JPH043531A - Automatic band control system - Google Patents

Abstract

PURPOSE:To offer a signal equalization section with an optimum band at all times by applying feedback so that a leading time of an output signal sent from a band control section and a trailing time are constant by a control voltage thereby controlling the band. CONSTITUTION:A band detection section 6 detects the leading time and the trailing time of an output signal of a band control section 4 and after a reference voltage section 5 detects '1', '0' in the output signal of the band control section 4, the result of detection is extracted and recovered by using a clock signal, a reference voltage comparing a signal before clock extraction and recovery and a signal after clock extraction and recovery to keep the result constant is generated and the voltage is fed to a feedback amplifier 7. Thus, a control voltage fed to a band control section 4 by comparing both output signals of a reference voltage section 5 and a band detection section 6 at the feedback amplifier 7 is generated thereby applying feedback so that the leading time and the trailing time of the output signal sent from the band control section 4 are made constant. Thus, a signal equalizing section having an optimum band is always obtained.

Description

[Detailed Description of the Invention] [Summary] Regarding the equalization section of the reception section of a digital transmission path, the high cutoff frequency of the equalization filter is controlled according to the signal transmission speed and the dispersion and fluctuation of the band of the equalization section. , the purpose of which is to provide a signal equalization section that always has an optimal band, and which equalizes and identifies the received signal in the digital signal reception section, by adding a control signal from the outside to vary the amplification gain. a band control section that is controlled to change the band of the output signal; a band detection section that detects the rise time and fall time of the output signal of the band control section and outputs a signal proportional to the both times; an identification unit that compares the output signal of the band control unit with an identification level to detect “1” and “0” in the signal, and punches and reproduces the detection result using a clock; and a clock punching of the identification unit. a reference voltage section that compares the pre-regeneration signal and the clock punched and post-regeneration signal and generates a reference voltage corresponding to the band to be kept constant; and a reference voltage section that compares both output signals of the reference voltage section and the band detection section to determine the frequency range of the above band. A feedback amplifier is provided that generates a control voltage to be applied to the control section and applies feedback so that the rise time and fall time of the output signal sent from the band control section are constant values using the control voltage, and the output signal is equalized. The nine regions are controlled so that the rise time and fall time of the digital signal are always constant.

[Industrial application field]

The present invention relates to a receiver of a digital transmission line.

[Conventional technology]

FIG. 3 is a diagram showing a circuit configuration of a conventional embodiment. In the figure, 1 is a light receiving element, and 2 is a preamplifier 21, an automatic gain control amplifier (hereinafter referred to as AGC amplifier) 22, an equalization filter 23, a first comparison circuit 24, and a peak detector 25.
and a reference voltage 26. Note that 3 is an identification section including a second comparison circuit 31, an identification level 32, and an FF circuit 33.

In FIG. 3, a light intensity modulated signal received by the light receiving element 1 is detected, converted into an electrical signal, and input to the equalization section 2. Note that the received optical signal is, for example, 100 Mbi.
It is a signal consisting of "1" and "0" at a speed of t/s. In the equalization section, the preamplifier 21 performs low noise amplification of the electrical signal, and the AGC amplifier 22 amplifies it to a predetermined level that can be identified. , the equalization filter 23 performs equalization processing such as noise processing to make the signal easy to identify, and outputs it to the identification section 3. In the identification section 3, the second comparison circuit 31 converts the output signal of the equalization filter 23 to the identification level. 32 and discriminates between "1" and "0", performs punching reproduction using a clock in a Frisopfromp circuit (hereinafter referred to as FF circuit) 33, and sends out output data with suppressed jitter etc.Furthermore, In the equalization unit 2, the amplitude of the signal input to the equalization filter 23 is peak-detected in a peak detector 25 so that the output amplitude output from the equalization filter 23 is constant,
The peak detected voltage and the voltage value of the reference voltage 26 are compared in a first comparison circuit 24 so that they become equal, and in addition to the AGC amplifier 22, the gain of the AGC amplifier 22 is automatically controlled.

