Log-periodic Array Antenna Research Articles

Metamaterial-Loaded 16-Printed Log Periodic Antenna Array for Microwave Imaging of Breast Tumor Detection

This article presents printed log periodic antennas with metamaterials for use in microwave imaging. A single layer of epsilon negative (ENG) metamaterial (MTM) array (1 × 6) of the unit cell is on the radiating patch. Adding a single negative metamaterial structure enhances the properties of far-field antennas, such as radiation pattern and gain, both of which are vital for breast imaging. Two frequency bands exhibit negative permittivity: 3–3.3 GHz and 3.6–4.5 GHz. In the operating band, the proposed antennas have achieved a maximum gain of 5.5 dBi and impedance bandwidth of 3 GHz (2–5 GHz) with a reflection coefficient less than −10 dB. At the lowest operating frequency of 2 GHz, the electrical dimensions of this designed antenna are 0.34λ × 0.26λ × 0.01λ. All 16 transceiver antennas are arranged vertically in a circular pattern around the phantom, each acting as a transmitter and the rest as receivers. The system design is carried out with the electromagnetic simulators CST and HFSS. After receiving the extracted data, the data are postprocessed using the MATLAB software and the delay multiply and sum (DMAS) imaging algorithm. Based on the reconstructed image, it is evident that the MTM-loaded antenna-based imaging system can detect many undesired tumors inside the breast phantom.

DOA Estimation Method for Ultra-Wide-Band Insect Radar Based on Variable Conical Conformal Array: Adjustable MUSIC Algorithm

Insect radar is an important tool for studying the ecological behaviors of insects. Due to the harsh environment, radar is susceptible to interference from ground echoes, which makes it difficult to monitor insects in low altitude. To study the flying insects at low altitude in radar entomology, the research of ultra-wideband (UWB) insect radar based on log-periodic antenna array was proposed. This method uses a conical conformal array to receive signals and an improved multiple signal classification (MUSIC) algorithm to process the signals. This array is capable of monitoring insects of different sizes in the ultra-wideband range, adjusting the angle of the cone tip to change the position and polarization information, and obtaining information on various insects flying at low altitude. The problem of two-dimensional angle of arrival estimation of insect cone conformal array was analyzed by computer simulation, which are low-altitude flying targets with different cone apex angles. In addition, a modified multiple signal classification algorithm was implemented to make the radar search and catch multiple targets faster and more accurate. The algorithm greatly reduces computational complexity while maintaining the accuracy of estimation. There is a linear relationship between the time calculation and the accuracy with the modified algorithm, compared with the relationship between exponential growth and the generalized MUSIC algorithm. Finally, the experimental simulation has proved the superiority of the proposed algorithm.

Modified 16-Quasi Log Periodic Antenna Array for Microwave Imaging of Breast Cancer Detection

In this paper, an effective system for microwave imaging of breast tumor detection using modified 16-planar log periodic antenna (PLPA) array is presented. The modified PLPA operates in the band from 2 to 5 GHz with stable directional patterns in the end-fire direction. Once the results of a single antenna element have been validated, the design is extended to include 16 antenna elements. All 16 transceiver antennas are vertically placed around the phantom in a circular manner where one antenna acts as a transmitter and the rest work as receivers. Delay and Sum (DAS) algorithm is used for post processing the acquired scattered signals from the sensors to reconstruct the image of the breast and to identify the existence of breast tumors. The electromagnetic simulators CST and HFSS are used to design the system, while MATLAB is used to process the data. The developed PLPA array-based microwave imaging system performs admirably, making it one of the most effective systems for detecting tumor cells.

A compensation method for the consistency of multi-channel mixing circuit for solar radio observation system

The observing frequency of Ground-based Solar Radio Observation Systems (SROS) ranges from tens of MHz (10-m-wave) to tens of GHz (millimeter-wave). Due to the limitation of the ADC input bandwidth and sampling rate, the broadband solar radio signals acquired by the SROS will be segmented by mixing circuit and then processed the analog-to-digital conversion. The analog device inconsistency leads to the inconsistencies of the amplitude and phase between different channels of mixing circuits, which affects the accuracy of the receiver. The compensation coefficient of each frequency point is first calculated by measuring the deviation of the amplitude and phase between different channels, and then stored in FPGA of the receiver. The data achieved by ADC are proceed by FFT and then compensated by the compensation coefficients. The validation experiments are carried out using 150–500 MHz SROS located in Chashan Solar Radio Observatory (CSO). The amplitude difference between different channels can be as small as 0.5 dBm. The phase consistency can also be significantly improved. The practical application shows that this method can improve the consistency of the wideband mixing circuit, and can be used to correct of multi-channel consistency of the digital beam forming (DBF) for the low-frequency log-periodic antenna array and interference of the multiple antennas.

Fast and Accurate Simulation Technique for Large Irregular Arrays

A fast full-wave simulation technique is presented for the analysis of large irregular planar arrays of identical 3-D metallic antennas. The solution method relies on the Macro Basis Functions (MBF) approach and an interpolatory technique to compute the interactions between MBFs. The Harmonic-polynomial (HARP) model is established for the near-field interactions in a modified system of coordinates. For extremely large arrays made of complex antennas, two approaches assuming a limited radius of influence for mutual coupling are considered: one is based on a sparse-matrix LU decomposition and the other one on a tessellation of the array in the form of overlapping sub-arrays. The computation of all embedded element patterns is sped up with the help of the non-uniform FFT algorithm. Extensive validations are shown for arrays of log-periodic antennas envisaged for the low-frequency SKA (Square Kilometer Array) radio-telescope. The analysis of SKA stations with such a large number of elements has not been treated yet in the literature. Validations include comparison with results obtained with commercial software and with experiments. The proposed method is particularly well suited to array synthesis, in which several orders of magnitude can be saved in terms of computation time.

SKALA, a log-periodic array antenna for the SKA-low instrument: design, simulations, tests and system considerations

The very demanding requirements of the SKA-low instrument call for a challenging antenna design capable of delivering excellence performance in radiation patterns, impedance matching, polarization purity, cost, longevity, etc. This paper is devoted to the development (design and test of first prototypes) of an active ultra-wideband antenna element for the low-frequency instrument of the SKA radio telescope. The antenna element and differential low noise amplifier described here were originally designed to cover the former SKA-low band (70-450MHz) but it is now aimed to cover the re-defined SKA-low band (50-350MHz) and furthermore the antenna is capable of performing up to 650MHz with the current design. The design is focused on maximum sensitivity in a wide field of view (+/- 45deg from zenith) and low cross-polarization ratios. Furthermore, the size and cost of the element has to be kept to a minimum as millions of these antennas will need to be deployed for the full SKA in very compact configurations. The primary focus of this paper is therefore to discuss various design implications for the SKA-low telescope.

Impedance Characteristics of Log Periodic Antenna

Log Periodic array Antenna is one of the most important and commercially used antennas for T.V. reception. It is used in VHF and UHF bands. Although the analysis of this antenna is reported in literature, the data of self impedance & mutual impedance is not fully available. But, this data is useful for the optimal design of the antenna. In view of this the array above is considered and the analysis is carried out in the present work. The computed data for Self-Impedance as a function of lengths of elements and frequency and the Mutual Impedance as a function of spacings of elements is presented.

Synchronization and combining of the radiation powers of active microwave antennas integrated with field-effect transistors

Combining of the powers of microwave generators designed as a array of log-periodic antennas on a dielectric substrate and field-effect transistors as active components is experimentally investigated. Possibilities of a substantial increase in the generation efficiency due to mutual synchronization of radiators are demonstrated, and conditions for formation of the radiation pattern are studied.

On Conditions for Constant Radiation Characteristics for Log-Periodic Array Antennas

Wide frequency band antenna systems are required for many now and future applications, such as in radio astronomy and ultrawideband (UWB) technology. Constant radiation characteristics over a decade bandwidth are required for some of wide band applications, for example, feeds for reflector antennas in radio telescope. The log-periodic array antenna is one of the technologies for wideband antennas. In the present paper, an analysis on condition for constant radiation characteristics over wide bandwidth for a log-periodic array antenna is presented. From this condition, a guide rule for designing a wideband log-periodic array antenna is obtained. The Eleven antenna, a decade bandwidth log-periodic array antenna, is selected to illustrate the condition and verify the analysis in the paper.

Radiation Characteristics of Linear Log-Periodic Dipole Array Antennas Placed Near a Lossy Ground

The radiation properties of linear log-periodic dipole array antennas placed near a finite conductivity earth is investigated analytically. A method of moment solution is developed to solve the integral equation associated with the log periodic antenna array. The effect of finite ground conductivity is taken into account by using the appropriate Green's function which is derived from the well known Sommerfeld solution of the finite conductivity semi-infinite space. Piecewise sinusoidal pulse functions are employed as describing and testing functions. In computing the mutual impedance matrix elements, Sommerfeld type integrals are encountered which are computed by applying a numerically efficient technique. After computing the current distributions on the dipole elements of the log-periodic array the far field of the antenna is computed by employing the stationary phase integration technique. Several type log-periodic dipole arrays placed near a finite conductivity ground are computed. The effects of condu...