JP2929973B2 - Analog service channel circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an analog service channel (hereinafter referred to as A) for a demodulator of a digital microwave communication device.
The present invention relates to an ASC circuit having a configuration in which unnecessary ASC output is prevented when a power is turned on and when a power is turned off, and a malfunction does not occur in a control device or the like.

[0002]

2. Description of the Related Art Conventionally, in a multi-phase PSK modulation or a multi-level quadrature amplitude modulation system, a main signal n-ary PSK or n-ary QAM modulated carrier is further added to a service channel (hereinafter ASC).
There is known a method in which a signal is frequency-modulated and transmitted, and an ASC signal is demodulated in a carrier recovery circuit on the receiving side. An example of an ASC circuit used in the above-mentioned conventional demodulator will be described with reference to block diagrams of FIGS. 3 and 4 and a time chart of FIG.

FIG. 3 shows main blocks of a demodulator including an ASC circuit. In the figure, an input signal a is supplied to a phase detector 1. The signal a is input to the phase detector 1 together with a reproduced carrier f output from the VCO 3 that generates a reproduced carrier having a center frequency of the carrier of the signal a, and is subjected to in-phase detection. The signal b output from the phase detector 1 is a baseband signal containing various data information.

The baseband signal b is subjected to signal processing such as A / D conversion in which various signals included in the baseband signal b input to the discriminator 2 are discriminated and reproduced. A phase information signal c identified for each predetermined modulation phase is output. The phase information signal c includes an ASC signal. This phase information signal c is sent to the APC detection circuit 4.

The phase information signal c sent to the APC detection circuit 4 is output as a reproduced carrier control signal e for controlling the VCO 3 so that the phase difference between the input carrier and the reproduced carrier is made close to 0 after a predetermined arithmetic processing. You. APC detection circuit 4
Is sent to the ASC circuit 5. ASC circuit 5
ASC signal g from input reproduced carrier control signal e
Is detected and output.

FIG. 4 shows an ASC circuit for transmitting an ASC signal from the reproduced carrier control signal e output from the APC detection circuit, and has a function of amplifying the ASC signal to a certain level. The reproduced carrier control signal e output from the APC detection circuit 4 which is supplied with the positive and negative power supply voltages + E and -E and is operated is input to the ASC circuit 5.

The ASC circuit 5 detects only a frequency component used for the ASC signal from the reproduced carrier control signal e,
Output as SC signal g. And the ASC circuit is A
An SC output circuit 51 and an operational amplifier 52 for amplifying the output of the ASC output circuit 51 to a required level by a feedback resistor 53
, A capacitor 54 connected to the ASC signal g1 output from the operational amplifier 52 to cut the DC component, a matching resistor 55 for matching the impedance of the external output, and converting to the balanced ASC signals g2 and g3 to the outside. An output transformer 56 was provided.

FIG. 5 is a time chart of FIG. (1) of the figure is a power supply voltage supplied to the APC detection circuit 4,
(2) is an ASC signal output from the ASC circuit 5 and having a frequency that fluctuates randomly within a certain frequency band (however, in this figure, it is represented by a fixed frequency for simplicity). The power supply voltage + E supplied to the APC detection circuit 4 in the configuration shown in FIG.
As shown in FIG. 5, when V and -EV are turned on and off without time, the ASC signal output from the ASC circuit is output at the same time as the power is turned on, and the output is stopped at the same time as the cutoff.

[0009]

SUMMARY OF THE INVENTION
In the SC circuit, there is no problem when the positive and negative power supplies supplied to the APC detection circuit are simultaneously turned on and off, but the positive and negative power supplies normally supplied to the APC detection circuit have the same demodulation. It is also supplied to another circuit in the device, and there may be a time difference between turning on and off the positive and negative power supply due to the difference in the load capacity and the difference in the power supply voltage from the ground potential.

When there is a time difference between the turning on and off of the positive and negative bipolar power supplies, the signal output from the APC detection circuit becomes noise when one of the power supplies is turned on first, resulting in noise.
It has a drawback that it is output from the SC circuit and causes a malfunction in the communication control and monitoring system.

That is, FIG. 6 is a diagram showing a time chart in a case where there is a time difference between the turning on and off of the positive and negative power supply voltages in the configuration of FIG.

