On the design of broadband quasioptical systems for submillimeter-wave radio-astronomy receivers

In this paper, we summarize the issues that should be considered when designing broadband quasioptical systems for submillimetre-wave radioastronomy receivers. We cover topics such as bandwidth, cross-talk, truncation, and aberrations, and we argue that it should be possible to manufacture high-efficiency systems that have several octaves of bandwidth. A key feature of the paper is that we use the language of multimode Gaussian optics throughout, and in this way, we emphasize that a receiver is a diffraction-limited imaging system rather than just a collection of components for guiding Gaussian beams. The whole discussion is conducted in terms of a particular system we are constructing for the James Clerk Maxwell Telescope in Hawaii.     

Universal receivers with side information from the demodulators: anexample for nonselective Rician fading channels

We consider binary orthogonal signaling over a nonselective Rician-fading channel with additive white Gaussian noise. The received signal over such a channel may have both a specular component and a scatter (Rayleigh-faded) component. If there is only a scatter component, the noncoherent receiver is optimal. If there is only a specular component, the optimal receiver is the coherent receiver. In general, the optimal receiver for a Rician channel depends on the strengths of the two signal components and the noise density, and the set of possible optimal receivers is infinite. We consider a system in which the noncoherent receiver and the coherent receiver are employed in a parallel configuration for a symbol-by-symbol demodulation of the received signal. Each sequence of transmitted symbols produces a sequence at the output of each of the parallel receivers. The task of identifying which of these received sequences is a more reliable reproduction of the transmitted sequence is the data verification problem. In this paper, we show that data verification can be accomplished by combining side information from the demodulators with a suitable error-control coding scheme. The resulting system is a universal receiver that provides good performance over the entire range of channel parameters. In particular, the universal receiver performs better than the traditional noncoherent receiver     

A parallel systems approach to universal receivers

The problem of communication over a channel with unknown characteristics is addressed. The true channel is from a known set of channels, but the transmitter and receiver do not know which of these channels is actually in effect. The goal of a universal receiver is to provide nearly optimal demodulation regardless of the channel that is actually in effect. A parallel receiver implementation is proposed for a universal scheme to cope with such uncertainty. The parallel system consists of a finite number of receivers with the property that, for each channel in the set, the performance of at least one of the receivers will be within a specified performance range. Data verification is accomplished by an appropriate coding system. Sufficient conditions for the existence of such a universal receiver for a prescribed set of channels are established, procedures are outlined for the receiver design, and an example is given to illustrate the applicability of the theory. For M-ary signaling it is shown that, from an information-theoretic viewpoint, the data verification can be achieved at no extra cost by use of the intrinsic side information that is provided by an appropriate coding scheme that also provides error correction     

Receiving antenna design for miniature receivers

A design procedure is described which determines the minimum required volume and the optimum dimensions for a ferrite loaded loop receiving antenna. The frequency of operation, bandwidth, transmitted signal strength, desired signal-to-noise ratio, receiver sensitivity, and the relative permeability of the ferrite are required to determine the design. Useful approximations for flux averaging, demagnetization factor, atmospheric noise, and chassis loadedQare given.     

Tuned front-end design for heterodyne optical receivers

A theoretical analysis of the noise performance of optical receivers with front-end tuning, suitable for wideband coherent systems, is presented. An algorithm for choosing the values of the tuning components in the front end so as to minimize the thermal noise output power has been developed. This theory is applied to the well-known simple parallel and serial tuning configurations and also to three more advanced designs. It is shown that any tuning is better than none in the wide-bandwidth designs considered and that the more advanced designs yield up to 12-dB reduction in thermal noise power. Two of the designs can be implemented with discrete components and should yield shot-noise-limited detection with 50-100 μW of local oscillator power in receivers with 5-GHz bandwidth. The practical problem of equalizing the front-end response is considered, and it is shown that good performance can be expected using realizable components     

MOS-only complex filter design for dual-band GNSS receivers

In this paper, the use of MOS-only active filters in the implementation of area-effective low-IF image reject filters is discussed. For this purpose, complex filter design procedure is considered regarding MOS-only filter realization techniques and a new second-order filter topology which favors filter’s area-effective implementation is proposed. Owing to the presented approach, a new complex image-reject filter with reduced chip area, which can be used in dual-band GNSS receivers, is obtained. Issues related to IQ imbalance are briefly discussed and a calibration imbalance circuit is proposed. By virtue of the current-mode design technique, the IQ imbalance circuit is embedded with the complex filter, simplifying the system topology. In order to illustrate the feasibility of the filter, post-layout simulation results of a fourth-order Butterworth-type image reject filter designed for dual-band GNSS receivers are provided using SPECTRE simulation tool in CADENCE design environment.     

