Intermediate Frequency Filter Research Articles

Performance Evaluation of SAW Devices by Simulation

Surface acoustic wave (SAW) devices have been used since theearly 1990s as critical components in many radio frequency (RF)transmitters and receivers due to their small size, efficient operation, and excellent performance characteristics.

Performance Evaluation of Saw Devices by Simulation

Surface acoustic wave (SAW) devices have been used since the early 1990s as critical components in many radio frequency (RF) transmitters and receivers due to their small size, efficient operation, and excellent performance characteristics. In today’s wireless applications, the number of passive SAW components used is on the increase. SAW devices are being used in mobile phones and wireless devices as RF resonator filters, intermediate frequency filters, and local oscillators. In addition, SAW devices have recently been defined and used for sensing various measurands, including gases, liquids, ice, and mechanical vibrations. Because SAW devices are so widely used, it is desirable to evaluate the device prior to fabrication, especially in cases where the devices’ material and dimensions have a major influence on the performance of the overall system. In this article the authors present the frequency response simulation of SAW devices using MATLAB™. Both equivalent circuit and transmission matrices model have been simulated for three different types of SAW devices: a delay line, a one-port resonator, and a two-port resonator. The results obtained are presented along with the design parameters and models used in the simulations.

Electrical and Frequency Characteristics of Third-Overtone Vibration-Mode Surface Mount Device High-Frequency Filter Using Modified PbTiO3 Ceramics

In this study, a 3rd-overtone thickness-vibration-mode surface mount device (SMD) filter was manufactured using modified PbTiO3 system ceramics for application as an intermediate frequency (IF) filter with a split electrode and gap size. To investigate the effects of the split electrode and gap size on the filter characteristics of the 3rd-overtone-mode energy-trapped filter, ceramic wafers were fabricated by etching split rectangular electrodes with sizes (b ×d) of b=0.4, 0.6, 0.8 and 1 mm, d=0.3, 0.4, 0.5 and 0.6 mm and gap sizes (c) of the c=0.2, 0.3, 0.4 and 0.6 mm, respectively. Then, SMD ceramic filters were fabricated with the size of 3.7 ×3.1 mm2. SMD ceramic filter with the size of b=0.8 mm, d=0.4 mm and c=0.4 mm showed insertion loss of 2.951 dB, 3 dB bandwidth of 54.7 kHz and 20 dB stop bandwidth of 129.27 kHz. Also, these two filters were cascaded and their bandwidth characteristics were investigated by varying the coupling capacitance to check their applicability as high frequency band-pass filters. The cascaded filter showed a higher stop band, reduction of spurious response and increase of selectivity. With increasing coupling capacitance, insertion loss increased but spurious response decreased. The cascaded filter with a coupling capacitance of 15 pF showed insertion loss of 5.643 dB, 3 dB bandwidth of 55.089 kHz and 20 dB bandwidth of 83.608 kHz.

An AI-calibrated IF filter: a yield enhancement method with area and power dissipation reductions

We have developed a large-scale integration (LSI) for Gm-C intermediate frequency (IF) filters, attaining a 63% reduction in filter area, a 26% reduction in power dissipation, compared with existing commercial products using the same process technology and filter topology, and a yield rate of 97%. The developed chip is calibrated within a few seconds by a genetic algorithm - an efficient AI technique for difficult optimization problems. Our calibration method, which can be applied to a wide variety of analog circuits, leads to cost reductions and the efficient implementation of analog LSIs.

Very small IF resonator filters using reflection of shear horizontal wave at free edges of substrate

A shear horizontal (SH) wave has the characteristic of complete reflection at the free edges of a substrate with a large dielectric constant. A conventional surface acoustic wave (SAW) resonator filter requires reflectors consisting of numerous grating fingers on both sides of interdigital transducers (IDTs). On the contrary, it is considered that small-sized and low loss resonator filters without reflectors consisting of grating fingers can be realized by exploiting this characteristic of the SH wave or the Bleustein-Gulyaev-Shimizu (BGS) wave. There are two types of resonator filters: transversely coupled and longitudinally coupled. No transversely coupled filters (neither conventional nor edge-reflection) using the SH wave on a single-crystal substrate have been realized until now, because two transverse modes (symmetrical and asymmetrical modes) are not easily coupled. However, the authors have realized small low loss transversely coupled resonator filters in the range of 25 to 52 MHz using edge reflections of the BGS wave on piezoelectric ceramic (PZT: Pb(Zr,Ti)O3) substrates for the first time by developing methods by which the two transverse modes could be coupled. On the other hand, longitudinally coupled resonator filters using edge reflection of the SH or BGS wave always have large spurious responses because of the even modes in the out-of-band range, because the frequencies of even modes do not coincide with the nulls of the frequency spectra of the IDTs. Consequently, longitudinally coupled resonator filters using the edge reflection of the SH wave have not been realized. By developing a method of reducing the spurious responses without increasing of the insertion loss, the authors have realized small low loss longitudinally coupled resonator filters in the range of 40 to 190 MHz using edge reflection of BGS or SH waves on PZT or 36 degrees-rotated-Y X-propagation LiTaO3 substrates for the first time. Despite being intermediate frequency (IF) filters, their package (3 x 3 x 1.03 mm3) sizes are as small as those of radio frequency (RF) SAW filters.

