Showing papers on "Frequency response published in 1984"
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01 Dec 1984
TL;DR: In this paper, an error bound for reduced order models obtained from internally balanced realizations is derived, where the error bound is that the infinity norm of the frequency response of the difference between the full and reduced-order models is bounded by twice the sum of the balanced grammian's singular values that correspond to the truncated states of a balanced realization.
Abstract: An error bound for reduced order models obtained from internally balanced realizations is derived. The bound is that the infinity norm of the frequency response of the difference between the full and reduced order models is bounded by twice the sum of the balanced grammian's singular values that correspond to the truncated states of the balanced realization. The importance of a frequency weighted model reduction and the infinity norm for control system applications is discussed. A frequency weighted balanced realization which depends on specified input and output model reduction weightings is defined. Results for an example are compared using the weighted and unweighted balancing model reduction techniques.
731 citations
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TL;DR: In this paper, two methods for the linear approximation of a transfer function with a pole of fractional power are presented, and the Pade method gives a better approximation than Wang and Hsia's method within the frequency limit as specified.
Abstract: Two methods for the linear approximation of a transfer function with a pole of fractional power are presented. Analog circuit models are developed, and their frequency response curves and step response curves are compared. It was found that the Pade method gives a better approximation than Wang and Hsia's method within the frequency limit as specified.
480 citations
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01 Jul 1984TL;DR: In this paper, the authors discuss the implementation of fiber-optic lattice structures incorporating singlemode fibers and directional couplers, and show that the pole of the system transfer function with the largest magnitude is simple and positive-valued (in the Z-plane), and that the magnitude of the frequency response can nowhere exceed its value at the origin.
Abstract: We discuss the implementation of fiber-optic lattice structures incorporating single-mode fibers and directional couplers. These fiber structures can be used to perform various high-speed time-domain and frequency-domain functions such as matrix operations and frequency filtering. In this paper we mainly consider systems in which the signals (optical intensities) and coupling coefficients are nonnegative quantities; these systems fit well in the theory of positive systems. We use this theory to conclude, for example, that for such systems the pole of the system transfer function with the largest magnitude is simple and positive-valued (in the Z-plane), and that the magnitude of the frequency response can nowhere exceed its value at the origin. We also discuss the effects of various noise phenomena on the performance of fiber-optic signal processors, particularly considering the effects of laser source phase fluctuations. Experimental results are presented showing that the dynamic range of the fiber systems, discussed in this paper, is limited, not by the laser source intensity noise or shot noise, but by the laser phase-induced intensity noise. Mathematical analyses of lattice structures as well as additional applications are also presented.
362 citations
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TL;DR: In this article, the analysis of GaAs MESFET distributed amplifiers and a systematic approach to their design are presented, focusing on fundamental design considerations and also establishing the maximum gain-bandwidth product of the amplifier.
Abstract: In the paper, the analysis of GaAs MESFET distributed amplifiers and a systematic approach to their design are presented. The analysis focuses on fundamental design considerations and also establishes the maximum gain-bandwidth product of the amplifier.The design approach presented enables one to examine the tradeoffs between the variables, such as the device, the number of devices, and the impedances and cutoff frequency of the lines, and arrive at a design which gives the desired frequency response. Excellent agreement is shown when the theoretically predicted response of a typical amplifier is compared with computer-aided analysis results, and good agreement is shown with previously published experimental results.
349 citations
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TL;DR: In this paper, the traveling wave electrodes are laterally shifted periodically to reverse the direction of the applied electric field within the optical waveguide which exactly compensates for the polarity reversal caused by the microwave-optical walkoff.
Abstract: We propose and analyze a new technique for achieving velocity match between the traveling wave electrical drive and guided optical signal for modulators in substrates for which there is an inherent mismatch. The traveling wave electrodes are laterally shifted periodically to reverse the direction of the applied electric field within the optical waveguide which exactly compensates for the polarity reversal caused by the microwave-optical walkoff. Consequently, the electrooptically induced phase shifts of each section add in phase and several sections can be used to reduce the required drive voltage at the design frequency. This artificial velocity-matching technique moves the mismatch-limited bandwidth to an arbitrarily high design frequency. In addition, we extend the new concept of phase reversal and the previously suggested technique of intermittent interaction by proposing electrode structures with large inactive to active aspect ratios. This generalization provides increased flexibility for manipulating the total available bandwidth to, for example, allow efficient modulation by a train of arbitrarily short electrical pulses. These techniques are ideally suited for several proposed integrated optic devices, including picosecond samplers and gates, which require strong overmodulation at a single high frequency.
