Product specifications

6
Pulsed-RF Detection Techniques
Figure 3 shows an important measure of a pulsed RF signal and its relationship
between the time and frequency domain. When a signal is switched on and
off in the time domain (pulsed), the signal’s spectrum in the frequency domain
has a sin(x)/x response. The width of the lobes is inversely related to the pulse
width (PW). This means that as the pulses get shorter in duration, the spectral
energy is spread across a wider bandwidth. The spacing between the various
spectral components is equal to the pulse repetition frequency (PRF). If the PRF
is 10 kHz, then the spacing of the spectral components is 10 kHz. In the time
domain, the repetition of pulses is expressed as pulse repetition interval (PRI)
or pulse repetition period (PRP), which are two terms with the same meaning.
Another important measure of a pulsed RF signal is its duty cycle. This is the
amount of time the pulse is on, compared to the period of the pulses. A duty
cycle of 1 (100%) would be a CW signal. A duty cycle of 0.1 (10%) means that
the pulse is on for one-tenth of the overall pulse period. For a fixed pulse width,
increasing the PRF will increase the duty cycle. For a fixed PRF, increasing the
pulse width increases the duty cycle. Duty cycle will become an important
pulse parameter when we look at narrowband detection.
Figure 3. Pulsed-RF network analysis terminologies