GHz WLAN Band Research Articles

A −40 dB EVM, 77 MHz Dual-Band Tunable Gain Sub-Sampling Receiver Front End in 65-nm CMOS

In this paper, the first dual-band sub-sampling receiver front end with sampling frequency optimization to meet the ultimate receiver error vector magnitude (EVM) of −40 dB over wide input power range of 19 dB is proposed. A systematic sub-sampling receiver chain EVM optimization with respect to major system-level impairments, such as noise folding, sampling frequency, IQ mismatches, phase noise of the sub-sampling clock, and unit capacitor value realizable at the decimation filter, is presented. The proposed dual-band sub-sampling receiver has a 26–41 dB continuously tunable gain for 2.4 GHz and 26–38.5 dB for the 5 GHz WLAN band. Continuously tunable gain ensures the ultimate receiver EVM performance over wider input power levels. In addition, the 5 GHz band is continuously tunable from 4.5 to 5.7 GHz. An active balun feedback low-noise amplifier followed by a sub-sampling down-conversion mixer is implemented to down-convert both WLAN bands to an intermediate frequency in the range from 445 to 538 MHz. Sub-sampling frequency optimization proposed in this paper down-converts both WLAN bands with the sampling frequency from 1.78 to 2.15 GHz to reach the target EVM. Additionally, a switched capacitor decimation filter running at 90 MHz is implemented to provide dual functionalities of down-conversion to baseband and band selection. A test-chip is implemented in a 1.2 V 65-nm CMOS technology. The proposed dual-band sub-sampling receiver occupies a total active area of 0.72 mm2 and has a total power dissipation of 55.6 mW. The overall receiver chain shows a noise figure of 11.5 dB at the highest gain and an IIP3 of −8 dBm at the lowest gain.

Dumbbell Shaped Microstrip Broadband Antenna

The article proposes a dumbbell shaped broadband microstrip antenna which consists of dumbbell shaped octagons and a valley shaped backplane with a partial ground plane and multiple circular and rectangular slits. The design can be used for multiple applications working in frequency ranges from 3.48 GHz to 25 GHz. The overall dimension of the proposed antenna is 20 x 15 x 1.5 mm 3 . It is fabricated on FR4 substrate which has electrical permittivity of 4.3 and loss tangent of 0.025. FR4 is a low cost and easily available. The antenna covers partial frequency range for ultra-wide band applications, 3.5/5.5GHz WiMAX band, 5.2/5.8GHz WLAN band, 8/12 GHz X-band, 12/18 GHz Ku –band. It can be used in space and satellite communications etc. The peak gain is 4.5 dB and peak radiation efficiency is 68%. Simulated results are in agreement with the measured results. Curves of radiation pattern and S-parameter of both simulated and measured results are shown. The impedance curves, surface current, radiation efficiency, simulated return losses, gain, and radiation patterns of the proposed antenna are described in the paper.

A compact four‐element multiple‐input‐multiple‐output antenna with enhanced gain and bandwidth

AbstractA compact four‐element wideband planar multiple‐input‐multiple‐output (MIMO) antenna is proposed. The radiating elements are half‐loop monopoles. In order to cover the 5.8 GHz WLAN band, an additional high‐frequency operation mode is excited by an inter‐connected coupling parasitic element, and the radiation gain attained is enhanced via the arrangement of elements. The proposed four‐element MIMO antenna operates in a wide frequency range of 4.58‐6.37 GHz (34.3%), which covers the 5.2/5.8 GHz WLAN band and 5.5 GHz WiMAX band. For each element, an average gain of greater than 3.18 dBi is achieved, and the envelope correlation coefficient (ECC) between elements is lower than 0.05. The overall size of the compact multiport antenna system is only 40 × 36 mm2 with minimum isolation of 19 dB between its elements and has no any complex decoupling structure. Since the antenna has a satisfactory MIMO performance and is easily integrated with a planar structure, it is an excellent candidate for the MIMO communications application.

A novel design of a planar antenna with modified patch and defective ground plane for ultra‐wideband applications

AbstractIn this article, a novel design of a planar antenna with modified patch and defective ground plane for UWB applications is presented. The optimum dimension of the antenna is 20 × 25 × 1.5 mm3 and it is fabricated on commercially available low‐cost FR‐4 substrate having relative permittivity (εr = 4.3) and relative permeability (μr = 1) with a loss tangent of 0.025. The impedance bandwidth of the proposed antenna (magnitude of S11 [S11 < −10 dB]) is 110% (3.1‐10.8 GHz). The peak gain and the peak radiation efficiency of the proposed antenna is 5.1 dB and 89%, respectively, in the proposed band of operation. Simulated and measured results of the proposed antenna are in good agreement. The proposed antenna is suitable for ultra‐wideband applications, 3.5/5.5 GHz WiMAX band, 5.2/5.8 GHz WLAN band, 4/6 GHz satellite communication, and various other wireless communication applications.

