A 1-MHz-bandwidth second-order continuous-time quadrature bandpass sigma-delta modulator for low-IF radio receivers

This paper presents a quadrature bandpass /spl Sigma//spl Delta/ modulator with continuous-time architecture. Due to the continuous-time architecture and the inherent anti-aliasing filter, the proposed /spl Sigma//spl Delta/ modulator needs no additional anti-aliasing filter in front of the modulator in contrast to quadrature bandpass /spl Sigma//spl Delta/ modulators with switched-capacitor architectures. The second-order /spl Sigma//spl Delta/ modulator digitizes complex analog I/Q input signals at 1-MHz intermediate frequency and operates within a clock frequency range of 25-100 MHz. The modulator chip achieves a peak signal-to-noise-distortion ratio (SNDR) of 56.7 dB and a dynamic range of 63.8 dB within a 1-MHz signal bandwidth and at a clock frequency of 100 MHz. Furthermore, it provides an image rejection of at least 40 dB. The 0.65-/spl mu/m BiCMOS chip consumes 21.8 mW at 2.7-V supply voltage.     

Detection of the pulsed Poisson radio emission by quadrature receivers

This study deals with the reception by quadrature receivers of pulse sequences of the radio-frequency emission against the background of noise, when the number of received radio pulses obeys the Poisson distribution, while the pulse amplitudes contain regular and random components. The expressions were obtained for detection characteristics of the emission subject to registration. The correct detection probability was analyzed as a function of the signal-to-noise ratio, false alarm probability, and the ratio of the regular and fluctuating components of amplitudes of pulses.     

Low sensitivity complex image rejection filter for GNSS receivers

In this paper, a new approach for the design of a low sensitivity complex-filter is proposed. The approach is based on realising the filter using low sensitivity allpass sections. The complex filter obtained can be used as image-reject filter in low-IF GNSS receivers. The filter configuration is modular, i.e. is composed of the same subcircuits which simplifies the design of the circuit. A Chebyshev type OTA-C image-reject filter obtained by cascading two third-order allpass-based complex filters is presented. Post layout simulation results of the filter using SPECTRE in CADENCE design tool verifying its proper operation are provided.     

An LO architecture with novel wide locking range,quadrature output RILFDs and ILROs for cognitive radio applications

In this paper, a wide locking range, quadrature output ring type injection locked frequency divider (ILFD) is presented for division ratios of 3 and 4. This ILFD proposes a novel injection scheme that shapes the injection signal to a proper form and provides a convenient situation for divider locking. Furthermore, two new wide locking range, low power consumption, injection locked ring oscillators (ILROs) are proposed for quadrature generation in local oscillator architectures. A novel cognitive radio quadrature local oscillator (LO) architecture is presented by utilizing the proposed ILFDs and ILROs to verify the effectiveness of the proposed circuits. Moreover, a new technique is implemented on the LO architecture to widen the frequency range without consuming any extra power. Because of using a single LC tank, this architecture is very compact. Also, it has the benefit of low power consumption and low output phase noise.     

Submillimeter receivers for radio astronomy

The state of development of receivers for submillimeter-wave radio astronomy is reviewed. Bolometers for continuum observation, hot-electron mixer receivers for narrowband spectral line observation, and heterodyne receivers, both Schottky diode and superconducting tunnel junction, are presented. At the lower frequency end of the submillimeter band, standard waveguide techniques, scaled from millimeter wavelengths, prevail. At wavelengths shorter than about 0.5 mm, quasioptical designs are preferred. In the case of Schottky diode receivers, corner cube designs are used almost exclusively, whereas integrated mixer designs are the focal point of research for superconductor-insulator-superconductor (SIS) receivers at these wavelengths. Although such designs are extensively reviewed, it is nevertheless the Schottky diode mixer remains the element of choice at the shortest submillimeter wavelengths     

A 9.8-11.5-GHz quadrature ring oscillator for optical receivers

This paper describes a quadrature ring oscillator that is tunable from 9.8 to 11.5 GHz in a 30-GHz f_T BiCMOS technology. The ring oscillator can be used in advanced data clock recovery architectures in optical receivers. The circuit implementation of the oscillator uses transistors as active inductances. Isolation between the oscillator and cascaded circuits, such as buffers and flip-flops, is improved by utilizing the active inductances in a cascode configuration. Carrier to noise ratios better than 94 dBc/Hz at 2-MHz offset are measured with 75-mW dissipation and 2.7-V supply voltage. The evolution in two-stage ring oscillator topologies, leading to the realized design, is discussed in detail on the circuit level     

A process-tolerant out-of-band blocker rejection technique for SAW-less receivers

In this paper, an active filtering technique is presented which is capable of filtering the out-of-band blockers in wireless receivers. The concept is based on the feedforward cancellation technique where a blocker replica is subtracted at the output of the low-noise amplifier (LNA). In contrast to the previously reported feedforward cancellation methods, exact gain and phase matching are easily obtained in the proposed architecture to produce a highly selective narrowband frequency response at the output of the LNA with wide rejection bandwidth. For the proof of concept, the system is implemented in a 65 nm CMOS technology. It occupies a total area of 0.8 mm² and the current consumption is 24 mA from a 1.2 V supply. The system post-layout simulations showed a blocker rejection of more than 33 dB for blocker signals 100 MHz away from the desired signal when the feedforward path is activated. The noise figure (NF) of the entire system is 3.8 dB that degrades to 5.8 dB when the feedforward path is activated.     

