DOI:10.1049/jiere.1986.0013

出版商:IERE    

年代:1986

数据来源: IET

摘要:

Tape-skew variation imposes one of the limits on the upper recording frequency at which digital data may be read coherently from a multitrack tape. It can be measured using timers controlled from marker transitions on the outer tracks of the tape. The timers are interfaced to a microprocessor which applies a ratio technique to indicate a bit-cell displacement which is insensitive to tape velocity and circuit variations. Spectral analysis of the skew of C60 compact cassette tapes reveals a cyclic variation of skew angle of about 2 Hz with a total displacement across the tape of within one bit-cell at 10kb/s.The skew angle is not always uniformly distributed across the tape due to tape deformation. The computed values of average tape deformation are 0-67 μm, 0.85 μm and 1.08 μm for C60, C90 and C120 tapes respectively.

DOI:10.1049/jiere.1986.0019

出版商:IERE    

年代:1986

数据来源: IET

摘要:

The EBU published in March 1985 the detailed technical specifications of a family of receiver-compatible systems which are recommended for direct satellite broadcasting at 12 GHz and for the distribution of broadcasts from these satellites on cable networks.The systems in this family, known as the ‘MAC/packet’ family, are based on the time-multiplexing of analogue and digital elements, the coding of the television picture in MAC (time-multiplexed analogue components), the digital coding of sound signals and the packet multiplexing of sound and data services.The members of the family are the C-MAC/packet system intended for DBS, the D-MAC/packet system intended for wide-band cable distribution (at least 10-5 MHz) of all the information contained in the C system, and the D2-MAC/packet system intended both for DBS and for narrow-band cable distribution (at least 7 MHz) but with the loss of one-half of the digital services carried in the C and D systems.

DOI:10.1049/jiere.1986.0020

出版商:IERE    

年代:1986

数据来源: IET

摘要:

This paper describes the development and engineering of a practical traffic simulator for assessing the behaviour of the SKYNET 4 s.h.f. satellite transponders to various access configurations. The simulator encompasses the full input s.h.f. band of the transponders with a minimum access spacing of 50 kHz. Pseudo-random data streams are used to simulate digital traffic between 50 bit/s and 20 Mbit/s.Up to 32 separately tunable accesses are provided with a further provision for expanding each carrier as a comb of up to four carriers while still maintaining the noise and stability specification of the simulator.The generated access levels are such that they interface with the satellite under pre-launch/laboratory test, either by direct interconnection to its repeater amplifier or via a transmission path and the satellite antenna. The equipment is self-contained in a portable console.

DOI:10.1049/jiere.1986.0021

出版商:IERE    

年代:1986

数据来源: IET

摘要:

A direct conversion digital radio may have a limited dynamic range performance under some circumstances, due to deviations from true quadrature between the I and Q signal paths. These errors are analysed and a method of correcting them, using an adaptively designed digital filter, is proposed.

DOI:10.1049/jiere.1986.0022

出版商:IERE    

年代:1986

数据来源: IET

摘要:

The interaction between a user and instrumentation can be represented by a standard notation or grammar. The software tools necessary generate computational structures called parsers. The parsers described in the paper are implemented in hardware using programmable logic arrays which are realized as v. l. s. i. silicon devices.

DOI:10.1049/jiere.1986.0023

出版商:IERE    

年代:1986

数据来源: IET