Showing papers on "Electronic filter published in 2008"

Nonlinear Complementary Filters on the Special Orthogonal Group

Abstract: This paper considers the problem of obtaining good attitude estimates from measurements obtained from typical low cost inertial measurement units. The outputs of such systems are characterized by high noise levels and time varying additive biases. We formulate the filtering problem as deterministic observer kinematics posed directly on the special orthogonal group SO (3) driven by reconstructed attitude and angular velocity measurements. Lyapunov analysis results for the proposed observers are derived that ensure almost global stability of the observer error. The approach taken leads to an observer that we term the direct complementary filter. By exploiting the geometry of the special orthogonal group a related observer, termed the passive complementary filter, is derived that decouples the gyro measurements from the reconstructed attitude in the observer inputs. Both the direct and passive filters can be extended to estimate gyro bias online. The passive filter is further developed to provide a formulation in terms of the measurement error that avoids any algebraic reconstruction of the attitude. This leads to an observer on SO(3), termed the explicit complementary filter, that requires only accelerometer and gyro outputs; is suitable for implementation on embedded hardware; and provides good attitude estimates as well as estimating the gyro biases online. The performance of the observers are demonstrated with a set of experiments performed on a robotic test-bed and a radio controlled unmanned aerial vehicle.

Ambient noise reduction system

Abstract: An adaptive, feed-forward, ambient noise-reduction system includes a reference microphone for generating first electrical signals representing incoming ambient noise, and a connection path including a circuit for inverting these signals and applying them to a loudspeaker directed into the ear of a user. The system also includes an error microphone for generating second electrical signals representative of sound (including that generated by the loudspeaker in response to the inverted first electrical signals) approaching the user's ear. An adaptive electronic filter is provided in the connection path, together with a controller for automatically adjusting one or more characteristics of the filter in response to the first and second electrical signals. The system is configured to constrain the operation of the adaptive filter such that it always conforms to one of a predetermined family of filter responses, thereby restricting the filter to operation within a predetermined and limited set of amplitude and phase characteristics.

Analysis and Design of Highly Compact Bandpass Waveguide Filter Using Complementary Split Ring Resonators(CSRR)

Abstract: Split Ring Resonators (SRR) and Complementary Split Ring Resonators (CSRR) are widely used to design metamaterial structures. These structures when excited by suitable electromagnetic fields have resonance behavior and show unusual properties such as negative permeability and permittivity near the resonance frequency region. In this paper, CSRRs are used to design a bandpass waveguide filter in the X-band. The circuit model of these elements in the waveguide is similar to parallel L and C components that are placed in parallel form in a transmission line. Resonance frequency and bandwidth of LC resonance circuit are adjusted by proper choice of the CSRR geometrical dimensions. Then, to design the miniaturized filter these structures are combined with proper admittance inverter. The admittance inverter is designed such that its electric length is very smaller than the conventional λ/4 transmission line. As a result, a filter is compacted about 66% in comparison to the λ/4 transmission line as admittance inverter. Simulation results by Ansoft HFSS (Based on the Finite Element Method) confirm the results of filter circuit model. 108 Bahrami, Hakkak, and Pirhadi

A 2.7-mW 2-MHz Continuous-Time $\Sigma \Delta$ Modulator With a Hybrid Active–Passive Loop Filter

Abstract: In this paper, passive continuous-time (CT) Sigma Delta modulators are briefly reviewed and compared with conventional active CT Sigma Delta modulators. A fifth-order CT Sigma Delta modulator with a hybrid active-passive loop filter is realized with only three active integrators. The hybrid CT Sigma Delta modulator is robust to the excess loop delay, clock jitter, and RC product variations. The prototype chip is designed in a 0.25- mum CMOS technology targeting for GPS or WCDMA applications. The experimental results show that the prototype Sigma Delta modulator achieves a 68-dB dynamic range and a - 75 dB IM3 over a 2-MHz bandwidth with a 150-MHz clock, consuming 1.8 mA from a 1.5-V supply.

