JPS6025940B2 - Reference carrier wave regenerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reference carrier regeneration circuit that regenerates each reference carrier signal or clock signal from a plurality of time-divisionally inputted burst signals (carrier waves) in multiple access type time division multiplex communication. , especially regarding its synchronous pull-in.

There are frequency division multiplexing systems, time division multiplexing systems, etc. as communication systems for multi-access satellite communication or multidirectional multiplex communication on terrestrial lines, but recently the transmission of digital information has increased, and this is due to mutual interference. Time-division multiplexing is often used for the purpose of efficiently transmitting data without having to do so.

Figure 1 shows a system overview of a multidirectional multiplex terrestrial line using this time division multiplexing method.As shown in Figure 1a, there is one master station P, and multiple It consists of 4 slave stations A, B, C, and D.

Each of these slave stations A to D has time slots T^, TB, Tc, and T, respectively. has been assigned,
Information on each slave station A to D is its own assigned time slot T^
Each can be transmitted to the master station P only within the period of ~To. Each slave station information sent from each slave station A to ○ is the master station P.
As shown in FIG. 1(b), the received signal is input in bursts to the top one of the assigned time slots M of each slave station, and is input in units of frames. By the way, the frequencies fA, fB, fc, f of the transmission carrier waves of each of these slave stations A to ○ are
o and its phases 0^, 08, ac, oo are generally different, and the distance between the master station P and each slave station A to D and the radio wave propagation state between them are also different. The frequencies and phases of the slave station transmission carrier waves vary. Therefore, for example, when information from each slave station A to D is transmitted by phase modulation and demodulated by a synchronous detection method, each reference carrier wave is regenerated from the transmission carrier wave of each slave station,
It is necessary to input it to the demodulation circuit. Fig. 2 shows a conventional reference carrier regeneration circuit used in this type of device. An input terminal that is input at a predetermined frame period F, 2 is this input terminal 1
From the phase modulated waves of each slave station A to D that are burst input into the
A non-modulated carrier wave generation circuit that generates respective non-modulated carrier waves (hereinafter referred to as burst carrier waves) f [f^, fB, fc, fo] by a borrowing method etc. 3 is a non-modulated carrier wave generation circuit that generates these burst carrier waves f [f^, fB ,fc,f.

] and its reference carrier waves [fo^, foB, fpi, foo] to be described later, a phase difference 8-8o is detected, and a phase error voltage V[V^, VB, Vc, V according to the phase difference is detected. ], 4 is a low-pass filter (hereinafter referred to as LPF) that removes the high frequency component of this phase error voltage V, and 5 is the output voltage of this LPF 4, that is, the VCO control voltage V[V
^, VB, Vc, Vo] is a voltage controlled oscillator (hereinafter referred to as VCO) that controls its oscillation frequency phase according to
foc, rao] are input to the phase detector 3 for comparison and output to the output terminal 6. Here, the phase detector 3,
LPF4 and VC05 constitute a phase locked loop (PLL), and are controlled so that the oscillation output of VC05 follows or synchronizes with each input burst carrier wave f.

That is, the fluctuations in each burst carrier f and control voltage V with respect to the free-running oscillation state of VC05 are expressed as Δf and A, respectively.
If V, then △V- Kd FS Af-S+Kd Ko FS Where, Kd: Detection sensitivity of phase detector 3 (V/rad)
Ko: VC05 modulation sensitivity (rad/sec/V) FS
: Becomes the time constant of LPF4.

Note that when the PLL is in a synchronous state, S=0, so △V/
Δf=1/K, and ΔV proportional to Δf is output from the LPF4. Next, the operation of this conventional circuit is shown in Figure 3a-
This will be explained using the operation waveform diagram of e.

The phase modulated waves of each of the slave stations A to D inputted to the input terminal 1' are non-modulated by the non-modulated carrier generating circuit 2 and output as a burst carrier wave f as shown in FIG. 3a.

