Peng-Fa Li

Wide-Angle Scanning Phased Array Using an Efficient Decoupling Network

The active impedance of each element in a phased array changes substantially with scan angle due to mutual coupling. Therefore, a key challenge in the design of wide-angle scanning phased array is to achieve wide-angle impedance matching (WAIM). In this communication, an efficient decoupling network is developed to reduce the mutual coupling between adjacent elements for this purpose. A complete scattering matrix analysis of the decoupling network is given and the design procedure is summarized. A 1 × 16 linear microstrip phased array has been designed and fabricated for experimental verification. Good agreement is obtained between measured and simulated results. The measured mutual coupling between adjacent elements is reduced to lower than -35 dB at the center frequency. Due to the reduced mutual coupling, the array can experimentally scan to 66° with a gain reduction of only 3.04 dB.

An Efficient Decoupling Feeding Network for Microstrip Antenna Array

An efficient decoupling feeding network is proposed in this letter. It is composed of two directional couplers and two sections of transmission line for connection use. By connecting the two couplers, an indirect coupling with controlled magnitude and phase is introduced, which can be used to cancel out the direct coupling caused by space waves and surface waves between array elements. To demonstrate the method, a two-element microstrip antenna array with the proposed network has been designed, fabricated and measured. Both simulated and measured results have simultaneously proved that the proposed method presents excellent decoupling performance. The measured mutual coupling can be reduced to below -58 dB at center frequency. Meanwhile it has little influence on return loss and radiation patterns. The decoupling mechanism is simple and straightforward which can be easily applied in phased array antennas and MIMO systems.

Wideband Folded Reflectarray Using Novel Elements With High Orthogonal Polarization Isolation

A wideband folded reflectarray antenna (FRA) operating in a frequency band of 11-15 GHz is proposed in this communication. It consists of novel dual-polarization elements with high orthogonal polarization isolation. A two-layer element structure is used to control the reflection phase of two orthogonally polarized waves independently and the element presents a large phase variation of about 700° and approximately linear phase curves. Meanwhile, the multifrequency phase matching method is applied in the FRA design. A 30% bandwidth for a 1-dB gain drop, a peak aperture efficiency of 49.1%, and sidelobe levels below -14 dB are achieved. Factors with strong influences on the aperture efficiency are discussed. The simulated results are experimentally verified by an FRA prototype fed by an open-ended waveguide.

Low-Cost Periodic Sparse Cavity-Backed Phased Array Based on Multiport Elements

In this communication, an H-plane sparse cavity-backed antenna array is proposed, and by using multiport elements, the number of array control components such as transmitting/receiving modules, phase shifters, and power dividers is reduced, and therefore cost of the phased array is saved. In the array, each subarray consists of an active and a passive element, and the active element not only works as an antenna but also as a power divider to feed the passive one. A reflection-type phase shifter (RTPS) is designed and integrated between the two elements, whose phase shift is controlled by two reflective loads. The distance between the neighboring active elements is 1.225λ0 (λ0 is the free-space wavelength at the center of the operating frequency band), twice of that between the active and the passive elements. Meanwhile, cavity-backed structure is adopted to obtain unidirectional radiation patterns with high aperture efficiency. The proposed array can be used in both wide-angle scanning and limited field-of-view applications. Simulated and measured results are given and discussed to validate the proposed idea.

Microstrip Array Antenna With 2-D Steerable Focus in Near-Field Region

A microstrip planar array antenna is presented in this paper, which is designed to have near-field focused beams, and it is capable of steering its focus on the designed focal plane. The array is composed of eight series-fed linear arrays, which are able to scan the focus by frequency around 10 GHz in the H-plane, whereas, E-plane focus scan can be achieved by feeding the linear arrays with different phases. The proposed array can be used in near-field scan systems, e.g., microwave imaging system, with a faster scan rate than mechanically scanned antennas and a lower cost than array antennas with full phase control elements. Theoretical analysis is presented in this paper, and is verified by simulations and experiments.

Focused Array Antenna using subarrays

Array antennas are used in near-field-focused (NFF) applications recently. Typically Focused Array Antennas (FAA) are fed by multi-level power dividers. However, when it comes to large array antennas, the design of dividers is complicated, especially for tightly arranged arrays; also a large divider may cause large inserting loss when we use low-cost materials. A novel method is proposed in this paper to simplify the feeding network of a large FAA; subarrays are used and the array is fed on the subarray level, and the required phase distribution is realized by subarray geometry as well as the simplified divider. A 4×16 FAA working at 10 GHz with a focal distance 250mm is explored, simulated results show the new array has almost the same performance on the focal plane compared to its conventional counterpart and has no forelobe along the axial line.

Focused array antenna with 2-D steerable focus

A microstrip array antenna with near-field focused beam is presented in this paper, which is composed of eight series-fed and frequency-scanned linear arrays. The array focus can be scanned on the designed focal plane by frequency and through phase control. This array can be used in near-field fast scanning systems, with a low cost.

Sparse Focused Array Antenna Based on Subarrays

A focused array antenna (FAA) focuses its radiation power in a small spot in its Fresnel Zone. Typically an FAA is fed by a multi-level power divider. However, the bulky feed network leads to a large insertion loss and increase of complexity especially for large FAAs. A simple method to decrease the complexity of the feeding network is presented in this paper. The proposed FAA is composed of several subarrays and is fed on the subarray level. A 2 × 8 FAA working at 10 GHz is explored, the simplified FAA has similar performance but much simpler feeding network compared to a conventional one.

Sparse focused array antenna based on subarrays

A focused array antenna (FAA) focuses its radiation power in a small spot in its Fresnel Zone. Typically an FAA is fed by a multi-level power divider. However, the bulky feed network leads to a large insertion loss and increase of complexity especially for large FAAs. A simple method to decrease the complexity of the feeding network is presented in this paper. The proposed FAA is composed of several subarrays and is fed on the subarray level. A 2 × 8 FAA working at 10 GHz is explored, the simplified FAA has similar performance but much simpler feeding network compared to a conventional one.

A near-field focused array antenna with reconfigurable elements

A novel method using reconfigurable elements to design near-field focused array antenna is introduced in this paper. Compared with the traditional focused antenna, the beam-reconfigurable elements can improve the focusing gain and the focusing ability. A 6×6 focused microstrip array antenna with the focal distance of 100 mm is designed to verify the proposed design method.