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BPSK Tx

Play Stop PSK31 is created by switching the polarity of the signal used to key the computer's sound card. In the most-commonly-used variant (BPSK31), binary information is transmitted by either imparting a 180-degree polarity shift (a binary 'zero') or no polarity shift (a binary 'one') in each 32ms symbol interval. As shown in the figure above, a "raised cosine" filter is used to limit the occupied bandwidth, resulting in both amplitude and phase modulation of the carrier. The 180 degree phase shift for a "zero" bit code occurs during at an amplitude null. The maximum baud rate for a passband for common modulation methods such as QAM, PSK and OFDM is approximately equal to the passband bandwidth. A V.22bis modem transmits 2400 bit/s using 1200 Bd (1200 symbol/s), where each quadrature amplitude modulation symbol carries two bits of information. The modem can generate M=22=4 different symbols. It requires a bandwidth of 1200 Hz (equal to the baud rate). The carrier frequency (the central frequency of the generated spectrum) is 1800 Hz, meaning that the lower cut off frequency is 1800 -1200/2 = 1200 Hz, and the upper cutoff frequency is 1800 + 1200/2 = 2400 Hz.

[ CW Tx | CW Rx ] --- [PSK Tx | PSK Rx ] --- [ DTMF Tx | DTMF Rx ]