Showing papers on "Keying published in 1987"

Spectral Correlation of Modulated Signals: Part II--Digital Modulation

Abstract: As a continuation of Part I, the spectral correlation function is presented for a variety of types of digitally modulated signals. These include digital pulse-amplitude, pulse-width, and pulse-position modulation, and various types of phase-shift keying and frequency-shift keying. The magnitudes of the spectral correlation functions are graphed as the heights of surfaces above a bifrequency plane, and these graphs are used as visual aids for comparison and contrast of the spectral correlation properties of different modulation types.

Phase diversity techniques for coherent optical receivers

Abstract: In the present state of the art, coherent optical receivers most often operate in the heterodyne mode. Here a photodiode-amplifier combination having bandwidth greater than twice the bit rate ( B ) is needed: indeed bandwidths considerably greater than 2B are preferably employed to ease design of the bandpass filter needed for noise limitation, and to avoid demodulator penalties in some modulation schemes. For the high bit rate systems now coming into service (560 Mbit/s-2.4 Gbit/s), the optical receiver design requirements become more stringent for coherent heterodyne operation. The various modes of "zero IF" operation, however, require only baseband receiver module bandwidth. The options available are either homodyne (phase locked) operation, or phase diversity (multiport) techniques. In this paper, we compare these options, and show that phase diversity techniques are capable of good performance for high bit rate coherent receivers. In phase diversity operation, not only is phase locking avoided, but also the necessary frequency locking does not have high stability requirements. Furthermore, there are advantages in operating with a small frequency offset from zero (of the order of 1 percent of the bit rate). An experimental receiver has been operated at 320 and 680 Mbit/s, demodulating both amplitude shift keying (ASK) and differential phase shift keying (DPSK). Operation with FSK is also possible. Sensitivities so far achieved of -47.5 dBm (320-Mbit/s ASK) and -42 dBm (680- Mbit/s ASK) with limited local oscillator power are capable of substantial improvement when higher power local oscillators and lower noise receive modules become available. Demodulation of DPSK at 320 Mbit/s has also been achieved and shows a measured receiver sensitivity improvement of over 4 dB over ASK at the same bit rate and local oscillator power. These practical results show clearly that phase diversity is a very realistic option for high bit rate systems.

Heterodyne transmission of a 560 Mbit/s optical signal by means of polarisation shift keying

Abstract: Experimental results for a 560 Mbit/s optical heterodyne system using polarisation shift keying are presented. It is demonstrated that this modulation technique provides up to 3dB gain compared to ASK modulation.

Correction to "Design and Experimental Results for a Direct-Sequence Spread-Spectrum Radio Using Differential Phase-Shift Keying Modulation for Indoor, Wireless Communications"

Abstract: We report on our design and measurements that have been made for a direct-sequence spread-spectrum radio using differential phase-shift keying modulation for a wireless PBX. We describe the design and implementation of a transmitter and a receiver using a surface acoustic wave (SAW) filter matching the spread-spectrum code of a user. The receiver performance is within 1 dB of the theoretical performance of a differential phase-shift keying (DPSK) receiver in the presence of additive white Gaussian noise. We also show receiver performance in a multipath fading indoor environment with multipath fade notches of up to 50 dB depth. The indoor channel multipath fading can be overcome by using an equal gain diversity combiner which is suitable when DPSK modulation is used. We confirm that the indoor mean power level attenuation follows the inverse fourth power of the distance. Also, we investigate the multiple-access capability of the system by introducing an interfering transmitter with a different spread-spectrum code sequence.

A Novel Anti-Multipath Modulation Technique DSK

Abstract: This paper describes a new modulation technique called DSK (double phase-shift keying) which shows an interesting antimultipath feature over mobile frequency-selective fading environments. The effect of this technique is shown for various multipath channels by detection waveform and theoretical bit error rate (BER) analyses. A result obtained from a laboratory test is also presented. In the latter part of the paper, a generalized form of DSK is described and extensive investigations are made so as to clarify the anti-multipath effect of DSK in view of the diversity concept and to further explore the possibility of a narrowband scheme. A major result shows that this technique can give a kind of diversity effect which is implicit in the arrival of signals via multiple paths with different delays.

An ARQ Scheme with Memory and Integrated Modulation

Abstract: In this paper, the integration of the modulation operation in an automatic-repeat-request scheme, using error-detecting codes, is analyzed. A new protocol is described, in which the modulation operation facilitates the recovery of the transmitted code word. The results show a net improvement in the throughput of the automatic-repeat-request scheme, particularly for mean and high error-rate conditions. Continuous-phase-frequency shift keying modulations, which present a low bandwidth occupancy, are particularly considered.

