Synchronization and Receiver Design

Carrier frequency and phase recovery, timing frequency and phase recovery, AGC, I/Q imbalance compensation, phase-locked loops

Communications Toolbox™ includes tools using either MATLAB^® or Simulink^® for signal recovery.

Functions

`iqcoef2imbal`	Convert compensator coefficient to amplitude and phase imbalance
`iqimbal2coef`	Convert I/Q imbalance to compensator coefficient
`channelDelay`	Channel timing delay

Objects

`comm.AGC`	Adaptively adjust gain for constant signal-level output
`comm.CarrierSynchronizer`	Compensate for carrier frequency offset
`comm.SymbolSynchronizer`	Correct symbol timing clock skew
`comm.PreambleDetector`	Detect preamble in data
`comm.CoarseFrequencyCompensator`	Compensate for frequency offset for PAM, PSK, or QAM
`comm.IQImbalanceCompensator`	Compensate for I/Q imbalance
`comm.DiscreteTimeVCO`	Generate variable frequency sinusoid
`comm.GMSKTimingSynchronizer`	Recover symbol timing phase using fourth-order nonlinearity method
`comm.MSKTimingSynchronizer`	Recover symbol timing phase using fourth-order nonlinearity method

Blocks

AGC	Adaptively adjust gain for constant signal-level output
Carrier Synchronizer	Compensate for carrier frequency offset
Symbol Synchronizer	Correct symbol timing clock skew
Preamble Detector	Detect preamble in data packet
Coarse Frequency Compensator	Compensate for carrier frequency offset for PAM, PSK, or QAM
I/Q Compensator Coefficient to Imbalance	Convert compensator coefficient into amplitude and phase imbalance
I/Q Imbalance Compensator	Compensate for imbalance between in-phase and quadrature components
I/Q Imbalance to Compensator Coefficient	Converts amplitude and phase imbalance into I/Q compensator coefficient
Discrete-Time VCO	Implement voltage-controlled oscillator in discrete time
MSK-Type Signal Timing Recovery	Recover symbol timing phase using fourth-order nonlinearity method
Baseband PLL	Implement baseband phase-locked loop
Charge Pump PLL	Implement charge pump phase-locked loop using digital phase detector
Continuous-Time VCO	Implement voltage-controlled oscillator
Linearized Baseband PLL	Implement linearized version of baseband phase-locked loop
Phase-Locked Loop	Implement phase-locked loop to recover phase of input signal

Topics

Synchronization Fundamentals

Phase-Locked Loops

Phase recovery methods and phase-locked loops.

MATLAB

Correct Phase and Frequency Offset for 16-QAM Using Coarse and Fine Synchronization

Compensation of significant phase and frequency offsets for a 16-QAM signal in an AWGN channel is accomplished in two steps.

Compensate for Frequency Offset Using Coarse and Fine Compensation

Correct for a phase and frequency offset in a noisy QAM signal using a carrier synchronizer.

Correct Symbol Timing and Doppler Offsets

Correct symbol timing and frequency offset errors by using the comm.SymbolSynchronizer and comm.CarrierSynchronizer System objects.

Adjust Carrier Synchronizer Damping Factor to Correct Frequency Offset

Attempt to correct for a frequency offset using the carrier synchronizer object.

MSK Signal Recovery

Model channel impairments such as timing phase offset, carrier frequency offset, and carrier phase offset for a minimum shift keying (MSK) signal.

Simulink

MSK Signal Recovery

This model shows how channel impairments such as timing phase offset, carrier frequency offset, and phase offset for a minimum shift keying (MSK) signal are modeled.

Featured Examples

QPSK Transmitter and Receiver

The implementation of a QPSK transmitter and receiver. The receiver addresses practical issues in wireless communications, e.g. carrier frequency and phase offset, timing drift and frame synchronization. The receiver demodulates the received symbols and outputs a simple message (e.g., to the Diagnostic Viewer).

Open Model

QPSK Transmitter and Receiver

A digital communications system using QPSK modulation. In particular, this example illustrates methods to address real-world wireless communications issues like carrier frequency and phase offset, timing recovery and frame synchronization.

Open Script

RF Satellite Link

A satellite link, using the blocks from the Communications Toolbox™ to simulate the following impairments: Memoryless nonlinearity

Open Script

Top-Down Design of an RF Receiver

Designs an RF receiver for a ZigBee®-like application using a top-down methodology. It verifies the BER of an impairment-free design, then analyzes BER performance after the addition of impairment models. The example uses the RF Budget Analyzer App to rank the elements contributing to the noise and nonlinearity budget.

Open Script

OFDM Synchronization

A method for digital communication with OFDM synchronization based upon the IEEE® 802.11a™ standard. System objects™ from the Communications Toolbox are utilized to provide OFDM modulation and demodulation and help synchronization functionality. In particular, this example illustrates methods to address real-world wireless communication issues like carrier frequency recovery, timing recovery, and frequency domain equalization.

Open Script

DVB-S.2 Link, Including LDPC Coding

The state-of-the-art channel coding scheme used in the second generation Digital Video Broadcasting standard (DVB-S.2), which is deployed by DIRECTV in the United States. The coding scheme is based on concatenation of LDPC (Low-Density Parity-Check) and BCH codes. LDPC codes, invented by Gallager in his seminal doctoral thesis in 1960, can achieve extremely low error rates near channel capacity by using a low-complexity iterative decoding algorithm. The outer BCH codes are used to correct sporadic errors made by the LDPC decoder.

Open Model

Architectural Design of a Low IF Receiver System

Use the RF Blockset™ Circuit Envelope library to simulate the performance of a Low IF architecture with the following RF impairments: Component noise

Open Script

Parallel Concatenated Convolutional Coding: Turbo Codes

The basic structure of turbo codes, both at the transmitter and receiver ends, and characterizes their performance over a noisy channel using components from the Communications Toolbox™. We chose the Long Term Evolution (LTE) specifications [ 4 ] for the constituent component parameters.

Open Model

RF Noise Modeling

Use the RF Blockset™ Circuit Envelope library to simulate noise and calculate noise power. Results are compared against theoretical calculations and a Communications Toolbox™ reference model.

Open Script

Impact of Thermal Noise on Communication System Performance

Use the RF Blockset Circuit Envelope library to model the thermal noise of a super-heterodyne RF receiver and measure its effects on the bit error rate (BER) of a communications system. The RF receiver model does not include impedance mismatches or nonlinearities. A Communications Toolbox reference model with parameters computed using Friis equations is used to verify the results.

Open Model

CORDIC-Based QPSK Carrier Synchronization

The use of a CORDIC (COordinate Rotation DIgital Computer) rotation algorithm in a digital PLL (Phase Locked Loop) implementation for QPSK carrier synchronization. Fixed-Point Designer™ is needed to run this model.

Open Script

Defense Communications: US MIL-STD-188-110A Receiver

A communications system compliant with the U. S. MIL-STD-188-110A military standard. In particular, the model implements a full receiver that demodulates and outputs a text message, which was modulated by a reference transmitter and captured with data acquisition equipment. This model supports a 1200 bps data rate. It also implements an interleaver length of 0.6 s.

Open Model