Demodulator Category Block Listing

The following blocks are included in the Demodulator category :

• Differential PSK Detector
• FM Demodulator
• IQ Detector
• PPM Demodulator
• PSK Detector
• QAM/PAM Detector

Differential PSK Detector

This block implements a differential phase shift keying (DPSK) detector, which maps baseband DPSK constellation values in IQ space into symbol values.

Whever the input clock is high, this block reads in a complex value representing a point in the (I, Q) plane, and determines the phase change since the previous detection. It then converts the observed phase change to a symbol number according to the specified phase transition map file.

Supported DPSK modes include DBPSK, DQPSK, Pi/4-DQPSK, D8PSK, D16PSK and D32PSK.

FM Demodulator

This block demodulates a Frequency Modulated (FM) signal. The block operates by estimating the derivative of the input signal. The FM Demodulator assumes a baseband complex input, but will also work at an IF frequency. For IF operation, a bias is introduced in the output, but this can be compensated using the Offset parameter.

IQ Detector

This block is used to map an arbitrary baseband IQ constellation point back to a symbol value. This block typically follows an Integrate & Dump block. It takes as input a complex value — representing a point in the (I, Q) plane — and determines the closest constellation point per a user provided look-up table. It thyen outputs the corresponding symbol number.

The IQ Detector block operates by measuring the Euclidian distance between the received point and all constellation points, and then selecting the closest point. The simulation speed of the block is inversely proportional to the constellation size.

PPM Demodulator

This block demodulates a pulse position modulated (PPM) signal. The PPM Demodulator block accepts a baseband real signal as input and outputs a symbol number. The block’s parameter values should match the associated PPM modulator block where applicable.

PSK Detector

This block is used to map a baseband PSK constellation point back to its corresponding symbol number.

Th PSK Detector block accepts a complex value representing a point in the (I, Q) plane, and determines the closest PSK constellation point whenever the input clock is high. It then outputs the corresponding symbol number from the specified PSK constellation map file. Its input is typically the output of an Integrate & Dump block or of a filter matched to the symbol rate.

QAM/PAM Detector

This block is used to map a baseband QAM or PAM constellation point back to its corresponding symbol number.

The QAM/PAM Detector block accepts a complex value, representing a point in the (I, Q) plane, and determines the closest QAM or PAM constellation point whenever the input clock is high. It then outputs the corresponding symbol number from the specified QAM/PAM constellation map file. Its input is typically the output of an Integrate & Dump block or of a filter matched to the symbol rate.