This paper presents a new approach for design of the log-periodic dipole array antenna (LPDA) based on using of different design parameters in the LPDA elements to control the antenna behavior. In the proposed procedure, the design parameters can control the value of forward gain over the operating frequency range, and also adjust the gain flatness. Furthermore, this design procedure can decrease the LPDA dimensions in comparison to the conventional design. Based on the proposed design method, several LPDA antennas are designed and simulated numerically by the method of moment. The simulation results show that this LPDA design procedure can be a good candidate for design of optimized antenna in different frequency bands.

For further and various applications of communication systems, we lead to using the overall of electromagnetic spectrum. Also, because of the developing f multiband wireless systems, antenna designers are enforced to design antennas matched to the operation in multi-band and multi-frequency. On the other hand, nowadays, the use of light-weight, simple, small and inexpensive antennas is an essential requirement for covering multi bands. In this paper, a microstrip antenna is designed and suggested fractal-based and utilized FR4 substrate with small size and light, and also ability to resonance in multi-frequency by increasing fractal repetitions and self-similarity property. Therefore, this proposed structure causes the antenna resonance in more frequencies, and also leads to miniaturization of its size. This antenna operates in 1-10 GHz range includes five frequency resonance for the most of convenient applications. Also, it has appropriate pattern and circular polarization which increases its applications. The antenna has been fabricated and there is a good agreement between measurement results and full wave simulation using HFSS software.‏

Recently, the production of biosurfactants in bioreactors and their use in various pharmaceutical, chemical and food industries have been developed. Optimum production is directly related to the physicochemical condition of culture medium (such as pH and temperature) and engineering parameters of bioreactors (such as aeration rate, volume of operation and the amount of energy input). Understanding the gas transfer in shaken bioreactors equipped with a sterile closure is advantageous to avoid oxygen limitation or carbon dioxide inhibition of a microbial culture. In this study, the effect of aeration rates (due to using different design closures) on the amount of biosurfactin production by Bacillus subtilis ATCC 6633 in a ventilation flask as a miniaturized bioreactor was investigated. The highest biosurfactin concentration (0.0485 g/L/h) was obtained in the optimum conditions in which the amount of filling volume and shaking frequency were 15 ml and 300 rpm, respectively. The specific aeration rate (qin) and maximum oxygen transfer rate (OTR max), were calculated 1.88 vvm and 0.01 mol/L/h, respectively. The results showed the significant biosurfactin productivity increase under non-oxygen limiting condition.

One of the methods for optimizing the radiation characteristics of microstrip antennas is using metamaterial as substrate and superstrate. In this research, a rectangular microstrip antenna with circular polarization and conical pattern is designed at 2.2 GHz frequency. For creating circular polarization cutting corner method is used and to create conical pattern, 4 array rectangular microstrip patch antennas are used and each antenna is feeded by microstrip line and whole of structure is feeded by a 50 Ω SMA connector. To improve the radiation characteristics and optimize the dimensions of antenna, a 10×10 aray layer of metamaterial is used as substrate and Then the antenna has been made. The metamaterial parameters such as Permeability (µ) and Permittivity (ε) is extracted by Nicolson-Rose method. The simulation results show that the antenna dimensions is decreased 30% and bandwidth and gain of the antenna are increased 17% and 45% respectively. All the simulation process for antenna designation is implemented in HFSS 18.2 software.

This article presents a design method of miniaturized, circularly polarized (CP), concentric ring-shaped monopole on-chip antenna for 24 GHz short-range application. The proposed antenna covers automotive radar spectrum 22-29 GHz with a resonance at 24 GHz. Taking a simple circular ring-shaped patch as reference antenna, a small gap is introduced in the closed-loop structure that helps to provide the required travelling wave current distribution for realizing the CP property. Then a smaller circular ring is incorporated inside the reference antenna to improve the antenna performance in terms of CP characteristics. Finally, the proposed antenna is tuned to obtain the CP characteristics in the desired band ranging from 23.2 GHz to 27 GHz with 3-dB axial ratio (AR) bandwidth of 3.8 GHz. It offers a maximum gain of -4.5 dBi and wide angular range coverage (HPBW>75° in both E and H-plane). The standard CMOS process with only one level of mask (metal patterning) is used to realize the designed antenna. Compact in size of 3.8 mm × 4 mm × 0.678 mm, simple design layout, and its performance make the antenna as a suitable candidate for system-on-chip (SoC) application.

