Intermediate Frequency Filter Research Articles

VHF RADIO PATH WITH INTERMEDIATE FREQUENCY FILTER AND FREQUENCY DETECTOR ON SURFACE ACOUSTIC WAVES

The article applies a new approach to microminiaturization of the VHF radio path with a significant improvement of its main characteristics based on acoustoelectronic elements on SAW. In particular, instead of the intermediate frequency filter (IF), which in most cases is implemented with the help of "coil " products (LC circuits), the CSF (concentrated selection filter) is proposed to be a filter on the characteristic curve, and instead of the same traditional frequency detector (FD) – a FD with by a phase-shifting delay line (DL). Both SAW devices are integrated into the VHF radio path, the main characteristics of the path are given.

Improving the Performance of Direct-Conversion SDRs for Radiated Precompliance Measurements

In this letter, a highly linear front end to improve the performance of software-defined radio (SDRs) for radiated precompliance measurements is presented. In CISPR band C/D, the test receiver needs to fulfill stringent requirements for using the quasi-peak detector. Usually, an expensive preselection filter bank is necessary to make fully compliant measurements of broadband transients. Direct-conversion-based SDRs show a limited out-of-the-box performance for precompliance measurements caused by, e.g., harmonic mixing and saturation effects. With the use of a triple-balanced mixer, a highly linear upconversion stage is built, eliminating the need for a filter bank. The dynamic range (DR) requirements for the SDR are strongly reduced by a narrowband intermediate frequency filter, making CISPR 16-1-1 compliant measurements possible. The sensitivity of the front end is comparable to professional receivers on the market, although no low-noise amplifier is implemented. The performance is verified by continuous wave (CW) and transient signals according to CISPR norms. The broadband measurement results are compared with traditional characterizations of the DR using the compression level and the noise figure. It shows that assumptions on the RF-link budget for a compliant design can be made with CW measurements. Based on our results, the requirements for the SDR front end are derived.

A 90‐ to 115‐GHz superheterodyne receiver front‐end for W‐band imaging system in 28‐nm complementary metal‐oxide‐semiconductor

SummaryIn this paper, a broadband superheterodyne receiver (RX) front‐end for millimeter‐wave (mm‐Wave) imaging radar is presented. Realized in 28‐nm CMOS technology, the proposed RX incorporates a wideband low‐noise amplifier (LNA), double‐balanced passive mixers for the dual down‐conversion, a differential power divider, a differential intermediate frequency filters, a current‐mode‐logic divider‐by‐2, and a local oscillator buffers. Wideband technique and layout optimization are taken into consideration in the RX. A four‐stage LNA is devised to realize the high gain and low noise figure (NF) with a common‐gate input stage and three pseudodifferential common‐source stages. Optimized transistor layout and capacitor neutralization technique are developed to improve gain and noise performance. Transformer‐based matching networks with the peak‐staggered technique are adopted in the LNA to achieve a flatter gain response with a wider bandwidth (BW). The passive double‐balanced mixers are implemented with a highly symmetrical layout for broadband down‐conversion. Simulation results show that the mm‐Wave RX front‐end exhibits a BW ranging from 90 to 115 GHz. The simulated NF of our RX is 4.7 dB at 86 GHz. With a supply voltage of 1 V, the presented RX consumes 88.2‐mW power and occupies a chip size of 1.6 × 0.5 mm2 including all the testing pads. The proposed RX is suitable for W‐band imaging systems.

Mechanically coupled clamped circular plate resonators: modeling, design and experimental verification

Mechanically coupled resonators usually require a mechanical coupling element; this introduces additional complexity to the picture. We propose a novel modeling and design approach, followed by experimental verification, for mechanically coupled clamped circular plate resonators in which no additional coupling element is present. In our study, the flexural mode clamped circular plate resonators overlap to an extent, and their clamps at the overlap region are removed to generate a freely moving coupling boundary between the resonators. The practical measure of the overlapping is small enough to preserve the characteristics of each resonator. This result enables modeling the coupled resonators based on the clamped circular plate resonator model. A physics-based lumped element equivalent circuit model is developed where dimensions, bias voltage, and material properties are controllable variables. Each of the model parameters is expressed as the corresponding single resonator model parameter multiplied by a function of the amount of overlap. Analytical derivations and finite element method simulations are used to extract the dependency of the model parameters on the amount of overlap. Closed-form expressions for center frequency, bandwidth, and termination impedance of the coupled resonator are derived using the developed model. A design procedure is introduced to determine dimensional parameters and bias voltage. The proposed coupled-resonator offers up to 5% fractional bandwidth. For a typical design using a polysilicon plate with 100 nm gap height, the ratio of the termination impedance to the center frequency is calculated to be 158 Ω MHz−1. This result indicates that on-chip intermediate frequency filters can be implemented at center frequencies up to several 100 MHz using this type of coupled resonators. A coupled resonator is designed and realized for a proof of concept demonstration. The measurement results of the coupled resonator show good agreement with the equivalent circuit model simulations.

