초록 ▼

In fill-level measuring devices according to the pulse-transit-time method, a reflection that is generated internally in a microwave module is used as a reference for transit time measuring. For generating the reference pulse, the microwave module comprises its own sampling mixer or its own oscillat

In fill-level measuring devices according to the pulse-transit-time method, a reflection that is generated internally in a microwave module is used as a reference for transit time measuring. For generating the reference pulse, the microwave module comprises its own sampling mixer or its own oscillator. Subsequently, the echo signal and the reference pulse can be further processed separately or together. No delay line is necessary on the transmission frequency of the radar sensor. Interference as a result of leakage signals is largely prevented.

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What is claimed is: 1. A microwave module for an independent reference pulse generation for a fill-level measuring device, comprising: an echo signal unit providing an echo signal; a reference-pulse generating unit generating a reference pulse, the reference-pulse generating unit including a first

What is claimed is: 1. A microwave module for an independent reference pulse generation for a fill-level measuring device, comprising: an echo signal unit providing an echo signal; a reference-pulse generating unit generating a reference pulse, the reference-pulse generating unit including a first sampling mixer, the first sampling mixer converting a reference signal to the reference pulse in the form of a second intermediate-frequency signal; a sampling pulse generator generating a sampling pulse; a second sampling mixer situated in the echo signal unit, the second sampling mixer converting a receiving signal and the sampling pulse to the echo signal in the form of a first intermediate-frequency signal; an intermediate-frequency amplifier; and a changeover switch transmitting the first intermediate-frequency signal and the second intermediate-frequency signal to the intermediate-frequency amplifier, wherein the reference pulse and the echo signal are signals that are separate from each other. 2. The microwave module according to claim 1, further comprising: a first drawing-off device situated in the reference-pulse generating unit; wherein the first drawing-off device decouples the reference signal from a transmission path for a transmission signal between a first oscillator and one of (a) an antenna and (b) a probe. 3. The microwave module according to claim 2, further comprising: a first amplifier amplifying the transmission signal, the first amplifier being arranged downstream of the first drawing-off device in the transmission path. 4. The microwave module according to claim 2, further comprising: a second drawing-off device distributing the sampling pulse to the first and second sampling mixers, wherein the first amplifier is arranged upstream of the first drawing-off device in the transmission path. 5. The microwave module according to claim 4, wherein the first and second drawing-off devices are directional couplers. 6. The microwave module according to claim 4, wherein the first and second drawing-off devices are hybrid couplers. 7. The microwave module according to claim 1, further comprising: an adjustable attenuation device varying the transmitting power of the transmission signal, the adjustable attenuation device being arranged in the transmission path. 8. The microwave module according to claim 1, further comprising: a power divider distributing a sampling pulse to the first and second sampling mixers. 9. The microwave module according to claim 1, further comprising: a first memory storing the echo signal; and a second memory being separated from the first memory, the second memory storing the reference pulse. 10. The microwave module according to claim 9, wherein the reference pulse and the echo signal are stored in the same memory and wherein the echo signal is masked at a position of the reference pulse, and is replaced by the reference pulse. 11. The microwave module according to claim 1, further comprising: two transistors of a cascode amplifier; wherein the changeover switch is arranged between the two transistors. 12. The microwave module according to claim 1, further comprising: a first rectifier rectifying the decoupled reference signal; and a second rectifier rectifying the sampling pulse; wherein the first and second rectifiers are arranged upstream of the first sampling mixer. 13. The microwave module according to claim 12, wherein the first and second rectifiers are detectors. 14. The microwave module according to claim 1, further comprising: a second oscillator generating the reference pulse; and a delay device delaying the transmission signal on its way to one of the antenna and the probe. 15. The microwave module according to claim 14, wherein the delay device is a simple line in a multilayer printed circuit board. 16. A fill-level measuring device for determining a fill level in a tank, comprising: a microwave module and an antenna including (a) an echo signal unit providing an echo signal, (b) a reference-pulse generating unit generating a reference pulse, the reference-pulse generating unit including a first sampling mixer, the first sampling mixer converting a reference signal to the reference pulse in the form of a second intermediate-frequency signal, (c) a sampling pulse generator generating a sampling pulse, (d) a second sampling mixer situated in the echo signal unit, the second sampling mixer converting a receiving signal and the sampling pulse to the echo signal in the form of a first intermediate-frequency signal, (e) an intermediate-frequency amplifier, and (f) a changeover switch transmitting the first intermediate-frequency signal and the second intermediate-frequency signal to the intermediate-frequency amplifier, wherein the reference pulse and the echo signal are signals that are separate from each other. 17. A method for independently generating a reference pulse for a fill-level measuring device, comprising; providing an echo signal by generating a sample pulse and converting a receiving signal and the sampling pulse to the echo signal in the form of a first intermediate-frequency signal; generating a reference pulse using a sampling mixer, the first sampling mixer converting a reference signal to the reference pulse in the form of a second intermediate-frequency signal; and transmitting, by means of a changeover switch, the first intermediate-frequency signal and the second intermediate-frequency signal to the intermediate-frequency amplifier, wherein the reference pulse and the echo signal are signals that are separate from each other. 18. A microwave module for an independent reference pulse generation for a fill-level measuring device, comprising: an echo signal unit providing an echo signal; a reference-pulse generating unit generating a reference pulse, the reference-pulse generating unit including a separate oscillator solely generating the reference pulse; a sampling pulse generator generating a sampling pulse; and a second sampling mixer situated in the echo signal unit, the second sampling mixer convening a receiving signal and the sampling pulse to the echo signal, wherein the reference pulse and the echo signal are signals that are separate from each other.