Radar System Parameters

The System page of a radar's Basic properties relates to general characteristics of the radar system being modeled, including a choice between monostatic and bistatic operation; frequency or wavelength (for monostatic systems); peak power (for monostatic systems); antenna options; system temperature; rain outage; and other gains and losses.

Monostatic vs. Bistatic Operation

Option buttons on the System page allow you to choose between Monostatic and Bistatic operation. Some of the selections in the following table depend upon that choice:

Type	Description
Monostatic/ Bistatic Operation	In a Monostatic operation, a common antenna is used for both transmitting and receiving. (Continuous Wave radars are modeled to use identical, co-located antennas.) In a Bistatic operation, the transmitting and receiving antennas may be separated by a considerable distance. If Bistatic is chosen, the other radars that can act as transmitters (listed together with their parent objects in the Bistatic Transmitter frame) are ungrayed.
Frequency/ Wavelength	This field defaults to 1 m wavelength, which corresponds to a frequency of 2.998 GHz. You can enter another wavelength or select Frequency from the drop-down menu and enter the desired frequency. This option is available only for a Monostatic operation. For a Bistatic operation, frequency/wavelength is determined by the other radar serving as the bistatic transmitter.
Peak Power	This is the peak output power of the transmitter. It is available only for a Monostatic operation. For a Bistatic operation, peak power is determined by the other radar serving as the bistatic transmitter. It defaults to 40 dBW.
Bistatic Transmitter	Select the radar that serves as the transmitter in a bistatic radar system. Only monostatic radars may serve as the bistatic transmitter.

Hint: When Bistatic operation is selected, all radars appearing in the Bistatic Transmitter frame are of the monostatic type.

Antenna Selection, Definition & Orientation

Modern radar antennas are, for the most part, highly similar to antennas used in radio communications. STK/Radar includes several of the antenna models used in STK/Communications. Click Antenna Setup... to select and define an antenna and set its orientation. Two radar antenna types (pencil beam and rectangular pattern) are provided for purely analytical purposes.

Environmental Factors

You can specify or calculate the System Temperature and set Rain Model parameters locally. You can also choose a refraction model for your radar analysis.

Radar analysis uses geometric Line Of Sight (LOS) calculations in the access analysis to determine object visibility. However, when the Use Refraction in Access Computations is enabled on the Refraction properties page, all access computations for that radar are based on the refracted LOS, not the geometric LOS. This may enable a radar antenna to see over the horizon objects.

Other Gain/Loss

To specify Post-Transmit Gains & Losses for a radar, click Other Gain/Loss Details....

Compute Jamming

Use this option to enable or disable the computation of jamming effects. This allows you to turn off jamming analysis temporarily without having to dismantle your jamming setup, i.e., it is not necessary to de-assign jammers, turn off constraints, etc. Disabling jamming computation will save you processing time if you want to make and test other changes in the scenario without having to recompute jamming each time. This can be especially advantageous in a scenario that includes many jammers.

Signal Power Spectral Density and Rf Spectrum Filters

You can enable power spectral density (PSD) analysis and RF spectrum filters on the radar object.

Radar objects use signal power spectral density analysis to compute the reflected signal power as seen by the radar receivers front-end bandwidth.

The fidelity of the radar system analysis is enhanced by taking into account the signal spectrum and the distribution of power across the frequency band.

Type	Description
Enable PSD Analysis	If enabled, STK computes the power spectral density based on the radar's operating mode, S/T pulsed or continuous wave. For a pulsed waveform, the PSD is computed to ±15 null points on the RF spectrum. The pulsed signal spectrum follows a sinc pattern. The first null point is at the 1/ pulse width (e.g., the default value for the pulse width is 1.0e^-7 seconds; the spectrum is computed to ±150 MHz. The spectrum sample rate is adaptive and is based on the spectrum bandwidth used by the signal. This insures that the spectrum is sampled at sufficient rate for accuracy. The S/T continuous mode models the carrier to be a pure sinc wave. By enabling PSD analysis, this can be changed to an impure carrier with a Gaussian power density distribution. The spectrum is spread to ±6 sigma over the bandwidth specified in the Power Spectral Density and RF Spectrum Filters group on the Radar Basic System properties page. PSD Analysis use will enhance the fidelity of the radar performance analysis. STK will compute the amount of RF power at the radar's transmitter and the transmitter filter due to the signal spectrum characteristics and the bandwidth. On the receive side of the radar, the received power is computed based on the incoming signal spectrum, the receive side filter characteristics and the bandwidth. PSD analysis also improves the radar performance analysis under jamming. The received jamming power is computed on the basis of the jammer signal spectrum, bandwidth, the radar's receive side filter and the bandwidth. The jamming power represents the unwanted signal power as seen by the radar's receiver. The pulsed radar signal spectrum is a train of sinc-shaped spectrums. The envelope of the peak amplitudes of these sinc spectrums also follow a sinc characteristic curve. A SincEnvSinc filter is available as a filter type to do match filtering on the radar signals.
Use Transmit Side Spectrum Filter	The transmit side filter of the RF spectrum allows the radar's power spectrum to be shaped to conform to a specified power distribution. See spectrum filters for details. Note: The transmit and receiver filters can be enabled and configured independently.
Use Receive Side Spectrum Filter	The receive side filter updates the spectrum shape of the incoming radar return signal. The filters can be used to enhance the spectral components or to suppress the unwanted jamming signal. See spectrum filters for a list of available filters.

Type

Description

Enable PSD Analysis

If enabled, STK computes the power spectral density based on the radar's operating mode, S/T pulsed or continuous wave.

For a pulsed waveform, the PSD is computed to ±15 null points on the RF spectrum. The pulsed signal spectrum follows a sinc pattern. The first null point is at the 1/ pulse width (e.g., the default value for the pulse width is 1.0e^-7 seconds; the spectrum is computed to ±150 MHz. The spectrum sample rate is adaptive and is based on the spectrum bandwidth used by the signal. This insures that the spectrum is sampled at sufficient rate for accuracy.

The S/T continuous mode models the carrier to be a pure sinc wave. By enabling PSD analysis, this can be changed to an impure carrier with a Gaussian power density distribution. The spectrum is spread to ±6 sigma over the bandwidth specified in the Power Spectral Density and RF Spectrum Filters group on the Radar Basic System properties page.

PSD Analysis use will enhance the fidelity of the radar performance analysis.

STK will compute the amount of RF power at the radar's transmitter and the transmitter filter due to the signal spectrum characteristics and the bandwidth.

On the receive side of the radar, the received power is computed based on the incoming signal spectrum, the receive side filter characteristics and the bandwidth. PSD analysis also improves the radar performance analysis under jamming. The received jamming power is computed on the basis of the jammer signal spectrum, bandwidth, the radar's receive side filter and the bandwidth. The jamming power represents the unwanted signal power as seen by the radar's receiver.

The pulsed radar signal spectrum is a train of sinc-shaped spectrums. The envelope of the peak amplitudes of these sinc spectrums also follow a sinc characteristic curve.

A SincEnvSinc filter is available as a filter type to do match filtering on the radar signals.

Use Transmit Side Spectrum Filter

The transmit side filter of the RF spectrum allows the radar's power spectrum to be shaped to conform to a specified power distribution. See spectrum filters for details.

Note: The transmit and receiver filters can be enabled and configured independently.

Use Receive Side Spectrum Filter

The receive side filter updates the spectrum shape of the incoming radar return signal. The filters can be used to enhance the spectral components or to suppress the unwanted jamming signal. See spectrum filters for a list of available filters.