ADF5902 datasheet(37/39 Pages) AD

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Data Sheet

ADF5902

Rev. 0 | Page 37 of 39

Ramp Complete and Ramp-Down Signals to MUXOUT

Figure 50 shows the ramp complete signal on MUXOUT.

TIME

Figure 50. Ramp Complete Signal on MUXOUT

To activate this function, set Bits[DB15:DB12] in Register R3

to 1111, and set Bits[DB19:DB5] in Register R4 to 0x00C0.

Figure 51 shows the ramp-down signal on MUXOUT.

TIME

Figure 51. Ramp-Down Signal on MUXOUT

To activate this function, set Bits[DB15:DB12] in Register R3

to 1111, and set Bits[DB19:DB5] in Register R4 to 0x0100.

External Control of Ramp Steps

The internal ramp clock can be bypassed and each step can be

triggered by a pulse on the TX_DATA pin. This process allows

transparent control of each step. Enable this feature by setting

Bit DB30 in Register R14 to 1.

TIME

TX_DATA

RFOUT

TIME

Figure 52. External Control of Ramp Steps

APPLICATION OF THE ADF5902 IN FMCW RADAR

Figure 53 shows the application of the ADF5902 in a frequency

modulated continuous wave (FMCW) radar system.

In the FMCW radar system, the ADF5902 generates the

sawtooth or triangle ramps necessary for this type of radar to

operate.

The ADF5902 CPOUT pin controls the VTUNE pin on the ADF5902

transmitter MMIC and thus the frequency of the VCO and the

transmitter output signal on TXOUT1 or TXOUT2. The LO signal

from the ADF5902 is fed to the LO input on the ADF5904.

The ADF5904 downconverts the signal from the four receiver

antennas to baseband with the LO signal from the transmitter

MMIC.

The downconverted baseband signals from the four receiver

channels on the ADF5904 are fed to the ADAR7251 4-channel,

continuous time, Σ-Δ ADC.

A digital signal processor (DSP) follows the ADC to handle the

target information processing.

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