JPH09135278A - Output alarm circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To identify an output alarm attribute of an intermediate frequency output alarm and a carrier alarm by using an output alarm discrimination circuit to discriminate an alarm type. SOLUTION: Four bit of data 1-4 are allocated to I, Q-CH channels by 2-bit each and sequentially latched to flip-flop circuits FF1, 5 by using a clock CLK, then given to mixers 4, 8 via D/A converters 2, 6 and LPFs 3, 7. An output of an IF local oscillator 9 is converted into a sine/cosine signal by a hybrid transformer 10 and given to mixers 4, 8. The 2PSK signal output is synthesize by a hybrid transformer 11 and the result is amplified by IFAMP 13, 14 as a 16QAM signal and outputted to an IFOUT. An output alarm discrimination circuit 17 has a carrier ALM terminal in addition to an IFOUTALM terminal to control FF 1, 5 via a carrier on/off SW. Thus, the attribute of output alarm is identified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output alarm circuit, and more particularly to a multilevel QAM in a digital multiplex radio device.
(Quadrature Amplitude Modulation) The present invention relates to an intermediate frequency output (IFOUT) alarm circuit of a modulator.

[0002]

2. Description of the Related Art FIG. 12 shows a conventional multilevel QAM modulator (1
6QAM modulator) and its intermediate frequency output (hereinafter, I
Call it FOUT. 2) shows an example of the alarm circuit of FIG. In FIG. 12, 4-bit data of data 1 to data 4 (indicating one value of 2 ⁴ = 16 values) is divided into I channel (I-CH) and Q channel (Q-CH) whose phases are different by 90 degrees. Two bits are allocated to each (2 ² = one value of 4 values is assigned).

They are clock input terminals (CLKI
N) are sequentially latched by the D type-flip-flop circuits (FF) 1 and 5 of the data input stage by the clock signal from N), and the digital-analog converter (D /
A) Converted to a level signal indicating one of the corresponding four values in 2 and 6.

The output signals from the digital-analog converters 2 and 6 have their harmonic components removed by low-pass filters (LPFs) 3 and 7, and the mixer circuits 4 and 8 at the next stage.
Given to. In the intermediate frequency (IF) local oscillator 9, for example, a 70 MHz local oscillation signal (f
_C = ω _C / 2π) is generated.

The signal is the hybrid transformer 1 in the next stage.
At 0, it is converted into a sine signal (sin ω _C t) and a cosine signal (cos ω _C t) which are orthogonal to each other, and these are supplied to the mixer circuits 4 and 8 as local oscillation signals on the I channel side and the Q channel side.

The output signals from the mixer circuits 4 and 8 are 2
It is considered to be a 2PSK (Phase Shift Keying) signal having a value level (binary level × 2 phases = 4 values), which are combined by the hybrid transformer 11 at the output stage, and are combined in the I-axis and Q-axis directions orthogonal to each other. It is output as a 16QAM signal consisting of a 4PSK signal giving a value level.

The 16QAM signal is amplified by two stages of intermediate frequency amplifiers 13 and 14, and the intermediate frequency output terminal (I
FOUT). The intermediate frequency output alarm circuit (IF ALM) 15 detects the intermediate frequency output signal that has become equal to or lower than a predetermined threshold value, and outputs it from the intermediate frequency output alarm terminal (IFOUT ALM) by using it as an obstacle.

The intermediate frequency output alarm circuit (IF A
The LM) 15 is composed of a level detection circuit using a diode and a comparison circuit that compares the detected rectified output with a predetermined threshold value. For example, it detects that the intermediate frequency output has decreased by 3 dB or 6 dB, and outputs an intermediate alarm signal. Output to the frequency output alarm terminal.

Further, the carrier ON / OFF switch 12
Is a D-type flip-flop circuit (FF)
This is a manual switch for starting / stopping the clock supply from the clock input terminal (CLKIN) for 1, 5 and by which the modulator can be set to the non-modulation state in which only the carrier signal is output. The carrier ON / OFF switch 12 is used at the time of a failure test or maintenance of the device.

[0010]

However, in the modulator of the digital multiplex radio apparatus according to the above-mentioned conventional configuration, whether the content (attribute) of the fault due to the output alarm of the modulator is the output cutoff of the output spectrum or the output is There is a problem that it is difficult to determine the alarm content in the output state because the carrier state cannot be identified.

Further, at the time of maintenance of the digital multiplex radio equipment, the output signal of the modulator is turned on / off the carrier.
The toggle switch on the front surface of the modulator provided as the OFF switch 12 is used to select whether to use the modulated wave or the carrier, and then the micro frequency is measured and adjusted.

