Showing papers on "Electronic filter published in 1983"

Novel topological alternatives to the design of a harmonic-free, utility/DC interface

Abstract: Circuit designs previously proposed for utility/DC power conditioning interfaces that draw a harmonic-free, unity power factor ac current have, for the most part, followed a certain topological approach. This paper discusses several alternative approaches that can greatly improve the interface's simplicity, performance, and cost. One suggestion involves the use of a dc current source instead of a voltage source. Another concerns the use of a tuned passive filter to remove the ripple from the dc system's waveforms. Results from an experimental 6 kW rectifier are included to demonstrate the feasibility and usefulness of the approaches suggested.

A digitally programmable switched-capacitor universal active filter/oscillator

Abstract: A universal second-order switched-capacitor filter section has been fabricated on an NMOS chip. The device can perform all five basic filter types as well as a sine wave oscillator without external components, while requiring only an external clock. The filter type is determined by selecting one or more of three input pins. The filter response is determined by ten external programming pins which may be either digitally controlled or hard wired.

Clock-frequency recovery device adapted to high-frequency radiocommunications in disturbed media

Abstract: A clock-frequency recovery device applicable to digital transmission systems for radiocommunications by tropospheric or ionospheric propagation as well as from moving vehicles includes a rectification circuit, a filter circuit, a switching circuit and an output circuit comprising a delay line controlled by a phase-locked oscillator. The input of the output circuit is connected to the output of the filter circuit when the noise level of the transmission is below a predetermined threshold value. The input of the output circuit is connected to its own output when the noise level of the transmission is higher than said threshold value.

Timing extraction circuit

Abstract: A timing extraction circuit includes a phase comparator, a charge pump circuit, a filter circuit and a voltage controlled oscillator, these components constituting a phase-locked loop. The phase comparator compares the phases of a digital data signal and a timing signal and supplies first and second difference signals to the charge pump circuit. The charge pump circuit detects a phase error corresponding to the difference between the integrals of the first and second difference signals. The filter circuit supplies a control signal corresponding to the phase error to the voltage controlled oscillator. The voltage controlled oscillator generates the timing signal having a period corresponding to the control signal.

Minimal delay realization of first order 2-D all-pass digital filters

Abstract: A method is proposed to realize a first-order 2-D all-pass transfer function with two delays and six multipliers. Stability constraints on the coefficients of first-order 2-D filters are used to guarantee the existence of real-gain multipliers for the realized filter.

Low-Loss SAW Filter Using Single-Phase IDTs and No External Tuning

Abstract: Currently available techniques for implementing SAW filters with low insertion loss generally require multi-layer fabrication and/or complex external tuning and matching networks, with corresponding cost and size penalties. Here we report a new type of low-loss SAW filter which uses single level f abrication and which is naturally matched to 5011 and so requires no external components. The IDTs are d isplaced laterally (rather than the usual longitudinal arrangement), and SAW is transmitted between these IDTs by two reflecting multistrip couplers (RMSC) of a novel d esign. Most of the selectivity is provided by the RMSCs. The IDTs perform some filtering but the main design consideration was to achieve a natural 50R real impedance. Results are presented for the experimental and theoretical charactrrisation of many designs of RMSC on 128O YX lithium niobate and the responses of filters with fractional bandwidths of about 1% are shown.

High efficiency high frequency power oscillator

Abstract: The invention relates to a high frequency, high mechanical energy output apparatus comprising a transducer, a filter circuit, and a driving circuit. The transducer and the filter circuit are serially coupled together, and the transducer operates at its fundamental frequency of oscillatory motion. The driving circuit serves to drive the transducer at its fundamental frequency and comprises first and second active devices, wherein each active device has an output circuit and a control circuit. Each of the active devices are cooperatively connected together and are responsive to control signals for producing an alternating output signal. There is also provided means coupling the output circuits of the active devices to the transducer so that an alternating series current signal is applied serially through the transducer. The filter circuit filters from the alternating series current signal substantially all harmonics of the fundamental frequency of oscillation of the transducer to produce a filtered series current signal. There is also provided means for coupling the filtered series current signal to the control circuits of the active devices such that the filtered series current signal constitutes the control signal for controlling each of the first and second active devices for producing an output signal from the driving circuit substantially at the fundamental frequency.

