Baseband Frequency Research Articles

A Full-Duplex Single-Chip Transceiver With Self-Interference Cancellation in 0.13 <inline-formula> <tex-math notation="LaTeX">$\mu$ </tex-math> </inline-formula>m SiGe BiCMOS for Electron Paramagnetic Resonance Spectroscopy

This paper presents a miniaturized EPR spectrometer based on a single-chip transceiver. Utilizing a novel on-chip self-interference cancellation circuit, the electromagnetic coupling from the transmitter (TX) to the receiver (RX) is minimized, allowing simultaneous achievement of large TX output power and low RX noise figure (NF). In the measurement, the RX achieves a NF of 3.1 dB/6.3 dB at 10 MHz/50 kHz baseband frequencies, when the TX and cancellation circuits are turned off. The measured flicker noise corner is 60 kHz, more than $10\times $ lower than the prior work. Moreover, for the first time, the operation of the RX and cancellation circuit is demonstrated when a co-integrated TX is operating at the same time and frequency, while producing >20 dBm output power. When the TX and cancellation circuits are turned on, at −10 dBm interference power, the measured NF is 6.8 dB/11.1 dB at 10 MHz/50 kHz baseband frequencies. This is lower by 5.6 dB/9.6 dB at 10 MHz/50 kHz baseband frequencies, compared to the NF with the cancellation circuit off at the same interference power. The transceiver chip is implemented in IBM $0.13~\mu \text {m}$ BiCMOS process and consumes a power of 2 W. Utilizing this transceiver, an electron paramagnetic resonance (EPR) spectrometer is built and tested. It is observed, through measurement, that the interference cancellation circuit increases the signal-to-noise ratio (SNR) of the EPR signal by 7 dB at −10 dBm interference power. Compared to prior work, the reported EPR spectrometer improves the sensitivity of the system by 25 dB.

Numerical Analysis of a Multi-Function Photonic Integrated Circuit for Coherent Radio-Over-Fiber

A digital coherent radio-over-fiber (RoF) system comprising a microwave photonic integrated circuit (MPIC) as the main building block is proposed. The multifunction MPIC circuit is analyzed to operate as a single-sideband (SSB) modulator and as an in-phase and quadrature modulator (IQM) of a baseband signal in the RoF downlink. The circuit is also analyzed in the uplink as an SSB of a 60-GHz frequency-shifted input. The performance of the MPIC is assessed through numerical simulations, computing the harmonic distortions in the SSB, as well as the error vector magnitude in the IQM and coherent RoF system. Obtained results illustrate the advantage of the proposed MPIC for heterodyne mixing by providing the upper and lower sidebands spatially located in distinct ports. Moreover, simulation results yield insights into the feasibility of the circuit as an IQM of both baseband and low-power intermediate frequency signals. A comparison of an orthogonal frequency division multiplexing system and a single carrier system employing the proposed circuit in the end-to-end transport of high data rate is presented through error vector magnitude calculations.

Theory and circuit modeling of baseband and modulated signal delay compensations with low- and band-pass NGD effects

With the increase of the electrical interconnect network complexity, the signal integrity (SI) analysis becomes crucial for the electronic RF and mixed circuit designer. Approximated and optimized models of printed circuit boards (PCBs) electrical interconnect network were developed. However, interconnect effect correction techniques are still needed. The present paper addresses an example of correction technique of electrical interconnect for the PCBs. The feasibility of the concept is verified by considering a distributed transmission line (TL) latency and delay correction. The proposed correction technique is based on the use of the negative group delay (NGD) circuits. The theoretical approach including the NGD cell synthesis relations are established. The innovative low- and band-pass NGD topologies are suggested respectively for the baseband and modulated signal delay reduction. The fundamental characteristics of the low- and band-pass NGD cells are examined. The proposed technique is applied to the compensation of the microstrip interconnect line delay. It was found that the NGD effects enable to compensate the signal delay in baseband frequency up to hundreds MHz with low-pass NGD circuit and 2.45GHz modulated microwave signals with band-pass NGD circuit. In both cases, the possibilities to reduce the latency and delay of some nanoseconds (ns) are performed.

