Cw Sweeper Mode; One-Way Sweeps - Infinite Pasternack PE11S100 Series User Manual

User Manual | PE11S100X Series Synthesizer

4.4 CW Sweeper Mode

The internal PLL features a built-in frequency sweeper function, useful for test instrumentation, FMCW
sensors, automotive radars, and other applications.
Sweeper modes include:
a. Single-Step Ramp Mode
b. 1-Way Sweep Mode
c. 2-Way Sweep Mode (alternating positive and negative frequency ramps)
The sweep generator is enabled with ramp_enable in
through a series of discrete frequency values, which may be:
a. Single-stepped by individual triggers if ramp_singlestep
b. Stepped by an automatic sequencer if ramp_singlestep
Triggering of sweeps, or of steps in single-step mode, may be configured to operate as follows:
a. Triggered from TTL input on GPIO3 if
b. Triggered by setting ramp_trigg
c. Triggered with an automatically-generated internal trigger, if ramp_repeat_en
(Reg 14 h<3>) is set.
The sweep will begin at the current frequency value of the synthesizer, denoted as f0. The frequency step
size for the ramp is set by ramp_step
Δf
= ramp_step * f
step
The total number of ramp steps taken in a single sweep is given by ramp_steps_number
the initial ramp direction is set to be increasing or decreasing in frequency by clearing or setting ramp_
startdir_dn (Reg 14 h<4>) respectively. Setting ramp_singledir
sweep to the initial sweep direction only.
The final ramp frequency, ff, is given by f
- Δf
and f = f * ramp_steps_number for decreasing-frequency ramps. Unless in single-step mode, the
f 0 step
sweeper timebase, TREF, is the period of the divided reference f
total time to ramp from f
The user should be aware that the synthesized ramp is subject to normal phase-locked-loop dynamics. If
the loop bandwidth in use is much wider than the rate of the steps, then the locking will be very fast and the
ramp will have a staircase shape. As the update rate approaches the loop bandwidth, the loop will not fully
settle before a new frequency step is received. In this case, the swept output will have a small lag and will
sweep in a near-continuous fashion.

4.4.1 One-Way Sweeps

One-way sweeps are selected by enabling ramp_singledir
the sweeper will dwell at the final frequency, f
the synthesizer back to the initial frequency, f
10
Reg 14
(Reg 14
(Reg 15 h), with
24
/ 2
REF
+ Δf
= f
f 0
to f is T = T * ramp_steps_number.
0 f ramp REF
, until a new trigger is received. The second trigger will hop
f
. The third trigger will restart the sweep from f
0
Reg 14 h<1>. The sweep function cycles
(Reg 14
(Reg 14
h<5> = 1, or
h<2>), if ramp_trigg has previously been cleared, or
(Reg 14h<7>) restricts the direction of the
* ramp_steps_number for increasing frequency ramps
step
at the phase detector. So in and the
REF
(Reg 14h<7>). At the end of the ramp time, T
h<6>) is set, or
h<6>) is cleared
(Reg 16
.
0
pasternack.com
h), and
,
ramp