Center Frequency Of Bandpass Filter Research Articles

Constant absolute bandwidth six-pole quasi-elliptic tunable bandpass filter using synchronously tuned dual-mode resonators

This paper presents the design of a 6th-order tunable bandpass filter (BPF) that achieves constant absolute bandwidth (ABW) and transmission zeros (TZs) across a wide frequency tuning range. The proposed tunable BPF employs three synchronously tuned dual-mode resonators, along with a frequency-dependent coupling structure realized using a T-network consisting of series and shunt capacitors. To achieve constant ABW, the tunable external quality factors are implemented using series capacitor and shunt varactor. As an illustrative example, a 6th-order BPF is fabricated and measured, results revealing that the center frequency of BPF can be tuned from 1.39 GHz to 1.81 GHz (26.25 %) with two TZs on the lower and upper side of the passband, 1-dB constant ABW of 62 ± 1.5 MHz and return loss > 12 dB in every tuning state.

Effective Position Error Compensation in Sensorless Control Based on Unified Model of SPMSM and IPMSM

Sliding mode observer (SMO) has attracted extensive attention in the field of medium- and high-speed sensorless control of permanent magnet synchronous (PMSM) because of its strong robustness and stability. However, the traditional methods are vulnerable to dc bias caused by measurement errors and parameter changes. Therefore, an improved SMO algorithm by disturbance observer compensation is proposed in this article. The algorithm unifies the mathematical models of surface PMSM and interior PMSM. Besides, a band-pass filter (BPF) is used to replace the traditional low-pass filter, so it can effectively suppress dc bias and high-frequency noise. In addition, at any BPF center frequency, the proposed disturbance observer with LPF characteristics can perfectly compensate the position error caused by the digital filter in real time. Moreover, through sensitivity analysis, the influence of model uncertainty on the observation position is studied, and an adaptive extended state observer is added to mitigate the influence of parameter mismatch on the performance, and hence improving the estimation accuracy. Finally, a triple redundant permanent magnet assisted synchronous reluctance motor is taken as an example to verify the feasibility and effectiveness of the proposed observer.

Design and fabrication of a miniaturized lowpass-bandpass diplexer with wide tuning range and high isolation

ABSTRACTIn this article, a compact lowpass-bandpass (LP-BP) diplexer with high isolation for wireless telecommunication applications is presented. The −3 dB cut-off frequency of the lowpass filter (LPF) is equal to 1 GHz. The roll-off-rate (ROF or ζ) parameter is sharp and equal to 108.8 dB/GHz, and the rejection level in the stopband is 20 dB. The center frequency of bandpass filter (BPF) is 2.4 GHz. The tuning range of −3 dB cut-off frequency of the LPF is wide and ranges from 0.3 to 0.89 GHz. The tuning range of center frequency of the BPF is wide and ranges from 2.65 to 3.1 GHz. The obtained isolation between the two output ports is better than 30 dB. The proposed tunable LP-BP diplexer is designed, simulated, fabricated and measured. The results of measurement and simulation are in good agreement with each other. The proposed diplexer has a compact size of 64 × 38 mm2.

DESIGN OF BAND-PASS FILTERS WITH NON-EQUIRIPPLE FREQUENCY RESPONSES

Introduction. Band-pass filters circuit elements can be calculated by converting low-pass filter (LPF) parameters, which is the prototype of the designed band-pass filter. The conversion causes problems in case calculated values of circuit elements (resistors and capacitors) are out of standard values determined by the GOST standard. Obviously, frequency characteristics of band-pass filters are distorted when replacing the calculated values of circuit elements by the standard ones. The number of circuit elements with values different from standard can be reduced to zero by solving an additional system of equations that connects parameters of designed and reintroduced non-equiripple frequency responses. Objective. The objective of this work is to develop a calculation method of band-pass ladder filters with values of circuit elements corresponding to standard ones. Materials and methods. The filter design process includes two stages. The first stage is a parameters calculation of a polynomial LPF prototype. The calculated parameters are determined as a system of equations solution set. The equations are formed by equating coefficients of variables raised to the same powers in transfer function (TF) expressions of designed and realized filters. Initial characteristics are the filter order and frequency response unevenness. The transition to the standard values of circuit elements can be done when solving another system of equations that connects LPF converted parameters with unknown parameters of reintroduced non-equiripple frequency response. Results. TF of LPF prototypes up to the fifth order and frequency responses of band-pass filters (BPF) and bandrejection filters up to the tenth order are presented. Analytical expressions of non-equiripple and equiripple frequency responses are used to estimate distortions of the latter when a band-pass filter center frequency is tuned by using variable inductors or capacitors. The integral quadratic function of a variable is taken as a measure of real frequency response distortions. The tenth order BPF calculation example is given. Conclusion. The presented calculation methods of band-pass filters and given example demonstrate possibilities of the filter design method based on the systems of non-linear equations solution. In contrast to approximation methods of ideal filter frequency response by using special functions and tabular filters design, the presented method allows high-order filter calculation for any initial requirements without using reference data.

