In this paper theoretical and experimental investigation of a right hand circularly polarized microstrip rectangular patch antenna have been presented. The antenna has a coaxial feed and designed for operating at L1 frequency (1575 MHz) of global positioning systems (GPS). The antenna have been simulated and optimized using the HP-HFSS software in combination with Empipe3D. The inherently narrow bandwidth of the antenna was increased to 70 MHz using an air layer. A useful practical method was proposed in order to minimizing the input VSWR of the antenna. Theoretical and measured results have been presented and compared.

The U-slot micro-strip patch antennas were originally developed for bandwidth broadening applications. This study presents a transmission line feed to modify the U-slot stacked rectangular micro-strip patch antenna forUltra-Wide Band (UWB) communications. The modified antenna has a U-cut loaded with parallel slits and cornerslots and is printed on a dielectric substrate of FR4 with relative permittivity (ε r) of 4. 4, the thickness of 1. 59 mmand the tangent loss of 0. 025. The results show that the proposed antenna achieves an impedance bandwidth of11. 55 GHz (2. 1 – 13. 65 GHz) with the return loss < (-10) dB. This antenna can be employed for ultra-widebandapplications in S Band, C Band and X Band. The proposed patch antenna is designed and simulated by using IE3D14. 0 software. Simulation results are presented in terms of the resonant frequency, the return loss, VSWR, theimpedance bandwidth and the impedance matching.

A broadband microstrip antenna based on log periodic technique was conceived and demonstrated practically. The antenna exhibits a wideband characteristic comparing with other microstrip antennas. Over the operation frequency range, i.e.2.5-6 GHz, a 50 W input impedance has been considered.

This paper presents the design and construction of an apparatus in an RF ion source for automatic impedance matching between variable impedance environment (plasma) and fixed impedance system (an RF power generator) in order to transfer a maximum power to the plasma. The apparatus includes a matching box, a directional coupler and a balanced antenna associated with a transmission line transformer (TLT). The constructed automatic matching system is very simple and at the same time is capable of functioning under different conditions of the gas pressure to ensure a good performance. The matching network is mainly designed in order to be used in the first electrostatic accelerator designed and constructed in NSTIR, where the RF ion source is placed in the HV terminal, where there is no access to a manual matching box during the operation. The measured output current of the ion source is about 700 mA with 200 WRF power input in the working frequency of 70MHz. The output current of the previous ion source current could not exceed 200 mA under the same condition (10-2 Torr) without employing the present matching system. The system is capable of reaching an optimum VSWR point of about 1.2 in the pressure range of 10-1 to 10-4 Torr. This can be realized in a short matching convergence time (i.e., couple of seconds).

In this paper, an ultra-low-noise amplifier with frequency band switching capability is designed, simulated and fabricated. The two frequency ranges of this amplifier consist of the 2. 4 to 2. 5 GHz and 3. 1 GHz to 3. 15 GHz frequency bands. The designed amplifier has a noise figure of less than 1dB, a minimum gain of 23 dB and a VSWR of less than 2 in the whole frequency band. The design process starts with increasing the stability factor in the source through manipulating the inductor placement technique. Then the input and output matching circuits for the first frequency band are designed. This process is completed by utilizing two similar stages placed successively in order to achieve the desired gain level. Since no degradation of the noise figure is observed and acceptable values are also obtained for other parameters, switching the elements in the output matching circuit can be a good idea for avoiding the use of a similar circuit for the second frequency band. The optimum secondary values for the mentioned elements are obtained through the analyses performed using the ADS software. For changing the values of the mentioned elements two MOSFETs are used for adding capacitance and inductance to the matching circuit. In the next step, the designed amplifier is finalized and optimized after adding a suitable bias circuit to it. Moreover, The designed amplifier is fabricated and a good agreement between the measurement, analysis, and simulation results is observed.

A new design of coplanar waveguide (CPW)-fed antenna with circular polarization (CP) and excellent impedance matching is presented. In this design a pair of circular-shaped slits is applied to opposite corners of the slot for enhancing the impedance matching and realizing bandwidth of 134. 43 % across 2. 98-15. 20 GHz for VSWR ≤ 2. Furthermore, this structure exhibits axial ration bandwidth (ARBW) of 36. 22 % across 4. 43-6. 39 GHz by embedding two inverted L-shaped ground arms in the slot. The total dimension of the proposed antenna is 25 × 25 × 0. 8 mm3. This new design has advantages of, supporting the ultra-wideband (UWB) systems and covering the WLAN spectrums with 3 dB CP radiation and VSWR ≤ 2 simultaneously. The numerical and experimental results of the antenna explain the superiority of the proposed antenna performance in comparison with recent similar works.

This paper presents a new wide-band CPW Vivaldi antenna for breast tumor detection. First, a simple CPW-fed Vivaldi antenna is designed based on two-term exponential equations. The coefficient of the exponential terms and the parameters of the antenna fed are optimized for the best impedance matching at the UWB frequency band. Then, peripheral slots are added to the antenna to improve the impedance matching and gain. A prototype of this antenna is fabricated, and the scattering parameters and radiation patterns are measured. The proposed antenna achieves a wide bandwidth of 2.9–10.8 GHz with a VSWR < 3.5 and 4.2–10.2 GHz with a VSWR < 2, along with a peak gain exceeding 1 dBi. Finally, microwave imaging with the help of six samples of the proposed antenna is done. An image of a cancerous tissue inside a breast is reconstructed using the delay and sum method, successfully detecting a 20 mm spherical tumor. All the results show that a suitable antenna for a microwave imaging system is proposed.

circularly-polarized antenna is built based on new SIW(substrate integrated waveguide) structure which contains cavity-backed resonator and a conventional polarized ring with two square slits in inner and outer ring that differ 90° at position and is proposed for right-handed circular polarization (RHCP) and fabricated in two separate layers. A broadband impedance bandwidth of 13.9% and a RHCP axial ratio of 0.5GHz have been obtained under the condition of less than VSWR ≤2 and axial ratio≤ 3 dB, respectively.

This paper presents a novel implementation of an electromagnetically coupled patch antenna using air gap filled substrates to achieve the maximum bandwidth. We also propose an efficient modeling technique using the FDTD method which can substantially reduce the simulation cost for modeling the structure. The simulated results have been compared with measurement to show the broadband behavior of the antenna and the accuracy of the proposed modeling technique. The measured results show a 16% of VSWR<2 bandwidth which is considerable considering the inherent bandwidth limitations in microstrip antenna technology.

A new design of Microsrtip patch fractal antenna for 2.5 GHz is proposed which possess an excellent size reduction possibility with good radiation performance for wireless applications like Wireless Local Area Network (WLAN). The design and simulation results of microstrip patch fractal antenna using An soft HFSS is presented which has S11<-10 dB (VSWR<2). The antenna is designed based on the transmission line model with the input impedance of 50 ohm. The fractal geometry for the conventional antenna is generated up to second iteration. The results show that size reduction of 51.9% can be achieved as compared to conventional patch antenna.