Digital Phase Modulation Research Articles

Performance analysis of a three-stage quadrature RC generator with operational amplifiers

This paper presents the special features of RC harmonic oscillation generators and their widespread use and in particular the quadrature generators which provide two output signals dephased at 90º or 270º. Quadrature generators can be classified as those with an aperiodic frequency-determining circuit or with a phase inverter group which are used to generate oscillations of one or more fixed frequencies. Studies of a three-stage quadrature RC generator circuit with operational amplifiers have been performed. The results obtained from the simulation and experimental studies performed are presented for the selected circuit. It can be assumed that the experimental and simulation results completely coincide to an accuracy of up to 20% for the amplitude of the generated signals and to the total accuracy for the generated frequency. Quadrature generators are very widely used in communication technology and, most importantly, in the structure of digital frequency, phase and quadrature-amplitude modulators and demodulators, in vector RLC meters and many other electronic circuits and devices in practice.

Adaptive power permutation modulation: A novel transmission technique for increased spectral efficiency over fading channels

SummaryIn this study, we propose a novel transmission technique for multiple‐input multiple‐output (MIMO) systems as a partial response to ever‐growing demand for the increased spectral efficiency. The introduced scheme, called adaptive power permutation modulation (APPM), relies on the distinct power allocations on the conventionally modulated symbols to convey a certain number of additional information bits. Unlike the traditional power allocation strategies which generally aim to combat the channel fading and entail some form of channel state information (CSI) at the transmit side, APPM utilizes different power levels to convey additional information and does not necessitate any kind of CSI at the transmitter. The proposed approach is applied to two well‐known MIMO configurations, Alamouti space‐time block coding and zero‐forcing beamforming, by embracing a general frequency‐selective fading scenario under digital phase modulation. Both the modulation order and the power allocation levels on the modulated symbols are adaptively determined based on a set of additional information bits. It is shown that in addition to the conventionally modulated symbols, an extra sequence of bits can be conveyed without any significant additional complexity where equals the number of subcarriers. Also, it is demonstrated that considerable transmit power savings can be attained when compared with the standard schemes under a certain target spectral efficiency.

A Digital PLL-Based Phase Modulator With Non-Uniform Clock Compensation and Non-linearity Predistortion

In this article, we present a low-power digital phase-locked loop (PLL)-based phase modulator targeting low error vector magnitude (EVM). We introduce a new non-uniform clock compensation (NUCC) scheme to tackle an EVM degradation resulting from the beneficial use of a time-varying sampling clock that is re-timed to the phase-modulated carrier. We also employ a phase-domain digital predistortion (DPD) to combat the intrinsic non-linearity of an LC-type digitally controlled oscillator (DCO), thus avoiding the complications of frequency-dependent calibrations. The prototype, implemented in 40-nm CMOS, modulates the carrier in the range of 2.7–3.9 GHz from a 40-MHz reference. The measured EVM is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 47 dB for a 60-Mb/s 64-PSK modulation under the case that the phase-modulated output is frequency-divided by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K=8$</tex-math> </inline-formula> , i.e., when the DCO exhibits the most significant non-linearity due to the large fractional FM bandwidth. When <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K=8$</tex-math> </inline-formula> or 4, the measured EVM remains below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 43 dB across the carrier-frequency tuning range and without re-calibrating the DCO non-linearity.

Six-channel programmable coding metasurface simultaneously for orthogonal circular and linear polarizations

Metasurfaces have intrigued long-standing research interests and developed multitudinous compelling applications owing to their unprecedented capability for manipulating electromagnetic waves, and the emerging programmable coding metasurfaces (PCMs) provide a real-time reconfigurable platform to dynamically implement customized functions. Nevertheless, most existing PCMs can only act on the single polarization state or perform in the limited polarization channel, which immensely restricts their practical application in multitask intelligent metadevices. Herein, an appealing strategy of the PCM is proposed to realize tunable functions in co-polarized reflection channels of orthogonal circularly polarized waves and in co-polarized and cross-polarized reflection channels of orthogonal linearly polarized waves from 9.0 to 10.5 GHz. In the above six channels, the spin-decoupled programmable meta-atom can achieve high-efficiency reflection and 1-bit digital phase modulation by selecting the specific ON/OFF states of two diodes, and the phase coding sequence of the PCM is dynamically regulated by the field-programmable gate array to generate the desired function. A proof-of-concept prototype is constructed to verify the feasibility of our methodology, and numerous simulation and experimental results are in excellent agreement with the theoretical predictions. This inspiring design opens a new avenue for constructing intelligent metasurfaces with higher serviceability and flexibility, and has tremendous application potential in communication, sensing, and other multifunctional smart metadevices.

Reconfigurable radar signal generator based on phase-quantized photonic digital-to-analog conversion.