Ultrasound imaging system employing operator controlled filter for reflected signal attenuation compensation

Abstract: The amplitudes of electrical signals generated by a transducer in an ultrasound scanning system are controlled by applying the electrical signals to an electrical filter whose frequency pass characteristics can be varied. As the ampltude and frequency of the generated electrical signals decrease due to passage through tissue, the low frequency of the filter is reduced. The control of the filter can be automatically implemented or can be manually implemented by the system operator.

Controlled power line filters for suppressing interference

Abstract: A power line filter comprises a filter circuit in the form of an impedor assembly (30) that filters a network supply voltage to be applied to a load. A voltage sensor means (34) monitors a characteristic of the supply that is representative of the interference content of the supply voltage. A microprocessor (36) compares the monitored characteristic with data that is stored in a memory (38) and is representative of a desired supply characteristic. By way of control means (32), the microprocessor (36) cause variation of a filtration characteristic of the impedor assembly (30) in a sense to minimize any divergence between the two above-mentioned characteristics, thereby to better suppress the interference.

Miniature 90 MHz low-loss narrowband SAW filter using new resonant configuration

Abstract: A new low-loss narrowband SAW filter that uses one pair of electrically connected IDTs with an optimum number of fingers, as well as SAW reflectors, is described. A miniature filter with a loss as low as 2 dB and a bandwidth of 0.7% at 90 MHz is presented. The filter is mounted in a TO-8 package and is usable without any outer inductors.

A Bipolar, High Precision, Low Ripple Power Supply

Abstract: A ±600 V, ±50 Amp high precision SCR power supply has been developed for use in the Energy Doubler Correction system. The bipolar output is accomplished by means of a dual converter with circulating current for smooth zero-crossing current transitions. Absolute accuracy better than ±.025% is achieved with a high precision transductor, current reference, and other high quality components. Stability is better than 2.5 ppm/°C and voltage ripple is less than 30 mV peak to peak. Low ripple is achieved through the use of bipolar series-pass transistor bank. The dual converter (plus a passive filter) acts as a pre-regulator for the transistor bank, which has a dynamic range of 30 volts. Ripple attenuation of the transistor bank is a minimum of 60 dB from DC to 2 kHz. Microvolt level noise and pickup in the power supply regulator ultimately set the ripple level in the power supply output. A special "active ground" circuit is included to filter the common mode ripple which is inherent in SCR supplies.

A fully adaptive transversal canceler and equalizer chip

Abstract: A wide dynamic range (84dB) analog sampled-data transversal filter circuit will be described. The chip in CMOS technology is 34mm2and includes all timing, control and memory circuits for both a 24th-order adaptive canceler and a user-programmable eighth-order gain/slope equalizer.

Filter circuit for digital-to-analog converter

Abstract: A filter circuit smooths the output signal of a digital-to-analog converter by providing linear ramps between adjacent steps of the signal. The circuit measures the voltage difference between two adjacent step levels, amplifies the difference voltage by a predetermined gain, 10 in the present example, then applies the amplified signal to an integrating network having a time constant which is determined by the amplifier gain and the sampling time of the D/A converter. The integrator output signal is summed over the sample period with the converter output signal level of the next preceding sample time period, thereby providing a waveform which has substantially linear transitions between adjacent D/A output levels.

Colour video signal processing

Abstract: A filter adaptively filters a PAL (or NTSC) luminance signal so as to attenuate the high frequency portion of the luminance band, in which the chrominance information lies, when movement is detected. This reduces cross-colour in the reproduced picture. Movement is detected by comparing (20) the undelayed luminance signal with this signal delayed (18) by an integral number of lines corresponding substantially to one field or one picture. The resultant is applied to a ROM (22) which provides a multiplier coefficient to a multiplier (26) at the output of a high-pass filter circuit (16) in the luminance channel. The filter may precede a coder (Figure 2) or follow a decoder (Figure 3).

