A compact, reconfigurable antenna supporting multiple wireless services with a minimum number of switches is found lacking in literature and the same became the focus and outcome of this work. It was achieved by designing a Th-Shaped frequency reconfigurable multi-band microstrip planar antenna, based on use of a single switch within the radiating structure of the antenna. Three frequency bands (i.e., 2007–2501 MHz, 3660–3983 MHz and 9341–1046 MHz) can be operated with the switch in the ON switch state. In the OFF state of the switch, the antenna operates within the 2577–3280 MHz and 9379–1033 MHz Bands. The proposed antenna shows an acceptable input impedance match with Voltage Standing Wave Ratio (VSWR) less than 1.2. The peak radiation efficiency of the antenna is 82%. A reasonable gain is obtained from 1.22 to 3.31 dB within the operating bands is achieved. The proposed antenna supports Universal Mobile Telecommunication System (UMTS)-1920 to 2170 MHz, Worldwide Interoperability and Microwave Access (WiMAX)/Wireless Broadband/(Long Term Evolution) LTE2500–2500 to 2690 MHz, Fifth Generation (5G)-2500/3500 MHz, Wireless Fidelity (Wi-Fi)/ Bluetooth-2400 to 2480 MHz, and Satellite communication applications in X-Band-8000 to 12000 MHz. The overall planar dimension of the proposed antenna is 40 × 20 mm2. The antenna was designed, along with the parametric study, using Electromagnetic (EM) simulation tool. The antenna prototype is fabricated for experimental validation with the simulated results. The proposed antenna is low profile, tunable, lightweight, cheap to fabricate and highly efficient and hence is deemed suitable for use in modern wireless communication electronic devices.
Advancement in the domain of wireless communication requires a single portable electronic device to serve multiple wireless services. Commonly used wireless services for communication and space applications used by European Space Agency plus their ranges are summarized in
Wireless application | Frequency range (MHz) |
---|---|
Universal Mobile Telecommunication System (UMTS) | 1920–2170 |
Worldwide Interoperability and Microwave Access (WiMAX) | 2500–2690/5250–5850 |
Long Term Evolution (LTE2500) | 5150–5350 |
Wireless Local Area Network (WLAN) | 2400–2480 |
Bluetooth | 2400–2480 |
As every wireless technology has its own requirements, multiband antennas with the reconfigurable ability (Frequency, Pattern and Polarization) are the preferred choice in recent wireless systems. These reconfigurable antennas operate on multiple resonant frequencies whereas reconfigurable techniques enhanced its performance in terms of efficiency, battery power, and cost. In a conventional multiband antenna system, the radiation happens to be on multiple frequencies without giving due consideration to the end users’ preferences. Hence more battery power is consumed and degrades overall antenna performance (efficiency). Due to the flexible and attractive features of reconfigurable antennas’ researchers have proposed different designs [
The arc-shaped slot is investigated in [
A slot antenna using PIN diodes to achieve frequency reconfiguration for four bands was implemented in [
In the literature, it can be observed that researchers have used different reconfiguration approaches. Electrical reconfiguration techniques are easy to implement and have a comparatively low cost; however, they require a biasing circuit, which complicates the overall antenna structure. Optical reconfiguration does not require biasing lines, but it is lossy in nature and has a complex activation mechanism. Mechanical reconfiguration does not require a biasing system or active elements, but the antennas are comparatively slow in response and need a dedicated power source. Smart material-based reconfiguration, albeit lighter in weight, leads to lower efficiency and limited applications [
Antenna size is one of the key parameters for feasible integration in electronic devices. For multiband operation, the size of the antenna becomes an issue. Researchers have designed various antennas of different sizes to achieve optimum frequency bands for wireless communication [
In this paper, a novel, Th-shaped, frequency switchable, a monopole antenna, using a PIN diode switch, is proposed. To enhance the performance of the reconfigurable antenna, the truncated ground plane is used, while to reduce its footprint, the antenna size is kept small. To simulate PIN diode behavior in CST Microwave Studio, lumped elements are used. In the switch OFF state, a high resistance value is used to block the flow of current in specific portions of the radiating structure. A minimum value of resistance is used in the switch ON state, to allow full flow of current. The performance of the antenna is evaluated in both these states. These bands supported by the proposed antenna can be utilized for wireless services that include Worldwide Interoperability and Microwave Access (WIMAX), LTE2500, WLAN and various satellite applications.
