Baseband Components Research Articles

Photonic Generation and Antidispersion Transmission of Background-Free Multiband Arbitrarily Phase-Coded Microwave Signals

A novel type of photonic background-free multiband arbitrarily phase-coded microwave signal generator with power fading elimination capability is reported. An <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> -polarized phase modulated optical signal and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula> -polarized radio frequency (RF) modulated harmonic single-sideband (HSSB) optical signal are produced based on a dual-polarization quadrature phase shift-keying modulator (DP-QPSKM). After polarization modulation to intensity modulation conversion, a microwave signal with arbitrarily phase encoding in multiple frequency bands is generated. Benefiting from the phase modulation state of the driven electrical coded signal, the generated arbitrarily phase-coded signal has no baseband components. Moreover, the equivalent HSSB modulation ensures the system can realize antidispersion transmission of one-to-multi base stations (BSs). The main distinct highlights of our generator are multifunction. The proposed single-modulator-based photonic scheme can achieve phase encoding in arbitrary format over multiple frequency bands and transmit over long-distance single-mode fiber with the elimination of power fading simultaneously. This work is pretty promising in multiband radar systems for one-to-multi BSs transmission and can increase the detection range, range resolution, Doppler tolerance, and sensitivity of objective recognition of radars.

Photonics Generation of Baseband-Free Arbitrary-Phase-Coded Microwave Waveform Pulse

A photonics system for baseband-free arbitrary-phase-coded microwave waveform pulse (APCMWP) generation is proposed and demonstrated. The proposed system realizes the generation of APCMWP, and further solves the baseband components problem in the pulsed process. The system uses a polarization-multiplexing dual-drive Mach–Zehnder modulator (PM-DMZM) and an optical band pass filter (OBPF) to obtain a polarization-multiplexed single-sideband modulated (SSBM) optical signal with carrier intensity-phase modulation, then uses a balanced photodetector (BPD) to properly detect the polarization-multiplexed SSBM optical signal, APCMWP with baseband components suppression can be easily generated. A detailed theoretical analysis and a proof-of-concept experiment are provided. The generations of 1.2-GBaud 9.6-GHz and 2-GBaud 12-GHz baseband-free APCMWP are verified.

Optimal Bit Allocation-Based Hybrid Precoder-Combiner Design Techniques for mmWave MIMO-OFDM Systems

This work conceives techniques for the design of hybrid precoders/combiners for optimal bit allocation in frequency selective millimeter wave (mmWave) multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems, toward transmission rate maximization. Initially, the optimal fully digital ideal precoder/ combiner design is derived together with a closed-form expression for the optimal bit allocation in the above system. This is followed by the development of a framework for optimal transceiver design and bit allocation in a practical mmWave MIMO-OFDM implementation with a hybrid architecture. It is demonstrated that the pertinent problem can be formulated as a multiple measurement vector (MMV)-based sparse signal recovery problem for joint design of the RF and baseband components across all the subcarriers, and an explicit algorithm is derived to solve this using the simultaneous orthogonal matching pursuit (SOMP). To overcome the shortcomings of the SOMP-based greedy approach, an MMV sparse Bayesian learning (MSBL)-based state-of-the-art algorithm is subsequently developed, which is seen to lead to improved performance due to the superior sparse recovery properties of the Bayesian learning framework. Simulation results verify the efficacy of the proposed designs and also demonstrate that the performance of the hybrid transceiver is close to that of its fully-digital counterpart.

Rank Constrained Precoding for the Downlink of mmWave Massive MIMO Hybrid Systems

The hybrid design of precoding schemes for millimeter-wave communications allows exploiting the gains by using large antenna array with an affordable hardware cost and power consumption. In this work, we present a novel design strategy based on limiting the rank of the fully digital solutions before their decomposition into the analog and digital baseband components. This rank constraint on the digital formulation leads to a joint precoding and scheduling scheme where the number of allocated streams is limited according to the hardware constraints. In this way, the proposed approach can significantly reduce the performance losses caused by the direct decomposition of the unconstrained digital precoders. The resulting rank-constrained problems for the considered scenario are not convex and difficult to sort out. However, we propose several algorithms to compute the rank-constrained digital solutions with the help of the uplink-downlink duality for the achievable sum-rate. The obtained results show that this strategy achieves considerably higher sum-rates regardless of the channel conditions or available hardware resources.