Optical Excision In The Frequency Plane

Abstract: This paper presents recent advancements in RF filtering techniques through the use ofacousto- optics and a special purpose array of wideband photodiodes. An electronicallyprogrammable filter may be synthesized by inserting this array of photodiodes into thefrequency plane of an optical spectrum analyzer. A description of the optical system, thephotodiode array and some experimental results are presented.IntroductionThe reception and recording of wideband signals in various types of noise environmentshas been studied and analyzed for many decades. The enhancement of signal -to -noise ratiosand improvement in the dynamic range for recording and communications purposes haveincorporated such notch filter techniques as programmable digital filters, tunable L -Cfilters, and even superconducting filters for the excision of narrowband interference fromthe received information to be processed.These electronic filter techniques are very effective in enhancing the signal -to -noiseratio of an RF signal. A source of error for these filters is the phase distortion whichoccurs at the bandstop -passband edges of the filter shape. These errors, although somewhatpredictable, will add up and may severely distort the received signals when multiplefilters are stacked in series.Performing these RF filter functions in the frequency plane of an optical spectrumanalyzer1 -4 has several advantages over the current electronic techniques. First, whensome object is placed in the frequency plane of the optical spectrum analyzer, the magnitudeof the affected frequency interval is attenuated and the phase remains constant. Also, theoptical spectrum analyzer offers a high degree of parallelism which is a function of thetime -bandwidth product associated with the acousto -optic cell chosen. Many filters may berealized simply by inserting more objects into the frequency plane. With the currenttechnology, time -bandwidth products of 1000 are feasible with bandwidths ranging from 10 to1000 MHz. This time -bandwidth product of 1000 implies 1000 resolvable frequency components.Optical configurationThe optical excisor evaluated is shown in Figure 1. This configuration is a Mach -Zehnder interferometers with an acousto -optic (AO) cell operating as a spectrum analyzerinserted in one path of the interferometer.

Low-loss unidirectional SAW filters using integrated microinductors

Abstract: A SAW filter (using GUDTs for excitation and detection) has been described, requiring no external discrete components for the matching and the phase shifting networks. Using this design the filter can be fabricated on a single chip of substrate using the integrated-circuit fabrication procedures. The theoretical analysis has been done using the crossfield equivalent-circuit model of the filter and the results are in good correspondence with the experimental results.

Inverter controlling system for induction motor

Abstract: PURPOSE:To reduce the capacity of a smoothing capacitor in a filter circuit by a method wherein a phase difference is selected between frequency signals supplied to inverters in response to a selection of carrier frequencies for pulse width modulation CONSTITUTION:The system is constituted of pulse width modulation inverters 4A and 4B receiving power from a common filter circuit 3, induction motors 5A- 5H controlled by the respective inverters 4A and 4B, voltage control means 11A and 11B for controlling the inverter output voltages, and a frequency control means 9 for controlling inverter operating frequencies in response to revolving speeds A phase shift circuit 28 is added to said system which provides a phase shift to frequency signals being fed to each inverter from frequency control means 11A and 11B, while said circuit 28 switches over the magnitude of the phase difference in accordance with the carrier frequency switching over of the pulse width modulation The system being thus constructed, the ripple frequency in the output current from the filter circuit 3 is larger, realizing a smoothing capacitor 7 effectively functioning with a reduced capacity in the filter circuit 3

Noise eliminating device

Abstract: PURPOSE:To improve the eliminating capacity of an impulsive noise eliminating circuit, by arranging a filter circuit, which stops the passage of a continuously generated impulsive noise signal when this signal is received, in the output side of a single-generated noise pulse eliminating circuit. CONSTITUTION:When a single impulsive noise signal is included in the wave detection output from a wave detecting circuit 1, the output of a noise amplifier 8 is not changed much, and therefore, the level of the amplification degree control signal of an amplification degree controlling circuit 10 is low, and a switching transistor TR 14 is turned off, and a filter circuit 11 does not function. Consequently, the held level signal of a capacitor 4 for holding the storage which is provided in the output side of a switch 3 for eliminating the single noise pulse is sent to a voice part 6 as it is. When a continuously generated impulsive noise is included in the wave detection output, the switching TR 14 is turned on, and therefore, the noise signal which passes through the switch 3 erroneously is eliminated by a low pass filter consisting of a resistance 12 and a capacitor 13 and is not sent to the voice part 6.

