Intermediate Frequency Filter Research Articles

Integrated high-inductance three-dimensional toroidal inductors

Fabrication, characterizations, and modeling of three-dimensional high-inductance value toroidal inductors are presented. The effect of substrate and number of turns on toroidal inductors with 16, 31, and 62 turn fabricated using prestressed metals are investigated. A 62-turn inductor on high-resistivity Si substrate has an inductance value of 81 nH, a self-resonance frequency of ∼2 GHz, and a peak quality factor (Q) of ∼10. It is found that the substrate loss is detrimental to the quality factor of toroidal inductors at high frequencies and should be suppressed by using high-resistivity substrate or SU-8 coated Si substrate in order to obtain high values of the quality factor. In addition, reducing turn-to-turn gap in toroidal inductors results in higher mutual couplings among the inductor turns and thus achieving high-inductance values. Integrated high-inductance value, high-Q inductors can be used in integrated switching power supplies, radio frequency (rf) and intermediate frequency filters, energy conversion circuits, and as on-chip rf chokes in rf integrated circuits.

A Double Inequality for the Equivalent Impulse Bandwidth

In this paper, we derive a double inequality that permits one to obtain a lower and an upper limit for the value of the impulse bandwidth of a measuring receiver. The limits are the reciprocal of the integral of the relative envelope of the impulse response (lower limit) and the integral of the relative frequency response (upper limit) of the intermediate frequency (IF) filter. Since the limits are relative quantities, their evaluation does not require the use of a calibrated generator, the only significant sources of error being receiver's vertical scale nonlinearity and noise proximity. Here, the deviation between the impulse bandwidth and its limits is quantified for practical IF filter configurations. The dominant contributions to measurement uncertainty are identified and suggestions for reducing their magnitude are also offered.

Guided acoustic wave resonators using an acoustic Bragg mirror

Lamb wave devices have recently gained an interest for providing narrow bandpass filters in wireless transmission systems. Their cointegration with film bulk acoustic wave resonators is a major advantage, enabling the possibility to provide simultaneously several radio frequency and intermediate-frequency filters in a single fabrication. Similarly, in this work, we report the fabrication of resonators using waves guided in a piezoelectric layer deposited atop a Bragg mirror. Such waves exhibit a behavior close to Lamb waves, thanks to the acoustic isolation provided by the mirror, while being cointegrated along with solidly mounted resonator structures.

A Novel Diversity-Controlled Genetic Algorithm for Optimization of BIBO Stable Digital IF Filters Over CSD Multiplier Coefficient Space

This paper presents a novel diversity-controlled (DC) genetic algorithm (GA) for the optimization of digital Intermediate Frequency (IF) filters over the (finite-precision) canonical signed-digit (CSD) multiplier coefficient space. This optimization exploits the bilinear-lossless-discrete- integrator (bilinear-LDI) lattice digital filter design approach for the realization of the required infinite-precision seed digital IF filter chromosome. A look-up table (LUT) approach is proposed to ensure that the finite-precision CSD digital IF filter chromosomes generated in the course of DCGA optimization are guaranteed to be bounded-input bounded-output (BIBO) stable. The salient feature of DCGA optimization is that it permits external control over the population diversity (i.e. the parent selection pressure) to achieve a high convergence speed. This feature is illustrated through the application of the proposed DCGA optimization to the design of a pair of practical digital IF filters satisfying different design specifications. It is observed that, for both digital IF filter designs, the DCGA optimization results in around an order of magnitude improvement in the convergence speed as compared to a conventional GA optimization.

