IFIP IEEE Dubai Conference Pass Band

8/6/2019 IFIP IEEE Dubai Conference Pass Band

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Enhanced Telemetry System using CP-QPSK Band-

Pass Modulation Technique Suitable for Smart Pill

Medical Application

Nidal Fawaz

Institute for Applied Research

Offenburg, Germany

[email protected]

Dirk Jansen

Institute for Applied Research

Offenburg, Germany

[email protected]

Abstract— A new approach of continuous phase QPSK Band-Pass modulation technique is being developed as enhancement to

the QPSK modulation scheme for inductive data transmission

(NFC). The modulation is based on Gaussian filtering of thephase transition from one state to the other rather than

discontinuity in phase shift. The carrier is based on low

frequency 115 KHz suitable for human body energy penetration

due to its large skin-depth and lower inductive power

attenuation. The complete signal processing is done digitally,external coil and capacitor is used for transceiver interface. The

telemetry assists a smart pill swallowed by human being totrigger an actuator for drug delivery, record temperature, orperform diagnostic task inside the body. The smart pill includes

32bit processor, 16 Kbyte memory, temperature sensor,

telemetry unit, and additional external peripheries. The complete

system is designed, embedded in one SoC, and realized on ASICwith chip-area less than 14 mm².

Wireless communication; DSP; ASIC; SOC; RFID

I. INTRODUCTION

Development of electronics in the last decades opened thedoor for sophisticated equipments to be enrolled in therapeuticand diagnostic applications in medical field. Smart, tiny, andmultipurpose equipments are growing rapidly in this domain.

One of these applications is to diagnose the gastrointestinaltract (GI) for different biomedical analysis as sensing fortemperature, pH, intestinal bacterial flora, intraluminal enzymecontent or mucosal biopsies that are concentrated in the smallintestine. Another application could be used to deliver orrelease pharmaceutically active compounds, food stuff, orvaccine to a chosen location in the GI, as an example thedelivery of chemotherapeutic drugs to the colon of patientshaving colon cancer. These applications are assisted bytelemetry communication to handle out control and dataretrieve from inside the body.

Figure 1 shows a concept of telemetry communicationbetween external device and internal electronic pill. Theexternal device works as a master while the electronic pillserves as a slave. This concept is similar to the RFIDcommunication system based on interrogator or reader (master)and the transponder (slave).

Figure 1. Concept of telemetry system from within the the body to the

outisde using near field communication (NFC) interface

Such electronic pills exist since 1960s where Mackayinvented the first radio telemetry capsule with one transistor in1957 [1], and the first successful pH sensor capsule wasachieved in 1972 [2], since then further improvement are goingon to produce more advanced and self controlled systems tocarry out more complicated tasks as drug delivery anddiagnostic operation inside the body. Table 1 lists most of thesecapsules with their specification [1-8].

Communication system in these pills varies from basicHartley oscillator unidirectional transmitter with low carrierfrequency to more advanced transceiver with high carrierfrequency up to 2.4 GHz. The first pills used simple transmitterwith low carrier frequency suffer from primitive and limitedsignal processing while advanced pills used complicatedcircuits with high frequency carrier suffered from higher

attenuation when the transmitted signal propagates inside thebody. This paper presents an optimized solution between usinga low carrier frequency and signal processing for bidirectionaldata transfer from-to the body.



II. ELECTRONIC PILL CONCEPT

A new electronic capsule with bidirectional communication

system is being developed for multi-task application. Thecapsule is designed to be a platform for medical assistant

inside the body. The designed telemetry unit has synchronous

bidirectional communication block using continuous phase

QPSK of 115 KHz low carrier frequency for inductive data

transmission suited for human body energy transfer.

The communication system can assist the electronic pill to

trigger an actuator for drug delivery, to record temperature, or

to measure pH of the body. It consists additionally to a 32bit

processor, memory, and external peripheries [9]. The complete

system is designed to fit small-size mass medical application

with low power consumption, size of 7x25mm, and invasive

for swallow ability. The first version of this capsule is

powered by a small lithium battery and holds for three days

which is the expected stay duration of the capsule inside thebody. Figure 1 shows the electronic pill (ePille®) construction

[10], this paper focuses on the enhanced modulation of the

telemetry unit of this capsule.

