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This paper presents the design and the experimental demonstration of transmission of spectrally efficient frequency division multiplexing (SEFDM) signals, using a single 5-GHz channel, from 81 to 86 GHz in the E-band frequency allocation. A purpose-built E-band SEFDM experimental demonstrator, consisting of transmitter and receiver GaAs microwave integrated circuits, along with a complete chain of digital signal processing is explained. Solutions are proposed to solve the channel and phase offset estimation and equalization issues, which arise from the well-known intercarrier interference between the SEFDM signal subcarriers. This paper shows the highest transmission rate of 12 Gb/s over a bandwidth varying between 2.67 to 4 GHz depending on the compression level of the SEFDM signals, which results in a spectral efficiency improvement by up to 50%, compared to the conventional orthogonal frequency division multiplexing modulation format. [ABSTRACT FROM AUTHOR]

When two filters are cascaded together, unwanted spikes appear in the rejection region. These spikes can have a strong impact on the rejection performance of the resulting filter. Therefore, it is desired to suppress or move them far away from the operational band, including part of the rejection band as well. This paper addresses a systematic evaluation of such phenomenon and proposes a simple yet effective method, called spike envelope curve, to have, in a single run and for any frequency, the worst possible case, without the need of repeating onerous analyses. It is also shown that a judicious choice of the length and losses of the line separating the filters can be exploited to mitigate considerably such a negative effect. The method is assessed by full-wave simulations and measurements. [ABSTRACT FROM AUTHOR]

The effects of electrode configuration on body channel communication (BCC) are studied for the development of body channel characteristics, such as frequency response, path loss, and resilience to other interferers. First, this paper introduces nine types of electrode configurations according to the arrangement and direction of both transmitting and receiving electrodes on the body. Each configuration is then modeled by means of vertical and horizontal electric dipoles. From Maxwell’s equations, the complete equations of vertical and horizontal electric fields on the human body, followed by the ratios of the received electric field to the transmitted electric field, are obtained to find the theoretical body channel characteristics and the effect of electrode configurations on the body channel. The theory is verified with measurement results using a network analyzer and balun transformer. In addition to the channel characteristics, the influence of BCC and RF interference on the body channel is investigated and discussed along with receiving electrode configurations. Based on the measurement results, we found that vertical electrodes in the transmitter and horizontal electrodes with longitudinal direction in the receiver is the optimal configuration for BCC in regard to transmission gain, environmental sensitivity, and interference resilience. Finally, we suggest an effective parameter for BCC, which is equivalent reference distance to determine the proper electrode size for the required frequency response. The relation between the parameter and the electrode size is formulated for the purpose of proper electrode utilization in the design of BCC systems as well as in many potential applications. [ABSTRACT FROM AUTHOR]

The transmitter (TX)-induced interference due to power amplifier nonlinearities poses severe desensitization problems to the receiver chain in frequency-division duplexing transceivers. Due to nonlinear signal process involved, a high sampling rate is normally required in the existing digital suppression approaches, which can result in high cost and high power consumption in wideband systems. In this paper, a new digital suppression model is proposed to cancel the TX leakage at baseband with a low sampling rate. The cancellation model is based on the modified decomposed vector rotation model. With the addition of cross-term products, the enhanced model is capable of eliminating the aliasing effect arising from the reduced sampling rate. Theoretical analysis of aliasing elimination is presented, and the algorithm is subsequently verified by both simulation and experiment results, confirming the effectiveness and feasibility of the proposed cancellation technique for TX leakage suppression. Compared with conventional solutions, the new approach uses much less hardware resource and consumes much lower power while achieving comparable performance. [ABSTRACT FROM PUBLISHER]

In this paper, active synthetic band-stop filter (BSF) for interference rejection at 2–4, 4–8, and 8–16 GHz are presented. In the designs, a sharp notch, typically less than −50 dB for the entire frequency bands, is synthesized by subtracting the bandpass filter output from the all-pass (AP) output. The proposed synthetic notch filters allow optimization of filter dynamic range (DR) in the AP amplifier and frequency selectivity in the BPF independently, breaking the tradeoff between selectivity and DR ingrained in passive filters. In addition, the notch attenuation can be controlled independently of the filter bandwidth and center frequency tuning, providing more operational flexibility in suppressing blocker under a dynamic interference environment. The notch filters are fabricated in a 0.13- \mu \textm SiGe BiCMOS technology. The measured gain is 0–1 dB for all three filters. The 2–4 GHz notch filter shows a 12–13 dB noise figure (NF) and a $- 2\sim -1.5$ dBm input 1-dB compression point (IP $_{{-1\text {dB}}} ) in the passband while drawing 20–30 mA from a 3.3-V supply. For the 4–8-GHz design, the measurement shows a 8–10-dB NF and a −1–1 dBm IP -1\text {dB} in the passband at the expense of 20–27.6 mA from a 3.3 V supply. For the 8–16 GHz filter, the measured NF is 14–17 dB and the IP -1\text {dB} is 0–4 dBm with a 70–90 mW dc power dissipation. The die areas are $0.68 \times 0.72$ mm2, $0.63 \times 0.63$ mm2, and $0.62\times 0.57$ mm2 for the S-band, C-band, and X-/Ku-band filters, respectively. [ABSTRACT FROM AUTHOR]

