at frequencies within the filter's pass band and attenuates in the filter's stop band to regulate the frequency response at a particular location in a system [9][10][11]. A microstrip bandwidth reconfigurable filtering antenna may be created by simply tuning the transmitting zeroes. With transmission zeros, an electrically reconfigured BPF was achieved, resulting in substantially greater selectivity. The conformal profile, compact size, [4] emphasized that people who are visually impaired have a hard time navigating their surroundings, recognizing objects, and avoiding hazards on their own since they do not know what is going on in their immediate surroundings. We have devised a new method of delivering assistance to people who are blind in their quest to improve their vision. An affordable, compact, and easy-to-use Raspberry Pi 3 Model B+ was chosen to demonstrate how the proposed prototype works and simple structure of this antenna are all benefits [12][13][14]. Carving a slit in the radiating patch or introducing a degenerate structure near the feeding line or ground plane is commonly used to provide the notch function.
To achieve re-configurability, two microstrip lines parallel to the feeding line and two PIN diodes are employed [16][17]. The use of lumped components such as positive-intrinsic-negative (PIN) diodes allows antennas with reconfigurable structures to be modified, allowing them to adapt to varied frequencies [18][19]. To adjust the resonance frequency, patch antenna slots are provided, and these slots are linked or detached using switches [20]. Because of their use in integrated circuits and applications, switchable antennas are highly recommended [21]. By introducing two transmission zeros through two independent Ushaped resonators integrated at the rectangular patch, the bandwidth reconfigurable filtering antenna is illustrated in [22][23]. The transmission zeroes are generated when the resonators are linked to the antenna's transmission line over a minimum coupling distance [24]. But these filtering antennas offer tore complexity while integrating with the filter structure. Additionally, the tuning of operating frequency is also difficult in the above literature.
In this paper, a simple UWB Microstrip Antenna is proposed and integrated with a hairpin filter on a defected ground structure (DGS) with a microstrip feed line. The selectivity of frequency is implemented by installing three switches at the corners of the filter. Further, two resonators are introduced to extend the band of operation to Bluetooth applications.

░ 2. ANTENNA DESIGN
The suggested antenna is made of FR4 and has a dielectric constant of 4.4, with a loss tangent of 0.002. Between the ground plane and a rectangular patch of 32*16 2 size, the substrate is sandwiched. The overall dimension of the proposed design is 34*30*1.6 3 . The antenna is fed with a conventional microstrip line feed with a dimension of 17*4.7 2 . The geometry of the basic design is shown in figure 1. In the table1, the dimensions of the proposed design are listed.  The proposed antenna is implemented with the defected ground structure to enhance the bandwidth. The dimension of the ground plane is optimized to 16.2*30 2 . Furthermore, two rectangular slots with the size of 2*2.2 2 are carved onto the rectangular patch. Figure 2 depicts the proposed design with a defected ground structure and with two rectangular slots. In recent times, microwave filters have gained much attention to achieve frequency re-configurability. Microwave filters improve the signal-to-noise ratio by removing undesired frequency components from the stream. These filters are especially effective in the radio UHF region, where they may filter out unwanted broadcasts and improve the receiver's relative sensitivity.   To achieve frequency re-configurability without increasing the size of the antenna, the hairpin filter is integrated within the feed line. After integrating with the hairpin filter, the antenna is considered a filtering antenna which is portrayed in figure 4. The proposed filtering antenna with eight combinations of switches is used to select the frequencies within the UWB frequency range. In addition to the UWB frequency, two inverted-shaped resonators are etched on the patch to operate at Bluetooth frequency (2.4GHz to 2.458) GHz. The filtering antenna along with the resonators is shown in figure 5. The optimized dimensions of the resonators are tabulated in table 4.

International Journal of Electrical and Electronics Research (IJEER)
For better visualization of the resonator part, it is enlarged and depicted.

░ 3. RESULTS AND DISCUSSION
The designed antenna is simulated using the CST MWS 3Dsimulation tool. Initially, the rectangular-shaped patch antenna is simulated and analyzed. The antenna is operated at 9.24GHz with a return loss of -24.90dB. The bandwidth obtained is very small, i.e., 288.8MHz. The gain obtained at this operating frequency is 4.9 dB, as shown in figure 6. The return loss plot of the proposed design is shown in figure 7.  The proposed antenna ground plane is carved to disrupt the passage of current in the metal plane to boost bandwidth. The rectangular-shaped part is removed from the ground plane using the Defected Ground Structure (DGS). After optimizing the ground plane, the operating bandwidth was increased from 2.95GHz to 7.75GHz. The bandwidth obtained is 4.79GHz.    To confer the frequency re-configurability, the filter is integrated with the feed line. Due to the integration of the hairpin filter, the proposed design selects the pass band frequencies for the required wireless applications. Three switches are substituted for eight Boolean possibilities using a third-order filter. Because of their dependability, low cost, high switching speed, compact size, and lower capacitance and resistance in their ON and OFF states, pin diodes will be employed for the reconfiguration. The 8 combinations of the filter are explained, starting from all switches OFF to all switches ON.

