JPH02246695A - Amplitude limiting system in multi-frequency signal receiver - Google Patents

Abstract

PURPOSE:To ensure the reception of an input signal near a signal detection limit level by constituting a device so that the signal of definite amplitude is outputted if the pulse of the amplitude larger than a signal detection level exists among n-pieces of the pulses of a PAM signal. CONSTITUTION:The PAM signal which is PAM-modulated and is separated into the signal of a single frequency is converted into the definite amplitude by an amplitude converting means 1, and is outputted as a bipolar equiamplitude pulse. Besides, the PAM signal is compared with the signal detection level at its amplitude level of each pulse by an amplitude discriminating means 2, and is outputted as amplitude information to a signal detecting means 3. The signal detecting means 3 outputs the amplitude information as signal detection information if there is one piece, at least, of amplitude information discriminated to be larger than the signal detection level among n-pieces of the amplitude information. A signal confirming means 5 inputs a signal confirmation pulse from a signal confirmation period generating means 4 and the signal detection information, and fixes and holds the signal detection information at the point of time when the signal confirmation pulse is inputted, and simultaneously, sends it as signal control information to a signal controlling means 6. The signal controlling means 6 sends or stops sending the bipolar equiamplitude pulse to an output side according to the signal control information.

Description

[Detailed Description of the Invention] [Summary] Regarding an amplitude limiting method in a multi-frequency signal receiver, an amplitude limiting method is provided that ensures the reception of input signals near the signal detection limit level in a digital processing multi-frequency signal receiver. In the amplitude limiting circuit of a multi-frequency signal receiver that receives multi-frequency signals and performs signal identification through digital processing, a signal separated into a single frequency and converted into PAM is input. an amplitude converting means for converting into bipolar equal amplitude pulses and outputting the same; and inputting the PAM signal, identifying whether or not the amplitude level of each pulse of the PAM signal is higher than the signal detection level to generate amplitude information. an amplitude identifying means that sequentially inputs the amplitude information, detects whether or not there is at least one pulse larger than the signal detection level among the latest n pulses, and outputs it as signal detection information. signal detection means for counting clock pulses having the same period as the sampling pulse of the PAM signal and outputting a signal confirmation pulse every time m (m≦n) are counted; A signal confirmation means inputting the pulse and the signal detection information, holding the signal detection information at the time when the signal confirmation pulse is input until the next signal confirmation pulse is input, and outputting it as signal control information, and the signal control The apparatus is configured to include a signal control means that inputs information and the bipolar equal amplitude pulse, and transmits or stops sending the bipolar equal amplitude pulse as an output signal based on signal control information.

[Industrial application field]

The present invention relates to an amplitude limiting method in a multifrequency signal receiver.

In recent years, the mainstream of multi-frequency signal receivers that receive multi-frequency signals such as MF multiplied signals used for selection signals between stations and PB multiplied signals used in butshuhon telephones is one that performs signal identification through digital processing. It's coming. For digital processing, the input signal is PAM (Pulse Amplitude Modulation)
After converting the signal into a single frequency signal, the signal is input to an amplitude limiting circuit.The amplitude limiting circuit converts the input signal within the signal detection level range into a bipolar pulse with a constant amplitude, and sends it to a digital filter to determine the frequency. It is common to identify

In the above, the period of polarity change of the bipolar constant amplitude pulse input to the digital filter is the element for identifying the frequency. This is done each time the negative signal detection (threshold) level is exceeded. If the input is an analog signal, even if a low-level signal close to the signal detection limit is input, if the positive and negative peak levels of the analog signal exceed the signal detection level, the polarity can be reliably changed. It is done. However, when the input is a PAM signal, the sampling pulse does not necessarily coincide with the peak level point, so in the input signal near the signal detection limit, the peak level exceeding the signal detection level is sampled. Points below the signal detection level may be sampled without being detected, and the polarity of the constant amplitude pulse may not be reversed, making the frequency indistinguishable. Even in multi-frequency signals, especially
Since the interval between the PB double signal signal frequencies used for the buttons and dials is small, and the difference between the signal detection level and the non-signal detection level is also small, in a digitally processed multi-frequency signal receiver, the peak value will gradually become the signal as described above. There is a need for a method that reliably detects input signals near the signal detection limit that exceed the detection level.