This paper summarizes the development of safety-of-life receivers for global navigation satellite systems. Two receiver systems have been successfully fabricated, integrated, and tested by means of field experiments. Implementation issues of these two systems are described in this paper. The third generation of this receiving system is based on a dual-band approach with antennas that are able to separate two frequency bands using two outputs. Measured results show that high isolation between the two bands can be achieved. [ABSTRACT FROM AUTHOR]

Passive intermodulation (PIM) often limits the performance of communication systems with analog and digitally modulated signals and especially of systems supporting multiple carriers. Since the origins of the apparently multiple physical sources of nonlinearity causing PIM are not fully understood, the behavioral models are frequently used to describe the process of PIM generation. In this paper, a polynomial model of memoryless nonlinearity is deduced from PIM measurements of a microstrip line with distributed nonlinearity with two-tone CW signals. The analytical model of nonlinearity is incorporated in Keysight Technology’s ADS simulator to evaluate the metrics of signal fidelity in the receive band for analog and digitally modulated signals. PIM-induced distortion and cross-band interference with modulated signals are compared with those with two-tone CW signals. It is shown that conventional metrics can be applied to quantify the effect of distributed nonlinearities on signal fidelity. It is found that the two-tone CW test provides a worst-case estimate of cross-band interference for two-carrier modulated signals, whereas, with a three-carrier signal, PIM interference in the receive band is noticeably overestimated. The simulated constellation diagrams for QPSK signals demonstrate that PIM interference exhibits the distinctive signatures of correlated distortion and this indicates that there are opportunities for mitigating PIM interference and that PIM interference cannot be treated as noise. One of the interesting results is that PIM distortion on a transmission line results in asymmetrical regrowth of output PIM interference for modulated signals. [ABSTRACT FROM PUBLISHER]

Carrier aggregation transmissions in frequency division duplexing devices reduce the duplexing distance between the transmitter (TX) and receiver (RX) bands. As a consequence, the spurious intermodulation distortion products created by the nonlinear RF front-end of the TX may easily extend over to the RX band, potentially causing own RX desensitization. In this paper, we propose an efficient and computationally feasible adaptive digital identification and cancellation technique to mitigate the RX desensitization. We first show that the spurious leakage signal at own RX band depends on an equivalent leakage channel that models the overall signal leakage path including the TX nonlinearities, duplexer filter responses, and RX path. The parameters of the equivalent leakage channel can be efficiently estimated with the least squares or the recursive least squares algorithm, using the actual digital transmit data as a reference, and then used to regenerate and cancel the leakage interference from the received signal. The performance of the proposed technique is evaluated with extensive computer simulations, as well as with practical real-world RF measurements, demonstrating excellent calibration properties with up to 19-dB improvement in singal-to-interference plus noise ratio of the desired received signal. [ABSTRACT FROM PUBLISHER]

In this paper, novel blind identification and compensation architectures for the frequency response mismatch of a two-channel time-interleaved analog-to-digital-converter (TI-ADC) are proposed. First, detailed modeling of the frequency response mismatch is carried out, establishing a direct connection and similarity to the well-known in-phase/quadrature mismatch problem. Stemming from this modeling, the proposed blind mismatch identification and compensation architectures are then developed building on complex statistical signal processing. Compared to the existing methods in the literature, the proposed solutions can identify and correct the frequency response mismatch in a fully blind manner for the full digital bandwidth (BW) of the ADC system, and are also applicable in sub-sampling TI-ADC devices and RF sampling. The efficiency of the proposed solutions is verified and demonstrated using comprehensive measurements of actual RF-sampling TI-ADC hardware with gigahertz-scale instantaneous BW. [ABSTRACT FROM AUTHOR]

Motivated by advanced-generation signals and corresponding trends for multiband, broadband, and ultra-wideband transmitters, several models have recently been proposed for digital predistortion in a dual-band concurrent transmission. These state-of-the-art models assume that two frequencies of operation are uncorrelated and harmonic products can be filtered out. However, when the harmonic of one signal falls on the frequency band of another signal, it cannot be removed with filters. This paper proposes a 3-D harmonic memory polynomial based model for the dual-band concurrent transmission in the presence of harmonic interferences. The model is extracted and predistortion is implemented using a low-cost field-programmable gate-array-based system including a transmitter and a feedback receiver. Using the proposed model, a performance improvement up to 22 dB in terms of normalized mean square error and performance improvement up to 20 dB in terms of the adjacent channel power ratio is achieved compared to a conventional dual-band memory polynomial model not including harmonics. [ABSTRACT FROM AUTHOR]

