Characteristic-Mode-Based Design of Planar In-Band Full-Duplex Antennas

Abstract

In-band full-duplex radios demand simultaneous transmit and receive (STAR) antennas with high isolation, compact and ultra-low profiles, and simple feed networks. Current state-of-the-art designs rarely meet all of these requirements at the same time. In this paper, we present a characteristicmode-based design approach to achieve high isolation using compact fully-planar STAR antennas with a simple feed structure. The proposed method utilizes two characteristic modes of a conducting object as transmit and receive chains to achieve high isolation without a complicated self-interference cancellation circuit. The design example in this work is fully-planar, and it has a physical height of 1.6 mm. The measured −10 dB overlapped |S11| and |S22| fractional bandwidth of this STAR antenna is 2.5% and the measured isolation between the transmit and receive ports is greater than 30 dB over the entire frequency band of operation. Index Terms-Characteristic mode theory, in-band full-duplex antennas, in-band full-duplex radios, low-profile antennas, and simultaneous transmit and receive (STAR) antennas.

Antenna/Propagation Domain Self-Interference Cancellation (SIC) for In-Band Full-Duplex Wireless Communication Systems

“…At last, there are also a few examples of achieving SIC by exciting a pair of orthogonal characteristic modes on one antenna with different feed positions. For example, as shown in Figure 14, reference [87] presents the current distributions and radiation patterns of seven modes of a patch antenna. By exciting the two dominant characteristic modes with orthogonal polarizations, i.e., mode 1 and mode 2, an isolation of more than 30 dB between the two modes is achieved.…”

A Wideband L-Probe Fed Conformal Antenna Array Using Metasurface

“…The MS ranges from 0 to 1, where MS = 1 means that the mode resonates and radiates with the maximal efficiency and MS = 0 means the mode hardly resonates and radiates. When the MS value of a mode is within 0.707~1, that mode is considered significant, which is suitable for antenna design [34]. An array of 4×4 square patches etched on the top surface of the F4b substrate constructs the MTS.…”

Co-Circularly Polarized Planar Antenna With Highly Decoupled Ports for S-Band Full Duplex Applications

“…So far, various SIC techniques have been investigated to clinch elevated levels of interport isolation for antennas intended for IBFD applications [13][14][15][16][17][18][19][20][21][22][23][24][25]. The SIC techniques include the path loss decoupling based on spatial separation of antennas elements [13], isolation through uncorrelated dual polarized T x and R x signals [14][15][16][17][18][19], suppression of SI through near field cancellation i.e.…”

“…The SIC techniques include the path loss decoupling based on spatial separation of antennas elements [13], isolation through uncorrelated dual polarized T x and R x signals [14][15][16][17][18][19], suppression of SI through near field cancellation i.e. near field SIC [20][21][22], and other topologies based on characteristics modes and different polarizations for T x and R x modes [23][24][25]. The path loss based isolation termed as spatial duplexing acquires the decoupling between T x and R x ports of IBFD antenna by increased spacing between T x and R x antenna elements or through separation of very narrow directional beams from respective antennas.…”