Background-Free Microwave Signal Generation Based on Unbalanced Temporal Pulse Shaping

We propose a new method to generate background-free high-frequency pulsed microwave signal based on an unbalanced temporal optical pulse shaping (TPS) system and balanced photodetection. The proposed system consists of a polarization modulator and an unbalanced TPS system realized by two conjugate dispersion elements. The carrier frequency of the pulsed microwave signal could be tuned by changing the residual dispersion of the TPS. The proposed method is theoretically analyzed and experimentally demonstrated. The experimental results show that the carrier frequency of the generated microwave pulse could be tuned over a broad frequency range. Moreover, the generated microwave pulse signal is background-free by suppressing the baseband frequency components using balanced photodetection.

An Analysis Approach for the Assessment of Pulse-width Modulated Carrier Frequency Spectral Components in Power Distribution Systems with Photovoltaic Resources

Power distribution systems may have photovoltaic resources, and these resources may interface with the AC system via pulse-width modulated inverters. The pulse-width modulated currents have high-frequency spectra due to the switching frequency, which is typically 2.0–20 kHz. These carrier frequency components are asynchronous to the “power frequency” (the “baseband,” which is 50 or 60 Hz). Residential photovoltaic resources are in the 2–5 kW range, and “utility-scale” photovoltaic resources may be in the range of 500 kW. The pulse-width modulated carrier frequency components of voltage and current propagate in the power distribution system, and the details of this propagation are described. Note that the pulse-width modulated voltages are not harmonics of the 60-Hz baseband frequency, nor are the several pulse-width modulated voltages generally synchronous with each other. The objective is to describe an analytical approach for the assessment of carrier frequency spectra in distribution systems with photovoltaic resources. Analysis tools and experience with those tools are given. Information is given to distribution engineers faced with systems with pulse-width modulated inverter resources and advice on frequency ranges of study, potential modeling inaccuracies, and software tools. The results of a study on an actual high penetration solar photovoltaic feeder are given.

Millimeter-Wave Photonics for Communications and Phased Arrays

This article presents recent developments in millimeter-wave communications architectures featuring broadband photonic signal generation, up-conversion and down-conversion, as well as true-time-delay photonic steering of millimeter-wave arrays. These developments will support future high-capacity millimeter-wave wireless communications by enabling broadband signals to be generated and converted between baseband and millimeter-wave carrier frequencies without electronic heterodyne systems and by permitting the use of true-time-delay beamsteering in millimeter-wave array apertures.

Wireless data transfer with mm-waves for future tracking detectors

Wireless data transfer has revolutionized the consumer market for the last decade generating many products equipped with transmitters and receivers for wireless data transfer. Wireless technology opens attractive possibilities for data transfer in future tracking detectors. The reduction of wires and connectors for data links is certainly beneficial both for the material budget and the reliability of the system. An advantage of wireless data transfer is the freedom of routing signals which today is particularly complicated when bringing the data the first 50 cm out of the tracker. With wireless links intelligence can be built into a tracker by introducing communication between tracking layers within a region of interest which would allow the construction of track primitives in real time. The wireless technology used in consumer products is however not suitable for tracker readouts. The low data transfer capacity of current 5 GHz transceivers and the relatively large feature sizes of the components is a disadvantage.Due to the requirement of high data rates in tracking detectors high bandwidth is required. The frequency band around 60 GHz turns out to be a very promising candidate for data transfer in a detector system. The high baseband frequency allows for data transfer in the order of several Gbit/s. Due to the small wavelength in the mm range only small structures are needed for the transmitting and receiving electronics. The 60 GHz frequency band is a strong candidate for future WLAN applications hence components are already starting to be available on the market.Patch antennas produced on flexible Printed Circuit Board substrate that can be used for wireless communication in future trackers are presented in this article. The antennas can be connected to transceivers for data transmission/reception or be connected by wave-guides to structures capable of bringing the 60 GHz signal behind boundaries. Results on simulation and fabrication of these antennas are presented as well as studies on the sensitivity of production tolerances.