Evolvable analog LSIs: Adaptation to process variations via genetic algorithms

AbstractWe propose a concept of evolvable analog LSIs and apply it to Intermediate Frequency (IF) filters, which are widely used in cellular phones. The developed chip can correct discrepancies in the values of analog circuit components by genetic algorithms (GAs), which have attained (1) a yield rate of 97%, (2) a 60% reduction of the filter area, and (3) a 38% reduction of power dissipation, compared with AKM commercial products. When analog Integrated Circuits (ICs) and Large‐Scale Integrated Circuits (LSIs) are manufactured, the values of the analog circuit components, such as resistors or capacitors, often vary from the precise design specifications. Analog LSIs with such defective components cannot perform at required levels and thus have to be discarded. However, our technique can improve yield rates of analog LSIs and has two additional advantages, namely, smaller circuits and less power dissipation, which can lead to cost reductions and efficient implementation of analog LSIs. This approach could be applied to a wide variety of analog LSIs. © 2001 Scripta Technica, Electr Eng Jpn, 138(3): 63–71, 2002

Design of a selective digital filter using the decimation technique

The implementation of an Intermediate Frequency (IF) filter in Digital Audio-VIsual Council (DAVIC) compliant modems is a particularly complex task. In previous works, we compared the performance of different designs (analog and digital) for the radio-frequency stage in a modem application. These designs have been evaluated for a particular case defined in the DAVIC recommendation. The design limits that were pointed out are mainly due, in the digital approach, to the high frequencies at which the IF stage must operate, and to the variation of the sampling frequency.In this paper, we propose a digital implementation of the IF filter based on the decimation technique. The evaluation of the performance has been performed using the PTOLEMY software from the Berkeley University.

Longitudinally Coupled Resonator Filter Using Edge Reflection of Bleustein-Gulyaev-Shimizu and Shear Horizontal Waves with Various Bandwidths Realized by Selecting Substrates

A conventional surface acoustic wave (SAW) resonator filter requires reflectors with many grating fingers at both sides of the interdigital transducers (IDTs). On the other hand, a small-sized low-loss resonator filter without grating fingers can be realized by utilizing the reflection of a Bleustein-Gulyaev-Shimizu (BGS) wave or a shear horizontal (SH) wave at the edge of a substrate. As a result, the authors have developed longitudinally coupled resonator filters using the reflection of BGS and SH waves at the edges of a substrate. Longitudinally coupled resonator filters on piezoelectric ceramic substrates for the first intermediate frequency (IF) stage have been realized to be low-loss, small-sized and extremely wide bandwidth (fractional bandwidth of 15%) filters as compared to the ordinary resonator filters, and they can have various kinds of bandwidths (2 to 15%) by employing ceramic substrates with various electromechanical coupling factors. On the other hand, the edge-reflection-type resonator filters on LiTaO3 single crystal for various first IF stages have also been realized to be low-loss and small-sized filters. In spite of being a wire-bonding type of IF filter, the package size of this filter is the same as that of the radio frequency (RF) SAW filter.

High-Q HF microelectromechanical filters

IC-compatible microelectromechanical intermediate frequency filters using integrated resonators with Q's in the thousands to achieve filter Q's in the hundreds have been demonstrated using a polysilicon surface micromachining technology. These filters are composed of two clamped-clamped beam micromechanical resonators coupled by a soft flexural-mode mechanical spring. The center frequency of a given filter is determined by the resonance frequency of the constituent resonators, while the bandwidth is determined by the coupling spring dimensions and its location between the resonators. Quarter-wavelength coupling is required on this microscale to alleviate mass loading effects caused by similar resonator and coupler dimensions. Despite constraints arising from quarter-wavelength design, a range of percent bandwidths is still attainable by taking advantage of low-velocity spring attachment locations. A complete design procedure is presented in which electromechanical analogies are used to model the mechanical device via equivalent electrical circuits. Filter center frequencies around 8 MHz with Q's from 40 to 450 (i.e., percent bandwidths from 0.23 to 2.5%), associated insertion losses less than 2 dB, and spurious-free dynamic ranges around 78 dB are demonstrated using low-velocity designs with input and output termination resistances of the order of 12 k/spl Omega/.