However, in the conventional circuit, the carrier signal output state is provided by stopping the clock signal as described above. Therefore, in the case of 16QAM, the D type flip-flop circuit (F.
F) One of the carrier signals having three different vectors is transmitted on the IQ orthogonal coordinates by the latch data of 1 and 5, and the carrier signal level is not constant when the clock is stopped. There was (see FIG. 6).

As a result, an alarm may not be output from the IFOUT alarm terminal due to the level fluctuation of the carrier signal, which is one of the causes of failure. Further, it has been earnestly desired to provide a fixed carrier signal of a fixed level for the measurement and adjustment of the micro frequency.

Therefore, in view of the above problems, an object of the present invention is to provide an alarm circuit of an intermediate frequency output signal (IFOUT) capable of discriminating the attribute of an output alarm.
Another object of the present invention is to provide an intermediate frequency output signal (IFOUT) alarm circuit that keeps the level of a carrier signal constant when an alarm whose output signal is a carrier signal is detected.

[0015]

According to the present invention, in a modulator for modulating a carrier signal by a digital input signal and outputting the carrier signal, an output alarm circuit for warning the abnormality of the output is provided. An output alarm circuit is provided that includes an output alarm determination circuit that determines an attribute indicating a type and outputs a signal based on the attribute.
The signals based on the attributes include an output alarm signal indicating an abnormality in the modulated output signal and a carrier alarm signal indicating a non-modulated state of only the carrier signal.

The output alarm determination circuit extracts a signal spectrum component of the output signal from the modulator, determines its level, and outputs a logical level according to the determination result. A second determination circuit that determines the levels of all spectrum components including a carrier component of the output signal from the modulator, and outputs a logical level according to the determination result, and the first determination circuit and the second determination It consists of a gate circuit that gives the exclusive OR output of the outputs from the circuit.

The first judgment circuit outputs an output alarm signal indicating an abnormality of the modulated output signal as a signal based on the attribute, and the gate circuit outputs only a carrier signal as a signal based on the attribute. A carrier alarm signal indicating the modulation state is output.

Further, according to the present invention, the digital input signal is fixed to a predetermined value by the output of the signal based on the attribute from the output alarm discrimination circuit, and thereby the carrier signal of a constant level is transmitted. A carrier switch circuit that outputs a signal, a manual switch circuit that performs a similar function by a switching signal by a manual operation, and a clock signal that detects an abnormality in a clock signal for capturing the digital input signal, and thereby performs a clock detection that performs the same function. Can have circuitry.

The outputs from the respective circuits are concentrated in an OR gate circuit, and the digital input signal is fixed to a predetermined value by the output signal thereof, whereby a carrier signal of a constant level is sent out.

The modulator is a multilevel QAM modulator used in a digital multiplex radio apparatus, and the output signal from the modulator is an intermediate frequency output signal (IF signal).

[0021]

1 shows a basic block configuration of an intermediate frequency output alarm circuit according to the present invention. FIG. 2 shows another basic block configuration of the intermediate frequency output alarm circuit according to the present invention. FIG.
The circuit block configuration of the 16QAM modulator in each of the following drawings including is the same as that described in the conventional example of FIG. 12, and the same reference numerals are used for the corresponding blocks. Therefore, they will not be described further in the following description.

In FIG. 1, an output alarm discrimination circuit 17 according to the present invention is a conventional intermediate frequency output alarm circuit 15.
(Fig. 12) Intermediate frequency output alarm terminal (IFOUT
In addition to ALM, the carrier alarm terminal (carrier A
LM). In addition, conventional carrier ON / OF
The switch 12 (FIG. 12) is a clock signal (CL) for the D-type flip-flop circuits (FF) 1 and 5.
K) was controlled to be supplied / stopped, whereas the carrier ON / OF switch 16 according to the present invention uses the output alarm discrimination circuit 17 to clear the clear terminals (CLR) of the D type flip-flop circuits 1 and 5. Control.

In FIG. 2, the carrier ON / OF is further added.
An OR gate circuit 18 is provided to a portion corresponding to the switch 16, a control signal from the output alarm discrimination circuit 17 is provided at one input, and a conventional carrier ON / OF switch 12 (is provided at the other input. A manual switch 19 for carrier ON / OF corresponding to FIG. 12) is provided.

FIG. 3 shows a specific circuit configuration example of the output alarm discrimination circuit 17 according to the present invention described above. In FIG. 3, the intermediate frequency amplifier (IF AM
The intermediate frequency output signal (including all of the signal spectrum component and the carrier component) from P) 13 is rectified by the detector 21 and given to one input of the comparator 1 (25). A predetermined threshold value for confirming the normal level of the intermediate frequency output signal is given to the other input of the comparator 25.