[Conventional technology]

FIG. 4 is a waveform explanatory diagram of an amplitude limiting circuit in a conventional analog processing multifrequency signal receiver, and FIG. 5 is a waveform explanatory diagram of an amplitude limiting circuit in a conventional digital processing multifrequency signal receiver.

The amplitude limiting circuit is a circuit that converts only the amplitude to a constant level and outputs it without changing the frequency when the level of the input signal is higher than the signal detection level.

No output is sent when the level of the input signal is below the signal detection level.

Figure 4 shows an example in which the amplitude of the analog input signal exceeds the signal detection levels LTH and -LA, and the output signal is at the Lo level at the point where the positive waveform of the input signal exceeds LTH. The level is changed to -L0 at the point where the negative waveform of the input signal exceeds -LTH. As a result, the frequency of the output signal remains the same as that of the input signal, only the amplitude is limited to a constant value (±L6), and the output signal is sent to a bandpass filter that forms part of the configuration of the multifrequency receiver.

FIG. 5 shows an input signal at the same level as FIG. 4, but this is a multi-frequency receiver for digital signal processing, and the input is a PAM signal instead of an analog signal.

Also in FIG. 5, the level of the input signal is La and -L? of the signal detection level. The polarity of the output waveform is switched when the sampling pulse exceeds the signal detection level L?, as shown in part A of the figure. If it is not in the peak portion exceeding H, the polarity of the output waveform is not changed and a pulse like the part B is output. In such a case, it becomes difficult to detect the correct frequency based on the output pulse.

As described above, in a digitally processed multi-frequency signal receiver that inputs a PAM signal, the signal may not be reliably detected even if the peak value exceeds the signal detection level.

Problem to be solved by the invention] As described above, in the amplitude limiting circuit of a multi-frequency signal receiver for conventional digital signal processing, it is difficult to reliably detect low-level input signals near the signal detection limit. It was difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide an amplitude limiting method that ensures the reception of input signals near the signal detection limit level in a digital processing multi-frequency signal receiver.

[Means to solve the problem]

FIG. 1 is a diagram explaining the principle of the present invention.

In FIG. 1, 1 is an amplitude conversion means, which outputs a PAM pulse of an input PAM signal as a constant-amplitude pulse, that is, a bipolar equal-amplitude pulse; 2 is an amplitude discrimination means;
A portion 3 identifies whether or not the level of each pulse of the PAM signal exceeds a signal detection level and outputs the information identified for each pulse as amplitude information, 3 is a signal detection means, and the amplitude identification means 2 sequentially outputs the amplitude information n
at least one among the n pulses,
A part detects whether or not there is a pulse exceeding the signal detection level and outputs it as signal detection information. 4 is a signal confirmation cycle creation means that counts clock pulses having the same cycle as the sampling pulse of the PAM signal. , m pieces (m≦n)
Signal 61 every time I count! The part that outputs the recognition pulse, 5
is a signal confirmation means which inputs a signal confirmation pulse from the signal confirmation cycle generating means 4 and signal detection information from the signal detection means 3, and calculates the signal detection information when the signal confirmation pulse is input into the next signal confirmation pulse. A portion 6 is a signal control means that is held until input and output as signal control information, and inputs the signal control information output from the signal confirmation means 5 and the bipolar equal amplitude pulse from the amplitude conversion means 1. , which is a part for sending out or stopping sending out the bipolar equal amplitude pulse as an output signal according to signal control information.

[For production]

In FIG. 1, a multi-frequency signal is converted into PAM in a not-illustrated portion, separated into single-frequency signals, and input. When the PAM signal is input to the amplitude conversion means 1, each pulse is converted to a constant amplitude and output as a bipolar equal amplitude pulse.

Further, the PAM signal is input to the amplitude identifying means 2, and the amplitude level of each pulse is compared with the signal detection level. As a result of the comparison, it is determined whether the signal is higher or lower than the signal detection level, and is outputted to the signal detection means 3 as amplitude information. The signal detecting means 3 sequentially receives amplitude information from the amplitude identifying means 2, and the latest n pieces of amplitude information are always left in the signal detecting means 3. It is detected whether or not there is at least one piece of amplitude information identified as being larger than the signal detection level, and output as signal detection information. The signal detection information is, for example, "1" indicating signal detection if at least one piece of amplitude information among the n pieces of amplitude information is identified as being larger than the signal detection level.
, otherwise it is output in a form such as "0" indicating that no signal is detected.

