Showing papers on "Keying published in 1984"

Differential detection of Gaussian MSK in a mobile radio environment

Abstract: Minimum shift keying with Gaussian shaped transmit pulses is a strong candidate for a modulation technique that satisfies the stringent out-of-band radiated power requirements of the mobil radio application. Numerous studies and field experiments have been conducted by the Japanese on urban and suburban mobile radio channels with systems employing Gaussian minimum-shift keying (GMSK) transmission and differentially coherent reception. A comprehensive analytical treatment is presented of the performance of such systems emphasizing the important trade-offs among the various system design parameters such as transmit and receiver filter bandwidths and detection threshold level. It is shown that two-bit differential detection of GMSK is capable of offering far superior performance to the more conventional one-bit detection method both in the presence of an additive Gaussian noise background and Rician fading.

High-Level Modulation and Coding for Nonlinear Satellite Channels

Abstract: Currently, 4-PSK is the prevalent modulation format in use for digital satellite communications. To improve bandwidth efficiency, 8PSK could be used instead, but a higher power would be needed; to improve power efficiency, error-correcting codes could be used, but at the expense of a larger bandwidth. Recently, Ungerboeck [1] has proposed a class of codes in which a constellation of 2M signals is used to transmit information at the rate of log_{2} M bits per symbol, and has shown that coding gains of up to several decibels can be achieved on the additive white Gaussian noise (AWGN) channel with no increase in bandwidth occupancy and a relatively small added complexity. Thus, these codes seem to be particularly attractive for application in the band-limited environment typical of satellite communication systems, provided that the performance gain that they provide on the AWGN channel is not lost over a satellite channel. The goal of this work is to assess the performance of this class of codes when used to transmit 3 information bits per symbol on a band-limited, nonlinear satellite channel. Three modulation formats are considered, namely 16-PSK, 16-QAM, and a 16-ary amplitude-phase keying scheme with two amplitude levels. It is found that 16-PSK outperforms the two other modulation formats, and that the use of these codes can provide a substantial performance improvement even on a satellite channel.

Bit Error Rate Evaluation for Spread-Spectrum Multiple-Access Systems

Abstract: A unified method for approximating and bounding the average bit error probability for spread-spectrum multiple-access communication systems is presented. Various forms of direct-sequence spreadspectrum modulation are considered including binary phase-shift keying, quadriphase-shift keying, and minimum-shift keying. The analysis of the multiple-access interference makes use of a number of moments sufficent to evaluate the error probability with a high degree of accuracy. A computationally efficient algorithm for computing the moments is also given. The subsequent transformation from the moments to the average bit error probability is carried out by means of Gauss-type numerical integration formulas. It is shown that the same approach can be exploited for evaluating two classes of upper and lower bounds on the bit error rate. Finally, some results and comparisons are reported.

Locating Data Frames in Direct-Detection Optical Communication Systems

Abstract: The maximum-likelihood rule for locating a frame-synchronization pattern in a direct-detection optical communication system employing either Q -ary pulse-position modulation or on-off keying is identified. We show that equivalent performance for the simple correlation and postdctection-correlation rules used in practice can require substantially more than a 3 dB increase in signal power over that required using the maximum-likelihood rule.

Frequency Hopping with Multiple Frequency-Shift Keying and Hard Decisions

Abstract: The performance of frequency-hopping systems with multiple frequency-shift keying and hard decisions is determined for operation against optimal partial-band jamming. A receiver that eliminates the potential advantage of optimally placed jamming tones is proposed. The effects of Reed-Solomon, binary block, and convolutional codes are analyzed. Concatenated codes with hard and soft decisions available to the outer decoder are examined. Continuous-phase frequency-shift keying with limiter-discriminator demodulation is shown to offer potentially improved performance in frequency-hopping systems.

Keying system for electrical connectors

Abstract: First and second connector housings are keyed to each other by means of identical parts which can serve as either keys or keyway plugs. The identical parts are produced as a continuous strip comprising a carrier strip from which the parts extend at spaced apart intervals. In the practice of the invention, a section of strip is used which has a number of parts thereon equal to the number of keying positions in the connector assembly. One or more of the identical parts are removed from the strip and assembled to the first housing. Thereafter the remaining parts on the strip are aligned with the keying positions on the second housing and assembled to the second housing. The carrier strip can then be separated from the remaining identical parts.

