Design 2
Jack Browne, Technical Director
Pulse statistic time and frequency domain analysis
Off time
omitted from trend Radar
pulses
Amplitude
Amplitude 400 Hz
RADAR-SYSTEM TESTING has never been routine. Measurements have often combined expensive microwave test equipment, including synthesized signal sources and spectrum analyzers, well as experience and a little bit of luck. Fortunately, with the RSA6100A Series of real-time spectrum analyzers from Tektronix ( www.tektronix.com), the accuracy of these measurements no longer has to be left to fate, as the RSA6100A provides coverage through 14 GHz with instantaneously intermediate-frequency (IF) bandwidths as wide as 110 MHz and dynamic range of 73 dB.
The signal path of the RSA6100A includes a mixer and local-oscillator (LO)-based RF down-
Trend Frequency
Trend analysis Time spectrum
can perform an FFT on trend measurement data to convert the results into frequency-domain displays that can better show the modulation.
Two versions of the RSA6100A real-time spectrum analyzer are available, with 40- and 110-MHz IF bandwidths. The wider-bandwidth model allows measurements of very narrow pulses without distortion (inadequate IF bandwidth will increase the perceived rise time of a short-duration pulse). The RSA6100A features a variety of automatic pulse characterization functions, such as on/off ratio, rise time, fall time, pulse width, and duty cycle.
Editor’s Note: This article has been abstracted from a 16-page application note from Tektronix, Inc., “Advanced Radar Testing with the RSA6100A Series Real-Time Spectrum Analyzer.” A copy of the note can be ordered or downloaded from the Tektronix website at www.tektronix.com.
converter with extremely wide (40 or 110 MHz) IF bandwidth that covers 9 kHz to 14 GHz. The front end uses switched bandpass filters for image and spurious rejection and feeds a high-speed analog-to-digital converter (ADC). The analyzer borrows the unique digital phosphor display technology (DPX) of the company’s high-speed digital oscilloscopes for the display screen, with technology that can process more than 48,000 spectral measurements per second to capture even short-duration events. The PDX display processor com-presses the 48,000 spectrum measurements per second into approximately 33 screen updates per second using a color-graded display. The color and intensity of each pixel in the display (Fig. 1) is based on the number of times that energy s found at each pixel location during a display frame.
The analyzer’s pulse trace display can be used for simplified pulse rise-time and fall-time measurements, using an automatic scaling feature. A pulse statistics display can perform an analysis on a series of pulses and then view a Fast Fourier Transform (FFT) of the results for further analysis.
Built-in trend-analysis functions (Fig. 2) make it possible to isolate unintentional phase or amplitude modulation on radar pulses that might be otherwise impossible to identify with a traditional swept-tuned spectrum analyzer. The RSA6100A
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