This letter addresses the problem of finding a tractable expression for the symbol error outage (SEO) in flat Nakagami-m fading and shadowing channels. We deal with M-ary phase shift keying (M-PSK) and quadrature amplitude modulation (M-QAM) which extends our previous results on BPSK signaling. We propose a new tight approximation of the symbol error probability (SEP) holding for M-PSK and M-QAM signals which is accurate over all signal to noise ratios (SNRs) of interest. We derive a new generic expression for the inverse SEP which facilitates the derivation of a tight approximation of the SEO in a lognormal shadowing environment.

Harvesting radio frequency (RF) energy is an attractive solution for powering ultralow-power (ULP) devices. However, harvesting efficiently from different RF power levels is still a challenge. This work presents a wide power range RF harvester composed of a rectifier circuit and a power management integrated circuit (PMIC). Such a wide range is achieved by associating two independent rectifiers in parallel, one specifically optimized for low RF powers. In the association, the inductive matching technique is employed in each rectifier. It consists of an inductive branch comprised of a lumped inductor and a short-circuited stub whose values are selected to minimize ohmic losses. The operation range is controlled via the inductive branch values and by following the optimal load of the rectifier circuit with the PMIC, based on the input power level. The harvester is designed at $889~\text{MHz}$ and manufactured by using off-the-shelf components. Measured efficiencies of $29\%$ and $63\%$ are obtained at $-20$ and $0~\text{dBm}$ , respectively, demonstrating the wide power range with high efficiency at low powers. At $-20~\text{dBm}$ , the rectifier association keeps the PMIC active and delivers hundreds of nW at a regulated voltage of $1.8~\text{V}$ , which is suitable for ULP devices.

In the context of the UHF (Ultra High Frequency) passive RFID (Radio Frequency Identification) technology, recent works have proposed a new paradigm demonstrating the possibility to perform short distance tag to tag (T2T) communications. This paper presents a study that focuses on the performance evaluation of T2T systems. Without loss of generality as to the methodology followed, dipole antennas are considered here (assumed ideal in the theoretical part, then printed for the rest of the study). The results obtained show that the modulation depth, which can be considered as an evaluation metric for the T2T systems, is strongly impacted by three main parameters: the switching impedances (here chosen as short-circuit and open-circuit); the geometrical configuration constituted by the two tag antennas forming the T2T system; and also, the position of the external source on which the backscatter communication relies. As the modulation depth is very sensitive to these three parameters, which are more or less directly related, it is very difficult to predict the communication quality for a given configuration. For example, when the two tags are in parallel and the source is symmetrically positioned, the modulation depth shows a decreasing trend by oscillating when the distance between the tags increases from $0.1~\lambda $ to $1~\lambda $ ( $\lambda $ being the wavelength): with values going from 70% to less than 5%. As a consequence, from a very complete set of scenarios considered, the presented study helps to illustrate and explain the interactions of these parameters and their impact on the modulation depth. And at the same time, the paper provides guidelines for defining the specifications of such a system based on quantified results. The set is completed by introducing the BER (Bit Error Rate) as an evaluation metric by considering then a more complete T2T system (for instance listener tag including a non-coherent envelope detector).

With the increasing demand of wireless applications, current radio transceivers are challenged by the requirement of high data rate and high flexibility. Full-Duplex Dual-Band OFDM radio transceiver is a very promising radio technique to approach this goal. However, the mutual undesirable signal leakages due to the I/Q imbalance in the Full-Duplex Dual-Band RF front-end lead to a significant performance degradation in the radio link. In this paper, a practical and suitable digital I/Q imbalance estimation and compensation method for mitigating the I/Q imbalance in this flexible radio transceivers is developed and evaluated. The developed I/Q imbalance estimation method is based on the character of the frequency-flat-fading of the self-interference channel. The ADS-Matlab co-simulation results show that the developed digital compensation method can significantly reduce the impact of the I/Q imbalance on the Full-Duplex Dual-Band OFDM radio receivers.

We propose a modification of the multi-resolution frequency domain ParFlow (MR-FDPF) method that allows simulating radio propagation channels in a frequency range. The performance of the proposed MR-FDPF implementation has been analyzed based on different realistic propagation scenarios. We also analyze the possibility of applying the multi-resolution frequency domain approach to the well-known transmission-line matrix method. The proposed multi-resolution frequency domain transmission-line matrix method provides a computationally efficient way of modeling radio wave propagation in three-dimensional space at multiple frequencies.