Compact bandwidth tunable IF filters for reconfigurable converters

AbstractThis paper aims to present some outcomes from a European Space Agency (ESA) Technology Research Programme (TRP) project on R&D of new design techniques, concepts, and filtering configurations for tunable IF (intermediate frequency) filters with a compact footprint, wide bandwidth tuning range (covering from 49 to 478 MHz at f0 = 1 GHz) as well as equivalent high-Q performance (i.e. low insertion loss variation and high selectivity by using low-Q resonators). In order to obtain a wide tuning range, the proposed filtering configuration utilizes a new tuning technique that only necessitates control of coupling values with simple DC control circuits, without the need of tuning the electrical length of resonators to avoid deviating the center frequency. Furthermore, in order to achieve the equivalent high-Q performance, a novel lossy technique by using a centrally resistor-loaded half-wavelength resonator is adopted. For the proof of concept, a six-pole prototype filter is designed, fabricated, and tested.

Extraction of Common-Mode Impedance of an Induction Motor by Using All-Phase FFT With Intermediate-Frequency Filtering

This letter proposes an online extraction method of common-mode (CM) impedance of induction motor based on all-phase spectrum calculation. All-phase fast Fourier transform with intermediate-frequency filtering (ApFFTIF) is proposed based on infinite impulse response filter, zero-phase filtering technique, and all-phase fast Fourier transform. By using ApFFTIF, the accurate amplitude spectrum together with accurate phase spectrum of CM impedance of induction motor are extracted. Then genetic algorithm is used to establish the model of CM impedance of inductor motor. Finally, through comparing CM impedances extracted by using different spectrum calculation methods, and through comparing measured and calculated CM currents, the accuracy of the proposed method is validated.

Low spurious optoelectronic oscillator achieved by frequency conversion filtering without deteriorating phase noise.

In order to obtain microwave signals with low spurs and low phase noise, we studied the residual phase noise of the frequency-conversion filtering oscillator and methods to improve its phase noise performance. We first analyze the influence of the dispersion of the intermediate frequency (IF) filter on the residual phase noise in the frequency conversion filtering process. Then, we use an electro-optic modulator to achieve up-conversion in the frequency conversion filtering and extend the intra-cavity delay with an optical fiber after the modulator. This allows the optoelectronic oscillator (OEO) to improve the phase noise performance while having a good suppression of spurs. The spurs suppression ratio of the proposed OEO is 80 dB with a fiber of about 1.6 km in the cavity. The phase noise of the proposed OEO is -130 dBc/Hz at 10 kHz offset from 10 GHz, which is 10 dB lower than our previous work.

Wideband dual‐mode microstrip resonators as IF filters in a K‐band wireless transceiver

AbstractIn this article, the design, construction and characterization of band‐pass filters (BPF), based on the classic single‐structure, square‐loop, dual‐mode resonator rings (SL‐DMRR) is revisited. A specific requirement is proposed for using such a basic topology: the design and fabrication of L‐band SL‐DMRR filters to be part of the intermediate frequency (IF) section of a heterodyne K‐band microwave transceiver. The heterodyne K‐band transceiver has been designed and implemented to measure atmospheric attenuation at 22.4 GHz, in the vicinity of the strong absorption peak by water vapor molecules in the atmosphere. The BPFs are designed to operate at a center frequency of 1.1 GHz and a minimum bandwidth of 200 MHz. SL‐DMRR filters in the L‐band microwave range are more compact when compared to other microstrip structures such as parallel coupled lines, tapped input digital filters, hairpin filters, and so on. Filter realizations on FR4 and RT/Duroid 6010 substrates are optimized by resolving narrow coupling gap (0.07‐0.1 mm), between the input/output stubs and the resonator ring. Narrow gaps (less than 0.1 mm) are an original achievement in our work to ensure insertion losses of 1 dB for FR4, 0.5 dB for RT/Duroid, return losses better than 20 dB and a minimum bandwidth of 200 MHz. These figures represent an appreciable advancement of the state‐of‐the‐art for these classic structures for filters. The simulated and measured electrical responses of the filters show an excellent agreement. The IF filter has been incorporated to the K‐band receiver and the system's performance is also reported in this article.