Wide-Beamwidth Unilateral Dielectric Resonator Antenna Using Higher-Order Mode

For the first time, a unilateral rectangular dielectric resonator (DR) antenna (DRA) is designed using two DR modes, namely the fundamental $\boldsymbol{TE}_{\boldsymbol{\delta }11}^{\boldsymbol{x}}$ mode and higher-order $\boldsymbol{TE}_{2\boldsymbol{\delta }1}^{\boldsymbol{y}}$ mode. The former and latter provide the broadside and quasi-omnidirectional radiation patterns, respectively. By combining the radiation fields of the two resonant modes, unilateral radiation with wide 3 dB beamwidths can be obtained. For demonstration, a unilateral rectangular DRA was designed in 2.4 GHz WLAN band. Across the WLAN band, the DRA has a measured front-to-back ratio (FTBR) of higher than 15 dB. It is found that the measured maximum FTBR of the DRA is 36.6 dB, whereas the measured 3 dB beamwidths of the two principal radiation planes are both wider than 174°.

High gain dual-polarised pentagonal microstrip antenna for wireless communications

In this paper we propose a dual polarised pentagonal microstrip antenna for massive MIMO-base station to operate at 2.4 GHz WLAN band (IEEE 802.11 b/g/n/ax). The various researchers have used antenna array with different feeds for the massive MIMO BS to obtain the desired gain with required impedance bandwidth. However, this proposed work contradicts with existing method by using a single novel radiating element with suspended substrate to achieve the desired gain and required impedance bandwidth. The circular polarisation is achieved by using two coaxial-probe feeds. The main focus of research is on the selection of proper shape of the radiating element for Massive MIMO BS. The proposed antenna is successfully simulated using HFSS 13.0, fabricated on a FR-4 substrate and measured. The proposed antenna exhibits a much higher gain of 6.17 dB, improved impedance bandwidth of 171.9 MHz (return loss, S11=−10 dB), the axial ratio (AR) is 1.78 dB (< 3 dB), the patch area of 1,775 mm2, and also yields return loss better than −15 dB around the centre frequency of 2.45 GHz. The measured characteristics of the antenna are in good agreement with the simulated results.

A Low Profile, Dual-band, Dual Polarized Antenna for Indoor/Outdoor Wearable Application

A planar, low-profile, dual-band and dual-polarized antenna on a semi-flex substrate is proposed in this paper. The antenna is fabricated on Rogers substrate with a thickness of 3.04 mm and sized at $70.4 \times 76.14 \times 3.11$ mm3 ( $0.37\lambda _{0} \times 0.40\lambda _{0}\times 0.016 \lambda _{0}$ ) only. The circular polarization property is enabled in the global navigation satellite system (GNSS) L1/E1 (lower) band by introducing a complementary split ring resonator on the antenna patch. Meanwhile, the antenna operates in the second (upper) 2.45 GHz WLAN band is enabled by etching a U-shaped slot on its ground plane. This simultaneous, dual-band and dual-polarized operation enables the proposed antenna to be applied in the indoor/outdoor wearable application. To isolate the antenna against the influence of the human body, a multiband artificial magnetic conductor (AMC) plane is added on the reverse side of the dual-band radiator. Comparison of the antenna without AMC in free space and when evaluated on the chest of a human body backed by AMC showed improved gain; from 3–5.1 dBi in the lower band, and from 1.53–5.03 dBi in the upper band. Besides that, the front-to-back ratio of the AMC backed monopole antenna also improved from 11–21.88 dB and from 2.5–24.5 dB in the GNSS and WLAN bands, respectively. Next, the specific absorption rate (SAR) of the monopole antenna with and without the AMC plane is assessed. Evaluation results indicate that the maximum SAR value decreased by up to 89.45% in comparison with the antenna without AMC in the lower band. This indicates the effectiveness of the AMC array in increasing gain and FBR, besides reducing EM absorption in the human body.