Each of these burst carrier waves f [f^, fB, fc, fD]
is compared in phase with the reference carrier wave fo [fo^, f field, f, foo] output from VC05 at each burst timing in the phase detector 3, and the phase detector 3 detects the phase according to each phase difference. Error voltage v [v^, v
B, vc, vo]. In this case, if the PLL operation is ideal and its synchronization pull-in time is zero, the phase error voltage v of the phase detector 3 rises to the synchronization control voltage at the input timing of each burst, as shown in Figure 3b. However, in reality, the response characteristics of PLL, such as the time constant of LPF4, VC0
Due to the shift position of the oscillation frequency in step 5, the phase error voltage v takes a required time to reach a predetermined synchronous control voltage as shown in FIG. 3c, and oscillations occur in the initial stage. This phase error voltage v [v^, v8, vc, v. ] is L
It is input to PF4, its high frequency component (vibration component) is removed, and the VCO control voltage V[V^, VB, Vc, V. ], and this is input to VC05. The oscillation frequency and phase of VC05 are controlled by this VCO control voltage V, but in this case, since the rise of each control voltage V^, V8, Vc, Vo is worsened, the oscillation output of VC05, that is, the reference Carrier wave fo [fo^, foB, foc, fo. ] takes a considerable amount of time (synchronization pull-in time) 7P to completely synchronize with each burst carrier wave f [f^, f8, fc, fo]. Figure 3e shows the synchronous/asynchronous state.
Each synchronization period within each burst input period is
The synchronization pull-in time is reduced by 7P. Since the conventional carrier wave regeneration circuit is configured as described above, each burst carrier wave f[f^, fB, fc, f.

] is input, the reference carrier wave synchronized with it [f
It takes a considerable delay time (i.e. synchronization pull-in time) 7P to obtain [o^, foB, foc, f], and the phase modulated wave received within this time cannot be demodulated. In a system where the assigned time slots T^ to TD for each slave station A to D are short, such as a multiplex terrestrial line, the ratio of the synchronization pull-in time ↑P to that time slot increases, resulting in a significant drop in transmission efficiency, etc. There were drawbacks. In addition,
As a method to compensate for this drawback, as shown in FIG. 4, LPFs 4a to 4n and VC05a to 5n are provided corresponding to each input burst carrier wave f [f^ to fN], and a converter is used to switch them at the burst timing. 7,
8 and changing the PLL response characteristics for each burst, but in this case as well, it is impossible to significantly shorten the synchronization pull-in time 7P.
Since it is necessary to provide as many PF4s and VC05s as there are burst carrier waves f to be input, the device becomes large, complicated, and expensive. The present invention has been made to eliminate the drawbacks of the conventional ones as described above, and it eliminates the high frequency component of the phase error voltage of each burst carrier wave and holds each output voltage for at least one frame period. The LPF, the LPF output voltage at each burst input timing, and the LPF holding voltage of the next burst are alternately switched and input at each burst timing.
VCOs are provided, and one of the VCOs is connected to the above L.
By inputting the PF output voltage to perform PLL control and inputting the LPF holding voltage to the other VCO to preset its free-running oscillation frequency near the carrier wave frequency of the next burst, the same pull-in time of each burst carrier wave can be reduced. It is an object of the present invention to provide a reference carrier wave regenerating device capable of shortening the transmission time and performing time division multiplex transmission with good transmission efficiency.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 5, numerals 1 to 3 and 6 are the same as those of the conventional device shown in FIG. 10 is the phase error voltage v of each burst output from the phase detector 3 [v^, v8, vc, vo
] for each burst, a first switching circuit 11a
, 11b, 11c, and 11d are LPFs that are provided corresponding to each burst carrier wave f [f^, fB, fc, fo] that is input into the frame, and are configured with a CR integrating circuit or the like having second-order delay characteristics. 1a to 11d are phase error voltages v [v^,
vB, vc, vo], and the output voltage (i.e., VCO control voltage) vV^,
VB, Vc, Vo] are each held for one frame period.

12 is the LPF output voltage V [V^, VB, Vc, Vo] at the input timing of each burst and the LPF holding voltage v-, [V^-,, VB-,, Vc-,
,V.