A new microwave device called the cascaded type of coupled resonator decoupling network (C-CRDN) is proposed in this paper. The four-port device can be used to reduce the interference between two radio systems that work in adjacent or even contiguous frequency bands. A C-CRDN is cascaded between the two antennas to be decoupled and the I/O ports of their radio systems, respectively. The coupling matrix of a C-CRDN can be designed to meet the required isolation and return-loss specifications. To prove the concept, a fourth- and sixth-order C-CRDN using coaxial combline cavities are designed, fabricated, and measured according to the characteristics of a testing array that consists of two high-gain sleeve dipoles working in the adjacent time-division long-term evolution and wireless fidelity bands. The measured results have demonstrated that the proposed C-CRDN can effectively mitigate the coexistence interference between the two collocated systems by providing at least 20-dB isolation improvement and enhanced matching performance. The proposed technique is general and can find many applications in heterogeneous wireless systems. [ABSTRACT FROM AUTHOR]

An early characterization of integrated circuit passive isolation structures is crucial to predict their performance and effectiveness in minimizing substrate coupling. In this paper, an electromagnetic (EM) modeling methodology is proposed, which can be applied to different types of isolation structures based on interference blocking. It consists in characterizing the different doping profiles by identifying those propagation modes with a greater contribution to substrate coupling and to the aggressor-victim transfer function. This allows a fast EM characterization, providing insight on the different isolation mechanisms, identification of transitory effects, and a fast prediction of isolation effectiveness. [ABSTRACT FROM PUBLISHER]

A transmitter (TX) leakage canceller is proposed for improving the dynamic range of the receiver (RX) for wideband code division multiple access applications. A TX leakage canceller circuit in this paper is simple in implementation and has low noise figure (NF) contribution. It is a feed-forward canceller that samples a reference signal from the TX output and injects the amplitude-adjusted and phase-rotated signal to the RX chain. The canceller circuit is integrated with a low-noise amplifier and implemented in a 0.18-\mu\m CMOS technology. A cancellation of 23 dB is achieved with only 10-mA current consumption increase and low NF increase. [ABSTRACT FROM PUBLISHER]

In this paper, the mechanisms that lead to the conversion of common-mode (CM) RF interference (RFI) into differential-mode (DM) disturbances, which corrupt the information content of nominal signals and impair the operation of electronic systems, are investigated. To this purpose, distributed and lumped common-mode into differential-mode (CM-DM) conversion mechanisms are discussed with reference to a simple test structure that can be analytically described. On the basis of the proposed analysis, the origin and the relative impact of such mechanisms is highlighted and the detrimental effect of distributed CM-DM conversion on the effectiveness of differential RFI suppressing filters is discussed. Theoretical predictions are compared with experimental results. [ABSTRACT FROM AUTHOR]

Exposed to strong cochannel/adjacent-channel interference, digital multiple-input–multiple-output (MIMO) receivers require high-dynamic-range analog-to-digital converters (ADCs). Hybrid beamforming featuring spatial filtering before the ADCs can adaptively mitigate interference in both the analog and digital domains; hence relaxing the required dynamic ranges of the ADCs. This article demonstrates the effectiveness of hybrid beamforming in this mitigation utilizing adaptive minimum mean square error (MMSE) and error vector magnitude (EVM) as an optimization criterion. Extensive EVM measurements are carried out with a conductive setup using a four-element 22-nm FD-SOI CMOS prototype MIMO receiver chip to verify the performance of the adaptive MMSE algorithm. Over-the-air (OTA) measurements with a linear four-element dipole antenna array with half-wavelength spacing in the 2.4-GHz industrial scientific and medical (ISM) band quantify the improvement for real-world scenarios, e.g., having a multipath propagation channel and mutual coupling between the antenna array elements. OTA results show that a rejection of 22.5 and 24.5 dB can be achieved on average in an in-door laboratory environment utilizing vector modulator (VM) constellations with 16 and 64 points, respectively. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive survey of the literature on self-interference (SI) in long-term evolution advanced (LTE-A) and fifth-generation (5G) new radio transceivers and should serve the reader as a guide and starting point for further work on SI management. Current trends in cellular transceiver designs are discussed, and reasons why new technologies, such as carrier aggregation, cause potential sensitivity degradation due to self-interfering signals are highlighted. The survey provides an overview of the most common interference mechanisms and continues with a taxonomy on SI mitigation architectures by comparing the strengths and weaknesses of various techniques. [ABSTRACT FROM AUTHOR]

