Digital Interpolating Phase Modulator for Wideband Outphasing Transmitters

Main lobe shifting and splitting phenomena of Airy beams are theoretically investigated based on the spatial light modulator (SLM) method. By digitally modulating the phase masks on the SLM, the single main lobe of the 2D symmetric Airy beam shifts to its neighboring side lobe. This results in the main-lobe splitting and the formation of a two-main-lobe state. These two main lobes further split into four while appropriately setting the phase modulation parameters. Meanwhile, the main lobe intensity decreases from 1.529 to 0.361a.u. as the incident Gaussian beam's amplitude is 1. Therefore, one, two, or four main lobes can be obtained in Airy beams, and the corresponding intensity can be flexibly modulated by digital phase masks without moving the obstacle. Furthermore, a set of Airy beams with single main lobes and their corresponding splitting are realized by periodically setting the propagation distance. This further improves the modulation flexibility of the main lobe intensity. In our work, the number and intensity modulations of main lobes in Airy beams may have significant potentials for optical communication devices, such as tunable lasers and optical demultiplexers.

This paper presents a low power, high speed SiGe DDS MMIC with 9-bit phase and 7-bit amplitude resolutions. This DDS MMIC is the first reported GHz range output DDS with direct digital frequency and phase modulation capabilities. Using more than eight thousand transistors, the DDS MMIC includes a 9-bit CLA accumulator for phase accumulation, a 9-bit CLA adder for phase modulation and a 7-bit sine-weighted DAC. The core area of the DDS occupies 1.7times2.0 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The DDS consumes low power of 2.0 W under a 3.3 V single power supply even with the added modulation blocks. The narrow band spurious-free-dynamic range (SFDR) is measured as 35 dBc with the maximum update frequency of 2.9 GHz. The DDS MMIC is packaged and tested in an LCC-44 cavity.

There have been few papers researching on effects of HPA nonlinearity towards system performance of digital phase modulation systems based on DSSS in satellite communication channel. System performance comparison of four digital phase modulation manner (based on DSSS), BPSK, QPSK, OQPSK and MSK are investigated in our paper. Two types of HPA are used in our simulation, TWTA (Traveling Wave Tube Amplifier) and SSPA (Solid State Power Amplifier). Well-known SALEH model is used for TWTA. RAPP model, which consider AM/AM distortion only and modified RAPP model, which consider both AM/AM and AM/PM distortion are adopted towards SSPA. We mainly focus on eye-diagrams, PSD and BER performance when HPA works on saturation or serious saturation area. Comparisons are made among four phase modulation manners. At last some useful and important conclusions are gotten.

19 - Digital modulation

Precise signal processing schemes for resonator fiber optic gyro (R-FOG) with bipolar digital serrodyne phase modulation technique are proposed. One scheme is to suppress the noise induced by higher harmonics of the frequency used to extract the rotation signal when the bipolar digital serrodyne modulation technique is used. The other scheme is to increase the stability of the control signal for the amplitude adjustment of the phase modulation waveform, in which a lock-in reference waveform with 90° out of phase compared with the modulation waveform is introduced.

The performance of constant envelope digital partial response continuous phase modulation (PRCPM) with two-bit differential detection and offset receiver diversity is theoretically analyzed in fast Rayleigh fading AWGN (additive white Gaussian noise) channels. A simple closed-form expression for the probability of error is derived and evaluated for cases of practical interest to researchers and designers of land mobile radio systems. It is shown that the dynamic BER performance is considerably improved using the offset diversity scheme. Thus, many new PRCPM signals having compact power spectra can be used in future mobile radio systems. >

A fully digital burst-mode handheld transmitter with power amplifier for the 900-MHz band is presented. The transmitter front-end consists of a digital polar modulator which uses pulse width modulation (PWM) for the amplitude modulator. Phase modulation (PM) is implemented by shifting the carrier in time. Both the PWM and the PM are implemented using asynchronous delay lines which allow time resolutions down to 10 ps without the need for high-frequency clock signals. The modulated signal is amplified by a Class B amplifier which uses power combining to reach watt-level output power. The transmitter is implemented in standard CMOS technology. When transmitting a modulated signal with a peak-to-average power ratio (PAPR) of 10.3 dB and 5-MHz bandwidth, the burst-mode transmitter meets the stringent error-vector-magnitude (EVM) specifications of 5.6% at 23.1-dBm average output power with 11.7% power added efficiency (PAE).

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.

