A generalized circuit architecture for RF-photonic frequency multiplication with minimum RF energy

A photonic frequency octo-tupler with reduced RF drive power and extended spurious sideband suppression

In this work, we propose a new scheme of generating high quality frequency quadrupling signal for millimeter-wave wireless communication system. The frequency quadrupling scheme is achieved by using three parallel Mach-Zehnder modulators (MZMs) and an optical phase shifter. The first two MZMs are driven by the RF signals to operate at the maximum transmission point. The third MZM is operated with no RF signal and an extra π-phase difference is introduced for it by the optical phase shifter. The advantage of the proposed scheme is that the optical carrier and the fourth optical sideband can be suppressed simultaneously. The performance of proposed scheme is investigated theoretically and evaluated by simulations. Numerical results show that the radio frequency spurious suppression ratio (RFSSR) higher than 44.18 dB and the optical sideband suppression ratio (OSSR) higher than 21 dB can be obtained without optical filter when the extinction ratio (ER) of the MZM is 30 dB. The impact of the non-ideal RF driven voltage and phase difference of RF driven signal applied to the first two sub-MZMs on OSSR and RFSSR is also discussed and analyzed.

This paper proposes a 32‐tupling frequency millimeter‐wave (MMW) filter‐free system based on four Mach‐Zehnder Modulators (MZM) connected in parallel and cascaded with a simple radio‐fiber (RoF) link structure. The four MZMs are all at the maximum transmission point (MATP), and the radio frequency (RF) driving voltage phase difference between MZMs is π /2. The center carrier is suppressed by using an optical attenuator (OATT) and an optical phase shifter (OPS). Two parallel MZMs can generate ±8th order and ±12th order optical sidebands, and the ±4th order optical sidebands can be suppressed by adjusting the modulation index m of the MZM, using cascaded two dual‐parallel MZMS(DPMZM) and the phase difference of the RF signal source is π/4 to generate ±16th order optical sidebands. The theoretical analysis and simulation experiments are performed for the scheme proposed in this paper. The results show that the simulated and theoretical values of the optical sideband suppression ratio (OSSR) for ±16th order optical sideband signals are 60.02 and 59.96 dB, respectively, and the simulated and theoretical values of the RF sideband suppression ratio (RFSSR) for the 32‐tupling MMW signal are 56.34 and 53.94 dB, respectively.

Mach-Zehnder (MZ) modulators are widely used in optical transmitters to generate high-speed optical signals. With electronic dispersion compensation (EDC), the driving signals to MZ modulators change from digital to analog, or continuous waveforms. Consequently, there is signal degradation from their sinusoidal transfer curves. In this paper, we theoretically and numerically investigate the signal degradation in optical transmitters using MZ modulators in the presence of EDC. We show that the temporal waveforms follow the Gaussian distribution when the EDC is large, and therefore, the modulation index needs to be optimized between the output SNR and the excess insertion loss of MZ modulators. With varying modulation index, we quantify the output SNR and excess insertion loss of optical IQ modulators that consist of two parallel MZ modulators. The calculations are also extended to the scenarios where the sinusoidal transfer curves are compensated for. All the analytical results are verified in a simulation of QPSK transmissions, and they are useful for finding an optimized modulation index for a tradeoff between the output SNR and excess insertion loss.

Radio frequency (RF) energy transfer and harvesting techniques have recently become alternative methods to power the next generation wireless networks. The RF energy harvesting system was designed to convert the RF energy available in the atmosphere into useful electrical energy which can be used to charge a battery of capacity 50 uAh. This battery requires a voltage in the range of 4- 4.2V to get itself charged. In this paper we have designed and simulated a Radio Frequency (RF) energy harvesting circuit which utilized available RF energy with the voltage boosting circuit. Simulation results represents that by using matching network of high-Q, output voltage of harvesting circuit increases and it becomes more sensitive with respect to input signal frequency and value of elements used.