In spite of the FCC regulations, the coexistence of ultra-wideband (UWB) and narrowband (NB) systems is still an unsolved challenge. A UWB transmitter (TX) can severely degrade the performance of an IEEE 802.11a system. In this paper, a fully integrated analog impulse-radio UWB TX is presented that generates a novel UWB pulse with a tunable notch at the frequency of IEEE 802.11a system. The pulse has a 5.5-GHz bandwidth (BW), which makes it suitable for high-resolution high data-rate applications. The TX has a maximum pulse rate of 400 Mpulse/s and energy of 65 pJ/pulse with a power supply of 1.2 V. The measurement results show that the pulse has a 30-dB notch, and the TX power inside the BW of the NB system is less than -\78 dBm/MHz. The TX has a biphase modulation and has been fabricated in a 90-nm CMOS process. The proposed pulse meets the Federal Communications Commission mask for UWB systems. [ABSTRACT FROM AUTHOR]

This paper presents a 77-GHz CMOS frequency-modulated continuous-wave (FMCW) frequency synthesizer with the capability of reconfigurable chirps. The frequency-sweep range and sweep time of the chirp signals can be reconfigured every cycle such that the frequency-hopping random chirp signal can be realized for an FMCW radar transceiver. The frequency synthesizer adopts the fractional-N phase-locked-loop technique and is fully integrated in TSMC 65-nm digital CMOS technology. The silicon area of the synthesizer is 0.65 mm \times 0.45 mm and it consumes 51.3 mW of power. The measured output phase noise of the synthesizer is -85.1 dBc/Hz at 1-MHz offset and the root-mean-square modulation frequency error is smaller than 73 kHz. [ABSTRACT FROM PUBLISHER]

Transceivers operating in frequency division duplex experience a transmitter leakage (TxL) signal into the receiver due to the limited duplexer stopband isolation. This TxL signal in combination with the second-order nonlinearity of the receive mixer may lead to a baseband (BB) second-order intermodulation distortion (IMD2) with twice the transmit signal bandwidth. In direct conversion receivers, this nonlinear IMD2 interference may cause a severe signal-to-interference-plus-noise ratio degradation of the wanted receive signal. This contribution presents a nonlinear Wiener model recursive-least-squares (RLS) type adaptive filter for the cancellation of the IMD2 interference in the digital BB. The included channel-select filter and dc-notch filter at the output of the proposed adaptive filter ensure that the provided IMD2 replica includes the receiver front-end filtering. A second, robust version of the nonlinear recursive-least-squares (RLS) algorithm is derived which provides numerical stability for highly correlated input signals that arise in, e.g., Long-Term Evolution (LTE)-Advanced intra-band multi-cluster transmission scenarios. The performance of the proposed algorithms is evaluated by numerical simulations and by measurement data. [ABSTRACT FROM AUTHOR]

In this paper we present a comprehensive simulation framework that can accurately simulate our indoor UWB positioning system including the analog front-ends, digital back-ends, and channel effects. Experimental results from our UWB positioning system are compared to simulated results to validate the accuracy of the simulation framework. Simulated results illustrate the design decisions made in optimizing overall system performance. Multiple peak detection algorithms are presented, and the robustness of our leading-edge detection algorithm is shown even in dense multipath environments. Geometric effects are examined by simulating various base station configurations. This comprehensive simulation framework provides an in-depth analysis of our UWB positioning system and also provides a general framework for rapid prototyping and design of complex wireless systems. [ABSTRACT FROM AUTHOR]

In this paper, we propose a 2-D electircal interferometer as a means of high-speed data conversion. The structure is based on wave propagation in 2-D LC lattices. We will discuss the principle behind this technique, which exploits wave propagation and medium manipulation in order to take advantage of different interference patterns. This method of quantization is based on passive LC lattices that can operate at very high frequencies on a conventional CMOS process. We analyze different properties of the structure and propose the design methodology. To show the feasibility of this approach, we design a 20-GS/s 4-bit quantizer consuming 194 mW for quanization and 943 mW for an analog memory. There is good agreement between analysis and simulation. [ABSTRACT FROM PUBLISHER]

Ultra-wideband (UWB) is an effective technique that enables coexistence with other radio systems using very short pulses and spread spectrum. However, there are potential interferences among those using the same frequency bands. This paper discusses the effects of interference between pulse-based UWB (p-UWB) and other systems: continuous wave, binary phase-shift keying signal, IEEE802.11a wireless LAN using a 5-GHz band, and multiband orthogonal frequency-division multiplexing (MB-OFDM). The MB-OFDM is inferentially proposed for personal area networks, as is p-UWB. The FCC has stated that both p-UWB and MB-OFDM systems will use the same band from 3.1 to 10.6 GHz. The bit-error-rate performance is shown assuming that p-UWB and the other systems are utilized at close range. To mitigate the effects of interference to p-UWB from other radio systems, a multicarrier template wave technique is proposed. The multicarrier template wave is approximated with an ordinary pulse waveform by Gabor transform formula and is composed of several subband pulses without interfering bands. The proposed UWB receiver for MB-OFDM interferences can detect their hopping pattern without a priori knowledge from the MB-OFDM transmitter. These techniques are shown to be effective for the systems to coexist. [ABSTRACT FROM PUBLISHER]