143 citations
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TL;DR: In this article, a differential input hearing aid with a programmable frequency response is presented, where audio inputs of two microphones are applied to a subtractive circuit with the balance of the inputs being controllable.
Abstract: A differential input hearing aid with a programmable frequency response provides the hard of hearing with the capability to listen to individual conversations in the midst of high ambient background noise, and to have the frequency response of the hearing aid tailored to the individual user by programming the desired response characteristics into the hearing aid by digital signals. The audio inputs of two microphones are applied to a subtractive circuit with the balance of the inputs being controllable. Digitally controlled band pass filters with selectable band and selectable level of amplification are provided.
97 citations
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TL;DR: In this article, an electrical equalization network is coupled to the transducer, cooperating with the acoustic components to obtain a frequency response characteristic which is either flat or which matches that of the human ear.
Abstract: Insert earphones, which are especially useful for audiometry applications include a transducer which is coupled to a resonance cancellation tube as well as to a main tube which is coupled to the ear, with series acoustic dampers in the tubes, operating in a known manner to obtain a smoothly varying frequency response characteristic. An electrical equalization network is coupled to the transducer, cooperating with the acoustic components to obtain a frequency response characteristic which is either flat or which matches that of the human ear. The dampers in series with the main and cancellation tubes have acoustic resistances which are respectively about 20% lower and 20% higher than the characteristic impedances of such tubes, operating to obtain a broadband increase in output.
81 citations
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06 Apr 1984TL;DR: In this paper, an optical spatial frequency filter with a pair of birefringent elements with means for changing the polarization state of light between them is given a substantially color dependent spatial frequency response, which is particularly useful with a color image sensor having a first sampling frequency in a first color and a second sampling frequency different from the first in a second color.
Abstract: An optical spatial frequency filter of the type having a pair of birefringent elements with means for changing the polarization state of light between them is given a substantially color dependent spatial frequency response. The filter comprises a wavelength dependent means for changing the polarization state of light between the birefringent elements such that the polarization state of light of a first color is changed by a first amount and the polarization state of light of a second color is changed by a second amount sufficiently different from the first amount such that the spatial frequency response of the spatial frequency filter is substantially color dependent. The filter is particularly useful with a color image sensor of the type having a first sampling frequency in a first color and a second sampling frequency different from the first in a second color. The filter is made to have a frequency response in the first and second colors in relation to the respective first and second sampling frequencies of the sensor. The filter has the advantage that, when used with the color image sensor, aliasing is selectively reduced in each color without reducing resolution in the other colors.
72 citations
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TL;DR: Sine-wave currents intracellularly injected into spinal α-motoneurones were found to modulate sinusoidally the regular rhythmic firing evoked by a current step, and the sensitivity and the phase relationships were estimated by varying the modulation frequency of a given sine- wave.
Abstract: 1)
Sine-wave currents intracellularly injected into spinal α-motoneurones were found to modulate sinusoidally the regular rhythmic firing (carrier frequency) evoked by a current step. Cycle histograms of the instantaneous frequency could be accurately fitted by sinusoidal functions. Those functions were treated as the cell output.
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For a given modulation frequency between 2 and 14–18 Hz, the amplitude of the cell output was linearly related to the amplitude of the sine-wave current, all over a wide range of current intensities.
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The sensitivity (gain) and the phase relationships were estimated by varying the modulation frequency of a given sine-wave. When modulation frequency varied from 1–2 Hz to 14–18 Hz, there was a progressive increase of the gain and a phase advance. The experimental gain curve closely conformed to the response of an ideal linear transducer sensitive to both the intensity and the velocity of the input. The phase advance was instead less than that predicted by the model. No “carrier dependent” variations of gain and phase were detected.
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Differences among motoneurones regarded both the static gain and the “corner frequency” (a measure of the dynamic sensitivity). In 10 motoneurones, the corner frequency ranged between 5 and 10 Hz.
71 citations
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TL;DR: The objective of this paper is to develop a computer-aided method for synthesizing the pulse-transfer function of the digital controller by matching the frequency response of thedigital control system to that of the continuous system with a minimum weighted mean-square error.
Abstract: The problem of converting existing continuous-data control systems into digital control systems is considered. The objective of this paper is to develop a computer-aided method for synthesizing the pulse-transfer function of the digital controller. This is done by matching the frequency response of the digital control system to that of the continuous system with a minimum weighted mean-square error. Formulas for computing the parameters of the digital controller are obtained as a result. The design technique is illustrated aith a numerical example, and a comparison with previous methods is also presented.
67 citations
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22 Jun 1984
TL;DR: In this paper, a read-only memory (ROM) is used to compensate for the microphone's nonlinear frequency response characteristic during their integration into a single unit, and the ROM is thus programmed to provide a frequency response complementary to that exhibited by the microphone.
