JPH0422376B2 - - 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.

[Conventional technology]

In the slotted Aloha system, which is one of the time division multiple access systems, time slots of fixed duration 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.

This conventional carrier wave regeneration method uses a phase comparator and
A phase-locked loop consisting of a low-frequency wave generator and a voltage-controlled oscillator (hereinafter abbreviated as VCO) was used to regenerate the reference carrier wave by phase-locking the VCO to the carrier wave component of the burst. Since there is no phase comparator output in time slots where no burst is input, the VCO
becomes a free-running oscillation state. Since the frequency stability of a VCO in its free-running oscillation state is generally not very good, the oscillation frequency of the VCO fluctuates greatly during this period.
When a burst is input next, the difference between the carrier wave component frequency and the VCO oscillation frequency, that is, the initial frequency offset, becomes a large value.

[Problem that the invention seeks to solve]

As explained above, the conventional carrier wave regeneration method is
In the time slot where no burst is input, the VCO enters a free-running oscillation state and the initial frequency offset becomes large.The pull-in time of the phase-locked loop is determined by the initial frequency offset, so there is a drawback that the pull-in time is long. The drawback is that the operation itself becomes unstable.

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

[Means for solving problems]

The carrier wave regeneration method of the present invention is a carrier wave regeneration method in which each reference carrier wave is regenerated from a burst carrier wave input to an arbitrary time slot in a time series of time slots having a predetermined time length set in advance. a phase comparison means for comparing the phase with the reference carrier wave and outputting an error signal; an addition means for adding an average value signal to the error signal and outputting the result; and each time the burst carrier wave is input, adding the previous output and the above. comprising averaging means for calculating an average value with a signal newly output by the means and outputting the average value signal, and oscillation means for controlling an oscillation frequency by the output of the adding means and outputting the reference carrier wave. It consists of

〔Example〕

The present invention will be described in detail below with reference to drawings showing embodiments.

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

The embodiment shown in FIG.
01 and a reference carrier signal 104 and outputs the comparison result, a low frequency converter 2 that outputs the low frequency component of the output of the phase comparator 1 as an error signal 102, and a VCO control signal 108. An averaging circuit 3 inputting a reset signal 107 and outputting an average value signal 103, an error signal 102 and an average value signal 1
03, a VCO 5 that uses the output of the adder 4 as a control input and oscillates and outputs the reference carrier signal 104, and an AND that gates the slot timing signal 105 with the burst detection signal 106 and outputs it as a reset signal 107. The gate 6 is configured to include a gate 6.

The averaging circuit 3 converts the VCO control signal 108 into A-
A-D converter 31 for D conversion and reset signal 1
A register 32 that stores and holds the output of the A-D converter 31 when 07 is input, and a coefficient signal 301 whose value is 0.5 in the contents of the register 32 and register 36.
A multiplier 33 and a multiplier 34 that multiply and output the result,
An adder 35 that adds the output of the multiplier 33 and the output of the multiplier 34, and a register 36 that stores and holds the output of the adder 35 when the reset signal 107 is input.
Then, the output of the adder 35 is D-A converted and the average value signal 1 is obtained.
03.

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

The burst carrier wave signal 101 is a burst-shaped carrier wave component extracted from an input burst using a known carrier wave extraction method such as the Costas loop method. In the time slot where the burst is input, the burst carrier signal 101 and the VCO 5 output (reference carrier signal 104) are compared in phase by the phase comparator 1, and the comparison result is sent to the error signal 102 via the low frequency converter 2. becomes.

The burst detection signal 106 is a signal generated when an input burst is reliably received and a unique word of the burst is detected. The slot timing signal 105 is a constant cycle signal representing slot timing, and is gated by the burst detection signal 106 in the AND gate 6. AND gate 6 therefore outputs a reset signal 107 each time a burst is reliably received.

Here, the operation of the averaging circuit 3 will be explained first.

At the time when a new burst is input, the register 32 holds the VCO control signal 108 corresponding to the most recently input burst via the AD converter 31. This value
Let it be V _o-1 . Also, assume that the value held by the register 36 at this point is _o-1 . When this newly input burst is reliably received, the reset signal 107 is input, and the contents of the register 32 are updated to the control signal 108 at this point (the value V _o converted by the A-D converter 31). be done. The contents of the register 36 are also updated to the value _o at the same time. Multiplier 33・
Due to the operation of the adder 35, _o becomes the arithmetic mean of V _o-1 and _o-1 . Therefore, from this point on until the next burst is reliably received, the output of adder 35 is
This is the average value (averaged with greater weight given to the more recent bursts) of the control signals 108 (values converted by the AD converter 31) corresponding to each burst received in the past. Adder 35 output is D
-Average value signal 1 after being D-A converted by A converter 37
It becomes 03.

Now, the oscillation frequency of VCO5 is the error signal 102
and the average value signal 103. In the time slot where the burst is input,
Since the VCO 5 is controlled by this sum and is phase-locked to the burst carrier signal 101, the frequency of the reference carrier signal 104 is the same as that of the burst carrier signal 101.
matches the frequency of Since the burst carrier wave signal 101 does not exist in the time slot where no burst is input, and the error signal 102 does not occur,
The control input of the VCO 5 is only the average value signal 103, and the average value signal 103 is the average value of the control signals 108 corresponding to each burst received in the past, so the oscillation frequency of the VCO 5 is the frequency corresponding to the average value signal 103. , that is, the average frequency of the carrier wave components of bursts input in the past.

Next, when a low frequency filter or a phase comparator is used as the low frequency filter 2 or phase comparator 1 such that the error signal 102 becomes unstable when the burst carrier signal 101 is not present, burst arrival prediction is performed. By discharging the voltage of the low frequency generator 2 by the signal 109, the VCO control signal 108 becomes the average value signal 103.
matches. The initial frequency offset at the time when the burst carrier signal 101 is input is the difference between the average frequency of the carrier wave components of past bursts and the frequency of the carrier wave components of the newly input burst, and its value is the carrier wave frequency error of each burst. Less than the maximum value. Since the carrier wave frequency error of each burst is much smaller than the fluctuation of the oscillation frequency when the VCO 5 enters a free-running oscillation state in a time slot where no burst is input, the initial frequency offset of the embodiment shown in Fig. 1 is is very small.

The operation of the embodiment shown in FIG. 1 has been described above.

In the embodiment shown in FIG. 1, the averaging circuit 3 performs signal processing digitally, but it is of course possible to construct an averaging circuit that performs analog processing in a similar manner. D converter 3
1.The DA converter 37 is not required.

〔Effect of the invention〕

As explained in detail above, the carrier wave regeneration method of the present invention is a means of reducing the initial frequency offset by keeping the frequency of the oscillation means at the average value of the carrier wave frequencies of past bursts in time slots where no burst is input. Since we use
Use of the present invention has the effect of providing a carrier wave regeneration system with fast and stable regeneration operation.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the carrier wave regeneration system of the present invention. 1... Phase comparator, 2... Low frequency device, 3...
Averaging circuit, 4...adder, 5...VCO, 6...
…AND gate.

Claims (1)

[Scope of Claims] 1. A carrier wave regeneration method in which each reference carrier wave is regenerated from a burst carrier wave input to an arbitrary time slot in a time series of time slots having a predetermined time length, comprising: A phase comparison means that compares the phase with a reference carrier wave and outputs an error signal, an addition means that adds an average value signal to the error signal and outputs the result, and each time the burst carrier wave is input, the output up to that point and the addition means and an oscillation means for controlling an oscillation frequency based on the output of the adding means and outputting the reference carrier wave. A carrier wave regeneration method featuring: