Low SNR Enhancement (Digital Demod)

Default: cleared

The Low SNR Enhancement checkbox enables additional filtering of the frequency and phase estimates during the synchronization part of demod. This filtering allows the demodulator to lock in the presence of more noise but causes the frequency lock range to get smaller. To compensate for the smaller frequency lock range, the frequency estimate is tracked from measurement to measurement. An exponential average is used and the output of this average becomes the starting point for the next frequency estimate for the next measurment.

This feature applies to the following demod formats:

BPSK Binary phase shift keying - A type of phase modulation using 2 distinct carrier phases to signal ones and zeros.	16 QAM Quadrature Amplitude Modulation	DVB QAM 16	16 APSK	DVB APSK 16	EDGE Enhanced Data for Global Evolution: A technology that gives GSMA and TDMA similar capacity to handle services for the third generation of mobile telephony. EDGE was developed to enable the transmission of large amounts of data at a high speed, 384 kilobits per second. (It increases available time slots and data rates over existing wireless networks.)
DQPSK Differential Quadrature Phase Shift Keying: QPSK modulation using differential encoding of the digital information stream.	32 QAM	DVB QAM 32	32 APSK	DVB APSK 32
QPSK Quadrature phase shift keying	64 QAM	DVB QAM 64
Offset QPSK	128 QAM	DVB QAM 128
8 PSK Phase Shift Keying: A broad classification of modulation techniques where the information to be transmitted is contained in the phase of the carrier wave.	256 QAM	DVB QAM 256
	512 QAM
	1024 QAM
	2048 QAM
	4096 QAM

If a demod format that Low SNR Enhancement does not apply to is selected, the feature is grayed.

For the Offset QPSK digital demodulation format, if Low SNR Signal-to-Noise Ratio Enhancement is enabled, the maximum Result Length value is about 40000 symbols, otherwise it is 2048. In both cases this maximum may be limited by "Search Time" or by hardware capabilities.