Indy R1000 Datasheet - Impinj

Indy R1000 ® Electrical, Mechanical, & Thermal Specification
5.1.2 LO Input
The RX LO may be sourced internally or externally as shown in Figure 6. If an external RX LO is not used, the DC blocking capacitors, inductor,
and balun are not required.
5.1.3 Receive RF Interface
Figure 6: LO Input External Interfaces
The Indy R1000 reader chip has differential RF and LO ports to alleviate interference on the package bond-wires coming from the digital section of
the chip.
The Indy R1000 RX Mixer also supports a high gain and a low gain mode with differing compression points. In order to switch between these
modes, it is necessary to both correctly program the ANA_CTRL1 register as well as bias the output of the mixer to +3.3v through 400 ohm
resistors. These resistors may be switched in for low gain mode and out for high gain mode. Ensure that when switched out, these bias resistors do
not create an unintended current summing node.
5.1.4 Receive Baseband Interface
An AC coupling interface is used in the Indy R1000 reader chip 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.
The design of the baseband interface meets the following requirements:
• The high-pass filtering corner must be low enough to not attenuate the received signal. Although the tag response modulation does not consist
of any DC content, the low data rate modes can have significant signal contents very close to DC
• The high-pass filtering corner must be high enough so that the DC changes can converge quickly enough. There is a change of DC content
going from modulated data transmission (interrogator transmit) to continuous wave (CW) transmission (interrogator receive.) The DC changes
need to converge before the receive demodulator can demodulate correctly. The DC level change occurs during transition from transmit to
receive. Varying the time constant of the high-pass filtering or sampling and holding the DC offset is allowed, provided the air interface
protocol is not violated.
• The AC coupling capacitor and the bias resistance must form a low-pass filter for the bias thermal noise, provided the total integrated noise is a
constant equal to KT/C. To reduce the input referred noise of the baseband low noise amplifier, either make the corner frequency high to lower
the in-channel spectral noise density, or make the corner frequency lower than the high-pass filtering in the baseband filter chain.
16 Revision 2.3, Copyright © 2012, Impinj, Inc.