Prototype Transmitter Research Articles

Intelligent Transmitter of Field (ITF) Based on Microcontroller for Data Acquisition in PV Solar Plants

In this article the design of a prototype of an Intelligent Transmitter of Field (ITF) is presented. The objective of this ITF is to be used as a data acquisition in a PV solar plant implemented at the new Campus, the Diagonal-Besòs Campus, of the Technical University of Catalonia – BarcelonaTech (UPC). Aspects like power consumption of the electronic circuits, energy supply through the wires of communication of the transmitter, the coexistence in these wires of analogical signals of measurement and digital signals of communication, etc., are essential to get the foreseen objective. The article seeks, also, to contribute to obtain a practical and, at the same time, didactic solution for a problem that has been one of the main challenges in instrumentation field for data acquisition in renewable energy systems.

An FLL Providing Real-Time Frequency Calibration for OOK Power Oscillator Transmitters

A frequency-locked loop (FLL) is proposed to provide a real-time frequency calibration for OOK power oscillator transmitters. This FLL incorporates a pulse-width detector (PWD) based on Time-Registers (TRs) to discriminate accurately between the carrier frequency and the preset target frequency during the data modulation. As a result, frequency calibration can be performed simultaneously with data modulation without interruption. A prototype of an OOK power oscillator transmitter integrated with the proposed FLL is implemented with onboard discrete electronic elements for demonstration. The measurement indicates that the FLL can accurately lock to a carrier frequency of 160MHz despite electromagnetic (EM) interference in the loop antenna of the transmitter. In contrast, with EM interference and charge leakage, the carrier frequency differs from the expected value by about 1 MHz when the FLL is disabled.

Load and Power Indexed Predistortion for Improved Robustness to MIMO Channel Conditions

This letter presents an effective digital predistortion (DPD) solution to the problem of channel-dependent variations in the linearity of multiple-input-multiple-output (MIMO) transmitters. Such variations arise because: 1) conventional MIMO precoding results in large disparities in the average-power levels across chains and 2) antenna crosstalk causes significant active load modulation at the power amplifier (PA) output. Consequently, PA nonlinearity is channel dependent and cannot be compensated using static DPD. In this work, we propose a DPD solution that is a function of the estimated average reflection coefficient at the antenna as well as the PA average input power, which thus accounts for the channel conditions and antenna crosstalk. The proposed solution is validated through experiments on a MIMO transmitter prototype across varying channel conditions.

Development of Transmitter and Receiver With Set Partitioning 64APSK Coded Modulation Designed on Basis of Channel Capacity

In this paper, we present a prototype transmitter and receiver with set partitioning (SP)-64 amplitude and phase shift keying (APSK) coded modulation we developed for expanding satellite transmission capacity. SP-multi-level coded modulation is a transmission scheme that can improve noise immunity by properly combining a modulation scheme, bit allocation, and error-correction codes. We designed SP-64APSK coded modulation on the basis of channel capacity for expanding satellite transmission capacity. We confirmed that it has higher robustness to additive white Gaussian noise (AWGN) than DVB-S2X’s 64APSK modulation with Gray mapping through computer simulation. We also developed a prototype transmitter and receiver to implement our SP-64APSK coded modulation and evaluated its transmission performances in an AWGN channel and in a non-linear channel simulating 12-GHz-band satellite transponder characteristics. We describe the method of designing our SP-64APSK coded modulation through computer simulation, the modulation/demodulation process, and transmission performances of the prototype transmitter and receiver. We also indicate that 8K ultra-high definition television (UHDTV) with an encoded bit rate of 150 Mbps can be transmitted using the prototype within 34.5 MHz, which is the bandwidth of a single transponder for satellite broadcasting in Japan.

Massive MIMO Precoding Methods That Minimize the Variation in Average Power and Active Impedance With Channel Conditions

This article investigates the impact of precoding on the performance of massive multiple-input multiple-output (mMIMO) transmitters exhibiting nonnegligible antenna crosstalk. For this, a new metric, called the average active impedance, is introduced to quantify the extent of load modulation as a function of the antenna S-parameters and the employed precoding. The new metric is then used to investigate the load modulation under conventional precoding schemes. It is shown that these precoders yield large disparities in average-power levels across the radio frequency (RF) chains, which results in substantial performance variations with channel conditions. Based on this investigation, we propose three new precoding schemes that yield equal average-power (EP) levels across all RF chains, independent of the channel conditions. Numerical simulations and experiments conducted on an mMIMO transmitter prototype confirmed that the proposed schemes improve the transmitter’s resilience to the variation in channel conditions.