A 71-MHz CMOS IF-baseband strip for GSM

An intermediate-frequency (IF) baseband strip for a superheterodyne GSM receiver developed in a 0.25-/spl mu/m CMOS technology is presented. It contains a 71-MHz IF amplifier, programmable between -20 and +60 dB in 2-dB steps; a quadrature demodulator; and two low-pass output filters for channel selection. Measurements show an overall maximum gain of 89 dB and a noise figure of 3.8 dB. Phase and amplitude mismatches of the demodulator are below 10 and 0.1 dB, respectively. The high linearity required by the blocking and intermodulating signals, which are not completely suppressed by the IF filter, has been achieved using 4.7 mA from the 2,5-V power supply.

Steering of an optically driven true-time delay phased-array antenna based on a broad-band coherent WDM architecture

Performance of a six-channel (delay) three-antenna element coherent optically driven phased-array antenna which transports true-time delays from the controller to the antenna site over 4.4 km of single-mode fiber (SMF) are presented. We demonstrate accurate true-time delay and beam steering from 0.8-1.5 GHz. Wide bandwidth intermediate frequency (IF) filters are used to minimize the phase-to-intensity noise, resulting in a single-channel signal-to-noise ratio (SNR) and dynamic range of 49 (dB-MHz) and 94 (dB-Hz)/sup 2/3/, respectively. Additionally, using up-conversion at the antenna site, true-time delays at frequencies up to 18.3 GHz are demonstrated.

TE Harmonic Overtone Mode Energy-Trapped Ceramic Filter with Narrow Frequency Tolerance

Experimental studies have been made on the suppression of two major spurious responses, i.e., inharmonic overtones and the 6th thickness-shear-mode harmonic overtone, to realize a 3rd overtone thickness-extension double-mode bandpass filter using PbTiO3 ceramic substrates. Each leverage was found by investiging of low-symmetry electrode shapes and implementing the nonpolarized portion of the region between terminal pads on the piezoelectric substrate. The practical importance of the application of intermediate-frequency filters (IF filters) used in wireless communication systems depends on how the narrow frequency tolerance requirement is satisfied. A simple but accurate method of adjusting the center frequency of these filters is shown here.

A custom digital intermediate frequency filter for the American mobile telephone system

A digital filter for intermediate frequency filtering in mobile communication systems is presented. The purpose of the work is to show an alternative to the analog filters which are used in most of today's heterodyne receivers. Bit-serial arithmetic is applied on a twelfth-order wave digital lattice filter algorithm. The paper also shows a method for retiming such algorithms. The power consumption in two fabricated prototypes is compared. By customizing the library cells, the power consumption has been reduced significantly. In the low power prototype, the power dissipation is 8 mW using 3 V supply voltage. The prototype is a 10 MIPS design fabricated in a 0.8-/spl mu/m standard two-metal-layer CMOS process.

Phase noise in coherent analog AM-WIRNA optical links

Coherent analog amplitude modulated-wideband rectifier narrowband (AM-WIRNA) systems have been the focus of many recent studies because of their high performance and relative immunity to phase noise compared to angle modulated systems. Despite their natural advantages over angle modulated systems, AM-WIRNA receivers are still vulnerable to phase noise because of distortion of their phase broadened signals in a finite bandwidth system. We present the first numerical analysis of the effects of this distortion on the performance of AM-WIRNA systems. The analysis accurately models the power spectral density of the phase-to-intensity noise with a root-mean-square deviation from the averaged experimental noise spectrum of 1.2 dB and a maximum deviation of 3.8 dB in the modulation range of <2 GHz. The accuracy of the analysis is limited primarily by nonidealities in the AM-WIRNA receiver and the accuracy of the analytical intermediate frequency (IF) filter model. Optimal link designs are presented which minimize the impact of phase-to-distortion noise in AM-WIRNA systems. We present experimental data from AM-WIRNA links which use both external cavity and distributed feedback lasers for the signal and local oscillator sources. The numerical analysis predicts the link signal-to-noise ratio (SNR) for different signal laser powers to within 1.4 dB of experiment. We find that systems requiring high SNR such as phased array antennas and AM-CATV are significantly affected by this noise.

