Electronic safety of radars: how is their functioning ensured?

A fundamental field in information technology is the correctness of the software that has the task of controlling critical units. Generally, therefore, it is tested to ensure its reliability, otherwise it would be unreliable. One of the first sectors in which reliability analyzes have been applied since the 1960s is that of telecommunications . Reliability studies begin right from the design stages to ensure greater reliability: this is the case of radars, whose signals produced by the software and transferred to the controls are highly critical for the correct detection of the required coordinates.


To ensure correct operability, even during the operational phase of the radar itself, tests carried out using the Built-In Test Equipment (BITE) are used. BITE therefore defines those integrated test equipment for fault management and integrated diagnosis . In particular, this article describes:

  • the study of the testability of the BITE logics of a radar
  • the subdivision units of the BITE of a radar
  • the BITE of the radar receiving processor management unit (RRPMU)

Realization of the BITE logics of n radars and their functioning

The BITE logics of the radar are made up of 3 distinct sub-logics, such as Primary State logics, on-line BITE logic and off-line BITE logic . With primary status logics we refer to those logics that are active when the service power supply is active and provide, even in the absence of the Power-ON command, the status of the radar units in relation to any hardware failures of the same , of the links, of the power supply, of the overtemperatures and, in the case of operation of the apparatus, a summary of the status of these units against the BITE data.

The on-line BITE logics refer to those logics that are active only when the system, following a Power-On command, transitions into the Operational state and is periodically performed in parallel with the other radar activities . It consists of:

  • checks that do not require radar time. The units, through the Built in Test BIT system, check the operation of the subassemblies simultaneously with the execution of the radar activities;
  • checks that require radar time. The Receiver Management Computer (RMC) periodically schedules activities dedicated to monitoring the operating status of the units, allocating adequate time in the radar activity pre-scheduling cycle.

Finally, with Off-Line BITE logic, it is performed locally on the units during maintenance using (if necessary) off-line diagnostics for a more in-depth examination of the operating condition of the units and sub-assemblies making up the radar. It is intended to carry out performance monitoring and troubleshooting.

Subdivision of the groups constituting the units of BITE

From a BITE point of view, radar units can be divided into A, B and C type units . Type A Units only have a link to the Receiver Management Computer (RMC) via a Primary Status signal and consists of the following units:

  • Antenna Control & Power Distribution Unit (AC&PDU);
  • Cooling Unit (CU);
  • RRPMU Receiving Processor Management Unit (Cabinet only).

Type B Units have both a serial link to the Receiver Management Computer (RMC) and a Primary Status signal. The Primary Status signal is managed similarly to the type A units, ie by means of the same status logics (Normal, Alarm, Damaged, Fault) which are described in the BITE of the Radar Reception Processor Management Unit. The serial links to the Receiver Management Computer (RMC) are made via an Ethernet and fiber optic network.

Type C units, on the other hand, only have a serial link to the Receiver Management Computer (RMC) and are made up of the following components:

  • Signal Processor (SP), which processes digital signals into recurring instruction sequences;
  • Wave and Frequency Generator (FG), which generates predominantly sinusoidal signals with frequency control;
  • IF Intermediate Frequencies (IF-RX) or indirect detection (superheterodyne) receiver.

In particular, the Signal Processor has a dedicated serial link to the Receiver Management Computer (RMC), made using optical fiber. The Wave and Frequency Generator and the IF Receiver have a serial link (LDVS) towards the Receiver Management Computer (RMC).

Radar Receiving Processor Management Unit (RRPMU) BITE

The RRPMU is a basic unit of radar which contains a Wave and Frequency Generator (FG), IF Receiver (IF-RX), Signal Processor (SP), Receiver Management Computer (RMC), various power supplies electrical, fans, and minor items to control the cabinet environment . To determine the overall state of the RRPMU it is therefore necessary to determine the state of the units making up the RRRPMU.

The state of the RRPMU can therefore be normal, alarm, degraded or taste , according to the following considerations:

  • Normal: if the status of the FG, IF-RX, RMC and SP assemblies is Normal and no faults are detected by the RRPMU Primary Logic signal.
  • Alarm: if at least one unit of the RRPMU is Alarm and the others have Normal status.
  • Degraded: if at least one unit of the RRPMU is Degraded and the others have Normal or Alarm status. Furthermore, the Primary Logic signal must not dictate failures classified as Fault.
  • Fault: if the status of at least one unit of the RRPMU is Fault or the Primary Logic signal detects a failure classified as Fault.

The article Electronic safety of radars: how is their functioning ensured? was written on: Tech CuE | Close-up Engineering .