Design and Comparative Study of Voltage Regulation-Based 2-Tap Flexible Feed-Forward Equalizer for Voltage-Mode Transmitters

Herein, the analog-based, 2-tap feed-forward equalization (FFE) voltage-mode transmitter using dual supply/ground voltage regulation is presented. In an FFE data modulator, the data are divided into transition and non-transition segments, and are transmitted to the main- and post-tap drivers. By using dual voltage regulation, flexible FFE strength adjustment is possible without process dependency, and the short-current path is eliminated, thus improving the overall energy efficiency. Furthermore, this structure with independent impedance calibration loops has good on-resistance and return loss characteristics, thereby securing signal integrity. In addition, by regulating the supply/ground voltages, the output swing and common-mode voltage can be adjusted independently. Therefore, our transmitter can serve multiple standards and channel environments with a single design. To verify the effectiveness of our method, we designed a prototype of the source-synchronous transmitter in a 65 nm CMOS process, and its performance was compared with that of a conventional FFE design. The simulation results show that the proposed design has better on-resistance, return loss, and FFE controllability, and it has an energy efficiency of 2.23 pJ/bit at 20 Gb/s.

Model, Design, and Testing of an Electret-Based Portable Transmitter for Low-Frequency Applications

Submarine communication and geologic examination in deep earth are challenging because high-frequency electromagnetic (EM) waves with short wavelength can be blocked by soil and seawater, as a result, the low-frequency (LF) waves are preferred in these applications. However, the conventional LF transmitter facility requires size on the scale of the wavelength (here, >1 km), making portable transmitters extremely challenging. To greatly decrease the size of the conventional LF communication system, this article introduces a novel LF transmitter based on electret, which applies mechanical motion to accelerate the charges on the polymer electret and realize the high-efficiency generation of EM fields. Moreover, a magnetic field analytical model is established to analyze the influence of structure parameters, shapes, rotation frequency, and stacking mode on the EM signals' generation and propagation, in terms of not only distance but also orientation. Finally, an electret-based mechanically actuated transmitter prototype is built to verify the correctness and feasibility of the design.

Rapid Prototyping and Validation of FS-FBMC Dynamic Spectrum Radio With Simulink and ZynqSDR

This article presents the research carried out in developing and targeting a novel real-time Dynamic Spectrum Access (DSA) Frequency Spread Filter Bank Multicarrier (FS-FBMC) transmitter prototype to programmable ‘ZynqSDR’ Software Defined Radio (SDR) hardware, and introduces a series of experiments used to validate the design’s ‘cognitive’ DSA capabilities. This transmitter is a proof of concept, that uses DSA techniques to enable Secondary Users (SUs) to access the band traditionally used for FM Radio broadcasting (88-108 MHz), and establish data communication channels in vacant parts of the FM Radio Primary User (PU) spectrum using a multicarrier modulation scheme with a Non Contiguous (NC) channel mask. Once implemented on the hardware, the transmitter is subjected to various FM Radio environments sampled from around Central Scotland, and it is demonstrated that it can dynamically adapt its NC transmitter mask in real time to protect the FM Radio signals it detects. A video is presented of this dynamic on-hardware spectral reconfiguration, and the reader is encouraged to view the video to appreciate the responsiveness of the design. An investigation into potential FBMC guardband sizes is carried out, with initial findings indicating a guardband of 200 kHz (either side of an FM Radio station) is required in order to prevent interference with the PUs. This article also demonstrates the capabilities of the MATLAB and Simulink Model Based Design Zynq-Based Radio workflow, and provides a case study and reference design that we feel other researchers working in this field can benefit from.

A 50–112-Gb/s PAM-4 Transmitter With a Fractional-Spaced FFE in 65-nm CMOS

This article presents a 50–112-Gb/s current-mode four-level pulse amplitude modulation (PAM-4) transmitter with a two-tap fractional-spaced feed-forward equalizer (FFE). The principle analysis shows that the fractional-spaced FFE can provide an extended compensation range beyond the Nyquist frequency without amplifying noise. For the transmitter prototype implementation, the tap delay is adjusted by a coarse–fine capacitor array-based delay cell located in the quarter-rate clock path. Dynamic latches, pseudo-AND2s, and bandwidth-enhanced 4:1 multiplexers are employed to guarantee an adequate timing margin and a sufficient bandwidth for the data rate of 112 Gb/s. A linearity-optimized FFE driver is employed to overcome the current compression caused by the channel-length modulation. Fabricated in a 65-nm CMOS process, the measurement results show that the proposed fractional-spaced FFE can significantly improve the eye-opening in terms of expanding the eye width and optimizing the eyelid thickness. The PAM-4 transmitter can operate in both full-rate PAM-4 and half-rate NRZ modes, achieving a maximum data rate of 112 Gb/s with an energy efficiency of 2.17 pJ/bit.