Figure 2. ePille® concept of drug delivery

III. COMMUNICATION

Back to the general equation of a sinusoidal carrier which isdefined as follows:

[ ]ccc t f At c ϑ π += 2cos)( (1)

where Ac is the carrier amplitude, f c is the carrier frequency,and θc is the carrier phase. These three parameters identify threedistinct forms of modulation: Amplitude modulation (ASK),

Frequency modulation (FSK), and Phase modulation (PSK).Other modulations are derived from these three schemes.

The instantaneous frequency is defined as the frequencythat is present at a particular instant of time:

[ ])(2

1)( t t w

dt

d t f ci ϑ

π +⋅=

(2)

⋅+=

dt

t d f t f ci

)(

2

1)(

ϑ

π

(3)

and the frequency deviation is:

⋅=−=

dt

t d f t f t f cid

)(

2

1)()(

ϑ

π

(4)

In QPSK modulation, the angle phase is shifted from onevalue to another in a time limit that tends to zero as shown infigure 3 (a).

Figure 3. Comparison between hard shift (a) and smooth shift (b)

These transient shiftings lead to generate a wide spectrumwith high effect side lobes. To decrease these side effect lobesand increase the power within a limited bandwidth a Gaussianfilter is used to smooth this transient shift within a symbolduration as shown in figure 3 (b).

ϕ2ϕ

ϕ1

t

Tsymbol

ϕ

t

ϕ2

ϕ1

(a)

(b)

TABLE I

LIST OF CAPSULES WITH THEIR SPECIFICATIONS

CapsulesFreq.

(MHz)

Size

(mm)Remarks

InteliSite 6.78 35x10 Pulsed release

Telemetric 108 39x11 Radioactive free

Enterion 1.8 32x12 Pulsed release

HF Capsule 4 28x12 Pulsed release

Gastrotarget N.A. N.A. Dummy Unit LocalizerChipRx N.A. N.A. Continues release

Temp. pill 1 35x9 known as NASA pill

SmartPill N.A. N.A. Multi-sensorsBRAVO 433 25x6 Attached to Esophagus

Radio Pill 0.35 22x9 1st radio pill in 1957Heidelberg pH 1.9 18x8

Microcapsule 433 23x10 MEMS Tech.

Tohoku pH N.A. 2x2 In progressIDEAS 38 36x12 Mutli-sensors

PillCam/M2A N.A. 27x11 Pioneer

Norika 2400 23x9 State-of-the-artEndoscope 433/315 30x11

IVP 900/1 23x11 High power transmission



The idea is to increase the carrier frequency and decrease itback to the original value or vice versa within a period of onesymbol, this process leads an increment or decrement of phaseshift and accordingly achieved the desired phase shift value, forexample {±45° or ±135°}.

The deviation of the frequency has a Gaussian distributionas shown in figure 4 with filter order of 13. The effect of thisGaussian filter is on the carrier frequency, it increases tillmaximum frequency value at the middle and then decreases

back to its original value.

Figure 4. Gaussian distribution (a), Filter coefficients (b),

and filter effect on carrier signal (c)

The frequency-time relation is described as follows:

2

2

1

2

)(

−

−

+=

K

T t

ci

symbol

eK f t f

(5)

Equating (3) and (5):

2

2

1

2

)(

2

1

−

−

+=

⋅+

K

T t

cc

symbol

eK f dt

t d f

ϑ

π

(6)

2

2

1

2

)(

2

1

−

−

=

⋅

K

T t

symbol

eK dt

t d ϑ

π

(7)

dt eK t

t K

T t

symbol

⋅⋅= ∫ ∞−

−

−

2

2

1

2

2)( π ϑ

(8)

A closed form of the Gaussian integration function does notexist, math tables or numerical integration techniques must beused to evaluate it.

A definition for that is the Error function erf(x) or Qfunction, they are used to replace the integration form and theyare known as the cumulative distribution function (CDF) forthe Gaussian distribution :

)()()( t erf K t Qt ⋅≅≅ϑ (9)

A closed form for the modulated signal can be described as

[ ])(cos)( t erf K t w At v c⋅+⋅⋅= (10)

The coefficients of the filter are listed in table 2.

A similar behavior could be understood from MSK andGMSK, in fact the GMSK is based on FSK modulation withGaussian filtering while CP-QPSK is based on PSKmodulation where the phase itself is filtered.