Spread spectrum synchronizing loop for spreading code modulated by code shift keying

Abstract: Sequence Inversion Keying (SIK) which inverts the signs of the spreading codes, has been used mainly for conventional Spread Spectrum (SS) modulation. Since SIK modulation is essentially not suited to multilevel transmission which enables us to decrease inter-channel interference, the inter-channel interference begins increasing significantly if we try to improve the interference characteristic or the multiplexing capability. to improve the performance of the SS, code shift keying (CSK), which is a kind of multilevel modulation, of the spreading code has been proposed recently. However, there have been no reports of a synchronous technique for CSK at the receiver. This paper proposes two types of new synchronizing loops for CSK of SS and their performances are evaluated through experiments. the loops for a 2-phase and 4-phase CSKs are treated in the experiments. Both show good synchronizing characteristics and the synchronizing loops which show little performance deterioration despite the increase in the number of phases, are obtained. the proposed schemes compare favorably with the conventional SIK synchronizing loops and give practically sufficient results.

Differential phase shift keying demodulator

Abstract: A differential phase shift keying demodulator in which a signal modulated by differential phase shift keying is compared with the modulated signal delayed an integral number times as much as a period of the carrier wave of the modulated signal and shorter than a transmission period for one bit of the modulated signal.

A method of scheduling a meeting among several terminal users

Abstract: U A method of scheduling a meeting among terminal users who are provided with calendaring applications for storing and retrieving timed and dated events, consisting in presenting to a meeting scheduler with a prompting screen with blanks for keying in desired times and dates, and prospective attendees, and based on keying to this screen comparising with the prospective attendees' calendars of events. The result of the comparison is an option list which is presented to the scheduler for selecting an available meeting time. Based on a selection from the option list, a meeting notification screen is built for transmitting to the attendees.

Digital-based phase shift keying modulator

Abstract: A digital-based phase shift keying modulating device is disclosed. A phase code command signal is applied to an exemplary bi-phase shift keying modulating (BPSK) device designed in accordance with the present invention to phase reverse by 180° the output signal produced by the device. The exemplary BPSK modulating device is capable of producing an output signal of either triangular or sinusoidal shape. A preferred embodiment of the exemplary device is implemented by using a single exclusive OR logic gate in conjunction with a frequency synthesizer, which is comprised of an accumulator, an output register, and a group of exclusive OR logic gates. The modulator device has a variety of applications in digital communication systems such as, for example, ground-based and spacecraft communication systems. The disclosed BPSK modulating device is particularly useful in spacecraft data link communications systems wherein weight, volume, and power consumption are at a premium.

Apparatus for scrambling and descrambling communication signals

Abstract: Of the scrambling systems used in CATV and direct satellite broadcasting systems, the invention pertains to the transmission of a keying signal for demodulation. The keying signal, as a carrier wave displaced 90° in phase from a picture carrier wave, is superimposed on the conventional sync signal suppression period with no sound carrier wave being processed, thereby avoiding the generation of buzzing noise which would occur when the keying signal is superimposed on the sound carrier wave. With this invention, not only can the generation of buzzing noises be eliminated, but also even in multiplex sound systems the sound signal can be transmitted without the sound quality being adversely affected. Also, no synchronizing signal can readily and easily be detected and, therefore, subscription TV programs can not be viewed by unauthorized persons.

Data terminal device having radio calling function

Abstract: PURPOSE:To attain suitable management of a terminal device and the efficient operation of line, by providing a sound coupler to a portable terminal device, equipping a radio calling mechanism and calling out the terminal device in radio as required for transmitting information. CONSTITUTION:A main body 1 contains a data input device 11 in a storage section 5 and is formed into an attache case, is of portable type and used for the individual sales activities such as home visit. Further, in case of the sale to a credit card possessor and the payment of service charge, a cover 2 of the main body 1 is opened, a data input device 11 is extracted from the containing section 5, and the operation of a part of information preset on the credit card and the data keying through key operation is performed. Couplers 6, 7 of a sound coupler section 3 are coupled with a handset 71 of a telephone set 70 and the data exchange is performed between the main body 1 and the telephone set 70 via the sound coupler section 3 ahead the keying, and the transmission/ reception of information is attained between the main body 1 and a computer center 75.

Design of a Convolver-Based Packet Voice Spread Spectrum System

Abstract: A spread spectrum system for the transmission of packet voice has been developed. Using a continuously variable slope delta (CVSD) modulator, speech signals are encoded at 16 kbit/s. The encoder output data stream is split into blocks of 1024 bits, which are t ransmitted in bursts at a data rate of 84 kbit/s. For data representation binary code shift keying (CSK) is employed. The spreading modulation is direct-sequence (DS) with a chip rate of 21.4 MHz. The receiver design is based on the application of two SAW elastic convolvers to programmable matched filtering of the continuously changing code patterns. The alignment of received signal and local reference is accomplished by means of an 11-bit preamble preceding each data packet. Experiments are in good agreement with theoretical predictions, measures of performance being the probability of burst loss and the bit error probability in an additive white Gaussian noise channel.

