Source Description
IF Clock Frequency The sampling clock frequency is fully programmable 50 ... 100 MHz with microhertz
(μHz) resolution.
You can choose the clock frequency independently of the original reference clock
frequency that produces it; they do not have to be small integer multiples of each
other.
See 4.2.8.1 Choosing A/D Sample Rate or Tx Synthesis Rate (page 65)
The RVP901 IFDR sampling clock is derived from the master clock source. The
architecture minimizes jitter, while allowing full
flexibility in selecting sampling
frequencies 50 ... 100 MHz. The output clock runs at the same frequency as the
sampling clock.
Clock Jitter IF clock jitter is sub-picosecond allowing the system to maximize the benefits of the
16-bit A/D converters.
When RVP900 is used in a klystron system, or a synchronous radar, the radar COHO is
supplied to the RVP901 IFDR, so that the sampling clock can digitally lock to it. The COHO
phase is measured at the beginning of each transmitted pulse, and is used to lock the
subsequent (I,Q) data for that pulse. The COHO phase is measured relative to the RVP901
IFDR internal stable sampling clock, which is user selectable. The internal sampling clock is
not
aected by the application of the COHO. A/D samples of the COHO are obtained at the
fixed sampling rate, and the (I,Q) data are digitally locked downstream in the RVP900 IF-
to-I/Q processing chain (see 3.1.2 RVP901 IFDR IF to I and Q Processing (page 23)). The
procedure is identical to the manner in which phase is recovered in a magnetron system,
except that the COHO signal is used in place of a sample of the transmit burst.
There are two concerns that may occur when RVP900 is used in the above manner within a
synchronous radar system. Both concerns are the result of the RVP901 IFDR sampling clock
being asynchronous with the radar system clock.
Table 21 Clock Generator Concerns in a Synchronous Radar System
Concern Description
RVP900 Generates the
Radar Trigger
The trigger signals supplied by RVP900 are synchronous with the RVP901 IFDR data
sampling clock.
This is accomplished by a clock recovery PLL that provides on-board timing, which is
identical to the sampling clock in the RVP901 IFDR. Since the RVP901 IFDR sampling
clock is asynchronous with the radar clocks, RVP900 trigger outputs are similarly
asynchronous. The result is that each transmitted pulse envelope is triggered
independently of the COHO phase. The transmitted pulse is still synchronous, but
the precise alignment of the amplitude modulated envelope varies.
In almost all cases, the exact placement of the transmitter’s amplitude envelope
does not
aect the overall system stability, nor the ability of RVP900 to reject
ground clutter and to process multi-mode return signals. For this reason, a
synchronous radar system, which is triggered using RVP900 triggers, still performs
optimally using the standard digital COHO locking techniques. In spite of this, some
system designers may still prefer that the amplitude envelope be locked to the
COHO.
RVP900 User Guide M211322EN-J
64
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