Summary form only given. Future mobile radio systems are expected to provide high-quality voice and high-speed data transmission and to be integrated into the digital communication networks in several countries. The performance of some digital modulation techniques that are relevant for future mobile radio systems is studied. These techniques are characterized by having a constant envelope signal to reduce the effect of nonlinearity and fading and a compact RF power spectrum to reduce adjacent channel interference. Most digital partial-response continuous-phase modulation (PRCPM) techniques such as 2 RC, 2 SRC, 2 RC, 3 SRC, GMSK, and GTFM have the above properties. Discriminator detection of these techniques is analyzed in fast Rayleigh fading characterizing land mobile radio channels. Approximate closed-form expressions for the probability of error are derived and numerical results are presented for land mobile radio systems. >

Digital phase modulation is a class of power‐ and bandwidth‐efficient modulations widely used in telecommunications. In this article, the reader will first be introduced to the general concept of digital phase modulation, and the notions of bandwidth and power efficiency. The commonly used class of digital phase modulation schemes, that is, M ‐ary phase shift keying (MPSK), are described in detail. Their signal waveform expressions, signal constellations, and power spectral densities (PSDs) are presented. The block diagrams of the modulator and the optimal coherent demodulator are presented and explained. The symbol and bit error rate (BER) of the demodulator is derived and symbol error probability graphs are given. Widely used binary PSK (BPSK) and quaternary PSK (QPSK) are treated as special cases of MPSK. Next, differential PSK schemes are introduced, which are particularly useful in wireless fading channels. Their symbol error probability expressions and graphs are presented. At the end, two important phase modulation variations, namely, offset QPSK (OQPSK) and π/4‐DQPSK, and the advanced continuous‐phase modulation (CPM), including multi‐ h CPM, are briefly introduced.

The system takes advantage of the fact that a phase-modulated carrier signal will produce equivalent frequency modulation, where the change of frequency is proportional to the time rate of change of the phase variation. A mirowave carrier frequency, FC, is shifted in a single sideband generator to a frequency, FC+FM. The upper sideband is transmitted through the phase modulating medium and then mixed with the original carrier frequency. The difference frequency FM contains the phase modulation information and, after preamplification, the signal is put through a wide-band limiter-discriminator of center frequency, FM. The discriminator output voltage will be directly proportional to the rate of phase change. To compensate for the time rate of change dependency, the discriminator output is followed by an integrating network (E/sub 0/~1/f) which will produce an output voltage proportional to the phase change only. Calibration is accomplished by imposing a known amount of phase modulation on the sideband modulating signal FM and observing the system output signal. This measuring scheme has been built in the 70 Gc/s band and is capable of following a wide range of phase changes over microsecond periods.

In this paper, we show that amplitude transitions that are inherent to the multilevel outphasing radio transmitter architecture distort the transmitted signal due to time-domain discontinuities. In order to address this challenge, we propose a new transmitter architecture called tri-phasing which avoids discontinuities in signal waveforms and thus achieves significantly better linearity than multilevel outphasing. The output wave-form in tri-phasing can be made continuous by representing the baseband signal with three components. One of the three components is amplified by discrete amplitude steps, whereas the other two are used to compensate the instantaneous shift in the output waveform due to the discrete amplitude step and to provide fine amplitude resolution. An implementation of the tri-phasing transmitter requires three phase modulators and additional digital signal processing. The system-level simulations performed in this paper demonstrate that the ACLR of a multilevel outphasing transmitter with 4 amplitude levels and 10-bit phase resolution is limited to -48 dBc, when simulated with a 100 MHz carrier-aggregated LTE downlink signal at 2.46 GHz carrier frequency. The proposed tri-phasing transmitter achieves -58 dBc ACLR with the same simulation parameters, indicating that continuous amplitude transitions can significantly improve the transmitter linearity.

A Sub-GHz multimode digital polar transmitter for 802.11ah and NB-IoT applications

TRW is developing High Temperature Superconducting (HTS) electronics to dramatically improve the performance of space- based communications systems. These systems demand high speed analog-to-digital converters, high speed digital multiplexers, and quadriphase modulation of rf carrier signals. TRW has demonstrated an HTS high-speed multiplexer and a digital phase modulator that operates at microwave frequencies. The latter is the fundamental building block of a Quadriphase Modulator Exciter (QME). TRW has also developed an HTS cryogenic packaging subsystem which uses a commercially available palm-sized cryocooler. This package represents the first demonstration of an HTS self-supporting system. Package verification tests revealed that the package is capable of supporting high speed I/O and demonstrates reliable connectivity through multiple interfaces. The successful operation of a digital phase modulator has been demonstrated with this package.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper presents a fully digital polar up-converter for wireless transmission in the GHz range. The system is designed to drive two class-E power amplifiers (PAs) with a power combiner. It uses baseband pulse width modulation (PWM) for the amplitude modulation (AM), whereas phase modulation (PM) is implemented by shifting the RF carrier in time. Both the PWM and the PM are implemented using asynchronous delay lines which allow time resolutions down to 10 ps without the need for any reference frequencies higher than the carrier frequency. The system supports a continuous range of carrier frequencies from 946 MHz up to 2.4 GHz. It also supports a continuous range of sampling frequencies, which allows trading off signal quality for PA efficiency. The modulator has been implemented in 65-nm low-power CMOS. Measurements using 64-QAM OFDM signals show error vector magnitude (EVM) values ranging from 1.90% (-34.4 dB) for 5-MHz bandwidth signals at 946 MHz to 6.08% (-24.3 dB) for 20-MHz bandwidth signals at 2.4 GHz.