Wide‐bandwidth multifrequency circularly polarized monopole antenna for wireless communication applications

In this article, wideband circularly polarized monopole antennas with multiresonating frequencies are presented for Bluetooth, WLAN, WiMAX, and X-band applications. The designed antennas have dimensions of 50 × 35 × 1.6 mm3. Two different substrates (FR4-epoxy and PTFE) are used for fabricating the antennas. The antennas consist of corner truncated I-shaped and C-shaped strips excited by a 50 Ω microstrip feed line. The parametric analyses are performed with the help of Ansoft HFSS V.11 EM simulator. Both antennas have been fabricated and measured. The measured percentage bandwidth of the antenna made by FR4 substrate is 31.32% (centered at 1.66 GHz), and 64.85% (centered at 5.69 GHz). The percentage bandwidth of antenna made by PTFE substrate is 20.57% (centered 2.43 GHz) and 68.74% (centered at 7.39 GHz). In addition to that, there exists 3 dB AR bandwidth for LHCP of about 1050 MHz for 5.2 GHz WLAN-band. The reflection coefficient, radiation patterns, and the gains of both the antennas are studied in detail. It is found that the measured and simulated results are in good agreement.

A Compact ACS-Fed Tri-band Microstrip Monopole Antenna for WLAN/WiMAX Applications

This paper proposes a novel small asymmetric coplanar strip (ACS) fed tri-band monopole antenna for WLAN and WiMAX applications. To tune and create multiple resonant frequencies, the exciting strip of monopole antenna is connected to two different arms which are a J-shaped directed toward the asymmetric ground plane and an open stub. The proposed monopole antenna with a total size of 14.6 x17.5 mm2 is fabricated and tested. The measured results indicate that the antenna has impedance bandwidths for 10-dB return loss reach about 500 MHz (2.01-2.52 GHz), 230 MHz (3.48-3.71 GHz) and 1.2GHz (5.59-6.72 GHz) which cover widely the 2.4/5.8 GHz WLAN bands and the 3.5GHz WiMAX band. The simulated radiation patterns of the proposed antenna at the three resonant frequencies have a dipole-like radiation pattern in both E-and H-Planes. The compact size, the simple structure and good radiation performances of the proposed antenna makes it well-suited forthe intended applications.

Center-Fed Unilateral and Pattern Reconfigurable Planar Antennas With Slotted Ground Plane

A center-fed, single-layer, planar antenna with unilateral radiation patterns is investigated. The antenna consists of a turnstile-shaped patch and a slotted ground plane, which function as a vertical magnetic dipole and a horizontal electric dipole, respectively. By combining the two orthogonal dipoles with the same radiation intensities and antiphases, unilateral patterns with wide beamwidth and high front-to-back (F/B) ratio are achieved. As the unilateral radiation pattern can be easily steered in the horizontal plane by changing the slot location, a pattern reconfigurable antenna is further designed by using p-i-n diodes to control the connection states of the radial slots on the ground plane. Four steerable beams are obtained, capable of covering the entire azimuthal plane. For demonstration, both the unilateral and pattern reconfigurable antennas operating at 2.4 GHz WLAN band (2.40–2.48 GHz) were fabricated and measured. The measured overlapping bandwidths, with $\vert S_{11}\vert dB and F/B ratio >15 dB, are given by 7.0% (2.33–2.5 GHz) and 6.3% (2.32–2.47 GHz), respectively.

Designs of Textile Antenna Arrays for Smart Clothing Applications

Abstract In this work, three designs of textile antennas, namely, a rectangular microstrip patch antenna, annular slot antenna, and planar inverted-F antenna (PIFA), operating in the 2.45 GHz WLAN band were developed for smart clothing applications. Conductive textile, a copper-plated polyester fabric, was used for fabricating antenna radiators and grounds. An insulating neoprene fabric with a thickness of 4 mm and a permittivity of 1.5 was used for preparing the substrates. The textile patch antenna achieved a maximum gain of 5.96 dBi and a bandwidth of 4.6%. The annual slot antenna showed a moderate gain and bandwidth of 2.9 dBi and 13.1%, respectively. The PIFA achieved the widest bandwidth of 31% but the smallest gain of 1.2 dBi. Furthermore, the performance deterioration of the proposed antennas under various bending conditions was analyzed to evaluate their suitability for wearable applications. Moreover, two 2 × 2 patch and slot antenna arrays were assembled to increase gain and bandwidth. The measured results proved that the developed antenna designs provide superior performance.