Internal-combustion engine filter regenerating device

Abstract: PURPOSE:To obtain a stable and highly efficient filter regenerating device for internal-combustion engine by providing pressure sensors before and behind a DPF and judging the regenerating time from the ratio between the sizes of the AC components, and from the pressure signals, of the outputs of both sensors. CONSTITUTION:Pressures before and behind a DPF 5 are transduced into electric signals by means of pressure 22, 22', through pressure measuring tubes 21, 21' provided on an exhaust pipe 3. These pressure signals are amplified by amplifiers 23, 23' and are separated into DC components and AC components by means of high-pass filter circuits 24, 24' and low-pass filter circuits 25, 25' respectively. The DC components are operated through a subtraction circuit 27 to produce a difference between the DC components, i.e., a pressure loss, which is outputted to a processing circuit 28. As for the AC components, the ratio between the sizes of the AC signals is operated through a division circuit 26 and the result is outputted to the processing circuit 28. The processing circuit 28 outputs a signal to make a control circuit 7 carry out the regeneration of the DPF based on said two signals.

Motion compensating inter-frame decoding device

Abstract: PURPOSE:To remarkably reduce deterioration of a picture quality, by outputting while suppressing at least a minute variation out of amplitude variations between frames, of a TV signal outputted from a decoding circuit. CONSTITUTION:A decoder 5 decodes a forecasting error signal inputted from a signal line 3, sends it to an adder 7, and the adder 7 adds an expanded forecasting error signal and a forecasting signal applied from a signal line 6, decodes a TV signal, and applies the signal to a frame memory 13 and a filter circuit 9 through a signal line 8. The signal inputted to this memory 13 is delayed by 1 frame, applied to a variable delaying circuit 15, delayed in accordance with a dynamic vector signal by the circuit 15, and supplied as a forecasting signal to the adder 7. On the other hand, the circuit 9 suppresses a minute variation of a TV signal between adjacent frames, and outputs an analog signal obtained through a D/A converter 11, to a signal line 12.

Filter circuit element

Abstract: PURPOSE:To obtain a small sized filter element, by making the length of lines from the input to the output of a resonator formed with slot lines in a counterclockwise route different from the length in a clockwise route, in a hybrid IC constituting the closed slot lines on the surface of the insulating base CONSTITUTION:A ring shaped slot line 3 is provided on the surface of a dielectric base 2, for example a signal input microstrip line 1 is provided for the back side so that a center line passes through the center point of the line 3 corresponding to the surface, and a signal output microstrip line 4 is provided for the center line of the line 1 with an angle theta to the center point of the line 3 In propagating electromagnetic waves from the line 1 to the line 4, when the theta is not zero, the length of clockwise and counterclockwise routes is changed, the degeneration of the resonance mode is released by the perturbation and the electromagnetic field having a band are stored Similarly, the waves are outputted to the line 4 with the microstrip-slot conversion Thus, the filter can be constituted with small sized elements

