Showing papers on "Continuous phase modulation published in 1979"

A Comparison of Modulation Techniques for Digital Radio

Abstract: This paper describes and summarizes the characteristics of the modulation techniques most applicable to digital radio. The modulation techniques discussed are on-off-keying (OOK) with coherent and noncoherent detection, quadrature amplitude modulation (QAM), quadrature partial response (QPR), frequency-shift-keying (FSK) with noncoherent detection, continuous phase FSK (CP-FSK) with coherent and noncoherent detection, minimum-shift-keying (MSK), binary and quaternary phase-shift-keying (BPSK, QPSK) with coherent and differentially coherent detection, offset-keyed QPSK (OK-QPSK), M -ary PSK with coherent detection ( M = 8, 16 ), and 16-ary amplitude and phase-shift-keying (APK). Functional descriptions of these schemes are provided and their performance is compared in a series of tables summarizing the results of the literature of the past 20 years. The modulation schemes are compared with respect to ideal (white Gaussian noise) performance, spectral properties, signaling speed, complexity, and the effects on performance of interference, fading and delay distortion.

QPSK Suppressed carrier with rotating reference phase

Abstract: A suppressed carrier signal is offset quadrature phase shift key modulated so the reference carrier phase is stepped 90° in the same direction in synchronism with sequential bits of a serial data stream and is further bi-phase modulated in response to the binary data source having first or second binary values. A coherent receiver responds to the suppressed carrier signal to establish an equivalent sequence of stepping reference phases at the carrier frequency. The reference phases synchronously rotate in 90° increments in the same direction as the suppressed carrier reference, being permitted a four-fold initial phase ambiguity (0°, 90°, 180°, and 270°). The rotating reference phase is compared in a bi-phase manner with the appropriate component of the suppressed carrier signal to derive sequential d.c. polarities indicative of the binary bit values during the sequential binary data bits.

Method of and apparatus for transmitting and recovering offset QPSK modulated data

Abstract: Bit timing references are derived at a receiver for a carrier modulated by OQPSK. A carrier is transmitted with a constant reference phase modulation during a first interval. During a subsequent, second interval the carrier is transmitted with rotational phase modulation representing binary bit values so that orthogonal components phase modulate the carrier with a predetermined bit sequence. A receiver responds to the constant phase modulated carrier to lock the frequency and phase of a phase lock loop oscillator of a carrier recovery loop. Synchronization at the receiver is achieved in response to a reception of the rotational phase modulation, while maintaining the frequency and phase lock. A carrier recovery loop of the receiver is activated to a decision directed operation after bit synchronization has been achieved. Decision directed operation is achieved by sampling and comparing components derived in orthogonal channels of the carrier recovery loop while the receiver is responsive to the rotational phase modulation. The bandwidth of a filter used in achieving bit synchronization is reduced after there has been a decay of transients in the carrier tracking loop resulting from a transition between locking of the loop and initiation of the decision directed operation. Then the bandwidth of a filter in the carrier tracking loop is adjusted as a function of the quality of the received rotational modulated suppressed carrier.

Combined coherent frequency and phase shift keying modulation system

Abstract: A system of modulation and demodulation for the transmission of binary data in the presence of multipath. The binary data modulates the phase of the carrier and the same binary data, after a delay of "δ" bits, also modulates the frequency of the carrier. Following reception, the binary data is obtained either by frequency demodulation or by a method of coherent phase shift demodulation wherein the mark or the space frequency is selected for detection of each bit in accord with the bit received "n" bits previously. The system selects between the demodulation methods to obtain one which operates satisfactorily in the instant electromagnetic environment.

Carrier regeneration circuit for polyphase modulation system

Abstract: An n (=8, 9)-valued polyphase modulation system having circuit construction for carrier regeneration in which not only correct phase demodulation is effected but also any AM components of the regenerated carrier wave are effectively compensated for and in which the decision circuit is adapted to produce a signal output having no phase ambiguity which is coupled to a π/4 phase modulator unit of the carrier generator to serve as a drive signal therefor.

Method and apparatus for quadriphase-shift-key and linear phase modulation

Abstract: A submultiple (30Fl) of an S-band transmitter output frequency (240Fl) is divided equally between a linear phase modulation branch and a QPSK modulation branch. The linear modulation branch includes a multiplier (X7) to increase the carrier frequency to a level (210Fl) which, when combined with the carrier in the QPSK branch in an up-converter (utilizing a mixer at the input thereof followed by a bandpass filter), produces the transmitter output frequency. This allows the QPSK modulator to operate at one-eighth of the output frequency where repeatable and precisely controlled modulation can be easily achieved. This also allows linear phase modulation at one-eighth the output frequency where low modulator deviation and good linearity can be easily maintained.

A new modulation scheme for multitransmitter simulcast digital mobile radio communication

Abstract: Many mobile radio communication systems require digital siganling simultaneously from multiple transmitters from the viewpoints of efficient frequency utilization and simplified receiver construction. This paper describes a new modulation scheme in order to realize a simulcast digital transmission. In this method modulation signal is made by superimposing a sinusoidal wave on an ordinary rectangular digital wave. When Manchester-coded type signal is used, the frequency of the sinusoidal wave is twice as much as that of the original bit-rate and the relative phase difference between the two waves is different at each base station. In order to clarify the feasibility of this technique, experimental simulation tests are performed on 900-MHz band in two transmitter construction. It is proved that this modulation scheme does not only give the same amount of the improvement effect on the digital signaling on an overlapped area, but also makes the allowable carrier frequency drift several times lager than that of the carrier frequency offset strategy.