Experimental investigations in transmission performance of real-time long-reach adaptively modulated direct-detection optical-orthogonal frequency division multiplexing systems

A real-time base-band orthogonal frequency division multiplexing (OFDM) transceiver with symbol synchronization, channel equalization, sampling clock frequency synchronization, and adaptive modulation technique is successfully implemented by field programmable gate arrays and a 2.5-GSps digital-to-analog converter and analog-to-digital converter. The real-time optical OFDM signal at a raw bit rate of 5.156 Gbps within about 1.1-GHz bandwidth transmission over 100-km standard single-mode fiber (SSMF) is experimentally investigated in a simple intensity-modulation and direct-detection system. The experimental results show that the real-time system has a good bit error rate (BER) performance by using an adaptive modulation technique according to the conditions on the subchannels. After 100-km SSMF transmission, at a BER of 1×10−3, the power penalty is <1 dB. Moreover, there is a negligible penalty between the off-line and real-time digital signal processing results.

Noise and Sensitivity of Harmonic Radar Architecture for Remote Sensing and Detection of Vital Signs

This paper addresses noise and sensitivity issues in remote sensing and detection of vital signs based on a continuous wave biomedical radar operating at multiple harmonic carrier frequencies or channels. This Doppler radar makes use of a single mixer, taking advantage of the inherent nonlinearity and harmonic characteristics of the mixer. Other system building elements such as antennas, amplifiers, and circulators can also operate at and comply with multiple harmonic frequencies or channels requirements, which makes the system compact. Noise is one of the most important factors that affect the sensitivity of this type of system. The total noise is the combined contribution of thermal noise, residual phase noise, and flicker noise. Flicker noise is found to be the critical parameter for the baseband detection. Experimental results show that with the use of the harmonic radar technique, the flicker noise can be reduced by 20 dB around 1-Hz baseband frequency compared with the counterpart in a conventional radar operating at single frequency. The noise and sensitivity of a harmonic radar system operating at 12 and 24 GHz for vital signs detection are studied theoretically and experimentally. It is proven that the harmonic radar solution is able to increase detection sensitivity by increasing the signal-to-noise ratio. The performance of the harmonic radar is tested experimentally with a moving plate and also a real patient. For the heartbeat detection, an oximeter giving the oxygen saturation of blood and heart rate is used as the reference.

A High Speed Radio on Fiber Based on Optical Double-Sidebands via Optical Filter and Optical Phase Modulation

We demonstrate a system scheme of generating and transmitting base-band and radio frequency signal based on optical double-sidebands scheme to generate optical millimeter-wave signal via optical phase modulation (OPM) and FBG. The system architecture with the source of laser at central station, the data re-modulation on downlink optical carrier gained from one base station is a good method to reduce the cost of uplink transmitter, for it does not needs the source of laser and wavelength administration at the base station. The optical phase modulator is inexpensive and mature. The downlink communicated bandwidth can be doubled to realize Ultra Width Band &amp; Ultra High Frequency (UHF) communication via phase modulation and FBG at the base station. And the other signal which is reflected by FBG can be reused as uplink via amplitude modulation availably. The simulation results show that the bi-directional 2.5Gbit/s data and UHF microwave with 24GHz is successfully transmitted over 50km distance of a single-mode optical fiber with a optical dispersion of 20ps/(nm·km), an optical attenuation of 0.25dB/km and a light source power of 3dBm.

Generation of FCC-compliant and background-free millimeter-wave ultrawideband signal based on nonlinear polarization rotation in a highly nonlinear fiber.

We propose a novel approach to generating millimeter-wave (MMW) ultrawideband (UWB) signal based on nonlinear polarization rotation (NPR) in a highly nonlinear fiber (HNLF). The MMW UWB signal is background-free by eliminating the baseband frequency components using an optical filter. The proposed scheme is theoretically analyzed and experimentally verified. The generated MMW UWB signal centered at 25.5 GHz has a 10-dB bandwidth of 7 GHz from 22 to 29 GHz, which fully satisfies the spectral mask regulated by the Federal Communications Commission (FCC).