Abstract: A microphone is provided with a read only memory (ROM) which is programmed to compensate for the microphone's nonlinear frequency response characteristic during their integration into a single unit. The ROM is thus programmed to provide a frequency response complementary to that exhibited by the microphone. The microphone may have a relatively poor frequency response over the audio spectrum, i.e., 20 Hz-20 kHz, but with the ROM serving to calibrate the microphone, the combination exhibits a relatively flat frequency response over this frequency range. Intended for use in a portable, battery operated, microprocessor-controlled audio spectrum analyzer, the integrated microphone and ROM combination is coupled to a CMOS random access memory (RAM) in which the calibration contents of the ROM are stored. During normal operation, the microprocessor reads the microphone calibration data from the thus programmed RAM in order to conserve battery power, but may read this data from the ROM when necessary. This permits an inexpensive microphone to be used in a high performance audio spectrum analyzer resulting in a flat frequency response.
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TL;DR: A frequency-dependent nonlinear quadrature model is developed for TWT amplifiers exhibiting both frequency- dependent amplitude nonlinearity and AM/PM conversion.
Abstract: A frequency-dependent nonlinear quadrature model is developed for TWT amplifiers exhibiting both frequency-dependent amplitude nonlinearity and AM/PM conversion.
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TL;DR: The present design was developed as an alternative to the fragile aluminum-ribbon microphones used previously and has the advantages of low cost, small size, robustness and a broad frequency response.
Abstract: Conventional particle velocity microphones (see Olson, 1957) are not readily available, are expensive, fragile and large, so they are not commonly used in biological research, though their use in one situation where the source is highly reactive, the recording of Drosophila song, is now standard practice. Here, the particle velocity produced by the fly is far louder than the sound pressure, so high quality recordings can be made with minimal sound insulation (see Bennet-Clark, 1971; Bennet-Clark, Leroy & Tsacas, 1980). The microphones can also be used to localize sources of echoes and to measure other reactive conditions. The present design was developed as an alternative to the fragile aluminum-ribbon microphones used previously (Bennet-Clark, 1973) and has the advantages of low cost, small size, robustness and a broad frequency response. The transducer is an electret membrane open on both sides to the sound wave. The resonant frequency of the electret unit is at the top of the practical frequency range of the microphone (16—17 kHz). Below this, the output is proportional to the driving force, the pressure gradient, so rises 6dB per octave and leads by 90 in phase compared with the particle velocity (see Michelsen & Nocke, 1974). The microphone has three major components, a pressure gradient transducer, an FET impedance converter in the microphone head and an integrating amplifier to correct the frequency and phase response of the transducer. The electret unit is Radio Shack type 270-090 (Fig. 1) (Tandy Corporation; products are available world-wide). Retain the metal-coated electret membrane on its supporting ring; the 40/im thick plastic spacer washer, the perforated fixed electrode and the FET (see Fig. 1). The membrane is reassembled so as to be open to the sound wave on both sides. Dimensions of a brass housing and PTFE or Delrin (Acetal) insulator are shown in Fig. 2A. Assembly is shown in Fig. 2B. The electret and fixed electrode are separated by the 40 /xm spacer washer and the fixed electrode is separated from the housing by the insulator. The edges of the brass housing can then be crimped over to secure the components in position. If the electret is heated, it may discharge. The FET amplifier should be built close to the transducer. A suitable layout, which incorporates the 1 • 1 k£2 FET load resistor, is shown in Fig. 2C and the circuit diagram is shown in Fig. 3. In this layout, response varies as the cosine of the angle from the
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01 Dec 1984TL;DR: In this article, an algorithm for adaptively controlling a single-input, single-output process admitting an n-dimensional, minimum phase linear model of relative degree n*, with unknown parameters is presented.
Abstract: This paper presents an algorithm for adaptively controlling a single-input, single-output process admitting an n-dimensional, minimum phase linear model of relative degree n*, with unknown parameters. Apriori knowledge of the sign of the model's high frequency gain is not required, and a sufficiently rich probing signal is not needed for stabilization.
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TL;DR: An improved method for transfer function synthesis from measured frequency response data is presented in this article, which is due to a new scheme of matrix adaptation that eliminates measurement dependent inaccuracies step by step.
Abstract: An improved method for transfer function synthesis from measured frequency response data is presented. The improvement is due to a new scheme of matrix adaptation that eliminates measurement dependent inaccuracies step by step. Arbitrary coefficients can be set to any preassigned values, so that account can be taken of previous knowledge of the investigated system. An extension to integrating systems is developed. The efficiency of the proposed method is demonstrated for an example taken from the literature.