A Pulse-Modulated Polar Transmitter Using Direct Digital Synthesis for 5G NR Mobile Applications

This brief presents a pulse-modulated polar transmitter using direct digital synthesis (DDS) for 5G NR mobile phone applications. In contrast to the conventional radio-frequency transmitter that requires high-resolution digital-to-analog converters (DACs) to maintain signal fidelity, the proposed transmitter only needs high-speed but low-resolution DACs for DDS. A transmitter prototype was developed and tested with a 5G NR 20-MHz bandwidth signal at the carrier frequency of 836.5 MHz. The transmitter achieved the adjacent channel leakage ratio (ACLR) of −31.9 dBc using the 4 GS/s DACs with resolution of just 4 bits without the use of digital predistortion or other linearization techniques.

12 Gbit/s three‐tap FFE half‐rate transmitter with low jitter clock buffering scheme

A 12 Gbit/s feed-forward equalisation (FFE) transmitter has been designed in 65 nm CMOS process. The three-tap/half-rate highspeed tap signal generation technique for the segmented FFE driver is presented. A clock buffer scheme to make the equivalent signal transition for each segmented unit contributes to a low jitter performance. The measurement results show 9.31 ps RMS jitter at 12 Gbit/s after equalisation and the horizontal eye-opening is 0.204 UI at 10 -12 BER. The prototype transmitter occupies 0.042 mm 2 and consumes 1.58 pJ/bit.

Propagation measurements for a LoRa network in an urban environment

LoRa is a relatively new proprietary communication technology that allows long-range communication distances while consuming very little power. It utilizes license-free Industrial, Scientific and Medical ISM frequency bands to exchange information at low data rates. LoRa is favourable when looking for limited exchange of data and low-cost devices and infrastructure. This work presents some preliminary propagation measurements in a typical urban environment by using prototype transmitters and receivers working in a private network. Results highlight that LoRa can be used as a communication technology for different ad-hoc networks deployed in an urban area.

Two-phase flow experiments with Coriolis Mass Flow Metering using complex signal processing

Abstract— Two-phase (gas/liquid) flow is common in many industrial applications but its measurement remains challenging for Coriolis mass flow meters (CMFM), especially for high Gas Void Fraction (GVF). In this paper, we present experimental results applying previously developed complex signal processing techniques for tracking the rapidly changing sensor signals generated by two-phase flow. The techniques are implemented in a new System-on-Chip (SOC) prototype transmitter connected to a commercial Coriolis flow tube. Experiments have been carried out over a range of single phase and two-phase (water/air) flows. The signal tracking as well as mass flow rate and density measurement performance is compared with that of a laboratory version of a commercial Coriolis transmitter with two-phase flow capability. The results show that the complex bandpass algorithms, coupled with flowtube control algorithms, reduce the standard deviation of the mass flow measurement by a factor of 3 or more in 50% of the experiments undertaken. For the density measurement, the corresponding reduction in standard deviation is by a factor of 6.

Prototype of multifunctional transmitter with Rejection of disturbances

The industrial instruments found in the different industrial processes allow supervisory and control actions to be carried out. These elements are usually composed of an electronic circuit, which varies according to the specifications given by the manufacturer. Another factor that influences the design of a circuit for elements of this type is cost, since, at a lower cost, electronic elements are susceptible to fail for reasons such as electric fields, motor interference or environmental conditions. This problem limits the operation of the instrument and reduces its useful life, which causes unnecessary stops of the automated processes increasing the cost of producing a product. Some partial solutions to this problem have been obtained by means of the implementation of additional circuits such as protections or filters, although the number of unexpected stops of the process is reduced, even this type of failures occur. This paper proposes an alternative solution to the problem through a low cost prototype, which has a mechanism for rejection of disturbances that increases the accuracy and precision of an instrument compared to the low-cost instrument technology developed so far.

A Multiphase Digital Pulsewidth Modulated Polar Transmitter Architecture With Reactive Combiner for Improved Efficiency

This paper presents a new method of reactive-combiner structure to be used as part of a multiphase digital pulsewidth modulated polar transmitter (DPWMPT). It overcomes the limitations of previous implementations of the multiphase pulse-modulated polar transmitter related to terminating pulsewidth modulation (PWM) harmonics located outside the passband, thereby improving both PWM harmonic suppression by using multiphase aliasing-free digital PWM technique and increasing overall efficiency by using reactive combining. For validation, a prototype transmitter was implemented and tested with a 64-QAM 20-MHz bandwidth long-term evolution (LTE) downlink signal with a 7.5-dB peak-to-average power ratio at 2140 MHz. The prototype dual-phase DPWMPT architecture achieved an output power level of 37 dBm and power-added efficiency of 33.5% while passing the stringent spectral requirements of the LTE standard for small-cell base stations using only simply memoryless predistortion correction.

