Multiplex communications – Diagnostic testing – Of a switching system
Reexamination Certificate
2000-10-04
2004-10-12
Marcelo, Melvin (Department: 2663)
Multiplex communications
Diagnostic testing
Of a switching system
C455S423000
Reexamination Certificate
active
06804200
ABSTRACT:
The invention relates to a switching network for connecting at least one high-frequency signal between at least one transceiver and at least one other transceiver according to the introductory part of Claim
1
.
Such a switching network represents a radio link, particularly for the mobile radio sector, and serves to simulate the link for testing mobile radio equipment such as transceivers of mobile radio base stations and mobile radio terminals.
Until now, link simulations have been realized with switching networks discretely constructed for the particular application, and this has necessitated high circuit-assembly costs, especially for the testing of so-called dual band mobile radio terminals operating in both the GSM (900 MHz) and DCS (1800 MHz) frequency bands. Also, the discretely constructed switching networks have not been convenient for users to operate. To simulate the attenuation of the radio signals, interconnected coaxial relays have been used as attenuators. These not only have a certain switching time, but also have limited life. Furthermore, switching from one attenuation value to another has caused a certain radio-signal blackout time which has made readings difficult.
The problem which lies at the basis of the invention is to improve a switching network of the kind stated at the outset, in terms of functionality and ease of operation.
This problem is solved in accordance with the invention by the features stated in the independent claim.
In this solution the switching network comprises: a first switching stage with at least two similar switching modules for connecting at least one transceiver, the switching modules each having a power splitter and at least one fixed or variable signal attenuator and outputs at which the unattenuated input signal and at least one attenuated input signal are available; a second switching stage with at least one switching module which has at least two inputs downstream of each of which a stepped attenuator is connected and a power splittor which combines the inputs to form a common output signal; and a third switching stage with at least one switching module which comprises a four-pole hybrid coupler with two inputs and two outputs, the outputs having signal attenuators connected upstream to which at least the other transceiver is connectable; the inputs of the second and third switching stages being connectable as desired, by means of jumpers and/or connection cables, to the outputs of the first and second switching stages.
The invention affords the advantage that the widest variety of test scenarios can be realized without incurring great expense in terms of circuit assembly. All that is necessary it to interconnect the switching modules as desired by means of jumpers or plug connections. This results in greater convenience of operation. The inputs and outputs of the switching modules are advantageously led to connection sockets located on the front and/or back of the casing. Installation in a standard casing, e.g. a 19″ casing, renders the switching network easily transportable, and usable in any location.
In one preferred embodiment of the invention, with a view to augmenting the possible connections and combinations between the switching modules, the switching network is equipped with an additional freely connectable four-pole hybrid coupler with two inputs and two outputs, the outputs of the second switching stage being connectable as desired, via the hybrid coupler, to the inputs of the third switching stage.
Short switching times of the stepped attenuators and long life by comparison with relay-type switching stages can be obtained in accordance with one embodiment of the invention by building the stepped attenuators from semiconductor components. Semiconductor attenuators also allow switching operations to be performed without causing interruptions i.e. without blacking out the signal during switching. This is especially advantageous when carrying out series at readings or runs. Another advantage of semiconductor components is the low overall insertion loss of typically 17 to 25 dB that can be achieved, depending on how the switching modules are connected. This means that signals from very weak signal sources can also be processed.
In another preferred embodiment of the invention, a keyboard fitted to the casing allows direct setting and/or step-adjustment of the attenuation values of the stepped attenuators. This enhances convenience of operation. The attenuation setting can be displayed directly to the operator by a corresponding display device.
According to the invention the switching network is rated for a frequency range of approx. 800-2500 MHz. This large frequency range is achieved through the use of the latest semiconductor components, making it possible for the first time to test dual band or triband mobile radio terminals operating in the 900, 1800 and 2200 MHz range.
According to a development of the invention, signal strength display devices are arranged at the inputs or outputs of the first switching stage; in the simplest (and preferred) case these comprise a high-frequency coupler, a high-frequency rectifier and a comparator circuit or threshold circuit with at least one visual display element for the signal strength. The output with the optimal strength, which is led to the subsequent switching stages, is then easily determined.
REFERENCES:
patent: 5465393 (1995-11-01), Frostrom et al.
patent: 6128474 (2000-10-01), Kim et al.
patent: 6438357 (2002-08-01), Oh et al.
patent: 2002/0119772 (2002-08-01), Yoshida
Bremer Hans
Burggraf Reiner
Kreuz Wolfgang
Reinert Jürgen
Marcelo Melvin
McCormick Paulding & Huber LLP
T-Mobile Deutschland GmbH
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