JPH02177732A - Fading monitoring circuit for variable amplitude equalizer - Google Patents

Abstract

PURPOSE:To monitor waveform distortion in a transmission band by using a 1st monitoring circuit, detecting a notch frequency due to selective fading, detecting the depth of the notch with a 2nd monitoring circuit and bringing the botch frequency due to the fading to a prescribed value in a monitoring voltage processing circuit. CONSTITUTION:A resistor 19 monitors a voltage across a varactor element 17 from a control section 38 and the voltage is led to a monitoring voltage processing circuit 20. A voltage representing a notch frequency is outputted to a terminal 22 and a voltage representing the depth of the notch is outputted to a terminal 23. Since a voltage deciding the center frequency of a variable resonance circuit 12 of a variable amplitude equalizer 9 is applied to the resistor 19, the absence of selective fading is represented by setting a voltage outputted at the terminal 22 to be, e.g. 0V when the voltage of resistors 14, 15 is a certain voltage or below. When the voltage at the resistors 14, 15 is a certain voltage or over, a voltage Vf representing the notch frequency is outputted at the terminal 22.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a variable amplitude equalizer that equalizes selective fading occurring in a propagation path in a wireless communication system, in which deterioration of amplitude characteristics due to the selective fading is The present invention relates to a fading monitoring circuit that monitors fading.

[Conventional technology]

FIG. 6 shows a block diagram of a conventional flat fading monitoring circuit. In the figure, +1) is a variable attenuator, (2) is an amplifier, (3) is amplifier 2, and (4)
is a power detector, (5) is a feedback amplifier, (6) is an input terminal, (7) is an output terminal, and (8) is a feedback voltage monitoring output terminal.

The conventional flat fading monitoring circuit is configured as described above, and is an AGC amplifier that amplifies the received power that changes moment by moment due to fading that occurs in the propagation path and automatically amplifies it to a certain level. perform an action. A signal with level fluctuations input from the input terminal (6) is attenuated by the variable attenuator (1) and then passed through the amplifier (
2) and (3), the amplified signal level is detected by a power detector (4), DC amplified by a feedback amplifier (5), and used as a control voltage to drive a variable attenuator (1). In other words, when the signal wave input from the input terminal (6) is attenuated, the detection level at the detector (4) decreases after amplification, and the control voltage decreases, so the amount of attenuation of the variable attenuator (1) decreases, and the output terminal The signal power output to (7) is a negative feedback that tends to be constant. In this case, the voltage output from the feedback amplifier (5) to monitor the control voltage changes in proportion to the signal power input to the terminal (6), and level fluctuations caused by reaging can be monitored as a voltage value. Therefore, the output terminal (8) from the feedback amplifier (5) is used as a flat fading monitoring circuit.

[Problem to be solved by the invention]

The flat fading monitoring circuit as described above only monitors the level of the input signal as a voltage value, and cannot monitor waveform distortion within the transmission band due to selective fading.

That is, the conventional configuration monitors the total power within the transmission band, and is not suitable for monitoring selective waveform distortion occurring within the transmission band.

The present invention was made to solve these problems, and its purpose is to monitor waveform distortion within a transmission band due to selective fading.

[Means to solve the problem]

A fading monitoring circuit for a variable amplitude equalizer according to the present invention uses a first monitoring circuit to monitor a voltage applied to a variable capacitance element for automatically controlling the resonant frequency of a variable resonant circuit of a variable amplitude equalizer, The voltage or current applied to the variable resistance element for automatically controlling the sharpness of the variable resonance circuit of the variable amplitude equalizer is monitored by a second monitoring circuit, and further from the first monitoring circuit and the second monitoring circuit. , and when the signal from the second monitoring circuit is below a predetermined value, a monitoring voltage processing circuit is provided which sets the output from the first monitoring circuit to a predetermined value.