Anti-blocker design techniques for MOSFET-C filters for directconversion receivers

A linearized MOSFET-C low-pass filter suitable for a baseband channel selection filter for a direct conversion receiver is presented. Using polysilicon resistors instead of MOSFET resistors in the input and output part, the filter achieves very high out-of-band linearity but maintains the original transfer function under the control of a continuous on-chip cutoff tuning scheme. In order to enhance the linearity of the triode-mode MOSFET variable resistors, the gates of the MOSFETs are driven by a charge pump in the cutoff control loop. Also, an appropriate gain scaling is implemented to lower the input referred noise, thus making the out-of-band dynamic range wider. This fifth-order elliptic filter achieves -2 dBV in-band IIP3, +28 dBV out-of-band IIP3, +94 dBV out-of-band IIP2 and -87 dBV input-referred noise, and dissipates 6.2 mW from a 2.7-V supply; the on-chip continuous automatic tuning system dissipates 4.1 mW     

Improved design of tuned optical receivers

We present new design principles for improved heterodyne tuned optical receivers where several tuning inductances reduce the influence of thermal receiver noise over a broad frequency range. A theoretical example for a 600 MHz tuning bandwidth shows a reduction of thermal receiver noise (and thus in required local oscillator power) of up to 13dB. The example is tested experimentally for the so-called mixed tuning configuration. We obtain good agreement with the theoretical predictions. The experimental RMS noise current is <5pA/?(Hz) over a 580 MHz bandwidth with the lowest value of 3-5 pA/?(Hz) at 950MHz.     

A single-chip CMOS IF-band converter design for DVB-T receivers

This paper describes a CMOS single-chip IF-band converter (IFC) which is applied in the analog front end circuitry of DVB-T receivers. The proposed IFC is composed of a down-conversion mixer, an automatic gain controller (AGC), and an anti-aliasing filter (AAF). The down-conversion mixer uses a current folded-mirror technique which converts a 36 MHz intermediate frequency (IF) input into a 4.5 MHz baseband signal. The AGC loop applies a novel digital variable gain amplifier (VGA) basing on a g_m-boosting DVGA (digital VGA). A total of three tunable gain stages are cascaded to provide a 70 dB dynamic range. A temperature-compensated 6th order transconductance-C (Gm-C) filter with digitally tunable bandwidth (6, 7, 8 MHz) is used to constitute the proposed AAF. Moreover, a temperature-compensated circuitry is used to neutralize the AAF's bandwidth drifting caused by the temperature variation.     

Computer-aided design of hybrid and monolithic broad-bandamplifiers for optoelectronic receivers

In very-high-data-rate fiber-optic systems, it is necessary to have an ultrawideband, high-gain, low-noise amplifier after the front end. The authors show how powerful analytical techniques, such as the real frequency technique, can be applied to the design of a 4-MHz-7-GHz amplifier. A two-stage monolithic amplifier designed according to the theory gives 17-dB gain; a three-stage hybrid amplifier exhibits 16-dB gain across the same frequency band. The gain, noise figure, and pulse response of each amplifier are presented     

On multicast flow control for heterogeneous receivers

In this paper, we study the impact of heterogeneous receivers on the throughput of multicast flow control and propose a new multicast flow control algorithm to optimally partition group members into multiple subgroups. Our main contributions are as follows. First, we cast the multicast flow control problem in the Internet as the list partition problem and then prove that the list partition problem is equivalent to the optimal paging problem in cellular networks. The result is not only interesting in itself but also essential to derive the first known analytical bounds for the throughput of multicast flow control. Furthermore, we propose an algorithm to solve not only the list partition problem but also the optimal paging problem and the problem of bulk data transfer using multiple multicast groups. The complexity of our algorithm is one order less than the best known algorithm designed only for the problem of bulk data transfer using multiple multicast groups in the literature. While earlier work uses simulations to justify the usage of multiple subgroups to deliver information to a large amount of receivers in heterogeneous networks, we provide the first analytical support     

High-speed Si-bipolar IC design for multi-Gb/s optical receivers

The authors developed several special circuits to minimize the decrease in speed caused by parasitics. The common-base circuit assures flat and wide frequency preamplifier response even when V_ee is unstable because of bond wire inductance. Cascode interconnections between circuit blocks prevent waveform degradation due to line capacitance discharge. The high level of integration prevents the signal speed from decreasing due to chip interfaces and external interference. Using these circuits and Si-bipolar ESPER (emitter-base self-aligned structure with polysilicon electrodes and resistors) transistors whose f_T was 28 GHz, the authors fabricated three ICs: a preamplifier with a 5.1 GHz bandwidth, a fully integrated automatic gain control (AGC) amplifier with a 3.6 GHz bandwidth, and a decision circuit that operates at 10.6 Gb/s. The authors used these ICs and an avalanche photodiode (APD) to construct a 5 Gb/s optical receiver with a minimum detectable optical power of -26.8 dBm. The speed of the Si ICs exceeded 5 Gb/s     