Photonic generation of arbitrarily phase-modulated microwave signals based on a single DDMZM

We propose and demonstrate a compact and cost-effective photonic approach to generate arbitrarily phase-modulated microwave signals using a conventional dual-drive Mach-Zehnder modulator (DDMZM). One arm (arm1) of the DDMZM is driven by a sinusoidal microwave signal whose power is optimized to suppress the optical carrier, while the other arm (arm2) of the DDMZM is driven by a coding signal. In this way, the phase-modulated optical carrier from the arm2 and the sidebands from the arm1 are combined together at the output of the DDMZM. Binary phase-coded microwave pulses which are free from the baseband frequency components can be generated when the coding signal is a three-level signal. In this case, the precise π phase shift of the microwave signal is independent of the amplitude of the coding signal. Moreover, arbitrarily phase-modulated microwave signals can be generated when an optical bandpass filter is attached after the DDMZM to achieve optical single-sideband modulation. The proposed approach is theoretically analyzed and experimentally verified. The binary phase-coded microwave pulses, quaternary phase-coded microwave signal, and linearly frequency-chirped microwave signal are experimentally generated. The simulated and the experimental results agree very well with each other.

Photonic generation of background-free millimeter-wave ultra-wideband pulses based on a single dual-drive Mach–Zehnder modulator

We propose a novel photonic approach for generating a background-free millimeter-wave (MMW) ultra-wideband (UWB) signal based on a conventional dual-drive Mach-Zehnder modulator (DMZM). One arm of the DMZM is driven by a local oscillator (LO) signal. The LO power is optimized to realize optical carrier suppressed modulation. The other arm is fed by a rectangular signal. The MMW UWB pulses are generated by truncating the continuous wave LO signal into a pulsed one in a photodetector (PD). The generated MMW UWB signal is background-free by eliminating the baseband frequency components because the optical power launched to the PD keeps constant all the time. The proposed method is theoretically analyzed and experimentally verified. The generated MMW UWB signal centered at a frequency of 26 GHz meets the Federal Communications Commission spectral mask very well.

Orthogonal time-frequency domain multiplexing with multilevel signaling

In this paper, we propose and investigate an optical multiplexing technique, called orthogonal time-frequency domain multiplexing (OTFDM) with multilevel signaling, that enables ultrafast, high-spectral-efficiency transmission. On the transmitter side, optical rectangular combs generated from electro-optic modulators are data modulated and multiplexed into the time-frequency domain. On the receiver side, the OTFDM signal is demultiplexed and coherently demodulated by coherent matched detection in which multi-frequency homodyne mixing with a locally generated comb down-converts a target OTFDM tributary channel into baseband frequencies. These multiplexing and demultiplexing processes are fully performed in the optical domain using optoelectronic devices, without the use of fast Fourier transform circuits or optical channel selection filters. It is analytically and numerically proved that multilevel signals such as nPSK and nQAM can be OTFDM-multiplexed and demultiplexed while retaining orthogonality between tributaries. The spectral efficiency of this method reaches as high as 1 Baud/Hz per single polarization, i.e., the Nyquist limit, enabling high-bandwidth operation unrestricted by an electronic response in the transmitter or receiver.

Real-Time Optical OFDM Long-Reach PON System Over 100 km SSMF Using a Directly Modulated DFB Laser

A real-time base-band orthogonal frequency division multiplexing (OFDM) transceiver with a simple symbol synchronization and channel estimation scheme is implemented on only one off-the-shelf commercial field programmable gate array (FPGA). The real-time optical OFDM long-reach passive optical network (PON) system with direct detection over 100 km standard single-mode fiber (SSMF) employing a cost-effective directly modulated distributed feedback (DFB) laser has been successfully demonstrated experimentally. The experimental results show that the simplified symbol synchronization with low complexity and high accuracy is effective for long-reach optical OFDM transmission systems. After 100 km SSMF transmission, the power penalty at a bit-error rate of 1e-3 is only about 1.1 dB.

Photonic Generation of Ultrawideband Signals With Large Carrier Frequency Tunability Based on an Optical Carrier Phase-Shifting Method

We theoretically and experimentally demonstrated a novel photonic approach to generating ultrawideband (UWB) pulses with large carrier frequency tunability based on an optical carrier phase-shifting technique by cascading polarization modulators (PolMs) and a polarizer. The UWB pulses are generated by truncating a continuous wave (CW) RF signal into a pulsed signal in a photodetector (PD). The experimental results show that the baseband frequency components and the strong residual local oscillator (LO) signal are well suppressed. In addition, the generated UWB signals satisfy the Federal Communications Commission (FCC) spectral mask very well.

