R2000 datasheet(20/75 Pages) ETC

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Indy® R2000 Electrical, Mechanical, & Thermal Specification

Figure 4-5: Self-jammer Cancellation Grid and Calibration Examples

0,0

15,15

15,-15

-15,15

-15,-15

Coarse full scan

3x3 matrix scan

Step size = 4

Scan size = 3

Step size = 1

Scan size = 1

Origin

The scan type is defined by the origin, the scan size, and the scan step as described in Figure 4-5. For a full scan,

the origin (register 0x151) is typically set to zero, the scan size to three, and step size to four (register 0x152). When

the scan is triggered, the control block evaluates the self-jammer suppression for all the points corresponding to the

blue settings. The value of the best setting is returned in register 0x154. To perform a 3x3 matrix scan around the

previous best setting,

the scan and step sizes are both set to one and the scan retriggered with the “Use current

settings as origin” flag set. The configuration of the scans determines the calibration time. If the data path sample

rate is 3 MSps and the digital filter is bypassed during SJC calibration, suitable settling and measurement durations

are 16 and 8 samples, respectively. These sampling durations correspond to 5.3 and 2.6

μs. Performing a coarse full

scan requires a total of 49 measurements, and take 392

μs. A single 3x3 matrix scan will take 72 μs. To ensure

optimal settings, repeat the matrix scan a few times. Ideally, you should repeat the 3x3 matrix scan periodically to

allow the system to track.

5.1.6 Receive Baseband Interface

The Indy R2000 uses an AC coupling interface between the mixer and the baseband low noise amplifier. This

interface provides a high-pass filtering response to notch out the DC offset generated by the self-jamming signal

from the transmitter.

An example schematic is shown in Figure 4-6. The R2000 reference design has higher order external DRM filters.

The design of the baseband interface meets the following requirements:



The high-pass filtering corner must be low enough to prevent attenuating the received signal. Although the

tag response modulation does not consist of any DC content, the low data rate modes can have significant

signal content very close to DC.



The high-pass filtering corner must be high enough so that the DC changes can converge quickly. There is

a change of DC content going from modulated data transmission (interrogator transmit) to continuous wave

(CW) transmission (interrogator receive). The DC changes must converge before the receive demodulator

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