Timing frequency recovery

Claim 3

A method as defined in claim 1 wherein said step of determining is carried out to provide the maximum and minimum of the sum of the squares of the two demodulation products as the adjustment criterion.

Claim 4

A method as defined in claim 2 wherein said step of determining comprises ascertaining that the maximum of the sum of the squares of the two demodulation products exceeds a predetermined value or that the minimum of the sum of the squares of the two demodulation products lies below a predetermined value to provide an additional adjustment criterion.

Claim 5

A method as defined in claim 3 where said step of determining comprises comparing a signal representing the sum with the same signal delayed in time to provide the maximum and minimum of the sum.

Claim 6

A method as defined in claim 4 wherein said step of forming the sum comprises scanning the two demodulation products in rapid alternation and forming the squares of the two products by time division multiplexing.

Claim 7

A method as defined in claim 1 further comprising, before said step of forming, converting each demodulation product from analog to digital form.

Claim 8

A method as defined in claim 6 wherein said step of forming comprises preliminarily storing a representation of the square of each demodulation product value in a memory.

Claim 9

Apparatus for recovering the timing frequency in a modulated data signal receiver containing a timing frequency generator, a demodulator for demodulating a received signal with the aid of carriers which are shifted by 90° in phase relative to one another to form two demodulation products, and a converter connected to receive successive values of the two demodulation products in alternation and generating a digital representation of each successively received value, said apparatus comprising: a read-only memory containing a representation of the square of each demodulation product and connected to receive the digital representations of the successive demodulation product values; a first time delay member having its input connected to the output of said memory; a summing member having a first input connected to the output of said memory and a second input connected to the output of said first delay member; a second time delay member having its input connected to the output of said summing member; a comparator having a first input connected to the output of said summing member and a second input connected to the output of said second delay member; a differentiating member having its input connected to the output of said comparator; a threshold value switch having its input connected to the output of said summing member; an AND-circuit having a first input connected to the output of said differentiating member and a second input connected to the output of said threshold value switch; an oscillator; and means defining a control path having a first input connected to the output of said AND-circuit and a second input connected to said oscillator, with the output of said control path providing the timing frequency for the receiver.

Claim 10

Apparatus for recovering the timing frequency in a modulated data signal receiver containing a timing frequency generator, a demodulator for demodulating a received signal with the aid of carriers which are shifted by 90° in phase relative to one another to form two demodulation products, and a converter connected to receive successive values of the two demodulation products in alternation and generating a digital representation of each successively received value, said apparatus comprising: a read-only memory containing a representation of the square of each demodulation product and connected to receive the digital representations of the successive demodulation product values; a first time delay member having its input connected to the output of said memory; a summing member having a first input connected to the output of said memory and a second input connected to the output of said first delay member; a second time delay member having its input connected to the output of said summing member; a comparator having a first input connected to the output of said summing member and a second input connected to the output of said second delay member; a differentiating member having its input connected to the output of said comparator; a threshold value switch having its input connected to the output of said summing member; an AND-circuit having a first input connected to the output of said differentiating member and a second input connected to the output of said threshold value switch; an oscillator; and means defining a control path having a first input connected to the output of said AND-circuit and a second input connected to said oscillator, with the output of said control path providing the timing frequency for the receiver.

Claim 11

Apparatus for recovering the timing frequency in a modulated data signal receiver containing a timing frequency generator and a demodulator for demodulating a received signal with the aid of carriers which are shifted by 90° in phase relative to one another to form two demodulation products, said apparatus comprising: first and second multipliers each having both of its inputs connected together to receive a respective one of the demodulation products in order to provide an output representing the square of the demodulation product which it receives; summing means having inputs connected to the outputs of said multipliers; a first differentiator having its input connected to the output of said summing means; a limiter having its input connected to the output of said first differentiator; a second differentiator having its input connected to the output of said limiter; a threshold value switch having its input connected to the output of said summing means; an AND-circuit having a dynamic input connected to the output of said second differentiator and a static input connected to the output of said threshold value switch; a quartz oscillator; and means defining a control path having one input connected to the output of said AND-circuit and another input connected to said oscillator and having an output providing the timing frequency for the receiver.

Claim 12

Apparatus for recovering the timing frequency in a modulated data signal receiver containing a timing frequency generator and a demodulator for demodulating a received signal with the aid of carriers which are shifted by 90° in phase relative to one another to form two demodulation products, said apparatus comprising: first and second multipliers each having both of its inputs connected together to receive a respective one of the demodulation products in order to provide an output representing the square of the demodulation product which it receives; summing means having inputs connected to the outputs of said multipliers; a first differentiator having its input connected to the output of said summing means; a limiter having its input connected to the output of said first differentiator; a second differentiator having its input connected to the output of said limiter; a threshold value switch having its input connected to the output of said summing means; an AND-circuit having a dynamic input connected to the output of said second differentiator and a static input connected to the output of said threshold value switch; a quartz oscillator; and means defining a control path having one input connected to the output of said AND-circuit and another input connected to said oscillator and having an output providing the timing frequency for the receiver.

Claim 13

Apparatus for recovering the timing frequency in a modulated data signal receiver containing a timing frequency generator and a demodulator for demodulating a received signal with the aid of carriers which are shifted by 90° in phase relative to one another to form two demodulation products, said apparatus comprising: time multiplexing means connected to sample the two demodulation products alternatingly and successively at a given rate; a multiplier having both inputs connected to the output of said multiplexing means to provide an output signal representative of the square of the demodulation product currently being sampled; a first time delay member having its input connected to the output of said multiplier; a summing member having a first input connected to the output of said first delay member and a second input connected to the output of said multiplier; a second time delay member having its input connected to the output of said summing member; a subtraction member having one input connected to the output of said second delay member and its other input connected to the output of said summing member; a limiter having its input connected to the output of said subtraction member; a differentiator having its input connected to the output of said limiter; a threshold value switch having its input connected to the output of said summing member; an AND-circuit having a dynamic input connected to the output of said differentiator and a static input connected to the output of said threshold value switch; an oscillator; and means defining a control path having one input connected to the output of said AND-circuit and another input connected to said oscillator and having an output providing the timing frequency for the receiver.

Claim 14

Apparatus for recovering the timing frequency in a modulated data signal receiver containing a timing frequency generator and a demodulator for demodulating a received signal with the aid of carriers which are shifted by 90° in phase relative to one another to form two demodulation products, said apparatus comprising: time multiplexing means connected to sample the two demodulation products alternatingly and successively at a given rate; a multiplier having both inputs connected to the output of said multiplexing means to provide an output signal representative of the square of the demodulation product currently being sampled; a first time delay member having its input connected to the output of said multiplier; a summing member having a first input connected to the output of said first delay member and a second input connected to the output of said multiplier; a second time delay member having its input connected to the output of said summing member; a subtraction member having one input connected to the output of said second delay member and its other input connected to the output of said summing member; a limiter having its input connected to the output of said subtraction member; a differentiator having its input connected to the output of said limiter; a threshold value switch having its input connected to the output of said summing member; an AND-circuit having a dynamic input connected to the output of said differentiator and a static input connected to the output of said threshold value switch; an oscillator; and means defining a control path having one input connected to the output of said AND-circuit and another input connected to said oscillator and having an output providing the timing frequency for the receiver.