We present the first experimental demonstration of an integrated microwave photonic circuit for active, analog self-interference cancellation. The circuit is unique in its ability to operate in any radio frequency (RF) band from 400 MHz up to 6 GHz while not requiring any optical inputs or outputs. We focus on two topics related to the functional performance of the circuit. First, we investigate the amount of interference cancellation that can be achieved over a wide range of operating frequencies. We show that the circuit can achieve nearly −30 dB of interference cancellation across all existing frequency-division duplexed local thermal equilibrium and WiFi bands. Second, we investigate the control aspects of the integrated circuit and determine how much amplitude and phase tunability can be generated to perform active cancellation. Using dispersive techniques, the integrated circuit achieves 10 dB and 52° of independent amplitude and phase tunability, respectively, at 1.25 GHz. The range decreases with increasing frequency. We find that the sensitivity of the circuit’s cancellation performance to the control biases are 2 and 0.5 mA at cancellation depths of −40 and −50 dB, respectively. Finally, we use the integrated circuit to demonstrate adaptive interference cancellation. Our results show that an integrated solution is able to achieve a cancellation performance comparable to a discrete fiber-optic system. Additionally, it is one of the first demonstrations of an integrated microwave photonic circuit that only possesses RF inputs and outputs. [ABSTRACT FROM PUBLISHER]

An optically switched high temperature superconducting (HTS) band-reject filter bank is presented. Fast low loss switching of high quality (Q) factor HTS filter elements enables digital selection of arbitrary pass-bands and stop-bands. Patterned pieces of GaAs and silicon are used in the manufacture of the photosensitive switches. Fiber optic cabling is used to transfer the optical energy from an LED to the switch. The fiber optic cable minimizes the thermal loading of the filter package and DC-couples the switch's power source from the RF circuit. This paper will discuss the development of a computer-controlled HTS bank of optically switchable, narrow band, high Q bandstop filters which incorporates a cryocooler to maintain the 77 K operating temperature of the HTS microwave circuit. [ABSTRACT FROM AUTHOR]

As driver assistance systems and autonomous driving are on the rise, radar sensors become a common device for automobiles. The high sensor density leads to the occurrence of interference, which decreases the detection capabilities. Here, digital beamforming (DBF) is applied to mitigate such interference. A DBF system requires a calibration of the different receiving channels. It is shown how this calibration completely changes the DBF beam pattern required to cancel interferences, if the system has no IQ receiver. Afterward, the application of DBF on a multiple-input multiple-output (MIMO) radar is investigated. It is shown that only the real aperture and not the virtual one can be used for interference suppression, leading to wide notches in the pattern. However, for any target the large virtual aperture can be exploited, even if interferers are blinded out. Moreover, the wide notches for interference suppression of the real aperture appear narrow in the virtual aperture for target localization. The results are verified by measurements with time-multiplexing MIMO radar. [ABSTRACT FROM AUTHOR]

A 30-MHz–3-GHz wideband complementary metal–oxide–semiconductor phased array receiver with interference suppression capability in the frequency and spatial domains is presented. A frequency filtering function is provided by a two-stage harmonic rejection mixer with 16-phase local oscillator (LO) signals that are generated by frequency dividers and phase interpolators. The developed IC suppresses third- to seventh-order harmonic interference by more than 55 dB in a wide range from 30 MHz to 3 GHz. The 16-phase LO signal generator combined with a 2-b baseband phase shifter (PS) also works as a 6-b PS. Equipped with a 6-b amplitude control in addition to the 6-b phase control, the array receiver enables analog null steering that can reduce a spatial interference coming from a specific direction. The multi-chip synchronization needed for the null steering function is realized with pre-set circuits in the frequency dividers. Space propagation measurements made on a four-element array antenna system using the developed ICs indicated that the null steering function reduces spatial interference by 20 dB and reduces the error vector magnitude of a 2-GHz radio frequency, 20-MHz bandwidth, and 64-quadrature amplitude modulation signal from −12.7 to −26.3 dB even when a strong interferer exists. [ABSTRACT FROM AUTHOR]