A flexible and ultra-flat optical frequency comb generator using a parallel Mach–Zehnder modulator with a single DC bias

Past work on radio frequency (RF) energy harvester design mostly focused on harvesting RF energy in a single RF band [1, 2,]. While a significant portion of RF energy is concentrated in the communication band around 900 MHz, there is also abundant RF energy present in the band covering 1800 MHz to 2100 MHz. For example. Li [2011] demonstrated the design and implementation of a dual band RF energy harvester chip that has two cascade voltage multipliers in parallel and can operate at 900 and 1900 MHz bands. The chip can generate 1.2 V output DC voltage at 900 MHz for −19 dBm RF input power and 1.05 V output voltage at 2000 MHz for −18 dBm RF input power. The RF energy conversion efficiency is ∼12% at 900MHz and ∼8% at 2000MHz which is comparable with its single band counterparts at both frequencies in the literature. The design greatly increases the energy harvesting efficiency over two bands. It is found that the input impedance of the chip is ∼ 50 ohm at 900 MHz, 26 ohm at 1.9 GHz, and 70+j10 ohm at 2 GHz. To operate the harvester chip in two bands, the antenna is required to be matched to the chip impedance at 900 MHz for one band and at either 1.9 GHz or 2GHz for the other band.

In directional energy transmissions, a radio frequency (RF) energy source needs to monitor each sector to achieve higher RF energy transmission efficiency. However, since the distribution of harvesting nodes can be dynamically changed in mobile environments, it is difficult to obtain the exact numbers of harvesting nodes in all sectors within limited time. In such a situation, the operations of RF energy sources (i.e., monitoring the number of harvesting nodes and transmitting the RF energy) can be modeled by a partially observable Markov decision process (POMDP), which has high complexity to be solved. As a practical solution, in this paper, we propose an observation-based directional energy transmission algorithm (OB-DETA) that estimates the population in sectors and transmits the RF energy to the selected sector with a sufficient number of harvesting nodes. Evaluation results are given to demonstrate the effectiveness of OB-DETA over the comparison schemes in terms of the RF energy transmission efficiency.

The Mach-Zehnder modulator (MZM) has been widely used for broadband photonic analog links and high-speed digital optical fiber communication systems because it possesses large modulation bandwidth, low driving voltage, and low chirp. The MZM is a very important optical modulator for photonic applications. In an MZM, the input light is split into two paths, each of which is modulated by an electrical signal. Then the two arms are combined to generate an intensity-modulated light or a phase-modulated light at the output of the MZM. An MZM can be made of lithium niobate (LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ), gallium arsenide (GaAs), or indium phosphide (InP), materials that exhibit some anisotropy in their dielectric properties. Theoretically, the relation of output optical field and driving voltage is a cosine function, i.e., nonlinear transfer function. For RF photonics, the MZM has typically two applications: optical harmonic generation for optical frequency multiplication and optical subcarrier modulation for optical signal modulation. For optical frequency multiplication, high transfer-function nonlinearity is preferred. In contrast, high transfer-function linearity is preferred for optical subcarrier modulation. It is well known that a cosine transfer function can present high or low nonlinearity dependent on operation voltage. Specifically, bias voltages determine the degree of nonlinearity or linearity of the MZM transfer function. For optical frequency multiplication such as millimeter-wave generation, the MZM should be biased at some specific bias points, such as minimum transmission, maximum transmission, and quadrature bias points, to enhance nonlinearity [1]?[2]. For optical subcarrier modulation, biasing an MZM in its linear region such as quadrature bias points allows transmitting broadband RF signals with multioctave bandwidth and improves spurious free dynamic range (SFDR). Therefore, care must be taken to maintain and control the MZM bias point for a specific application.

Preferential properties with decremental conduction of the Marshall vein between the coronary sinus and left superior pulmonary vein

In this paper, we propose a new approach to generate quadrupling-frequency optical millimeter-wave (mm-wave) signal with carrier suppression by using two parallel Mach-Zehnder modulators (MZMs) in Radio-over-flber (RoF) system. Among the numerous properties of this approach, the most important is that a fllterless optical mm-wave at 60GHz with an optical sideband suppression ratio (OSSR) as high as 40dB can be obtained when the extinction ratio of the MZM is 25dB. Simplicity and cost-efiectiveness have made this approach a compelling candidate for future wave-division-multiplexing RoF systems. Theoretical analysis is conducted to suppress the undesired optical sidebands for the high-quality generation of frequency quadrupling mm-wave signal. The simulation results show that a 60GHz mm-wave is generated from a 15GHz radio frequency (RF) oscillator with an OSSR as high as 40dB and an radio frequency spurious suppression ratio (RFSSR) exceeding 35dB without any optical or electrical fllter when the extinction ratio of the MZM is 25dB. Furthermore, the efiect of the non-ideal RF-driven voltage as well as the phase difierence of RF-driven signals applied to the two MZMs on OSSR and RFSSR is discussed and analyzed. Finally, we

