Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
2000-05-15
2001-12-04
Phan, James (Department: 2872)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C342S137000, C342S175000, C342S372000, C359S896000
Reexamination Certificate
active
06326917
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a scanner-control device for scanning an echo signal formed by returning transmit initial pulses, including a clock generator, which triggers a pulse shaper for the transmit pulses and a further pulse shaper for scanning pulses, and a setting member (e.g., an ajustment element) for modifying a delay time &Dgr;
T
of the scanning pulses, so that the echo signal can gradually be reconstructed from the returning transmit pulses.
BACKGROUND INFORMATION
A scanner-control device of this type has applications in many technical areas, for example in a nonhomogeneous medium or on boundary surfaces, to receive reflected echo signals from transmit pulses and to evaluate them. Through an echo-time (e.g., delay time) measurement, information can be derived regarding, for example, the length of the distance that the signal has traveled. Examples of applications include distance measuring using sound, radar, or light waves. Furthermore, the echo signal shape can give information about the structure of the carrying medium, such as in determining the fog density in the atmosphere using light waves, or in seismic measurements of plate motion in the earth, or in measurements of material layers in pipes and walls using radar, to name only a few examples.
In most cases, an evaluation in real time, i.e., at the speed at which the echo signals arrive, is impossible due to the insufficient speed of the evaluation circuit. This is particularly true of the evaluation of signals that expand at the speed of light. Therefore, for this purpose, scanning devices are used in which the echo signal is scanned in a step-by-step manner, resulting in the desired time extension for the evaluation. In a scanning system of this type, a clock generator periodically triggers a pulse shaper, which sends transmit pulses to the system to be investigated. The returning echo signal is scanned in a scanner after a variable time &Dgr;
T
. The scanning value associated with a time point, after delay &Dgr;
T
, receives further signal processing. By varying delay &Dgr;
T
, the entire echo signal can gradually be reconstructed.
The conventional methods for generating scanning pulses delayed by a delay &Dgr;
T
are either imprecise or very expensive, particularly for very small increments and/or great variation ranges.
In U.S. Pat. No. 5,543,799, a local-range radar is described in which a variable, voltage-controlled delay of the transmit pulse takes place. The delay in certain circumstances is not a linear function of a control voltage and is therefore imprecise.
The Analog Devices Company offers a digital circuit arrangement having a controllable time delay (AD9501, AD9505), the linearity being maintained through generating a highly precise frame function.
SUMMARY OF THE INVENTION
The present invention relates to refining a scanner-control device so that the transmit pulses and the delayed scanning pulses are generated very precisely, and the echo signal can be reproduced very precisely.
The pulse shaper for the transmit pulses is an element of a first closed loop having a summing point and a controller (e.g., a closed-loop controller), and the further pulse shaper is an element of a second closed loop having a further summing point and a further controller, and that the summing point and a further summing point have supplied to them an identical setpoint value, and the further summing point additionally has supplied to it a further setpoint value, which is varied in order to modify the delay time. Through the feedback control of the transmission of the transmit pulses and of the scanning pulses, in this manner transmit pulses and scanning pulses are generated in a precisely prescribed manner, the time relation of one to the other being maintained in a stable manner.
A stable feedback control in a simple design of the control device is achieved through the fact that the pulse shaper and the further pulse shaper, in each case, have at least one switching element which at a given threshold voltage carries out a switchover, and that a control direct voltage applied to the switching element is controlled by the controller and the further controller.
A control deviation is reliably detected, for example, due to the fact that the setpoint value supplied to the summing point and a further summing point as well as the further setpoint value are direct voltages.
If provision is made that the further setpoint value is a direct voltage formed by a counter and a D/A converter connected downstream of the counter, and that the counter is clocked using a clock generator, then a modification of the delay is achieved that can be quantized very precisely, values of less than 50 ps being reproducible.
An exemplary embodiment that is also suitable for rapidly changing control voltages and using which a large usable frequency range is achieved for the control signal, the controller having only to compensate for errors in the selected weighting and for effects from non-linearities, arises from the fact that in the second closed loop between the further controller and the further timing (e.g., echo-time) element a summing element is provided, to which the further setpoint value is supplied.
A simple design for generating and controlling the transmit pulses and the scanning pulses is achieved through the fact that the switching element has an AND gate circuit, one input of which receiving the clock signal of the clock generator and the other input of which being connected to an RC, RL, or LC element and receiving an input signal having the superimposed control direct voltage. By superimposing the control direct voltage, the echo time of the arrangement can be changed, since the gate circuit always switches at the same switching point, the delay shifting in a defined manner using the control voltage. In this context, it is an advantageous measure that the other input has supplied to it, as the input signal, the inverted clock signal having the superimposed control direct voltage.
A further advantageous configuration of the control device for a stable, highly precise feedback control of the transmit pulses and scanning pulses arises from the fact that the switching element has a NAND gate circuit and a flip-flop, to whose clock input the clock signal of the clock generator is supplied and whose one output is connected via a timing element to an input of the NAND gate circuit and is connected to the controller or the further controller, that the other input of the NAND gate circuit via a further timing element is supplied, on the one hand, with the clock signal and, on the other hand, with the control direct voltage superimposed on the clock signal, and that the output of the NAND gate circuit is connected to a reset input of the flip-flop, and trailing edges of the output signal of the NAND gate circuit function directly to trigger the transmit pulses or the scanning pulses. In this specific embodiment, there is no need for a further circuit that generates the transmit or scanning pulses from the trailing edge of the signal supplied to the controller. The position of the trailing edge, which determines the transmission time point and scanning time point, is in this embodiment also feedback controlled.
REFERENCES:
patent: 5543799 (1996-08-01), Heger
patent: 5563605 (1996-10-01), McEwan
patent: 5757320 (1998-05-01), McEwan
Pfendler Thomas
Steinlechner Siegbert
Kenyon & Kenyon
Phan James
Robert & Bosch GmbH
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