RF

Wireless Local Area Networks (WLANs) are commonly deployed in various environments. The WLAN data packets are not transmitted continuously but often worst-case exposure of WLAN is assessed, assuming 100% activity and leading to huge overestimations. Actual duty cycles of WLAN are thus of importance for time-averaging of exposure when checking compliance with international guidelines on limiting adverse health effects. In this paper, duty cycles of WLAN using Wi-Fi technology are determined for exposure assessment on large scale at 179 locations for different environments and activities (file transfer, video streaming, audio, surfing on the internet, etc.). The median duty cycle equals 1.4% and the 95th percentile is 10.4% (standard deviation SD = 6.4%). Largest duty cycles are observed in urban and industrial environments. For actual applications, the theoretical upper limit for the WLAN duty cycle is 69.8% and 94.7% for maximum and minimum physical data rate, respectively. For lowe...

Frequency oscillator is one of the basic devices that can be used in most electrical, electronics and communications circuits and systems. There are many types of oscillators depending on frequency range used in an application such as audio, radio and microwave. The needed was appeared to use high and very high frequencies to make the rapid development of advanced technology Colpitts oscillator is one of the most common types of oscillator, it can be used for radio frequency (RF), that its output signal is often utilized at the basic of a wireless communication system in most application. In this research, a Colpitts oscillator is comprised from a bipolar junction transistor (BJT) amplifier with LC tank. This design is carrying out with a known Barkhausen criterion for oscillation. Firstly, is carried out using theoretical calculation. The secondary is carried out using simulation (Multisim 13). All the obtained result from the above two approaches are 10 MHz and 9.745 MHz respectively. This result is seen to be very encouraging.

"It's a Microcontroller Based DIY Electronics Project. Named Wireless RF Module Using PIC Microcontroller. The RF module is a small electronic circuit used to transmit, receive, or transceive radio waves on one of a number of carrier frequencies. RF modules are widely used in consumer applications such as garage door openers, wireless alarm systems, industrial remote controls, smart sensor applications, weather monitoring system, RFID, wireless mouse technology and wireless home automation systems. They are often used instead of infrared remote controls as they have the advantage of not requiring line-of-sight operation. Thanxx.
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Low noise amplifier is a crucial and essential component in RF receiver design. It amplifies the received weak RF signal with minimum noise contribution. Designing Low noise amplifier with CMOS technology is one of the important topics in research fields due to its advantages of low power, low cost and higher integration. Applications of LNA include WLAN, WSN and UWB applications. In this paper a detailed survey is provided for various LNA design techniques. The designed circuit is simulated using Advanced Design System (ADS) software.

The Society for Vascular Surgery (SVS) and the American Venous Forum (AVF) have developed clinical practice guidelines for the care of patients with varicose veins of the lower limbs and pelvis. The document also includes recommendations on the management of superficial and perforating vein incompetence in patients with associated, more advanced chronic venous diseases (CVDs), including edema, skin changes, or venous ulcers. Recommendations of the Venous Guideline Committee are based on the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system as strong (GRADE 1) if the benefits clearly outweigh the risks, burden, and costs. The suggestions are weak (GRADE 2) if the benefits are closely balanced with risks and burden. The level of available evidence to support the evaluation or treatment can be of high (A), medium (B), or low or very low (C) quality. The key recommendations of these guidelines are: We recommend that in patients with varicose veins or more...

Vitreous coatings can be used as a means for the corrosion protection of metals and alloys due to their excellent dielectric properties. Their use is of particular interest in the case of highly aggressive media (different pH levels, temperatures up to 600 °C). However, ceramic coatings exposed to aggressive agents and thermal cycles can experience devitrification and spalling problems, with the consequent loss of their protective properties.The present study uses the electrochemical impedance spectroscopy technique to characterize, in a non-destructive way, the appearance of surface defects induced by the effect of temperature and chemical attack on a vitreous enamel deposited on steel. By means of analysis of the impedance diagrams obtained, a relationship is established between the loss of the coating's protective properties and the mechanism by which the corrosion process takes place.

Sensitivity of the receiver is one of the important parameter of communication system. System noise figure contributes more roles in receiver sensitivity. In single channel receiver very low noise device is used at the RF front end section to improve the system noise figure. In this research work multi-channel receiver noise figure is analysed with different configuration. In each configuration theoretical noise figure calculated for multi-channel receiver and it compared with measured results. The theoretical calculation and Simulation in Advanced Design System (ADS) is done. Keywords: Advanced Design System (ADS), Multichannel receiver, Noise Figure (NF), RF, system noise figure, Signal to Noise Ratio (SNR) ________________________________________________________________________________________________________

In advanced communication technology the microstrip filter has an important job in terms of selectivity and elimination of the undesired signals. In microwave and RF frequency applications the design of filter is complex task as lumped components cannot be used in this range of frequency. Microstrip filters are always preferred over the lumped filters at larger frequency for their compact size, lighter weight, lower cost and higher performance. In this paper the design of grooved microstrip patch resonator band-pass filter is presented at mid-band frequency 1.8 GHz for L-Band applications. It also acts as a band-reject filter at center frequency 1.1 GHz, which is innovative concept in microstrip filter design. Band-pass filter has a high attenuation in stop band, small insertion loss of 0.5744 dB and high return loss of 26.52 dB in the pass band whereas Band-reject filter has a low attenuation, high insertion loss of 21.95 dB and low return loss of 0.2432 dB in the stop band. The result is encouraging and fabrication is also very easy.

"This paper describes several radio frequency interference shields that have been developed for integration with high-speed bulk-input turret-test IC handlers. The shields were developed to mitigate interference to noise figure measurements of Low Noise Amplifier components. Two categories of shielded enclosures were evaluated for shielding effectiveness and ease of incorporation into the existing machines and manufacturing processes. The first category enclosed the handler's working area in its entirety, while the second one enclosed the testboard only. Variation in the testboard shield design was required to suit different collet trajectories between handler models. The shielding effectiveness (SE) was measured according to the MIL-STD-285 standard. The different designs exhibited SE in the 16-49 dB range.

Index Terms —  RF shielding, electromagnetic screening, noise figure measurement."

"The main cause of loss in the PIN-Schottky limiter is the diodes’ parasitic capacitances. Techniques to counter the parasitic capacitances include using bare chip, air cavity packaging, diode stacking, mesa construction, isolating the Schottky diode from the signal path and connecting the diodes to a low impedance node. But the aforementioned techniques either sacrifice cost, manufacturability, size, performances or thermal ruggedness. To reduce loss in the PIN-Schottky limiter, we re-configured its parasitics into a low pass ladder network. This paper reports on the new configuration’s changed large signal and transient performances. We observed improved isolation at 0.9 and 2.4 GHz, and a beneficial reduction in the initial energy that slips through the limiter before limiting begins. In conclusion, this configuration simultaneously improves insertion loss, matching, isolation and spike leakage suppression. It has the potential to improve limiting performances in wideband receivers for wireless communication and medical imaging.
Index Terms — Limiter, receiver protection, Schottky assisted PIN limiter, Schottky enhanced PIN limiter, quasi-active limiter."