In this effort, the authors implement the first ultralong-range chipless sensing sticker, by providing more than an order of magnitude increase in reading range, compared with the state of the art. The theoretical advantages of the use of millimeter-wave frequencies for high-performance chipless radio-frequency identification (RFID) sensor implementations are first argued before both a new fully inkjet-printed flexible device, based on the Van-Atta reflectarray structure, as well as a new chipless RFID polarimetric interrogation, and time-frequency data-processing approach is then presented and implemented, for operation in the Ka-band. The array, fully inkjet printed on Kapton HN polyimide, was demonstrated as being robust to variations of interrogation angle (between ±70° from normal), as well as to bending. With its demonstrated range, in excess of 30 m, and its proven adequacy for dense multitag and multisensing implementations in indoor environments, the structure may set the foundation for the emergence of flexible printable low-cost sensing smart skins for the Internet of Things. [ABSTRACT FROM PUBLISHER]

A new method for measuring free-space electromagnetic waves, based on a scalar interferometric measurement principle similar to the six-port concept, is presented. A proof of concept was performed at frequency band 6-12 GHz. The corresponding measurement system contains both a reference channel featuring a transmitting antenna directly irradiating receiving antenna, and, a test channel which has a transmitting antenna irradiating a test object. A wave reflected or scattered by the test object, and the reference wave phase shifted in several steps, both coherent, interfere in the receiving antenna. Redundancy is exploited via a multistate regime of measurement which enables to reduce uncertainty of measurement. A geometrical representation of the approach in the complex plane makes it possible to estimate measurement uncertainties. Precise computing of uncertainties based on the Monte Carlo Method is also performed. [ABSTRACT FROM AUTHOR]

A mixer-first acoustic-filtering high-intermediate-frequency (IF) superheterodyne radio frequency (RF) front end is presented, which utilizes a mixed-domain recombination architecture. By having a set of commutated switches or essentially a passive mixer before fixed-frequency acoustic filters, mixer-first acoustic filtering enables a widely tunable RF for the front end while preserving the acoustic filter’s high-order filtering response and high linearity. Compared to the prior work that uses IF-only recombination, the proposed IF-and-baseband mixed-domain recombination supports a wider instantaneous bandwidth (BW) and higher RF while reducing the number of IF passive components that are lossy and bulky. A proof-of-concept chipset is demonstrated; it consists of an RF front-end $N$ -path commutated- $LC$ passive mixer and an IF in-phase and quadrature ($I$ – $Q$)-mismatch-compensating complex receiver in 65-nm CMOS as well as two 2.6-GHz Qorvo QPQ1285 bulk-acoustic wave (BAW) filters. In measurement, the chipset operates across 3.5–6.5 GHz RF with a 160-MHz instantaneous BW, 10-dB noise figure (NF) at 3.5-GHz RF, and an out-of-band IIP3 of +27 dBm at $1 \times $ BW offset. [ABSTRACT FROM AUTHOR]

A fully integrated low-power high-coexistence 2.4-GHz ZigBee transceiver implemented in 90-nm CMOS technology is demonstrated. The two-point direct-modulation with a fractional-N synthesizer is adopted in the transmitter architecture. The transmitter can provide high output power of +9 dBm and excellent error vector magnitude of 5.1%. The direct conversion is used in receiver for simplicity and -97-dBm minimum receiver sensitivity is achieved. Current consumptions for a TX at +9-dBm output power and for an RX are 28.4 and 15.4 mA, respectively. Excellent coexistence is presented through wireless local area network interferer rejection performance. [ABSTRACT FROM AUTHOR]

A low-power regenerative frequency-modulated ultra-wideband (FM-UWB) receiver with wideband signal reception and linear FM–AM conversion is implemented in 65-nm CMOS for short-range communication systems. Different from the conventional regenerative FM-UWB receiver having the narrowband low-noise amplifier (LNA), the proposed receiver employs a wideband LNA and dual bandpass filters (BPFs) to improve the robustness against narrowband interference and frequency shift-keying demodulation with a relaxed Q requirement of the BPF. A 3.5–4-GHz FM-UWB receiver consisting of a stacked LNA, dual BPFs, two envelop detectors, and a subtractor successfully performs FM demodulation through wireless transmission from a 100-kb/s FM-UWB transmitter, consuming the total power of 3.8 mW. [ABSTRACT FROM PUBLISHER]

This article presents a highly integrated, supply, temperature, and interference-robust, event-driven wake-up receiver (WuRx) achieving $< -78.3$ -dBm sensitivity using a custom-designed antenna at 4.9 GHz or $< -72.3$ -dBm sensitivity when matched to a 50- $\Omega $ source at 5.3 GHz, consuming 184 nW at room temperature. The chip is fabricated in 65-nm CMOS LP technology and powered by a single supply. A novel slot antenna is proposed to directly conjugate match to the input of the chip and eliminate lossy impedance matching networks. The integrated references and regulation enable the receiver to operate for a wide range of temperatures from $-30\,\,^\circ \text{C}$ to 70 $^\circ \text{C}$ and a supply range from 1.2 to 1.5 V. The integrated proportional–integral–derivative (PID) control module allows the WuRx to automatically adapt for different temperatures and interference signals present in the ambient environment. [ABSTRACT FROM AUTHOR]

