JPS6218810A - Primary delay equalizing circuit - Google Patents

Abstract

PURPOSE:To equalize primary delay time characteristics of a filter over a wide temperature range by constituting primary delay equalizers which have a positive and a negative gradient including a varactor diode and varying the capacity value of this diode, i.e. Q of the circuit according to ambient temperature. CONSTITUTION:The filter consists of the primary delay equalizer 3 which has the positive gradient, the primary delay equalizer 4 which is connected thereto and has the negative gradient, and a control circuit 5 which controls the gradients of the equalizers 3 and 4 according to temperature variation. The equalizers 3 and 4 are each composed of a coil and a capacitor, but include varactor diodes 3-1 and 4-1 respectively; and the Q of the filter is varied by varying the capacities of the diodes. Further, the control circuit 5 incorporates a temperature compensating sensor 5-1 using a Schottky diode and an output voltage corresponding to the temperature is applied to the varactor diode 3-1 through an amplifier 5-2 and an amplifier 5-3 and further applied to the varactor diode 4-1 through an inversion circuit 6. Consequently, the positive and negative gradients of the two primary delay equalizers vary with the ambient temperature and the primary delay time of the filter is equalized over a wide temperature range.

Description

Detailed Description of the Invention [Summary] In the first-order delay equalization circuit, the first-order delay equalizers 3 and 4 having positive and negative slopes are configured to include variable capacitance diodes, and the diodes are adjusted according to the ambient temperature. The capacitance value, that is, the Q of the circuit is changed. As a result, negative or positive primary delay time characteristics occurring in the transmission path can be equalized over a wide temperature range, and deterioration in error rate can be improved.

[Industrial application field]

The present invention relates to an improvement in a first-order delay equalization circuit used, for example, in a microwave radio system.

FIG. 6 shows temperature change diagrams of the frequency characteristics and delay time characteristics of the filter, where [a] shows the case at room temperature, and (b) shows the case at high or low temperature.

The filter shown in FIG. 6(a) is, for example, a waveguide type filter, and at room temperature, the delay time characteristic in the transmission band f1 to f2 is approximately a second-order delay time characteristic.

However, when the ambient temperature is higher or lower than room temperature, the frequency characteristics shift to the left or right, so the delay time characteristics have a primary delay time characteristic with a positive or negative slope added to a secondary delay time characteristic whose shape hardly changes. It becomes something.

On the other hand, in recent years, there has been a tendency to use, for example, multilevel amplitude modulation methods to improve frequency utilization efficiency, but such methods also have other disadvantages such as primary delay that can satisfy the delay time characteristic standards. is requested.

[Conventional technology]

FIG. 7 shows a block diagram of a conventional example.

In the figure, the microwave input from the terminal IN is extracted by a waveguide type filter 1, for example, to extract only the desired wave, and then amplified, frequency converted, etc., and converted to an intermediate frequency band signal. Other offenses such as primary delay, etc., consisting of
added to. This other sin 2 is designed to equalize the primary delay time characteristic of the filter 1 at room temperature, so after the first component is equalized, the two components are equalized and delayed due to other sins such as secondary delay. An intermediate frequency signal with reduced distortion is sent out from the terminal OUT.

[Problem that the invention seeks to solve]

However, since the primary delay equalizer is adjusted to equalize the primary delay time characteristics of the filter at room temperature, the
), when the ambient temperature changes and the primary delay time characteristics change, it becomes impossible to equalize them.

FIG. 8 shows an explanatory diagram of the operation of FIG. 7.

Figure 8(a) shows equalization when the ambient temperature is room temperature, and the equalization characteristic of the first-order delay equalizer (EQL in the figure) is the -order delay time of the filter (filter in the figure). Since the characteristics are compensated for, equalization is sufficiently performed (composition in the figure), and the delay time characteristics become flat and no delay distortion occurs.

However, as shown in (b) and (C1), when the temperature is high or low, the slope of the filter's primary delay time characteristic becomes steeper or vice versa, but the primary delay time of the primary delay equalizer EQL is For example, since the characteristic has a positive slope and hardly changes, it is not possible to sufficiently compensate for the primary delay time characteristic caused by the filter.

