Abstract:
Un circuit (10) possede une impedance d'entree variable qui est commandee par application d'un signal d'entree en courant continu. Le circuit d'impedance variable comprend une paire de condensateurs (12, 14) couples en serie avec une paire de diodes (32, 34). Les diodes sont rendues conductrices en reponse au signal de commande en courant continu pour cour-circuiter sensiblement les deux condensateurs en serie entre eux sur les bornes d'entree (7, 18) du circuit. Lorsqu'aucun signal de commande n'est applique sur le circuit, les diodes sont non conductrices, ce qui deconnecte les condensateurs des entrees du circuit. Par consequent, la composante de reactance de l'impedance d'entree du circuit varie en reponse au signal de commande en courant continu.
Abstract:
Un circuit de commande (10) approprie a une utilisation dans un amplificateur operationnel, comprend un transistor de redressement bipolaire (36) qui envoie un courant a une borne de sortie (38) proportionnellement a un courant de commande applique, et un transistor de rabaissement MOS (48) qui affaiblit le courant provenant de la borne de sortie (38) proportionnellement a une tension de commande appliquee. Un transistor de commande MOS (32) fournit un courant de commande constant pour le transistor de redressement (36), et un transistor de shuntage MOS (44) shunte le courant de commande en l'eloignant du transistor bipolaire (36) proportionnellement a la tension de commande. Un circuit de compensation de convergence (14) developpe une tension de polarisation predeterminee sur la base du transistor bipolaire (36) par rapport a la tension sur la borne de sortie (38) pour assurer un niveau minimum de fonctionnement du transistor bipolaire (36) lorsque la borne de sortie (38) est proche de la tension de terre analogique.
Abstract:
A manual tuning circuit for an AM and/or FM radio (10) in which the magnitude of the radio audible signals is intentionally varied in accordance with the magnitude of an error signal related to the absolute difference between the frequency of a desired received modulated carrier signal and the frequency to which the radio front end (11-17) is tuned. In this manner, precisely tuning the radio front end to precisely the desired frequency can be obtained by tuning for the maximum volume of radio audible signals. Preferably, this is accomplished through the use of full wave rectification of either the FM discriminator (35) DC output voltage or full wave rectification of the control voltage for a voltage controlled oscillator (VCO) (26) in a phase locked loop (24) which tracks the IF output signal of an AM/FM radio IF stage (16).
Abstract:
A battery powered paging device having an adaptive signal decoder (22) which is capable of processing detected encoded signals in accordance with a plurality of decoding schemes. The decoder has an equivalent microcomputer implementation (34). Energy conservation means (28) operating independently of the detected signals acts to conserve the energy of the battery.
Abstract:
Systeme de transmission de donnees ou des signaux de donnees sont transmis par le transmetteur (101 et Fig. 2) avec quatre etats binaires possibles a deux bits des lignes de signaux des donnees verifiees (221) et des donnees complementaires (220). Un etat de texte est prevu avant et apres le signal de donnees et un etat un ou un etant zero suivi d'un etat de bit est prevu pour chaque bit du signal de donnees. Les recepteurs de donnees (102, 103, 104, et Fig. 3) detectent l'etat de bit pour recuperer un signal d'horloge binaire (311) et detecter l'etat un et l'etat zero pour recuperer un signal de donnee NRZ (305, 306). En reponse au signal d'horloge de bit, le signal de donnees NRZ est introduit par decalage seriel dans un registre (312) tandis qu'un signal de donnees de retour charge anterieurement en parallele est sorti par decalage du registre (312) et est applique (314, 315, 316) a la ligne de signaux de donnees de retour.
Abstract:
As shown in Fig. 4 a phase corrected clock signal recovery circuit (150) for multilevel digital signals includes a transition marker generator (200) for generating a narrow width pulse each time a received multilevel digital signal crosses one of the threshold levels between the adjacent logic levels of multilevel signal. Picket fence-like pulse trains are thus formed, the pulses (transition markers) of which correspond to the threshold crossings of the received digital signal. The pulse trains are interspersed with spaces or eye intervals which correspond to the absence of any threshold crossings. Each eye interval additionally corresponds to the time during which each respective bit of digital signal information is transmitted. The rate of occurrence of the pulse trains is substantially equal to the clock frequency of the received digital signal. A phase error detection circuit (400) is operatively coupled to the output of the transition marker generator (200) and to an electronically tune bandpass filter (300) capable of adjusting the phase of the pulse trains. More specifically, the phase error detection circuit (400) includes an up/down counter (410, 411) and adjusts the phase of the clock signal recovered from the pulse trains such that the number of transition markers generated during the high portion of the clock signal equals the number of transition markers generated during the low portion of the clock signal. Thus, selected transitory edges of the pulses of the recovered clock signal are centered at the middles of the respective eye intervals, that is, at the points in time when each respective bit of multilevel digital signal information occurs. This phase corrected recovered clock signal is conveniently applied to appropriate sampling circuitry to enable sampling of the multilevel digital signal at optimum times, that is, at the center of the eye intervals.