Classical Circuit Theory

Abstract: This book begins with the basic principles of circuits, derives their analytic properties in both the time and frequency domains, and states and proves the two important theorems. It then develops an algorithmic method to design common and uncommon types of circuits, such as prototype filters, lumped delay lines, constant phase difference circuits, and delay equalizers. The material also discusses the relation between gain and phase, linear and minimum phase functions, group delay, sensitivity functions, scattering matrix, synthesis of transfer functions, approximation of filter functions, all-pass circuits, and circuit design by optimization. This book fills a need for a modern text on the mathematical foundations of passive circuits in general and passive filter design in particular. The mathematical foundations are what classical circuit theory, which is the subject of this book, is all about. It is old, but it has survived the test of time and it is still relevant today because it is basic.

Embedded EZ-Source Inverters

Abstract: Z-source inverters are recent topological options proposed for buck-boost energy conversion with a number of possible voltage and current-type circuitries already reported in the literature. Comparing them, a common feature noted is their inclusion of a LC impedance network, placed between the dc input source and inverter bridge. This impedance network allows the output end of a voltage-type Z-source inverter to be shorted for voltage-boosting without causing a large current flow, and the terminal current of a current-type inverter to be interrupted for current boosting without introducing over-voltage oscillations to the system. Therefore, Z-source inverters are in effect safer and less complex, and can be implemented using only passive elements with no additional active semiconductor needed. Believing in the prospects of Z-source inverters, this paper contributes by introducing a new family of embedded EZ-source inverters that can produce the same gain as the Z-source inverters, but with smoother and smaller current / voltage maintained across the dc input source and within the impedance network. These latter features are attained without using any additional passive filter, which surely is a favorable advantage since an added filter will raise the system cost, and at times can complicate the dynamic tuning and resonant consideration of the inverters. The same embedded concept can also be used for designing a full range of voltage and current-type inverters with each of them tested experimentally using a number of scaled down laboratory prototypes.

Implementation of a Dynamic Voltage Restorer System Based on Discrete Wavelet Transforms

Abstract: This paper presents an implementation of the discrete wavelet transform (DWT) using passive LC filters for operating a dynamic voltage restorer (DVR) system. The proposed implementation is based on designing Butterworth passive LC filters with cutoff frequencies that are identical to cutoff frequencies of DWT associated digital filters. These passive LC filters can detect abnormal conditions that may disrupt the quality of the power supplied to sensitive loads in a power system. Detecting any abnormal condition is realized through extracting high- and low-frequency components present in system voltages using high-pass and low-pass filters, respectively. The designed Butterworth passive LC passive filters are third-order systems to simplify their practical implementation as well as their integration with the test power system and the DVR. Simulation and experimental test results for transient voltage dip and steady-state harmonic distortion cases show significant performance improvement of the DVR system operated by the designed Butterworth passive LC filters. The proposed DWT-operated DVR system using Butterworth passive LC filters is implemented and tested for improving the power quality under different abnormal conditions.

A 2.4-GHz ISM-Band Sliding-IF Receiver With a 0.5-V Supply

Abstract: We report an ultra-low-voltage RF receiver for applications in the 2.4 GHz band, designed in a 90 nm CMOS technology. The sliding-IF receiver prototype includes an LNA, an image-reject LC filter with single-ended to differential conversion, an RF mixer, an LC IF filter, a quadrature IF mixer, RF and IF LO buffers, and an I/Q baseband section with a VGA and a low-pass channel-select filter in each path, all integrated on-chip. It has a programmable overall gain of 30 dB, noise figure of 18 dB, out-of-channel IIP3 of -22 dBm. The 3.4 mm2 chip consumes 8.5 mW from a 0.5 V supply.

