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In recent years, features extracted from bowel sound (BS) has been proposed in the evaluation and monitoring of gastrointestinal motility. BS has been acquired using sensors such as electronic stethoscopes which require body contact with a subject. However, to our knowledge, the analysis of BS using non-contact microphones has not been reported yet. In this study, we compared BS acquired from a non-contact microphone with those of a stethoscope, while subjects undergo the soda tolerance test (STT). The STT stimulates bowel motility. Our investigation shows that irrespective of the body mass index, both stethoscope-based and non-contact microphone-based BSs have a similar performance in computing features such as: BS detected per minute and sound to sound interval in the time domain. These findings provide a powerful new window into the non-contact evaluation of bowel motility.

Approximately 10%-20% of adults and adolescents suffer from irritable bowel syndrome (IBS) worldwide. IBS is characterized by chronic gastrointestinal dysfunction which may reflect in altered motility. Currently, the diagnosis of IBS is made through expensive invasive radiographic and endoscopic examinations. However these are inconvenient and unsuited for community screening. Bowel sounds (BSs) can be easily recorded with non-invasive and low-cost equipment. Recently, several researchers have pointed out changes in features obtained from BS according to the pathological condition of bowel motility. However a widely accepted, simple automatic BS detection algorithm still has to be found, and the appropriate recording period needs to be investigated for further evaluation of bowel motility. In this study we propose a novel simple automatic method to detect the BSs based on the 3 dB bandwidth of the frequency peaks in the autoregressive moving average spectrum. We use the measure, sound-to-sound interval (SSI) obtained by the proposed method, to capture bowel motility. In this paper, we show that the proposed method for automatic detection could achieve a sensitivity of 87.8±5.88%, specificity of 91.7±4.33% and area under the curve of 0.923 when working on 16 healthy volunteers during mosapride administrations. Furthermore, we show that the measured SSI averaged over a period of 30 min can clearly capture bowel motility. Our findings should have the potential to contribute toward developing automated BS-based diagnosis of IBS.

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A 5-GHz direct-conversion quadrature modulator has been developed using a frequency-doubling circuit technique to integrate a local oscillator on a single silicon chip. A three-level mixer, newly designed with symmetrical topology for two local oscillator inputs, is used to apply the frequency-doubling technique, so low image component levels of the modulated signals are achieved. The modulator is implemented on a single chip using Si-bipolar process technology with a cutoff frequency of 40-GHz. The image ratio is less than -34 dBc at a 5-GHz carrier frequency. I NT RO DUCT IONThe demand for low-cost wireless LANs with high transmission rates has grown over the past few years. A 5-GHz wireless LAN system built with inexpensive silicon chips would meet this demand, and several system components, including an up/down converter [l], have already been developed. However, the frequency of the developed oscillators on silicon is 2.4-GHz at most [2]. Such systems require a highfrequency local oscillator for carrier frequency generation. However, as the local oscillation frequency becomes higher, the oscillation phase noise and the error rate increases. Thus, it is difficult to implement an oscillator as a monolithic modulator on a single silicon chip. These problems could be overcome with a monolithic quadrature modulator whose local oscillation frequency can be reduced without reducing the carrier frequency.We propose a frequency-doubling modulator with a four-stage ring-type local oscillator and a novel "threelevel mixer (multiplier)". Since the local oscillation frequency is half that of the carrier frequency, the modulator is expected to have small phase noise. The local oscillator supplies four local oscillator signals with different phases to double the local oscillation frequency and to generate quadrature carriers. On the other hand, since the mixer has symmetrical topology for two local oscillator inputs, the modulated signals have low image component levels. CIRCUIT DESIGNA frequency-doubling quadrature modulator requires accurate four-phase local oscillator signals and a three-level mixer with symmetrical topology for multiplication of the signals. Since a four-stage ringtype oscillator generates the signals accurately and is suitable for integration on a silicon chip, it is used for the modulator. The mixer with symmetrical topology was newly designed and built. As shown in the block diagram in Fig. 1, the modulator consists of a fourstage ring-type local oscillator, four buffers, two threelevel mixers, an analog adder and an output buffer with a 50R load. The oscillator generates four phase local oscillator signals, namely LO-0, , whose phases are 0, 45, 90, and 135 degrees, respectively. The signals are supplied to the two mixers through the buffers. The I-channel mixer multiplies LO-0 and LO-90 to generate a carrier with a frequency that is twice that of LO, and the carrier is modulated by a baseband signal. On the other hand, the mixer for the Q-channel mixes LO-45, LO-135 and a baseband signal. Since th...