R2000 datasheet(18/75 Pages) ETC

18 / 75 page

Indy® R2000 Electrical, Mechanical, & Thermal Specification

Figure 4-3: Self-Jammer Cancellation Architecture

Indy Reader Chip

0/90

Coupler

Self-Jammer reference

Self-Jammer signal

Ensure that the power level of the reference signal is equal to the largest self-jammer power level that you intend to

cancel. From the real RF reference signal, a new complex reference signal is created using a very low noise,

passive, 90-degree poly-phase filter. The output of the filter consists of four signals: +I, -I, +Q, and

–Q. By adjusting

the I and Q scaling, it is possible to let the cancellation signal achieve the same amplitude as the received self-

jammer, but with a 180 degree phase shift.

In principle, the cancellation signal has the same amplitude and phase noise as the self-jammer. If the time delay

between the reference transmit signal and the received self-jammer is small, it is possible to cancel not only the self-

jammer carrier but also its noise by adding the cancellation signal to the received signal. The RF low noise amplifier

performs this cancellation by adding currents. The noise added by all the blocks in the self-jammer cancellation path

must be smaller than the targeted self-jammer noise after cancellation. For noise minimization purposes, capacitive

coupling scales the reference signal. Switched binary weight capacitors determine the amount of capacitive

coupling. This method has the side effect that the scaling of the reference signal becomes quantized in amplitude.

Figure 4-4 shows the ratio between the output and input for all possible signals. The circular areas illustrate complex

constellation diagrams representing all possible signals relative to the full scale reference signal. The color shows

the theoretical output after self-jammer cancellation relative to full scale for all possible self-jammer signals. When

the received self-jammer has a phase and amplitude that matches one of the possible cancellation signals, the

suppression is very good (shown in blue). When the received self-jammer falls between possible cancellation

signals, the suppression is not as good (shown in red). With two bits per axis (i.e., four levels per axis ranging from

zero to full scale), the worst case suppression is almost 13 dB. With four bits per axis, the worst case suppression is

theoretically more than 26 dB. Indy R2000 implements four bits per axis, because with 26 dB suppression, other

factors will start to dominate the actual noise suppression.

R2000 Datasheet(PDF) 18 Page - List of Unclassifed Manufacturers