Design of Reconfigurable Digital IF Filter with Low Complexity
ABSTARCT :
Due to limited frequency resources, new services are being applied to the existing frequencies, and service providers are allocating some of the existing frequencies for newly enhanced mobile communications. Because of this frequency environment, repeater and base station systems for mobile communications are becoming more complicated, and frequency interference caused by multiple bands and services is getting worse. Therefore, a heterodyne receiver using IF filters with high selectivity has been used to minimize the interference between frequencies. However, repeater and base station systems in mobile communications employing fixed IF filters cannot actively cope with the usage of multiple frequency bands, the application of various services, and frequency recycling. Therefore, this brief proposes a reconfigurable digital IF filter with variable center frequency and bandwidth while achieving high selectivity as existing IF filters. The center frequency of filter can vary from 10MHz to 62.5MHz, and the filter bandwidth can be selective to one of 10MHz, 15MHz, and 20MHz. The proposed digital filter also reduces the complexity of adders and multipliers by 38.81% and 41.57%, respectively, compared to an existing digital filter by using a filter bank and a multi stage structure. This digital IF filter is fabricated on a 130-nm CMOS process and occupies 5.90 mm2.
EXISTING SYSTEM :
? Most of the existing filter and filter bank architectures are designed and optimized for supporting single communication standard.
? The proposed coefficient representation technique uses pipelining technique in order to increase the performance and we also focus on increase the filter order i.e filter order to save more area as compared to existing methods.
? SDRs and CRs need multistandard wireless communication receivers (MWCRs) to integrate existing as well as imminent communication standards into a single generic hardware platform.
? The VDFs and filter banks should be reconfigurable to support distinct frequency specifications corresponding to existing as well as imminent communication standards.
DISADVANTAGE :
? Due to the channel fading, interference and hidden terminal problems, a reliable, low complexity and fast spectrum sensing is one of the most vital requirements in MMCRs.
? The advancements in mobile communications have also made prominent impact on improving education, health, public safety, disaster management, banking services etc.
? The CDM has inherent disadvantage of deterioration in stopband attenuation as well as the TBW for higher decimation factors and hence the prototype filter needs to be over-designed.
? The FFB, multi-resolution and non-uniform FFB provide low complexity alternative to modulated filter banks but they have same drawbacks as that of modulated filter banks.
PROPOSED SYSTEM :
• We propose an improved and low complexity reconfigurable filtered OFDM (LRef-OFDM) based LDACS using novel interpolation and masking based multi-stage digital filter.
• The proposed filter is designed to meet the stringent non-uniform spectral attenuation requirements of LDACS standard.
• The proposed filter employs the interpolation operation to reduce the complexity.
• A new hardware efficient reconfigurable FIR filter architecture is proposed in this paper based on the proposed binary signed sub coefficient method.
• Some techniques have been proposed to minimize the number of required adders for multiplier implementation.
ADVANTAGE :
? A digital FIR filter can change its center frequency and bandwidth by adjusting filter coefficients.
? The filter coefficients for adjusting the center frequency and the bandwidth of IF filter is set via the UART from external control devices such as a micro-controller.
? The performance and computational complexity of subsequent DSP algorithms significantly depend on the filtering performance of the DFE.
? The CFD takes advantage of cyclostationary properties of the input signal and have better performance than the energy detection at low SNR.
? In base stations and repeaters, spectrum efficiency is maximized by using filters to minimize the interference of adjacent frequencies.
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