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Nowadays, terms such as 'Smart Textile', 'Intelligent Textile' and 'Wearable Computing' are commonly used in everyday contexts. And radio-frequency identification (RFID) is the use of a wireless non-contact system that uses radio-frequency electromagnetic fields to transfer data from a tag attached to an object, for the purposes of automatic identification and tracking. These products are required technologies which are textile treatments, printing, ink, etc. Durability of textile substrates is an essential marker for conductive ink printing process. Especially, heat stability is important, since conductive ink should be processable (annealing, curing) at temperatures below 150 . This study was application of RFID

In this study, we have fabricated an RFID tag antenna of the sewing type, and not the embroidery type. Inaddition, we have measured its impedance, return loss, and reading range. The sewing patterns of two different den-sities are fabricated, and the properties of the RFID tag antenna have been measured. The measurement results showthat the two-layer sewing pattern RFID tag antennas are better than the one-layer sewing pattern antennas. Upon com-parison, with regard to the effect of the sewing density, it is found that a lower density is a better property. The max-imum reading ranges are 70, 49, 84, and 85 cm, which are sufficiently long.Keywords: RFID, UHF RFID tag, sewing type RFID tag antenna 1. 서 론 최근 기존 전통산업의 성장 잠재력의 한계를 극복하기위해 산업간 융합을 통한 새로운 산업 및 기술을 발굴하려는 다양한 노력들이 산업전반에서 전개되고 있는 실정이다.특히 의복형태의 컴퓨터로 대표되는 웨어러블 컴퓨터는 섬유 및 의류 기술과 IT 기술과의 산업적 융합의 대표적인분야라고 할 수 있다[1]. RFID(Radio Frequency IDentification)는 무선으로 사물을 인식하는 기술로 기존의 바코드 시스템을 대체할 수 있을 뿐만 아니라, 새로운 물류응용 분야에 적용할 수 있는신기술로 주목 받고 있다. RFID 기술은 각 사물에 태그를부착하여 그 태그의 고유 ID를 무선으로 인식하여 정보를수집, 저장, 추적 관리함으로써 사물의 관리 서비스를 제공하는 기술이다[2,3]. 현재 정보인식 기술로 대중화된 방식은 바코드(bar code)와 마그네틱 카드(magnetic card)이다.저렴한 단가에도 불구하고 바코드는 물에 젖거나 오염 물질이 묻어 바코드가 손상되면 정보를 제대로 전달할 수 없다. 뿐만 아니라, 바코드와 마그네틱 카드 모두 아주 가까운 거리에서 접촉을 시켜야 정보가 인식된다는 단점을 안고 있다. 반면 RFID는 전파를 이용해 다양한 정보를 전달하기 때문에 이런 한계로 부터 자유롭다. 게다가 바코드가일직선상에서만, 또 한번에 하나씩의 매우 제한된 용량의데이터만 인식할 수 있는 반면, RFID는 동시에 여러 개의대용량의 정보를, 상당히 먼 거리에서도 인식하고 기록, 저장할 수 있다.

In this article, a CMOS multistandard wireless direct-conversion receiver is designed. The receiver is composed of three components: low noise amplifier, voltage-controlled oscillator, and mixer. In details, the designed receiver adopts direct-conversion architecture and accommodates three standards: WCDMA, Wibro (or mobile WIMAX), and CDMA 2000 1×: 1.84–2.4 GHz. The designed mixer is a passive sub-harmonic doubly balanced structure, the VCO is a back-gate coupling quadrature VCO, and the LNA is a differential structure. Each component is designed with relevance to direct-conversion architecture. The designed mixer has no flicker noise theoretically because the mixing transistors operate in the triode region. Also, DC offset problem is avoided, because local oscillator frequency is half of RF frequency and the port isolation is improved by the innate characteristic of a balanced structure. The VCO generates a quadrature signal and the oscillation frequency is half of RF frequency to drive designed sub-harmonic mixer. No coupling transistors are needed due to the use of back-gate coupling to reduce flicker noise. Back-gate coupling means that the body of a transistor is used as another gate. The LNA, which adopts a well-known cascade structure, is designed as a differential structure to suppress common mode noise and to drive a doubly balanced mixer. All designed components are fabricated by the TSMC 0.18-μm RF CMOS process. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 718–721, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24989

A passive mixer provides a good linearity and noise figure. Above all, it is definite that the flicker noise is suppressed from the simulation result. The QVCO can oscillate the wide range frequency so as to support multi-bands wireless communication services. The measured phase noise shows that it is suitable for the standard of each service.

In this letter CMOS multi-standard wireless direct-conversion receiver is presented. That is composed of wideband LNA, passive double-balanced sub-harmonic mixer, and back-gate coupled quadrature voltage controlled oscillator (QVCO). The frequency operating band of the LNA covers three standards, and it has a differential structure to drive double balanced mixer. The mixer achieved low flicker noise corner and high LO-RF port isolation by using passive sub-harmonic structure. The back-gate coupled QVCO is the structure that uses body connection as another gate. Therefore no coupling transistor is needed, so better phase noise performance is offered.

In this paper, quadrature VCO adopts back-gate coupling instead of coupling transistor topology to get low phase noise and low power consumption. The 2-bit switch capacitor arrays and two MOS varactors are used to widen the frequency range in the band tuning circuit. As a result, the proposed LC quadrature VCO shows excellent performances of power consumption and phase noise for the frequency band of three standards: CDMA2000 lx, WCDMA, and WiBro.