60-GHz Integrated-Circuit High Data Rate Quadriphase Shift Keying Exciter and Modulator (Short Papers)

Abstract: An integrated-circuit quadriphase shift keying (QPSK) exciter and modulator have demonstrated excellent performance directly modulating a carrier frequency of 60 GHz with an output phase error of less than 3 degrees and maximum amplitude error of 0.5 dB. The circuit consists of a 60-GHz Gunn VCO phase-locked to a low-frequency reference source, a 4th subharmonic mixer, and a QPSK modulator packaged into a small volume of 1.8x2.5X 0.35 in. The use of microstrip has the advantages of small size, light-weight, and low-cost fabrication. The unit has the potential for multigigabit data rate applications.

Device for two-way radio traffic

Abstract: The invention relates to a device for two-way radio traffic using the time division multiplex method for signal transmission from and to the subscriber. A device of this type is intended to be simple in its design and to guarantee interference-free function. The invention provides for this purpose that a digital microprocessor controller (MPS) is allocated to the radio unit (FG) for analog signals on the AF side with analog-digital converters (5, 8) on the input side and digital-analog converters (7, 10) on the output side and with means (storage and control elements) for time compression of the signal to be transmitted and for expansion of the received signal and for soft keying of the transmitter and synchronisation of the radio unit (FG) to an already operating distant station.

Digital transmitter simulator

Abstract: A modulated VLF signal source has the capability for providing radio sign suitable for performance testing and operator training relative to VLF digital data receiving systems. A number of separately proven components are utilized to implement a relatively low cost, reliable compact and easily transportable system. A digital modulator is driven through suitably adapted microprocessor circuits by selective information stored on floppy diskettes. Operator input commands actuate the modulator to generate representations of data in the continuous shift keying, frequency shift keying, or minimum shift keying output modes to provide a modulated VLF output which can be received by several receive systems. Prolonged data transmissions can be produced by merely selecting the appropriate floppy diskettes to initiate the desired modulated sequences.

Keyed DC stabilization system with protection from error introduction during vertical sync interval

Abstract: DC stabilization system for a color TV receiver includes three control loops, each including a keyed comparator (35, 31, 33) for comparing a respectively different one of a set of blue, green, and red color signals with a common reference voltage (RV) during keying periods determined by line rate keying of «backporch» timing pulses (K). The output of the keyed comparator (35) responding to the blue signal adjusts the DC level of a luminance signal component used in color signal formation. The output of the keyed comparator (33) responding to the red signal adjusts the DC level of an I color-difference signal component used for color signal formation. The output of the keyed comparator (31) responding to the green signal adjusts the DC level of a Q color-difference signal used for color signal formation. The line rate keying pulse source (50) is subject to field-rate blanking to prevent comparator keying during significant portion of received signal's vertical sync interval.

Error Correction during Text Entry with Word-Processing Systems

Abstract: To answer questions related to keying errors and error corrections, performance data were collected from typists as they keyed text into a simulated word-processing system. Data are presented on the frequency of error detection, the amount of time spent correcting errors, the number of characters erased per error correction, and the types of errors corrected. Comparisons are also made between corrected and uncorrected errors.

Method for displaying an annotated calendar

Abstract: A method for displaying on a display device (1) a monthly calendar annotated with exterior current day narrative notes (7) and embedded abbreviated notes. Notes related to a specific day can be prepared on a time independent basis by calling, and keying to, a dayly file (4) for the specific day. In addition, keying is used to distinguish between normal and special notes which are to be later displayed in abbreviated and narrative forms, respectively. Upon the occurrence ofthe specific day and the calling of a calendar screen, the notes are displayed along with an updated calendar. Special notes appear as narrative footnotes (7) and normal notes appear in abbreviated form with the day indications. In the absence of further day screen calling and keying, the footnotes changed on a daily basis, while the abbreviated notes remain fixed.

Synchronization in a Spread Spectrum Communication Modem based on SAW Convolvers

Abstract: This paper describes the synchronization process in a spread spectrum burst communication system which is based on the application of surface acoustic wave (SAW) convolvers. The data modulation is binary code shift keying (CSK). For spectrum spreading pseudonoise (PN) direct-sequence (DS) is employed. The performance of the receiver synchronization in the presence of additive white Gaussian noise is analyzed, the measure of performance being the probability of burst loss. Special attention is paid to the effect of code autocorrelation sidelobes on the detection of the synchronization preamble, and a strategy for the elimination of this effect is considered. Theoretical performance is compared with some experimental results obtained with a test modem.