A correlation electron cyclotron emission diagnostic and the importance of multifield fluctuation measurements for testing nonlinear gyrokinetic turbulence simulations

A correlation electron cyclotron emission (CECE) diagnostic has been used to measure local, turbulent fluctuations of the electron temperature in the core of DIII-D plasmas. This paper describes the hardware and testing of the CECE diagnostic and highlights the importance of measurements of multifield fluctuation profiles for the testing and validation of nonlinear gyrokinetic codes. The process of testing and validating such codes is critical for extrapolation to next-step fusion devices. For the first time, the radial profiles of electron temperature and density fluctuations are compared to nonlinear gyrokinetic simulations. The CECE diagnostic at DIII-D uses correlation radiometry to measure the rms amplitude and spectrum of the electron temperature fluctuations. Gaussian optics are used to produce a poloidal spot size with w(o) approximately 1.75 cm in the plasma. The intermediate frequency filters and the natural linewidth of the EC emission determine the radial resolution of the CECE diagnostic, which can be less than 1 cm. Wavenumbers resolved by the CECE diagnostic are k(theta) < or = 1.8 cm(-1) and k(r) < or = 4 cm(-1), relevant for studies of long-wavelength turbulence associated with the trapped electron mode and the ion temperature gradient mode. In neutral beam heated L-mode plasmas, core electron temperature fluctuations in the region 0.5 < r/a < 0.9, increase with radius from approximately 0.5% to approximately 2%, similar to density fluctuations that are measured simultaneously with beam emission spectroscopy. After incorporating "synthetic diagnostics" to effectively filter the code output, the simulations reproduce the characteristics of the turbulence and transport at one radial location r/a = 0.5, but not at a second location, r/a = 0.75. These results illustrate that measurements of the profiles of multiple fluctuating fields can provide a significant constraint on the turbulence models employed by the code.

Receiver Front-End Circuits for Future Generations of Wireless Communications

In this paper, new receiver concepts and CMOS circuits for future wireless communications applications are introduced. The concepts derived are applied to a few classes of wireless communications standards that are broad-band at radio frequencies and/or require a broad-band baseband circuitry. Multimode multiband operation and adaptivity as key requirements for future generation receivers are highlighted throughout the paper. The tradeoffs between power consumption, noise figure and linearity performance of low-noise amplifiers, mixers, and intermediate frequency filters are considered too.

A method for restoration of radio channel transfer function by chirp sounding of the ionosphere

[1] Analysis of both in-phase and quadrature components of received frequency-modulated continuous wave (FMCW) signal at the output of intermediate frequency (IF) band-pass filter of the chirp ionosonde demonstrates a new possibility of recovering the transfer function of the HF radio channel within the band of operating frequencies and the interval of time delays that are defined by the IF filter characteristics. The transfer function is determined by the parameters of all parts comprising the radio channel: transmitter, receiving-transmitting antenna-feeder devices, Earth surface, ionosphere, as well as the receiver circuitry participating in the signal processing. However, characteristics of all parts except the ionosphere can be considered stationary and well-known or controlled. It is the ionosphere that displays significant temporal variability. A new technique is proposed for recovering the transfer function of the ionospheric radio channel, together with its implementation as a signal preprocessing circuit containing a correcting digital filter that adapts to the current amplitude frequency and phase frequency characteristics of the channel. INDEX TERMS: 2441 Ionosphere: Ionospheric storms; 2407 Ionosphere: Auroral ionosphere; 2447 Ionosphere: Modeling and forecasting; KEYWORDS: FMCW sounder, chirp sounding technique, ionospheric radio channel, transfer function, digital signal processing.

Estimation of Aliasing Effects Due to Periodical Nonuniform Individual Sampling in High-&lt;emphasis&gt;Q&lt;/emphasis&gt; Switched-Capacitor Filters

The periodical nonuniform individual sampling scheme has been shown suitable for capacitance spread and total capacitor area reduction in high quality (Q) factor switched-capacitor (SC) filters. However, the use of periodical nonuniform clock signals results in additional aliasing components in the output spectrum. This paper presents a simple model to analyze the generation of such alias components and gives practical expressions to estimate their power. The results are verified through circuit simulation of a 10.7-MHz second-order SC bandpass filter in a 0.35-mum CMOS technology. Implications on the use of this technique in the design of intermediate-frequency filters are discussed

CMOS low-power bandpass IF filter for Bluetooth

Design of a CMOS 18th-order IF (intermediate frequency) bandpass filter for integrated low-IF Bluetooth receivers is presented. The centre frequency and bandwidth of the filter are 3 and 1 MHz, respectively. The proposed filter is based on unity gain fully differential voltage buffers and provides efficient, low power and a small area design solution. The filter, including its automatic tuning circuit, occupies an area of 0.6 mm2 in a standard 0.5 µm-CMOS chip. Experimental results show that the filter satisfies the selectivity and dynamic range requirements of Bluetooth while operating from a total supply current of 0.9 mA.

