| 摘要 |
In determining distances using electro-magnetic waves, in particular when determining short distances in a radar installation, from a transmitter (1) a frequency modulated signal is issued, which can be modulated by a sinusoidal or triangular signal and the modulation of which in addition can have a frequency varying in time. In the receiver part (11) of the installation, in a mixer (9) a received echo signal is mixed with a leak signal (7) from the transmitter side (4). From the obtained spectrum signals are extracted around several different multiples of the modulation frequency by means of coherent detectors (19a, 19b) in different signal processing branches (a, b). After the mixing also a product modulation using a reference signal in the shape of a suitable sine signal can be executed. The signals from the signal processing branches (a, b) are conducted to a device (27), which executes a weighted production of a difference. The difference signal obtains, when using suitable control signals (vref,a, vref,b) to the coherent detectors (19a, 19b), a strongly increasing signal strength, when the installation increases the object, which causes the echo signal. The control signals to the detectors are selected, so that different special linear combinations are selected among tones in the incoming signal, whereby desired distance dependencies can be achieved. |