A 26-GHz transmitter front-end using double quadrature architecture.

A 26-GHz transmitter front-end is designed using 65 nm CMOS technology. The double frequency conversion transmitter consists of an intermediate frequency(IF) mixer, an millimeter-wave(mm-wave) mixer, and a pre-power amplifier. A double quadrature architecture is employed to accomplish image rejection without using an image rejection filter for the first time in the mm-wave frequency band. The IF mixer cores are designed as harmonic rejection mixers to avoid using IF filters. The measured conversion gain is 26.85±0.65 dB, with LO2 (IF LO) at 1–1.5 GHz and 26.9±0.6 dB with LO1 (mm-wave LO) at 27–29 GHz. The measured output return loss is less than -10 dB at 25.7–27.2 GHz. The output 1-dB compression point and the saturation output power measured at 26 GHz are 10 dBm and 14.1 dBm, respectively. The output-referred third-order intercept point (OIP3) measured at 26 GHz is 15.76 dBm. The third-order distortion, suppressed by the harmonic rejection mixer, is -60.5 dBc at an output power of 10 dBm. The error vector magnitude measured for OFDM 16-QAM with a 110-MHz signal bandwidth is -17.7 dB at an average output power of 3.5 dBm. The total power consumption of the proposed 26-GHz transmitter front-end is 267 mW, and it occupies a chip area of 2.31 mm2.

Design of Reconfigurable Digital IF Filter With Low Complexity

Due to limited frequency resources, new services are being applied to the existing frequencies, and service providers are allocating some of the existing frequencies for newly enhanced mobile communications. Because of this frequency environment, repeater and base station systems for mobile communications are becoming more complicated, and frequency interference caused by multiple bands and services is getting worse. Therefore, a heterodyne receiver using intermediate frequency (IF) filters with high selectivity has been used to minimize the interference between frequencies. However, repeater and base station systems in mobile communications employing fixed IF filters cannot actively cope with the usage of multiple frequency bands, the application of various services, and frequency recycling. Therefore, this brief proposes a reconfigurable digital IF filter with variable center frequency and bandwidth while achieving high selectivity as existing IF filters. The center frequency of a filter can vary from 10 MHz to 62.5 MHz, and the filter bandwidth can be selective to one of 10 MHz, 15 MHz, and 20 MHz. The proposed digital filter also reduces the complexity of adders and multipliers by 38.81% and 41.57%, respectively, compared to an existing digital filter by using a filter bank and a multi stage structure. This digital IF filter is fabricated on a 130-nm CMOS process and occupies 5.90 mm2.

Development of a correlation ECE radiometer for electron temperature fluctuation measurements in Heliotron J

A radial correlation ECE radiometer diagnostic has been developed for electron temperature fluctuation measurements in the helical-axis heliotron device, Heliotron J. The radiometer consists of two heterodyne detection systems. One system scans the frequency of a local oscillator from 52 to 64 GHz with a single intermediate frequency filter, and the second system has a fixed frequency, 56 GHz local oscillator with four intermediate frequency filters. This frequency range covers measurement positions spanning from the plasma core to the half radius. Laboratory tests indicate that each system has narrow intermediate frequency bandwidth and high-sensitivity over a large dynamic range. During plasma experiments with NBI heating, radiation temperature fluctuation measured by the CECE radiometer decrease with increasing ECCD commensurate with previous measurements of energetic particle driven modes on Heliotron J.