A novel, to the best of our knowledge, scheme for reconfigurable radar signal generation is proposed based on the principle of photonic phase-quantized digital-to-analog conversion. Multi-level digital phase modulation with different modulation depths is combined to convert multi-channel digital data to the phase of an optical carrier. Frequency-modulated or phase-modulated radar signals are generated by beating the phase-synthesized optical carrier with a coherent reference light. The proposed radar signal generator features a simple structure, highly reconfigurable modulation format, and flexibly tunable frequency. A 3-bit photonic phase-quantized digital-to-analog converter with a 10-GSa/s sampling rate is constructed experimentally. The generation of linear frequency-modulated, nonlinear frequency-modulated, frequency-stepped, frequency-hopping, binary phase-coded, and polyphase-coded waveforms is demonstrated.

Power permutation modulation in multiple‐input multiple‐output systems

AbstractThe forthcoming communications standards are conjectured to require unprecedentedly high spectral efficiency values. Motivated by this fact, we propose a new transmission scheme for multiple‐input multiple‐output systems, which is termed as power permutation modulation (PPM). In addition to the conventional data‐carrying modulated symbols, some amount of extra information is conveyed in the distinct permutations of power allocation levels associated with the modulated symbols. The detection of the additional bits is performed by a power permutation recovery process at the receive side. Unlike the common approach, the power allocation is exploited as a new degree of freedom for carrying information without requiring any channel state information at the transmitter. The application of the introduced method is exemplified for zero‐forcing beamforming and space‐time block coding systems under digital phase modulation. It is shown that, without any important additional complexity, some notable signal‐to‐noise ratio gains (as large as 3 dB) are attained as compared to the standard approaches. An exact closed‐form result on the bit error rate (BER) of the presented PPM scheme is provided. The obtained expression is used to obtain the optimum power allocation levels such that the overall BER is minimized.

Analog and Digital Phase Modulation and Signal Transmission with Spin-Torque Nano-Oscillators

Researchers present a method of phase modulation and phase-shift keying for spin-torque nano-oscillators (STNOs), and demonstrate transmission of a voice signal (telephony) with their STNO-based gear. The key elements of the proposed method are the ability of an STNO to be synchronized by an external signal, and to shift its phase relative to the source's phase according to an additional control signal. These properties allow not only control of the phase, but also reduction of phase noise, which is a main issue for all oscillators with nanoscale dimensions. The results comprise a significant advance for wireless data and signal communication with nano-oscillators.

Ultrasonic multipath monitoring of turbulent gas flows: pulse signals correlation processing

The article proposes digital phase modulation and correlation processing of pulsed ultrasonic signals for the turbulent gas flows monitoring. Estimates of errors in measuring the relative time delay of ultrasonic pulses during multipath propagation and their interference in the receiver were made. The data obtained from the experiment show that the relative pulse delay measured in a turbulent gas flow has a resolution exceeding tenths of the carrier frequency period. As an example the possibilities of turbulence’s quantitative control the air flow boundaries of a fan are shown. The perspectives to use the developed software and hardware in flow meters and other ultrasonic control and measuring devices are discussed.

A Low Phase Noise Open Loop Fractional-N Frequency Synthesizer With Injection Locking Digital Phase Modulator

This brief presents a two stage open loop fractional-N frequency synthesizer using proposed injection locking phase modulator for low power applications. A novel low power injection locking oscillator (ILO)-based digital phase modulator (DPM) is proposed in this brief. The maximum differential nonlinearity (DNL) of proposed DPM is smaller than 0.3 degree in the whole range with 1.6 mW power consumption. An integer-N injection locking phase locked loop (ILPLL) is designed to generate the radio frequency signals for the second stage open loop frequency synthesizer. With an injection strength adjustment unit, the open loop fractional-N frequency synthesizer employing proposed DPM achieved excellent in band phase noise and instantaneous frequency switching with low power consumption. This frequency synthesizer is fabricated on 28-nm CMOS technology and its active area is 0.08 mm2. The output frequency range is from 320 MHz to 520 MHz and the power dissipation is 2.7 mW from 0.9 V supply in fractional-N mode. The measured RMS jitter integrated phase noise from 10 KHz to 40 MHz of 440 MHz and 440.4 MHz carrier frequency are 3.8 ps and 17.6 ps, respectively. The corresponding figure of merits (FoM) are −231 dB and −211 dB, respectively.