A Low-Power WCDMA Transmitter with an Integrated Notch Filter

Abstract: In a WCDMA FDD system, since the transmitter and receiver operate concurrently, the receiver is plagued by the transmitter leakage due to finite isolation of antenna duplexer. As a consequence, the transmitter noise at the receive band degrades the sensitivity, unless the noise is further attenuated before reaching the receiver. Due to the modest Q of on-chip inductors, typically the use of a costly SAW filter placed before the PA is inevitable. On the other hand, the external filter may be eliminated through sufficiently lowering the transmitter noise for any given duplexer. However, given the power-noise trade off, in all previous designs due to the lack of an on-chip filtering mechanism, meeting the stringent noise requirement has resulted in an excessive transmitter power dissipation. To address these issues, a feedback-based filtering technique to suppress the receive-band noise with negligible area or power penalty is presented. Stability analysis reveals that with practical transmitter gain distribution, optimum component sizes, and for a typical required noise suppression, using a simple first- or second-order RC LPF, the feedback remains stable and no additional compensation is required.

Integrated RF Interference Suppression Filter Design Using Bond-Wire Inductors

Abstract: Design techniques are presented for the realization of high-performance integrated interference suppression filters using bond-wire inductors. A new configuration is proposed for mitigating the impact of mutual coupling between the bond wires. A differential low-noise amplifier with an integrated on-chip passive interference suppression filter is designed at 2.1 GHz in a 0.18-mum CMOS process, and achieves a transmit leakage suppression of 10 dB at 190-MHz offset. The differential filter uses metal-insulator-metal capacitors and bond-wire inductors and occupies only 0.22 mm2. The cascaded system achieves a measured gain of 9.5 dB with a 1.6-dB noise figure and -5 dBm out-of-band IIP3 and consumes 11 mA from a 2-V supply.

Conducted EMI noise mitigation in DC-DC converters using active filtering method

Abstract: Electromagnetic interference (EMI) noise mitigation is an important issue that should be addressed and emphasized when designing DC/DC converters. These later, are known to be the primary culprit of the EMI noise generation in most of the electronic systems, mainly due to the switching action of the MOSFET circuitries. Passive input EMI LC filters have been the intuitive solution for EMI noise mitigation; hence they have been integrated in almost every DC/DC converters. However, their size, weight and cost can cause a significant constraint in some applications. To overcome these constraints, an input active EMI filter is proposed. The active filter is based on the noise current phase shift and the injection of this noise current back to the DC input bus. However, the combination of the input active and the passive filters shows a substantial attenuation of the conducted emissions as compared to the passive filter only, which in turn contributes to the reduction of the size and weight of the input passive EMI filter. The proposed combination provides a design solution for compliance engineers where the PCB real-estate is an issue. Experimental results to demonstrate the performance and the effectiveness of the input active EMI filter in DC/DC converters are presented.

Universal resistorless current-mode filters employing CCCIIs

Abstract: In this paper, four different-type second-order current-mode filters, employing second-generation current-controlled conveyors (CCCIIs) and two capacitors, are proposed. The first two of the presented filters can simultaneously realize high-output impedance low-pass, band-pass and high-pass responses. Also, the two filters can provide notch and all-pass filter responses with interconnection of the relevant output currents. The first developed one needs no critical active and passive element matching conditions and-or cancellation constraints. The second and third introduced ones employ only grounded capacitors. The fourth proposed filter derived from the third one uses only plus-type single output CCCIIs (CCCII+s). The fifth filter can be constructed using commercially available active devices such as AD844s along with additional resistors instead of CCCII+s of the fourth proposed filter to perform experimental test easily. All of the proposed filters have low active and passive element sensitivities. Time and frequency domain analyses are performed for the first, second and third realized filters using SPICE simulation program. Also, experimental test is achieved for the fifth filter. In this study, stability problems attributed to non-ideal gains of the CCCIIs and signal limitations of the first, second and third introduced filters due to restricted power supply voltages are investigated. Copyright © 2007 John Wiley & Sons, Ltd.

