1 t3 1 1 1 1 2 3 4 -50 -40 -30 -20 -10 0.6 -200 -180 -160 -140 -120 -100 -80 BP-SDM NTF 0.8 1 1.2 Frequency (GHz) Channel 1 Channel 2 Channel 3 Channel 4 100 200 300 400 Time Samples 500 (a) RF Filter TF Channel 1 Channel 2 Channel 3 Channel 4 600 700 800 900 1,000 t1 100 200 300 400 500 600 700 t6 800 900 1,000 100 100 t2 200 300 400 500 200 300 400 100 200 300 400 t4 500 t5 600 700 800 900 1,000 600 700 800 500 600 700 800 t7 900 1,000 900 t8 1,000 1.4 1.6 0.6 0.8 1 1.2 Frequency (GHz) (b) Figure 23. Illustration of the operation of the LSTM-based AI engine in CR receivers. (a) Evolution of channel occupancy and band selection provided by the decision block [61]. (b) Effect on tuning of the RF filter Transfer Function (TF) and noise-shaping of the BP CT-RDM. FIRST QUARTER 2022 IEEE CIRCUITS AND SYSTEMS MAGAZINE 33 1.4 1.6 Power/Frequency (dB/Hz) Magnitude (dB) No. Ch. Oc4 Oc3 Oc2 Oc1