Effect of Sampling Frequency on GNSS Receiver Performance

ABSTRACT: This paper investigates the effect of the sampling frequency on Global Navigation Satellite System (GNSS) receiver performance. Modern digital navigation receivers sample the analog signal at the output of the Intermediate Frequency (IF) filter and implement digital tracking loops. The synchronization of the incoming and local code, fundamental to compute the user's position, is an alignment between two discrete sequences. It is important to recognize that certain relationships between sampling and code rates can result in an accuracy degradation. Although this aspect is understood within a select group within the receiver design community, this paper attempts to present and quantify the impact for a broader audience. Further, commercial vendors have continued to propose such architectures with a sampling frequency that is a multiple of the nominal code rate. This paper demonstrates the impact on the correlation function and pseudorange measurement using variations on the sampling frequency with real data.

Impact of frequency offsets and IQ imbalance on MC-CDMA reception based on channel tracking

New air interfaces are currently being developed to meet the high spectral efficiency requirements of the emerging wireless communication systems. Multicarrier code-division multiple access (MC-CDMA) is seen as a promising candidate for the fourth-generation (4G) cellular communication systems because it can interestingly deal with the multipath propagation at a low processing complexity. Besides spectral efficiency and power consumption, the production cost of the transceiver should also be optimized. Direct conversion radio frequency (RF) receivers are appealing because they avoid costly intermediate frequency (IF) filters. However, they imply RF IQ separation, introducing a phase and amplitude mismatch between the I and Q branches. A communication system based on MC-CDMA is sensitive to synchronization errors and front-end non-idealities because it uses a long symbol duration. The goal of this paper is to evaluate the impact of the carrier frequency offset, the sampling clock offset, and the IQ imbalance on the MC-CDMA downlink system performance, considering a receiver based on channel tracking designed to cope with high mobility conditions. It is demonstrated that part of the effects is compensated by the channel estimation and an expression of the variance of the remaining symbol estimation error is provided. For the cellular system and the target performance considered in this paper, specifications are defined on the non-idealities. The results are validated with bit-error rate simulations

Solving phase-noise Fokker-Planck equations using the motion-group Fourier transform

A quantity of importance in coherent optical communications is the probability density of a filtered signal in the presence of phase noise (PN). The Fokker-Planck(FP) approach has been recognized as a rigorous way to describe these statistical properties. However, computational difficulties in solving these FP equation shave prevented their widespread application. In this paper, we present a new and simple computational solution method based on techniques from noncommutative harmonic analysis on motion groups. This proposed method can easily solve all the PN FP equations with any kind of intermediate frequency filter. We also present a new derivation of PN FP equations from the viewpoint of stochastic processes.

A New Configuration of Surface Acoustic Wave Intermediate-Frequency Filter with Compact Size and Improved Insertion Loss

Size reduction is always a major challenge to surface acoustic wave (SAW) manufacturers. For some years, commercial SAW filter designers have been developing various configurations of SAW filters just to fit into a smaller package. In this work, a new single-phase unidirectional transducer (SPUDT) based intermediate-frequency (IF) filter with improved insertion loss and compact size is proposed. This filter has an architecture that combines electrode-width controlled single-phase unidirectional transducer (EWC-SPUDT) and comb-type SPUDT. As a result of this improvement, a filter for IF-filtering of Digital European Cordless Telephone (DECT) system can be squeezed into a surface-mount device (SMD) 7.0×5.0 mm2 package. The performance of this filter even excels most commercial available IF filters in the same application.