Abstract:
Filtre a cristal monolithique bipolaire (200) comprenant des electrodes en bandes mises a la masse (203, 213) entre les electrodes d'entree (201, 21 1) et de sortie (205, 215). Les electrodes en bande mises a la masse (203, 213) possedent une frequence de resonance plus elevee que les electrodes d'entree (201, 211) et de sortie (205, 215), permettent d'obtenir un couplage acoustique ameliore et une capacite (702) reduite entre les electrodes d'entree (201, 211) et de sortie (205, 215), tout en exercant un effet minime ou nul sur les caracteristiques electriques de bande moyenne du filtre. Grace au couplage ameliore, les electrodes d'entree (201, 211) et de sortie (205, 215) peuvent etre espacees d'une distance superieure a la distance possible jusqu'a present dans les filtres a cristal monolithique de l'art anterieur. En outre, des augmentations ulterieures dans le couplage acoustique peuvent etre obtenues en disposant une pluralite d'electrodes en bandes (402, 412; 403, 413; et 404, 414) entre les electrodes d'entree (401, 411) et de sortie (404, 414). Le filtre a cristal monolithique (806) de la presente invention peut etre utilise avantageusement pour le filtrage du signal IF produit dans la partie IF (804) d'un recepteur radio a modulation de frequence (00).
Abstract:
Analog signal processing circuit (10) for detecting engine knock. A sensor (11) mechanically resonant at characteristic engine knock frequencies provides an analog signal (12) related to engine knock and engine background noise. An envelope detector (15) provides the signal envelope (16) of the sensor signal. An integrator means (17) provides an average signal (18) related to the average of the envelope signal while an attenuator (19) and subsequent filter (20) (integrator) provide an integrated and attenuated signal (21) which responds faster to amplitude changes in the envelope signal (16) than the average signal (18). The integrated and attenuated signal level is set below the average signal level for conditions of no-knock. A comparator (23) receives both the average signal (18) and the integrated and attenuated signal (21) and provides an output signal (27) indicating knock detection in response to the amplitude of the integrated and attenuated signal exceeding the amplitude of the average signal. Preferably the knock detection output (27) of the comparator (23) is latched and the comparator is reset by periodic engine pulses (26).
Abstract:
Housing for electronic circuits. The housing is designed to deal with the problem caused by the fact that certain types of circuits are sensitive to acoustic vibrations of the housing and that some electronic components of the circuits need to be protected from the heat generated by other components in the housing. The housing includes a unitary die-cast (11) for enclosing electronic circuits within one or more compartments or cavities (13, 15) adapted to receive circuit boards therein. A cavity (15) includes a post (23) centrally located in the bottom and extending upwardly in the middle of the cavity. A fastening device, such as a screw (37), is used to forcibly affix a rigid but flexible cover (31) onto the housing at the center post. The cast and the cover are made of electrically conductive but acoustically dampening material. When the cover is forcibly affixed to cover the cavity, the cover and the chassis provide an acoustically and microphonically dampened housing for the circuit placed therein. The cast includes a wall (51) separating the compartments, and the wall has a cavity (53) along the length thereof and substantially co-extensive therewith for providing a thermal separation between the compartments whereby the wall acts as a thermal insulator.
Abstract:
A monolithic silicon pressure sensor (10) employing a terminal resistive element (16) is formed in a thin monocrystalline silicon diaphragm (12). The resistive element is a diffused resistor (18) having current contacts (22, 23) at the ends and two voltage contacts (26, 27) located midway between the current contacts and on opposite sides of a current axis defined between the two current contacts. The thin silicon diaphragm (12) has a square shape and is oriented in a (100) silicon surface with its sides parallel to a (110) crystal orientation. The resistor (18) is oriented with its current axis parallel to a (100) crystalline direction and at 45 degrees with respect to the edge of the diaphragm to maximize sensitivity of the resistor to shear stresses generated by flexure of the diaphragm resulting from pressure differentials across the diaphragm. With a current flowing between current contacts (22, 23), a shear stress acting on the resistor (18) generates a voltage which appears at the voltage contacts (26, 27) and which is proportional to the magnitude of the shear stress.