Substitute circuit for a plurality of functional units

Details Substitute circuit for a plurality of functional units Substitute circuit for a plurality of functional units

1997-02-27

1998-07-14

Elmore, Reba I.

Excavating

36447012, 364733, 364149, G01R 3108, G06F 1100, G08C 1500, H04L 100

Patent

active

057815631

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a substitute circuit for a plurality of functional units.
A substitute circuit which is connected via mechanical switches is presented in the Patent Abstract of Patent JP-A-59 011 454.
It is known for substitute circuits to be provided in order to improve the operational reliability. If a functional unit, for example an assembly, fails, this functional unit is isolated from the signal path (or the signal paths), and a substitute functional unit is connected in its stead. Relays have been used for changing over; in the case of digital signals, an implementation of the switching over is also possible by means of logic modules.
Laid-Open Specification of German reference DE 41 32 598 A1 discloses a system for switching over telecommunications devices, in which a changeover to a substitute device is made for the purpose of substitution or for testing one of these devices. Relays are used for switching over.
The use of relays for switching over operational functional units and substitute functional units is extremely problematic. The reliability of the relays decreases rapidly for the changeover operations, which are carried out extremely rarely.
In the case of a substitute circuit which processes digital or analog signals at relatively high frequencies of about 30 Megahertz (MHz) or even several Gigahertz, further problems arise.
The relay contacts have excessive capacitances, so that their use is not feasible for this reason alone. In addition, this solution would necessitate the provision of greater power.
The generally used ECL (emitter couple logic) technology requires considerable power levels, so that logic circuits are not ideal for changing over, just for reasons of power consumption. In addition, there are also no modules with which implementation would be feasible for higher frequencies.
Diode switches which are more suitable for changeover purposes in the radio-frequency range are known from the German Examined Specification 26 08 117.
The Laid-Open Specification of German reference DE 41 02 930 A1 discloses a circuit for splitting or combining radio-frequency power, in which the initial outlet impedance, which acts between the individual pores in each case, is formed by an absorber resistor, which is connected to ground at one end, for splitting radio-frequency power, which is supplied from a sum port, to a plurality of individual ports and for combining radio-frequency power, which is supplied from individual ports, in a sum port. However, only a low level of decoupling is provided between the inputs and the outputs in this arrangement.
Combiners for VHF and UHF signals are described in the journal "MICROWAVES and RF", December 1990, pages 100 to 108 and October 1993, pages 81 to 86 and 132. There is no reference quoted for use with digital signals or for substitute circuits.


SUMMARY OF THE INVENTION

The object of the invention is to specify a substitute circuit, which is suitable for higher frequencies, for a plurality of functional units.
The use of in each case only one substitute functional unit for a plurality of operational functional units is particularly advantageous. Duplication of systems or functional units is generally no longer necessary for a high level of fail-safety.
The use of double distributors/combiners which are constructed using transformers has been found to be particularly expedient. The double distributors/combiners are used for distributing a signal from an input between two outputs or for combining two signals onto this output. These passive components require no operating power whatsoever and have inputs and outputs which are decoupled excellently.
Combiners and distributors can be designed using pin-diodes, as a particularly simple, cost-effective and advantageous variant.
A plurality of substitute functional units can also be provided for further increased reliability, and are each connected to the associated substitute functional units via a separate combination circuit.
Pin-diode combinations are provided as e

REFERENCES:
patent: 4448074 (1984-05-01), Schmidt
patent: 4558216 (1985-12-01), Rodi et al.
patent: 4623974 (1986-11-01), Dentz et al.
patent: 4774451 (1988-09-01), Mehnert et al.
patent: 4947386 (1990-08-01), Preschutti
patent: 4970722 (1990-11-01), Preschutti
patent: 4972292 (1990-11-01), Petersen
patent: 5066930 (1991-11-01), Morse
patent: 5229999 (1993-07-01), Cushing et al.

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