Gibbs-Phenomenon-Reduced Digital PWM for Power Amplifiers Using Pulse Modulation

The pulse-modulated polar transmitter (PMPT) uses radio-frequency (RF) phase modulated signal with pulse-width modulated envelope to drive a power amplifier (PA) as a switch to achieve high linearity and high efficiency. However, as the signal bandwidth increases, various non-idealities limit the performance of the PMPT architecture. In this paper, a Gibbs-phenomenon reduction filter is proposed with a partial Fourier series of digital pulse-width modulation (PWM) such that the pulsed signal is more immune to the distortion in nonlinear high-efficiency RF PAs. For validation, a prototype transmitter was tested with a 20-MHz bandwidth 256-QAM 5G new radio (NR) signal at 2.14 GHz. The proposed method achieved a drain efficiency of 28.3%, error vector magnitude (EVM) of 1.67%, and adjacent channel leakage ratio (ACLR) of -45.4 dBc at an output power of 18 dBm using the prototype transmitter. Linearity requirements for base stations were met without the use of any digital predistortion methods.

DDS-PLL Phase Shifter Architectures for Phased Arrays: Theory and Techniques

The main purpose of this paper is to review the framework behind direct digital synthesizer phase-locked loops (DDS-PLLs), as well as to provide a set of novel techniques that can be used during the development and the deployment of phased arrays based on local oscillator (LO) phase shifting approaches. A beam steering transmitter prototype employing our revised DDS-PLL architecture and the experimental results obtained during its characterization are presented. The main contribution of the proposed implementation consists in showing that the output phase increments of the DDS-PLL are unaffected by the frequency multiplication operated by the PLL. The proposed prototype is centered at 3.350 GHz and allows to independently set the phase of its four LOs at 2.453 GHz with an 8-bit resolution. The DDS-PLL architecture is frequency-independent, and the modular structure of its phase control units allows to achieve different phase resolutions with a very small redesign effort.

A 32-Gb/s C2C-DAC-Based PAM-4 Wireline Transmitter With Two-Tap Feed-Forward Equalization and Level-Mismatch Correction in 28-nm CMOS

This letter presents a C2C-DAC-based PAM-4 wireline transmitter that utilizes capacitor-weighting within a predriver stage for multitap multilevel signal summation in charge domain at the transmitter front end. Such a unique approach isolates the signal summing node from the output to alleviate bandwidth limitation and also inherently provides passive voltage-scaling and level-shifting at the predriver output without sacrificing its speed. A level-mismatch-correction scheme is adopted to effectively enhance PAM-4 signaling quality. Implemented in a 28-nm CMOS, the designed transmitter prototype achieves a peak data rate of 32 Gb/s and an energy efficiency of 2.1 mW/Gb/s.

Doherty Transmitter Based on Monopole Array Antenna Active Load Modulation

This letter presents a new antenna topology to implement the load modulation in the Doherty transmitter, which resulted in enhancing the bandwidth compared to previous works. The active load modulation is realized by using a monopole array antenna, which serves as both Doherty combiner and wave radiator. The load impedances of amplifiers can be dynamically tuned through the mutual coupling of the array elements. Detailed design equations and procedures are developed. For verification, a Doherty transmitter operating at 1.95–2.10 GHz has been designed and fabricated using GaN HEMT transistors. The prototype transmitter exhibited a power-added efficiency of 53% at peak power level and maintained an efficiency of 43% at 6.8-dB backoff, over the frequency band of 1.95–2.10 GHz.

A Multilevel Pulse-Modulated Polar Transmitter Based on a Doherty Power Amplifier and Memoryless Digital Predistortion

This letter presents an aliasingfree multilevel pulse modulation (MLPM) architecture to implement a linear Doherty power amplifier (PA). This letter is believed to be the first reported results of this type of Doherty architecture to achieve linear amplification rather than the usual situation of a continuous amplitude modulated carrier and continuous load modulation. Our results show that both high efficiency and good linearization can be achieved with simple memoryless digital predistortion. Doherty operation with MLPM is believed to have benefits in linearization due to the MLPM discrete drive as less power is dissipated by the PA, leading to less thermal-related memory effects. A prototype transmitter system is constructed using a commercially available Doherty PA for validation. Measurements are performed using a 64-QAM long-term evolution (LTE) downlink signal at 2140 MHz with 20-MHz bandwidth. The overall system achieved an output power level of 40.1 dBm with a power-added efficiency of 39.5% while passing the −45-dBc downlink spectral requirements of the LTE standard.