Abstract: In today’s modern era, mobile phones have become a basic need for people all over the world. The charging of mobile phone has become an arduous task. It is a hectic task to carry everywhere the charger of mobile phones or any electronic gadget while travelling or it is very cruel when your mobile phone getting off by the time you urgently need it. It is the major problem in today’s electronic gadgets. Though the world is leading with the developments in technology, but this technology is still incomplete because of certain limitations. Today’s world requires the complete technology and this purpose is solved using a technique called ‘Wireless Charging of Mobile Phones Using Microwaves’.
The technique mentioned has two basic concepts. They are:-
When white light is shone through a prism it is separated out into all the colors of the rainbow this is called the visible spectrum. According to some physicians light consists of tiny particles called photons. Photons are bundle of energy. The speed of light is about 300,000,000 meters per second as light hit something that means it may be bounce off, go right through or get absorbed. If they bounce off something and then go into your eye you will see the thing they have bounced off. This is the cause of vision.
Microwaves are a form of electromagnetic radiation with wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz (0.3 GHz) and 300 GHz. Microwave technology is extensively used for point-to-point telecommunications (i.e., non broadcast uses).
Microwaves are especially suitable for this use since they are more easily focused into narrower beams than radio waves, allowing frequency reuse; their comparatively higher frequencies allow broad bandwidth and high data transmission rates, and antenna sizes are smaller than at lower frequencies because antenna size is inversely proportional to transmitted frequency. At high frequencies, atmosphere is less transparent to microwaves. Microwaves are used in applications where information has to travel long distances between ground stations and communications satellites. Microwaves are also employed in microwave ovens and radar technology.
The frequency selection is another important aspect in GHz ISM band for the purpose of concern. As Indus-trial, Scientific and Medical (ISM) some bands are reserve for some specific purpose. So we can’t use it. Here S band 2.45 GHz is freely available band which can be used for experiment
WIRELESS POWER TRANSMISSION
Wireless power transmission works on the principle of Magnetic induction. As we put one coil carrying current through it, it creates a magnetic field near to it. And if we put other coil over there than it is induce by the first coil and it carry current from it. This is the principle of magnetic induction.
WIRELESS POWER TRANSMITTING SYSTEM:
This system gives the validity of principle of magnetic induction in wireless communication. The basic components of a wireless transmitting system are:- Transmitter: It consists of microwave generator and transmitting antenna(preferably, slotted waveguide antenna) Receiver: It consists of a receiving antenna and a receiver. A receiver is major part in wireless mobile charging.
The system designing of wireless charging of mobile phone using microwaves mainly consist of four parts as
The Process of Rectification
It mainly consists of a magnetron which is a diode vacuum tube with cathode filament. Magnetron is actually behaved as an oscillator to produce microwaves. It can be done by putting magnet between the resonating chambers which is the center of the oscillator. These resonating chambers are named as anode in the magnetron.
When electrons come out from the cathode and go direct towards the Anode, it passes through the magnetic field. It starts circulating in the resonating cavity and start producing waves according to its frequency. And the generated RF signal by this flow outside of the chamber.
The basic addition to the mobile phone is going to be type of antenna that is used to directly convert microwave energy into DC electricity. This is done by a component known as Rectenna. Actually the size of Rectenna can be reducing using the Nano technology.
The elements of Rectenna are usually arranged in antennae. The current included by the microwaves in the antenna is rectified by the diode which powers a load connected across the diode. Scotty diodes are used because they have low voltage drop and high speed so that they have low power loss. Rectenna are highly efficient at converting microwave energy above 90% have been observed with regularity A sensor must be added at the receiver side. Since the phone must be charged while a person is talking. So here sensor is used to detect wither the phone is using microwaves or not.
PROCESS OF RECTIFICATION:-
Microwave can easily travel through the media but it also loses some energy. So our key objective is to rectify the circuit and to rectify the waves at the low cost. And also we have to make the detection more sensitive. As we know that bridge rectification is more efficient than the single diode we use this for the better performance. We use the schottky diode to get the better impedance. The Schottky barrier diode is an ideal diode, such as for a 1 ampere limited current PN interface. Another advantage of the Schottky barrier diode is a very low noise index that is very important for a communication receiver; its working scope may reach20GHz
The sensor circuitry is a any message signal. This is very important as the phone has to be charged as long as the user is talking. . Thus a simple frequency to voltage converter would serve our purpose. And this converter would act as switches to trigger the rectenna circuit to on. So when our phone is receiving microwave signal it make the rectenna circuit on and charge the battery. Here in India the operating frequency of the GSM is 900 MHz to 1800 MHz. We can use LM2907 for F to V conversion.
It can be concluded from this technique, this usage of mobile phones is made simpler and leads to elimination of the need for separate chargers for mobile phones making charging universal. This improvisation in mobile phones allows the mobile phone users to carry their phones anywhere even if the place is devoid of facilities for charging. Thus the tagline the more you talk, the more your mobile phone is charged is perfectly implemented. With this proposal the manufacturers would be able to remove the talk time and battery standby from their phone specifications. A novel use of the rectenna and a sensor in a mobile phone could provide a new dimension in the revelation of mobile phone.