Study on Waveform Characteristic for Simultaneous Transmit and Receive used in Multifunction Phased Array

Mitigating self-interference (SI) is vital for advancing simultaneous transmit and receive (STAR) systems. The noise and linearity of the canceller impose limitations on SI power handling. This article proposes a novel dual-path SI cancelling scheme for high-power SI handling. The proposed approach breaks self-interference cancellation (SIC) tradeoffs between operating frequency, SI power handling, and canceller noise/distortion by using a frequency-translated (FT) SI canceller and an auxiliary FT noise-cancelling (NC) path that cancels the noise/distortion from the primary canceller. This approach can work well for both full-duplex (FD) and frequency-division duplex (FDD) schemes. The 65-nm CMOS implementation achieves <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 45-dB SIC for 12-dBm receiver (RX) SI peak power (9-dBm avg.) with only 4-dB noise figure (NF) degradation and 207-mW power consumption at 600 MHz. The SIC approach enables a blocker-1 dB with respect to SI of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 16 dBm (8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> higher than prior work) while operating from 0.5 to 1.3 GHz. Therefore, this implementation can support watt-level SI power handling with transmitter (TX)–RX isolation <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 15 dB. This is demonstrated through measurements that show 30-dBm TX power handling with 22-dB initial isolation from the circulator.

In next generation Wireless Local Area Network (WLAN), increasing spectral efficiency is indispensable in order to provide enhanced throughput. Spectral efficiency can be increased though Simultaneous Transmit and Receive (STR) technology. In this paper, an efficient WLAN transmission scheme using STR technology is proposed. Since STR technology allows simultaneous reception while receiving, at most network throughput can be doubled. However, in order to utilize STR technology, at least two non- interfering parties are required. Railroad communication environment of busy railroad station is able to provide good STR environment with plenty number of non-interfering communication parties. Therefore, the proposed scheme is able to provide very efficient railroad communication scheme.

Theoretical performance of ideal multi-channel analog Self-Interference Cancellation (SIC) networks are considered for Simultaneous Transmit and Receive (STAR) phased array applications. Three different matching criteria are described for designing analog SIC networks, two of which may be implemented using a single cancellation path per element. Simulated results are presented comparing the performance of each SIC type under finite dynamic range limitations.

ABSTRACTSelf‐interference (SI) suppression has always been critical for simultaneous transmit and receive (STAR) systems. To address the strong coupling between nearby transmit and receive antennas, this study employs an improved quantum genetic algorithm (IQGA) to eliminate SI by combining digital self‐interference cancellation (SIC) and adaptive beamforming (ABF). Through digital SIC, both transmit noise and transmit signals are suppressed. The objective of the transceiver beamformer is to further reduce SI through SIC while simultaneously achieving high transceiver gain in the desired direction. IQGA represents the weights of feasible transceiver beams using chromosomes. By updating the population through quantum rotation, quantum crossover and quantum mutation strategies, IQGA demonstrates improvements in convergence accuracy, convergence speed, and reliability. In comparison to traditional ABF approaches, IQGA eliminates the need for complex matrix calculations and numerical derivations, thereby simplifying the solution process. The simulation results indicate that by cancelling the SI component through SIC and ABF, an isolation of 159.78 dB can be achieved at a transmit power of 1000 W. This represents an improvement of 40.32 dB compared to SIC alone and 113.87 dB compared to scenarios without SIC and ABF.

Simultaneous transmit and receive (STAR) architectures must continually improve receiver isolation techniques to support more demanding frequency agile and instantaneous RF bandwidth requirements. To ensure adequate lifetime and STAR performance, leakage signals above receive saturation levels must be suppressed to protect sensitive front end components. A commonly used technique to suppress leakage signals, known as selfinterference cancellation (SIC), can provide a sufficient level of analog isolation for full duplex operation. The adaptive self-interference canceller developed in this paper utilizes a novel transversal filter approach that passively replicates the strongly distorted transmitted signal, coupled at the receiver, for true time delay cancellation. Conventional transversal filter implementations introduce significant divider, combiner, and attenuator losses between each tap, severely limiting the synthesizable order of the multiple-path leakage channel, which effectively degrades the cancellation performance. To avoid these fixed losses, the novel transversal filter prototype incorporates a lineup of tunable coupler pairs transversely through delay lines as a theoretically lossless alternative to set amplitude and phase weighting coefficients at each tap. Minimizing transversal filter loss lessens the required coupling factor and improves insertion and power efficiency loss penalties at receive and transmit paths respectively. The loss improvements of the SIC architecture define the maximum interference power that can be cancelled. Therefore, to maximize the dynamic range of a STAR system, the SIC architecture should utilize a matching filter that balances loss, noise, and distortion. We propose a technique that provides a completely passive method to cancel strongly coupled signals up to 25 dBc below the transmitted power. The work outlines an avenue to substitute loss driven amplitude and phase weighting components with tunable reflective discontinuities, see equation (1) for a 2-tap filter expression, which can be extended to N-taps by cascading N-1 tunable coupler pairs. Analysis of the novel lossless transversal filter architecture has shown a cancellation performance of 30 dB across a125 MHz bandwidth centered at 2.4 GHz.

