Wednesday, January 12, 2011


It seems these days that everyone has a cellular phone. Whether yours is for business purposes or personal use, you need an efficient way of charging the battery in the phone. But, like most people, you probably don’t like being tethered to the wall. Imagine a system where your cellular phone battery is always charged. No more worrying about forgetting to charge the battery. Sound Impossible?

It is the focus of this thesis to discuss the first step toward realizing this goal. A system will be presented using existing antenna and charge pump technology to charge a cellular phone battery without wires. In this first step, we will use a standard phone, and incorporate the charging technology into a commercially available base station. The base station will contain an antenna tuned to 915MHz and a charge pump. We will discuss the advantages and disadvantages of such a system, and hopefully pave the way for a system incorporated into the phone for charging without the use of a base station.

Through the years, technology has allowed the cellular phone to shrink not only the size of the ICs, but also the batteries. New combinations of materials have made possible the ability to produce batteries that not only are smaller and last longer, but also can be recharged easily. However, as technology has advanced and made our phones smaller and easier to use, we still have one of the original problems: we must plug the phone into the wall in order to recharge the battery. Most people accept this as something that will never change, so they might as well accept it and carry around either extra batteries with them or a charger. Either way, it’s just something extra to weigh a person down. There has been research done in the area of shrinking the charger in order to make it easier to carry with the phone. One study in particular went on to find the lower limit of charger size [1]. But as small as the charger becomes, it still needs to be plugged in to a wall outlet. How can something be called “wireless” when the object in question is required to be plugged in, even though periodically?

Now, think about this; what if it didn’t have to be that way? Most people don’t realize that there is an abundance of energy all around us at all times. We are being bombarded with energy waves every second of the day. Radio and television towers, satellites orbiting earth, and even the cellular phone antennas are constantly transmitting energy. What if there was a way we could harvest the energy that is being transmitted and use it as a source of power? If it could be possible to gather the energy and store it, we could potentially use it to power other circuits. In the case of the cellular phone, this power could be used to recharge a battery that is constantly being depleted. The potential exists for cellular phones, and even more complicated devices - i.e. pocket organizers, person digital assistants (PDAs), and even notebook computers - to become completely wireless.

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