A compact 220 GHz heterodyne receiver module with planar Schottky diodes

This letter presents the development of a compact 220 GHz heterodyne receiver module for radars application in which a novel low pass wide stop band intermediate frequency (IF) filter is integrated. The planar Schottky anti-parallel mixing diode based subharmonic mixer (SHM) is used as the receiver’s first stage. The diode is flip-chip mounted on a 50 μm thick quartz substrate. The accurate modeling of the self and mutual inductance of the diode’s air-bridges are discussed. The measured conversion loss (CL) of the SHM has a minimum value of 6.2 dB at 210.5 GHz, and is lower than 8.4 dB in the frequency range 209.4–219.6 GHz with a 10 mW input power from a local oscillator (LO). The LO chain consists of a 110 GHz passive tripler, two Ka-band amplifiers and a Ka-band active tripler. The tested minimum double side band (DSB) noise temperature of the integrated 220 GHz heterodyne receiver is 725 K at 205.2 GHz and lower than 1550 K in the frequency range 199–226 GHz.

Acoustic Wave Filter Technology-A Review.

Today, acoustic filters are the filter technology to meet the requirements with respect to performance dictated by the cellular phone standards and their form factor. Around two billion cellular phones are sold every year, and smart phones are of a very high percentage of approximately two-thirds. Smart phones require a very high number of filter functions ranging from the low double-digit range up to almost triple digit numbers in the near future. In the frequency range up to 1 GHz, surface acoustic wave (SAW) filters are almost exclusively employed, while in the higher frequency range, bulk acoustic wave (BAW) and SAW filters are competing for their shares. Prerequisites for the success of acoustic filters were the availability of high-quality substrates, advanced and highly reproducible fabrication technologies, optimum filter techniques, precise simulation software, and advanced design tools that allow the fast and efficient design according to customer specifications. This paper will try to focus on innovations leading to high volume applications of intermediate frequency (IF) and radio frequency (RF) acoustic filters, e.g., TV IF filters, IF filters for cellular phones, and SAW/BAW RF filters for the RF front-end of cellular phones.

Design and fabrication of aluminum nitride Lamb wave resonators towards high figure of merit for intermediate frequency filter applications

A design guideline for one-port aluminum nitride (AlN) Lamb wave resonators (LWRs) working at S0 mode with high performance is reported. A fabricated 252 MHz LWR, with an aperture of 200 μm, 12 fingers, and 1.5 μm thick AlN, is found to have a remarkably high figure of merit (FOM), which exhibits a high ratio of the resistance at parallel resonance (Rp) to the resistance at series resonance (Rs) of 1317 and a corresponding product of the effective coupling coefficient (k2eff) and quality factor (Q) exceeding 52. Consisting of such resonators, a 6-stage ladder filter with a low pass-band insertion loss (IL) of 4.5 dB and steep filter skirts is achieved, offering significant advantage of size savings.

Calibration of a 32 channel electron cyclotron emission radiometer on the HL-2A tokamak

A novel 32-channel electron cyclotron emission radiometer has been designed and tested for the measurement of electron temperature profiles on the HL-2A tokamak. This system is based on the intermediate frequency filter detection technique, and has the features of wide working frequency range and high spatial resolution. Two relative calibration methods have been investigated: sweeping the toroidal magnetic field and hopping the output frequency of the local oscillator. Preliminary results show that both methods can ensure reasonable profiles.

HIGH THROUGHPUT FILTER ARCHITECTURE FOR OPTIMAL FPGA-BASED IMPLEMENTATIONS

Modern field programmable gate arrays (FPGAs) offer built in support for efficient implementation of signal processing algorithms in the form of specialized embedded blocks such as high speed carry chains, specialized shift registers, adders, multiply accumulators (MAC) and block memories. These dedicated elements provide increased computational power and are used for efficient implementation of computationally extensive algorithms. This paper proposes a novel algorithm and architecture for the design and implementation of high performance intermediate frequency (IF) filters on FPGAs. In this research, we have proposed innovative design methodologies for generation of optimal feed forward and recursive architectures to be mapped on a family of FPGAs. Keeping in perspective the limited number of registers within the embedded blocks, the new methodology applies transformations to achieve higher throughput by applying various optimizations to the design algorithm. Implementation options include systolic MAC, transpose direct form MAC, canonic signed digit and distributed arithmetic based filters to suite the most economical FPGA implementation. The paper demonstrates the methodology and shows its applicability by synthesizing the designs and comparing the results to a number of traditional architectures and intellectual property cores. Using Xilinx Virtex-5 FPGA, our results show a throughput improvement between 7% and 30% with an average improvement of 16% over traditional implementations of these designs.