The purpose of this study was to test whether radiofrequency (RF) energy could be used to fixate leads to the endocardium. In six dogs we measured the dislodgment force and pacing threshold before and after RF fixation in the coronary sinus (CS) and right ventricle (RV). RF fixation was achieved with a CardioRhythm Atakr ablation unit. The dislodgment force of CS leads fixed with RF energy was 1.63+/-0.65 oz, compared with < 0.1 oz for similar leads placed in the CS of six separate dogs. In the RV, leads fixed with RF energy had a dislodgment force of 1.29+/-0.27 oz, compared with 0.48+/-0.28 oz. for urethane (P < 0.01) and 1.01+/-0.21 oz for silicone (P = 0.41) tined leads. In the CS, the pacing threshold for RF fixed leads increased significantly from 2.2+/-1.1 V (0.5 msec) before fixation to 4.2+/-1.3 V after fixation (P < 0.01), while in the RV, the pacing threshold increased from 0.41+/-0.05 V (0.5 msec) before fixation to a mean of 2.03+/-0.44 V after fixation (P < 0.01). In another group of six dogs studied for 12 weeks, 5 of 6 RF fixed CS leads remained attached, as did 8 of 10 RF fixed RV leads. For the RV leads, the mean pacing threshold was 0.90+/-0.35 V, compared with 0.53+/-0.18 V (0.5 msec) for similar tined leads (P = 0.02) and 1.2+/-0.30 V (0.5 msec) for screw leads (P = 0.18) in the RV. We conclude that RF energy can be used to attach leads to the RV and CS endocardium. While the RV pacing thresholds increased acutely, the mean chronic thresholds were not significantly different for RF fixed leads and standard tined or screw leads.

A phase-coded microwave signal generation method based on parallel Mach-Zehnder modulator (MZM) with tunable frequency multiplication factor is proposed and demonstrated. By controlling the modulation index and the optical power ratio of the parallel MZMs, phase-coded microwave signals with frequency multiplication factors of 1, 3 and 5 are obtained. The feasibility of this approach is demonstrated by theoretical analysis and simulation, in which binary phase-coded signals with carrier frequency of 1GHz, 3GHz or 5GHz are respectively generated under 1GHz radio frequency (RF) signal input.

One of key performances in radio frequency (RF) energy harvesting application is how to efficiently capture the ambient RF energy to be rectified for energizing small electronic appliances. In this paper, a rectenna equipped with pump-charge and DC-DC converter is proposed for 1.8GHz RF energy harvesting application. The selection of Global System for Mobile communications (GSM) frequency at 1.8GHz is based on the frequent use of these frequencies for communication so that it has potential to receive a lot of RF energy. The proposed rectenna is developed using 2$\times$2 circular waveguide array antenna, while the pump-charge and DC-DC converter circuits are implemented to gain high enough direct current (DC) output voltage from the captured RF signal. The experimental characterization result shows that the RF signal output of circular waveguide array antenna in the range of -10dBm to 1dBm has been successfully rectified to obtain the DC output voltage of 0–2V and 0–3V for pump-charge and DC-DC converter, respectively.

This paper proposes a MAC protocol for Radio Frequency (RF) energy harvesting in Wireless Sensor Networks (WSN). In the conventional RF energy harvesting methods, an Energy Transmitter (ET) operates in a passive manner. An ET transmits RF energy signals only when a sensor with depleted energy sends a Request-for-Energy (RFE) message. Unlike the conventional methods, an ET in the proposed scheme can actively send RF energy signals without RFE messages. An ET determines the active energy signal transmission according to the consequence of the passive energy harvesting procedures. To transmit RF energy signals without request from sensors, the ET participates in a contention-based channel access procedure. Once the ET successfully acquires the channel, it sends RF energy signals on the acquired channel during Short Charging Time (SCT). The proposed scheme determines the length of SCT to minimize the interruption of data communication. We compare the performance of the proposed protocol with RF-MAC protocol by simulation. The simulation results show that the proposed protocol can increase the energy harvesting rate by 150% with 8% loss of network throughput compared to RF-MAC. In addition, the proposed protocol can increase the lifetime of WSN because of the active energy signal transmission method.