A low-power low-phase-noise LC VCO with MEMS Cu inductors

A 2-3 GHz CMOS inductance-capacitance (LC) voltage-controlled oscillator (VCO) integrated with high-Q micro-electromechanical systems (MEMS) Cu inductors is reported. While dissipating only 6.3 mW, a phase noise of -121 dBc/Hz at 600 kHz offset from 2.78 GHz carrier is achieved. This MEMS VCO has the largest power-frequency normalized figure-of-merit (12.5 dB) among the Si bipolar and CMOS LC VCOs.     

Frequency-selective surface for microwave power transmission

Using an equivalent-circuit model, frequency-selective surfaces (FSS's) with gridded- and double-square elements have been designed and tested for suppressing the harmonics radiation in microwave power transmission system. It is shown that the angular sensitivity of the frequency response of the FSS arrays can be reduced with a combination of TE- and TM-polarized incident waves or a circularly polarized incident waves instead of a single TE- or TM-polarized incident wave. The FSS arrays have also been measured in a microwave anechoic chamber and a good agreement is obtained between the theoretical calculations and experimental results     

基于小波的频率选择性瑞利衰落信道估计

频率选择性快衰落信道的精确估计对接收机性能的提高起着重要作用。本文采用小波基表示频率选择性快衰落信道，并由此提出两种估计时变信道的算法，瑞利快速衰落信道下的仿真结果表明，信道估计精度较之传统的LMS和RLS算法有明显提高。     

Frequency-selective integrated circuits using phase-lock techniques

A system-oriented approach to the design of inductorless tuned integrated circuits is described. This design method uses the phase-locked loop (PLL) techniques to obtain the desired tuning and interference-rejection characteristics. The PLL approach does not require tight control of component tolerances, and offers a higher selectivity and frequency capability than the corresponding active-RC synthesis methods. In this paper, basic design parameters for phase-locked integrated circuits are given, and two separate design examples are described. First is a high- frequency (1 to 25 MHz) FM amplifier/detector, which forms a monolithic replacement for the IF strip and the detector sections of a conventional FM receiver or TV sound system. The second is an integrated FM multiplex receiver for multi-channel telemetry applications, which has the selectivity of a 6-pole bandpass filter and can be tuned by means of an external resistor or capacitor from a fraction of a cycle to over 300 kHz.     

Frequency-selective scanning of acoustic surface wave

An acoustic-surface-wave point source is obtained when an interdigital transducer with concentric curved fingers is used. An array transducer composed of 80 point sources has been tested. The direction of propagation of the surface-wave beam emitted by this transducer depends on the frequency. A transmitting-array transducer and five receiving transducers are deposited on a quartz substrate. Each of these five outputs corresponds to a given frequency and delay prescribed by the positioning. At 12°, scanning was attained for a frequency variation of 7.6 MHz around a central frequency of about 60 MHz, corresponding to a delay variation of 18.2 ?s.     

Frequency-selective Scheduling Scheme in LTE System

从无线资源分配的角度出发,提出了一种频选调度方案,旨在充分利用LTE系统频谱资源的前提下提高小区的吞吐量.频选调度方案设计的MAC层调度器可以按照UE上报的信道质量指示,将可以使用的资源分为不同的优先级,然后把最好的资源分配给相应的UE,实现频选调度策略.通过系统级仿真可知,该方案能提高用户的性能.     

Frequency-selective surface using aperture-coupled microstrip patches

A new type of frequency-selective surface using aperture-coupled microstrip patches is described. The geometry uses two back-to-back arrays of microstrip antennas with coupling apertures in the common ground plane, and provides a narrow passband response that may be useful for radome and RCS reduction applications. Calculated results demonstrate the operation of the structure, and are verified with measurements using a waveguide simulator.<>     

Frequency-selective properties of modified dielectric gratings

Several modifications of dielectric gratings are studied by the mode matching technique, which was shown to be quite adequate for the analysis of such structures in our previous works. These modifications include a socalled metal-dielectric grating, i.e., a dielectric grating, in which the inner faces of the rods are covered with a thin conducting layer, and a matched dielectric grating. The former grating is paid especial attention because of its unique frequency-selective properties.     

