Dispensing with Channel Estimation…

In this article, we investigate the feasibility of noncoherent detection schemes in wireless communication systems as a low-complexity alternative to the family of coherent schemes. The noncoherent schemes require no channel knowledge at the receiver for the detection of the received signal, while the coherent schemes require channel inherently complex estimation, which implies that pilot symbols have to be transmitted resulting in a wastage of the available bandwidth as well as the transmission power

Near-field direct antenna modulation

NFDAM systems provide a unique solution for transmitting highly secured direction-dependent data and hence preventing eavesdroppers from properly demodulating the signal. A 60-GHz proof-of-concept chip was designed and measured

Tone calibration technique: A digital signaling scheme for mobile applications

Residual carrier modulation is conventionally used in a communication link to assist the receiver with signal demodulation and detection. Although suppressed carrier modulation has a slight power advantage over the residual carrier approach in systems enjoying a high level of stability, it lacks sufficient robustness to be used in channels severely contaminated by noise, interference and propagation effects. In mobile links, in particular, the vehicle motion and multipath waveform propagation affect the received carrier in an adverse fashion. A residual carrier scheme that uses a pilot carrier to calibrate a mobile channel against multipath fading anomalies is described. The benefits of this scheme, known as tone calibration technique, are described. A brief study of the system performance in the presence of implementation anomalies is also given

Coherent versus noncoherent signaling for satellite-aided mobile communications

The use of coherent versus noncoherent communications is an unresolved issue for the mobile satellite community. Should one select the more robust but less efficient noncoherent strategy for communications over satellite-aided mobile channels, or does the introduction of a space platform in the mobile link improve signal stability (both amplitude and phase) such that conventional coherent schemes become attractive? This publication tries to answer some of the questions by discussing the results from experiments using a coherent QPSK receiver. The issues discussed include items such as the measured performance in Rician fading, the link error floor in a fading environment, etc. The results are compared and contrasted with that of a noncoherent limiter/discriminator FM receiver

Doctor of Philosophy

dissertationHigh speed wireless communication systems (e.g., long-term evolution (LTE), Wi-Fi) operate with high bandwidth and large peak-to-average power ratios (PAPRs). This is largely due to the use of orthogonal frequency division multiplexing (OFDM) modulation that is prevalent to maximize the spectral efficiency of the communication system. The power amplifier (PA) in the transmitter is the dominant energy consumer in the radio, largely because of the PAPR of the input signal. To reduce the energy consumption of the PA an amplifier that simultaneously achieves high efficiency and high linearity. Furthermore, to lower the cost for high volume production, it is desirable to achieve a complete System-on-Chip (SoC) integration. Linear amplifiers (e.g., Class-A, -B, -AB) are inefficient when amplifying signals with large PAPR that is associated by high peak-to-average modulation techniques such as LTE. OFDM. Switching amplifiers (e.g., Class-D, -E, -F) are very promising due to their high efficiency when compared to their linear amplifier counterparts. Linearization techniques for switching amplifiers have been intensively investigated due to their limited sensitivity to the input amplitude of the signal. Deep-submicron CMOS technology is mostly utilized for logic circuitry, and the Moore's law scaling of CMOS optimizes transistors to operate as high-speed and low-loss switches rather than high gain transistors. Hence, it is advantageous to use transistors in switching mode as switching amplifies and use high-speed digital logic circuitry to implement linearization systems and circuitry. In this work, several linearization architectures are investigated and demonstrated. An envelope elimination and restoration (EER) transmitter that comprises a class-E power amplifier and a 10-bit digital-to-analog converter (DAC) controlled current modulator is investigated. A pipelined switched-capacitor DAC is designed to control an open-loop transconductor that operates as a current modulator, modulating the amplitude of the current supplied to a class-E PA. Such a topology allows for increased filtering of the quantization noise that is problematic in most digital PAs (DPA). The proposed quadrature and multiphase architecture can avoid the bandwidth expansion and delay mismatch associated with polar PAs. The multiphase switched capacitor power amplifier (SCPA) was proposed after the quadrature SCPA and it significantly improves the power efficiency

Noise radar technology as an interference prevention method

In some applications, such as automotive and marine/navigation, hundreds of radars may operate in a small environment (e.g., a road complex or a strait) and in an allocated frequency band with limited width. Therefore, a compatibility problem between different radars arises that is not easily solved by time, frequency, space, or polarization diversity. The advent of fast digital signal processing and signal generation techniques makes it possible to use waveform diversity to solve this problem that will be exacerbated in the next future. Ideal waveforms for the diversity are supplied by Noise Radar Technology (NRT), whose application is promising in some military applications as well as in the civilian applications considered in this paper. In addition to being orthogonal as much as possible, the random signals to be transmitted have to satisfy requirements concerning side lobe level and crest factor, calling for novel, original design and generation processes

Power Amplifiers for Next Generation Wireless Platforms

Class-E amplifier has the potential to deliver high efficiency required for the next generation wireless systems. In this journal, we discuss a novel load pull analysis technique to characterize the efficiency performance of Class-E amplifier in an outphasing power combining scheme. Class-E amplifier is not an ideal current or voltage source as is required for the traditional analysis of outphasing structures. It requires a phase modulated input signal and has a non-linear transfer characteristic which is a function of load impedance. Here we define an operating load locus based on the load pull analysis which can be used to predict the non-linear transfer function, efficiency, output power, input drive phase and many other factors associated with the outphasing class-E amplifier. This scheme could also be used to characterize any amplifier class in an outphasing structure. Finally modulation performance of Class-E amplifier using PWM technique is also presented