Electrically Tunable Ferrite Bandpass Filter in X-Band With Wide Tunability

An electrically tunable bandpass filter is designed using ferrite inductor as a tuning element. The device is made electrically tunable by winding copper coils around ferrite substrate. Ferrite substrate is made of low-temperature co-fire ceramic compatible ferrite tape (ESL 40011). The $50~\Omega $ microstrip line is printed on the ferrite substrate in the form of a rectangular loop. The area of the loop determines the center frequency of the filter. This structure results in a closed-loop magnetic field in the ferrite substrate when bias is applied thereby reducing the losses and improving efficiency. Center frequency of bandpass filter is around 9.6 GHz. Tunability of the filter is around 11%. Bias current is varied from 50 to 350 mA. This corresponds to an effective magnetic field varying from 15 to 80 Oe. Center frequency of the bandpass filter shifted from 9.6 GHz to around 10.8 GHz due to the application of bias field. Due to the reduction in the slope of bias curve (hysteresis curve) of the ferrite material with an increase in the bias field, the tunability of the device saturates at high bias fields. The coils are wound around the ferrite material to provide a dc bias in the azimuthal direction (in the plane of substrate). High degree of tunability has been achieved from very low bias currents by this design. Insertion loss of the filter varied from 2 to 2.6 dB which is primarily due to the losses in the ferrite material. This filter can be used for high-power applications due to the ferrite material used for fabrication. High-power measurements show stability up to 2 W of input power. Beyond 2 W, this filter can be used for pulsed power applications. Low-field losses in the ferrite material can be avoided by choosing an operating frequency above $4\pi \text{M}_{\mathbf {s}}$ which is about 9 GHz for this material.

Based on the Pseudo Code Ranging Network Broadband Spectrum Perception Algorithm

The research based on the related network broadband spectrum sensing algorithm of pn code ranging. More than the traditional spectrum sensing method based on narrow band as the research basis, through the radio-frequency head band pass filter center frequency change and implementation, therefore, not effective spectrum of broadband usage in real time tracking and perception, therefore, put forward the network broadband spectrum sensing algorithm based on pseudo code ranging. Spectrum resource usage through the main user judgment, build relevant spectrum perception model, according to theory of time serial search for pseudo code capture, until the results reached the preset threshold, enter the pn code tracking, according to the obtained phase difference sequence regulating local phase to achieve two sequences are minimum steady-state phase, implementation pseudo-code tracking, thus complete the perception of broadband spectrum and tracking. The experimental results show that the improved algorithm for network broadband spectrum perception can effectively reduce because of the negative impact of such factors as the channel fading and improve the processing speed and the reliability of perception, to provide data support to improve the utilization rate of spectrum resources, has a great advantage.

Effect of Center Frequency Deviation in Miniaturized CMOS Bandpass Filter

In this letter, the effect of quality factor on center frequency deviation in miniaturized coupled line bandpass filter (BPF) with diagonally end-shorted at their opposite sides and lumped capacitors is theoretically analyzed. The miniaturized BPF of a two-stage structure with two types of quality factors in standard CMOS process was designed and manufactured at 5.5 GHz. The die area of BPF was . The measured center frequency of BPF with a quality factor of 4.9 was deviated from 5.5 GHz to 4.7 GHz. The one with 14.8 was shifted to 5GHz. The theoretical and measured results validate that quality factor influences the center frequency shift of BPF.

