Citation
Abstract
The subcarrier demodulation digital loop is part of the Baseband Assembly. The subcarrier demodulator is a fourth-order Costas-type loop. It corresponds to a “type 2” analog loop in terms of steady state response. In this article, the expected value and the variance of the error signal are determined as functions of the input SNR. A Nyquist sampling rate of the input signal is assumed. From the integro-difference equations a mixed s/z domain block diagram is obtained. From the loop’s transfer function a set of gains for the loop filter is obtained. Also, a set of state equations is presented for future reference. Finally, the noise-equivalent bandwidths are calculated for normalized computation times of 0, 0.25 and 0.5. The subcarrier demodulator analyzed in this article tracks a parabolic phase input with finite steady state error. Since at each update instant the loup gains are adjusted to compensate for the variations in SNR of the input signal, the noise-equivalent bandwidth is maintained constant.
Details
- Volume
- 42-80
- Published
- February 15, 1985
- Pages
- 180–194
- File Size
- 380.4 KB