The equalization filter 23 of the equalization section 2 typically uses a low-pass filter. This is to remove high frequency noise contained in the signal. Therefore, the lower the high cutoff frequency (hereinafter referred to as fch) of the equalization filter 23 is, the better in order to remove wide-band noise, but if it is low enough to remove passing signal components, the rising and falling edges of the signal waveform will deteriorate. This causes code amount interference. Also, the preamplifier 21
There is also an fch in the AGC amplifier 22, and the fc
h changes greatly due to variations in elements, ambient temperature, power supply voltage, etc., and is less stable than the equalization filter 23. Therefore, the fch of the equalization section 2 is equalized by the equalization filter 23.
preamplifier 2 as determined by the low-pass filter of
1 and the AGC amplifier 22 must be made sufficiently wider than the band of the low-pass filter of the equalization filter 23. Note that the normal band is an input signal of approximately 100 Mbit.
/s, the frequency including the preamplifier 21 and AGC amplifier 22 is 200MHz, and the equalization filter 23 is 60MHz.
It is selected by z.

[Problem to be solved by the invention]

Therefore, using a preamplifier and an AGC amplifier in a band larger than necessary causes increased power consumption, oscillation, peaking of gain-frequency characteristics, etc., and it is necessary to select and use an equalization filter that is optimal for the transmission speed. There is a problem.

An object of the present invention is to control the high cutoff frequency of an equalization filter according to variations and fluctuations in the signal transmission speed and the band of the equalizer, and to provide a signal equalizer that always has an optimal band. do.

[Means to solve the problem]

The present invention is a device that equalizes and identifies a received signal in a digital signal receiving section, and the present invention is a band control device that is controlled to change the band of an output signal by adding a control signal from the outside to vary the amplification gain. detecting the rise time and fall time of the output signal of the band control unit 4 and the band control unit 4;
A band detecting section 6 outputs a signal proportional to both times, and the output signal of the band controlling section 4 is compared with the identification level to detect "1" and "0" in the signal, and the detection result is an identification section 3 that performs punching reproduction using a clock; and a reference voltage section 5 that compares a signal before clock punching reproduction and a signal after clock punching reproduction of the identification section 3 and generates a reference voltage corresponding to a band to be kept constant. , compares the output signals of the reference voltage section 5 and the band detection section 6 to generate a control voltage to be applied to the band control section 4, and uses the control voltage to control the rise of the output signal sent from the band control section 4. A feedback amplifier 7 is provided to apply feedback so that the time and fall time are constant values, and the band is controlled so that the rise time and fall time of the digital signal to be equalized are always constant. It is.

[For production]

In the present invention, as shown in FIG. After detecting "1" and "0" in the clock, the detection result is punched and reproduced using a clock, and the signal before the clock punching and reproduction is compared with the signal after the clock punching and reproduction is kept constant. A voltage is generated and applied to the feedback amplifier 7.

Therefore, in the feedback amplifier 7, by comparing both the output signals of the reference voltage section 5 and the band detection section 6, a control voltage to be applied to the band control section 4 can be generated. Feedback can be applied so that the rise time and fall time of the output signal sent from the control section 4 are set to constant values.

〔Example〕

FIG. 1 is a diagram showing the circuit configuration of the present invention, and FIG. 2 is a diagram showing the operation of the reference voltage section of the present invention.

In the figure, 1 to 3 are the same circuits as the conventional example, 1 is a light receiving element, 2 is a preamplifier 21, an automatic gain control amplifier (hereinafter referred to as AGC amplifier) 22, a first comparison circuit 24, and a peak detection element. 25 and a reference voltage 26.

Note that 3 is an identification section including a second comparison circuit 31, an identification level 32, and an FF circuit 33. In addition, 4 to 7 are circuits of the present invention, 4 is a band control section comprising a resistor R, a capacitor C, and an equalization AGC amplifier 41, and 5 is an EOR circuit 51 that performs an exclusive OR operation, a DC smoothing circuit 52, and an attenuation circuit. 53. Note that 6 is a band detection section,
First reference voltage 61, second reference voltage 62, and third comparison circuit 6
3 and a DC smoothing circuit 64. Furthermore, 7 is a feedback amplifier, which includes a differential amplifier 71 and a low-pass filter 72 that passes a low-frequency signal. The details of this circuit will be explained below.

In FIG. 1, a received optical signal is detected by a light receiving element 1, converted into an electrical signal, and inputted to an equalization section 2. Note that the received optical signal is "1" at a speed of 100 Mbit/s, for example.
and “0” electrical signals. This electric signal is controlled in the band control section 4 of the present invention so that it is maintained at a constant band by a control signal input from the outside, and then input to the identification section, where it is punched and reproduced using a clock and output data is sent out. do.

The circuit operation will be explained in detail below.

