**Communication Strategies for Various Types of Swallowable Telemetry Capsules**

Jin-Ho Cho and Sang Hyo Woo

*School of Electrical Engineering and Computer Science, Kyungbook National University, South Korea* 

#### **1. Introduction**

40 Modern Telemetry

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In this chapter, introducing some of the ideas, potentialities, and limitations of swalowable telemetry capsule systems. The telemetry systems were widely used for animal research while the subject can do its regular activities [1-9]. Therefore, it is an ideal method to collect the data of migration path and environmental data. In order to collect the data, the telemetry system has to be attached or implanted to the subjects and transmits the signal throughout the antenna. For the human patients, most of physiological signal from outside of the body did not need telemetry systems, because the signal was easily distorted when the patients were moving. Therefore, the telemetry systems are used when the device is implant into the patients and then collect the data. Since the implantation of the device is extremely difficult work, using the telemetry system is limited for scientific researches and a commercial medical telemetry device was not advent.

Since the implantable telemetry systems is limited by the regulations and safety issue, the scientists look forward to develop a disposable capsule that resemble a medical pill and automatically measure the various philological data after swallow it. There are many frontier researches about the telemetry capsules. Some of the capsule measured the intraluminal pressure from inside of the gastro intestine while the capsule goes naturally flow toward to aboral direction [10-14]. Since the physician gets the intraluminal data, it was hard to assume a location of the capsule such as the capsule is in the middle of a duodenum or jejunum?

Another capsule can measure pH signals from the gastro intestine. This capsule provides the meaningful data to diagnosis many diseases such as the gastroesophageal reflux. These capsules also measure the pH signal while it is naturally flow and does not provide location information. While most of the capsules was measuring the signal when the capsule was naturally flow toward to aboral direction, a bravo capsule can stop at the esophagus and measuring the pH difference [15-19]. Other capsules measures the core temperature [20, 21], which is a bit higher than skin temperature.

Unlike above applications, a capsule endoscopy is a revolutionary product that captures inside of the gastro images and transmits it throughout the RF transmitter [22-26]. In order to get clear images, the data rate of the RF transmitter has to be sufficiently high while the power consumption is still low that could be active by small coin batteries. The frontier of this field is Given Image company products and it could monitor not only the small intestine but also the esophagus and colon.

Communication Strategies for Various Types of Swallowable Telemetry Capsules 43

Fig. 3 depicts common analog modulation methods that is known as amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM). The latter two types of modulation are similar, and belong to the class of modulation known as the angle

The AM is characterized by the fact that amplitude of carrier signal is varied in proportion to the baseband signal. In the fig. 3 (c) depicts modulated AM signal and it could be easily see the amplitude of the signal is varying with the baseband signal. The FM conveys information over a carrier wave by varying its instantaneous frequency. In the fig. 3 (d) depicts the frequency of the carrier signal is changed from the baseband signal. The PM is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave. In the fig. 3 (e) depicts that the phase of the signal is varying with the

With using analog modulation system, the super heterodyne system is widely used due to its simplicity, cheap, and high performance. Fig. 4 depicts the super heterodyne system that uses frequency mixing or heterodyning to convert a received signal to a fixed intermediate frequency (IF). With using the IF, it is easily tuning the channel and can reduce performance

modulation.

baseband signal.

Fig. 3. Simple example of the modulated signal.

of the band filters.

Due to success of the capsule endoscopy, there are many trails to develop the capsule that has surgical operation, medical treatment, and locomotion abilities [27-33]. Most of researches are focused to give locomotion ability by using a magnet, actuator, and electrical stimuli. The aim of locomotion research is to observe a suspicious area because the capsule is naturally goes down to the aboral direction. Other researches do increasing friction to stop the capsule at the suspicious area [34, 35]. Also, there are many interesting capsules are developing such as a bleeding detection [36], assembling capsule[37], and biopsy [37].

From above description, application of the swallowable telemetry capsule is abundant and it is rapidly cutting its edges. In order to transmit the physiological data or control the capsule, a telemetry system is essential part for stable module. In this chapter, a basic telemetry methods are describe in 2.1 to 2.2 and describe important points for swallowable capsule in the 2.6. Therefore, the reader who is familiar of a communication technique should skip the 2.1~2.5 and read the 2.6 directly.