A circuit model for nonlinear simulation of radio-frequency filters using bulk acoustic wave resonators

Abstract: This paper describes a circuit model for the analysis of nonlinearity in the filters based on radio- frequency (RF) bulk acoustic wave (BAW) resonators. The nonlinear output is expressed by a current source connected parallel to the linear resonator. Amplitude of the nonlinear current source is programmed proportional to the product of linear currents flowing in the resonator. Thus, the nonlinear analysis is performed by the common linear analysis, even for complex device structures. The analysis is applied to a ladder-type RF BAW filter, and frequency dependence of the nonlinear output is discussed. Furthermore, this analysis is verified through comparison with experiments.

Harmonic termination of power amplifiers using BAW filter output matching circuits

Abstract: A system, apparatus and method for providing filtering functionality and impedance transformation within a BAW resonator network are disclosed. In particular, a BAW resonator network is designed to provide bandpass capability and a transformation between its input impedance and output impedance. By effectively integrating impedance matching functionality within the BAW resonator network, discrete impedance matching elements previously required within a system may be removed or reduced in size. As a result, matching networks and their associated component costs, insertion losses, and board size contributions may be reduced. Harmonic termination may be provided within the BAW resonator network or a prematch stage to improve efficiency of a power amplifier.

Time-Interval Measurement Based on SAW Filter Excitation

Abstract: This paper deals with a novel time-interval measurement method that makes use of a surface acoustic wave (SAW) filter as a time interpolator. The method is based on the fact that a transversal SAW filter excited by a short pulse can generate a well-defined finite signal with highly suppressed spectra outside a narrow frequency band. If the responses to two excitations are sampled at clock ticks, they can be precisely reconstructed from a finite number of samples and then compared to determine the time interval between the two excitations. As a first step of a more comprehensive discussion of the method, the time-interpolation error caused by deterministic effects has been analyzed in this paper. It has been shown that the mean square of the interpolation error is limited by the upper bound, which is proportional to the relative energy of aliasing distortion and inversely proportional to the square of the filter center frequency. The upper bound has been compared to the results obtained from the simulation based on a linear-phase transversal filter. The RMS error resulting from the simulation exactly follows the slope of the theoretical upper bound, and it is approximately four times smaller than that. The described method excels in time interpolation efficiency since the time interpolation error relative to clock period is small; in other words, accurate measurement can be achieved even with a relatively low clock frequency. This has been practically demonstrated in a time-interval counter, which provides precision of 7-ps RMS using a clock frequency as low as 16.4 MHz. It results from the analysis that using state-of-the-art elements in the interpolator, the deterministic interpolation error on the order of 0.1 ps can be achieved.

6 MVA five-level hybrid converter for windpower

Abstract: For the further improvement of today's full converter systems for windpower applications a 6 MVA converter prototype has been developed. It is utilizing the ANPC5L topology as inverter on the grid-side and the simple 2-quadrant ANPC3L topology as rectifier for a permanent magnet synchronous generator (PMG). ANPC stands for Active Neutral Point Clamped, which is the base for the derivation of multiple topologies, i.e. 3-, 5- and higher levels. The ANPC5L converter is realized as a hybrid converter based on IGCT (Integrated Gate Commutated Thyristor) presspack devices and IGBT (Insulated Gate Bipolar Transistor) modules. The ANPC5L is modulated at 2 kHz. The IGCTs, used as inner switches, are operated at fundamental frequency, which allows a substantial reduction in silicon size. To meet the harmonic limits of the IEEE 519 no additional passive filter is required. To fulfill the more stringent VDEW requirements a simple LC filter is implemented. On the permanent generator side a simplified 2-quadrant 3 level converter (2Q-ANP3L), with 50% less turn-off switches than in a conventional NPC converter, is used. The operation of this simple topology with a discontinuous modulation allows the adjustment of the power factor of the permanent magnet synchronous generator for all operation conditions. The 6 MVA converter has been designed, built and tested in the power lab. The dimensions of the 6 MVA converter prototype, represents one of the most compact designs achieved for windpower applications today.