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TL;DR: In this paper, the performance characteristics of RF discharge excited CO 2 waveguide laser are investigated as a function of the frequency of the power source in the range 50-250 MHz.
Abstract: The performance characteristics of RF discharge excited CO 2 waveguide lasers are investigated as a function of the frequency of the power source in the range 50-250 MHz. In addition, the influence of frequency on the spatial and electrical properties of the discharge are studied. The laser power output, which is seen to peak at a particular frequency, may be correlated with the achievement of optimum ( E/N ) values for energy transfer to the upper laser level. The form and distribution of striations, parallel to the electrodes, are seen to be a major factor influencing laser properties.
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TL;DR: In this article, the authors describe a broadly tuneable frequency tripler which can provide more than 2-mW output power at any frequency between 200 and 290 GHz, with the major improvements being the use of a new low-pass filter design implemented using a novel suspended substrate stripline structure, an optimized waveguide transformer, and a lower loss contacting output backshort.
Abstract: This paper describes a broadly tuneable frequency tripler which can provide more than 2-mW output power at any frequency between 200 and 290 GHz. It is derived from an earlier narrow-band prototype design, with the major improvements being the use of a new low-pass filter design implemented using a novel suspended substrate stripline structure, an optimized waveguide transformer, and a lower loss contacting output backshort.
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TL;DR: Optimum-matched dielectric-slab filled waveguide phase shifters are designed with the method of field expansion into eigenmodes, which includes higher order mode interaction between the step discontinuities as mentioned in this paper.
Abstract: Optimum-matched dielectric-slab filled waveguide phase shifters are designed with the method of field expansion into eigenmodes, which includes higher order mode interaction between the step discontinuities The relative phase shift is mechanically adjustable between 0° and about 360° at midband frequency by lateral displacement of the dielectric slab Computer-optimized design data are given for Ku-, K-, and Ka-band prototypes which achieve return losses of better than 40 dB, both as a function of displacement at midband frequency and as a function of frequency at fixed displacements Measurements verify the theory
01 Jan 1984
TL;DR: In this article, the characteristics of infinite line pressure probes are reviewed and some applications in turbine engine research are described, and techniques for predicting the frequency response of probes with both circular and flat-oval cross sections are also cited.
Abstract: The infinite line pressure probe provides a means for measuring high frequency fluctuating pressures in difficult environments. A properly designed infinite line probe does not resonate; thus its frequency response is not limited by acoustic resonance in the probe tubing, as in conventional probes. The characteristics of infinite line pressure probes are reviewed and some applications in turbine engine research are described. A probe with a flat-oval cross section, permitting a constant-impedance pressure transducer installation, is described. Techniques for predicting the frequency response of probes with both circular and flat-oval cross sections are also cited.
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13 Nov 1984
TL;DR: In this paper, the authors proposed a digital clock signal generator for generating clock signals at different frequencies and in particular a fractional frequency of a reference frequency, consisting of a digital inverter for extracting the harmonic frequency of order n and delivering a signal at a multiple frequency.
Abstract: A device for generating clock signals at different frequencies and in particular a fractional frequency of a reference frequency comprises a reference frequency generator which delivers at the output a reference signal having a frequency f, a frequency-divider for dividing by an integer p which delivers a signal at the frequency f/p at the output, and a digital inverter for extracting the harmonic frequency of order n and delivering a signal at a multiple frequency in order to obtain at the output of the device a signal of digital type having the frequency n/pf. A feedback loop impedance is coupled to the input and output of the inverter and preferably has a maximum value at the frequency nf. A load impedance is coupled to the input of the inverter and preferably has a minimum value at the frequency nf.
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TL;DR: In this article, the amplitude of the primary is replaced by an effective amplitude that depends on the amplitudes and relative phases of the two components of the excitation, and the expression for the effective amplitude is used to determine the amplitude and phase of a superharmonic excitation of order two or three needed to quench the primary response.
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TL;DR: In this article, the authors measured peak pressure in simulated atmospheric boundary layer flows using both high-frequency-response short-tube and long-tube systems with more limited frequency response, and showed that significant attenuation of the pressure and suction peaks occurs when long tube systems with a response flat to ∼100 Hz.
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TL;DR: In this article, single-stage and two-stage GaAs traveling-wave amplifiers operating with flat gain responses in the 2-20 GHz frequency range are described, realized in monolithic form on a 0.1-mm GaAs substrate with 50-Omega input and output lines.
