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RF & Wireless Figure 3:

RF & Wireless Figure 3: PD radar example phase variations containing the Doppler frequency that conveys relative velocity. For a pulsed- Doppler (PD) radar, range is still measured by signal propagation time. To measure both range and relative velocity, the pulse-repetition frequency is an important parameter. There are many tradeoffs to be considered when deciding which architecture and waveform modulation technology delivers the necessary performance while maintaining development and production cost goals. These requirements can be met with VSS software, which is dedicated to RF system design and implementation, offering a toolbox of commonly calledfor simulation technologies and radio block/signal processing models, along with support for user-developed coding. VSS software is an RF and wireless communications and radar systems design solution that provides the simulation and detailed modeling of RF and digital signal processing (DSP) components necessary to accurately represent the signal generation, transmission, antenna, T/R switching, clutter, noise, jamming, receiving, signal processing, and channel model design challenges and analysis requirements for today’s advanced radar systems. The VSS workspace example in Figure 3 demonstrates a possible ACC radar architecture, modulation scheme, channel modeling and measurement configuration. This workspace includes a pulse-Doppler (PD) radar system design with signal generator, RF transmitter, antenna, clutters, RF receiver, moving target detection (MTD), constant false alarm rate (CFAR) processor, and signal Figure 4: RF transmitter block 60 hf-praxis 12/2018

RF & Wireless Figure 5: Subcircuit defining transmit and receive antennas, channel, and target with swept distance to radar detector for simulation purposes. The chirp signal level is set to 0 dBm, PRF = 2 kHz and DUTY = 25 percent. The target model is defined by the Doppler frequency offset and target distance, and angles of arrival (THETA/PHI) are specified in a data file and vary over time. The Doppler frequency and channel delay were generated to describe the target return signal with different velocities and distance, while the radar clutter model can be included, and the power spectrum can be shaped. In this example, the clutter magnitude distribution was set to Rayleigh and the clutter power spectrum was formed by a Weibull probability distribution. The RF transmitter in Figure 4 includes oscillators, mixers, amplifiers, and filters, whereas the gain, bandwidth, and carrier frequency were specified based on the requirements of the system or actual hardware performance as provided by the RF design team. Likewise, the RF receiver includes oscillators, mixers, amplifiers and filters with gain, bandwidth and carrier frequency specified according to the system requirements. Co-simulation with the Microwave Office circuit simulation software is possible as the transceiver front-end design details become available. As will be discussed later, the interaction between the transceiver electronics and a beamforming antenna array can be analyzed via circuit, system, and EM co-simulation. To detect the moving object more effectively, MTD is used. The MTD is based on a highperformance signal processing algorithm for PD radar. A bank of Doppler filters or FFT operators cover all possible expected target Doppler shifts and the output of the MTD is used for the CFAR processing. In this particular example, measurements for detection rate, and CFAR are provided. The radar signal waveform must be measured in the time domain at the receiver input. Since the target return signal is often blocked by clutter, jamming, and noise, detection in the time domain is not possible and an MTD is used to perform the Doppler and range detection in the frequency domain. In the MTD model, the data is grouped for corresponding target range and Doppler frequency. Afterwards, a CFAR processor is used to set the decision threshold based on the required probabilities of detection and false alarm, as shown in Figure 5. This relatively simple design can be used as a template for different PD applications. The radar signal is a function of pulse repetition frequency (PRF), power, and pulse width (duty cycle). These parameters can be modified for different cases. In the simulation, the radar signal also can be replaced by any defined Figure 6: Results of the simulation are shown in the system metrics graph hf-praxis 12/2018 61