In some examples, a system includes a digital-to-analog converter (DAC) configured to operate at a clock rate; a mixer configured to up-convert an intermediate-frequency (IF) signal from the DAC to a radio-frequency (RF) signal based on a local oscillator (LO) signal; and an RF filter configured to generate a filtered signal by at least removing, from the RF signal, frequency components greater than a difference between a frequency of the LO signal and one-half of the clock rate and less than a sum of a frequency of the LO signal and one-half of the clock rate, wherein an output node of the RF filter is configured to be coupled to an antenna for transmission of the filtered signal.

A method for detecting conflicts in the II/SI identification code of radars nearby a secondary mode-S radar, includes at least: a first step wherein the radar detects unsolicited unsynchronized replies, i.e. fruits, in a region of extended radar coverage; a second step wherein the radar detects a conflict in II/SI code by analyzing geographic regions of radar coverage common to the radar and to at least one nearby radar, a conflict being detected if the radar: detects, in the region of extended coverage, the presence of fruits that have as source the nearby radar; observes the absence of fruits caused by the nearby radar in that region of radar coverage of the radar which does not overlap with the region of radar coverage of the nearby radar; the region of overlap between the radar coverage of the radar and the radar coverage of the nearby radar forming a region of conflict in II/SI code.

A density of Mode S interrogations and responses in the environment covered by a secondary radar is characterized according to the following steps: a first step wherein the radar: detects and locates Mode S targets by way of their synchronous responses to the interrogations emitted by the radar; detects asynchronous responses emitted by the Mode S targets, and not elicited by the radar; for each target, associates its asynchronous responses with its synchronous response to the radar; a second step wherein the radar: based on the association, determines the response rate of each target by counting the number of synchronous and asynchronous responses received from the target per given time period; with the environment being divided into elementary space cells, determines the response rate per cell by counting the number of synchronous and asynchronous responses received by each target in each cell, the rate characterizing the density of Mode S interrogations per cell.

Computer assistance in interval management may be beneficial in a number of ways. For example, digital communication of interval management instructions or information related to interval management may beneficially be communicated to aircraft with respect to other aircraft. This information may be communicated overlaid on air traffic control (ATC) communications, or otherwise. A method can include, for example, obtaining a spacing goal for an aircraft relative to a target aircraft. The method can also include determining clearance instructions for the aircraft, wherein the speed guidance is based on the spacing goal. The method can further include transmitting the clearance instructions in a computer-readable format to the aircraft. The instructions can be provided by an overlay-modulated signal of a provided modulated ATC signal. The instructions can be configured to enable control of the aircraft to achieve the spacing goal.

Embodiments of the present invention disclose systems and methods for providing an ATC Overlay data link. Through embodiments of the present invention, existing ATC (or other) modulated signals using existing standard frequencies may be utilized to transmit (e.g., from an aircraft transponder) additional information in a manner that does not render the transmitted signal unrecognizable by legacy ATC equipment. Legacy equipment will be able to demodulate and decode information that was encoded in the transmitted signal in accordance with preexisting standard modulation formats, and updated equipment can also extract the additional information that was overlaid on transmitted signals.

A system provides a way to determine angle of bearing to a target receiver/transmitter relative to plural beacon stations with rotating directional radiation patterns. The target is “cooperative” in that it transmits a “report” message when the target receives maximum signal strength from a beacon station. Triangulation from multiple beacon transmitter sites can be used to determine the target's position.

An adaptive interrogation method is provided, the method including determining application of an adaptive whisper shout interrogation sequence. The determination may be predictive and based on an anticipation of garbled replies or may be reactive and based on a plurality of replies to an initial ATCRBS interrogation, there being interference between the replies such that the replies are unable to be properly decoded. The adaptive whisper shout interrogation sequence includes adapting a subsequent ATCRBS interrogation. The adaptation may be a change in an amplitude difference between an interrogation pulse and a suppression pulse of the subsequent ATCRBS interrogation (i.e. a bin width), as compared to the initial ATCRBS interrogation; or the adaptation may be a change in a power of the subsequent ATCRBS interrogation as compared to the initial ATCRBS interrogation. The subsequent ATCRBS interrogation is then transmitted, and one or more replies are received.

Various communication systems may benefit from enhanced reception methods. For example, various transponders and surveillance systems may benefit from reception methods that can distinguish between overlapping pulses from multiple sources. A method can include receiving, at an antenna, a first series of pulses from a first source. The method can also include receiving, at the antenna, a second series of pulses from a second source. The first series and the second series can at least partially overlap each other. The method can further include de-interleaving the first series from the second series using at least one non-time-domain technique.

A density of Mode S interrogations and responses in the environment covered by a secondary radar is characterized according to the following steps: a first step wherein the radar: detects and locates Mode S targets by way of their synchronous responses to the interrogations emitted by the radar; detects asynchronous responses emitted by the Mode S targets, and not elicited by the radar; for each target, associates its asynchronous responses with its synchronous response to the radar; a second step wherein the radar: based on the association, determines the response rate of each target by counting the number of synchronous and asynchronous responses received from the target per given time period; with the environment being divided into elementary space cells, determines the response rate per cell by counting the number of synchronous and asynchronous responses received by each target in each cell, the rate characterizing the density of Mode S interrogations per cell.

Various communication systems may benefit from enhanced reception methods. For example, various transponders and surveillance systems may benefit from reception methods that can distinguish between overlapping pulses from multiple sources. A method can include receiving, at an antenna, a first series of pulses from a first source. The method can also include receiving, at the antenna, a second series of pulses from a second source. The first series and the second series can at least partially overlap each other. The method can further include de-interleaving the first series from the second series using at least one non-time-domain technique.