In FIG. 1A, the positive power supply (+ E) of the power supply voltage supplied to the APC detection circuit is changed to the negative power supply (-E).
It shows a state in which the power supply is turned on with a delay of t1 and the power is turned off with a delay of t2.

In this case, since the APC detection circuit 4 does not operate normally in the output g of the ASC output circuit 51 shown in (2), noises of k1 and k2 are generated at the time when the time difference occurs. This noise is also amplified by the outputs g1 and g2 of the ASC circuit 5 as shown in (3), and k1 ',
k2 '.

In order to prevent the generation of such noise, an ASC circuit as shown in FIG. 7 has been used.

That is, when the NPN transistor 62 and the PNP transistor 63 are connected to the output of the amplifier 52, for example, when only the negative power supply (-E) is turned on, the transistor 63 is turned on and the output of the amplifier 52 is forced. To the ground potential connected to the collector terminal of the transistor.

This operation can also be applied when only the positive power supply (+ E) is turned on.

As a result, output of noise from the ASC circuit 5 is prevented.

However, in this circuit, the transistors 62, 6
3 is in the ON state, a slight forward voltage VCE is generated between the emitter and the collector, so that noise due to the time difference between the turning on and off of the positive and negative power cannot be completely prevented, and the time chart shown in FIG. As in (3), the noise k3
k4 occurs. Therefore, this circuit has a disadvantage that the noise cannot be completely prevented.

An object of the present invention is to solve the above-mentioned problem by monitoring the power supply voltage of the positive and negative poles and detecting a time lag between turning on and off the power supply and turning on either of the power supplies first. An object of the present invention is to provide an ASC circuit which prevents a signal output from an APC detection circuit from being output from the ASC circuit as noise and prevents a signal control and monitoring system from malfunctioning with an ASC signal.

[0020]

An ASC circuit according to the present invention comprises:
In a demodulator for digital microwave communication, a VCO for generating a reproduced carrier, a composite modulated wave input signal obtained by further frequency-modulating a carrier modulated by a main signal with a service channel signal, and a reproduced carrier from the VCO. Receiving the baseband signal detected and output by the phase detector, identifying and reproducing information included in the baseband signal, and outputting a phase information signal And a VC which receives the phase information from the discriminator and performs predetermined arithmetic processing so as to eliminate the phase difference between the carrier wave and the reproduced carrier wave.
An APC detection circuit for outputting a reproduced carrier control signal for controlling O, and an ASC circuit for receiving the reproduced carrier control signal output from the APC detection circuit and outputting a service channel signal, the positive and negative signals supplied to the APC circuit. 2. A means for monitoring the power supply voltage, detecting when one of the polarities is abnormal, and stopping the output of the ASC circuit.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention using the ASC circuit 5 shown in FIG. APC in FIG.
The detection circuit 4 operates with positive and negative power supply voltages + E and -E.

The reproduced carrier control signal e output from the APC detection circuit 4 is input to the ASC circuit 5 and the ASC signal g
Is output from an ASC output circuit 51, and an ASC signal g1 amplified to a required level by an operational amplifier 52 and a feedback resistor 53 is input to a power supply voltage detecting unit 7 after passing through a capacitor 54 for cutting a DC component.

The signal transmitted from the power supply voltage detecting section 7 passes through a resistor 55 for adjusting the impedance of the output and the balanced A
It is output to the outside as an ASC signal demodulated by a transformer 56 that converts the signal into SC signals g2 and g3.

The configuration of the power supply voltage detector 7 will be described with reference to FIG. On the anode side of the PIN diode 71, a DC cut capacitor 54 and a resistor 70 connected to the positive electrode power supply + E are connected. A DC component cutting capacitor 76 and a resistor 72 connected to a ground potential (G) of 0 V are connected to the cathode side. A DC component cutting capacitor 76 of the preceding stage and a negative power supply -E are provided on the cathode side of the PIN diode 74.
Is connected to the resistor 73. Further, on the anode side, a DC component cutting capacitor 75 and a resistor 77 connected to G which is a potential of 0 V are connected. The capacitor 75 is connected to the output impedance matching resistor 55.

Next, the operation of the power supply voltage detection circuit section 7 will be described with reference to a time chart in the case where there is a time lag between the turning on and off of the positive and negative power supplies as shown in FIG.