Fast low-power decoders for RAMs

Decoder design involves choosing the optimal circuit style and figuring out their sizing, including adding buffers if necessary. The problem of sizing a simple chain of logic gates has an elegant analytical solution, though there have been no corresponding analytical results until now which include the resistive effects of the interconnect. Using simple RC models, we analyze the problem of optimally sizing the decoder chain with RC interconnect and find the optimum fan-out to be about 4, just as in the case of a simple buffer chain. As in the simple buffer chain, supporting a fan-out of 4 often requires noninteger number of stages in the chain. Nevertheless, this result is used to arrive at a tight lower bound on the delay of a decoder. Two simple heuristics for sizing of real decoder with integer stages are examined. We evaluate a simple technique to reduce power, namely, reducing the sizes of the inputs of the word drivers, while sizing each of the subchains for maximum speed, and find that it provides for an efficient mechanism to trade off speed and power. We then use the RC models to compare different circuit techniques in use today and find that decoders with two input gates for all stages after the predecoder and pulse mode circuit techniques with skewed N to P ratios have the best performance     

一种具有双吸收带的频率选择特性吸波器

提出了一种三维的具有双吸收带的频率选择传输(AFST)结构,该结构由嵌有片式电阻器的金属条和平行板波导结构嵌套组成,可以实现吸收-传输-吸收的特性,即在通带两侧各有一个吸收带,且具有每个吸收带包含2个反射零点宽带性能。推导了该结构的等效电路模型研究设计理念,并通过仿真得到了在斜入射情况下性能仍然可以保持稳定的结果,验证了所提出等效电路模型的有效性和所设计的AFST结构的频率选择特性。     

Bit-swapping LFSR for low-power BIST

A modified linear feedback shift register (LFSR) is presented that reduces the number of transitions at the inputs of the circuit-under-test by 25% using a bit-swapping technique. Experimental results on ISCAS'85 and 89 benchmark circuits show up to 45% power reduction during test. They also show that the proposed design can be combined with other techniques to achieve a very substantial power reduction of up to 63%.     

Asynchronous switching for low-power networks-on-chip

Asynchronous switching is proposed to achieve low power Network on Chip. Asynchronous switching reduces the power dissipation of the network if the activity factor of the data transfer between two ports α_data is less than Aα_c+Bα_clk. Closed form expressions for power dissipation of different network topologies are provided for both synchronous and asynchronous switching. The expressions are technology independent and are used for power estimation. Asynchronous switching is compared with synchronous switching for different network densities N/L_cXL_c. The area of the asynchronous switch is 50% greater than the area of the synchronous switch. However, the power dissipation of asynchronous switching decreased by up to 70.8% as compared to the power dissipation of the conventional synchronous switching for Butter-Fly Fat Tree (BFT) topology. Asynchronous switching is more efficient in CLICHE topology than in both BFT and Octagon topologies achieving higher power reduction 75.7%. Asynchronous switching becomes more efficient as technology advances and network density increases. A reduction in power dissipation reaches 82.3% for 256 IPs with the same chip size. Even with clock gating, asynchronous switching achieves significant power reduction 77.7% for 75% clock activity factor.     

频率选择性衰落信道下的BLAST新方案

提出一种将贝尔实验室分层空时(BLAST)技术与RAKE接收机相结合的方案,介绍了该方案的算法原理,并与现有的频率选择性衰落信道下的BLAST方案进行了仿真对比.结果表明新方案在系统性能损失不大的情况下,极大地降低了系统复杂度.     

