In-band full-duplex (IBFD) technology can enable unique system capabilities and network architectures by allowing devices to transmit and receive on the same frequency at the same time. While previously considered impossible, this ability can now be used to optimize resource sharing within the crowded frequency spectrum for various communication systems, including 5G new radio. The potential of these IBFD systems can only be realized if each device incorporates a sufficient number of self-interference cancellation techniques to ensure that its receivers do not saturate. This tutorial survey offers the most comprehensive collection to date of these techniques and discusses how all of them can be implemented within the different domains of a typical transceiver. In addition, the results of a novel IBFD system study are presented for more than 50 demonstrated communication systems with more than 80 different measurement scenarios. The various system parameters are then combined into a new figure of merit, which can be used to propel future research and accelerate the inclusion of IBFD technology within an upcoming wireless standard.

In-Band Full-Duplex Technology: Techniques and Systems Survey

This expanded and thoroughly revised edition of Thomas H. Lee's acclaimed guide to the design of gigahertz RF integrated circuits features a completely new chapter on the principles of wireless systems. The chapters on low-noise amplifiers, oscillators and phase noise have been significantly expanded as well. The chapter on architectures now contains several examples of complete chip designs that bring together all the various theoretical and practical elements involved in producing a prototype chip. First Edition Hb (1998): 0-521-63061-4 First Edition Pb (1998); 0-521-63922-0

The Design of CMOS Radio-Frequency Integrated Circuits: RF CIRCUITS THROUGH THE AGES

With the rapid development of wireless communication technology, various indoor location-based services (ILBSs) have gradually penetrated into daily life. Although many other methods have been proposed to be applied to ILBS in the past decade, WiFi-based positioning techniques with a wide range of infrastructure have attracted attention in the field of wireless transmission. In this survey, the authors divide WiFi-based indoor positioning techniques into the active positioning technique and the passive positioning technique based on whether the target carries certain devices. After reviewing a large number of excellent papers in the related field, the authors make a detailed summary of these two types of positioning techniques. In addition, they also analyse the challenges and future development trends in the current technological environment.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-com.2019.1059

Survey on WiFi-based indoor positioning techniques

This communication presents two dual-polarized microstrip patch antenna systems based on a single radiating element with 180° ring hybrid coupler for differential feeding to achieve high interport RF isolation. One of the implemented single-layer patch antennas provides more than 67 dB isolation between transmit (Tx) and receive (Rx) ports at 2.4 GHz while the second fabricated antenna with slot coupled Tx port along with differential feeding for Rx operation provides more than 90 dB RF isolation at 2.41 GHz between dc isolated Tx–Rx ports. Moreover, the single-layer antenna provides better than 62 dB interport isolation for 10 dB-return loss impedance bandwidth (BW) of 50 MHz. Measured interport isolation for implemented antenna with slot coupled Tx port achieves around 70 and 79 dB port to port RF isolation for 50 and 20 MHz BWs, respectively, and these are the highest amounts of isolation for a single antenna to best of our knowledge. The antenna with slot coupled Tx port provides more interport RF isolation as compared to single-layer antenna due to low coupling between slot coupled and co-planar quarter-wave microstrip fed ports. Both antenna structures have the capability to remove in-band nonlinear self-interference (SI) components without complex SI cancellation circuits.

Dual-Polarized, Differential Fed Microstrip Patch Antennas With Very High Interport Isolation for Full-Duplex Communication

This letter presents a 2.4 GHz, dual-polarized microstrip patch antenna with extremely high interport isolation for a shared antenna architecture-based in-band full-duplex transceiver. The presented antenna configuration is based on four-ports linearly polarized single radiating element with differential feeding for both transmit $(T_{x})$ and receive $(R_{x})$ operation. The double-differential feeding using two identical 3 dB/180° ring hybrid couplers with nice amplitude and phase balance effectively suppresses the interport RF leakage to achieve very high isolation. The prototype of the proposed antenna architecture is implemented using a 1.6 mm thick general-purpose FR-4 substrate. The implemented antenna provides more than 90 and 80 dB interport RF isolation for 20 and 40 MHz bandwidths, respectively, in addition to more than 98 dB port-to-port peak isolation when measured inside an anechoic chamber. To the best of our knowledge, this is the highest amount of RF isolation reported for a single dual-polarized patch antenna.