Trellis-Coded Modulation for Fading Channels

Abstract: In proposed communication system, digital signals transmitted efficiently over fading channel by combination of trellis coding and multiple-phase-shift keying with addition of asymmetry to signal set. Coding and modulation schemes not designed separately as in previous systems but integrated to yield bandwidth-efficient modulation and forward-error-correction coding. Helps to satisfy need for reliable high-quality transmission of voice and data between land-mobile units via satellites, where limitations of power and bandwidth imposed simultaneously. Also applicable to ionospheric communications between fixed or mobile units.

Differential phase shift keying modulator

Abstract: A differential phase shift keying (DPSK) modulator utilizes time-domain filtering techniques The DPSK modulator includes a data scrambler which receives a serial digital data input signal and generates an output signal representing the dibit value of the serial input sequence The dibit signal is differentially encoded and then provided to a history generator which produces phase modulating vectors utilizing pulse density modulation (PDM) The carrier waveform is then modulated utilizing the modulating vectors to generate a DPSK output signal

Improvements in and relating to framing for windows or other panelling

Abstract: In order to render framing for panelling, especially for a window pane (19), easier to fix and yet more secure we provide first (9) and second (3) extrusion members arranged to embrace opposite sides of support means (1) for the frame, and provide mutually engagable keying means (23) between the extrusion members to allow interconnection in one direction but to resist separation in the other direction. The keying means conveniently takes the form of barb like projection and recess means.

Method and circuit arrangement for converting a measured voltage into a digital value

Abstract: A measured voltage is converted into a digital value according to the follow-up principle. A compensation signal is added to the measuring signal so that the mean value of both signals becomes zero. The compensation signal is formed from at least two auxiliary compensation values which are each a square wave signal having a fixed frequency and a keying ratio which is adjustable independently of the other square wave voltage. The keying ratios are varied or adjusted so that the compensation signal compensates the measured signal. In order to achieve this the value deviating from zero of the sum of the measured signal and the compensation signal is integrated, converted into digital values, and supplied to a PI-or PID-control circuit which controls in a closed loop manner the keying ratios of the square wave signals. The I-value of the PI- or PID-control circuit serves as a measure of the measured voltage.

Synchronous data recovery in RF communication channels

Abstract: Synchronous data recovery schemes over narrowband radio-frequency (RF) data channels based on phase-shift keying and frequency-shift keying are described. Experimental systems were breadboarded with 50-MHz analog RF circuits fabricated using a 2-/spl mu/m gate double-poly CMOS technology. Most circuits are developed for quadrature RF data transceiver applications in the 50-MHz commercial RF band, and an experimental frequency-aided Costas loop exhibits a 1-mV input sensitivity with an on-chip voltage-controlled oscillator. Developed circuits are applicable to general phase-locked-loop systems for data and clock recovery in VLSI chips. The 50-MHz quadrature RF section occupies 0.55 mm/SUP 2/ and consumes 150 mW with a 5-V supply.

Device for slowing down traffic, of the speed bump type

Abstract: The slowing-down device is formed by means of precast concrete slabs 11, 12, 13 which are assembled by keying, preventing any relative vertical displacement of a slab with respect to its neighbouring ones. The keying may be carried out by means of the shape or by means of additional keying parts.

Circuit arrangement for interrogating the state of at least one keying device and for supplying an indication to an indicating device

Abstract: In order to interrogate the state of at least one keying device (T2) by means of a microcomputer (EMC) and to supply an indication by means of an indicating device (LED2), which is allocated to the respective keying device (T2), for the case when the relevant keying device (T2) has been operated, the respective keying device (T2) and its indicating device (LED2) are connected via a single line (L2) to a single microcomputer connection (A3) which can be controlled cyclically and repeatedly into a high-impedance interrogation state and into a signal output state which carries a specific potential (earth potential) with a low impedance.

Phase adjusting circuit for keying signal

Abstract: PURPOSE:To form a variable delay circuit with an inverter to an integrating circuit and to eliminate the influence of temperature variation by independently adjusting the leading edge and the trailing edge of a keying signal and by making the said edges coincide with those of a video signal to be extracted. CONSTITUTION:A keying signal (a) by which an image signal from three-primary color signal input terminals 3-5 is processed is outputted from the key generator 6 of the titled circuit, and the signal is supplied to the first variable delay circuit 12. The circuit 12 gives the signal (a) a delay in an amount that its trailing edge coincides on the rear end of an object-image signal (f), and the output signal is made a signal (b) which is delayed by the second delay circuit 13 so that its leading edge coincides on the front end of the signal (f). The output from the circuit 13 is made a signal (c), which is supplied with the signal (b) outputted by the circuit 12 to a multiplier 14. The multiplier 14 adjusts the phases of the said signals and generates a signal (d) to supply it as a switching pulse to an analog switch circuit 8. The circuits 12 and 13 are of such construction that two pairs of an integrating circuit and an inverter to invert the output thereof are longitudinally connected. The constitution of the titled circuit is is thus simplified.