Frequency-selective transmission by a leaky parallel-plate-like waveguide

The phenomena of high frequency-selective transmission of a plane wave by a dielectric two-dimensional (2-D) periodic waveguide, comprising a uniform dielectric layer sandwiched by two finite thickness 2-D periodic structures served as the waveguide wall is described. This structure is termed a leaky parallel-plate-like waveguide because the waveguide walls are not perfect reflection mirrors. The scattering characteristics and dispersion relation, including the phase and attenuation constants, of the 2-D periodic waveguide are thoroughly analyzed with the modal transmission-line method and Floquet theory. The extraordinary open stopbands caused by the contra-flow coupling between a leaky parallel-plate-like waveguide and the leaky waves, which are generated by 2-D periodic structures (waveguide walls), are displayed in the form of the Brillouin diagram. The phase-match condition is used to verify the resonant coupling between the incident plane wave and the leaky parallel-plate-like waveguide modes. Specifically, the transmission peak frequencies are accurately predicted.     

Frequency-selective surfaces based on shorted ring slots

A periodic structure based on shorted ring slots is investigated. It is shown that this structure can be used as an adjustable frequency-selective surface. The possibility of adjusting the resonant frequency over more than an octave frequency band is demonstrated     

Opcode encoding for low-power instruction fetch

A method for encoding opcodes for low-power instruction fetching is described. To reduce the switching activity from opcode changes in the instruction fetch logic, opcodes are assigned so that more frequently consecutive instruction pairs have a smaller Hamming distance between their opcodes. The experimental result shows that a switching activity reduction of 37.4-66.7% is achievable over a naive encoding method     

Low-voltage low-power controllable preamplifier for electretmicrophones

A low-voltage low-power analog controllable preamplifier for electret microphones is discussed. It has been designed for a single supply voltage of 1.0 V, whereas its average power consumption amounts to some tens of microwatts. A DC current controls its gain directly into decibels. The design meets specifications concerning accuracy, bandwidth, and noise properties suitable for most applications in portable telephone equipment, portable transceivers, and hearing aids. Much attention has been paid to the dynamic range of the input signal, noise, and offset properties. The circuit has been realized in a semicustom IC process. Simulation and measurement data of the most important properties are presented     

Sequence-switch coding for low-power data transmission

Reducing the power dissipated by buses becomes one of the most important elements in low-power VLSI design. A new coding scheme called sequence-switch coding (SSC) is proposed in this paper. It is a general-purpose coding scheme that employs the sequence of data in reducing the number of transitions on buses. A simple switching algorithm is presented to show the feasibility of SSC. According to simulations, this algorithm reduces around 10% of bus transitions in the transmission of benchmark files. SSC can be used for burst data transfer in any application. In particular, it is suitable for internet and multimedia applications that have stream-type data transfer pattern.     

Frequency-selective multiple-input multiple-output channel estimation with transmitter non-linearities

The authors propose an algorithm based on the knowledge of training sequences to obtain an asymptotically unbiased estimator of non-linear multiple-input multiple-output (MIMO) channels, which involves the radio frequency front-end non-linearity and linear frequency selective MIMO channels. Although the impact of non-linearity in the transmitter side has been widely studied, most work on the channel estimation assumes linear channel models and ignores the non-linear effects. In this study, we develop a nonlinear channel estimator that can simultaneously estimate the linear MIMO channel model and non-linearity of the transmitter is developed. With these two sets of parameters, the non-linear channel model can be fully described. This channel estimation algorithm is implemented over an empirical MIMO channel model using an orthogonal frequency division multiplexing system.     

Segmented bus design for low-power systems

This paper proposes a bus-segmentation method that efficiently reduces the switched capacitance on the bus. The power consumed by the bus can, therefore, be substantially reduced. The basic idea of bus segmentation is to partition the bus into several bus segments separated by pass transistors. Highly communicating devices are located to adjacent bus segments, thus, most data communication can be achieved by switching a small portion of the bus segments. As a result, power consumption and critical path delay are both reduced. Experimental results obtained by simulating a delay model and a power model demonstrate that the proposed segmented bus system reduces bus power by about 60%-70% and improves critical bus delay by about 10%-30%