The power supply -E supplied to the APC detection circuit 4
+ Power of the same polarity noise that time difference to the insertion is applied in the case resulting in E is generated from APC detection circuit 4, only t1 hours ASC signal g output of ASC circuit 51 of FIG. 2 (2)
It appears like the k1 part.

Similarly, when the power is turned off, the time t2 is equal to k.
Occurs as two parts. First, the operation of the power supply voltage detection unit 7
The negative power supply -E is released earlier than the positive power supply + E by the time t1.
The case where the input is performed will be described. PIN diode 7
Reference numerals 1 and 74 denote PIN diodes which function as resistors having good linearity determined by a constant DC forward bias current . PI
When a voltage −E is applied to the resistor 73, a current determined by the resistors 73 and 77 flows through the N diode 74.
It turns on and has a small resistance value .

On the other hand, the DC bias current does not flow in the PIN diode 71 unless the + E power supply is applied to the resistor 70, and the resistance value of the PIN diode 71 becomes infinite (2).
Is not output from the power supply voltage detector 7. Similarly, when the negative power supply -E is cut off earlier than the positive power supply + E by the time t2, the voltage of the PIN diode 74 becomes 0 V applied to the resistor 73. The noise signal is not output from the power supply voltage detection unit 7.

Accordingly, the ASC signal is output from the ASC circuit 5 only when the positive and negative bipolar power supplies are normally applied as shown in (3). The case where the negative power supply -E is turned on and off first has been described above, but the same effect can be naturally obtained when the positive power supply + E is turned on and off first.

As described above, this circuit does not generate an ASC signal output unless a DC bias current flows through the PIN diode based on the voltages of the positive and negative power supplies, so that the above-described noise can be completely suppressed. doing.

The circuit of the present invention is a PIN diode,
The circuit can be easily configured with a resistor and a capacitor. Even if the power supply of either polarity is turned on or off first, the noise generated by the APC detection circuit can be prevented from being output from the ASC circuit to the outside. doing.

[0033]

As described above, according to the present invention, there is a time difference between the turning on and off of the positive and negative power supplies supplied to the APC detection circuit with a simple configuration, and the positive and negative power supplies are turned on and off. Also, the noise generated from the APC detection circuit is A
It is possible to prevent the control device from malfunctioning due to noise output from the SC circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an ASC circuit of the present invention.

FIG. 2 is an operation time chart of FIG.

FIG. 3 is a block diagram illustrating an example of an ASC circuit used in a demodulator.

FIG. 4 is a block diagram of an example of a conventional ASC circuit.

FIG. 5 is an operation time chart of FIG. 4 (no difference between positive and negative power supply times).

6 is an operation time chart of FIG. 4 (there is a positive / negative power supply time difference).

FIG. 7 is a block diagram illustrating an example of a conventional output stop circuit.

FIG. 8 is an operation time chart of FIG. 7;

[Explanation of symbols]

 Reference Signs List 1 phase detector 2 discriminator 3 VCO 4 APC detection circuit 5 ASC circuit 7 power supply voltage detection section 51 ASC output circuit 52 operational amplifier 53 resistor 54 capacitor 55 resistor 56 transformer 57 capacitor 58 resistor 59 resistor 60 zener diode 61 zener diode 62 transistor 63 transistor 70 resistor 71 pin diode 72 resistor 73 resistor 74 pin diode 75 capacitor 76 capacitor 77 resistor

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H04L 27/00-27/38

Claims (4)

(57) [Claims] 1. An ASC for receiving an output of an APC detection section of a carrier recovery circuit of a received signal of digital microwave communication and outputting an analog service channel (abbreviated as ASC) signal
The circuit, further comprising a prohibiting means for prohibiting the output of the ASC circuit from being output to the outside when one of the two power supply voltages supplied to the APC circuit is equal to or lower than a predetermined voltage. ASC circuit characterized by the above-mentioned. 2. The prohibition means includes a first diode in which the positive power supply conducts above the predetermined voltage and a second diode in which the negative power supply conducts below a predetermined voltage in series with the ASC output. The ASC circuit according to claim 1, wherein the ASC circuit is connected. 3. The ASC according to claim 2, wherein said first and second diodes are pin diodes.
circuit. 4. The ASC circuit according to claim 2, wherein said predetermined voltage is determined by values of resistors respectively connected to said first and second diodes.