Analog Devices ADRV9005 Reference Manual page 138

Reference Manual
FREQUENCY HOPPING
NCO only. It adds an offset to the current LO frequency. Note that IF operation is supported in the regular Rx FH mode. The IF frequencies
are also defined using rx1OffsetFrequencyHz and rx2OffsetFrequencyHz. The difference is that in the regular mode, both the LO and NCO
frequencies are changed, while in the NCO-only mode, only the NCO frequencies are changed but LO frequencies are not affected. This is the
fundamental difference between the regular Rx FH mode and NCO-only Rx FH mode.
The NCO-only mode changes the NCO frequency at the beginning of each hop frame based on the hopping table entry it is using. Also, the
NCO-only mode can be utilized to perform frequency changes or "hops" anytime within a hop frame by using a GPIO pin. To use this feature,
assign a GPIO to trigger the NCO change. Update the desired Rx frequency offset using adi_adrv9001_fh_RxOffsetFrequency_Set() API at
any point, but it does not take effect until the NCO change pin is toggled (both rising and falling edges). When the GPIO pin is toggled, the
offset frequency set through the API is used and the original offset frequency defined in the hopping table is ignored. At the start of the next
frame, the NCO frequency is first obtained from the hopping table until the NCO change pin is toggled.
Figure 132 shows a timing diagram for an NCO-only example. This timing diagram examines the actual RF frequency of the Rx1 port. For
simplicity, all frames are for Rx1. This figure shows two frames: "n" and "n+1". The first point to note here is that the carrier frequency for each
frame is taken from the FH table and does not change during the frame. The dynamic elements of the diagram are the Rx1 offset frequency,
the NCO 1 change pin, and the Rx1 output frequency. Throughout the frames, the BBIC loads new values for the Rx1 offset frequency. The first
offset frequency is retrieved from the hopping table. It adds an offset to the Rx1 output frequency, which does not change until the NCO 1 pin
is toggled. When the NCO 1 change pin is toggled, the offset frequency is updated based on the value set through the API, and thus the Rx1
output frequency is shifted correspondingly.
Table 58. Simplified Hop Table for NCO-Only Hop Example
Index
n
n+1
Frequency Hopping with PFIR Switching
The frequency hopping with PFIR switching allows the changing of the programmable FIR filter at each hop frame. Each channel (Rx1, Tx1,
Rx2, Tx2) has two PFIRs associated with it: primary and secondary PFIRs. At each hop, the PFIRs will be automatically switched between.
Figure 133 shows the operation of the PFIR switching.
analog.com
Carrier Frequency (MHz)
500
600
Figure 132. NCO-Only Hop Timing Diagram Example
Figure 133. FH with PFIR Switching Operation
ADRV9001
Rx1 Offset Frequency (kHz)
500
500
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