Siemens Aktiengesellschaft

Erwin Vachenauer

Bernd Mueller

Gerhard Wagner

Klaus V Pieverling

Dieter Leypold

An airport-surveillance system for determining the position and identification of aircraft (4) on the airfield which utilizes secondary radar and includes an interrogation station (1) installed on the airfield (3) and from which the interrogation signal is transmitted by way of a narrow sharply forcused beam of an antenna which scans the airfield and further includes transponding stations installed in the aircraft (4). The present invention provides accurate identification and location of the aircraft by utilizing a receiver which has a sharply focused antenna beam and which is geographically located a distance away from the interrogation antenna and wherein the replies from the transponder of the aircraft are received by the receiving antenna only when the interrogation and receiving antenna beams (2, 22) intersect. By scanning all locations of the airport, the position and identification of all aircraft on the airport can be determined. A modification of the invention provides that instead of or in addition to the receiving station having a narrow beam antenna a number of receivers (5, 6 and 7) having omni-directional receiving antennas can be mounted at different locations on the airfield for determining the aircraft positions by using hyperbola locating techniques. The airport surveillance system of the invention is particularly suitable for large airports.

Airport-surveillance system

A circuit for the comparative vector measurement of keyed radio signal pulses, in particular DME pulses which arrive virtually simultaneously in a plurality of receivers and which can exhibit large level differences is utilized where, in each receiver, the pulses are fed to a switching amplifier which has an amplification which is adjustable in discrete stages and the reduction of which is effected automatically with the rise in the leading edge of the relevant signal pulse, and where, when the relevant switching amplifier of the receivers has been traversed, at a specific measuring time which is common to all receivers, the instantaneous amplitudes and instantaneous phases of the measuring signals are measured, the circuit providing that the pulses are fed to the switching amplifier by way of a delay device and, that for the setting of the amplification of the switching amplifier, a control circuit is provided which is directly fed with the radio pulses and which comprises a logarithmic amplifier and a subsequently connected analog-digital converter which is constructed as a comparator chain operating in parallel operation.

Circuit for the comparative vector measurement of radio signal pulses

An amplifier circuit for the unadulterated transmission of phase information of a supplied ac voltage signal over a large dynamic range includes a series connection of a series of similar amplifier stages each of which is followed by a symmetrical limiter. The amplifier operates as a logarithmic amplifier for maintaining the amplitude information of the supplied ac signal. Each of the amplifier stages comprise an emitter-base transistor amplifier circuit having negative feedback and an output circuit which contains a resonant circuit which is strongly damped by an attenuating resistor and whose capacitance is formed by a trimmer capacitor connected in parallel to a pair of diodes. The diodes are connected in anti-parallel relation to one another and represent the limiter. The capacitance is adjustable for purpose of impedance adjustment and is set in such a manner that the resultant resonant circuit impedance is capacitive.

High dynamic phase-accurate alternating voltage amplifier operating as a

A method for the comparative vector measurement of keyed radio signal pulses arriving nearly simultaneously at several radio receivers, particularly DME pulses, which can exhibit great level differences. The pulses at each receiver are individually fed to an amplifier or attenuator having an amplification or attenuation, respectively, which can be adjusted in distinct steps, whose reduction or increase, respectively, takes place automatically with the rise of the leading edge of the respective signal pulse. After passing through the respective amplifier or attenuator of the receivers, the instantaneous amplitudes of the measuring signals are measured at a specific measured time which is common to all receivers. In each receiver, an individual measuring time is ascertained in such a way that switching pulses derived from the step-wise amplification reduction of the amplifier (or the step-wise attenuation increase of the attenuator) are fed to a retriggerable monostable multivibrator having a specific holding time, during the operating sequence of which the individual measuring time of each receiver is provided. After this measuring time, or after the measuring time, to all receivers, an additional step-wise reduction in amplification or increase in attenuation at the respective receiver is blocked. An individual measuring time, selected with reference to the arrival sequence, is used as the common measuring time for the simultaneous measurement of the receiving vectors of all receivers.

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Haar, Germany

Erwin Vachenauer