-, ] to its output lines L, , L2 alternately according to each burst length, 13 and 14 are the LPF output voltages V and The first LPF holding voltage v-, is alternately switched and inputted.
and a second VCO, these VCOs 13 and 14 are LP
The oscillation frequency and phase are controlled according to the F output voltage V or the LPF holding voltage v-. 15 is a third switching circuit that selectively outputs the oscillation output (reproduction reference carrier wave) fo of the VCO 13 or 14 to which the LPF output voltage V is input to the phase detector 3; 16 is a switching circuit 10, 1 for each of these switching circuits;
This is a control circuit that performs switching timing control of Nos. 2 and 15.

Next, the operation of this circuit will be explained using the operation waveform diagrams shown in FIGS. 6a to 6g.

In FIG. 6, a is the burst carrier wave f input to the phase detector 3, b is the phase error voltage v output from the phase detector 3, c is the switching timing of the first switching circuit 10, and d
and e are the first and second VCO control voltages output to the output lines L, L of the second sliding door circuit 12, f is the switching timing of the third sliding door circuit 15, and g is in this embodiment. It is a diagram showing a synchronous/asynchronous state. In FIG. 5, the phase detector 3 receives the burst carrier f [ shown in FIG.
f^, fB, fc, fo] are input as frames. The phase detector 3 detects this burst carrier wave f[f^, fB, fc,
fo] and its reference carrier wave outputted via the third switching circuit 15 also detect the phase difference between [fM, foB, foc, chio], and generate the corresponding phase error voltage v[v^,
vB, vc, vo] are sequentially output from the first switching circuit 10'. This switching circuit 10 outputs the phase error voltage v [v^, vB, vc, vo] to the LPFIs 1a to 11d provided corresponding to each burst at the timing shown in FIG. ~1 1d removes the high frequency component and outputs the output voltage V [VA, V8,
Vc, V. ] is held for one frame period. Note that the switching timing of the first switching circuit 10 includes an idle time of 7 between each burst in order to eliminate the influence of overlapping of adjacent bursts.
o, that is, an interruption period of the phase error voltage v is provided. now,
The burst carrier wave f^ is input at the timing t^, and its phase error voltage v^ is inputted to the LP via the first switching circuit 10.
If it is input to FI 1a, the second switching circuit 12
At timing t^, the LPF output voltage V^ is connected to the output line L.
, and the previous frame LPF output voltage of the burst carrier fB held in the LPFI 1b, that is, the LPF holding voltage VB-, are output to the output lines.

This V^ and V8-・ are the first and second VCO1
3 and 14 respectively, the oscillation frequency of each VCO,
Control the phase. The third gate circuit 15 at this burst timing is connected to the first VCO 13 side to which the LPF output voltage V^ is input, so this VCO
The oscillation output of 13, that is, the reference carrier wave fo^, is input to the phase detector 3. As a result, the PL of the burst carrier f^
L control is performed, and the reference carrier wave fM is output from the output terminal 6. In addition, the LPF holding voltage V of LPFI 1b
The second VCO 14 to which 8-, is input preliminarily sets its eye-running oscillation frequency to the frequency of the burst carrier wave fB of the previous frame.

Next, when the burst carrier wave f8 is input at timing tB and its phase error voltage v8 is input to the LPFI 1b, the second and third switching circuits 12 and 15 are switched, and the second VCO 14 is connected to the LPFI. The output voltage Vs of the LPFI 1b is input to the first VCO 13, the holding voltage Vc- of the LPFI 1c is input to the first VCO 13, and the oscillation output foB of the second VCO 14 is input to the phase detector 3 via the third switching circuit 15. be done. As a result, P of the burst carrier fB
LL control is performed, and the first VCO 13 is preset to the frequency of the burst carrier wave of the previous frame. Below, by performing conversion control using a similar time sequence,
The first and second VCOs 13 and 14 have LPF output voltages V [VA, VB, Vc, V.

