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Module 1.3: Radar Input Section

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Input Section

The term ‘Input Section’ refers to the parts an electronic system (in our case a Radar) which are used to receive a signal ‘in’.

Block diagram of a simple RADAR system
Block diagram of a simple RADAR system

Antenna

This is the same antenna used for transmitting. It collects electromagnetic energy from the air and converts it into electrical signals which are then fed to the receiver.

Duplexer

When travelling to the receiver, the converted signal passes through the duplexer. The duplexer ‘switch’ is now set to receive mode with the purpose to make sure that the very small received signals are not interfered with or ‘covered up’ by the noisy, high power electronics of the transmitter.

The signal received will be very small, so the duplexer should have both the lowest attenuation (or resistance) possible and be as physically close to the receiver as it can

Receiver

The receiver is an amplifier. The purpose of which is to make the signal collected by the antenna larger.

The signal received by the Radar would be very small and needs to be amplified before it can be used. It is also important that the receiver is a very ‘clean’ amplifier and does not introduce any additional noise into the system (if it did, the noise would be amplified too and could obscure some of the signal you are looking for).

Synchroniser

The synchroniser measures the time delay since the pulse was transmitted. As a Radar pulse will travel at a constant speed in air, the Radar system is able to measure the range (distance) between the position of the Radar and the location of any objects detected.

Display

The display is where the signal is converted into a visual format which enables you to ‘see’ targets.

The display could be a computer or an instrument screen.

Block diagram showing he input section, of a simple RADAR system

Heading: Receiving a pulse

  • The Radar would have already sent a pulse and switched into ‘receive’ mode.
  • Any reflections are collected by the antenna and transformed into electrical energy.
  • The electrical energy then travels through the Duplexer (already switched to isolate the ‘noisy’ transmitting electronics to keep them as separate as possible from received signals) into the receiver.
  • These reflections would be very small, so it is important that they encounter minimal attenuation (resistance) between the antenna and receiver.
  • In the receiver the signal is amplified (made larger) so it can be used.
  • The synchroniser measures the time delay since the signal was transmitted.
  • A response is then displayed.
Our Most Common Questions

Frequently Asked Questions

If your question isn't answered here, please do contact us for more information. 
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What can a Ground Penetrating Radar survey detect?

With GPR, you can detect a wide range of objects below ground level, including both metallic and non-metallic objects such as plastic pipework. GPR will also identify and map any voids below the surface, such as air pockets or mine shafts, as well as any other irregularities including concrete and previously excavated or back-filled areas.

Will GPR compromise safety on my site?

GPR equipment emits an electromagnetic pulse into the ground and records the reflected signals from subsurface structures and voids. It is entirely non-destructive and will not break the ground’s surface or affect any objects below. What’s more, it doesn’t emit any harmful levels of radiation, nor are there any other by-products created throughout the process. This means it’s entirely safe to use by its operators, and on sites of any type, including those open to the public.

Is a GPR survey 100% accurate?

While GPR is one of the most effective methods of non-destructive testing available, it can never be 100% accurate. One factor that can adversely affect the accuracy levels include the type of soil being surveyed. Clay soils and soils that contain high levels of salt or minerals can obstruct the GPR reading. Another factor is the experience of the equipment’s operator: interpreting the data collected can be complex, which is why it’s beneficial to commission surveys from an expert firm.

Is GPR equipment difficult to use?

The equipment itself is not difficult to use, but the interpretation of the data recorded tends to be complicated. The results of a GPR survey aren’t automatically translated into an easy-to-understand picture of what lies below the surface; instead, it’s a series of lines and waves and it can take both training and years of practice to master the art of correctly reading the output. Often, it is the experience of the equipment’s operator that plays the most significant role in the accuracy of the results GPR can achieve.

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