Multi‐band bisected Hilbert monopole antenna loaded with multiple subwavelength split‐ring resonators

Here, a simple yet effective design methodology to design multi-band planar antenna is proposed. The monopole antenna structure is realised using a bisected fractal Hilbert curve. Two subwavelength split-ring resonators (SRRs), where one is a Moore shaped fractal SRR, operates at 3.5 GHz, and the other conventional one operates at 5.2 GHz, are placed in proximity to the compact monopole to achieve two additional operating bands apart from the two resonant frequencies of the fractal-shaped monopole. The third and fourth bands are merged to obtain wide impedance bandwidth around 5.5 GHz. The proposed antenna displays tri-band resonance that covers 2.4 GHz WLAN band, 3.5 GHz Wi-MAX band, and the wide band ranges from 5.0 to 6.15 GHz. Stable monopole-like pattern over all the bands is observed. The overall antenna dimension is 33 × 20 × 0.787 mm3. A fabricated prototype is developed that exhibits good agreement between the measurement and simulation results.

Wideband CPW-Fed Spiral-Shaped Slot Antenna for Wireless Applications

A new compact design of CPW-fed wideband (WB) spiral-shaped slot antenna is proposed. The proposed antenna has a compact size with overall dimensions 37-33 mm and is fabricated on FR4 substrate with dielectric constant ɛ r = 4.4 and thickness h = 1.6 mm. With the different length of the spiral-shaped slots, simulated and experimental results of the antenna are suitable for WB operations. The–10 dB bandwidth of the WB antenna from measurement is approximately 115.2% (2.36–8.53 GHz). The proposed antenna provides nearly omni-directional radiation characteristics. The new antenna configuration operates in several different bands: 2.4, 3.5, 5.2, 5.5, and 5.8 GHz covering 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands. The results for S11, far-field H- and E-plane radiation patterns and gain of the proposed antennas are presented and discussed. The agreement between measured results and full-wave simulation validates the feasible configuration of the proposed antennas.

Transparent Patch Antenna Using Metal Mesh

This communication presents the design, fabrication, and measurement of transparent antennas with metal mesh (MM) for wireless transparent applications such as smart windows, transparent mobile devices, and transparent Internet of Things. The MM was proposed as a transparent electrode with high conductivity in electrical performance, with proper transparency in optical performance, and low fabrication cost compared to a traditional transparent thin film electrode. To analyze the performance of a transparent antenna fabricated by MM, the antennas were designed to operate in the 2.4–2.5 GHz WLAN band (802.11b). The conductive metal of transparent MM patch antennas was designed using a square lattice structure and was fabricated using wired MM with copper wire (0.2–0.5 mm). In addition, micro-MM film consisting of thin copper wire ( $20~\mu \text{m}$ ) was used to fabricate transparent patch antennas. The realized gain, efficiency, front-to-back ratio, and radiation patterns of the transparent MM patch antennas are discussed for various combinations of radiator and ground planes. Overall, the transparent MM patch antennas offer optical transparency, maintain sufficient performance, and could possibly be used in wireless transparent applications.

Wearable planar inverted‐F antenna with stable characteristic and low specific absorption rate

AbstractA dual band PIFA antenna with EBG structure in application to wearable communication system is investigated in this article. The proposed antenna is designed to work at 2.4/5.8 GHz WLAN band by two horizontal radiation units, and then the dual band EBG with two rectangular rings is designed, which is quite a simple structure. The two zero‐reflection phases and band‐gaps of S21&lt;−20 dB are observed in the designed working bands. Both of the measurement and simulation show that the performance of the proposed antenna under bending condition is stable, and by virtue of the EBG structures, several significant characteristics are obtained such as the unidirectional radiation, high gain, and low SAR value, which are necessary for WBAN applications.

Mechanically pattern reconfigurable dual‐band antenna with omnidirectional/directional pattern for 2.4/5GHz WLAN application

AbstractA mechanically pattern reconfigurable dual‐band antenna with an omnidirectional radiation pattern or a directional pattern for 2.4/5GHz dual‐band WLAN application is presented. By manually rotating the top substrate, the antenna can operate at patch state or monopole state, respectively. A novel U‐gap structure consisting of an outer patch, an inner patch and a U‐shaped gap is introduced to achieve the dual band feature at both operation states. The measured overlapped bands of the two states are 2.4–2.56 GHz and 5.22–6 GHz, covering the 2.4–2.48 GHz and most of the 5.15–5.85 GHz WLAN band. The measured peak gain is 2.4 dBi at 2.5GHz, 6.2 dBi at 5.5 GHz for monopole state, and 5.8 dBi at 2.5 GHz, 7.2 dBi at 5.5 GHz for patch state.

