TDMA/PSK Carrier synchronization without preamble

A process for providing coherent detection of a series of data bursts, each burst of said series having a single carrier and a plurality of symbols received at a symbol rate, said process comprising:

• applying said data bursts to a pair of demodulators;
• applying a frequency controlled local oscillator signal to said pair of demodulators to thereby provide a pair of quadrature signals at baseband;
• sampling said pair of quadrature signals at said symbol rate, and applying said sampled pair of quadrature signals to a phase estimator;
• estimating the phase difference between said signal carrier and said local oscillator signal in said phase estimator, said phase estimator inherently delaying said estimation of phase difference, and
• delaying said sampled pair of quadrature signals by a delay approximately equal to said inherent delay of said quadrature phase estimator, and providing a delayed quadrature output to a phase corrector;
• correcting the delayed quadrature output in accordance with said estimation of phase difference to thereby provide coherent detection of said data bursts.

An apparatus for automatically frequency tracking the carrier frequency .omega..sub.c of an M-state PSK signal represented by two baseband signals in phase quadrature and defined as:

• ##EQU42## where A is signal amplitude, of .theta..sub.c is an arbitrary phase and .zeta. is a phase modulation defined as:
• ##EQU43## where M=2.sup.k, K is an integer, and a.sub.k independently takes values .+-.1, said apparatus comprising:
• Mth power means for receiving and raising samples of said pair of baseband signals to the Mth power to provide first and second Mth power signals;
• first and second delay means for receiving said first and second Mth-power signals, respectively, for providing first and second delayed Mth power signals;
• first multiplying means for multiplying said first Mth power signal with said second delayed Mth power signal;
• second multiplying means for multiplying said second Mth power signal with said first delayed Mth power signal;
• subtractor means receiving and providing the difference between the outputs of said first and second multiplying means;
• averaging means for averaging said difference for providing an average difference signal;
• and
• filter means receiving said average difference signal for providing a signal to a variable frequency oscillator means.

In an apparatus for providing coherent detection of a series of data bursts, each burst of said series having a modulation imparted thereon to provide a plurality of symbols, said series of bursts having a first repetition rate, said plurality of symbols having a second repetition rate, means for providing a symbol synchronization signal at said second repetition rate comprising:

• means for providing a pair of baseband quadrature signals representing said data bursts;
• means for producing a sum of squares of said baseband signals;
• means for applying the sum of the squares of said baseband signals to a tuned filter to provide a tuned signal from said tuned filter;
• means for gating said tuned signal at said first repetition rate to provide a gated signal;
• phase-locked-loop means receiving said gated signal for providing a phase-locked signal;
• and zero crossing detecting means receiving said phase-locked signal for providing said symbol synchronization signal at said second repetition rate.