Charge monitoring device

Abstract: A charging monitor has: a switch that is disposed between a load section having a storage battery and an external AC power supply supplying a current to the load section via a plurality of lines and interrupts the supply of the current from the external AC power supply to the load section; a current detection circuit that outputs a detection signal corresponding to a difference in level between currents flowing through the lines; a suppression circuit that suppresses a DC component contained in the detection signal; a filter circuit that filters a plurality of frequency components contained in the detection signal so that attenuation increases as a frequency becomes high; a rectifier smoothing circuit that rectifies and smoothens an output signal obtained when the detection signal passes through the filter circuit and the suppression circuit; and an electric leakage determination circuit that detects an electric leakage and shuts off the switch when the level of the signal smoothened by the rectifier smoothing circuit exceeds a preset reference level.

A piezo-resistive resonant MEMS amplifier

Abstract: A MEMS resonator using electrostatic to piezo-resistive transduction is demonstrated to be capable of simultaneous signal filtering and amplification. The mechanical resonance serves as a high Q electrical filter, while the piezo-resistive readout allows for signal amplification. Amplification factors up to 4.6 dB and Q values up to 60,000 are obtained for a 15 MHz resonator.

Study on the Control of Shunt Active DC Filter for HVDC Systems

Abstract: A shunt active dc filter (ADF) has been applied in high-voltage dc transmission systems for harmonic suppression. Some key problems in the design of ADF control systems have not been investigated thoroughly due to high harmonic frequency and the complexity of system modeling. In this paper, a high-gain feedback control strategy is proposed, which is independent of circuit parameters. The authors draw a comparison between the harmonic suppression effects of ADF and that of a passive filter and prove that the former can increase the series impedance of the hybrid filter, while the latter can decrease the equivalent voltage. Based on circuit analyses, solutions, such as selection of the dc-side voltage, regulation of the modulation index, system stability conditions, filter design, and switching noise are presented. The consistency between theory analyses and experimental results verifies the feasibility of the proposed control strategy.

Large value AC capacitor for harmonic filtering and reactive power compensation

Abstract: To overcome the limitations of conventional shunt passive filters, which are invariably used for harmonic filtering, a quasi-passive filter (QPF) has been proposed. It comprises a parallel and series tuned LC tank circuit. Unlike the conventional shunt passive filter, the QPF utilises a large value AC capacitor. Unipolar DC capacitors and power semiconductor devices have been used to realise the large value AC capacitor. The operation of the QPF is simple and it does not require the complex control methods of active power filters. With certain modifications in the QPF, a modified quasi-passive filter (MQPF) has been proposed, which can be used for reactive power compensation in addition to harmonic filtering. The proposed QPF and MQPF have been verified through analysis and simulation. Experiments are carried out to verify the validity of the QPF.

Multiple-loop absolute type rotary encoder based on rotating transformer

Abstract: The invention relates to a multiturn absolute rotary encoder based on a rotary transformer, which is characterized in that: a sensor is displaced by taking the rotary transformer as a shaft angle; a shaft angle decoding circuit can be formed by adopting DSP as a core processor; a sine wave which can be controlled by frequency and phase in the method that the circuit is synthesized by direct digital frequency for the numerical control of an oscillator; and the sine wave is directly taken as an excitation rotary transformer signal via a power amplifier and a filter circuit; the rotary transformer signal is transferred to A/D converter after being run through a matching circuit of electronic transformer; after sampling, digital filtering and digital signal processing, the sine and cosine value for the actual angle of two channels is generated; the angle error change is tracked dynamically by the PI algorithm; the mechanical displacement of the rotating object is converted into digital shaft angle position and speed. The multiturn absolute rotary encoder based on a rotary transformer has the advantages of high tracking speed, high conversion accuracy, high reliability, simple structure, sensitive movement, low environmental condition, strong anti-interference capability, high measuring accuracy and speed voltage output.