A transformer-based notch filter is proposed in this article. The notch filter is integrated into a three-coil transformer in the matching network. While the primary coil and the secondary coil build a magnetically coupled resonator (MCR) and transfer the in-band signal to the next stage, the tertiary coil is coupled with the primary coil to absorb the interferers. Resonating with the switched capacitors, the notch frequency can be tuned digitally. A cross-coupled pair can further enhance the quality factor of the tank and, therefore, the rejection level. A low-noise amplifier (LNA) for Ku-band satellite communication with the proposed notch filter is implemented in 65-nm CMOS to verify the theory. The LNA achieves a measured power gain of 19.5 dB at 12.2 GHz with a −3-dB bandwidth of 9.2–12.7 GHz. The LNA can achieve 13.5-dB gain suppression at 13.9 GHz. The suppression level can be enhanced by tuning the quality factor of the active notch filter, which consumes up to 0.6 mW. The noise figure (NF) is 2.3 dB at 10.6 GHz and the NF is below 2.7 dB from 9.2 to 12.7 GHz. The input return loss is better than −15 dB from 8.8 to 18.5 GHz. The LNA consumes 5.9 mW from a 1-V supply. The whole chip occupies an area of 1000 $\times 800\,\,\mu \text{m}^{2}$. [ABSTRACT FROM AUTHOR]

A novel matrix-pencil (MP)-based interference mitigation approach for frequency-modulated continuous-wave (FMCW) radars is proposed in this article. The interference-contaminated segment of the beat signal is first cut out, and then, the signal samples in the cutout region are reconstructed by modeling the beat signal as a sum of complex exponentials and using the MP method to estimate their parameters. The efficiency of the proposed approach for the interference with different parameters (i.e., interference duration, signal-to-noise ratio (SNR), and different target scenarios) is investigated by means of numerical simulations. The proposed interference mitigation approach is intensively verified on experimental data. Comparisons of the proposed approach with the zeroing and other beat-frequency interpolation techniques are presented. The results indicate the broad applicability and superiority of the proposed approach, especially in low SNR and long interference duration situations. [ABSTRACT FROM AUTHOR]

In existing physical layer security (PLS) and key generation protocols, major assumptions, including channel reciprocity, localization, and synchronization between the legitimate parties, are often considered. However, these assumptions are arguable in practice leading to major barriers in building systems based on PLS protocols. To overcome these barriers, we proposed, designed, and implemented a novel embedded architecture for distributed Internet-of-Things (IoT) networks that utilize a master–slave full-duplex communication to exchange a random secret key. In the proposed architecture, an IoT node generates a phase-modulated random key/data and transmits it to a master node in the presence of an eavesdropper, referred to as Eve. The master node, simultaneously, broadcasts a high-power signal using an omnidirectional antenna, which is received as a jammer signal or interference by Eve. This results in a high bit error rate (BER) making the data undetectable by Eve. The two legitimate nodes communicate in a full-duplex fashion and, consequently, subtract their transmitted signals from the received signal (self-interference cancellation). Our proposed protocol does not require any knowledge of the node locations. In particular, we show, using theoretical and measurement results, that our proposed approach provides significantly better security measures, in terms of the BER at Eve’s location, compared to a conventional method based on directional beamforming antennas. Also, it is proved that in our novel system, the possible eavesdropping region, BER < 10−1, is always smaller than the reliable communication region, BER < 10−3. [ABSTRACT FROM AUTHOR]

A low-power CMOS sliding-IF RF receiver is presented for Bluetooth Low Energy (BLE) applications. It comprises an LNA, RF mixer, transconductance ($g_{m}$) stage, IF mixer, transimpedance amplifier (TIA), and LO generation block. We present a comprehensive analysis of the second-order intermodulation (IM2) distortion that is induced by an in-band orthogonal frequency-division modulation (OFDM) blocker and its effects on the receiver input sensitivity. Based on the analysis, an in-band two-tone blocker tolerance test procedure is proposed, and an IM2 calibration circuit to enhance the receiver’s IM2 tolerance is presented. Furthermore, a conflict issue in the co-optimization of IM2 calibration at the IF mixer stage and dc offset calibration at the subsequent baseband amplifier stage is alleviated. This is achieved by employing a body bias control method for the dc offset calibration and a gate bias control method for the IM2 calibration. A BLE RF receiver integrated circuit was fabricated in a 65-nm RF CMOS process. Dissipating 3.55 mW from a 1-V supply, it achieves a gain control range from +2 to +62 dB, a minimum noise figure of 3 dB, and an out-of-band (OOB) single-tone blocker tolerance level of −10 dBm. Measurement results demonstrate that the proposed IM2 calibration circuit significantly improves the in-band two-tone blocker tolerance level by 7–12 dB, achieving its range from −41 to −31 dBm. [ABSTRACT FROM AUTHOR]