Design and Simulation of an IF MEMS Filter Based on Face Shear Mode Square Resonator

Intermediate frequency (IF) Filters with IC (Integrated circuit) compatibility, narrow bandwidth and large stop band rejection are in need for wireless communications. This paper presents the design and simulation of a 70 MHz IF Micro-electro-mechanical filter using two identical face shear mode square resonators. By carefully designing the supporting structure of the resonators, a quality factor above 100,000 is achieved in the best designed resonator. With these face shear mode square resonators, three filters are designed and the simulated transmission response shows that these filters can obtain unterminated transmission passbands of about 25 kHz to 35 kHz with the centre frequency of 70 MHz, which represents a 0.036% to 0.05% bandwidth. This ultra narrow bandwidth IF bandpass filter can be an attractive candidate for wireless receivers.

Low‐power 24 GHz CMOS receiver front‐end using isolation enhancement technique for automatic radar systems

AbstractThis article describes a monolithic receiver front‐end comprising a low‐noise amplifier, a dual‐gate mixer, and an intermediate‐frequency (IF) amplifier implemented in a standard 0.18 μm CMOS technology. Over the frequency band of interest, flat and high conversion‐gain (CG) and flat and low noise‐figure (NF) are achieved simultaneously by adopting slightly under‐damped Q‐factors for the second‐order CG and NF frequency responses. To suppress the high‐frequency noise and to enhance the RF–IF and LO–IF isolation, RC low‐pass filters (i.e., IF filters) are added at output of the dual‐gate mixer and the cascode IF amplifier. The receiver front‐end dissipates 16.4 mW and exhibits an NF of 6.86 dB and a CG of 22.26 dB at 24 GHz. In addition, excellent isolation is also achieved. The measured LO–IF, RF–IF, and LO–RF isolation is −31.31, −49.36, and −58.93 dB, respectively, at 24 GHz. The chip area is only 1.21 × 0.7 mm2, that is, 0.847 mm2, excluding the test pads. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1471–1476, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26835

Low power and high conversion gain 21‐GHz receiver front end in a standard 0.18 μm CMOS technology

AbstractThis article describes a monolithic receiver front end comprising a low‐noise amplifier (LNA), a mixer, an intermediate‐frequency (IF) amplifier, and an IF filter implemented in a standard 0.18 μm CMOS technology.Current‐reused technique is used in the LNA to reduce power dissipation. Current bleeding technique is used in the mixer to improve conversion gain and power linearity. To enhance RF–IF and LO–IF isolation, an RC low‐pass filter (i.e., IF filter) is added in the drain terminal of the input transistor of the cascode IF amplifier. At an RF of 21 GHz and IF of 2.4 GHz, the receiver front end dissipated 43.2 mW and exhibited a noise figure (NF) of 8.6 dB, and a conversion gain of 20.3 dB. In addition, excellent isolation was also achieved. The measured LO–IF and LO‐RF isolation is −30.9 dB and −51.1 dB, respectively, at LOin of −1 dBm. The measured RF–IF isolation is −57.3 dB at RFin of −30 dBm. The chip area is only 0.97 × 0.9 mm2, that is, 0.873 mm2, excluding the test pads. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2875–2879, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26423

An Improved 110–130-GHZ Fix-Tuned Subharmonic Mixer with Compact Microstrip Resonant Cell Structure

This paper presents the design and fabrication of an improved low-loss 110–130 GHz subharmonically pumped mixer with planar Schottky diodes fabricated by Virginia Diodes Inc. The antiparallel pair of planar GaAs Schottky diodes flip-chipped onto a suspended microstrip is fully integrated with a radio frequency (RF) and an intermediate frequency (IF) filter. A compact microstrip resonant cell (CMRC) filter is for the first time introduced in a submillimeter mixer to replace the traditional low-and-high-impedance microstrip RF filter. The shorter size and wider stop-band of the CMRC filter improved the performance of the subharmonic mixer. The best single-sideband (SSB) conversion loss of 7.7 dB was achieved with 3.5 mW of local oscillator (LO) power at a fixed 59 GHz of LO frequency. Over an RF band of 20 GHz, the SSB conversion loss is below 11 dB.