Small electronic devices attached to the outer surface of standard capsule can potentially serve as a cost-effective method of validating medication compliance via electronic detection of an ingested e-pill inside the human digestive tract.In this paper

a passive chip design for such a device is discussed

and the detailed design procedure is given.For the volume-constrained device to achieve the best communication efficiency in the human body environment

an novel asymmetric architecture

which employs different carrier frequencies on Downlink / U plink data transfer

is proposed:the data communication from the reader to the ingested device (Downlink) is d

esigned at 13.56MHz to minimize the signal attenuation through the human body

and the 915MHz band is used for the communication from the ingested device to the reader (Uplink) to achieve the best antenna radiation efficiency.A prototype micro-chip is fabricated using UMC CMOS 130nm technology

and measures 1500×800μm

2

.Experimental results demonstrate that the chip can be activated by -4dBm input power and achieves a data rate of 17kb/s in the Downlink communication.For the Uplink communication

the chip generates periodic pulses at 915MHz with a data rate of 0.75kb/s.