Double-Differential-Fed, Dual-Polarized Patch Antenna With 90 dB Interport RF Isolation for a 2.4 GHz In-Band Full-Duplex Transceiver

This paper presents a novel low-complexity full-duplex radio design, which only uses a single patch antenna without any duplexer or circulator for passive suppression of self-interference, and a computationally efficient technique for linear digital cancellation. The proposed full-duplex design is tested for IEEE 802.11g Wireless Standard on the WARP (v3) software-defined radio implementation platform. It is shown that this design provides a total suppression of 88 dB, which is sufficient for low-power or short-range full-duplex communication. The dual polarized slot coupled patch antenna used in our design provides an interport isolation as high as 60 dB in 2.4 GHz band. Additionally, the digital domain cancellation utilizes a frequency domain-based estimation and reconstruction approach, which not only offers up to $61\%$ reduction in the computational complexity but also provides a $5-7$  dB better digital cancellation performance in highly selective channel conditions, as compared to the time-domain-based techniques. The proposed full-duplex implementation can be easily applied in OFDM-based wireless systems, such as IEEE 802.11, which is the considered air interface in this paper.

A Low-Complexity Full-Duplex Radio Implementation With a Single Antenna

In-band full duplex (IBFD) wireless operation can be accomplished by mitigating the self-interference (SI) at the receiver that is caused by coupling of radio-frequency power from its own transmitter. Maximum amount of SI cancellation (SIC) should be achieved at antenna stage to enable full-duplex wireless communication operation at same frequency. This study presents the design and implementation of a compact two-port dual-polarised microstrip patch antenna which uses three-port microstrip patch antenna with 3 dB ring hybrid coupler as SIC circuit to achieve high interport isolation. The implemented antenna provides 57dB interport isolation between transmit and receive ports at centre frequency of 2.5GHz with linear orthogonal polarisation and interport isolation is better than 40dB for 50MHz bandwidth. The fabricated compact microstrip patch antenna has 3.1 and 3.7 dBi gains for Tx and Rx modes, respectively. The proposed antenna has comparatively wider 10dB input bandwidth (50MHz) along with high interport isolation.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-map.2016.0329

Compact dual-polarised microstrip patch antenna with high interport isolation for 2.5 GHz in-band full-duplex wireless applications

This paper presents the design, implementation and interport isolation performance evaluation of three dual port, dual polarized 2.4GHz microstrip patch antennas. Input matching and interport isolation (both DC and RF) performance of implemented antennas has been compared by measuring the input return losses (Sii, S22) and interport isolation (S12) respectively at 2.4GHz. Two implemented single layer antennas provide around 40dB RF interport isolation while the multilayer antenna has 60dB isolation between transmit and receive ports at centre frequency with DC isolated ports. The multilayer antenna provides more than 55dB interport isolation for antenna's 10 dB input impedance bandwidth of 50MHz.

Haq Nawaz

Papers

Dual-Polarized, Differential Fed Microstrip Patch Antennas With Very High Interport Isolation for Full-Duplex Communication

Double-Differential-Fed, Dual-Polarized Patch Antenna With 90 dB Interport RF Isolation for a 2.4 GHz In-Band Full-Duplex Transceiver

A Low-Complexity Full-Duplex Radio Implementation With a Single Antenna

Compact dual-polarised microstrip patch antenna with high interport isolation for 2.5 GHz in-band full-duplex wireless applications

Three dual polarized 2.4GHz microstrip patch antennas for active antenna and in-band full duplex applications