Comparison of active filters topologies in medium voltage distribution power systems

Abstract: This paper presents the design of different topologies of active power filters to compensate reactive power and harmonics in the medium voltage level of a distribution power system. One pure active filter and two hybrid topologies, are implemented. A pure active compensation is obtained with a Shunt active power filter (SAPF). The shunt combination of SAPF and passive filter, form one of the hybrid topologies implemented, named shunt hybrid active power filter (SHAPF). The other hybrid topology, called hybrid shunt active power filter (HSAPF), connects the active filter in series with two shunt passive filters. Simulation for different load demands and distortions are performed. Finally a comparative evaluation of the different filters is carried out.

The algorithm for the parameters of AC filters in HVDC transmission system

Abstract: In conjunction with the reactive power exchange and AC voltage control, the issue of harmonic performance is one of the main power quality topics of high voltage direct current (HVDC) transmission projects. AC filters are widely used to restrain the AC side harmonics and to compensate for reactive power. The design of the AC filters has to satisfy the requirements of harmonic performance and reactive power compensation for the various operation modes. First of all the algorithm of the parameters of the single tuned filter are presented. Then during the process of designing double-tuned filter and triple tuned filter, two single tuned filters and three single tuned filters are designed to meet the need of reactive power compensation and the standard of harmonic restraint performance. With the parameters of two or three single tuned filters, formulae are given to calculate the parameters of double tuned filter and triple tuned filter. An example of designing a triple-tuned filter is offered. The impedance frequency characteristics of the three single tuned filters and the triple tuned filter are compared to show that the precision can meet the requirement of projects. Another way of double and triple tuned filter design, which is based on the analysis of circuits and impedance frequency characteristics of AC filters, is introduced. Two methods are compared to show both the advantage and the disadvantage of them.

Self-excited oscillation type high power LED constant-current driving circuit

Abstract: The invention provides a self-oscillation type high power LED constant-current drive circuit with low cost, high reliability and stability and high drive efficiency, the circuit comprises a rectifier and filter circuit, a switching circuit, a steady voltage constant current output circuit, a transformer, a self-oscillation type pulse width modulation signals generating circuit and a current feedback obstruction circuit, wherein the rectifier and filter circuit accesses commercial power into rectification, changes the commercial power into direct current, and then outputs commercial power to the switching circuit to switch in a self-oscillation type with high frequency, then high frequency voltage of the steady voltage constant current output circuit is transformed into direct voltage through the transformer to drive the LED, simultaneously sampling current signals produces jam signals through the current feedback obstruction circuit to control the switching circuit to work, the circuit does not adopt any driving chips and only uses fewer common individual devices to form a self-oscillation type structure to drive the switching circuit and to combine current feedbacks, which realizes constant current driving of the high power LED

A Fully Integrated Digital Hearing Aid Chip With Human Factors Considerations

Abstract: A low-power digital hearing aid chip with consideration of the human external ear characteristics according to the each individual user is proposed and implemented. It adopts the pre fitting verification algorithm (PREVA) to obtain the fast and accurate gain fitting and verification in two steps, coarse and fine gain fittings. The ear canal modeling filter circuit (EMC) which models the human external ear into the distributed LC filter enables the coarse gain fitting based on the shape of the external ear of the patient. The fine fitting verification is performed by the external inputs from the hearing loss test results. To reduce the power consumption of the human factored hearing aid chip design, the multi-threshold preamplifier, the adaptive fitting digital signal processor (DSP) with the filter reuse technique and the gated successive approximation ADC are designed and embedded to the digital hearing aid chip. The dynamic range of the multi-threshold preamplifier exists from 0.45 V to 0.8 V and dissipates 32 muW from a single 0.9 V supply. The fabricated digital hearing aid chip achieves the peak SNR of 81 dB in the overall system with 4.2 muV of input-referred noise voltage. The fabricated chip occupies the core area of 3.12times1.20 mm2 in a 0.18 mum standard CMOS technology and consumes only 107 muW from a single 0.9 V supply.