Unified design of iterative receivers using factor graphs

Iterative algorithms are an attractive approach to approximating optimal, but high-complexity, joint channel estimation and decoding receivers for communication systems. We present a unified approach based on factor graphs for deriving iterative message-passing receiver algorithms for channel estimation and decoding. For many common channels, it is easy to find simple graphical models that lead directly to implementable algorithms. Canonical distributions provide a new, general framework for handling continuous variables. Example receiver designs for Rayleigh fading channels with block or Markov memory, and multipath fading channels with fixed unknown coefficients illustrate the effectiveness of our approach     

高线性度组件简化了直接转换接收器的设计

直接转换无线电接收器可获取一个频率范围为800MHz～3GHz的高频输入信号,并利用一个混频器/解调器将该信号转换至基带,而无须经过一个中频(IF)级.     

Analysis and design of optimum interleaver for iterative receivers in IDMA scheme

In this paper, we propose a new tree based interleaver (TBI) to generate different chip‐level interleaving sequences for different users in an interleave division multiple access (IDMA) system, which reduces computational complexity. This method of generation also solves the memory cost problem and reduces the amount of information exchange between mobile stations (MSs) and base stations (BSs) required to specify the interleaver. Simulation results are presented to show that the proposed interleavers perform well as compared to random interleavers in an IDMA system. Copyright © 2008 John Wiley & Sons, Ltd.     

On noncoherent receivers for DSTM in spatially correlated fading

In this letter, we derive a multiple-symbol differential detection (MSDD) and a novel MSDD-based decision-feedback differential detection (MS-DFDD) receiver for differential space-time modulation transmitted over spatially correlated multiple-input multiple-output fading channels. We show that MS-DFDD outperforms previously proposed DFDD schemes that are based on scalar and vector prediction (SP-DFDD and VP-DFDD). In addition, we prove that at high signal-to-noise ratio (SNR) VP-DFDD is equivalent to SP-DFDD and thus fails to properly exploit the spatial fading correlations.     

On the existence of universal nonlinearities for blind sourceseparation

Many density-based methods for blind signal separation employ one or more models for the unknown source distribution(s). This paper considers the issue of density model mismatch in maximum likelihood (ML)-type blind signal separation algorithms. We show that the score function nonlinearity, which was previously derived from the standpoint of statistical efficiency, is also the most robust in maintaining a separation solution for the ML algorithm class. We also consider the existence of a universally applicable nonlinearity for separating all signal types, deriving two results. First, among nonlinearities with a convergent Taylor series, a single fixed nonlinearity for universal separation using the natural gradient algorithm cannot exist. Second, among nonlinearities with a single adjustable parameter, a previously proposed threshold nonlinearity can separate all signals with symmetric amplitude distributions as long as the threshold parameter is properly chosen. The design of "difficult-to-separate" signal distributions is also discussed     

The design of tuned front-end GaAs MMIC optical receivers

Recently, much interest has been shown in the design of very low noise tuned front-end optical receivers for use in lightwave systems. This paper looks at the accurate design of such receivers. Simplified design expressions are presented for a number of tuning configurations with theoretical and measured results being presented. The designs were realized as GaAs monolithic microwave/millimeter-wave integrated circuits (MMIC's)     

Surrogate-channel design of universal LDPC codes

A universal code is a code that may be used across a number of different channel types or conditions with little degradation relative to a good single-channel code. The explicit design of universal codes, which simultaneously seeks to solve a multitude of optimization problems, is a daunting task. This letter shows that a single channel may be used as a surrogate for an entire set of channels to produce good universal LDPC codes. This result suggests that sometimes a channel for which LDPC code design is simple may be used as a surrogate for a channel for which LDPC code design is complex. We explore here the universality of LDPC codes over the BEC, AWGN, and flat Rayleigh fading channels in terms of decoding threshold performance. Using excess mutual information as a performance metric, we present design results which support the contention that an LDPC code designed for a single channel can be universally good across the three channels.     

一种通用的OFDM发射机设计

正交频分复用（OFDM）系统参数众多,设计灵活,可以根据不同用途、信道环境以及接收机的性能等,设计出很多不同的OFDM系统。针对此问题,提出了一种通用的基于训练序列的OFDM发射机设计方案。从性能的角度出发,设计了OFDM符号结构和传输帧结构,并重点分析了OFDM数字基带调制模块的组成,最终在Xilinx开发板上实现了该方案,并获得了OFDM各模块的仿真时序图、OFDM射频信号频谱和误比特率图。研究结果表明,该方案频谱利用率高,复杂度低,通用性好。