A Low Loss 0.9 GHz Band SAW Filter

Abstract: A l o w l o s s 0 . 9 GHz band S4W f i l t e r i s p r e s e n t The i n s e r t i o n l o s s o f t h e f i l t e r i s 4 . 2 : 0 . 7 ed . dB o v e r 3 . 4 % bandwidth, and t h e s i d e l o b e s are below 1 5 dB. I n t r o d u c t i o n Low l o s s SAW f i l t e r s o p e r a t i n g a t 0 . 9 G H z hand a r e d e s i r e d i n communication sys t ems , such as mobi le t e l ephone and p e r s o n a l r a d i o . R e c e n t l y , g roup t y p e u n i d i r e c t i o n a l t r a n s d u c e r s have been wide ly i n v e s t i g a t e d t o a c h i e v e low l o s s [ l ] . However, t h e y r e q u i r e a d d i t i o n a l phase s h i f t e r s . From t h e v iewpoin t o f f a b r i c a t i o n , a n o t h e r s i m p l e r t e c h n i q u e may be p r e f e r e d . I n t h e f i l t e r p r e s e n t e d i n t h i s p a p e r , t h e t e c h n i q u e o f i n t e r d i g i t a t i n g IDTs [ 2 ] i s employed, and , t h r e e unapodized and two apod ized IDTs a r e a r r a n g e d s i d e by s i d e t o r educe t h e i n h e r e n t b i d i r e c t i o n a l i t y l o s s . The f i l t e r r e q u i r e s no more f a b r i c a t i o n p r o c e s s e s than t h e conven t iona l one u s i n g two IDTs . But , i n t h i s t y p e o f f i l t e r , many e l e c t r o d e s a r e r e q u i r e d . In o r d e r t o reduce t h e number o f e l e c t r o d e s , t h e SINC f u n c t i o n t r u n c a t e d a f t e r s h o r t l e n g t h o f 1 . 5 ~ 1 i s used as t h e a p o d i z a t i o n f u n c t i o n . The s i d e l o b e s due t o t h e t r u n c a t i o n are suppres sed by m u l t i p l y i n g t h e SINC f u n c t i o n by a two-s t eps f u n c t i o n , t h a t i s a l i n e a r s u p e r p o s i t i o n o f two r e c t a n g u l a r f u n c t i o n s . The f i l t e r i s f a b r i c a t e d on 128' r o t a t e d Y c u t X p r o p a g a t i n g l i t h i u m n i o b a t e by u s i n g e l e c t r o n beam l i t h o g r a p h y . The i n s e r t i o n l o s s o f t h e f i l t e r i s 4 . 2 0 . 7 dB o v e r 3 . 4 % bandwidth , and t h e s i d e l o b e s a r e below -25 dB. S t r u c t u r e F ig . 1 shows t h e arrangement o f f i v e IDTs. The b i d i r e c t i o n a l i t y l o s s i n t h i s s t r u c t u r e i s 1 . 8 dB. The i n p u t t h r e e unapodized IDTs are so des igned t h a t t h e passband c h a r a c t e r i s t i c s of t h e f i l t e r are de termined p r i m a r i l y by t h e o u t p u t two apod ized IDTs. r e c t a n g u l a r f r equency r e s p o n s e , t h e S I N C f u n c t i o n I n o r d e r t o o b t a i n a n e a r l y ( s i n ( n t ) / ( F t ) , l i s s e l e c t e d a s a b a s i c f u n c t i o n f o r t h e apodi z a t i o n . I J ~ t h e f i l t e r o p e r a t i n g a t 0.9 Gtiz , l i n e / s p n c e wid th o f e l e c t r o d e s is about h a l f a micron, when t h e double e l e c t r o d e s s t r u c t u r c i s used . So, i t i s p a r t i c u l a r l y d e s i r e d t o r e a l i z e a s p e c i f i e d f r e quency r e sponse wi th a smal l number o f e l e c t r o d e s . Consequent ly , t h e SINC f u n c t i o n i s t r u n c a t e d a f t e r s h o r t l e n g t h o f l . S n , as shown i n F ig . 2 , and t h e s i d e l o b e s due t o t h e t r u n c a t i o n a r e suppres sed h y m u l t i p l y i n g i t by a p r o p e r we igh t ing f u n c t i o n . M u l t i p l i c a t i o n i n t h e time domain is c q u i v a l c n t t o convo lu t ion i n t h e f r equency domain. Hence, i n o r d e r t o suppress t h e s i d e l o b e s due t o t h e t r u n c n t i o n , t h e convolv ing f u n c t i o n , d e f i n e d by t h e F o u r i e r t r a n s f o r m o f t h e we igh t ing f u n c t i o n , i s r e q u i r e d t o have low s i d e l o b e s [ 3 ] . As t h e weight i n g f u n c t i o n , a two-s t eps f u n c t i o n i s employed. T h i s i s a l i n e a r s u p e r p o s i t i o n o f two d i f f e r e n t r e c t a n g u l a r f u n c t i o n s , as shown i n F i g . 2 . The l o n g e r l e n g t h T i s 3 7 1 . F i g . 3 shows t h e convolv ing f u n c t i o n s . The f u n c t i o n A co r re sponds t o t h e twos t e p s f u n c t i o n . The f u n c t i o n s B and C co r re spond t o t h e two r e c t a n g u l a r f u n c t i o n s , t h a t i s , t h e y a r e t h e convolv ing f u n c t i o n s i n t h e c a s e o f s imple t r u n c a t i o n . S ince t h e convolv ing f u n c t i o n A h a s lower s i d e l o b e s t h a n t h e convolv ing f u n c t i o n s B and C , t h e s i d e l o b e s due t o t h e t r u n c a t i o n can b e sup p r e s s e d by u s i n g t h e two-s t eps we igh t ing f u n c t i o n . The pa rame te r s o f IDTs a r e r e f i n e d th rough numer ica l c a l c u l a t i o n s , u s i n g t h e c r o s s e d f i e l d e q u i v a l e n t c i r c u i t model. F i g . 4 shows t h e c a l c u l a t e d f r equency r e sponses o f f i l t e r s , when t h e normal ized h e i g h t o f t h e f i r s t s t e p H i s f i x e d and t h e r a t i o o f l e n g t h s TI and T i s v a r i e d . I n t h e c a l c u l a t i o n s o f t h e s e r e s p o n s e s , t h e maximum o v e r l a p l e n g t h s o f IDTs a r e op t imized so t h a t t h e sum of t h e mismatch l o s s e s a t i n p u t and o u t p u t e l e c t r i c p o r t s r educes t o minimum. A s T ' / T d e c r e a s e s , t h e f i r s t s i d e l o b e l e v e l d e c r e a s e s . F i g . 5 shows t h e f r equency r e s p o n s e s , when T'/T i s f i x e d and H i s v a r i e d . A s 1-1 d e c r e a s e s , t h e f i r s t s i d e l o b e l e v e l d e c r e a s e s . For t h e c o n s t r u c t i o n o f t h e f i l t e r , T ' / T i s chosen t o be 0 . 4 3 , and H i s 0.5. I n t h i s c a s e , t h e f i r s t s i d e l o b e l e v e l i s suppres sed by 10 dB, compared wi th t h e c a s e o f s imple t r u n c a t i o n ( H = l ) , and t h e sha rp n e s s a t band edges i s n o t s e r i o u s l y degraded . 0090-5607/83/0000-0059 $01.0

