Joint communication and radio sensing (JCAS) in millimeter wave (mmWave) systems requires the use of steerable beam. For analog antenna arrays, a single beam is typically used, which limits the sensing area to within the direction of the communication. Multibeam technology can overcome this limitation by separately generating package-level directionvarying sensing subbeams and fixed communication subbeams and then combing them coherently. In this paper, we investigate the optimal combination of the two subbeams and the quantization of the beamforming (BF) vector that generates the combined beam. When either full channel matrix or only the angle of departure (AoD) of the dominating line-of-sight (LOS) path is known at the transmitter, we derive closed-form expressions for the optimal combining coefficients that maximize the received communication signal power. For quantization of the BF vector, we focus on the two-phase-shifter array where two phase shifters are used to represent each BF weight. We propose novel joint quantization methods by combining the codebooks of the two phase shifters. The mean squared quantization error is derived for various quantization methods. Extensive simulation results validate the accuracy of the analytical results and the effectiveness of the proposed multibeam optimization and joint quantization methods.
A compact filtering antenna with high band-edge gain selectivity using a composite right-/left-handed (CRLH) resonator and a defected ground structure is presented. The CRLH resonator resonates at the zeroth-order mode and acts as the first stage of the corresponding filter; an octagonal patch acts as a radiator as well as the last stage of the filter. The design procedure follows the circuit approach -synthesis of bandpass filters. The filtering antenna has two poles in the passband and two radiation nulls (zeros) at the band edges. Compared to the conventional patch antenna, the proposed filtering antenna, with little extra circuit area, has flat gain response within the passband, good selectivity at the passband edge and wider bandwidth. Measurement results show that the filtering antenna can operate at 5.29 GHz, has a 430 MHz bandwidth and a 2.5 dBi antenna gain in the broadside (+Z ) direction within the passband.Introduction: In modern wireless communication technology, one of the issues is integrating multiple functional circuitries into one device to achieve miniaturisation and improved performance. The filtering antenna is a new concept that could realise both filtering and radiation functions, which avoids designing the antenna and the bandpass filter separately, and achieves the more compact devices and improves the performance of microwave front ends. Different from direct connection of the filter and the antenna by an extra impedance transformation structure, several studies on filtering antenna design which follow the filter synthesis that the antenna acts as one of the resonators have been presented in [1][2][3][4][5], such as a fan-shaped patch antenna with a circular openloop resonator [1], a U-shaped patch antenna with a T-shaped resonator [2], an Γ-shaped antenna with a coupled line resonator [3], an Γ-shaped antenna with two square open-loop resonators [4] and an inverted-L antenna with parallel coupled microstrip line sections [5].In this Letter, using a miniaturised composite right/left-handed (CRLH) resonator and an octagonal patch antenna with a defected ground structure (DGS), a new compact two-pole filtering antenna is proposed (Fig. 1). The CRLH resonator consists of an inter-digital capacitor and four metallic vias, resonating at zeroth-order mode, so that the size of the structure could be more flexible and compact than the conventional half-wavelength resonator. The octagonal patch antenna with the DGS acts as a radiator as well as the second resonator. The filtering antenna has a flat gain response within the passband and good selectivity at the passband edge. The measured results are in good agreement with the simulated ones.
Theory of characteristic modes (TCM) can provide physical insight into the radiation mechanism of arbitrarily-shaped electromagnetic objects. However, how to compute the characteristic modes (CMs) of different structures is still an open problem. Even for the calculation of CMs of an isolated dielectric body, there are eleven integral equation (IE)-based formulations which result in different modal solutions. Such kind of non-uniqueness of solutions makes CMs community confused. One of the objectives of this paper is to outline the differences among all existing IE-based formulations for the CMs of dielectric bodies. The existing formulations are briefly reviewed and carefully compared. We present a procedure to implement the different formulations in a unified manner. Then, we make a complete comparison of the numerical results of existing methods for a dielectric cylinder, which also serves as cross-validation for these approaches. We hope that this paper will help researchers understand the calculation of CMs of dielectric bodies and explore the computation methods of CMs for more complex objects.
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