Energy detection from VHF to X-band using software defined radio technology

Abstract

The software-defined radio (SDR) is a wireless exchange system that performs analog to digital (ADC) translation directly to the carrier signal instead of shifting the carrier signal down to a baseband signal through analog circuits. The benefit of this is that after digitization various code can be performed to demodulate amplitude, frequency and phase modulated signals. The drawback to this is that higher carrier frequencies require faster ADCs which can be expensive and consume additional power which is the background to the problem statement. Also, in this research, to mitigate the necessity of fast and power-hungry ADCs for direct higher frequency digitization, an alternative front-end receiver architecture was studied. This alternative proposed design will permit the mobile SDR to perceive energy of frequencies greater than a low-priced SDR and suppress the image occurrence. The image occurrence is the unique signal that occurs at the frequency RF±2IF. The consequence of the image occurrence incident to the front-end of the receiver at the precise period as the carrier signal produces the same IF after the down conversion process and can’t be removed by any form of filter. The research was undertaken with a system level approach by evaluating receiver architectures that can translate the carrier signal down to a baseband signal where a new design was proposed that is suitable for the mobile SDR environment and thus can be used in conjunction with SDR technology. The proposed design with the various RF components that constitutes the design were established and the limits of each component were defined. Cadence® Applied Wave Research (AWR®) Visual System Simulator™ (VSS) V16 software suite was used to develop a base model for each RF component after which the conceptualized down converter with its suitable specifications were derived. The simulations presented in this research also demonstrated that the proposed design could observe frequencies and suppress the image occurrence from VHF to X-band. This was attained by increasing the linearity of the RF chain and not using filters. These features fundamentally steered the design to have a reduced circuit footprint and will ultimately consume less power compared to expensive SDR’s using fast sampling ADCs to perceive higher frequencies.