The rest of the paper is organized as follows: the methodology and design geometry of the reconfigurable planar monopole antenna proposed is explained in Section 2. The Measured and Simulation results are discussed and presented in Section 3. Finally, the findings are concluded in Section 4.
Parameter | Value (mm) | Parameter | Value (mm) |
---|---|---|---|
C1 | 8.5 | Cf | 18.5 |
C2 | 3 | Wf | 3 |
C3 | 4.5 | Ls | 40 |
C4 | 6.5 | Wg | 20 |
C5 | 8 | Wg | 20 |
C6 | 3 | Cg | 9 |
A Pin diode is used for switching, which works as adjustable resistor in the radio frequency range. Tunability is obtained with the help of a pin diode which, like any other diode, acts as an open and short circuit under certain operating conditions. When the pin diode is in ON state, the effective length of the current path increases, leading to the antenna resonating within lower frequency bands. On the other hand, when the pin diode is in its OFF state, the effective length of the current path becomes shortened. This leads to the antenna resonating at comparatively higher frequency bands, as shown in
The designed procedure and simulations are performed on the CST Microwave Studio (CST MWS). A waveguide port with the optimum size is used for excitation. The parameters i.e., gain, reflection coefficient, E-field and H-field are analyzed using optimum boundary conditions and field monitors in the CST microwave studio.
The radiation patterns of the proposed antenna is measured in the set up as shown in
The simulation-based reflection coefficient of the proposed antenna is analyzed using CST Microwave Studio whereas measured results are obtained by utilizing a Vector Network Analyzer (VNA) and anechoic chamber facility. As per simulation, the Th-Shaped antenna shows tri-band behavior in the switch ON state, operating within 2007–2501 MHz, 3660–3983 MHz and 9341–1046 MHz bands, as shown in
S. No | Switch modes | Description |
---|---|---|
1 | ON | Tri band (2.19, 3.81, 9.72 GHz) |
2 | OFF | Dual band (2.90, 9.79 GHz) |
Gain patterns of the proposed antenna structure are analyzed in both the ON and OFF states of the switch. The h-plane pattern reveals that the proposed structure is radiating in all directions. At an angle of 90° in the E-plane pattern, nulls are observed. E-Plane Gain patterns of the proposed structure, in both the ON and OFF states of the switch, for the respective resonant frequencies, are shown in
While the switch is in ON mode, the values of gains are 1.39, 1.61 and 3.31 dBi at 2.19, 3.81 and 9.72 GHz respectively. In contrast, when the switch is in the OFF state, the resonant frequency shifts to dual-band operation i.e., 2.90 and 9.79 GHz, with respective gain values of 1.22 and 1.83 dBi.
The surface current distribution over the radiating structure is investigated for both states of the switch (ON/OFF). The surface current contributions/distributions, in both the ON and OFF states, are shown in
In the Switch ON state, it is observed that the whole part of the central/main radiating structure, including “T” portion, is contributing in radiating at 2.19 GHz. At 3.81 GHz, the central part of “h” portion and some positions of the main radiating structure are involved in radiation. It is also observed that some specific parts of the whole structure are contributing to radiation at resonant frequency of 9.72 GHz.
In the Switch OFF state, the “T” part is no more responsible for radiation and a portion of the radiator below the switch radiates at frequencies 2.90 GHz and at 9.79 GHz.
Antenna size is one of the key parameters in designing, fabricating, and integrating in an electronic device. Researchers have designed various antennas of different sizes to optimize them for wireless communication. Large size antennas need more space requirements which might not be desirable in most wireless systems. The proposed frequency reconfigurable multi-band monopole antenna is miniaturized (40 × 20 × 1.6 mm3) to occupy less space. The addition of reconfigurability enhances its performance, with a wide frequency range to support multiple wireless services i.e., UMTS, Wi-Fi, Bluetooth, WiMAX, LTE2500 and X-band satellite applications.
