A −40‐dB EVM 20‐MHz subsampling multistandard receiver architecture with dynamic carrier detection, bandwidth estimation, and EVM optimization

Abstract

SummaryIn this work, a reconfigurable multistandard subsampling receiver with dynamic carrier frequency detection and system‐level EVM optimizations is proposed. Ideal software defined radio (SDR) receivers promise complete flexibility at the expense of high‐performance analog‐to‐digital converters (ADCs) that are challenging to implement in current technologies for low‐power applications. This scenario leads to the research of digital intensive sampling receivers with discrete‐time signal processing (DTSP) implemented in analog domain. This approach makes it feasible to move channel selection filtering and dynamic gain adaptability from analog to digital domain. The proposed receiver employs subsampling down‐conversion along with subband filters to dynamically detect the carrier frequency of the incoming signal, estimate its bandwidth, and identify if the signal is present in one of the target standard bands. This carrier detection provides a unique capability to reconfigure the receiver dynamically. Additionally, in this work, system‐level EVM optimization is proposed considering frequency synthesizer phase noise, IQ mismatch, sampling frequency selection and block‐level gain, noise, and nonlinearity. The RF front end of the proposed receiver is modeled in Verilog‐AMS whereas the digital signal processing is implemented in Simulink‐Matlab. The complete receiver has been verified to detect and process three different bands belonging to three different standards (GSM, UMTS, and WLAN) with the carrier frequency ranging from 0.9 to 2.5 GHz. Test signals with 4‐QAM modulation, maximum bandwidth of 20 MHz, and input‐dynamic range from –109 to –20 dBm is utilized to demonstrate the receiver performance including an EVM of –40 dB.