A fully integrated low-IF CMOS GPS radio with on-chip analog image rejection

A fully integrated Global Positioning System (GPS) radio is presented. Low-IF architecture was used for a high level of integration and low power consumption. An on-chip analog image-reject filter provides 18 dB of image-noise rejection to prevent noise figure (NF) degradation. With image rejection performed in the analog radio, a single-path (nonquadrature) output was used. The integrated synthesizer only requires an off-chip phase-locked loop-filter to function. Implemented in a 0.35-/spl mu/m 2P4M CMOS process, the integrated radio has a chip area of 9.5 mm/sup 2/. The radio operates over a wide range of voltage and temperature, from 2.2 to 3.6 V and from -40/spl deg/C to +85/spl deg/C and consumes 27 mW from a 2.2-V supply. The receiver has 4 dB NF.     

实用的调频接收机电路设计

本设计主要由以下三部分组成:一、音芯片CXA1691,它是集调幅、调频、锁相环、立体声解码等电路为一体的AM/FM立体声收音IC.二、相环芯片BU2614,通过合理设计环路滤波器,频率能够稳定在88～108MHz.三、DC-DC变换电路,实现了系统的低功耗和单电源供电.     

Low-noise heterodyne receivers for near-millimeter-wave radio astronomy

Increased interest in the near-millimeter wavelength region, covering the range 3 mm to 300 µm, during the past decade has stimulated the development of sensitive heterodyne receivers for a wide range of applications. This review paper considers current low-noise receiver technology with emphasis on applications in radio astronomy. A brief discussion of the astrophysical importance of radio astronomy at millimeter wavelengths is presented. The concepts of receiver design and the particular problems associated with this region of the spectrum are discussed. The optimization of material parameters and device topology for both Schottky-barrier diodes and superconducting mixer elements is considered. The extension of waveguide mixer technology into the submillimeter region and the development of quasi-optical receivers is reviewed. Consideration is given to the recent development of efficient harmonic generators for local oscillator (LO) applications at near-millimeter wavelengths.     

New mute for land mobile radio receivers

A new mute for mobile radio receivers is described that combines the characteristics of noise and tone mutes. Use is made of a bandstop within the speech passband. Satisfactory muting depends on the appropriate choice of filter band-widths and circuit time constants.     

A soft radio architecture for reconfigurable platforms

While many soft/software radio architectures have been suggested and implemented, there remains a lack of a formal design methodology that can be used to design and implement these radios. This article presents a unified architecture for the design of soft radios on a reconfigurable platform called the layered radio architecture. The layered architecture makes it possible to incorporate all of the features of a software radio while minimizing complexity issues. The layered architecture also enables a methodology for incorporating changes and updates into the system. An example implementation of the layered architecture on actual hardware is presented     

A 1-V 3.5-mW CMOS switched-opamp quadrature IF circuitry for Bluetooth receivers

A 1-V switched-capacitor (SC) quadrature IF circuitry for Bluetooth receivers is demonstrated using switched-opamp technique. To achieve double power efficiency while maintaining low sensitivity to finite opamp gain effects for the SC IF circuitry, half-delay integrator-based filters and /spl Sigma//spl Delta/ modulator have been proposed. The proposed quadrature IF circuitry employs a seventh-order IF filter for channel selection and a third-order /spl Sigma//spl Delta/ modulator for analog-to-digital conversion. A noise-shaping extension technique is employed to enhance the resolution of the low-pass /spl Sigma//spl Delta/ modulator by 16 dB while operating at the same oversampling ratio and power consumption. At a 1-V supply, the quadrature IF circuitry achieves a measured IIP3 of -3 dBm at a nominal gain of 24 dB with a 48-dB variable gain control while consuming a total power dissipation of 3.5 mW.     

A software radio architecture for linear multiuser detection

The integration of multimedia services over wireless channels calls for provision of variable quality of service (QoS) requirements. While radio resource management algorithms (such as power control and call admission control) can provide certain levels of variability in QoS, an alternate approach is to use reconfigurable radio architectures to provide diverse QoS guarantees. We outline a novel reconfigurable architecture for linear multiuser detection, thereby providing a wide range of bit error rate (BER) requirements amongst the constituent receivers of the reconfigurable architecture. Specifically, we focus on achieving this dynamic reconfiguration via a software radio implementation of linear multiuser receivers. Using a unified framework for achieving this reconfiguration, we partition functionality into two core technologies [field programmable gate arrays (FPGA) and digital signal processor (DSP) devices] based on processing speed requirements. We present experimental results on the performance and reconfigurability of the software radio architecture as well as the impact of fixed point arithmetic (due to hardware constraints)     

