downconvert_process

Down-conversion to baseband.

Calling sequence

[dn,y] = downconvert_process(dn,x)

Parameters

x:: input signal (real or complex)
dn:: downconversion object (created with downconvert_init)
y:: output baseband signal (complex)

Description

If the input signal is complex, no image filtering is down. If the input signal is real, image is removed with a low-pass filter with cut-off frequency set to if , and otherwise, where is the normalized intermediate frequency (in either case, half-way between baseband signal and image signal).

Example 1: downconversion of a BPSK complex signal (without image filtering)

// Load RF test signal (BPSK, I/Q)
[x,fs,fi,fsymb] = sct_test_signal('c');
;
// Down-conversion to baseband
dn = downconvert_init(fi/fs,'c');
[dn,y] = downconvert_process(dn,x);

Scatter plot view:

Frequency view:

Example 2: downconversion of a BPSK real signal (with image filtering)

// Load RF test signal (BPSK, I/Q)
[x,fs,fi,fsymb] = sct_test_signal();
;
// Down-conversion to baseband
dn = downconvert_init(fi/fs,'r');
[dn,y] = downconvert_process(dn,x);