The intermediate frequency output signal is further applied to a band elimination filter (BEF) 22 which removes only the carrier signal component thereof, and only the signal spectrum component thereof is passed through the detector 23 in the same manner as described above to obtain the signal spectrum. It is applied to a comparator 2 (24) having a predetermined threshold that confirms the normal level of the component. The outputs of the comparators 24 and 25 are exclusive ORed by an exclusive OR gate circuit (EX-OR) 26.

FIG. 4 shows an operation truth table of the output alarm discrimination circuit of FIG. In FIG. 4, each of the outputs (X, Y) of the comparators 1 and 2 has an output of 1 (abnormal) when the input signal level thereof is equal to or less than the predetermined threshold value.
Becomes In the normal state, both the signal spectrum component and the carrier signal component are equal to or more than the predetermined threshold value (0, 0), and therefore the exclusive OR thereof is also 0.

At the time of failure (0, 1) in which only the carrier signal component exists, the carrier alarm terminal (carrier ALM) which is the output of the exclusive OR gate circuit 26 becomes 1. It should be noted that there cannot be a state (1,0) in which there is no carrier signal component but only a signal spectrum component. Further, in the state (1, 1) where both the carrier signal component and the signal spectrum component do not exist, the intermediate frequency output alarm terminal (IFOUT ALM) becomes 1.

FIG. 5 shows a concrete circuit configuration example of the case of FIG. 5, the circuit configuration of the output alarm discrimination circuit 17 of FIG. 2 is the same as that of FIGS. 3 and 4 described above, and the same reference numerals are attached.
Therefore, they will not be described further here.

The output of the exclusive OR gate circuit 26 becomes 1 at the time of failure (0, 1) in which only the carrier signal component exists as described above, and the signal is the OR gate circuit 18.
The D-type flip-flop circuits 1 and 5 are cleared via one of the inputs. As a result, unlike the conventional case where the clock signal (CLK) is stopped, the outputs of the D-type flip-flop circuits 1 and 5 are automatically cleared (set to zero) regardless of the latch data value at that time. ) Will be done.

As a result, carrier signals of the same level are always output. Also, when the carrier ON / OF switch 19 is manually set to 1, the same result as above can be obtained.

FIG. 6 shows an example of the output vector of the 16QAM modulator. FIG. 6 shows that the output of the 16QAM modulator can take three vector level values ˜.

FIG. 7 shows a carrier alarm (carrier AL
M) is a diagram showing an example of an output vector at the time of transmission. In FIG. 7, the carrier alarm terminal (carrier AL
When M) becomes 1, it indicates that the level values of three vectors in FIG. 6 automatically become the level values of a constant vector. The same applies when the carrier ON / OF switch 19 of FIG. 5 is manually set to 1.

FIG. 8 shows a basic configuration when an input disconnection detecting function is added to the intermediate frequency output alarm circuit according to the present invention. The input break detection circuit 31 shown in FIG. 8 is composed of, for example, a retriggerable timer that is always triggered by the input clock signal (CLK) in a normal state. Then, when the input clock signal is cut off for a predetermined time or more, the time-out output signal is output via the OR gate circuit 18 to D
Clear the type-flip-flop circuits 1 and 5.
The subsequent operation is as described above.

FIG. 9 shows a concrete circuit configuration example of the intermediate frequency output alarm circuit according to the present invention including the input disconnection detecting function of FIG. In FIG. 9, a clock input break alarm terminal (clock input break ALM) is newly added as an alarm output terminal. Others are the same as the circuit configuration of FIG. 5 and will not be described here.

FIG. 10 shows the operation truth table of FIG. FIG. 11 shows the operation truth table of FIG. 9 in more detail. 9 and 11 can be considered to be a combination of the truth table of FIG. 4 and the condition of the CLK input interruption. Therefore, from the combination, whether the carrier state at the time of failure is due to the clock input interruption or other causes. This makes it possible to distinguish whether or not there is a non-modulation state.

[0036]

As described above, according to the present invention, i) the attributes of the output alarm (IFOUT ALM, carrier ALM, and clock input interruption ALM) can be identified, and ii) the carrier level can be made constant, and at that time, automatic Or you can keep the carrier level constant by either manual,
And so on.

Although the present invention has been described with respect to the 16QAM modulator, it can be similarly applied to a multilevel QAM of 32QAM or more. Further, it is obvious that the same can be applied to a modulator using another modulation method that modulates and outputs a carrier signal. According to the present invention, even in that case, there is an advantage that the cost can be reduced without changing the circuit scale.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic block configuration of an intermediate frequency output alarm circuit according to the present invention.

FIG. 2 is a diagram showing another basic block configuration of an intermediate frequency output alarm circuit according to the present invention.

3 is a circuit block diagram showing a specific circuit configuration example of the output alarm determination circuit of FIG.