The signal confirmation cycle generating means 4 inputs a clock pulse having the same cycle as the sampling pulse of the PAM signal, and repeats the clock pulse a preset number of times, for example, m (m(n
) times, the signal confirmation pulse is sent to the signal confirmation means 5 every time it is counted.
Output to. The signal confirmation means 5 inputs the signal confirmation pulse and the signal detection information outputted from the signal detection means 3,
The signal detection information at the time when the signal confirmation pulse is input is fixed and held. The held signal detection information is held until the next signal confirmation pulse is input, and is sent to the signal control means 6 as signal control information.

The signal control means 6 inputs the bipolar equal amplitude pulse output from the amplitude conversion means 1 and the signal control information, and sends out or stops sending the bipolar equal amplitude pulse to the output side depending on the signal control information. , when the signal detection means 3 outputs signal detection information indicating that at least one piece of amplitude information among the n pieces of amplitude information is larger than the signal detection level, the signal control means 6 outputs the signal detection information such as bipolarity etc. Amplitude pulses are output as equal amplitude signals.

As described above, if a pulse with an amplitude larger than the signal detection level exists among the n pulses of the PAM signal, a signal with a constant amplitude is output.

In the conventional technology, in the case of a PAM signal, when a signal with a level near the signal detection limit is input, there is a possibility that an amplitude level higher than the signal detection level will not be detected because the peak part is not sampled. In FIG. 1, if n is set to a value that includes multiple cycles of the PAM signal waveform, the probability that a signal will not be detected from a waveform with a peak level greater than the signal detection level becomes extremely low.

〔Example〕

FIG. 2 is a configuration diagram of an embodiment of the present invention, and FIG. 3 is a waveform explanatory diagram of the embodiment of FIG.

In Figure 2, 11 is a polarity identification circuit, 12a and 12b are A
ND circuit, 13 is an OR circuit, 14 is an AND circuit, 15 is a polarity conversion circuit, 16 is an addition circuit, 17 is a shift register, 1 is an OR circuit, 19 is a counting circuit, 20 is an AND circuit, 21 is a flip circuit. It is a flop circuit.

In FIG. 2, the input PAM signal is input to the polarity identification circuit 11.
The polarity of the individual pulses is identified in , and the pulses identifying the sign, e.g. positive or 0 level signal pulses, are identified as “
1", a negative level signal pulse is output as "0". The output pulses are input to AND circuits 12a and 12b, and the AND circuits 12a and 12b each have an amplitude that becomes an equal amplitude pulse source. The L0 and -L0 pulses are P
It is input at a period synchronized with the AM signal, for example, PA
When the M signal pulse is at a positive level, the output pulse of the polarity identification circuit 11 is "°l", so the amplitude is higher than that of the AND circuit 12a. The pulse is output to the OR circuit 13. Similarly, when the PAM signal pulse is at a negative level, the AND circuit 812
A pulse of amplitude -Lo is output from b to the OR circuit 13. The OR circuit 13 receives the above output, and the polarity identification circuit 1
It alternately outputs positive or negative pulses of equal amplitude according to the output of 1. That is, the PAM signal is converted into a bipolar equal amplitude pulse.

On the other hand, the PAM signal is input to the polarity conversion circuit 15, rectified, and output to the addition circuit 16. The addition circuit 16 has -L? Since the level of □ is input, the positive level PAM pulse output from the polarity conversion circuit 15 is L? If the level is reduced by H and the remaining level is positive or O, “
1”, if negative, “0” is output.In the above,
The amplitude of each input PAM pulse is at the signal detection level LT.
It is determined whether it is greater than H or not. The output of the adder circuit 16 is added to a shift register 17 so that the latest n
pulses are stored in registers from I+ to I,I. Since the contents of the n registers are input to the OR circuit 18, if at least one "1" pulse is included in the n registers, the OR circuit 18 outputs "1". That is, when "1" is output from the OR circuit 18, it indicates that a signal higher than the signal detection level LTH has been manually applied to the previous n PAM pulses from that point in time.