The overall summary of the performance of our proposed Th-Shaped frequency reconfigurable monopole structure is given in
Ref. work | Size (mm2) | No of bands | Frequency (GHz) | Impedance bandwidth (MHz) | Gain (dB) | Rad. efficiency (%) | No. of switches |
---|---|---|---|---|---|---|---|
[ |
880 | 4 | 2.4, 5.13, 3.49, 5.81 | 750–1260 | 1.72–2.96 | 76.43–84.2 | 1 |
[ |
15625 | 4 | 5.37, 6.03, 6.84, 8.87 | --- | −1.1 | --- | 4 |
[ |
2250 | 3 | 2.4, 5.2, 3.5 | 108–330 | 2.5–5.8 | --- | 2 |
[ |
2250 | 3 | 2.4, 3.5, 5.2 | 330–1490 | 0.02–2.8 | 53–71 | 6 |
[ |
1600 | 4 | 1.8, 2.2, 2.3, 2.4 | 60–96 | 7.1–4.36 | 55–72 | 5 |
[ |
2301 | 3 | 2.42, 2.36, 3.64 | 160–270 | 0.7–1 | --- | 1 |
[ |
3600 | 5 | 2.4, 4.26, 4.32, 4.58, 5.76 | 60–170 | 1.31–2.77 | --- | 3 |
[ |
1295 | 4 | 2, 3.4, 2.4, 3.1 | 200–960 | 1.76–1.98 | >90 | 2 |
This work | 800 | 5 | 2.19, 3.81, 9.72, 2.90, 9.79 | 323–1119 | 1.22–3.31 | Upto 80 | 1 |
Parameter | Switch ON (Triple band) | Switch OFF (Dual band) | |||
---|---|---|---|---|---|
Frequency (GHz) | 2.19 | 3.81 | 9.72 | 2.90 | 9.79 |
Gain (dB) | 1.39 | 1.61 | 3.31 | 1.22 | 1.83 |
Directivity (dBi) | 2.3 | 4.4 | 4.87 | 2.57 | 3.72 |
Impedance bandwidth (MHz) | 494 | 323 | 1119 | 703 | 951 |
Impedance (Ω) | 45.12 | 49.36 | 50.04 | 54.71 | 51.79 |
Radiation efficiency (%) | 80.65 | 52.60 | 69.75 | 73.08 | 64.27 |
VSWR (Ratio) | 1.15 | 1.03 | 1.03 | 1.10 | 1.14 |
Reflection coefficient (dB) | −19.74 | −39.71 | −33.25 | −25.05 | −23.14 |
The comparison of this research work with the existing relevant state of the art works is listed in
A Th-Shaped, planar monopole, multi-band, frequency reconfigurable antenna is proposed for UMTS, LTE2500, 5G, Wi-Fi, WIMAX, Bluetooth and satellite applications is proposed in this work. The discrete switch is used to enable frequency reconfigurability to enable its operation on various wireless services depending upon the state of the switch (ON/OFF). The antenna reveals triple-band nature and covers a range of frequencies (2007–2501 MHz), (3660–3983 MHz) and (9341–1046 MHz) in the ON state of the switch. However, in this state, the third frequency band (9341–1046 MHz) is the third harmonic resonance of the second band (3660–3983 MHz) with satisfactory radiation properties. Similarly, dual-band characteristics with operating frequency ranges (2577–3280 MHz) and (9379–1033 MHz) are observed in the OFF state of the switch. In the OFF state, the second band is the third harmonic resonance of the 2577–3280 MHz frequency band with optimum radiation characteristics. The proposed antenna is quite small however it has radiation efficiency of up to 82%. The nearly Omnidirectional radiation pattern of the proposed antenna within the far-field increases its applicability for short-range broadcast applications. The antenna covers a specific range of frequencies used in different wireless services and can be a prospective candidate to be used in devices that include laptops, smartwatches, mobile phones, and autonomous vehicles.