Performance of coherent ASK lightwave systems with finite intermediate frequency

The impact of finite intermediate frequency (IF) on the performance of heterodyne ASK lightwave systems is examined and quantified in the presence of laser phase noise and shot noise. For negligible linewidths, it is shown that certain finite choices of IF (R/sub b/,3R/sub b//2,2R/sub b/,5R/sub b//2, etc.) lead to the same ideal bit-error-rate (BER) performance as infinite choices of IF. Results indicate that for negligible linewidths the worst case sensitivity penalty is 0.9 dB for proper heterodyne detection and occurs when f/sub IF/=1.25 R/sub b/. For nonnegligible linewidths (e.g., when /spl Delta//spl nu/T/spl ges/0.04) the sensitivity penalty is always less than 0.9 dB for finite choices of IF. The analysis presented does lead to a closed-form signal-to-noise ratio (SNR) expression at the decision gate of the receiver which can readily be used for BER and sensitivity penalty computations. The SNR expression provided includes all the key system parameters of interest such as system bit rate (R/sub b/), the peak IF SNR (/spl xi/), laser linewidth (/spl Delta//spl nu/), and the IF filter expansion factor (/spl alpha/). The findings of this work suggest that the number of channels in a multichannel heterodyne ASK lightwave system can be increased substantially by properly choosing a small value for the IF at the expense of a small penalty <1 dB. On the negative side, IF frequency stabilization becomes a more critical requirement in multichannel systems employing small values of IF.

An AM/TV/FM stereo radio IC including IF filters for a DTS

A single-chip AM/TV/FM stereo radio IC including IF (intermediate frequency) filters for a digital tuning system has been developed. The IF filter center frequency is controlled by new low-noise, low-distortion equivalent resistor circuits. Even though the value of resistors varies naturally, the center frequency can be fixed. Consequently, a radio IC including IF filters can be used for a DTS (digital tuning system), and peripheral components and production costs are reduced.

On diversity reception of narrow-band 16 STAR-QAM in fast Rician fading

An expression for the bit-error rate (BER) of 16 STAR-quadrature amplitude modulation (QAM) with differential encoding and detection in a Rician fading channel with diversity reception is obtained. Two types of intermediate frequency (IF) filters are considered in the analysis: the intersymbol interference (ISI)-free matched and nonISI-free Gaussian filters. BER curves for various ratios of the line-of-sight (LOS) power to the multipath power, Doppler spread frequencies, and orders of diversity are presented. It is shown that 16 STAR-QAM outperforms 16 DPSK under the same power-limited condition. For the Gaussian receive filter, a filter bandwidth of about 1.2 times the symbol rate is found to lead to a minimum error probability prior to the appearance of error-rate floors.

Performance Evaluation of ASK Multichannel Coherent Optical Systems

AbstractIn this work we evaluate the impairments due to laser phase noise in multichannel coherent optical systems using a heterodyne ASK modulation scheme. The effects of crosstalk due to a finite value of the channel spacing are considered in a system employing a frequency division multiplexing technique. The phase noise and the frequency spacing between adjacent channels are the fundamental parameters which determine the design criteria (e.g. the bandwidth of the intermediate frequency filters) and the performance of the receiver. The accurate statistical characterization of the filtered phase noise and of the crosstalk is the key to get accurate results: to this aim the exact moments of the random processes related to the phase noise and to the crosstalk interference are used together with a Gaussian Quadrature Rule for the evaluation of the error probability.

Advanced low voltage single chip radio IC

A complete single chip radio IC technology is discussed. It was possible to include intermediate frequency (IF) filters in a radio IC by reducing the IF. Degradation of image interference characteristics can be avoided by image canceling circuits with inphase/quadrature mixers and a phase shift network. Two ICs were developed for FM-stereo/AM and AM-only radio by using this technology. The FM-stereo/AM radio IC can work at a supply voltage of 0.95-V. >

Finite intermediate frequency penalty in optical PSK synchronous heterodyne receivers

System performance degradation due to the finite intermediate frequency (IF) is analyzed for an optical PSK (phase shift keying) synchronous heterodyne receiver. Analysis of the finite IF includes the effect of both the IF and the postdetection filtering. The theoretical study reveals that when the IF center frequency is set at f/sub IF/=2/T(T=bit time) and the IF filter bandwidth is adjusted to be 2f/sub B/=2/T, the finite IF introduces 0.2 and 0 dB sensitivity penalties for single- and two-pole baseband filters, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>