JPS6013348B2 - Timing signal correction circuit - Google Patents

Description

[Detailed Description of the Invention] In a differential phase modulation wave detection circuit, detecting the phase information at a position where there is less intersymbol interference in a time slot to form one piece of phase information improves the characteristics of the detection circuit. This is an important deciding factor.

Therefore, the timing signal that determines the detection position of the time slot needs to be of high quality. The present invention relates to a timing signal correction circuit for correcting this detection position to a more ideal position. Conventionally, a timing signal once extracted is used as is, and no consideration has been given to correcting the timing signal.

An object of the present invention is to perform detection at a more ideal position by correcting the extracted timing signal, thereby improving the characteristics of the detection circuit.

Conventionally, a difference signal between both sideband waves of a differential phase modulated wave (hereinafter referred to as a received carrier) has been used as a timing signal.

In this case, when the received carrier passes through the carrier line, both sideband waves of the received carrier are affected by group delay distortion, so the difference signal of both sideband waves changes its phase, and is created from the difference signal. The resulting timing signal changes the position at which the phase information of the time slot is detected. The present invention uses the changing points (referred to as cross points of the eye pattern) of the baseband signal (hereinafter referred to as the eye pattern) obtained by demodulating the received carrier to restore the above-mentioned timing signal to its original state, and as a result, the time slot This is a timing signal correction circuit that corrects the phase of detecting phase information.

Generally, the center between the cross points of the eye pattern is a position in the time slot where there is less intersymbol interference, and is considered to be the best position for detecting phase information.

Furthermore, if there are multiple eye patterns, there will be multiple cross points (referred to as a Kuroho point group). In this case, the best position is the center between the cross point groups. Embodiments of the present invention will be described in detail below with reference to the drawings. A first embodiment of the invention is shown in FIG.

The waveforms of each part are shown in FIG. This is an embodiment of a four-phase differential phase modulation wave detection circuit (see, for example, a phase modulation system for wideband data transmission published by Tsuken Research Fund on March 29, 1967) having two A-patterns. Signals from the baseband signal generation circuits of FIG. 1 110 and 120 FIG. 2 a and b
The cross point detection circuits 150 and 160, for example, constituted by differentiating circuits, generate signals indicating the cross points of A as shown in FIG. 2c and d. On the other hand, a square-law detection circuit 13 such as a well-known full-wave rectifier circuit, ring modulator, or saddle calculation circuit detects the received carrier, and a fundamental wave extraction circuit 140 extracts a signal as shown in FIG. 2e. A cross point detection circuit 170 generates a signal f in FIG. 2 indicating a cross point of the signals here.

A signal shown in FIG. 2g is generated by a synthesis circuit such as an OR circuit 180.

A fundamental wave extraction circuit composed of, for example, a tuning circuit of 141 extracts the fundamental wave from this signal and generates a timing signal as shown in Fig. 2h.
make.

For example, a digital PLL circuit 190 generates a signal k in FIG.

Considering the above explanation, the best detection position for the eye patterns shown in FIGS. 2a and 2b is as shown in FIG. 2i.

On the other hand, if a timing signal is created in the conventional manner using a signal whose detection position is slightly shifted as shown in FIG. 2e, the signal shown in FIG. 2i will be obtained. On the other hand, the timing signal shown in FIG. 2 k obtained by the present invention is closer to the ideal position shown in FIG. 2 i, so that the characteristics of the detection circuit are improved. Another embodiment is shown in FIG.

In this embodiment, 140 and 170 are omitted from the embodiment shown in FIG. Instead, in the synthesis circuit 380 in Fig. 3, after ORing the outputs of 150 and 160, the output and the output of 130 are synthesized using an analog circuit such as a hybrid, and the timing signal is extracted from the output. It is. Another embodiment is shown in FIG.

The waveforms of each part are shown in FIG. This embodiment is also an embodiment in which two eye patterns similar to the embodiment of FIG. 1 are provided. Signals from the baseband signal generation circuits of FIG. 4 110 and 120 FIG. 5 a and b are 150 and 16
A cross point detection circuit constructed of, for example, a differential circuit of 0 generates a signal indicating a cross point of A as shown in FIG. 5c and d. A combination circuit, such as an OR circuit, at 580 combines these signals to produce a signal as shown in FIG. 5e.

The fundamental wave extraction circuit 540 extracts the signal shown in FIG. 5f from this signal.

On the other hand, the detection circuit 130 detects the received carrier, and the detection circuit 140 detects the received carrier.
The fundamental wave extraction circuit extracts the signal shown in Fig. 5g. 58
As shown in FIG. 6, the timing signal correction circuit 1 corrects the phase of the signal g in FIG. 5 to h using the signal f.

The method is to create a signal f' using, for example, a phase shift circuit from a signal f, and then create a signal f' and g
By combining these, the timing signal is corrected as shown in h. Figure 5 is i, i, k. Figure 2 is i, i, k.
Since it is the same as , the explanation will be omitted. As explained above, with the timing signal correction circuit of the present invention, it is possible to correct the position of the extracted timing signal whose position has shifted, and it is possible to detect the received carrier at an ideal position, thereby improving the characteristics of the detection circuit. It can be improved.

[Brief explanation of the drawing]

FIG. 1, FIG. 3, and FIG. 4 show an embodiment of the present invention, FIG. 2, FIG. be. In the figure, 110 and 120 are baseband signal generation circuits;
30 is a square law detection circuit, 140, 141, 5401 are fundamental wave extraction circuits, 150, 160, 170 are cross point detection circuits, 180, 380, 580 are synthesis circuits, 581 is a timing signal correction circuit, 100' is an output terminal , 19 Kawama P
It is an LL circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 6 Figure 5

Claims (1)

[Claims] 1. In a timing signal extraction circuit of a differential phase modulated wave synchronous detection circuit, a means for extracting a timing signal, a means for detecting a change point of a baseband signal output from the synchronous detection circuit, and a means for detecting the timing signal and the change. A timing signal correction circuit comprising: means for calculating a sum with an output signal; and correcting the timing signal using an output signal of the means for calculating the sum.