Pulse or digital communications – Transceivers
Reexamination Certificate
2002-12-23
2004-05-18
Tse, Young T. (Department: 2634)
Pulse or digital communications
Transceivers
C375S257000
Reexamination Certificate
active
06738416
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to devices for transmitting high-frequency as well as digital signals between moving parts, consisting of a signal source and a signal sink connected by a transmission channel. Specifically, the present invention relates to the transmission of high-frequency signals such as intermediate-frequency signals or even digital data, rather than high-performance transmission in the microwave range. Such signals are normally made available as non-symmetrical signals.
High-frequency and also digital signals must frequently be transmitted between parts which are mobile relative to each other. A typical application of such transmission paths is radar technology, where signals are transmitted from the transmitter/receiver unit to the antenna.
Various devices are known for transmitting non-symmetrical signals. For instance, the transmission may be performed in a capacitive manner via a package of plates resembling a variable capacitor. The main problem of this arrangement is the current path between the mutually mobile parts is not precisely defined.
Initially, the current flows through the plate package. The return path is normally the frame or chassis, which is mostly implemented as a screen or housing. When the parts are rotating relative to each other, however, it is particularly difficult to achieve an effective low-inductance frame or ground connection. This results in the inherent problems with the previous transmission systems. In this case, it is very difficult to achieve constant transmission characteristics and a constant cross-talk.
Even though transmission paths implemented with the aid of variable capacitors have a comparatively large bandwidth, in distinction from other transmission techniques, they present the disadvantage of high engineering expenditures (in terms of the plate packages) and an upper limit frequency which is far below a wavelength corresponding to the dimensions of the plate package. Another disadvantage of this arrangement is their high sensitivity to mechanical loads as well as shocks and vibrations.
Transmission paths based on coupled resonance circuits present good transmission characteristics, but naturally they only have a very narrow band. They have high expenditure requirements (in terms of manufacturing technology), and may possibly require trimming. For different applications, each of these elements must be dimensioned differently. As a result, it is nearly impossible to obtain a wide range of products with such transmission paths in a standard design.
In order to avoid the disadvantages of these arrangements, several approaches have been tried to improve the high-frequency transmission characteristics of conventional collector rings. One such approach involves a method of simultaneously inputting the signals at several locations so that the occurrence of resonances at elevated frequencies is ensured during limited operating conditions. In another approach, attempts have been made to configure a slip ring with a defined wave resistance and to terminate it with the wave resistor at a suitable location.
Both approaches are entirely unsuitable for broad-band high-frequency transmission because they begin from a closed annular contact path. This path will always be a capacitive load. Even when a resistor is mounted, which corresponds to the wave resistor, a closed ring can never be designed to be free of reflections. With reference to FIG.
4
and
FIG. 5
, the explanation for this is as follows.
FIG. 4
shows a closed ring which is designed with a wave resistor of Z
o
=50 &OHgr;. An impedance
15
with R=50 &OHgr; is mounted on this wave resistor.
FIG. 5
shows a small segment of the ring including the impedance. On the assumption that the ring is actually terminated, and free of reflections, a wave propagating along the direction would encounter an impedance ahead of the impedance
15
. This is the result of mounting in parallel the real resistor (with R=50 &OHgr;) and the line (with Z
o=
50 &OHgr;) for the purpose of continuing conduction behind the resistor. The value of the parallel circuit is 25 &OHgr;. As a result, the line cannot be free of reflections for the wave ahead of the resistor. Even with all other combinations of wave resistors and terminating resistors, a line free of reflections is unobtainable.
The previously described non-contact transmission methods are superior to the contacting methods, because they contain a negligible amount of mechanical friction and hence a lack of abrasion or contact wear. The service life of such non-contact transmission systems is essentially longer than that of the contacting methods. This is particularly true in the case of high speeds in the relative motion of the moving parts. Nevertheless, these transmission methods have the inherent disadvantage of a frequency limit that is lower. As a function of the particular design, this limit may vary. What is characteristic, however, is the fact that a common-mode component with a frequency of 0 (zero) cannot be directly transmitted.
The digital signals occurring in practical industrial application, e.g. the signals used in advanced bus systems, vary between almost static signals with extremely low frequencies and signals with a maximum clock rate predetermined by the bus system. The lowest frequencies occurring are mostly below the lower limit frequency of the previously described non-contact transmission systems.
Hence a direct transmission of these signals is, as a rule, not possible. The known modulation or coding methods are a remedy in this respect. Both methods require high engineering expenditures. The coding methods which are well suited for digital signal transmission, such as the Manchester coding approach, require a wider bandwidth of the transmission channel merely on account of their coding. As a result engineering expenditures and costs of the transmission path are increased. Moreover, regeneration of the digital signal's timing is required in the majority of coding applications. This timing is frequently unreconstructable from the signal. Only with a suitable data structure, is timing regeneration possible via PLL elements. Such circuits are mostly suitable for a previously determined data rate. In the event that the non-contact transmission path should be transparent in terms of data and protocol, only the expensive modulation methods can be employed.
The object of the present invention is to improve a device for transmitting signals between mobile elements consisting of a signal source and a signal sink connected by a transmission channel such that a reliable wide-band transmission is ensured. This is accomplished without a frame or ground connection being required between the moving parts.
A further object of the present invention is to provide devices that are suitable for transmitting high-frequency signals and/or digital signals. Moreover, according to the object of the invention, a transmission that is transparent in terms of protocol and data, with a data rate lower than the lower limit frequency of the transmission path for the transmission of digital signals should be possible with low engineering expenditures and without an increased bandwidth requirement.
These and other objects and advantages are achieved by the present invention device, in which a signal source and a signal sink are connected by a transmission channel such that the transmission path has a symmetrical structure and hence a precisely defined current path is available. The current paths for emission and return are obtained in approximately identical ways. Therefore, the signal flow must not be returned via another path which is poorly defined. Hence, poor frame or ground connections are irrelevant and a frame or ground connection may even be eliminated entirely. As a result, a separation of potentials of the parts that are movable relative to each other can be achieved at the same time. Moreover, due to the symmetrical transmission, an excellent in-phase rejection is ach
Schleifring und Apparatebau GmbH
St. Onge Steward Johnston & Reens LLC
Tse Young T.
LandOfFree
Device for signal transmission between moving parts does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for signal transmission between moving parts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for signal transmission between moving parts will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3194217