A PISO JCCD filter with high-speed linear charge injection

Abstract: In junction charge-coupled devices (JCCDs), the unique possibility exists for charge injection through the gates. The process used for fabricating JCCDs also allows bipolar transistors and n-channel JFETs to be constructed. These features have been used to realize very linear charge-injection and charge-detection structures. By combining these structures, a parallel-in serial-out transversal JCCD filter has been realized. The filter is characterized by a high sampling rate and a low harmonic distortion.

Automatic balanced recording meter

Abstract: PURPOSE:To perform clean recording by using the constitution wherein resistors which are connected to a capacitor forming an input filter circuit are changed and the scanning speed of a pen is changed, thereby suppressing the effluence of ink. CONSTITUTION:A switching mechanism 11 can change the resistors 12 and 13 which are connected to the capacitor 14. An input signal (a) is applied to a servo motor 4 through the input filter circuit 1 which is provided with the switching mechanism 11, a preamplifier 2, and a power amplifier 3. The recording (b) is performed by the output of the motor through a speed reducing mechanism 5 and a pen mechanism 6. The running speed of the pen can be changed by the changed of the resistors 12 and 13. Therefore the amount of the offluence of the ink is suppressed in the sampling recording, and the clean recording can be performed.

Logical operation circuit

Abstract: PURPOSE:To obtain a circuit with good DC balance, by performing the logical operation of maximum value with the emitter connection of an NPN transistor (TR) and that of minimum value with the emitter connection of a PNP TR, respectively CONSTITUTION:A filter circuit for noise rejection is shown in figure and a television signal is inputted to the circuit The signal is delayed by delay circuits 3, 4 having a delay of one horizontal period respectively via a band pass filter and the correlation is taken with the signals (no correlation exists if noise is apart from each horizontal period) Circuits 5, 6, 10 output larger input signal and circuits 7, 8, 9 output smaller input signal, respectively The average output of the circuits 9, 10 is summed to a video signal obtained via a low-pass filter and outputted from an adder 11' Since TRs constituting the operation circuits are symmetrical between the input and output, good DC balance can be attained

Deflecting method of laser beam

Abstract: PURPOSE:To obtain a deflected beam having uniform intensity at a deflection angle over a wide range by providing a filter circuit which can correct the intensity of the acoustic wave propagating in an acousttooptic element according to the frequency thereof within a driving circuit for the acoustooptic element. CONSTITUTION:The output frequency of a voltage controlling oscillator 1 is determined by the DC voltage value applied on an input terminal 6 for a control voltage in a laser beam deflector and the oscillated output thereof is applied through a filter 2 and a power amplifier 3 to an acoustooptic element 4. The electric power applied on the element 4 is corrected with the frequency thereof by the filter circuit 2 having a suitable characteristic to negate the fluctuation in the deflecting efficiency of a laser beam 8 in the acoustic frequency range to be used by the change in the intensity of the acoustic wave. The beam 7 is thus deflected with the uniform intensity. The frequency characteristic of the circuit 2 is required to be adjusted by the deflecting efficiency characteristic of the element 4 and is made variable from the outside.