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Direct delta-sigma receiver architecture is introduced for wireless communication systems, such as LTE or WiMax. Architecture is based on direct downconversion, delta-sigma feedback that is up-converted to RF, and N-path filtering technique. Hence, the core receiver functions including channel selection filtering are embedded to a RF ADC with excellent linearity performance. This is achieved by transforming narrow-band filtering partially to RF injecting feedback into the input of the second amplifier stage, hence relieving requirements of the most critical subsequent stages. A 900-MHz direct delta-sigma receiver prototype occupies an active area of 1 2 mm 2 in 65-nm CMOS. The receiver for low-band cellular operations achieves NF of 2.3 and 6.2 dB in conventional and delta-sigma modes, respectively, and out-of-band IIP3 up to +4 dBm when the delta-sigma loop is active. The chip consumes 80 mW from a 1.2-V supply.

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GHz. The slightly different results of the simulations and measurement may be due to the fabrication tolerances. In addition, the proposed dual-band bandpass filter can generate two transmission zeros, which provide a better cut-off rate in the stopband and give much improved selectivity. CONCLUSIONA compact dual-band BPF using meandering SIRs has been proposed, which has good dual-passband performance at 2.4/5.25 GHz. The dual-passband characteristics are generated by properly controlling the impedance ratio of SIRs. The bandwidth of each passband could be controlled independently by tuning the coupling gap and the spur-line length. The circuit size is reduced about 50% compared with the conventional BPF with the same specifications. Finally, the simulated results are verified by our experiment of the fabricated dual-band BPF. ACKNOWLEDGMENTThis work is partially supported by the Science Funds of China U0635004 and No. 60571056, and the Science Funds of Guangdong 07118061. [5,6]. Several demodulation methods for retrieval of the cavity length from an optical spectrum have been proposed. The simple method of retrieving the cavity length is by using the peak-to-peak method to measure the wavelength spacing between two apexes in the spectrum, where there is a 2 phase shift [7]. The difficulty of this method is determining the peak positions in a white-light spectrum, because the waveform is in quasi-sine distribution, and there is great uncertainty in determining the peak position. The second method is linear or quadrature operation by keeping a /2 phase shift between the two interferometric beams [6]. Although the method has high resolution, the limited measuring range and ease of being affected by environ- ment and various imperfections of the sensor limit its application in practical engineering. The third popular method is determining the peak position of the main frequency component when the white-light optical spectrum is Fourier-transformed, and the cavity length can be calculated by using the frequency position of the main component [5]. However the resolution is much lower than other competitors, because the position of the main frequency component is insensitive to the change of the cavity length. Generally, we are not concerned with the absolute cavity length of an EFPI sensor. What we are interested in are the changes of the cavity length. For example, the initial strain is regarded as zero when an EFPI sensor is installed on a structure, and there is an initial cavity length. When the EFPI sensor is under loading, and the cavity length is changed, the strain is only reflected by the change of the cavity length, so it is also important to measure the changes of a cavity length. In this article, a Fourier-transform phase comparator is developed to measure the change of a cavity length, which keeps the properties of immunity to optical power fluctuations, large dynamic measurement range, and high resolution. MEASUREMENT PRINCIPLEThe spectral fringe amplitude of an EFPI for a WLI may be expressed as [4] ...