RFeye supports advanced techniques for direction finding and geolocation of suspicious or unauthorised transmitters

The RFeye receiver can be used to perform advanced geolocation measurements including TDOA (Time Difference of Arrival), AOA (Angle of Arrival) and POA (Power on Arrival). These can be applied either in real time or to recorded data.

We believe that the most effective and reliable way to pinpoint transmitters of all types is to overlay these techniques at multiple receiver sites.

The RFeye can work as a single channel system or by adding nodes a multi-channel system with all receivers located close to the antennas in a roof box, on a mast or roof top. Co-location of receivers and antennas reduces cable runs and cable losses greatly improving system performance.

Increasing the number of channels allows the network of nodes at a single site to simultaneously monitor increasing the probability of intercept (POI) using all three geo location techniques.

Each of these techniques has its advantages for particular sites and types of transmitter:

TDOA and POA measurements are multilateration methods requiring three or more receiver points. All receivers are synchronised in time to allow simultaneous spectrum sweeps for precise geolocation based on time difference of arrival (TDOA) or relative power on arrival (POA) at each receiver point. RFeye nodes can be accurately synchronised to <10ns RMS accuracy using SyncLinc connector modules or to 35ns using GPS.

TDOA involves complex algorithms and is particularly well suited for deployments over large areas where receivers are further apart enabling greater differences in time of arrival at each receiver. TDOA can be very effectively used with the low noise RFeye for locating even low power signals using the correlative properties of the data.

Below is an example of TDOA geolocation of a target signal using a network of RFeyes synchronised using GPS. The colouration represents the calculated probability of transmitter location, which improves as the target signal threshold is increased (click for larger images):

POA is well suited for in-building scenarios with a relatively high density of receivers where signal sources are closer to the receivers. This makes it an ideal technique for In-Place Monitoring Systems where the sensitivity and rapid sweep of the RFeye enables very high probability of intercept of suspicious signals.

AOA measurement is a relatively simple method for determining the direction of propagation of an RF signal. AOA can be reliably measured using a single receiver and a directional antenna array. RFeye AOA arrays have tight coupling between the RFeye receiver and the antenna switch, thereby allowing accurate bearings to be calculated based on even the shortest of transmission bursts.

RFeye DF systems can be configured to enable overlay of all three techniques, where appropriate, for increasing the probability of geolocating even very low power or transient signals.