Resource reduction for simultaneous generation of two types of continuous variable nonclassical states

We demonstrate experimentally the simultaneous generation and detection of two types of continuous variable nonclassical states from one type-0 phase-matching optical parametric amplifcation (OPA) and subsequent two ring flter cavities (RFCs). The output feld of the OPA includes the baseband ω0 and sideband modes ω0± nωf subjects to the cavity resonance condition, which are separated by two cascaded RFCs. The first RFC resonates with half the pump wavelength ω0 and the transmitted baseband component is a squeezed state. The refected felds of the frst RFC, including the sideband modes ω0± ωf, are separated by the second RFC, construct Einstein–Podolsky–Rosen entangled state. All freedoms, including the filter cavities for sideband separation and relative phases for the measurements of these sidebands, are actively stabilized. The noise variance of squeezed states is 10.2 dB below the shot noise limit (SNL), the correlation variances of both quadrature amplitude-sum and quadrature phase-diference for the entanglement state are 10.0 dB below the corresponding SNL.

300‐GHz integrated heterodyne receiver with carrier lock‐in Costas loop

A carrier signal lock-in experiment using a 300-GHz integrated heterodyne circuit is presented. The circuit contains a single voltage-controlled oscillator with a single set of quadrature mixers that are fabricated using 250-nm InP double hetero-junction bipolar transistor technology. An external feedback loop containing packaged baseband components such as amplifiers, a phase discriminator, and a filter is connected to the integrated circuit to form a complete receiver system. For a −25 dBm of input RF signal with 3.5-GHz single-tone carrier-suppressed modulation, the receiver system responds with successful lock-in range of 110 MHz centred around 311 GHz.

Fully Integrated Dual-Mode X-Band Radar Transceiver Using Configurable Receiver and Local Oscillator

In this paper, a fully-integrated dual-mode X-band radar transceiver that supports Doppler radar and frequency modulated continuous wave (FMCW) radar is proposed. To remove large off-chip DC-blocking capacitors in the Doppler mode, the double-conversion technique and local oscillator (LO) chopping technique are introduced. These techniques remove the DC offset and makes the transceiver more robust to the TX to RX leakage. In addition, they also improve the noise figure (NF) by filtering out 1/f noise of the analog baseband. The FMCW radar is realized using a direct-conversion receiver and a chirp generator. The chirp generator consists of a frequency sweep generator (FSG) and a fractional-N phase-locked loop (PLL). All the analog baseband components including a programable gain amplifiers (PGA) and 1/R 4 range compensation filters are integrated on the chip as well as a bandgap and low-dropout regulators. The operating frequency is from 9.7 to 12.3 GHz, which consumes 216 mW in Doppler mode and 201.6 mW in FMCW mode from a 1.2-V supply voltage. The maximum chirp bandwidth is 750 MHz and the maximum receiver gain is 76 dB with 6-dB gain step. The chip size of the transceiver is 7.68 mm 2 including all the pads.

All-optical generation of binary phase-coded microwave pulses without baseband components based on a dual-parallel Mach-Zehnder modulator.

In this paper, we propose an all-optical system for the generation of binary phase-coded microwave pulses without baseband components. The scheme is based on a dual-parallel Mach-Zehnder modulator (DPMZM). By properly applying the coding signals and the microwave signals to the precisely biased DPMZM, accurate π phase shift binary phase-coded microwave pulses without baseband components can be generated. The proposed system has an extremely simple and stable all-optical structure, leading to a large frequency tuning range and a high signal quality. The operation of the system is very easy. The generation of the 2-Gbit/s 14-GHz and 4-Gbit/s 16-GHz binary phase-coded microwave pulses under different coding signal amplitudes and microwave carrier powers are experimental verified. The results show that the proposed binary phase-coded microwave pulses generation system has high quality and performance.

Efficiency Degradation Analysis in Wideband Power Amplifiers

This paper addresses the mechanisms of wideband power amplifiers’ efficiency degradation in comparison with their narrowband operation. It starts by identifying some possible causes for this performance degradation, showing that the baseband terminations are dominant. A detailed explanation for the efficiency degradation is then presented, considering the scenarios where the most important baseband components fall before or after the resonance imposed by the bias and matching networks. A theoretical model that is able to describe this performance degradation is also presented. Finally, the proposed theory is validated through two implemented power amplifiers with the same fundamental and harmonic terminations, but with different baseband networks, showing that an optimized bias network design can improve the efficiency performance of a PA.

Fault line detection method based on the improved SVD de‐noising and ideal clustering curve for distribution networks

This study proposes an adaptive fault line detection method based on the improved singular value decomposition (SVD) de-noising and ideal clustering curve for distribution networks. First, the improved SVD algorithm is introduced to obtain the pure transient zero sequence current. Then, the fast Fourier transformation is employed to analyse the baseband signal and calculate the phase differences. After that, if the difference values are larger than the set threshold, the detection method based on the improved SVD and ideal clustering curve of baseband components is proposed; if not, the 1/4 cycle damping non-periodic components are rearranged, then based on the first half waveform extreme values and the rearranging damping non-periodic components, the detection method based on the ideal clustering curve of damping components is introduced. The simulation results prove the correctness of proposed selection method. After comparing with the existing methods, the advantages of proposed method are confirmed.