Frequency-domain chipless RFID readers hold tremendous promise as a low-cost solution for mass production of this technology. However, the strong self-jamming signal leakage, from the transmitter to the receiver, significantly degrades the sensitivity of the reader. As a result, the maximum reading range of the system is diminished. To address this issue, we studied the sources of interference signals in the system and proposed a method to significantly reduce them. An ultrawideband compensator, over the wide frequency range of 4.3 to 7.3 GHz, was designed and implemented. This method realized an interference isolation better than 40, 55, and 55 dB in single-antenna, dual-polarized antenna, and two-antenna readers, respectively. A noticeable 25-dB excessive isolation to that of the conventional architecture which should help to bring this technology closer to commercial adoption. [ABSTRACT FROM AUTHOR]

The issue of ambiguous frequency is a major drawback of the Doppler through-wall radar in target tracking applications. To solve the issue, an additional receiver, which can acquire target information from a different detection perspective, is added to the radar system, and the data fusion process is proposed to identify and track the targets in real time. The linear prediction coding technique is combined with the data fusion process to predict the target initial state for higher positioning accuracy. Compared with the traditional tracking approach, the proposed algorithm can not only improve the target positioning accuracy, suppress the issue of ambiguous frequency, but also help to identify stationary and tangentially moving targets, which is very essential in target tracking applications. A series of experiments are conducted to illustrate an outranking performance of the proposed algorithm in comparison with the traditional approach. [ABSTRACT FROM AUTHOR]

A frequency-modulated continuous-wave (FMCW) radar interference mitigation technique using the interpolation of beat frequencies in the short-time Fourier transform (STFT) domain, phase matching, and reconfigurable linear prediction coefficients estimation for Coherent Processing Interval processing is proposed. The technique is noniterative and does not rely on algorithm convergence. It allows the usage of the fast Fourier transform (FFT) as the radar’s beat-frequency estimation tool, for reasons such as real-time implementation, noise linearity after the FFT, and compatibility with legacy receiver architectures. Verification is done in range and in range-Doppler using radar experimental data in two ways: first by removing interferences from interference-contaminated data and second by using interference-free data as the reference data, and processing it—as if it had interferences—using the proposed technique, inverse cosine windowing and zeroing for comparison. We found that processing with the proposed technique closely matches the reference-data and outperforms the inverse cosine windowing and zeroing techniques in 2-D cross correlation, amplitude, and phase average errors and phase root-mean-square error. It is expected that the proposed technique will be operationally deployed on the TU Delft simultaneous-polarimetric PARSAX radar. [ABSTRACT FROM AUTHOR]

A compact low-pass filter based on the principle of destructive interference is proposed and analyzed, followed by an improved design demonstrating very high rejection levels better than 40 dB over a wide frequency span. Both filters, fabricated using liquid crystal polymer (LCP) multilayer techniques, are self-packaged, with small footprint and profile, and also very lightweight. Simulation and measured results are presented, showing good agreement. [ABSTRACT FROM PUBLISHER]

Millimeter-precision meter-distance real-time indoor ranging capability is challenging due to multipath reflections in a rich scattering environment. Traditional continuous wave (CW) phase-based ranging methods, although simple and flexible, are vulnerable to phase offsets and interferences. We improve the previous CW approach by passive broadband harmonic nonlinear-transmission-line (NLTL) tags. Since phase information is now contained within the second harmonic rather than the fundamental frequency, interferences and phase errors caused by direct reflections of the interrogating signal are greatly reduced. By the broadband property of NLTL, a heuristic multi-frequency CW method is formulated to resolve the phase integer ambiguity and to further improve ranging accuracy and robustness even under large phase errors. We present theoretical and simulation analyses, followed by experimental verification. [ABSTRACT FROM PUBLISHER]

Navigation in global positioning system (GPS)-denied or GPS-inhibited environments such as urban canyons, mountain areas, and indoors is often accomplished with an inertial measurement unit (IMU). For portable navigation, miniaturized IMUs suffer from poor accuracy due to bias, bias drift, and noise. We propose to use a low-power shoe-embedded radar as an aiding sensor to identify zero velocity periods during which the individual IMU sensor biases can be observed. The proposed radar sensor can also be used to detect the vertical position and velocity of the IMU relative to the ground in real time, which provides additional independent information for sensor fusion. The impacts of the noise and interference on the system performance have been analyzed analytically. A prototype sensor has been constructed to demonstrate the concept, and experimental results show that the proposed sensor is promising for position and velocity sensing. [ABSTRACT FROM PUBLISHER]