Abstract: Single-stage and two-stage GaAs traveling-wave amplifiers operating with flat gain responses in the 2-20-GHz frequency range are described. The circuits are realized in monolithic form on a 0.1-mm GaAs substrate with 50-Omega input and output lines. Complete gate and drain dc bias circuitry is included on the chip. By cascading these amplifier chips, a 30-dB gain in the 2-20-GHz range is demonstrated, with 9+-1dB noise figure.
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TL;DR: In this paper, the authors investigated the linear dynamic response of an automotive radial tire, with particular focus on the frequency response, the travelling sinusoidal load response, and the response spectrum due to a random pavement.
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TL;DR: In this paper, the authors describe an audio signal reproduction system having one or more of the following features: (1) a loudspeaker having a flat frequency response and a predetermined power response; (2) two loudspeakers adapted to be positioned relative to one another so that they reproduce a stereophonic image substantially independent of the listener's position along a listening line spaced from the loudspeakers and nonintersecting a line extending between the two speakers; (3) an improved cross-over network having a substantially constant input impedance as a function of frequency; (4) a
Abstract: The disclosure relates to an audio signal reproduction system having one or more of the following features: (1) a loudspeaker having (a) a flat frequency response and (b) a predetermined power response; (2) two loudspeakers adapted to be positioned relative to one another so that they reproduce a stereophonic image substantially independent of the listener's position along a listening line spaced from the loudspeakers and nonintersecting a line extending between the two speakers; (3) an improved cross-over network having a substantially constant input impedance as a function of frequency; (4) a power sensor for sensing the power applied to a transducer so that audio signals are transmitted over a first signal path through the system when the sensed power is above a predetermined minimum level, and over a second path when the sensed power falls below the minimum level; (5) a power monitoring circuit to prevent a loudspeaker driver from being overdriven; and (6) a circuit for substantially balancing the signal energy levels between two audio channels over a long period of time.
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TL;DR: In this paper, the forced frequency response characteristics of systems which can be considered to exhibit single or normal mode characteristics and which incorporate spatially localized clearance-type nonlinearities are analyzed by using both analytical and digital simulation methods.
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13 Aug 1984TL;DR: In this paper, an AGC shunt device is connected between the input and shaping sections of a photodiode and a transimpedance amplifier to maintain the frequency response of the shaping section so that it continues to compensate for the amplitude response characteristic of the input section.
Abstract: The circuit (34) is of the type having an input section (12) and a shaping section (22). The input section includes a photodiode (14) and a transimpedance amplifier (16) with an AGC shunt device (19) connected between its input nodes (+,-). The shaping section includes, in order, an AGC amplifier (24), an equalizer amplifier (26), a buffer amplifier (42), and a filter (44). A controller (36) responsive to the photocurrent controls the impedance value of a dynamic impedance in the equalizer so that the frequency zero of the equalizer tracks the pole frequency of the input section as it changes in the course of changes in the value of its AGC shunt. This maintains the frequency response of the shaping section so that it continues to compensate for the frequency response characteristic of the input section. A trigger (52) responsive to the impedance value of the shunt activates the equalizer only when the shunt is active. Also disclosed is a particularly advantageous differential configuration for the equalizer which includes a diode bridge (76,78,80,82) and four setting resistors (R 1 ,R 2 , R 3 ,R 4 ) by which the break points for the frequency response can be set.
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TL;DR: In this paper, computer-optimized design data for a four-resonator metallic E-plane filter with a midband frequency of about 94 GHz is given with a method of field expansion into suitable eigenmodes used considering the effects of finite insert thickness and higher order mode interaction.
Abstract: Computer-optimized design data for a four-resonator metallic E-plane filter are given with a midband frequency of about 94 GHz The method of field expansion into suitable eigenmodes used considers the effects of finite insert thickness and higher order mode interaction The measured minimum passband insertion loss of a metal filter prototype is 15 dB
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TL;DR: In this paper, a method of correction for temperature fluctuation spectra and RMS intensity accounting for thermal inertia of the wire, end conduction heat loss between wire and prongs, and spatial resolution is proposed to determine the temperature variance profile in the heated wake of a line source in a turbulent boundary layer.
Abstract: It has been shown previously that the frequency response of cold wires used to measure a turbulent temperature field can be noticeably attenuated because of thermal inertia of the wire, end conduction heat loss between wire and prongs, and spatial resolution. The correction of temperature signals is, therefore, indispensable. The transfer functions of cold wires have been determined by using a home-made dynamic calibration system. A theoretical analysis is used to take into account spatial resolution. The proposed method of correction for temperature fluctuation spectra and RMS intensity accounting for these three effects is applied to the determination of temperature variance profile in the heated wake of a line source in a turbulent boundary layer.