N-way Digitally Driven Doherty Power Amplifier Design and Analysis for Ku band Applications

With an increasing interest in backwards compatibility for existing satellites and the emerging satellite markets, wireless transceivers at Ku band are increasing in popularity. This paper presents the design of a four-way digitally driven Doherty amplifier, aimed at applications in Ku-band. Single tone measurements indicate a maximum drain efficiency of 53.4% at a maximum of 19.2 dBm output power. The final output power can readily be adjusted by changing the biasing in each stage accordingly. The N-way Doherty power amplifier was tested with an 800 MHz bandwidth, 64 QAM test signal aimed for future communication signal standards. An analysis of this configuration has also been performed for 2-way, 3-way and 4-way architectures

Behavioural Models for Distributed Arrays of High Performance Doherty Power Amplifiers

Behavioral models are intended as high level mathematical descriptions which require less computational effort to simulate behavior compared to physical or circuit level equivalent models. When designed and dimensioned properly they are well suited to concise characterization of power amplifiers under different operating conditions. In this paper we compare the relative performance of several behavioral models for modelling an asymmetric Doherty power amplifier for their use in distributed arrays

Phase-Only Digital Predistortion Technique for Class-E Outphasing Power Amplifiers

Efficient and linear power amplifiers (PA) are an essential part of forthcoming 5G wireless systems. Outphasing class-E PAs offer high power efficiency and an option for higher efficiency cellular networks. However, they employ signal component separators, which split the signal into two paths. In order to efficiently recombine the signal, nonlinear power combiners are used. This paper proposes a novel phase-only predistortion technique for outphasing class-E PAs. The predistortion coefficients can be extracted based on AMAM characteristics of the output signal and an analytical model of an outphasing Class E PA. The suggested technique has been validated by simulation of an outphasing power amplifier in ADS Ptolemy software. It is shown that applying this technique to a 16QAM OFDM modulated signal with 20 MHz bandwidth improves error vector magnitude (EVM) from 10.39% to 2.43% compared to the signal without predistortion

Wideband Interleaved Vector Modulators for 5G Wireless Communications

Next generation wireless communication systems such as fifth generation mobile communications and high throughput satellites have promised a step increase in the rate at which digital data can be transmitted. This requires wideband modulators consisting of high speed digital to analogue converters and RF upconverters to generate the wideband signal of interest. In this paper we demonstrate a scheme to generate a wide bandwidth modulated signal by bandwidth interleaving multiple modulators of narrower bandwidths. The proposed scheme is experimentally validated with measured results on an 8PSK signals of symbol rate 80 MSPS with modulation characteristics in accordance with DVB-S2 standard

A Novel Physical Layer Encryption Scheme to Counter Eavesdroppers in Wireless Communications

Modern wireless communication systems employ wideband modulated RF carriers to communicate the data of interest between the nodes in the network. The security of communications has been conventionally addressed in the data link layers through scrambling and data encryption schemes. These schemes however do not secure the air interface parameters such as modulation scheme and leave them susceptible to eavesdropping and interception by man-in-the-middle platforms. Physical layer security schemes such as directional modulation, DFT S OFDM and RF fingerprinting have been proposed. In this paper, we propose a novel physical layer encryption scheme based on the spectral profile of the intended modulated signal through deliberately introduced constellation distortion to conceal the modulation scheme. The scheme uses a dispersive filter in the modulator with unique group delay profiles unknown to the eavesdropper. The appropriate inverse filter is employed in the authorized receivers to recover the original modulated basebands for demodulation

Digitally Assisted Transmitter Enhancement Techniques for Millimeter Wave Radio Systems

Wireless communication has become an integral part of life in a modern society. The data to be transmitted is modulated on radio frequency carrier signals for transmission where the bandwidth of the signal to be transmitted increases proportional to the speed at which the data is intended to be transmitted. The present generation cellular wireless communication systems employ channel bandwidths as wide as 20 MHz in multipole bands between 800 MHz and 3.5 GHz with digitally modulated multi-carrier transmission schemes and hybrid access schemes in time, frequency and spatial domains. The radio spectrum has stretched to occupy multiple bands below to meet the demand for volume and speed of the data to be communicated. Indoor short range wireless communications of present generation employ channel bandwidths as wide as 160 MHz and transmit at powers lesser than a tenth of that transmitted by cellular systems and employ similar access schemes as cellular wireless systems. There has been a similar evolution in the area of wireless communications through satellites. Next generation wireless communication systems such as 5G and High-Throughput-Satellite systems in the millimetre wave bands have promised a step increase in data rates in the order of several gigabits per second operating multiple frequency bands over and above those in use at present. This necessitates design of state of the art mm-wave transceivers capable of operating in millimetre wave bands with instantaneous bandwidths of several hundreds of MHz. The cost and complexity of implementation of the radio transmission system increases rapidly as the bandwidths increase. This work investigates digital enhancement techniques to enhance performance of wideband radio frequency transmitters. A section of the work focusses on characterizing wideband impairments in radio frequency hardware and mitigating them through digital signal processing. Another section devises digital signal processing operations to jointly enhance power efficiency in radio frequency transmitters along with providing an additional tier of security to the information being transmitted.The third section focusses on methods of transmission of wideband modulated signals by seamlessly interleaving multiple radio frequency transceivers of relatively narrow bandwidths in the frequency domain thereby presenting an architecture for scalable bandwidth transmitters. Overall this thesis presents innovative techniques to mitigate limitations in radio frequency hardware that hinder wideband operation and schemes to construct scalable bandwidth transceivers with scope to reuse legacy radio frequency hardware for next generation communication systems in part or whole