Figure 5. Simulation result of the transmitted and received signals

Demodulated

Modulated

(b)

(c)

(a)

Min. Freq.

deviationMax. Freq.

deviation

v(t)

t

b0 b1 b2 b3 b4 b5 b6 b5 b4 b3 b2 b1 b0

f deviation

t

t

f deviation

Tsymbol

TABLE IIGAUSSIAN FILTER COEFFICIENTS

Coefficients +45 +135

b0 5 0000101 15 000001111

b1 13 0001101 40 000101000

b2 30 0011110 90 001011010

b3 56 0111000 169 010101001

b4 89 1011001 265 100001001

b5 116 1110100 348 101011100

b6 126 1111110 380 101111100



A digital PLL is designed to reconstruct the transmittedsignal from the digital bit stream of the received signal. Thereference frequency of the PLL is 115 kHz with 16bit offsetand 12bit corrector value. The decision circuit integrates thearea under the curve after the PLL output, the value of theintegration is compared to a LUT where the ranges of the fourdifferent symbols are defined. A FIR filter is additionally usedto reconstruct the symbol clock synchronizing the symbol rate.

IV. DESIGN TO LAYOUT PROCESS The complete system is designed using VHDL

programming. The telemetry unit and its signal processing arecompletely coded in digital except the external interface.

An amplifier stage with comparator at the receiver side of 2

ndorder with gain factor of 200 is designed and simulated by

Spice software.

The digital part is simulated using ModelSim software fromMentor Graphics tools. Figure 5 shows a simulation result of the frequency instantiation before transmitted and the receivedsignal after recovery. The signals construct and reconstruct thefilter Gaussian filter behavior, the area under the curverepresents directly the phase angle shift and respectively the

data encoded in the signal.

Figure 6. Layout of the SoC in 0.35µm AMS technology

After Successive emulation of the transmitter and receiver,a complete layout of the chip with its processor and all otherexternal peripheries are routed with 0.35 µ m AMS technology.

Figure 7. “ePille” ASIC Chip with bonding, area less than 14 mm²

After simulation the complete codes are synthesized bysynopsis software to generate the FPGA and ASIC verilognetlist. Cyclone II from Altera is used to emulate the FPGAnetlist of the design, and the ASIC netlist is used for ASIClayout. Digital placement was done by Encounter softwarefrom Cadence and analog placement was done by IC stationfrom Mentor graphics. The complete layout is shown in figure6, the telemetry unit with its digital and analog amplifier has acoverage area of 1 mm².

Figure 7 shows the complete ASIC chip of “ePille”, thechip has an area of 14 mm².

V. RESULTS

DUT showed successful running chip with goodperformance. The chip consumes 3 mW during transmittingand receiving at a distance of 20 cm, while 5µW during sleepmode. The spectrum showed attenuated side lobes of 20 dBwith respect to a normal QPSK as seen in Figure 8 withimproved power efficiency of 10 %.

Figure 8. Spectrum of QPSK (a) and CP-QPSK (b)

(a) QPSK Signal Spectrum

(b)

(b) CP-QPSK Signal Spectrum

RAM RAM

Telemetry Processor Analog



VI. CONCLUSION

A complete telemetry unit based on CP-QPSK Band-PassModulation is designed, simulated, emulated and layout.Enhancement in modulation technique led to a better spectrumand higher performance with respect to QPSK. Additionalwork is needed to be done for final acquisition andperformance.

REFERENCES

[1] Mackay, “Endoradiosonde” Nature, vol. 179, 1957.

[2] Meldrom, “pH profile pf gut as measured by radio telemetry capsule”Br. Med. Vol. 2, pp. 104, 1972.

[3] Wilding, Hirst, “Development of a new engineering-based capsule forhuman drug absorptions studies” PSTT vol 3, 2000.

[4] Houzego, Patent WO 01/45552 A1, 2001.

[5] www.chiprx.com

[6] G. Iddan, “Wireless Capsule Endoscopy”, Nature,vol 405, 2000.

[7] www.rfnorika.com

[8] http://ivp.ims-chips.de

[9] D. Jansen, N. Fawaz, D. Bau, M. Durrenberger: “A Small HighPerformance Microprocessor Core SIRIUS For Embedded Low PowerDesigns, Demonstrated in a Medical Mass Application Of an ElectronicPill (ePille®)”, Embedded System Design Topic, Techniques andTrends, Springer p. 363-372, 2007.

[10] N. Fawaz, D. Jansen: “A SoC Electronic Pill (ePille®) with 32bitSIRIUS Processor and Bidrectioanl Communicaiton System used forBiomedical Telemetry Applications”, International Conference onInformation & Communucaiton Technologies from Theroy toApplications – ICTTA’08, IEEE Communication Society, p. 63-64,April 2008.

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