[Effect]

In this invention, the first monitoring circuit detects the depression frequency of selective fading, the second monitoring circuit detects the depression depth of selective fading, and the monitoring voltage processing circuit detects the depression frequency of selective fading. When the input signal from the monitoring circuit No. 2 for monitoring the depth of fading drop is less than a predetermined value, the fading drop frequency is set to a predetermined value.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, in which (9) is a variable amplitude equalizer, σO is a resonant circuit, and α force is P
A variable resistance element such as an IN diode, (2) a variable resonance circuit composed of a variable capacitance element αη and a resonance circuit α0, which will be described later, and (C) a bias resistance at the center of the variable resistance element α, O4
and O5 is a resistor that monitors the current flowing through the variable resistance element, and constitutes a second monitoring circuit. Ql is a control signal terminal applied to the variable resistance element aυ, aη is a variable capacitance element such as a variable capacitance diode that automatically controls the resonant frequency of the variable resonant circuit @, (to) is the bias resistance of the variable capacitance element <17), and Ql is a resistor that monitors the voltage applied to the variable capacitance element aη, and constitutes a first monitoring circuit. (to) is a control signal terminal applied to the variable capacitance element Q7), and Q is a resistor αΦ.

QQ, a monitoring voltage processing circuit connected to QQ, @ is a voltage output terminal related to the frequency of fading, (E) is a voltage output terminal related to the depth of fading, (C)
is a carrier wave input terminal, (E) is an AGC amplifier connected to the output of the variable amplitude equalizer (9), and (1) is a carrier wave input terminal (
Fading detection unit connected to (A), (C) is AG
The equalization characteristic detection section is connected to the output terminal of the C amplifier section (a), the control section (to) is connected to the fading detection section (to) and the equalization characteristic detection section, and the wire is the carrier wave output terminal. , (7)
0η is a first control circuit consisting of a fading detection section (4) and a control section (to), and 0η is a second control circuit consisting of an equalization characteristic detection section (sub) and a control section (to). It is.

In Fig. 1, the AGC amplification section (c), fading detection section (e), equalization characteristic detection section@, control section (support), and variable amplitude equalizer (9) are shown in the literature (1983 m-child communication The configuration circuit of a variable resonant automatic equalizer using sweep control shown in the General Conference of Japanese Academic Society (FF12019) can be used.

As shown in Figure 2, a carrier wave with propagation path distortion due to selective fading exhibits a spectrum in which the characteristics of an anti-resonant circuit are superimposed, and a carrier wave with such distortion in the frequency domain is processed by a variable amplitude equalizer. Automatic equalization is possible using (9). A variable amplitude equalizer (9
) is equalized by automatic control of the center frequency and sharpness of the variable amplitude equalizer (9), following the anti-resonance characteristics of the carrier wave subjected to selective fading distortion.

In FIG. 1, a carrier wave with propagation path distortion inputted from a carrier wave input terminal is branched. This branched carrier wave is input to a fading detection section (1).

This fading detection section) detects a fading dip frequency and outputs a first detection signal. This first
The detection signal is processed by the microprocessor of the control section (support). After that, the control section (to) the variable resonance circuit (2)
A first control voltage for determining the resonant frequency of is applied from the terminal (e) to the variable capacitance element an of the variable amplitude equalizer (9) via the resistor (to).

The first control voltage varies the resonant frequency of the variable resonant circuit (2) and follows the falling frequency of selective fading. The first control voltage value indicates the center frequency of the variable resonant circuit (2) and represents the drop frequency of the selective fading being followed.

On the other hand, the output signal of the variable amplitude equalizer (9) is amplified to a required level in the AGC amplifier section (c) and then branched at the output section. This branched output signal is used to detect a level deviation within the carrier wave band in an equalization characteristic detection section, and outputs a second detection signal. The second detection signal is the control unit @
The microprocessor processes the signal so that the in-band level deviation is minimized. Then, the control unit (to) supplies a second control voltage to the variable amplitude equalizer (9) via the resistor (to) from the terminal α0 as a signal for controlling the sharpness Q of the variable amplitude equalizer (9). is applied to the variable resistance element α0. The second control voltage is applied to the variable resistance element α of the variable amplitude equalizer (9) to vary the sharpness Q of the variable resonance circuit @. This is related to the depth of the drop in the selective fading. If the depth is large, the current flowing through the variable resistance element αυ is controlled to be small and the sharpness Q is increased. Therefore, the depth of the selective fading drop is known by the current flowing through resistor 0, and the potential difference across the resistor is proportional to the current, so the voltage (Vt, ) monitored by resistor 0 and αυ is This represents the depth of selectivity fading.