This means that the deviation Δf of the center frequency fo due to temperature change is Δ
It is shown as f=foX temperature fluctuation ratio, but if the temperature fluctuation ratio is constant, the higher fo is, the higher Δf is, indicating that the influence on the delay time characteristics is greater, but f.

This is because a first-order delay equalizer with a low value is less affected by temperature changes than a filter.

For this reason, there is a problem in that the error rate deteriorates when transmitting digital signals.

[Means for solving problems]

The above problem consists of a first-order delay etc. 3 which has a positive slope as shown in FIG. 1, a first-order delay etc. 4 which is connected to the primary delay equalizer and has a negative slope, and a temperature This problem is solved by the first-order delay equalizer circuit of the present invention, which comprises a control circuit 5 that controls the slope of the first-order delay equalizer 3.4 in response to the change.

[Effect]

In the present invention, as shown in FIG. 2, for example, the peak of the delay time characteristic of the first-order delay equalizer 3 having a positive slope is set to the frequency f2,
Adjustments were made so that the peak of the delay time characteristic of the primary delay equalizer 4 having a negative slope would be at the frequency f1, and the capacitance of the variable capacitance diode included in each equalizer was changed. This changes the Q, that is, the positive and negative slopes.

Therefore, if Q is controlled by the control circuit 5 using an output corresponding to temperature changes, the primary delay time characteristics of the filter can be compensated over a wide temperature range, and the deterioration of the error rate can be improved.

〔Example〕

FIG. 3 is a block diagram of an embodiment of the present invention, FIG. 4 is a control characteristic diagram of the control circuit, and FIG. 5 is an explanatory diagram of the operation of FIG. 3.

As shown in Fig. 3, the primary delay etc. 3.4 is composed of a coil and a capacitor, each of which includes a variable capacitance diode (for example, 5 to 25 pf) 3-1.4-1, and this capacitance When Q changes, Q changes.

Further, the control circuit 5 includes a temperature compensation sensor 5-1 using a Schottky diode. Since the voltage drop across this diode changes at approximately -2.3mν/"c, an output voltage corresponding to the temperature is obtained from the amplifier 5-2, which is converted into voltage by the amplifier 5-3 and applied to the variable capacitance diode. .Furthermore, the temperature change of the slopes of the first-order delay equalizers 3 and 4 is
As shown in the figure, the output of the amplifier 5-3 is applied to the variable capacitance diode 4-1 via the inverting circuit 6 for control.

When such control is performed, as shown in Fig. 5, the positive and negative slopes of the vase (EQL-2, EQ in Fig. 4) are
L-1) changes in response to the ambient temperature, and the primary delay time of the filter can be equalized over a wide temperature range as shown in FIG.

For actual adjustment, use a delay time measuring device to display the entire delay time characteristic on the cathode ray tube, and adjust the variable resistor 5-4 (by changing the Q) so that it becomes flat by changing the ambient temperature.
do it.

Capacitor 3-3.3-4 instead of changing direction, Q
When replacing the capacitance with a variable capacitance diode and changing the capacitance value, f1. Since f2 changes, the slope can be changed isometrically.

〔Effect of the invention〕

As explained in detail above, since the filter's primary delay time characteristics can be equalized over a wide temperature range, g% 'l
This has the effect of improving the rate deterioration.

[Brief explanation of the drawing]

Fig. 4 is a control characteristic diagram of the control circuit, Fig. 5 is an explanatory diagram of the operation of Fig. 3, Fig. 6 is a temperature change diagram of the frequency and delay time characteristics of the filter, Fig. 7 is a block diagram of the conventional example, FIG. 8 shows an explanatory diagram of the operation of FIG. In the figure, 3.4 is a primary delay equalizer, and 5 is a control circuit. hj Zuji movement explanation diagram No. 212]
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Claims (1)

[Claims] A first-order delay equalizer (3) with a positive slope; a first-order delay equalizer (4) connected to the first-order delay equalizer and with a negative slope;
); and a control circuit (5) that controls the slope of the primary delay equalizer (3, 4) in response to temperature changes.