JPH0422377B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a carrier wave regeneration system, and particularly to a carrier wave regeneration system used in a slotted Aloha system.

(Prior art) In the slotted Aloha method, which is one of the time division multiple access (TDMA) methods, time slots of a certain length are set in advance, and each station transmits in bursts within the time slots when necessary. . A burst demodulator that receives this must reproduce a reference carrier wave of a frequency synchronized with the carrier wave component for each input burst.

Such conventional carrier wave recovery methods include a phase comparator,
A phase-locked loop consisting of a low-frequency wave generator and a voltage-controlled oscillator (hereinafter abbreviated as VCO) was used to phase-lock the VCO to the carrier wave component of the burst and regenerate the reference carrier wave.

Since there is no phase comparator output in time slots where no burst is input, the VCO enters a free-running oscillation state. Since the VOC oscillation frequency in the free-running oscillation state of the VCO and the frequency of the burst signal are independent, the initial frequency offset becomes large.

(Problems to be solved by the invention) As explained above, in the conventional carrier wave regeneration method,
Since the VCO enters a free-running oscillation state in time slots where no burst is input, and the initial frequency offset is large, the pull-in time of the phase-locked loop is long, and the operation of the phase-locked loop itself is unstable.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a carrier wave regeneration method in which the regeneration operation is fast and stable.

(Means for Solving the Problems) The present invention provides means for solving the above-mentioned problems, in which each reference carrier wave is extracted from burst carrier waves transmitted based on the slotted Aloha method on the transmitting side. In a carrier wave regeneration method using a phase-locked loop, an oscillation means whose oscillation frequency is limited by a control signal, a phase comparison means which compares the phase of the output of the oscillation means with the burst carrier wave and outputs an error signal, and each of the above-mentioned means for determining the maximum and minimum values of the control signal from the beginning of the burst carrier to the present; and averaging for averaging the maximum and minimum values to obtain and store the average value of the control signal; and an addition means for outputting the added value of the error signal and the average value as the control signal, the oscillation means, the phase comparison means, and the addition means forming the phase locked loop, The present invention is characterized in that when the output of the oscillation means is synchronized with the phase of the burst carrier wave, the output of the oscillation means becomes the reference carrier wave.

(Example) The present invention will be described in detail below with reference to drawings showing examples.

FIG. 1 is a block diagram showing an embodiment of the carrier wave regeneration system of the present invention.

The embodiment shown in FIG.
A phase comparator 1 that compares the phases of 01 and VCO output signal 104 and outputs the comparison result;
A low frequency converter 2 that outputs the low frequency component of the output as an error signal 102, and an A/V converter 2 that converts the VCO control voltage 105 from an analog signal to a digital signal 106.
A D converter 3, a maximum value detector 4 and a minimum value detector 5 which respectively detect the maximum value and minimum value of the incoming burst from the digital signal 106, and an average value from the output signals 107 and 108 of both the previous detectors. An average circuit 6 for calculating the average circuit output signal 109
D/A converter 7 that converts the signal into an analog signal 103
, an adder 8 that adds the error signal 102 and the average signal 103, and a VCO 9.

The operation of the embodiment shown in FIG. 1 will be explained.

A phase comparator 1 compares the phase of the burst carrier signal 101 with the VCO output signal 104 . When a burst is input, the comparison result becomes an error signal 102 via the low frequency converter 2, which controls the VCO 9 via the adder 8, thereby forming a phase-locked loop.

The burst detection signal 110 will now be explained. The burst detection signal 110 is a signal generated when a synchronization word (unique word) normally added to an input burst signal is detected. The timing chart is shown in FIG. The updating operation of the maximum value detector 4 and minimum value detector 5 described below is performed at the falling edge of the burst detection signal 110.

VCO control voltage 105 is converted into a digital signal by A/D converter 3 and input to maximum value detector 4 and minimum value detector 5. Maximum value detector 4
replaces the output with the input signal if the input signal 106 is greater than the output signal 107. However, the above operation is performed only when a burst is detected.

The minimum value detector 5 replaces the input signal with an output signal when the input signal 106 is smaller than the output signal 108. Similar to the maximum value detector, the above operation is performed only when a burst is detected.

Now, the digital signal 106 is the VCO control voltage 1
05, the VCO output frequency can be determined from the modulation sensitivity (Hz/V) of the VCO 9. That is, signal 107 indicates the VCO control voltage 105 for the frequency of the highest frequency burst among the input bursts, and signal 108 indicates the VCO control voltage 105 for the lowest frequency burst.

Therefore, the average value 109 of the signals 107 and 108 obtained by the averaging circuit 6 corresponds to the VCO control voltage 105 corresponding to the average frequency of the highest frequency and the lowest frequency of the received burst signal. The average frequency signal 109 is converted into an analog signal by the D/A converter 7 and becomes the average control voltage 103.

Since the control signal 111 resets the maximum value detector 4 and the minimum value detection value 5 in the initial state,
It is also necessary to cope with long-term frequency fluctuations in electrical transmission lines.

For example, if the input burst signal frequency shifts in the higher direction due to fluctuations in the oscillation frequency of the satellite repeater, the minimum value detector is no longer updated. Therefore, it is necessary to initialize the detectors 4 and 5 in long cycles using the control signal 111.

The control signal 112 is a control signal for discharging the low frequency converter 2 immediately before a predetermined burst receiving position so that the frequency of the VCO output signal 104 is always the average of the maximum and minimum frequencies of the burst.

The circuit shown in FIG. 1 is modified to include the A/D conversion circuit 3, the maximum value detection circuit 4, the minimum value detection circuit 5, the averaging circuit 6, and the D/A converter 7.
It is also possible to perform analog processing, and in this case, the A/D converter 3 and the D/A converter 7 are unnecessary.

(Effects of the Invention) As explained in detail above, in the carrier wave regeneration method of the present invention, the VCO frequency is maintained at the average frequency of the highest frequency and the lowest carrier wave frequency of the input burst signal at the time of initial acquisition, so the regeneration operation is performed. is fast and stable.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the carrier wave regeneration method of the present invention, and FIG. 2 is a time chart showing the relationship between a burst detection signal and a received signal. 1... Phase comparator, 2... Low frequency device, 3...
A/D converter, 4... Maximum value detector, 5... Minimum value detector, 6... Average circuit, 7... D/A converter, 8... Adder, 9... VCO.

Claims (1)

[Claims] 1 In a carrier wave regeneration method in which each reference carrier wave is regenerated in a phase-locked loop from a burst carrier wave transmitted based on the slotted Aloha method on the transmitting side, an oscillation means whose oscillation frequency is controlled by a control signal, and an oscillation means of this oscillation means are used. a phase comparison means for comparing the phase of the output and the burst carrier wave and outputting an error signal; means for determining the maximum value and minimum value of the control signal for each burst carrier wave from the beginning of the burst carrier wave to the present time; The control signal includes an averaging means for averaging the maximum value and the minimum value to obtain and store an average value of the control signal, and an adding means for outputting an added value of the error signal and the average value as the control signal, The oscillation means, the phase comparison means, and the addition means form the phase-locked loop, and when the output of the oscillation means is synchronized with the phase of the burst carrier wave, the output of the oscillation means becomes the reference carrier wave. Carrier wave regeneration method.