4 is a diagram showing an operation truth table of the output alarm discrimination circuit of FIG.

FIG. 5 is a circuit block diagram showing a specific circuit configuration example in the case of FIG.

FIG. 6 is a diagram showing an example of an output vector of a 16QAM modulator.

FIG. 7 is a diagram showing an example of an output vector when a carrier alarm (carrier ALM) is transmitted.

FIG. 8 is a diagram showing a basic block configuration when an input break detection function is added to the intermediate frequency output alarm circuit according to the present invention.

9 is a circuit block diagram showing a specific circuit configuration example in the case of FIG.

10 is a diagram showing an operation truth table (1) of FIG.

FIG. 11 is a diagram showing a more detailed operation truth table (2) of FIG. 9;

FIG. 12 is a block diagram showing an example of an intermediate frequency output alarm output circuit in a conventional 16QAM modulator.

[Explanation of symbols]

 1, 5 ... D type type-flip-flop circuit 2, 6 ... Digital-analog converter 3, 7 ... Low-pass filter 4, 8 ... Mixer circuit 10, 11 ... Hybrid transformer 12, 14 ... Intermediate frequency amplifier 16, 19, ... Carrier ON / OFF switch 18 ... OR gate circuit 22 ... Band elimination filter 26 ... Exclusive OR gate circuit

Claims (11)

[Claims] 1. In a modulator for modulating a carrier signal by a digital input signal and outputting the modulated carrier signal, an output alarm circuit for warning an abnormality of the output discriminates an attribute indicating a warning type of the output alarm, and the attribute thereof is determined. An output alarm circuit including an output alarm determination circuit for outputting a signal based on the above. 2. The output alarm circuit according to claim 1, wherein the signal based on the attribute includes an output alarm signal indicating an abnormality of a modulated output signal and a carrier alarm signal indicating a non-modulated state of only a carrier signal. 3. The first determination circuit, wherein the output alarm determination circuit extracts only a signal spectrum component from the output signal from the modulator, determines its level, and outputs a logical level according to the determination result. A circuit, a second judging circuit for judging levels of all spectrum components including a carrier component of an output signal from the modulator, and outputting a logical level according to the judgment result, and the first judging circuit.
2. The output alarm circuit according to claim 1, further comprising a gate circuit for providing an exclusive OR output of the outputs of the determination circuit and the second determination circuit. 4. The first determination circuit outputs an output alarm signal indicating an abnormality of a modulation output signal as a signal based on the attribute, and the gate circuit only outputs a carrier signal as a signal based on the attribute. 4. The output alarm circuit according to claim 3, which outputs a carrier alarm signal indicating the non-modulated state of. 5. A carrier switch circuit for fixing the digital input signal to a predetermined value by the output of a signal based on the attribute from the output alarm discrimination circuit, thereby transmitting a carrier signal of a constant level. The output alarm circuit according to claim 1, comprising. 6. The output alarm circuit according to claim 1, further comprising a manual switch circuit for fixing the digital input signal to a predetermined value by a switching signal by a manual operation and thereby sending a carrier signal of a constant level. 7. A clock detection circuit for detecting an abnormality of a clock signal for fetching the digital input signal, wherein the digital input signal is fixed to a predetermined value when an abnormality is detected, and thereby a carrier of a constant level is provided. The output alarm circuit according to claim 1, wherein a signal is transmitted. 8. The output alarm circuit according to claim 7, wherein the clock detection circuit outputs a clock alarm signal indicating the abnormality when the clock signal is abnormal. 9. The output alarm discrimination circuit outputs a signal based on the attribute to fix the digital input signal to a predetermined value, thereby outputting a signal for transmitting a carrier signal of a constant level. Carrier switch circuit, manual switch circuit that outputs a signal that fixes the digital input signal to a predetermined value by a switching signal by manual operation, and thereby outputs a carrier signal of a constant level, and a clock for capturing the digital input signal At least one of the clock detection circuits that has a clock detection circuit for detecting an abnormality of the signal, fixes the digital input signal to a predetermined value when the abnormality is detected, and outputs a signal for transmitting a carrier signal of a constant level by the fixed value In addition, the carrier switch The digital input signal is fixed to a predetermined value by collecting a plurality of signals from the circuit, the manual switch circuit, or the clock detection circuit, and outputting a logical sum signal thereof, thereby sending a carrier signal of a constant level. The output alarm circuit according to claim 1, further comprising a gate circuit. 10. The output alarm circuit according to claim 1, wherein the modulator is a multilevel QAM modulator in a digital multiplex radio apparatus. 11. The output alarm circuit according to claim 10, wherein the output signal from the modulator is an intermediate frequency output signal (IF signal).