A Passive Mixer-First Receiver With Digitally Controlled and Widely Tunable RF Interface

A software-defined radio (SDR) receiver with baseband programmable RF bandpass filter (BPF) and impedance match is presented. The passive mixer-first architecture used here allows the impedance characteristics of the receiver's baseband circuits to be translated to the RF port of the receiver. Tuning the resistance at the baseband port allows for a real impedance match to the antenna. The addition of complex between I and Q paths allows for matching to the imaginary component of the antenna impedance. By implementing both real and imaginary components with resistors in feedback around low noise baseband amplifiers, noise figure is also kept low. Tunable sampling capacitors on the baseband side of the passive mixer translate to tunable-Q filters on the RF port which allow for very good out-of-band linearity. Furthermore, the concept of in-band and out-of-band must be redefined as the impedance match and BPF center frequency move with the LO frequency, such that matching and filtering track the receive frequency. Additionally, 8-phase mixing is shown to provide significant benefits such as impedance matching range, rejection of blockers at LO harmonics, and lower noise figure (NF). Measurements from the receiver implemented in 65 nm CMOS show 70 dB of gain, NF as low as 3 dB, and 25 dBm out-of-band IIP3. Furthermore, tunable impedance matching shows that S11 <;- 30 dB can be achieved at any receive frequency from 0.1-1.3 GHz.

The control of electrical properties of multilayered LC-filter for 5 GHz applications

The effects of design, material and process parameters on the electrical properties and microstructures of laminated LC-filter for 5 GHz applications are described in this paper. The center frequency of bandpass filter can be controlled by the length of loading capacitor and the attenuation characteristics of filter depend on the degree of coupling between resonators. The microstructure of internal electrode and ceramic body strongly depends on the firing condition. Also, the selection and handling of surface roughness of the internal electrode are important to improve the insertion loss.

Broad-Band Lightwave Synthesized Frequency Sweeper Using Synchronous Filtering

We describe a broad-band lightwave synthesized frequency sweeper (LSFS) that uses synchronous filtering. We control the center frequency of the bandpass filter (BPF) in the LSFS so that it tracks the frequency of the circulating pulse. In the first half of this paper, we numerically simulate the accumulation of amplified spontaneous emission (ASE) noise in the LSFS and confirm the effectiveness of synchronous filtering in suppressing the noise. We show that the frequency sweep span can be enlarged to cover the erbium-doped fiber amplifier gain bandwidth completely if ideal synchronous filtering is realized. We also describe the way in which the fluctuation of the BPF center frequency severely limits the number of pulse circulations and we estimate the accuracy required for the BPF center frequency control. In the second half, we report our experimental results. We confirmed the completion of more than 10 000 pulse circulations, which corresponded to a frequency sweep span of >1.2 THz. We also estimated the accuracy of the BPF center frequency control experimentally. As a result, the relationship between the accuracy and the number of pulse circulations was in good agreement with that obtained in the simulation.

A new approach to the effect of bandpass filters on sound absorption calculations

Atmospheric absorption losses are usually calculated for single frequencies, but must often be applied to bandpass-filtered data, usually in octave bands or one-third octave bands. The simplest approach, using the absorption value at the bandpass filter center frequency, is inaccurate for broadband sources when the losses are large because the resulting spectrum has a large negative slope with frequency, and thus the band level is dominated by power near the lower band edge. The proposed new approach uses a representative frequency at which absorption is calculated and which depends on the total absorption along the path. An expression for the representative frequency is derived and errors are evaluated for several cases. A practical method, suitable for hand or computer implementation, is proposed.s

A pitch perception study for a cochlear implant user with residual hearing in the contralateral ear

In order to combine electrical and acoustic signals for multichannel cochlear implant users with residual hearing in the unimplanted ear, it is important to determine the degree of overlap in pitch sensations on the two sides. A pitch scaling experiment was performed maintaining constant and identical repetition rates on both the implanted (left) and normal (right) ear. The acoustic signals consisted of bandpass‐filtered pulses {with center frequencies ranging from 350–850 Hz). These were transmitted in synchrony with electrical pulses to one of five selected bipolar electrode pairs spanning 15.75 mm of the scala tympani (from approximately 2.25 to 18 mm beyond the base). The spacing between the two electrodes of each bipolar pair was 1.5 min. The experiment was repeated for repetition rates of 112.5 and 205 Hz. Pitch sensations on the left (electrical) side were reported to be as low as, and at times even lower than, on the right (acoustic) side. All signals were sealed with respect to an acoustic reference stimulus that had a bandpass filter center frequency at 450 Hz. Synthetic vowels were derived from the pitch scaling results and acoustic strategies only as well as combined electrical and acoustic strategies were tested. It was found that the best results were obtained from a combined electrical and acoustic strategy where the electrode information is chosen such that pitch perception overlap with the acoustic side is minimized. [Work supported by NIH Grant NS21027.]