Novel MEMS filters for on-chip transceiver architecture, modeling and experiments

MEMS-based mechanical resonators and filters have shown promising characteristics in achieving high-Q values and good stability. In this paper, new designs for IC-compatible microelectromechanical intermediate frequency (IF) filters are introduced. These filters have been fabricated and tested and experimental results are included in this work. One of the novel filters is composed of two-cantilever beam resonators coupled by a soft flexural-mode beam. Different configurations of these filters and their RF simulation and experimental responses are presented. One of the advantages of these filters is that the coupling elements can be added from more than one side in order to have elliptical responses. We also introduce a novel V-shaped coupling element that is used to mechanically couple two clamped–clamped MEMS resonators laterally. The stiffness of the proposed V-shaped coupling element is adjustable via changing the length of the V sidelines and/or the V conjunction angle to flatten the filter passband. A two-pole bandpass filter operating in the IF range is constructed using these coupling elements. A lumped modeling approach is presented for fast and accurate filter design and optimization. Using finite-element (FE) analysis, the validity and accuracy of the lumped model are investigated. The fabricated filters have center frequencies varying from 700 kHz to 1.7 MHz, with quality factors of 300–1500 when tested at ambient pressure. The experimental results are presented and compared with lumped and finite-element simulation results.

Micromechanical resonators and filters for microelectromechanical system applications

Microelectromechanical system (MEMS) based mechanical resonators and filters have shown promising characteristics in achieving high Q values and good stability. In this article, new designs for integrated circuit–compatible microelectromechanical intermediate frequency (IF) filters are introduced. These filters have been fabricated and tested, and experimental results are included in this work. One of the novel filters is composed of two-cantilever beam resonators coupled by a soft flexural-mode beam. Different configurations of these filters and their (RF) simulation and experimental responses are presented. One of the advantages of these filters is that the coupling elements can be added from more than one side in order to have elliptical responses. The authors also introduce a novel V-shape coupling element that is used to mechanically couple two clamped-clamped MEMS resonators laterally. The stiffness of the proposed V-shape coupling element is adjustable via changing the length of the V sidelines and...

Third-order intermodulation in a micromechanical thermal mixer

A radio frequency (RF) micromechanical shell-type resonator with a resistive thermal actuator is shown to perform as a highly linear, broadband mixer and a high-quality factor post-translation (intermediate frequency) filter. The resistor is capable of frequency translation of RF carrier signals as high as 1.5 GHz to the intermediate frequency of 12.7 MHz. The thermal actuator allows electrical isolation between the input and output of the mixer-filter, dc bias independent mixing, and provides a 50-Ohm load to match the output of front-end electronics. High linearity is demonstrated in the mixer with a third-order input intercept point of +30 dBm for interferers spaced at a 50-kHz offset from the carrier frequency. A variant of the Duffing oscillator model and finite element modeling are used to analyze the origin of nonlinearities in the micromechanical system. [1503].

A technique to improve the performance of serial, matched-filter acquisition in direct-sequence spread-spectrum packet radio communications

In this paper, we examine a simple method to improve the performance of serial, matched-filter acquisition in direct-sequence spread-spectrum packet radio communications. Each packet transmission includes an acquisition preamble, and the preamble sequence is changed at the boundaries of predefined time epochs based on a pseudorandom sequence generator. It is shown in previous work that the presence of an intermediate-frequency filter and the characteristics of the automatic gain-control subsystem lead to a probability of not acquiring that is a nonmonotonic function of the signal-to-noise ratio if the acquisition algorithm uses a threshold-crossing detector with a fixed threshold. The acquisition algorithm presented in this paper employs an estimator to adaptively select the acquisition threshold for each test statistic. It is shown that this technique reduces the severity of the nonmonotonicity and substantially improves the acquisition performance.