Digital video special effects generator

Abstract: Keying signals controlling the switching from a first to a second available signal source are available at the output of a comparator. The input of the comparator receives the output of a presettable up/down counter. The comparator has a first reference input which receives a first reference count (generally one half of the maximum count) at which the counter is switched from up to down operation. The second reference input receives a clip reference count which is less than the first reference count. If the oscillator oscillates at a frequency which is a predetermined multiple of the line frequency, and if the counter is reset at the line frequency, the keying signal will cause a vertical bar containing the picture information from the second signal source to appear within the remaining display which corresponds to the first signal source. The position of the bar can be varied by changing the preset input of the main counter, while its width can be varied by changing the clip reference. Squares can be generated by combining keying signals derived from horizontally synchronized and vertically synchronized apparatus of the above described type in an AND circuit. Many other shapes can be generated by changing the preset inputs and/or the clip reference input of either or both the horizontally and vertically synchronized apparatus. Basic shapes other than bars can be created by use of other inputs to the comparator (e.g. ramps) in conjunction with other comparator settings.

Brake system comprising at least one floating brake disc

Abstract: The braking system comprises at least one brake disc (26, 36) slidably mounted axially on a hub (22) through keying means (30,32). According to the invention the braking system comprises an integrated forced lubrication device (60) of the keying means (30, '32) formed by two sealed chambers with variable volumes connected together through said keying means (30, 32) .

Code setting system of label issuing machine

Abstract: PURPOSE:To simplify the code setting operation, by performing the input operation of the number of digits of a code for subclassification and the depression of a code set key only once to set the code of goods in case of the same classification. CONSTITUTION:When the code of upper digits are inputted to a keying register 2 with a ten-key switch 1 and a code setting key 8 is depressed twice during the set time of a timer 9, the code for classification which is contents of the register 2 is supplied to an upper register 5 by the output of an AND gate 14. Next, the code for the subclassification is inputted, and the key 8 is depressed once, and the timer 9 is driven by the output pulse, and an FF 12 is set. Its time-up signal is supplied to a lower register 6 through an AND circuit 4. The codes of these upper and lower registers 5 and 6 are sent to a code printer 7a and upper and lower digits of a code display device 7b and is printed on a label form and is displayed on a CRT.

Apparatus and method for generating multi-digit codes

Abstract: A radio apparatus, particularly a personal transceiver, includes a manual keypad for keying numerical data, read and write function keys, and a data processor. The processor is programmed to store keyed numerical data representing part of a multi-digit destination code into a storage location of a read-write memory in response to operation of the write function key and store keyed numerical data representing the address of the storage location. The stored part-destination code data are retrieved in response to successive operation of the read function key and the keyed keying numerical data representing the address of the storage location. In response to subsequent operation of the keypad keying numerical data representing an additional digit, the latter is appended to the part-destination code read from the memory to complete a full destination code.

Constant width burst gate keying pulse generator

Abstract: OF THE DISCLOSURE A keying pulse generator for a color television burst gate provides a gutting pulse in response to horizontal synchronizing pulses when present and in response to horizontal retrace pulses when sync pulses are absent. A timing circuit is provided to maintain a constant width keying pulse independent of video signal condition and receiver operating characteristics.

Finger attack speed detection system

Abstract: PURPOSE:To detect the finger attack speed stably at a high accuracy with a compact construction by employing a digital arithmetic circuit equivalent to a time constant circuit with a resistance and a capacity. CONSTITUTION:When a switch S1 is closed in response to finger attacking, a pulse corresponding to the keying timing is outputted to a data selection circuit 6 through an FF1, an FF3, a NOT circuit 4, an AND gate 5 and the like to select a numeral N which is memorized into a memory circuit 7. The multiplication of the memory contents by a specific coefficient with a multiplier 8, the selection of results of the multiplier 8 with the circuit 6 and the memory of selected output with the circuit 7 are done circularly to perform a digital computation equivalent of a time constant circuit with a resistance and capacity. The results of the computation are memorized into a memory circuit 9 whose latching is controlled with the FF2 for detecting the closing of a switch S2 delayed from the switch S1 in the keying and detected depending on the keying speed. Thus, the detection of the finger attack speed can be done stably at a high accuracy with a small LSI structure requiring none or such resistance, capacity and the like.

Sonarlink - A Deep Ocean High Data Rate, Adaptive Telemetry System

Abstract: The design, implementation, testing, and uses of a high data rate, adaptive deep ocean acoustic telemetry and communications system are discussed. Digital and analog information may be transferred independently or simultaneously from depths in excess of 20,000 feet. Frequency Modulation (FM), Frequency Shift Keying (FSK), Differential Phase Shift Keying (DPSK), and Quadrature Amplitude Modulation (QAM) are combined to insure the highest data rates commensurate with acoustic transmission conditions. A microprocessor based controller permits an ultra-low power standby mode, fail-soft recovery, Built-In-Test Equipment (BITE), and multiple fall-back levels as well as providing the user with the ability to dynamically alter many of the operating parameters to compensate for varying environmental conditions.