A Low-Power WCDMA Transmitter With an Integrated Notch Filter

Abstract: A filtering technique to attenuate the receive-band noise enables a 65-nm CMOS WCDMA transmitter to achieve an output noise level of -160 dBc/Hz at 80-MHz offset, while dissipating 65 mW Using a feedback filtering technique, the circuit introduces a null with an arbitrary width at the receive frequency and eliminates the need for an external SAW filter A stability analysis is performed to choose the most suitable architecture for the feedback path, which ensures stability over a wide range of loop-gain Nonideal effects such as quadrature phase and gain errors, LO feedthrough, harmonic downconversion and phase-noise are also analyzed

Frequency Domain Approach for Efficient Computation of Fixed-point Equalization Targets

Abstract: Various embodiments of the present invention provide systems and methods for equalizing an input signal. For example, various embodiments of the present invention provide a method for performing equalization in a storage device. Such methods include providing an equalizer circuit that is governed by a target value, and a filter circuit that is governed by a filter coefficient. An initial value is provided to the equalizer circuit as the target value, and an overall target based at least in part on the initial value and the filter coefficient is calculated. An updated value is calculated based on the overall target, and the updated value is provided to the equalizer circuit as the target value.

Design of passive filter components for switching band controlled DVR

Abstract: This paper presents a filter structure for improving the performance of switching band controlled Dynamic Voltage Restorer (DVR) and a systematic design procedure for the passive filter components. The switching operation of VSI is accompanied by a band controller which restricts the injected voltages within a band, defined about a reference voltage. Switching band control method exhibits merits such as fast dynamic response, robustness, zero magnitude / phase errors and ease in implementation. The performance of the band controller is improved using a novel filter structure. Quantitative expressions involving the dynamics of DVR and variation in switching frequency are also derived. The passive filter components are designed based on switching frequency and inverter rating. The proposed filter structure and design procedure for the DVR filter components are validated by carrying out PSCAD simulation studies.

Grass cutter intelligence control system

Abstract: The invention comprises: a motherboard circuit processor unit, a power and charging management circuit, a walk driving circuit, a grass-cutting driving circuit, a remote receiving circuit, an infrared detection circuit, a virtual line detecting circuit, a filter circuit, a hit processing circuit, a remote controller circuit. The motherboard processor unit is connected to the other circuits via each functional pin; the walk driving circuit is used for controlling the direction and speed of the mowing motor; the grass-cutting driving circuit is used for turn on or off the mowing motor; the infrared circuit uses a infrared transmitting tube and receiving tube to collect signals; the virtual line detecting circuit is used for converting the electromagnetic field signal produced by the virtual line into the electric signal; the filter circuit is used for filtering the virtual line signal.

Orthogonal frequency coded filters for use in ultra-wideband communication systems

Abstract: The use of ultra-short pulses, producing very wide bandwidths and low spectral power density, are the widely accepted approach for ultra-wideband (UWB) communication systems. This approach is simple and can be implemented with current digital signal processing technologies. However, surface acoustic wave (SAW) devices have the capability of producing complex signals with wide bandwidths and relatively high frequency operation. This approach, using SAW based correlators, eliminates many of the costly components that are needed in the IF block in the transmitter and receiver, and reduces many of the signal processing requirements. This work presents the development of SAW correlators using orthogonal frequency coding (OFC) for use in UWB spread spectrum communication systems. OFC and pseudo-noise (PN) coding provide a means for UWB spreading of data. The use of OFC spectrally spreads a PN sequence beyond that of code division multiple access (CDMA) because of the increased bandwidth providing an improvement in processing gain. The transceiver approach is still very similar to that of a CDMA but provides greater code diversity. Experimental results of a SAW filter designed with OFC transducers are presented. The SAW correlation filter was designed using seven contiguous chip frequencies within the transducer. SAW correlators with a 29% fractional bandwidth were fabricated on lithium niobate (LiNbO3) having a center frequency of 250 MHz. A coupling-of-modes (COM) model is used to predict the SAW filter response experimentally and is compared to the measured data. Good correlation between the predicted COM responses and the measured device data is obtained. Discussion of the design, analysis, and measurements are presented. The experimental matched filter results are shown for the OFC device and are compared to the ideal correlation. The results demonstrate the OFC SAW device concept for UWB communication transceivers.