(1) Bandwidth control unit 4 When the gain of the equalization AGC amplifier 41 is A, the transfer function G from input to output is: The high cutoff frequency fch is fch= (Hz)2π
RC (1+A) 2 trowels, R: resistance value [Ω] C: capacitance value CF'] ω: angular frequency (rad/sec), and by adding a control signal from the outside, equalizing AGC amplifier 4
Bandwidth can be controlled by controlling the gain A of 1.

(2) Band detection unit 6 Since it is difficult to directly detect the band, the rise time (Tr) and fall time (Tr) and fall time (Tr), which have a certain relationship with the band, are difficult to detect directly.
Tf) is detected.

A DC voltage proportional to the number of Tr and Tf of the input signal Vf is outputted to the output Vj. That is, V j = n x
t p x Vi −−−−−−−−−−−−−−
−−−−−−−−−−−−−(3) Where, n: rr for 1 second, number of [pieces/5ec] tp: Tr
and Tf time (sec) Vi: output limiter amplitude (V) of the third comparator circuit 63; detects the rise time and fall time of the output signal of the band control section 4, and is proportional to both the rise and fall times. outputs a signal Vj.

(3) Identification unit 3 and reference voltage unit 5 The output of the band detection unit 6 described above includes a voltage proportional to the number n of Tr and G, in addition to the time of Tr and Tf. Try to remove it.

Therefore, as shown in FIG. 1, in the identification section 3 and the reference voltage section 5, the signal Vl, which is compared and sent out by the second comparison circuit 31, is punched and reproduced in the F' F circuit 33 at the clock Vm and output data. Sends Vn. These signals vi and Vn are subjected to an exclusive OR in an EOR circuit 51, and a signal Vo having an amplitude value of VO and a pulse width of 1/2 of the clock period T is sent out. The signal Vq is smoothed and sent through an attenuator 53. This Vq is calculated using the following formula % n: Number of Tr, TfO per second [pcs/5ec) tpo:
172 hours of clock period C5ec) Vo:EOR
Output limiter amplitude (V) Att of circuit 51: attenuator 53
Attenuation amount (input/output) of the output signal V of the band control section 4
By comparing f and identification level Vk, the input signal “1” and “
0'' is detected, generates a signal Vt, 2, sends a signal Vn obtained by punching and reproducing the signal Vl using a clock Vm, compares it with the signal Vl, and generates a reference voltage Vq corresponding to a band to be kept constant. do.

(4) Feedback amplifier 7 A control signal Vc is supplied to the band control unit 4 so that the signal Vj from the band detection unit 6 and the signal Vq from the reference voltage unit 5 are equal.
Output. In other words, in equations (3) and (4), Vj=Vq and V
If i = Vo, then tp = tp 0/Att -・-11------
・・−・−−11−−−−−−−−−−−−−−・−(
5) [Effects of the Invention] As is clear from the above description, according to the present invention, there is no need to provide a preamplifier and an AGC amplifier that amplify signals with a band larger than necessary, resulting in lower power consumption. It is possible to avoid obstacles such as peaking in gain-frequency characteristics, and to improve characteristics that enable stable amplification by keeping the band optimal. Furthermore, systems with different transmission speeds can be handled without changing the circuit.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the circuit configuration of the present invention, FIG. 2 is a diagram showing the operation of the reference voltage section of the present invention, and FIG. 3 is a diagram showing the circuit configuration of a conventional embodiment. In the figure, (2) is a light receiving element, 2 is an equalization section, 3 is an identification section, 4 is a band control section, 5 is a reference voltage section, 6 is a band detection section, and 7 is a feedback amplifier. -Z ÷ Semi-invented fundamental voltage y nv ts Figure 2

Claims (1)

[Claims] In a device that equalizes and identifies a received signal in a digital signal receiving section, a band that is controlled by applying an external control signal to vary the amplification gain and change the band of the output signal. Control part (4)
and a band detection section (6) that detects the rise time and fall time of the output signal of the band control section (4) and outputs a signal proportional to the both times, and the output of the band control section (4). an identification unit (3) that compares the signal with an identification level to detect “1” and “0” in the signal, and punches out and reproduces the detection result using a clock; and a clock punching of the identification unit (3). a reference voltage section (5) that compares the pre-reproduction signal and the clock punched and post-reproduction signal and generates a reference voltage corresponding to a band to be kept constant; and the reference voltage section (5) and the band detection section (6). A control voltage to be applied to the band control section (4) is generated by comparing both output signals, and the rise time and fall time of the output signal sent from the band control section (4) are set to constant values by the control voltage. This automatic band control method is characterized in that it is equipped with a feedback amplifier (7) that applies feedback so that