All-Digital High Resolution D/A Conversion by Dyadic Digital Pulse Modulation

In this paper, the limitations of digital-to-analog (D/A) conversion by Digital Pulse Width Modulation (DPWM) are addressed and the novel Dyadic Digital Pulse Modulation (DDPM) technique for all-digital, low cost, high resolution, Nyquist-rate D/A conversion is proposed. Thanks to the spectral characteristics of the new modulation, in particular, the requirements of the filter needed to extract the baseband component of DPWM signals can be significantly released so that to be suitable to inexpensive integration on silicon in analog interfaces for nanoscale integrated systems. After the new DDPM technique and its properties are introduced on a theoretical basis, the implementation of a D/A converter (DAC) based on the proposed modulation is addressed and its performance in terms of noise and linearity is discussed. A 16-bit DDPM-DAC prototype is finally synthesized on a field-programmable gate array (FPGA) and experimentally characterized.

Reference Receiver Enhanced Digital Linearization of Wideband Direct-Conversion Receivers

This paper proposes two digital receiver (RX) linearization and in-phase/quadrature (I/Q) correction solutions, where an additional reference RX (ref-RX) chain is adopted in order to obtain a more linear observation, in particular, of the strong incoming signals. This is accomplished with reduced RF gain in the ref-RX in order to avoid nonlinear distortion therein. In digital domain, the signal observed by the ref-RX is exploited in linearizing the main RX. This allows combining the sensitivity of the main RX and the linearity of the lower gain ref-RX. The proposed digital processing solutions for implementing the linearization are feedforward interference cancelation and nonlinearity inversion, which are both adapted blindly, without a priori information of the received signals or RX nonlinearity characteristics. The linearization solutions enable flexible suppression of nonlinear distortion stemming from both the RF and analog baseband components of different orders. Especially, wideband multicarrier RXs, where significant demands are set for the RX linearity and I/Q matching, are targeted. Using comprehensive RF measurements and realistic base-station scale components, an RX blocker tolerance improvement of 23 dB and a weak carrier signal-to-noise-and-distortion ratio gain of 19 dB are demonstrated with combined linearization and I/Q correction.

Photonic frequency up‐conversion of baseband pulses for IR‐UWB using optical beating and balanced coherent detection

ABSTRACTThis article describes a photonic scheme that performs frequency up‐conversion of baseband pulses for potential applications on Impulse Radio‐Ultra Wideband systems. Mixing a laser modulated by a pulse with a wavelength‐tunable laser (local oscillator) and a coherent photodetection scheme we obtain high order pulses comparable with nth derivatives of a Gaussian pulse. With our approach is possible to perform the frequency translation of the baseband pulses so that UWB pulses within standardized UWB mask are obtained. Baseband components produced in the optical mixing are removed by using a balanced photodetection stage. Our scheme exploits two different microwave photonics technics (microwave generation and coherent detection) for accomplish a simple generator of high order pulses avoiding the use of complex schemes. Additionally, the scheme can be implemented with commercially available components and it is reconfigurable in a very simple way. The performance of the proposed scheme is analyzed and evaluated in this work.© 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2749–2755, 2016

A 3–5 GHz low-power high-speed radiated power tuning UWB transmitter

To satisfy the different radiated power requirements for the ultra-wideband (UWB) data transmitting in the implantable electronic devices or the wireless component interconnections, a novel low-power high-speed UWB transmitter with radiated power tuning was proposed. The tunable radiated power is achieved by a UWB RF buffer with a peak value controller. The designed low-complex narrow pulse generator and digital ring on–off VCO ensure a high speed transmitting. The low power is realized by using a subtractor to eliminate the base-band component from the output of the VCO and making the UWB RF buffer and the VCO operating in standby mode. The design was fabricated by a standard 0.18μm CMOS technology. The test results show that the design can achieve maximum data-rate of 250Mbps, frequency bandwidth from 3 to 5GHz, radiated power tuning from −40dBm to −60dBm, low-power of 8pJ/bit, and small circuit area of 0.18mm2.

Compensation of Nonlinear Harmonic Coupling for Pulsed-Jet-Velocity Shaping

This paper describes an approach to periodic reference tracking in a pulsed-jet-injection experimental study. The objective was to match the jet’s temporal velocity profile to a periodic reference. The challenge lies in controlling the highly nonlinear and poorly understood dynamics associated with the jet velocity. Although the actuator maintains good authority over the jet velocity, the nonlinear jet dynamics creates a high degree of coupling among neighboring harmonics that depends on the forcing level and the desired waveform. The coupling is quantified by demodulating the jet-velocity measurement into baseband components centered at the harmonic frequencies represented in the desired waveform. An empirical input–output relationship is developed by perturbing the baseband components and measuring their effect on neighboring harmonics, and it is shown that this relationship can be modeled as a linear multi-input/multi-output system. This knowledge is exploited to create stabilizing feedback controls that asymptotically drive the jet velocity to the desired waveforms over a wide range of forcing conditions.