Digitally Assisted Transmitter Enhancement Techniques for Millimeter Wave Radio Systems

Wireless communication has become an integral part of life in a modern society. The data to be transmitted is modulated on radio frequency carrier signals for transmission where the bandwidth of the signal to be transmitted increases proportional to the speed at which the data is intended to be transmitted. The present generation cellular wireless communication systems employ channel bandwidths as wide as 20 MHz in multipole bands between 800 MHz and 3.5 GHz with digitally modulated multi-carrier transmission schemes and hybrid access schemes in time, frequency and spatial domains. The radio spectrum has stretched to occupy multiple bands below to meet the demand for volume and speed of the data to be communicated. Indoor short range wireless communications of present generation employ channel bandwidths as wide as 160 MHz and transmit at powers lesser than a tenth of that transmitted by cellular systems and employ similar access schemes as cellular wireless systems. There has been a similar evolution in the area of wireless communications through satellites. Next generation wireless communication systems such as 5G and High-Throughput-Satellite systems in the millimetre wave bands have promised a step increase in data rates in the order of several gigabits per second operating multiple frequency bands over and above those in use at present. This necessitates design of state of the art mm-wave transceivers capable of operating in millimetre wave bands with instantaneous bandwidths of several hundreds of MHz. The cost and complexity of implementation of the radio transmission system increases rapidly as the bandwidths increase. This work investigates digital enhancement techniques to enhance performance of wideband radio frequency transmitters. A section of the work focusses on characterizing wideband impairments in radio frequency hardware and mitigating them through digital signal processing. Another section devises digital signal processing operations to jointly enhance power efficiency in radio frequency transmitters along with providing an additional tier of security to the information being transmitted.The third section focusses on methods of transmission of wideband modulated signals by seamlessly interleaving multiple radio frequency transceivers of relatively narrow bandwidths in the frequency domain thereby presenting an architecture for scalable bandwidth transmitters. Overall this thesis presents innovative techniques to mitigate limitations in radio frequency hardware that hinder wideband operation and schemes to construct scalable bandwidth transceivers with scope to reuse legacy radio frequency hardware for next generation communication systems in part or whole

Digitally Assisted Transmitter Enhancement Techniques for Millimeter Wave Radio Systems

Wireless communication has become an integral part of life in a modern society. The data to be transmitted is modulated on radio frequency carrier signals for transmission where the bandwidth of the signal to be transmitted increases proportional to the speed at which the data is intended to be transmitted. The present generation cellular wireless communication systems employ channel bandwidths as wide as 20 MHz in multipole bands between 800 MHz and 3.5 GHz with digitally modulated multi-carrier transmission schemes and hybrid access schemes in time, frequency and spatial domains. The radio spectrum has stretched to occupy multiple bands below to meet the demand for volume and speed of the data to be communicated. Indoor short range wireless communications of present generation employ channel bandwidths as wide as 160 MHz and transmit at powers lesser than a tenth of that transmitted by cellular systems and employ similar access schemes as cellular wireless systems. There has been a similar evolution in the area of wireless communications through satellites. Next generation wireless communication systems such as 5G and High-Throughput-Satellite systems in the millimetre wave bands have promised a step increase in data rates in the order of several gigabits per second operating multiple frequency bands over and above those in use at present. This necessitates design of state of the art mm-wave transceivers capable of operating in millimetre wave bands with instantaneous bandwidths of several hundreds of MHz. The cost and complexity of implementation of the radio transmission system increases rapidly as the bandwidths increase. This work investigates digital enhancement techniques to enhance performance of wideband radio frequency transmitters. A section of the work focusses on characterizing wideband impairments in radio frequency hardware and mitigating them through digital signal processing. Another section devises digital signal processing operations to jointly enhance power efficiency in radio frequency transmitters along with providing an additional tier of security to the information being transmitted.The third section focusses on methods of transmission of wideband modulated signals by seamlessly interleaving multiple radio frequency transceivers of relatively narrow bandwidths in the frequency domain thereby presenting an architecture for scalable bandwidth transmitters. Overall this thesis presents innovative techniques to mitigate limitations in radio frequency hardware that hinder wideband operation and schemes to construct scalable bandwidth transceivers with scope to reuse legacy radio frequency hardware for next generation communication systems in part or whole

Frequency Interleaved Modulators to Support Channel Bonding in Satellite Communications

Next generation wireless communication systems such as high throughput satellites and fifth generation mobile communications have promised a step increase in the rate at which data can be transmitted. This would ideally require bespoke modulator designs for the ground stations with wide bandwidths employing expensive high throughput data converters. The next generation communications hardware also need to be backward compatible with legacy systems of lower bandwidths till they are rendered obsolete. In this paper we demonstrate a scheme to generate a wide bandwidth modulated baseband signal with multiple modulators of narrower bandwidths in a satellite communications ground station

N-way Digitally Driven Doherty Power Amplifier Design and Analysis for Ku band Applications

With an increasing interest in backwards compatibility for existing satellites and the emerging satellite markets, wireless transceivers at Ku band are increasing in popularity. This paper presents the design of a four-way digitally driven Doherty amplifier, aimed at applications in Ku-band. Single tone measurements indicate a maximum drain efficiency of 53.4% at a maximum of 19.2 dBm output power. The final output power can readily be adjusted by changing the biasing in each stage accordingly. The N-way Doherty power amplifier was tested with an 800 MHz bandwidth, 64 QAM test signal aimed for future communication signal standards. An analysis of this configuration has also been performed for 2-way, 3-way and 4-way architectures