Continuous-phase frequency shift keying (CPFSK) is a type of frequency shift keying (FSK) that maintains phase continuity from symbol to symbol. The bandwidth efficiency of a CPFSK waveform is characterized by its modulation index, number of frequency tones and channel coding rate. These parameters can be flexibly designed to meet different bandwidth and energy requirements in wireless communication systems. One special case of CPFSK, orthogonal FSK, could be applied when bandwidth constraints are loose. By increasing the number of frequency tones, the energy efficiency can be improved at the expense of spectral efficiency. In this dissertation, the general case of orthogonal FSK, orthogonal modulation is first studied. Capacity, convergence behavior and asymptotic error rates of coded orthogonal modulation are analyzed. In addition to coherent detection, we consider noncoherent detection as well, which is one benefit of CPFSK. More often, CPFSK is designed to achieve high spectral efficiency by reducing its modulation index. The general case of nonorthogonal CPFSK is then studied. Capacity, spectral efficiency and capacity approaching code design are discussed for both coherent and noncoherent CPFSK. In addition to the system design and information theoretic issues, channel estimation for noncoherent CPFSK is considered. An iterative channel estimation, demodulation and decoding algorithm is derived using the expectation maximization (EM) algorithm. Finally, we apply noncoherent CPFSK to frequency hopping (FH) networks, leveraging the results acquired throughout the dissertation. Simulations show FH networks with CPFSK modulation and channel estimation can achieve robust performance against partial-band and multiple-access interference.

We present an actively tuned balun to enable simultaneous transmit and receive (STAR) antennas to achieve greater isolation. Specifically, for the first time, we propose placing a chip into the antenna feed to control the amplitude of the current density. Nearly perfect balance of the feed currents enables STAR antennas to maintain strong isolation despite unpredictable fabrication imperfections. Two identical prototypes were fabricated for comparison, one passive and the other with active tuning inserted. Measurements demonstrate a minimum isolation of 42 dB across a 250 MHz bandwidth, representing an 11 dB improvement over the passive case. This is the best reported transmit/receive isolation enhancement to date. Further, this novel tuning method is significant because it enables STAR antennas with low-cost substrates, such as FR-4, to achieve greater isolation than passive designs. Notably, the balun was tuned across 1.68–1.93 GHz, part of the Federal Communication Commission's AWS-3 spectrum auction. Measurements show good comparison with simulation.

A wideband monostatic simultaneous transmit and receive (STAR) antenna subsystem with high isolation and Co-horizontally polarized (Co-HP) omnidirectional radiation is presented. The antenna subsystem consists of a STAR antenna and a beamforming network (BFN). The STAR antenna consists of a planar circular array having four printed dipole elements surrounded by two groups of parasitic strips. The parasitic strips are used to improve the impedance bandwidth (IMBW) and reduce the gain variation in transmit (TX) and receive (RX) modes. To achieve high isolation, the four ports of the STAR antenna are excited with two orthogonal phase modes for TX and RX using the BFN. The BFN is a six-port network consisting of two 180&#x00B0; hybrid couplers, one 90&#x00B0; hybrid coupler, and a Wilkinson power divider. The 180&#x00B0; hybrid coupler is elaborately designed with low imbalances since it is most key to achieve high TX/RX isolation. Measured results show that the proposed STAR subsystem achieves a TX/RX overlapping IMBW of 4.71&#x2013;6.2 GHz, and a 40 dB TX/RX isolation bandwidth of 4.81&#x2013;5.88 GHz, while maintaining horizontally polarized omnidirectional radiation patterns for TX and RX over the entire operating frequency band.

Code-domain signal processing techniques implemented at radio frequencies (RFs) enable simultaneous transmit and receive (STAR) applications. With direct sequence spread spectrum (DSSS) techniques and RF correlators, transmit (TX) self-interference (SI) is separated from the receive (RX) signal at the antenna interface for STAR. The processing gain inherent in the code-domain approach increases the TX SI rejection in the RF domain to relax filtering and linearity requirements of the RX. A code-domain RX demonstrates 52 dB of TX SI rejection with TX code-notch and RX code-pass filters operating at the same center frequency. The RX is tunable from 0.25 to 1.25 GHz and has a gain of 39 dB at 1 GHz while consuming 90 mW of which 40 mW are consumed in the front-end filters. The RX is implemented in a 45-nm CMOS SOI process and full-duplex operation is verified through an over-the-air demonstration.