A Fully Digital Phase Modulator With a Highly Linear Phase Calibration Loop for Wideband Polar Transmitters

This brief presents a digital phase modulator for wideband polar transmitters. It adopts a digital-to-time converter (DTC) and a highly linear phase calibration loop that improves phase resolution for high data-rate systems. The proposed 10-bit DTC consists of a coarse 5-bit cascaded delay line and a fine 5-bit digitally controlled delay line. This DTC achieves a fine delay resolution with digitally controlled varactors and is capable of introducing incremental delays as small as 2.49 ps. A phase calibration loop based on an advanced successive approximation register (SAR) time-to-digital converter (TDC) is nested inside the phase modulator and sets the DTC output phase accurately across the range of input digital codes. The SAR TDC also compensates for any process, voltage, and temperature variations. By using the proposed SAR TDC-based calibration loop, the phase modulator can achieve a high sampling rate and a fine phase resolution. This was possible because the number of phase comparisons of the SAR TDC has been significantly reduced. The phase modulator achieves 0.61 degrees root-mean-square phase error and a 30 MS/s sampling rate at the carrier frequency of 600 MHz while consuming 9.4 mW. This phase modulator is implemented in a 180-nm CMOS technology and occupies 0.19 mm2.

A High-Speed DSP Engine for First-Order Hold Digital Phase Modulation in 28-nm CMOS

Conventional delay-based digital phase modulators use a zero-order hold (ZOH) phase control word to modulate the square-wave RF carrier. Recently, new architectures capable of performing first-order hold (FOH) digital phase modulation have been proposed, thus improving the wideband performance to a level suitable for 5G base stations. While currently available literature focuses on the generic operation principle, this brief details the first on-chip implementation of the DSP engine required for actual FOH computations. The circuit is based on a simple iterative algorithm, which can be pipelined for high-speed operation. The DSP engine has been integrated as part of a prototype 5G base-station outphasing transmitter, fabricated in 28-nm CMOS. When processing a 100-MHz orthogonal frequency-division multiplexing signal, the DSP achieves an adjacent-channel leakage ratio of −53 dBc, which is 12 dB better than with conventional ZOH phase modulation. Furthermore, the system enables flexible upconversion to any frequency between 0.35 and 2.1 GHz from a fixed 1.5-GHz reference clock. The power consumption of a single engine is lower than 18 mW.

On Numerical Evaluation of Packet-Error Rate for Binary Phase-Modulated Signals Reception over Generalized-K Fading Channels

We present a numerical evaluation of packet error rate (PER) for digital binary phase modulations over wireless communication channels. The analysis is valid for a quasistatic fading communication channel, where multipath fading and shadowing appear simultaneously. The approach is based on numerical evaluation of signal-to-noise ratio threshold that is further used in PER computation. We analyze the threshold and PER dependence on signal power, multipath fading and shadowing severity, as well as packet length.

Digital Phase Modulation and Correlation Processing of Ultrasound Signals for Pulsed Measurements in an Inhomogeneous Medium

A method and hardware for ultrasonic control of an inhomogeneous gaseous medium are presented. An algorithm based on digital phase modulation of pulse signals and their correlation processing is used to increase the resolution of an ultrasonic device. The algorithm allows high-resolution measurements of the time delay between the ultrasound pulses that arrive at a receiver along different propagation paths in an inhomogeneous medium. It is shown that it is possible to measure small values of time delays by analyzing the asymmetry of the cross correlation functions of signals. Laboratory experimental measurements carried out under scattering of ultrasound in an inhomogeneous airflow are described. The possibility of measuring relative time delays of 3–5 μs of pulses at the 40-kHz carrier frequency of ultrasound is shown.

QPSK MODULATOR FOR X-BAND IRS SATELLITES

The current work is applied to remote sensing satellites. IRS satellites in the orbits are not only sending data to Indian ground stations but also to other international stations for passing data to different countries. Multiple solid-state cameras are carried by the IRS satellite to operate in the visible and infrared bands that acquires imageries for earth survey such as agriculture and geology. Digital phase modulation that allows transmitting discrete phase angles is more popular and easily adaptable. Among the PSK schemes, the QPSK is adopted as it is relatively easy to realize and gives optimum performance in terms of power and bandwidth compared to other modulation schemes. The unit is realized in MIC form, which is smaller in size and weight compared to earlier ones. The data obtained from onboard camera is transmitted to ground on X-band carrier (8-8.4GHz). Keeping in view the future satellite applications, a QPSK modulator is designed with LVDS interface circuit for a data rate of upto 105 Mbps. The microwave simulation software used is EESOF.

Digital Interpolating Phase Modulator for Wideband Outphasing Transmitters

Radio transmitters are evolving towards digital-intensive solutions to exploit reconfigurability and benefit from CMOS process scaling. Outphasing has been identified as a suitable candidate for digital wideband transmitters. However, with recent digital-intensive outphasing transmitters the achieved performance in terms of adjacent channel leakage ratio (ACLR) has been limited. This paper identifies the sampling images of the modulating phase signal as the main factor limiting the ACLR of digital outphasing transmitters. We present a new digital interpolating phase modulator architecture, capable of providing significantly better sampling image attenuation. When evaluated in outphasing configuration with a 100 MHz OFDM signal at the carrier frequency of 2.46 GHz, and 10-bit phase resolution, the proposed solution achieves an ACLR of $-$ 59 dBc, compared to $-$ 43 dBc achievable with the phase modulator architecture utilized in state-of-the-art digital outphasing transmitters. The proposed digital interpolating phase modulator is also capable of custom carrier generation, a straightforward method for generating an arbitrary carrier frequency up to 1.25 times the phase modulator sampling rate.

