Method for amplifying an echo signal suitable for vehicle surroundings detection and device for carrying out the method

Abstract

A method for amplifying an echo signal, in which an analog echo signal suitable for detection of a vehicle's surroundings is amplified by a gain dependent on the transit time of the echo signal, the analog echo signal being amplified by an amplifier having a plurality of outputs, each having a different gain, and a downstream A/D converter having a time-variable reference voltage. In the process, there is a switch between the different outputs of the amplifier at predefined switching points in time, and the reference voltage of the A/D converter varies over time between the switching points in time in such a way that the echo signal is present at the output of the A/D converter with a transit time-dependent total gain having a predefined characteristic.

Claims

1. A method for amplifying an echo signal, the method comprising: amplifying an analog echo signal, which is for detecting a vehicle's surroundings, with a gain which depends on a transit time of the echo signal, wherein the analog echo signal is amplified with the aid of an amplifier unit having a plurality of outputs each having a different gain and a downstream A/D converter having a time-variable reference voltage, switching between different outputs of the amplifier unit at predefined switching points in time, wherein: the amplifier unit includes a series-connected chain of amplifiers, the analog echo signal is amplified with the aid of the series-connected chain of amplifiers having a fixed gain, and with the aid of the downstream A/D converter having the time-variable reference voltage, and each of the plurality of outputs of the amplifier unit is a respectively different output signal line branching from a different junction connecting different consecutive amplifiers in the series-connected chain of amplifiers, so that, except for an output signal line of a last amplifier in the series-connected chain of amplifiers, each of the different output signal lines bypasses every downstream amplifier in the series-connected chain of amplifiers; and varying the reference voltage of the A/D converter over time between the switching points in time so that the echo signal is available at the output of the A/D converter having a transit time-dependent total gain, which has a predefined characteristic.

2. The method of claim 1, wherein the characteristic is predefined in pieces between the switching points in time.

3. A method for detecting a vehicle's surroundings with the aid of at least one echo signal, the method comprising: amplifying at least one analog echo signal, by performing the following: amplifying an analog echo signal, which is suitable for detection of a vehicle's surroundings, with a gain which depends on a transit time of the echo signal, wherein the analog echo signal is amplified with the aid of an amplifier unit having a plurality of outputs each having a different gain and a downstream A/D converter having a time-variable reference voltage, switching between different outputs of the amplifier unit at predefined switching points in time, wherein: the amplifier unit includes a series-connected chain of amplifiers, the analog echo signal is amplified with the aid of the series-connected chain of amplifiers having a fixed gain, and with the aid of the downstream A/D converter having the time-variable reference voltage, and each of the plurality of outputs of the amplifier unit is a respectively different output signal line branching from a different junction connecting different consecutive amplifiers in the series-connected chain of amplifiers, so that, except for an output signal line of a last amplifier in the series-connected chain of amplifiers, each of the different output signal lines bypasses every downstream amplifier in the series-connected chain of amplifiers; and varying the reference voltage of the A/D converter over time between the switching points in time so that the echo signal is available at the output of the A/D converter having a transit time-dependent total gain, which has a predefined characteristic; and evaluating at least the amplified echo signal for detection of a vehicle's surroundings.

4. A device for amplifying at least one echo signal suitable for detecting a vehicle's surroundings, comprising: an amplifier unit to amplify an analog echo signal having a time-dependent gain, wherein the amplifier unit includes a plurality of outputs having different gains; a downstream A/D converter having a time-variable reference voltage; and a control device to switch between different outputs of the amplifier unit at predefined switching points in time, and to generate a time-dependent total gain of the echo signal, which is present at the output of the A/D converter and has a predefined characteristic by varying the reference voltage of the A/D converter between the switching points in time, wherein: the amplifier unit includes a series-connected chain of amplifiers, the analog echo signal is amplified with the aid of the series-connected chain of amplifiers having a fixed gain, and with the aid of the downstream A/D converter having the time-variable reference voltage, and each of the plurality of outputs of the amplifier unit is a respectively different output signal line branching from a different junction connecting different consecutive amplifiers in the series-connected chain of amplifiers, so that, except for an output signal line of a last amplifier in the series-connected chain of amplifiers, each of the different output signal lines bypasses every downstream amplifier in the series-connected chain of amplifiers.

5. The device of claim 4, wherein the control device is configured to connect at least one input of the A/D converter to multiple outputs, including all outputs of the amplifier in succession at predefined switching points in time with the aid of at least one analog switch.

