FreeScopes Basic I - Description

FreeScopes Basic I is the basic configuration of a Virtual Radar Control Center and of a Digital Signal Processing and Configuration Environment, allowing for control and visualization of all compatible sensors, including the 8 GHz pulse radar, the 24 GHz FMCW, the sonar extension and various simulators.

The FreeScopes Basic I software includes the modular hardware control environment, which controls all components of the radar training system's hardware. It includes a user interface for the trainer / teacher where specific hardware features can be controlled.

Many users are enabled to do manipulations independently and concurrently on their computers, treating live or prerecorded raw data (I/Q data). Free floating panels of the FreeScopes Control Center allow each student to set up his own block diagram and scopes (A-Scopes, B-Scopes, PPI-Scopes etc.), visualizing the signal conversion chain from beginning to end.

Apart from the scopes, it includes important filters / algorithms such as Suppress Source, STC, one-dimensional CFAR and FFT, MTI etc.

FreeScopes has real access to the radar's live raw data. The variety of possible exercises is only limited by the creativity of the teacher. Here are some examples:

Setting up a block diagram for Pulse, Doppler or FMCW radar
Using A-Scopes, B-Scopes and PPI Scope correctly
Application of Sensitivity Time Control (STC), Source Suppress, Threshold
Understanding the radar equation
Impact of transmitted power, antenna gain, RCS, target angle or shape, material or range on the received signal
Moving from the Frequency to the Time Domain
Comparing static threshold and constant false alarm rate (CFAR)
Applying I & Q signals
Applying and analyzing moving target indication to capture and focus on moving objects
Experimentally determining the antenna beam width

Teacher Panel

The teacher panel allows to set important radar features such as

Frames per second communicated from the radar to the individual students (FreeScope users)
Transmitter power
Motor start angle
Motor stop angle
North shift

The access to the teacher panel is restricted to the teacher. It is also the environment where updates can be installed with a single mouseclick.

A-Scope

The A-Scope is the first scope provided in FreeScopes Basic I. It is a free floating panels which can be used many times concurrently.

The A-Scope is provided as block in the block diagram and as scope to display live or recorded data.

The A-Scope has the possibility to display amplitudes across the range. The Threshold function allows to cut off noise and small clutter and to limit the signal on the upper end. Axis _min/max allows to select a specific section on the y axis. This can be also done manually by moving the mouse vertically (y-axis) or horizontally (x-axis).
The A-Scope can read I-data, Q-data and Magnitude data.

PPI-Scope

The Plan-Position-Indicator (also referred to as PPI or PPI-Scope) has the possibility to define

the maximal range
the contrast
the maximum and minimum threshold

These three features help to clean the image.

B-Scope

The B-Scope can be imagined as an unfolded PPI-Scope. It has the same features:

the maximal range
the contrast
the maximum and minimum threshold

Tx-Power-Control

The transceiver power control allows to vary the emission power (T_x). The system can vary between min, medium and max. The actual emission power T_x depends on the connected radar.

Source Suppression

The Suppress Source function allows to clean the scopes from the strong reflections of the radar source. This feature will impact A-Scopes, B-Scopes and PPI-Scope alike.

Sensitivity Time Control (STC)

The echo power of a radar digresses by 1/R4 along the range. STC compensates for this effect. The settings allow to change the exponent of the amplification along the range in between the values 0.5 and 2.5.

Theshold

FreeScopes provides a threshold block for static thresholding. In contrast to the threshold features within the Scopes, this block sets a threshold globally for the complete signal processing chain which comes after this block.

CFAR (1D)

The FreeScopes Basic I package includes a 1-dimensional version of the CFAR function. There are various variants of algorithms for the detection of the false alarm rate. We used the perhaps most common version. It has the following parameters:

alpha - defining the threshold for the probability of false alarm (pfa) and detection (pf)
window - the size of the observation window to estimate the noise floor (noise power)
guard cells - they are the cells around the CUT which we ignore because of side-lobes from the target.

Fast Fourier Transform (1D)

To operate with an FMCW radar in the time domain, data needs to be converted with the help of a one-dimensional FFT. This block is also called Range-FFT

I & Q Data

The output of the radar are the IQ signals. The can either be read as magnitude (this is how the scopes read them by default), or filtered as I-Signal or as Q-Signal

Moving Target Indication

The MTI function is vital to detect and follow moving targets. The order defines which previous pulses will be compared with the current.