An analog (7,5) convolutional decoder in 65 nm CMOS for low power wireless applications

A complete architecture with transistor level simulation is presented for a low power analog convolutional decoder in 65 nm CMOS. The decoder core operates in the weak inversion (sub-V_τ) and realizes the BCJR decoding algorithm corresponding to the 4-state tail-biting trellis of a (7,5) convolutional code. The complete decoder also incorporates serial I/O digital interfaces and current mode differential DACs. The simulated bit error rate is presented to illustrate the coding gain compared to an uncoded system. Our results show that a low power, high throughput convolutional decoder up to 1.25 Mb/s can be implemented using analog circuitry with a total power consumption of 84 μW. For low rate applications the decoder consumes only 47 μW at a throughput of 250 kb/s.