] and the next burst's LPF holding voltage V-, [V^-,, V
8-., Vc-., Vo-,] are switched and inputted alternately as shown in Fig. 6 d and e, and one of them, that is, P
The oscillation frequency of the VCO on the side that is not subjected to LL control is set in advance in the vicinity of the next burst carrier frequency. By the way, the synchronization pull-in time 7P of the PLL is proportional to the square of the frequency difference Δ between the input carrier wave signal f and the VCO's running oscillation signal, as shown in the following equation.

In other words, 7〆(△) Tsu2ma Misaki Up to this point: PLL tamping coefficient n: PLL natural angular frequency becomes.

Therefore, as in the above embodiment, by setting the oscillation frequency of the VCO in advance near the carrier frequency of the next burst, that is, by reducing △ in the above equation, the synchronization pull-in time is 7.
P can be significantly shortened. FIG. 6g shows the synchronization/asynchronous state of the PLL in this embodiment, and the synchronization period almost coincides with the input period of each burst carrier.
In the above embodiment, a reference carrier regeneration circuit for synchronously detecting a phase modulated wave has been described, but other signal regeneration can be performed, for example, if a clock extraction circuit for extracting a clock signal is used instead of the non-modulated carrier generation circuit 2. It becomes possible to reproduce the reference clock. It goes without saying that the present invention is applicable not only to multidirectional multiplexed terrestrial lines but also to the reproduction of carrier waves and clock signals transmitted in time division multiplexing, such as in multi-access satellite communications.

As described above, according to the present invention, the L
A PF, and first and second VCOs to which the LPF output voltage at each burst input timing and the LPF holding voltage of the next burst are alternately switched and input at each burst timing are provided. is input to control the PLL, and the above LP is input to the other VCO.
By inputting the F holding voltage, the target oscillation frequency is preset near the carrier frequency of the next burst, so the synchronization pull-in time for each burst carrier can be significantly shortened, and transmission efficiency can be improved. This has the effect of allowing division multiplex transmission. Further, since LPFs corresponding to each burst carrier wave are provided and the VCO control voltage is held in these LPFs, an inexpensive and highly flexible system can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a system overview diagram of a multidirectional multiplex terrestrial line, Fig. 2 is a circuit configuration diagram of a conventional reference carrier regeneration device, Fig. 3 is an operational waveform diagram for explaining the operation of Fig. 2, and Fig. 4 5 is a circuit diagram of another slave device, FIG. 5 is a circuit diagram of a reference carrier regenerating device according to an embodiment of the present invention, and FIG. 6 is an operation waveform diagram for explaining the operation of FIG. 5. . In the figure, 3 is a phase detector, 1 river is the first sliding door circuit, 11a
11b is a low frequency wave generator, 12 is a second switching circuit, 13 and 14 are first and second voltage controlled oscillators, 15 is a third switching circuit, and 16 is a control circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts. 1st
Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. In a device that reproduces each reference carrier wave from N burst carrier waves sequentially input in bursts at a predetermined timing of each frame, detecting a phase difference between each burst carrier wave inputted in bursts and each reference carrier wave, A phase detector that outputs a phase error voltage according to the phase difference is provided corresponding to each of the N burst carrier waves, and is provided to remove high frequency components of each phase error voltage output from the phase detector, and to remove high frequency components of each phase error voltage output from the phase detector. N low-frequency wave generators that maintain the output voltage for at least one frame period, whose oscillation frequency and phase are controlled according to the output voltage of each low-frequency wave generator, and whose oscillation output is controlled by the burst carrier wave. first and second voltage controlled oscillators selectively output to the phase detector as a reference carrier; At the same time, at this switching timing, the output of the low range wave generator of the input burst is switched and input to either the first or second voltage controlled oscillator. , and a switching control circuit that switches and inputs the holding output voltage of the low range wave generator provided corresponding to the next burst to the other voltage controlled oscillator, and each burst holding output voltage held in each of the above low range wave generators is provided. A reference carrier wave reproducing device characterized in that the free-running oscillation frequency of either the first or second voltage controlled oscillator is set near the carrier wave frequency of the next burst by a voltage.