Case-1{All switches OFF (000)}
For each 000 combination, the graph represents the simulated S11. In this case, all of the switches are turned off, allowing  19.19dB. Figure 12 shows the return-loss graphs for the first four combinations. This antenna is suitable for wireless applications such as Wi-MAX, WLAN, and long-range radio communications. This combination produces radiation that is nearly constant. Figure 13 depicts the radiation patterns of the first four circumstances.

Case-2 {Two switches OFF and third switch ON (001)}
The graph depicts the S11 simulation for the 001 combination.

Case-3 {first and third switches OFF and second switch ON (010)}
The S11 simulation for the 010 combination is shown in the graph. The first and third switches are OFF, and the second switch is ON. This combination serves as a notch-filter for the frequency band (5.84-6.68) GHz, with a bandwidth of 840MHz. This situation leads to a minimal return loss of -51.03dB at 6.512GHz. This antenna is ideal for wireless communications, such as long-distance radio conversations. This combination produces consistent radiation patterns throughout the entire working frequency range, with a maximum gain of 2.76dB at 6.51GHz.

Case-4 {first switch OFF and two and three switches ON (011)}
The simulated S11 for the 011 combination is shown in the graph. The first switch is turned OFF in this scenario, but the second and third switches are turned ON. The antenna has a fixed frequency range of (5.41-7.82) GHz. This situation produces a minimum return loss of -50.82dB at 5.61GHz.

Figure 12: Return loss plots of the first four switch combinations
This antenna is appropriate for WLAN and other wireless applications. This case produces virtually constant radiation patterns throughout the entire working frequency range, with a maximum gain of 2.67dB at 5.61GHz.

Case-5 {first switch ON and two and three switches OFF (100)}
The S11 for 100 combination simulation is depicted in the graph. In this setup, the first two switches are turned OFF and the third switch is turned ON. The antenna operates in a single frequency band of 6.9681 to 8.681 GHz. This situation leads to a minimal return loss of -24.12dB at 7.4GHz. This antenna is ideal for wireless applications, especially satellite communications and Wi-MAX applications. This case produces consistent radiation patterns throughout the entire working frequency range, with a maximum gain of 3.43dB at 7.4GHz.

Case-6 {second switch OFF and first and third switches ON (101)}
The graph depicts the S11 simulation for the 101 combinations. The first two switches are turned OFF, while the third switch is turned ON in this scenario. The antenna has a single frequency band that ranges from 6.96 to 8.68 GHz. At 7.4GHz, this circumstance results in a minimum return loss of -24.12dB. This antenna is an excellent choice for wireless applications, particularly satellite communications and Wi-MAX applications. With a maximum gain of 3.43dB at 7.4GHz, this case delivers steady radiation patterns over the full operating frequency ranges.

Case-7 {first and second switches ON and the third switch OFF (110)}
The graph depicts the S11 for 110 combinations as simulated.
The first and second switches are both turned ON, whereas the third switch is turned OFF in this configuration. The antenna has a single frequency band that ranges from (

Case-8 {All switches are ON (110)}
The graph depicts the S11 simulation for the 111 combinations.
All the switches are switched on in this circumstance, allowing energy to go the greatest distance and radiate from every part of the antenna. The antenna may resonate in two different frequency bands: (4.79-7.98) GHz and (9.28-12.56) GHz. The frequency range (7.98-9.28) GHz is rejected from the whole UWB frequency by this combination. This combination yields a minimal return loss of -28.22dB at 9.52GHz. This antenna is perfect for mobile satellite sub-band communications as well as satellite or radar communications. This combination produces essentially constant radiation patterns throughout the full working frequency ranges, with a maximum gain of 5.05dB at 9.524GHz. Figures 14 and 15 shows the return loss graphs and radiation patterns for the last four combinations. The return loss, gain, and applications of the eight switch combinations are given in table-5.

RESONATOR
The proposed antenna now covers many wireless applications from 3GHz to 12GHz frequency bands like Wi-MAX, WLAN, Long-Distance Radio Communication, Aviation Services, Radiolocation Services, mobile satellite sub-band, and satellite or radar communications. To cover the Bluetooth frequency also, the proposed design is integrated with two inverted U-shaped resonators, which are etched on the rectangular patch. The lengths of the resonators are optimized to operate at Bluetooth frequencies. In each resonator, there is destructive interference of the signal. As a result, the filter's insertion loss response has a transmission zero. The final design will operate at a frequency range of 2.4097 to 2.475GHz along with a 9.5GHz pass band frequency. The minimum return loss obtained is -29.38dB and the gain is 1.71dBi at a particular frequency of 9.5GHz.

░ 5. FUTURE WORK
The proposed design is compact and a simple rectangular patch is used as a radiating element. The proposed design is operating at different microwave frequencies with very good gain values. The feed line width is more i.e., ℎ ⁄ >>ʎ causes unnecessary radiation. It leads to fringing effects and surfaces current. The Feed line width may be reduced further to increase the performance of the proposed design. The Design may be fabricated to verify the performance.