Optimisation and implementation for a non‐focal Rotman lens design

Abstract

Rotman lens is widely used to feed a phased array antenna to implement a beam forming network. In designing Rotman lens, one of the most important challenges is the phase error. In recent years, Rotman lens has been designed by using a non-focal idea whereas the position of ports are only optimised to reduce the phase error. Because of the unsuitable location of the ports, which causes mismatching and coupling, the previous non-focal method cannot be constructed easily. To implement the lens, a new scheme, converting three-focal Rotman lens to non-focal, is presented. By using a simple procedure, the phase error is properly reduced. To evaluate the proposed method, the non-focal Rotman lens has been implemented at 10 GHz. The simulation and measurement results illustrate that the method is implementable. Furthermore, the average improvement of the maximum phase error in the proposed lens, with five beam ports and five array ports with overall lens size of 15 × 15 cm 2 , is 36% better than the previous reported work.

A new impedance matching approach for microstrip Rotman lens based on analyzing the standing wave pattern of an electric field

“…Many researchers contributed to reduce the produced phase error in the lens. 28,31,32 Good coupling energy between the beam and receive ports with amplitude rate varying below −10 dB are indicated in Figure 8B. However, an oscillation that can be observed within the level range (−11.5 to −16.5 dB) may be due to inside reflections within the lens junction.…”

“…On the other hand, a discontinuity in the linearity can be observed due to a phase error. Many researchers contributed to reduce the produced phase error in the lens . Good coupling energy between the beam and receive ports with amplitude rate varying below −10 dB are indicated in Figure B.…”

Design and Performance Analysis of Millimetre-Wave Rotman Lens-Based Array Beamforming Networks for Large-Scale Antenna Subsystems

“…The MTLs, with the effective dielectric constant of ε e , are routed with the appropriate curvature in order to guarantee the separation and non-overlapping required for the array contour, and also to maintain the same electrical length among all the output meandered MTLs. In the generalised RL model, it is assumed that the focal angle α is equal to the scan angle θ, and although the angles can be different, by applying which, it can be used for the potential computations and optimisations regarding the compactness of the beam region and phase error reductions [35]. The following equations govern the design of the trifocal RL based on the GO, in order to maintain the performance of the device, in terms of generating multiple beams with a linear progressive phase shift across the array ports (i.e., due to the different electrical lengths between a specific beam port and all output ports), as well as preventing the array from changing the scanning direction with frequency variation, i.e., the high-performance wideband true-time-delay (TTD) operation of the microwave/mmwave lens.…”

Analytical and Numerical Evaluations of Flexible v-Band Rotman Lens Beamforming Network Performance for Conformal Wireless Subsystems

“…The inputs include the desired scan angle of the array, the operating frequency, the number of beams and array ports, and the array element spacing. The geometry optimisation, phase error and coupling analysis are also considered while designing the device, as thoroughly discussed in [23][24][25][26]. For the sake of brevity, the design equations are not provided.…”