Automatic stop code insertion feature for a word processing apparatus

Abstract: A word processing apparatus is capable of detecting the entry of a function or operation during keying of the text into memory, which requires an operator intervention such as the changing of the print element or the changing of the format parameters. Upon the detection of that condition, an automatic operation is invoked by the software process to insert into the text string and memory a stop code. This insures that the playout of the stored text will be interrupted to permit the operator to perform the same or related operation at the same relative position in the text.

Keying signal generating circuit

Abstract: PURPOSE:To eliminate necessity for the operation of a resistor for slice-level adjustment in accordance with the background color and the operation of a switch to change the background color and to improve the operability of the titled circuit by automatically generating a keying signal for a chroma key circuit. CONSTITUTION:The peak values of the color difference signals R-Y and B-Y from a TV camera coming from input terminals 1 and 2, are supplied to peak value detecting circuits 13 and 14, and the peak values at the positions where the detection phases are set are detected by means of the pulse of one field period from a detection phase setting circuit 15. The peak value detection signals from the circuits 13 and 14 are attenuated with a constant ratio by level attenuators 16 and 17 to align the variance of the signals due to shading, and then the signals are held by S/H circuits 18 and 19. The peak values of required fields from the circuits 18 and 19 and the inputted signals R-Y and B-Y are processed by differential amplifiers 20 and 21. The outputs from the amplifiers 20 and 21 are supplied to logical converters 22 and 23, and the logical keying signals that vary with the duration of color difference signals related to the background and with that of an object are outputted from an adder 11.

Structural keying means

Abstract: A structural metal member which may form part of a lintel or beam for example has plaster or mortar keying means (13) formed without substantial removal of metal. Each keying means has a central slot (14), the borders (15, 16) of which are deformed out of the general plane of the metal to protrude in opposite directions, forming an obliquely angled passageway (20) to guide settable material such as mortar or plaster through the keying means. Preferably, adjacent slots are parallel but with the borders deformed in alternate directions to provide maximum keying. The deformed borders (15, 16) then provide additional stiffness in the direction of alignment of the keying means.

Keying signal reproduction circuit for scramble receiver

Abstract: PURPOSE:To reproduce and output a keying signal with almost no delay compared with its original signal, by using a PLL circuit including a phase comparator, an LPF, and a horizontal oscillator, etc, and an output circuit including a monostable multivibrator, etc CONSTITUTION:The tuner output of a scramble receiver is impressed on the input terminal 1 of a keying signal reproduction circuit, through a keying signal BPF, and is detected at an AM detection circuit 2, and through an LPF3, it is waveform-arranged at a comparator 4 The output of the comparator 4 is processed at the PLL circuit having the BPF function of narrow band, and consisting of a phase comparator 5, an LPF6, a horizontal oscillator 7, and an output circuit 8 which controls the circuit 5, etc, and it is changed to a reproduction keying signal having the same phase as its original signal, and receiving few disturbance from a video signal, or an adjacent channel Furthermore, almost the same pulse width as that of its original signal is attached by the monostable multivibrator built in the output circuit 8, and the keying reproduction signal without alterative delay from the circuit 8 can be outputted

Warning device for using condition of vdt

Abstract: PURPOSE:To contribute to prevention of troubles of necks, shoulders and arms as well as the radiation troubles, etc. by comparing the stored information with the registered reference value in accordance with the using conditions and then delivering a warning to the user for a rest. CONSTITUTION:A user supplies a reference value through a keyboard 2 against generation of warning to the limit value of the continuous working time and the upper limit value of keying frequency per unit time. The input reference value is stored in a reference value memory means 8 via a reference value register means 5. When the keying operation is started through the keyboard 2, the key input information is supplied to a key input conversion means 8. The means 4 uses the signal of a timer 3 to convert the key input information into the keying frequency per unit time at a job starting time point and in a working mode. The output of this conversion is stored in a memory means 6 for key input state information. At the same time, a comparison/decision means 7 compares the reference value of the means 8 with the key input state information of the means 6 to check whether or not the present working time point exceeds the reference value from the job working time point and whether or not the keying frequency per unit time exceeds the reference value respectively.

Keying apparatus for connecting a printed wiring assembly to a backplane structure

Abstract: A keying apparatus is provided including a key support structure having a plurality of protrusions which mate with a corresponding plurality of recesses formed in an edge surface of a printed wiring assembly. The key support structure includes a mechanism for permanently latching the key support structure at a predetermined location on a mounting rail adjacent a backplane interconnect. The printed wiring assembly is conveniently removable from the key support structure. This keying apparatus assures that when a printed wiring assembly is removed from the key support structure at a predetermined location on the rail, only the proper printed wiring assembly may be reinserted at that location.