Modern wireless communication equipment such as outphasing power amplifiers or systems like massive-MIMO rely heavily on transmission of complex wideband modulated radio frequency signals on parallel signal paths. As these signal bandwidths increase, wireless transmitters are more susceptible to amplitude and phase distortions across frequency. We propose a novel method to quantify the complex signal distortions in each transmit path and a technique to pre-compensate the transmitter over a wide bandwidth of interest. This work has been experimentally validated with measured results on two separate RF test benches using signal bandwidths up to 100 MHz. An outphasing power amplifier bench for WCDMA at S band requiring 4 signal paths and a satellite uplink modulator using 8-PSK at Ku band requiring two signal paths were tested in the experimental validation. Further, it is also validated that this method requires only one iteration to calibrate a set of parallel RF signal paths.
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.
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.
This paper presents the design of a Class AB power amplifier operating at a frequency band of 3.4 GHz-3.7 GHz for LTE base station applications. The proposed design is targeted for a compact, low cost, high efficiency, and good linearity features. It based on GaN HEMT CGH40006P device manufactured by Wolfspeed/Cree. The design procedure and assessment of the presented power amplifier are described in this paper. The proposed input and output matching networks with stepped tapered microstrip transmission line have enhanced the transmission coefficients of the power amplifier, resulting in improvement of overall performance. The drain voltage and current waveforms are demonstrated to ensure the appropriate biasing point of class AB. At 1dB compression, the simulated results of the proposed class AB power amplifier with one tone input signal delivers power added efficiency of 59%, and 38 dBm output power. With code division multiple access (CDMA) signal, the power amplifier delivers a 51.9% of PAE, adjacent channel power ratio (ACPR) of below than-28.5 dBc at 2.25 MHz offsets, and delivers 37 dBm (~5 W) output power.
Massive-MIMO and beamforming techniques have long been proposed as a means of increasing cellular network capacity and improving signal to interference ratio performance. The implementation of such systems requires a large number of signal transmission paths. To realize this, a distributed array of power amplifiers (PAs) is likely to be needed. These PAs will possess similar, but unique, characteristics which will alter over time independently due to temperature drift and component ageing. In order to operate all PAs in both a linear and efficient fashion a linearisation technique, such as Digital Pre-Distortion (DPD), must be used. DPD algorithms benefit from reconfigurability, low latency and power efficiency, all traits associated with Field Programmable Gate Arrays (FPGAs). This demonstration shows how an FPGA, specifically a ZYNQ System on a Chip (SoC), can be used in tandem with a transceiver board, the FMCOMMS2, to implement a DPD system.
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