FIG. 4 is a diagram illustrating the depth of fall in selective fading with monitored voltage (VL).

The larger the monitored voltage (VL), the smaller the depth of the fading dip. Conversely, if the monitored voltage (VL) is small, the depth of fading will be large.

In FIG. 1, the resistor Ql monitors the voltage applied from the control section to the variable capacitance element (17), and this voltage is
The voltage is guided to the monitoring voltage processing circuit t21). This monitoring voltage processing circuit c! The resistors α◆ and 0θ for monitoring the depth of fading depression and the resistor Ql for monitoring the frequency of fading are received and subjected to voltage processing. A voltage representing the depression frequency is output to the terminal die, and a voltage representing the depression depth is output to the terminal -.

Since the voltage that determines the center frequency of the variable resonance circuit 4 of the variable amplitude equalizer (9) is applied to the resistor (11) even when there is no selective fading, the voltage value of the resistors a◆ and αG is below the voltage. For example, the voltage output to the terminal) is o
(V) indicates that selective fading does not occur. When the voltage value of the resistor α→, aR exceeds the voltage, a voltage (Vf) representing the falling frequency is output to the terminal (2).

FIG. 6 is a diagram illustrating the drop frequency of selective fading depending on the voltage monitored in FIG. 5;

The greater the monitored voltage (vf), the greater the drop frequency shift.

In this example, a variable amplitude equalizer (9
) The control signal applied from the control section (to) to the output of the variable resistance element that adjusts the sharpness of the variable resonant circuit (6) was used as the second control voltage, but it is also possible to use it as a control current.

〔Effect of the invention〕

As described above, according to the present invention, the control voltage for controlling the variable amplitude equalizer is monitored and processed to monitor the depression frequency and depression depth of selective fading. There is no need for a fading analyzer, etc., and inexpensive monitoring can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a characteristic diagram of selective fading, FIG. 3 is a characteristic diagram of a variable amplitude equalizer (9), and FIG. Figure 5 is a relationship diagram between the monitored first voltage and the frequency of depression in selective fading, and Figure 6 is a diagram showing conventional fading monitoring. FIG. 2 is a block diagram showing a circuit. In the figure, (9) is a variable amplitude equalizer, α is a variable resistance element, @ is a variable resonant circuit, α is a resistance, (A) is a resistance, α
η is a variable capacitance element, a is a resistor, (A) is a voltage processing circuit, 翺 is a control section, (7) is a first control circuit, and C3'D is a second control circuit. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] A variable amplitude equalizer consists of a variable resonant circuit including a variable capacitance element that changes the resonant frequency, and a variable resistance element that changes the output impedance of the signal source that applies the signal to this variable resonant circuit, and detects the received signal. a first control circuit that outputs a voltage to be applied to the variable capacitance element for automatically controlling the resonant frequency of the variable resonant circuit; and a first control circuit that detects a received signal and automatically controls the sharpness of the variable resonant circuit. a second control circuit that outputs a voltage or current to be applied to the variable resistance element, a first monitoring circuit that monitors the voltage applied to the variable capacitance element to detect a drop frequency of selective fading; a second monitoring circuit that monitors the voltage or current applied to the variable resistance element to detect the depression depth of selective fading; and a second monitoring circuit that receives signals from the first and second monitoring circuits; A fading monitoring circuit for a variable amplitude equalizer, comprising a monitoring voltage processing circuit that sets the output from the first monitoring circuit to a predetermined value when the signal from the first monitoring circuit is below a predetermined value.