Performance analysis of a joint estimator for timing, frequency, and phase with continuous‐phase modulation

Performance analysis is presented for the joint estimation of symbol timing, frequency offset, and phase offset with continuous-phase modulation. In this study, undesirable influences on parameters to be estimated, which arise from the inaccuracy of the already estimated parameters, are computed mathematically. Based on performance analysis, a conditional Cramer-Rao bound (CRB) is put forward, and a hypothesise is made that phase offset variance with frequency error present should match with the conditional CRB for any digital phase modulation. Moreover, the hypothesis is manifested by analysing the log-likelihood function in a more general mathematical manner. To alleviate the influences, a data-aided acquisition and phase-locked loop tracking algorithm is proposed. The results of Monte Carlo simulations are presented, showing good agreement with theoretical analysis. Simulation results also show that the proposed algorithm can improve performance in terms of phase error variance at the expense of a high signal-to-noise ratio threshold.

A Sensitive Method to Measure the Integral Nonlinearity of a Digital-to-Time Converter Based on Phase Modulation

A digital-to-time converter (DTC) produces a time delay based on a digital code. Similar to data converters, linearity is a key metric for a DTC and it can be characterized by its integral nonlinearity (INL). However, measuring the INL of a subpicosecond-resolution DTC is problematic, even when using the best available high-speed oscilloscopes. In this brief we propose a new method to measure the INL of a DTC by applying digital phase modulation and measuring the output spectrum with a spectrum analyzer. The frequency selectivity of this method allows for an improved measurement resolution down to a few femtoseconds and allows measuring an INL below 100 fs. The proposed method is verified by behavioral simulations and is employed to measure the INL of a high-resolution DTC realized in the 65-nm CMOS, with a time resolution of 25 fs and a standard deviation of 27 fs.

Double closed-loop resonant micro optic gyro using hybrid digital phase modulation.

It is well-known that the closed-loop operation in optical gyros offers wider dynamic range and better linearity. By adding a stair-like digital serrodyne wave to a phase modulator can be used as a frequency shifter. The width of one stair in this stair-like digital serrodyne wave should be set equal to the optical transmission time in the resonator, which is relaxed in the hybrid digital phase modulation (HDPM) scheme. The physical mechanism for this relaxation is firstly indicated in this paper. Detailed theoretical and experimental investigations are presented for the HDPM. Simulation and experimental results show that the width of one stair is not restricted by the optical transmission time, however, it should be optimized according to the rise time of the output of the digital-to-analogue converter. Based on the optimum parameters of the HDPM, a bias stability of 0.05°/s for the integration time of 400 seconds in 1 h has been carried out in an RMOG with a waveguide ring resonator with a length of 7.9 cm and a diameter of 2.5 cm.

Wavefront watermarking of technical and biological samples using digital random phase modulation and phase retrieval

A technique for digital watermarking of smooth object wavefronts using digital random phase modulation and multiple-plane iterative phase retrieval is demonstrated experimentally. A complex-valued watermark is first encrypted using two random phase masks of known distributions before being superposed onto a set of host wavefront intensity patterns. Encryption scaling factor and depth of randomization of the masks are optimized such that the amplitude and phase watermarks are decrypted successfully and are not distorting the host wavefront. Given that the watermarked intensity patterns and the numerous decryption keys are available (i.e. distances between recording planes, light source wavelength, pixel size, random phase masks and their distances to the planes are all known), increasing the number of watermarked patterns used results in enhanced quality of decrypted watermarks. The main advantage of wavefront watermarking via the phase retrieval approach compared to the holographic approach is the avoidance of reference wave-induced aberration. Watermarking of wavefronts from lenses and unstained human cheek cells demonstrate the effectiveness of the technique.

Improvements Encoding Energy Benefit in Protected Telecommunication Data Transmission Channels

The features of using noise resistant encoding for protection from errors in digital data transmission channels with phase modulation have been analyzed. The building principles and encoder and decoder schemes of turbo-code were observed. The digital data transmission system with outer and inner turbo-encoder has been developed. The recommendations to type and structure of cascade encoder components have been given. Analytical relationships and research results describing bit error probability of cascade turbo-encoder components are represented. By using simulative modeling tools Matlab-Simulink the basic characteristics and features of digital transmission channel with cascade turbo-encoding and digital phase modulation were researched. The energy benefit gained by using cascade structures has been defined.