Reconfigurable fully digital transmitter with carrier‐frequency pulse‐width modulation

A reconfigurable fully digital transmitter with carrier-frequency (CF) pulse-width modulation (PWM) is implemented in 180 nm CMOS for low CF applications. Through delay lines, baseband phases are mapped to position delays of 1/4 period of a carrier clock. With delay lines based CF PWM, pre-corrected baseband envelopes are converted to pulse-widths of the position-modulated carrier clock. Both the pulse-widths and the positions of the modulated carrier clock are amplified and reshaped to the sine-wave carrier with baseband components by the sequent switched-mode power amplifier and a bandpass filter. The circuit-level simulation results verify that the proposed implementation achieves reconfigurable CF and 20 dB spectrum optimisation, when compared with the existing intermediate-frequency PWM based designs.

Tunable all-optical single-bandpass photonic microwave filter based on spectrally sliced broad optical source and phase modulation

A tunable all-optical single-bandpass photonic microwave filter (PMF) based on spectrally sliced broadband optical source and phase modulation is proposed and experimentally demonstrated. A broadband optical source and a Mach-Zehnder interferometer (MZI) are used to generate continuous optical spectral samples, which are employed to form a finite impulse response filter with a single-bandpass response with the help of a single-mode fiber. A phase modulator is then adopted to eliminate the baseband components in the filtering response. The center frequency of the PMF can be tuned by changing the free spectral range of the MZI. An experiment is performed, and the results demonstrate that the proposed PMF has a single-bandpass without baseband components and a tuning range of 5-15 GHz.

Statistical Modeling of the Interference Noise Generated by Computing Platforms

The trend of electronic systems toward higher integration and higher performance has also brought new challenges to the design of radio transceivers. The decrease of switching times accompanied by the increase of clock speeds, data rates, and interconnection speeds contribute to improve the overall system performance. At the same time, they also affect wireless communications due to an increment of the emissions of electromagnetic radiation. In this paper, we show that the statistics of the baseband components of the noise follow the K-distribution. The one-sided version of this distribution has been derived before as a model for the envelope of sea echo in radar and sonar, however, we show here that its two-sided version can also be used to model the interference noise that affects a transceiver located inside a computer platform. The model shows good agreement with experimental measurements. Also, a closed-form expression of the bit error rate (BER) and some bounds are computed.

Reducing the power of wireless terminals by adaptive baseband processing

In this paper, we illustrate specific power savings obtained from exploiting a reconfigurable mobile terminal under the 3GPP LTE standard. Building on traditional link adaptation towards maximum throughput and extended towards minimal power consumption, we add two flexible baseband components: the turbo decoder and the multiple input multiple output (MIMO) detector. Optimizing their configuration leads to larger power savings when compared to non-flexible systems only performing link adaptation. The gain observed strongly depends on the scenario. For low-activity set-ups with a few minutes of voice per day, the idle power dominates and the active data rate is relatively low. This makes analog front-end and time-domain processing dominant given their constant power consumption while MIMO detection and turbo decoding that scale with data rate play a smaller role. Still, because of its ability to improve the system spectral efficiency and hence reduce its duty cycle, an advanced MIMO detector can save 10% in power consumption, on the condition that the network requires to use MIMO. Otherwise single input single output is more power-efficient in downlink. In high-throughput scenarios, larger gains are obtained. The flexible MIMO detector can save up to 35% of average power consumption. The turbo decoding also brings some gain, saving up to 12% of power when the full bandwidth is allocated to a single user.

Implications of Passive Mixer Transparency for Impedance Matching and Noise Figure in Passive Mixer-First Receivers

In this paper, a class of passive mixer-first, LNA-less receivers is analyzed in depth. Quadrature passive mixers are shown to present the impedance of their baseband port to the RF port and vice versa. This transparency property, in combination with resistive feedback differential amplifiers, and “complex” feedback between the I and Q paths, can be used to control the impedance at the RF port. This impedance can be tuned using only baseband components (i.e., resistors). The noise limits of such an architecture are analyzed and simulated, and are shown to be comparable to standard RF-LNA-first receivers. Accounting for the higher harmonics of the LO frequency proves critical in accurately analyzing the behavior of these circuits and their ability to provide an impedance match with low noise figure. Additionally, it is shown that expanding quadrature passive mixers to harmonic rejection mixers allows for even better noise performance and wider matching range.