In parallel with the above, the counting circuit 19 inputs and counts clock pulses synchronized with the input PAM pulse, and sends out an output every time a preset number of times, for example m (m=n), is reached. The output is applied to an AND circuit 20 together with the output of the OR circuit 18. Therefore, for every m pulses mentioned above, OR
The output of the circuit 18 is sent to a flip-flop circuit 21 and set therein. The details of the flip-flop circuit 21 are not shown in the figure, but when the output is output from the counting circuit 19, it resets the information that had been set up to that point, and then calculates the OR at that point.
The output information of the circuit 18 is set. Further, the count of the counting circuit 19 is reset and starts counting anew every time m counts have been performed.

The information set in the flip-flop circuit 21 is output to the AND circuit 14. Since the above-mentioned bipolar equal amplitude pulse is input to the AND circuit 14, when "1" is set in the flip-flop circuit 21,
The AND circuit 14 sends out bipolar equal amplitude pulses as output signals. That is, every time m pulses of the PAM signal are counted, if there is a signal exceeding the signal detection level among the input pulses up to n pulses before, an equal amplitude signal is output.

As described above, when the peak value of the PAM signal waveform has reached the signal detection level, even if the sampling pulse misses the peak value in the signal of one or half cycles, the signal can be detected over multiple cycles. If a signal pulse higher than the signal detection level exists among the n pulses, an equal amplitude signal is output without disturbing the frequency.

FIG. 3 is a diagram explaining the waveform at each point in FIG.
-10, an example of m=5 is shown. In the figure, the half-wave portion of the waveform at point F, indicated by P, is identified as below the signal detection level by the sampling pulse, even though the signal peak level exceeds the signal detection level Lu11.
No signal detection pulse is output at the point, but 1
The output of point H at m4 when the pulse at point counts m for the fourth time, H4 detects two signal pulses (1 and 4) that exceed the signal detection level among the n-10 pulses. At the time m6, "1" is output, and there is no failure to detect a signal higher than the signal detection level.

In addition, in Figure 3, sampling and
Because the pulses are shown with a rough period, the number of pulses of the output equal amplitude signal appears to vary greatly from cycle to cycle, but the actual period is much shorter than shown in the figure, so the frequency can be changed by the output equal amplitude signal. There is no problem in identifying it.

〔Effect of the invention〕

As explained above, according to the present invention, when performing amplitude limitation using a PAM signal in a digital processing multi-frequency signal receiver, even if a signal at the signal detection limit level is received, the influence of sampling Therefore, signal detection does not become uncertain, which greatly contributes to improving the performance of such a multi-frequency signal receiver.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a configuration diagram of an embodiment of the invention, Fig. 3 is a diagram illustrating waveforms of the embodiment of the invention, and Fig. 4 is a waveform of a conventional analog processing amplitude limiting circuit. Explanatory diagram, 5th
The figure is an explanatory diagram of waveforms of a conventional digital processing amplitude limiting circuit. In the figure, 1-- Amplitude conversion means 2 Amplitude identification means 3 Signal detection means 4 Signal confirmation cycle creation means 5
Signal confirmation means 6 This is signal control means.

Claims (1)

[Claims] In an amplitude limiting circuit of a multi-frequency signal receiver that receives a multi-frequency signal and performs signal identification through digital processing, a signal separated into a single frequency and converted into PAM is input and a multiple signal is input. an amplitude converting means (1) for converting the polarity into equal amplitude pulses and outputting the same; an amplitude identifying means (2) for outputting amplitude information; sequentially inputting the amplitude information and detecting whether there is at least one pulse higher than the signal detection level among the latest n pulses; A signal detection means (3) outputting as signal detection information, and sampling/sampling of the PAM signal.
Count the clock pulses with the same period as the pulse and obtain m pieces (m
≦n) A signal confirmation cycle generating means (4) that outputs a signal confirmation pulse every time the signal is counted, and the signal confirmation pulse and the signal detection information outputted from the signal detection means (3) are input, and the signal confirmation pulse is a signal confirmation means (5) that holds signal detection information at the time of input until the next signal confirmation pulse is input and outputs it as signal control information; and outputs the signal control information and the amplitude conversion means (1). A multi-frequency signal receiver comprising a signal control means (6) for inputting a multi-polar equal amplitude pulse and for transmitting or stopping the sending of the multi-polar equal amplitude pulse as an output signal according to signal control information. Amplitude limiting method in .