Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Analysis of complex waves
Reexamination Certificate
2001-01-22
2004-01-20
Le, N. (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Analysis of complex waves
C324S076490, C324S076490
Reexamination Certificate
active
06680606
ABSTRACT:
This application is a national phase of PCT/FR99/01319 which was filed on Jun. 4, 1999 and was not published in English.
TECHNOLOGICAL FIELD
The invention relates to the field of electrical sampling, particularly of pulses of short or very short duration.
The metrology of pulses enables one to describe the evolution in time of a signal, or an electrical pulse, in particular its voltage or its energy, when this signal, or this pulse, is, for example, unique (i.e. non-repetitive), and very brief (that is to say, has a duration of the order of a few tens or a few hundreds of picoseconds).
Such pulses to be measured generally arise from very fast radiation detectors, which convert into electrical pulses, the energy of a pulse of radiation that they receive, for example, a pulse of X, or gamma, or visible, or infra-red radiation. Such radiation can be emitted by ultra-fast radiation sources, such as lasers or sources of synchrotron radiation, or can be the result of a laser-material interaction caused by an ultra-fast laser (that is to say, the duration of the pulse is in the picosecond or femtosecond range).
The invention can be applied to any measurement of a very brief electrical signal, particularly a non-repetitive signal, in particular in the physics of events, or in the measurement of events, generated by picosecond phenomena.
STATE OF THE TECHNOLOGY
There currently exist on the market sampling oscilloscopes for the measurement of signals whose spectrum extends to 50 GHz or 70 GHz. These pieces of equipment enable one to measure repetitive pulses. The sampling frequency is variable between from 250 kHz to 1 GHz.
In order to measure single pulses, commercial equipment exists on the market: this equipment enables one to reconstruct a spectrum up to 5 GHz or 7 GHz.
Among the laboratory prototypes, a known device is that described in document U.S. Pat. No. 5,471,162. Such a device rests on the principle of spatial sampling of a pulse. A pulse propagates along its line of propagation. The result is a spatial equivalent of the evolution, over time, of this pulse which is propagated on the line with a speed depending on its physical characteristics. At a specified instant t, if the line is of sufficient length, the whole of the pulse is distributed spatially along the line.
If the samplers are arranged along the line of propagation, their simultaneous actuation allows one to carry out complete sampling of the pulse, with a time step equal to the spatial step of the samplers, divided by the speed of propagation.
An optical sampling device is also known which measures signals with a bandwidth up to 35 GHz. This device is illustrated in FIG.
1
. It comprises a line of propagation
2
into which a pulse signal
4
to be measured is inserted and along which it propagates. Along the line of propagation sampling ports
6
, made of a photo-conductive material (CdTe), are arranged in a regular manner. These sampling ports are associated with sampling lines
8
, each of which is connected to charge reading means. The set of charge reading means is gathered into a charge reading device
10
. These charge reading means are connected to a computer
12
programmed to measure the relative charges on each channel and to analyze the pulse
4
. Each sampling port
6
has its circuit closed by a triggering light pulse
14
: a triggering light pulse is necessary which is distributed over all the sampling ports. Therefore, this device requires a picosecond optical flash of a few tens of nanojoules to trigger the sampling.
These known samplers are therefore photo-conductors, in the case of the optical sampler (
FIG. 1
) and diodes in the case of the compact digitizer.
In these known structures, samplers sample a part of the signal present at their position on the line. They are placed in parallel, on this line of propagation.
Document FR-97 06534 describes a single action electrical sampler for short pulses.
The principle of this electrical sampler, with line sections is illustrated in FIG.
2
.
A structure, or line,
24
of propagation of electrical pulses comprises a plurality of sections
18
,
20
,
22
of this structure. The different sections are linked, two by two, through switches
28
,
29
, constituted by, for example, MESFET AsGa (or Si, or MOS transistors or bipolar transistors on Si).
The command means for the switches
28
,
29
comprise, for example, a second structure
26
for the propagation of a triggering pulse, to which the switches
28
are connected.
In
FIG. 2
, only three sections of the line
24
have been shown, but the line may comprise any number of sections, separated, two by two, and connected two by two, by the switches.
A signal to be sampled propagates along the propagation structure, or the line of propagation
24
.
Along the line of propagation
26
, a synchronization signal is propagated, for example a voltage step slot. The switches are normally on, or closed, and the voltage step opens these switches. This step or slot, therefore isolates each section of the line of propagation, which is then used as a storage capacitance.
The whole of the charges transported by the pulse is then confined in the different sections
18
,
20
,
22
that make up the pulse propagation structure.
The structure illustrated in
FIG. 2
thus comprises:
on the one hand, a first propagation structure
24
where the quantity of charges to be measured is propagated and which is made up of sections connected two by two by switches which are initially closed,
on the other hand, a second propagation structure in which a synchronization signal of the “step” type can be propagated; at the moment the step passes, this modifies the command of the state of the switch in such a way that it opens and isolates the two sections to which it is connected, charges then being trapped in a section when the two switches which mark its limits are open. It is these charges which are subsequently read by a suitable reading device.
The device is completed by means of generating a synchronization signal, these means being connected to the structure
26
for propagating synchronization pulses. In addition, they can be connected to a device for reading the charges in the sections.
These samplers have a restricted bandwidth, linked to the bandwidth of the line itself. Furthermore the sensitivity of detection (that is to say the quantity of charges sampled in the signal) is also limited. With regard to the optical sampler, the use of a picosecond, high power laser imposes very great financial and experimental constraints.
Finally, all these devices require a very long propagation line, corrupting the signal in a non-uniform manner.
DESCRIPTION OF THE INVENTION
The invention relates to a novel electrical sampler. In particular, it relates to an analyzer of fugitive signals, that uses a non-simultaneous spatial sampling method.
It also relates to an analyzer of fugitive signals, that uses a new technology for coupling substrates.
Such an analyzer can be used for laser diagnostics. Its field of application also extends to the measurement of rapid single signals of any origin, through a simple adaptation.
More precisely, the subject of the invention is an electrical sampler, characterized in that it comprises:
a structure for the propagation of electrical pulses,
N means of sampling connected, on the one hand, to sampling points along the propagation structure, and, on the other hand, to means for the propagation of sampling signals,
means to temporally delay the propagation of a sampling signal between two consecutive sampling means.
A spatial sampling device according to the invention uses as many elementary samplers as there are samples to be taken. Each elementary sampler only functions once by acquisition. The signal is propagated on a propagation support matched to the frequencies to be analyzed, along which the samplers are arranged sequentially in such a way that the signal passes in front of each of them with a time shift that is linked to the spatial step of the layout of the samplers and to the temporal delay m
Ajram Sami
Ghis Anne
Benson Walter
Commissariat a l'Energie Atomique
Le N.
Thelen Reid & Priest LLP
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