In this paper a miniaturized diplexer for WLAN and WiMAX applications is presented, based on half-mode substrate integrated waveguide (HMSIW) technology by loading a novel metamaterial unit-cell. The proposed metamaterial unit-cells are called fractal open complementary split-ring resonators (FCSRRs). The proposed FCSRRs behave as electric dipoles if appropriately stimulated, and are able to generate a forward-wave passband region below the cutoff frequency of the waveguide structure. The electrical size of the proposed FCSRRs unit-cell is smaller than the conventional CSRRs unit-cell. Therefore, the FCSRR unit-cell is a good candidate to miniaturize the SIW structure. The proposed diplexer has been designed by cascading two bandpass filters with different center frequencies. The HMSIW bandpass filters are implemented by etching two FCSRR unit-cells with different sizes. The design procedure is based on the theory of evanescent mode propagation in which the FCSRR unit-cells behave as electric dipoles. A forward-wave passband below the intrinsic cutoff frequency of the HMSIW structure has been achieved by loading the FCSRR unit-cells on the metal surface of the HMSIW structure. This proposed diplexer displays high selectivity and compact size by using sub-wavelength resonators. The designed diplexer has been fabricated and experimental verifications have been provided. The measured results are in a good agreement with the simulated ones. The total size of the proposed diplexer is about 0. 30 λ g × 0. 09 λ g. The proposed diplexer shows significant advantages in terms of size reduction, low loss, high selectivity, high Q-factor, easy bandpass frequency shifting, easy fabrication and easy integration with other planar microwave circuits.

In this paper a novel fractal shape structure is introduced. Application of the proposed fractal shape to a square patch antenna represents a very good reduction size in comparison to the previously reported works. To compensate for the reduction in the antenna bandwidth, which occurs during the miniaturization process, the T-probe feeding method is used. By using this feeding method, the impedance bandwidth of the antenna is increased, which makes the antenna appropriate for PCS applications in the frequency range of GSM 1900. The effects of various parameters of the feed structure on the input impedance of the antenna are also presented in this paper. In order to validate the simulation results, the antenna was fabricated. The results of testing and measurements of the fabricated antenna in the antenna Laboratory of Iran Telecommunication Research Center (ITRC) verified the simulation results.

In recent years, biosurfactants due to wide applications in chemical, petroleum, food and pharmaceutical industries, have been widely considered by researchers. Biosurfactants are produced by a series of microorganisms, so it is important to screen culture medium and operating conditions in miniaturized bioreactors prior to scaling up to large bioreactors. In this study, using a kind of miniaturized bioreactor called ventilation flask, optimal production conditions, including filling volume and shaking frequency to produce a surfactin-type biosurfactant by Bacillus subtilis ATCC 6633, were examined. Moreover, the effect of oxygen transfer rate (OTR) on the surfactin production was investigated according to Amoabediny and Buchs model.The results indicated that the maximum biomass and biosurfactant yield which obtained under optimal conditions (filling volume of 15 mL and shaking frequency of 300 rpm) were evaluated 0.3 g/L/h and 0.0485 g/L/h, respectively. Also, at the same conditions, the amount of surface tension decreased from 60.5 mN/m to 31.7 mN/m and the maximum oxygen transfer rate (OTRmax) obtained as 0.01 mol/L/h.

A low profile fractal defected ground structure (DGS) antenna is presented for super-wideband (SWB) wireless communication applications. The designed antenna covers a very wide frequency range from 1 to 27.4 GHz (impedance bandwidth of 186%) with |S11|<-10 dB. Moreover, In spite of small electrical dimension of the proposed antenna (0.11 λ× 0.11 λ), a large bandwidth dimension ratio of 15372 is resulted. The SWB operation is achieved by using fractal DGS on the ground plane to improve the impedance characteristics between adjacent resonant frequencies. The antenna consists of a 34×34×1.6 mm3 FR4 substrate with a dielectric constant of 4.4 and a narrow rectangular radiator. A multi-frequency resonance characteristic is obtained by increasing the fractal slot iterations on the ground plane. The simulation results are verified by experimental measurements. Measured data are in good agreement with the simulated results. The frequency- and time-domain characteristics of the antenna including impedance matching, far-field patterns, gain, radiation efficiency, group delay, and fidelity factor are presented and discussed. The results indicate that the antenna has good performance over the entire operating bandwidth which make it very potential candidate for integration in SWB wireless communication systems.