New Radio Transmission Technology Requires No Power at All

All data transmission requires power, because the transmission itself—whether that is radio, visible light, or sound—carries energy. Without a power source, that energy would be “free” and that would violate the second law of thermodynamics. But that energy doesn’t necessarily need to come from the transmitter. In many cases, such as when transmitters need to be small and portable, it is very beneficial to reduce or eliminate their power consumption. Backscatter technology already accomplishes that by moving the power source to the receiver. But a team of engineers from the University of Washington and Stanford University developed a new radio transmission technique that seemingly doesn’t require any power at all.

Radio transmission works by sending electricity through an antenna. The method in which the transmitter encodes data varies, but the simplest technique is to simply switch power on and off like Morse code. Backscatter technology works using power from the receiver. In a conventional backscatter setup, the receiver also contains hardware to transmit a powerful signal of its own. The transmitter collects some of that power and passes it through its antenna to create a radio signal to send back to the receiver. Thus, the transmitter can operate without a direct, physically connected power source. It is, however, still using power—there is no free energy.

This new technology works in a different way, but still adheres to the fundamental laws of thermodynamics. In this case, the only power required at the transmitter is that used to flip the switch (a transistor). If that were a mechanical switch flipped by a human, like a Morse code key, the transmitter wouldn’t need any power at all. The receiver, on the other hand, needs a lot of power. The researchers use a refrigerator as an analogy to describe how it works:

The resolution of this seeming paradox is that the receiver in our system is powered and acts like a refrigerator. The signal-carrying electrons on the receive side are effectively kept cold by the powered amplifier, similar to how a refrigerator keeps its interior cold by continuously pumping heat out. The transmitter consumes almost no power, but the receiver consumes substantial power, up to 2 watts. This is similar to receivers in other ultra-low-power communications systems. Nearly all of the power consumption happens at a base station that does not have constraints on energy use.

The benefits here are similar to what we see with backscatter technology. Because the transmitter consumes very little power (just enough to switch the transistor), it doesn’t need bulky batteries. That makes it ideal for medical implants and other devices that can’t be charged often. The receiver needs a lot of power, but it could be in a base station connected to mains electricity or a large battery. This new technology is less complex than backscatter systems, which could make it more affordable and more practical in some situations.

Moving forward, the engineers intend to focus on improving the range of their new technology and the amount of data it can carry.

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