Improved Digital-IF Transmitter Architecture for Highly Integrated W-CDMA Mobile Terminals

An improved digital intermediate frequency (IF) transmitter architecture for wide-band code-division multiple-access (W-CDMA) mobile terminals is proposed. Based on the heterodyne design but without requiring any off-chip IF filter, the transmitter enjoys the advantages of a homodyne architecture (such as circuit simplicity, low power consumption, and a high level of integration) while avoiding the performance problems associated with direct upconversion. By implementing the quadrature modulation in the digital domain and requiring only a single path of analog baseband circuits, inherently perfect I/Q matching and good error vector magnitude (EVM) performance can be achieved. The IF is chosen to be a quarter of the clock rate for a very simple and low-power digital modulator design. The difficulties of on-chip IF filtering were greatly alleviated by 1) performing a careful frequency planning and 2) employing a special-purpose digital-to-analog converter to produce high-order sin(x)/x rolloff. System-level simulation demonstrates that spurious-emission requirements are met with virtually no dedicated reconstruction filter circuits. This architecture takes full advantage of complimentary metal-oxide-semiconductor technology scaling by employing digital processing to ease analog complexities.

Pipelined CORDIC-Based State-Space Orthogonal Recursive Digital Filters Using Matrix Look-Ahead

Orthogonal recursive or infinite impulse response (IIR) digital filters can achieve a sharp transition band, have good finite word-length behavior, and are used in many modern digital signal processing (DSP) applications such as mobile communications. However, Givens rotation or coordinate rotation digital computer (CORDIC)-based fine-grain pipelined true orthogonal recursive digital filters have yet to be developed. In this paper, a state-space approach-based novel algorithm for designing fine-grain pipelined true orthogonal recursive digital filters is proposed using the matrix look-ahead technique. The algorithm is developed for designing general multi-input/multi-output (MIMO) digital filters, whereas the single-input/single-output (SISO) filters are treated as special cases. The filter synthesis procedure contains five major steps and only involves applying orthogonal transformations that are known to be numerically very reliable and, therefore, is ideal for very large scale integration (VLSI) implementations. The proposed filter architectures are pipelined at fine-grain level and, thus, can be operated at arbitrarily high sample rates. The total complexity is MN(m+p)+(m+N)p+p(p-1)/2 Givens rotations for MIMO filters, where N, m, p, and M are the filter order, number of inputs, number of outputs, and pipelining level, respectively. For the SISO case, the complexity reduces to (2M+1)N+1 Givens rotations, which is linear with respect to the filter order and pipelining level. Furthermore, the filter realizations consist of only Givens rotations, which can be mapped onto CORDIC arithmetic-based processors. Different filter design and realization approaches are explored, and the resulting topologies are compared. As an application, a pipelined intermediate frequency filter for an American mobile telephone system is designed using the proposed approach. Finally, finite word-length simulations are carried out for various orthogonal topologies. It is shown both theoretically and numerically how the proposed orthogonal filter realizations achieve low sensitivity due to finite word-length truncations.

Small and low-loss IF SAW filters using zinc oxide film on quartz substrate

It was previously reported that a Rayleigh wave propagating on a zinc oxide film (ZnO)/ST-cut 35 degrees X propagation quartz substrate structure has the characteristics of an excellent temperature coefficient of frequency (TCF) and a large electromechanical coupling factor k(s). This substrate was applied to various intermediate-frequency (IF) stage filters. During the filter development, it was clarified that a spurious response due to the Love wave was generated. In this study, a new quartz substrate has been developed with a specific cut and propagation angle, that has the same values of the TCF and the coupling factor as the above-mentioned ones. In addition, it does not have the spurious response due to the Love wave. The combination of this specific-cut-angle quartz and ZnO film has been applied to IF filters for wideband code division multiple access (W-CDMA) and narrow-band CDMA (N-CDMA) systems. The insertion losses of their IF filters were 3-5 dB better and their TCF was superior (deltaf/f = 0.37 ppm/degrees C: one-third) compared with the conventional surface acoustic wave (SAW) filters.