A compact printed multistubs loaded resonator rectangular monopole antenna design for multiband wireless systems

In the present article, a compact triple-band multistubs loaded resonator printed monopole antenna is proposed. The antenna consists of a quarter wavelength two asymmetrical inverted L-shaped stubs to excite two resonant modes for 3.5/5.5 GHz bands and one integrated horizontally T-shaped stub with inverted long L-shaped stub to excite resonant mode for 2.5 GHz band. By loading these stub resonators along y-axis with distinct gaps, the antenna resonates at three frequencies 2.57/3.52/5.51 GHz covering the desired bands while keeping compact size of 24 × 30 mm2 (0.2 λ0 × 0.25 λ0). The proposed antenna is fabricated on Rogers RT/duroid 5880 substrate with thickness 0.79 mm and its performance experimentally verified. The measured results reveal that the antenna has the impedance bandwidths of about 210 MHz (2.50-2.71 GHz), 260 MHz (3.37-3.63 GHz), and 650 MHz (5.20-5.85 GHz), for 2.5/3.5/5.5 GHz WiMAX and 5.2/5.8 GHz WLAN band systems. The antenna provides omnidirectional radiation patterns and flat antenna gains over the three operating bands. In addition, the design approach and effects of multistubs resonator lengths on the operating bands are also examined and discussed in detail.

Development of PSO-ANN Ensemble Hybrid Algorithm and Its Application in Compact Crown Circular Fractal Patch Antenna Design

The traditional methods of designing antennas are not suitable in case of fractal antennas due to non availability of accurate mathematical design expressions. Recently, ANN model relating the physical and electromagnetic parameters of the fractal antenna to be designed is used as objective function of the optimization algorithm and it has been shown as an effective approach. In presented paper, ANN ensemble model has been used as the objective function of a PSO algorithm to calculate the optimal dimensions of a circular fractal antenna for desired resonant frequency. It has been established that ANN ensemble has better performance than the constituent ANN models. The design accuracy of the proposed hybrid algorithm is validated through the simulation and experimental results of the designed antenna. The size reduction capability of the proposed fractal antenna is used to design an antenna for 5.8 GHz WLAN band with a size reduction of 41.64% compared to simple circular microstrip antenna. The miniaturization of the antenna will lead to the design of compact devices for wireless communication systems.

A compact CPW‐fed antenna with fractal S‐shaped patches for multiband applications

ABSTRACTWe present the design of a novel compact coplanar waveguide‐fed antenna with fractal s‐shaped patches for multiband applications. The antenna consists of three fractal s‐shaped patches with different lengths. We demonstrate that the number of resonant frequencies is in direct proportion with the number of fractal s‐shaped patches. This is to say that, the number of resonant frequencies in a multiband antenna can be increased by increasing the number of patches. The resonant frequencies can be selected by carefully adjusting the length of the patches. We have designed our antenna to operate at 2.5/5.3/7.1/8.4 GHz. The measurement results show that the proposed antenna has 10 dB impedance bandwidths of 622 MHz (2.322–2.944 GHz), 466 MHz (5.113–5.579 GHz), 121 MHz (6.890–7.011 GHz) and 1080 MHz (8.206–9.286 GHz) to cover all the 2.4 GHz Bluetooth, 5.5 GHz WiMAX, and 2.4/5.2 GHz WLAN bands. The latter two bands of our proposed antenna fall within the X band range which finds vast applications in radar, aircraft, spacecraft and mobile or satellite communication system. The proposed antenna is printed on a single‐layered FR4 substrate, and it occupies a small volume of 17 × 18 × 1.6 mm3. The simulated and measured performance of the antenna confirms its omnidirectional radiation pattern and quad‐band operation. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:541–546, 2017

Left-handed compact MIMO antenna array based on wire spiral resonator for 5-GHz wireless applications

A compact coplanar waveguide-fed multiple-input multiple-output antenna array based on the left-handed wire loaded spiral resonators (SR) is presented. The proposed antenna consists of a 2 × 2 wire SR with two symmetrical microstrip feed lines, each line exciting a 1 × 2 wire SR. Left-handed metamaterial unit cells are placed on its reverse side and arranged in a 2 × 3 array. A reflection coefficient of less than −16 dB and mutual coupling of less than −28 dB are achieved at 5.15 GHz WLAN band.