6. The device of claim 4, wherein the characteristic is predefined in pieces between the switching points in time.

7. A vehicle assistance system for detecting a vehicle's surroundings, comprising: a device for amplifying at least one echo signal suitable for detecting a vehicle's surroundings, including: an amplifier unit to amplify an analog echo signal having a time-dependent gain, wherein the amplifier unit includes a plurality of outputs having different gains; a downstream A/D converter having a time-variable reference voltage; and a control device to switch between different outputs of the amplifier unit at predefined switching points in time, and to generate a time-dependent total gain of the echo signal, which is present at the output of the A/D converter and has a predefined characteristic by varying the reference voltage of the A/D converter between the switching points in time; an evaluation unit for detecting a vehicle's surroundings by at least one of (i) at least one echo signal amplified with the aid of the device, and (ii) a nonamplified echo signal, wherein: the amplifier unit includes a series-connected chain of amplifiers, the analog echo signal is amplified with the aid of the series-connected chain of amplifiers having a fixed gain, and with the aid of the downstream A/D converter having the time-variable reference voltage, and each of the plurality of outputs of the amplifier unit is a respectively different output signal line branching from a different junction connecting different consecutive amplifiers in the series-connected chain of amplifiers, so that, except for an output signal line of a last amplifier in the series-connected chain of amplifiers, each of the different output signal lines bypasses every downstream amplifier in the series-connected chain of amplifiers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a shows one possible characteristic of a transit time-dependent signal gain according to the related art.

(2) FIG. 1b show another possible characteristic of a transit time-dependent signal gain according to the related art.

(3) FIG. 2 shows a device according to the present invention for generating a transit time-dependent signal gain according to the first specific embodiment of the present invention.

(4) FIG. 3 shows a possible characteristic of the transit time-dependent signal gain according to the first specific embodiment of the present invention.

DETAILED DESCRIPTION

(5) FIG. 2 shows a device 10 according to the present invention for generating a transit time-dependent signal gain V() according to the first specific embodiment of the present invention.

(6) The analog input signal (echo signal) r.sub.a in, which is dependent on transit time of the echo, having the usual center frequency of approximately 48 kHz in particular, has a basic gain V.sub.0 with the aid of basic amplifier 20. A downstream amplifier 30 includes N series-connected, cascaded amplifiers 40, 50 having a fixed gain V.sub.fixed j, which results in a fixed total input signal gain

(7) $V_{\mathrm{fixed\_total}N}=\underset{j=1}{\overset{N}{.Math.}}{V}_{\mathrm{fixed}j}.$

(8) FIG. 2 shows only two N series-connected amplifiers 40, 50.

(9) A fixed gain V.sub.fixed.sub._.sub.total k is selected between switching points in time .sub.k, .sub.k+1 with the aid of at least one analog switch 60, and the analog signal amplified in this way is applied to a downstream A/D converter (ADC) 70. Control device 100 controls at least one analog switch 60 in such a way that N outputs 41, 51 of amplifier 30 are each connected in succession to input 80 of A/D converter at predefined switching points in time .sub.1, . . . , .sub.N.

(10) By varying the reference voltage of A/D converter U.sub.Ref AD()|.sub..sub.k.sub.<.sub.k+1 with the aid of control device 100, a corresponding time-variant gain V.sub.AD()|.sub..sub.k.sub.<.sub.k+1 is generated, in such a way that the total system gain of the scanned signals behaves according to a predefined characteristic V(). An output signal r.sub.d amplified by the total system gain is present at output 90 of A/D converter 70.

(11) For the total system, the variation in reference voltage U.sub.Ref AD()|.sub..sub.k.sub.<.sub.k+1 of A/D converter 70 acts like a time-variant gain V.sub.AD()|.sub..sub.k.sub.<.sub.k+1 of the scanned signals. A desired gain characteristic V() may be generated in pieces between switching points in time 0, .sub.1, .sub.2, .sub.3, .sub.4, . . . , .sub.N as shown in FIG. 3.

(12) In particular an inexpensive device 10 having an architecture with which the function of a desired, continuously adjustable gain is easily implementable in the required dynamic range

(13) $1\frac{V\left(\right)}{V_0}<V_{\max }$
is provided according to the present invention.

(14) With the aid of device 10 according to the present invention for gain and subsequent analog/digital conversion of signals r.sub.a in, a transit time-dependent gain V() is implemented with the aid of a series-connected chain of amplifiers 40, 50 having a fixed gain V.sub.fixed j at which there is a switch between different effective fixed partial gains V.sub.fixed.sub._.sub.total k with the aid of at least one analog signal switch 60 at certain points in time .sub.1, .sub.2, . . . , .sub.N, and downstream A/D conversion 70 is influenced with the aid of time-variable reference voltage U.sub.Ref AD()|.sub..sub.k.sub.<.sub.k+1 between switching points in time .sub.k, .sub.k+1, in such a way that the total system gain is more or less equal to the desired transit time-dependent gain V() due to this successive approximation.

(15) In addition to the written disclosure above, reference is herewith made explicitly to the illustrations in FIGS. 2 and 3 for further disclosure of the present invention.