Simultaneous transmit and receive (STAR), also known as in-band full-duplex (IBFD), is a key enabling technology for the next-generation wireless networks operating in spectrum congested and contested environments. Transmitting (Tx) and receiving (Rx) at the same time and over the same frequency channel results in significant improvements in communication systems throughput and spectral efficiency. The chief challenge associated with STAR systems is the required high Tx/Rx isolation that may be obtained with transceivers that combine multiple layers of self-interference (SI) cancellation including digital back-end processing. Since transceivers "start and end" with apertures, the antenna layer is therefore critically important for STAR operation. Nowadays, ~40-50% of the required isolation can be achieved with a well-designed IBFD antenna subsystem inching us ever closer to meeting this, not so long ago considered impossible task. This review focuses on the role of antennas in IBFD systems. Performances of various antennas designed to cover different bandwidths, fields of view, and concepts of use are overviewed. What was deemed impossible a decade ago is now likely.

In this paper, a wideband dual-circularly polarized simultaneous transmit and receive (STAR) antenna is designed at ISM band. Four sequential rotated microstrip patch elements are excited by two sets of feeding networks: the feeding network of transmit (TX) antenna on the top side of the substrate for left hand circular polarization (LHCP), and the feeding network of receive (RX) antenna on the bottom side for right hand circular polarization (RHCP), or vice versa. The parasitic patches with an air gap are used to enlarge the gain bandwidth. The cancellation technique based on the phase cancellation and geometrical symmetry of antenna is employed. The simulation and measurement results show good agreement and demonstrate the good TX/RX isolation of greater than 35 dB across a wide bandwidth of 5–6 GHz. The TX/RX isolation reaches 48.5 dB @ 5.18 GHz, and the axial radio is better than 3 dB across the entire ISM band, which further proves the feasibility of this design methodology and the application in STAR and sensory integration.

We demonstrate a wideband scanning 4-arm spiral antenna array with high transmit/receive isolation for Simultaneous Transmit and Receive (STAR). STAR increases a channel's spectral efficiency by transmitting and receiving across the full bandwidth of a channel. To our knowledge, this is the first STAR array to demonstrate scanning across GHz bandwidths. Each 4-arm spiral element is divided into two arms for transmit and two more for receive. To suppress grating lobes, the element spacing is kept at less than λ/2. A 3×3 array prototype was fabricated and measurements agree well with simulations.

To address the limited spectrum, current communication systems employ either frequency division duplex (FDD) or time division duplex (TDD) transceivers. These duplexing techniques exploit orthogonality of the time/frequency resources, to reuse the spectrum. A popular approach for implementing full duplex communication without increasing resource utilization is the simultaneous transmit and receive (STAR) scheme. However, the implementation of STAR systems is hindered by the high power transmitted signal which inevitably couples to the receiver, causing higher interference in the band of interest. It is therefore necessary to suppress this interference. In this paper, we present the design and implementation of a 2-stage interference cancellation at the RF and analog domain. This results in 50dB suppression of the coupled signal across a wide bandwidth of 500MHz.

In this paper, in order to improve bit error performance, bandwidth efficiency and reduction of complexity compared to related schemes such as turbo codes, we combine low density parity check (LDPC) codes and continuous phase frequency shift keying (CPFSK) modulation and introduce a new scheme, called ‘low density parity check coded‐continuous phase frequency shift keying (LDPCC‐CPFSK)’. Since LDPC codes have very large Euclidean distance and use iterative decoding algorithms, they have high error correcting capacity and have very close performances to Shannon limit. In all communication systems, phase discontinuities of modulated signals result extra bandwidth requirements. Continuous phase modulation (CPM) is a powerful solution for this problem. Beside CPM provides good bandwidth efficiency; it also improves bit error performance with its memory unit. In our proposed scheme, LDPC and CPFSK, which is a special type of CPM, are considered together to improve both error performance and bandwidth efficiencies. We also obtain error performance curves of LDPCC‐CPFSK via computer simulations for both regular and irregular LDPC code. Simulation results are drawn for 4‐ary CPFSK, 8‐ary CPFSK and 16‐ary CPFSK over AWGN, Rician and Rayleigh fading channels for maximum 100 iterations, while the frame size is chosen as 504. Copyright © 2006 John Wiley &amp; Sons, Ltd.

The simultaneous transmit and receive (STAR) digital radio frequency memory (DRFM) jammer can forward and modulate the target radar signal (TRS) in real time, and the jamming effective area is significantly increased compared with the time-division DRFM jammer. However, the STAR-DRFM jammer can receive strong self-interference (SI) signals from its transmitter. If the SI signal power exceeds the receiver sensitivity of the STAR-DRFM jammer, it will affect the normal detection and reception of the STAR-DRFM jammer. Since the correlation between the SI and the TRS is very strong, if the traditional self-interference cancellation (SIC) algorithm is used, the performance of the STAR-DRFM jammer will be inferior. Therefore, this paper proposes a pseudorandom sequence (PS) assisted SIC architecture in the STAR-DRFM jammer. Next, the minimum effective jamming distance (MEJD) is introduced to measure the jamming performance of the STAR-DRFM jammer. Finally, a testbed is designed and built to verify the feasibility of the proposed algorithm. The experimental results show that the STAR-DRFM jammer have a significantly larger effective jamming area than the traditional DRFM jammer. In the STARDRFM jammer, the jamming performance of the proposed algorithm is much stronger than that of the recursive least square algorithm.