One of the recent trends in multimode multiband (MMMB) receivers is to remove the analog filter or variable-gain amplifier (VGA) in the receiver chain and employ a wide-dynamic-range ADC directly after the mixer or include the mixer in the ADC [1,2]. While such architecture provides ease of programmability once the signals are digitized, it puts a large burden on the ADC and anti-alias filter. Hence, ADCs typically use high-performance analog circuits for wide dynamic range, even though it is difficult to implement these circuits using low-voltage nanoscale CMOS processes. A promising ADC architecture for an MMMB receiver is the VCO-based ADC, since it offers 1st-order noise-shaping from its open-loop digital-intensive nature, thus allowing high sampling rate and high SNR [3]. Furthermore, the VCO-based ADC provides an inherent anti-aliasing 1st-order Sinc filter due to the innate integrating ability of the VCO [4]. Unfortunately, for multiband receivers that do not have an RF pre-filter, a Sinc filter alone does not provide enough out-of-band rejection and hence higher-order anti-aliasing filters are required. In order to solve this problem, we propose a 2nd-order anti-aliasing Sinc filter (Sinc2 filter) that provides double the rejection ratio of a Sinc filter. Furthermore, the proposed technique is highly digital and can be embedded in a VCO, resulting in little overhead.
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机译：之一的多模多频带（MMMB）接收器的最近的趋势是，以除去在接收器链中的模拟滤波器或可变增益放大器（VGA）和混频器后直接采用宽动态范围ADC或包括在ADC混合器[1,2]。而一旦信号被数字化，这样的架构提供了易于编程的，它把一个很大的负担上ADC和抗混叠滤波器。因此，ADC通常使用高性能的模拟电路为宽动态范围，即使它是难以实现使用低电压的纳米级CMOS工艺这些电路。的MMMB接收机有前途的ADC体系结构是基于VCO的ADC，因为它提供了1 ST 阶从其开环数字密集性质噪声整形，从而使高采样率和高SNR [3]。此外，基于VCO的ADC提供了一种固有的抗混叠1 ST 阶SINC滤波器由于VCO [4]的积分先天能力。不幸的是，对于不具有RF预过滤器的多频带接收机中，一sinc滤波器不能单独提供出来的带外抑制不够，因此高次都需要抗混叠滤波器。为了解决这个问题，我们提出了一个2 第二阶的抗混叠SINC滤波器（Sinc函数 2 过滤器），其提供一sinc滤波器的两倍抑制比。此外，所提出的技术是高度数字并可以嵌入在一个VCO，导致小的开销。
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