On the Reduction of Hardware in Digital Modulators

Abstract: A Possible simplification of digital modulation (carrier multiplication with sine or cosine signal) is discussed. Using the fact that samples of a sine (or cosine) function are periodic under certain circumstances, a novel implementation is proposed. Depending on the ratio of sampling and carrier frequencies this implementation can lead to a reduction of cost in comparison with usual methods of implementation. The paper presents a systematic search for the cases where a certain amount of saving in hardware can be achieved.

Method and apparatus for synthesizing a modulated carrier to reduced interchannel interference in a digital communication system

Abstract: The modulated carrier in a frequency-multiplexed digital communications system is synthesized with each band of the modulated carrier derived from data stored in a read-only-memory. The carrier envelope shape is selected to reduce the sidebands of the digitally modulated carrier and thus reduce interchannel interference. The read-only-memory digital output is applied to a digital-to-analog converter for synthesis of an analog voltage, representing the modulated sinusoidal carrier, having reduced higher frequency content, without the necessity for use of a costly, narrow-bandpass filter.

Broadband Phase Modulator with a Branch Line Coupler - Transformer

Abstract: The paper presents a way and results of the computer aided optimization of the phase modulators to attain almost flat phase shift about the centre frequency. the modulator consists of the branch line coupler-transformer and of PIN diodes. There are many parameters of the circuit, namely structure and transformation coefficient of the coupler, lengths and characteristic impedances of the lines with diodes which oan be adjusted to attain optimum characteristics of the modulator. A program of the analysis and synthesis using the matrix techniques has been developed. Computs, tion results have shown that one can made the phase modulator for 180 and 90 degrees phase shifts with the deviation not greater than 2 degrees in the 15 per cent operating frequency band. Experimental results have shown a good agreement with the developed theory.

A Low-Cost Continuous L-Band Phase Shifter/Attenuator for Low Power Applications

Abstract: A simple continuous phase shifter and attenuator module for L-band applications is presented. The phase shift and the attenuation can be continuously varied over 360°and 20 dB, respectively. The phase shifter is a hybrid unit, consisting of a 180° discrete PIN diode phase shifter and a novel 180° continuous varactor diode phase shifter. Both phase shlfters are optimized for small frequency variations, which are less than 10° over a 7% bandwidth (1.5 to 1.7 GHz) at all phase shifts. The attenuator is a 3 dB hybrid, loaded by two tuned PIN-diodes. The interaction between phase shift and attenuation is negligible at the center frequency (1.6 GHz). The insertion loss for the complete module is about ?2 dB at the center frequency, the return loss is less than ?15 dB, and the maximum input level is about 10 mW.

Generation system for chrominance subcarrier

Abstract: PURPOSE:To increase the performance and stability, by making unnecessary complicated circuit such as single side band generation circuit or continuous phase veriable unit, in the generation system developing chrom subcarrier signal based on the separated horizontal synchronizing signal of PAL system. CONSTITUTION:The horizontal synchronizing signal 10 is compared 11 for the phase with the signal count down with the frequency counter 15 for the output of the chrominance subcarrier oscillator 14, and the phase error voltage according to this phase difference is mixed 12 with the output signal of the saw tooth wave generator 19 and amplified with integration, forming the phase control loop so that the oscillated frequency 14 can be controlled. Further, the frame synchronizing signal 20 is fed to the latch circuit and also fed to the saw tooth wave generator 19 and the AND gate 18. The output of the frequency counter 16 is in agreement with the output of the frequency counter 16 is in agreement with the output of the latch circuit 17 and is fed to the frequency counter 15, selecting the step down ratio of the counter 15. Accordingly, when the oscillator 14 is in agreement with the chrominance subcarrier frequency for the oscillated frequency, the output pulse of the counter 15 is in agreement with the horizontal synchronizing signal 10 for the average frequency, and phase error signal is caused in the output of the phase comparator 11.

Gigabit 4-Phase Modulation-Demodulation Circuits for Microwave Digital Systems

Abstract: An extremely high speed modulation-demodulation performance is discussed when data-rate becomes close to carrier frequency. A 4-phase PSK modulation-demodulation circuit with a newly designed transformer is described. The error-rate performance on 1.6 Gb/s data-rate was successfully undertaken at a 1.7 GHz carrier frequency.

A Multiple-Frequency Phase Comparison Technique for the Determination of Remote Layer Thickness

Abstract: A continuous-wave phase comparison technique which provides at least an order of magnitude improvement in accuracy over modulated carrier systems which operate in the same spectrum is described in this paper for the remote determination of the thickness of layered targets consisting of a known number of dielectric layers, each of a known maximum thickness. This system uses rationally related frequencies such as the fundamental and its harmonics to establish a multifrequency coherence relationship whereby a phase reference between frequencies can be conserved and information extracted from just the received and not the transmitted signals. Consequently, Doppler effects due to motion between the target layer and the apparatus, as well as local oscillator stability and drift limitations are avoided. Thus this system can measure the parameters of remote layered targets by interferometric techniques without the distance being a constraint.