Wave transmission lines and networks – Plural channel systems – Having branched circuits
Patent
1997-06-03
1999-01-26
Gensler, Paul
Wave transmission lines and networks
Plural channel systems
Having branched circuits
324632, H01P 518
Patent
active
058642595
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a measuring line, or test line, that can be coupled to a coaxial conductor. More specifically, the invention relates to a measuring line, or test line as described hereinafter.
Such measuring lines are often used in connection with antenna-connected conductors, e.g. in mobile telephony systems, intended for the UHF range. The transmitted energy is often comprised of several different carrier waves which have a mutual radio-channel spacing and which are intended for transmission on one and the same antenna, and consequently measuring of the composite power is of interest, despite being able to measure the transmission power of each modulated carrier wave per se. The standing-wave ratio is measured and monitored for the composite power, so as to be able to check antenna function among other things, since faults in an antenna function will normally result in mismatching noticeable by reflections, this mismatching immediately having a marked effect on the standing-wave ratio.
Measuring lines of the kind defined in the introduction and capable of being connected to a coaxial conductor or line with the aid of conventional coaxial contacts are known to the art, wherein the microwave energy is conducted through a hollow conductor which includes an inner conductor that is connected to the centre conductor of the coaxial connections and which has overall the same impedance as the coaxial conductor, e.g. an impedance of 50 ohms.
In view of the high powers that occur (upwards of 1 kW), the hollow conductor must have a careful configuration. A typical type is the so-called slab line, which is a type of TEM conductor and consists of a centre conductor placed between two parallel surfaces which together with narrower side surfaces and end surfaces define a flat, box-like configuration. In the case of one known construction, a directional coupler is located on each of said sides. The directional couplers are earthed at respective opposite ends via a matching resistor, whereas the non-earthed ends are each coupled to a respective measuring device, whereby the ratio between the output powers each representing a respective propagation direction can be measured and the standing-wave ratio can be calculated in voltage measurements (VSWR).
One object of the present invention is to provide a measuring device of the aforesaid kind which can be produced more cheaply and more simply. Another object of the invention is to provide in said device room for a measuring probe, a so-called test coupler. When wishing to make a complete analysis of what is transported in a coaxial conductor, it has hitherto been necessary to include a further measuring path, with the additional complexity and risk of error that this includes. It is difficult to provide room for more than two coupling conductors in a hollow conductor of the aforesaid kind, one on each side of the main conductor between the broad surfaces of the "box".
The aforesaid objects and advantages afforded by the invention are achieved by arranging in the hollow conductor solely one single directional coupler conductor which has symmetrically disposed transverse branch lines which are drawn through openings in a wall of the hollow conductor and each of which extends to a respective adapted conductor in a circuit board mounted externally of said wall, wherein the directional coupler conductor within the cavity and the lines or conductors on the circuit board have mutually matched impedances. Using circuit board technology, it is therewith possible to achieve the necessary precision much more cheaply and much more simply than can be achieved with conventional workshop practice.
The directional coupler conductor will preferably have a higher impedance than the hollow conductor, wherein an upper limit is set for reasons of mechanical stability because a high impedance means a narrow or slender directional coupler conductor and because a narrow directional coupler is unable to cope without the support of a dielectric material, which would result in impaired
REFERENCES:
patent: 4211911 (1980-07-01), Dehn
patent: 4859971 (1989-08-01), Edwards et al.
patent: 4990858 (1991-02-01), Garner
patent: 5325064 (1994-06-01), Leanes et al.
Gensler Paul
LG Products AB
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