Photonic generation of widely tunable and background-free binary phase-coded radio-frequency pulses

We present a novel photonic approach to generating widely tunable and background-free binary phase-coded radio-frequency (RF) pulses by cascading a polarization modulator (PolM) and a phase modulator (PM). The PolM is used to produce an optical carrier and two sidebands with orthogonal polarization states. The phase shift θ between the optical carrier and the sidebands is controlled by the electrical driving signal applied to the PM. For θ>π/2 or <π/2, the phase of the detected RF signal is 0 or π, respectively. For θ=π/2, there is no RF signal recovered in the photodiode (PD). In this way, binary phase-coded RF pulses can be generated, while the optical power launched to the PD keeps constant. The proposed technique is therefore background free by eliminating the baseband frequency components. Moreover, the carrier frequency of the RF pulses is widely tunable and the π phase shift of the RF signal is independent of the amplitude of the electrical driving signal. The proposed scheme is theoretically analyzed and experimentally verified.

MULTI-TONE MEASUREMENT SYSTEM WITH THE STATE-OF-THE-ART ACTIVE IF AND RF LOAD-PULL CAPABILITY

This paper reports a refined multi-tone waveform measurement system for the robust characterization and optimization of nonlinear microwave devices when driven by broadband multi-tone stimuli. This enhanced system has the ability to present specific, constant broadband impedances, not only at baseband (IF) frequencies, but also at RF frequencies, particularly, around the carrier and significant harmonics. This functionality is key in studying the effects of out-of-band impedance termination on both short and long-term electrical memory effects. Achieving such comprehensive impedance control across wide modulation bandwidths is also critical in allowing the "emulation" of emerging power amplifier modes and architectures, and the subsequent waveform characterization of devices operating in these complex and often dynamic impedance environments. Initially, the baseband load-pull capabilities of the enhanced measurement system are experimentally demonstrated through the measurement of adjacent channel power (ACP) behavior of a class AB biased 10 W GaN HEMT, in response to a varying baseband load. Complete baseband and RF impedance control is then demonstrated through the emulation and analysis of a modulated Class-J impedance environment, which interestingly highlights the presence of separate optimum baseband impedance conditions necessary for the suppression of individual IM products.

Multi-tone parallel coherent matched detection for demultiplexing of superchannels

This paper presents multi-tone parallel coherent matched detection that orthogonally detects superchannels without crosstalk between neighboring channels. The receiver consists of multiple sets of multi-tone coherent matched detector employed in parallel. In each detector, the received superchannels signal is homodyne mixed in multi frequency with locally generated multi-tone optical frequency comb; detected is a signal set that has the amplitude and phase exactly matched with the local comb. By launching orthogonal sets of local comb to the multiple parallel coherent matched detectors, the received superchannels are orthogonally downconverted to the baseband frequencies keeping the amplitude and phase information of all channels included. With an aid of n × n transform matrix, all channels are separately recovered from the downconverted signal sets. The system does not rely on any optical filters for channel demultiplexing and separation, with increased flexibility in wavelength arrangement. In addition, the parallel configuration equivalently enhance the bandwidth of the coherent matched detector keeping the speed in each tributary channel as high as possible. In this paper, it is experimentally demonstrated that even-odd interleaved 23 × 20-Gb/s QPSK superchannels are orthogonally demultiplexed and detected by two-tone coherent matched detection.

BD 빔포밍을 이용한 다중 사용자 기반 거대 안테나 통신 시스템용 안테나 선택 기법

Intensive researches on multiuser-based Massive MIMO are performed to increase the spectral efficiency. Although the Massive MIMO scheme based on huge number of antennas inevitably causes hardware and computational complexity in baseband and radio frequency (RF) elements, the problem can be mitigated without serious performance degradation by limiting the number of baseband and RF elements below the number of transmit antennas of base station and opportunistically selecting transmit antennas according to channel states. Accordingly, this paper proposes a simple antenna selection scheme for multiuser-based Massive MIMO systems.