In December we posted a report titled "Apple Files their Tenth Smart Pen Patent of the Year." In that report we covered Apple's invention of a "Stylus Signal Detection and Demodulation Architecture." Today, Apple builds on that invention by adding a superheterodyne pen stimulus receiver in a new patent application published by the U.S. Patent Office. We noted in a previous report that in order for Apple's future digital pen or stylus to be truly successful, it has to conquer the current latency issues. Apple's latest invention addresses this very issue head on.

Apple's Patent Background

As touch sensing technology continues to improve, touch sensitive devices are increasingly being used to compose and mark-up electronic documents. In particular, styluses have become popular input devices as they emulate the feel of traditional writing instruments.

Most conventional styluses simply include a bulky tip made of a material capable of interacting with the touch sensitive device in a manner resembling a user's finger. As a result, conventional styluses lack the precision and control of traditional writing instruments.

A stylus capable of generating stylus stimulation signals that can be transmitted to the touch sensitive device can improve the precision and control of the stylus. However, a touch sensitive device capable of detecting such a stimulation signal may require additional hardware and consume more power than a conventional touch sensitive device.

Apple Invents

Apple's invention relates specifically to a superheterodyne stylus signal receiver for detecting a stylus stimulation signal from a stylus. The stylus signal receiver can be configured to convert the touch signal into an intermediate frequency signal having a frequency that is less than that of the touch signal.

In some examples, a hardware-implemented I-phase demodulator can be used to convert the touch signal into the intermediate frequency signal. The receiver can be further configured to perform IQ demodulation on the intermediate frequency signal at the intermediate frequency signal's lower frequency. In some examples, the IQ demodulation can be performed in firmware.

Apple's patent FIG. 6 noted below illustrates an exemplary process for demodulating a touch signal from a touch sensor.

Apple's patent FIG. 3 illustrates a block diagram of an exemplary control system for a touch sensor that can detect both a user's touch and signals from a stylus.

Apple's patent FIG. 5 noted below illustrates a functional block diagram of a superheterodyne signal receiver.

Patent Credits

Apple credits Shahrooz Shahparnia as the sole inventor of patent application 20150029136 which was originally filed in Q4 2013. Considering that this is a patent application, the timing of such a product to market is unknown at this time.

This is a highly technical invention that only engineers could love. However, if you want to dig into the details of Apple's stylus invention, click here.

We posted a report earlier this month titled "A New Apple Pen Rumor Surfaces as an Accessory for iPad Pro." Will we see Apple introduce an advanced digital pen or stylus later this year? Only time will tell.

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