A novel multi-band OFDMA-PON architecture using signal-to-signal beat interference cancellation receivers based on balanced detection

We have proposed a novel multi-band orthogonal frequency division multiplexing and passive optical network (OFDMA-PON) architecture using signal-to-signal beat interference cancellation receivers based on balanced detection at both the optical line terminal and the optical network units (ONUs). Simulation of the full-duplex system with 20 km SSMF transmission and a 1:4 split is achieved successfully. Without a laser source and amplifier at the ONU, our proposed multi-band OFDMA-PON system reduces the signal-to-signal beat interference simply and effectively, while the space of each band can be as small as 1 GHz and optimum carrier-to-signal power ratio at about 10 dB. Simulation results show that the OSNRs of the 40 Gb/s downstream and 30 Gb/s upstream transmission are only 20 and 16 dB required at \(\hbox {BER}=3.8 \times 10^{-3}\), respectively.     

A novel phase-noise compensation scheme for communication receivers

A novel phase-noise (PHN) compensation method is proposed in this paper. The proposed approach uses the information provided by an additional signal path that is added with modest hardware overhead to better estimate the PHN. In this signal path, the oscillator output is self-downconverted to the baseband by mixing itself with a delayed and conjugated replica, so as to provide PHN information that is free from data modulation. A joint prediction and smoothing Wiener filter can then be employed to obtain the minimum mean-squared error estimate of the PHN. There are generally two types of PHN models commonly used in the literature: stationary PHN and Wiener PHN. Both types of PHN are considered in this paper. Adaptive schemes are also presented using the least-mean square algorithm and recursive least-square algorithm. Simulations of a 64-quadrature amplitude modulation receiver confirm the analysis results of the PHN estimation performance, and show that the proposed method can improve the receiver performance significantly over the conventional schemes.     

Analysis of optical amplifier noise in coherent opticalcommunication systems with optical image rejection receivers

A detailed theoretical analysis of optical amplifier noise in coherent optical communication systems with heterodyne receivers is presented. The analysis quantifies in particular how optical image rejection receiver configurations reduce the influence of optical amplifier noise on system performance. Two types of optical image rejection receivers are investigated: a novel, all-optical configuration and the conventional, microwave-based configuration. The analysis shows that local oscillator-spontaneous emission beat noise (LO-SP), signal-spontaneous emission beat noise (S-SP), and spontaneous-spontaneous beat noise (SP-SP) can all be reduced by 3 dB, thereby doubling the dynamic range of the optical amplifier. A 2.5-dB improvement in dynamic range has been demonstrated experimentally with the all-optical image rejection configuration. The implications of the increased dynamic range thus obtained are also discussed from a systems point of view     

A low-power DSP core-based software radio architecture

This paper describes an approach to developing a low-power digital signal processor (DSP) subsystem architecture for advanced software radio platforms. The architecture is intended to support next-generation wide-band spread-spectrum military waveforms. The methodology illustrates how a next-generation programmable DSP core forms the basis for an application-specific integrated circuit (ASIC). It also shows how semiconductor technologies can be integrated into such chips to achieve algorithm performance while minimizing subsystem power consumption. The ASIC is run-time configurable to maintain high flexibility. The range of RF channel modulation (“waveforms”) and air interfaces is intended to include both wide-band and traditional narrow-band waveforms. Estimated gate counts and power-consumption estimates are presented. DSP circuit-design and power-management strategies necessary to achieve low-power operation are presented. While the architecture discussion focuses on military waveforms, the approach is also applicable to commercial waveforms     

Two-step channel selection technique by programmable digital-double quadrature sampling for complex low-IF receivers

Presents a novel two-step channel selection technique to be adopted in complex low-IF receivers for enhancing the performance and efficiency of the front-end PLL-frequency synthesiser (PLL-FS), which will be mainly implemented by a proposed programmable digital-double quadrature sampling (D-DQS) scheme. Thus, the weaknesses of the PLL-FS in very small step-size operations including long locking time and large phase noise are significantly reduced. Simulation results of the D-DQS scheme are provided to demonstrated the feasibility of such a technique.     

A modular architecture for high resolution image dehazing

Haze is an atmospheric phenomenon which diminishes visibility in outdoor images. Algorithms based on dark channel prior (DCP) and haze line prior are found to be effective for dehazing images. These two methods make use of the Laplacian matrix, which is computationally complex, memory intensive and slow, thus making it impossible to use them on high-resolution (large) images. Multiple strategies have been suggested in the literature to speed up dehazing process by avoiding the Laplacian matrix, but these methods compromise on the quality of dehazing. We propose an effective modular method which divides the input image into blocks and processes each block independently. This makes it possible to use our method for dehazing large images retaining Laplacian matting and thus ensuring the output image quality. This division results in the possibility of assuming local values of atmospheric light. We show that this approach results in better dehazing in the local regions. The effectiveness of the proposed modular architecture is tested also on a learning based method. The output of the modular method is compared with those of different state-of-the-art dehazing methods for multiple quality parameters. Toward this, we have created a dataset of hazy natural outdoor images of large size.