JPS6328542B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a PCM transmission device, and more particularly to a device for multiplex transmitting general speech signals and different types of analog signals having different bandwidths, etc. over the same transmission path as general speech signals.

Generally, in a time-division PCM multiplex transmission system, multiple analog signals with the same frequency bandwidth and noise tolerance are each sampled at the same sampling frequency (e.g., 8 kHz), and the sampling values have the same number of bits ( Each digital signal is sequentially arranged in multiple time slots on one frame (one time slot consists of, for example, 8 bits) to form a time division multiplexed signal frame. Multiplex transmission is performed on one transmission path. With such a PCM transmission method,
It is not easy to transmit different types of analog signals with different frequency bands and noise tolerances than normal analog signals. By using n time slots, it is possible to transmit an analog signal with n times the band, and it is also possible to transmit signals with less quantization noise. In general, by using n x m time slots for one normal signal (hereinafter referred to as 1 channel), that is, time slots for nm channels, an analog signal with n times the bandwidth can be converted into m times the number of bits. Although transmission is possible, it is not easy to transmit a signal with an arbitrary band and an arbitrary number of bits. For example, if you want to send a signal with a band that is 1.5 times as large, you will need twice as many time slots, which has the disadvantage that you cannot use the transmission path effectively. In practice, it is often necessary to transmit a signal of somewhat higher quality than a normal signal, for example, a signal with a bandwidth of about 1.5 times and with somewhat less quantization noise. In such a case, doubling the bandwidth and doubling the number of bits per sampling would require time slots for four channels, which is not economical.

In view of the above-mentioned circumstances, an object of the present invention is to provide a PCM transmission device that can economically transmit different types of analog signals having different bandwidths and noise amounts.

The transmission device of the present invention transmits N analog signals sampled by sampling pulses of a constant frequency.
In a PCM transmission device that converts the N-bit digital signal into a digital signal and transmits and receives the N-bit digital signal by arranging multiple sets in one frame, a different kind of analog signal having a different bandwidth, etc. a control timing pulse generator that creates a sampling pulse for sampling with a sampling pulse having a frequency of [4/3×N]
The second converts and outputs a bit digital signal.
The output signals of the PCM transmission device and the second PCM transmission device are sequentially stored, and the stored digital signals are transmitted per frame [4/3 ×N〕×
and a buffer memory device that outputs 1.5 bits at a time, and outputs the output signal of the buffer memory device as described above.
It is characterized in that it is combined with the output signal of the PCM transmission device and output.

Here, the symbol [ ] is a Gauss symbol, and [x]
represents the largest integer not exceeding x.

Next, the present invention will be explained in detail with reference to the drawings.

The present invention samples different types of analog signals using sampling pulses with a frequency that is 1.5 times the sampling frequency of general analog signals, and the number of bits per sample is approximately 4/3 times the normal number N of bits in one channel. Convert the number into a digital signal. Then, a digital signal with 4/3 times as many bits as above is transmitted using two time slots for one normal channel. Since there are two time slots remaining, the increased sampling frequency can be divided and inserted into the remaining time slots. Therefore, by using the time slots for two channels, it is possible to transmit a signal with 1.5 times the frequency bandwidth at approximately 4/3 times the number of bits per sample, and the transmission path can be used effectively.

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a time chart showing signals of various parts of the above embodiment. In this embodiment, the audio signal is
An example of application to a normal PCM transmission device that samples with kilohertz sampling pulses, converts each sample to an 8-bit digital value, arranges 24 channels of signals into a 125 microsecond frame, and multiplexes the signals. state That is, the input terminal
When normal audio signals from A ₁ to _{A 24} are input to the first PCM transmission device B, the first PCM transmission device B
The signal from each input terminal is sampled by an 8 kHz sampling pulse C _f as shown in Fig. 2C, and each indicated value is converted into an 8-bit digital signal, as shown in Fig. 2a. The multiplexed signal b arranged in 24 time slots as shown in FIG. In the same figure, b ₀ is a frame synchronization signal,
b ₁ to _{b 24} each represent 8-bit digital signals for 24 channels. Each bit of the above signal is shown in Figure b.
It is synchronized to a 1.544 MHz multiplexed clock signal C _b as shown in FIG. The length of one frame, that is, the interval between frame synchronization signals _b0 is 125 microseconds. The above is the same as a normal PCM transmission device, but in this embodiment, the input terminals A ₂ ,
A normal audio signal is not input to _A3 . Using these two channels, the analog signal with a frequency bandwidth of 6 kHz that is input to the input terminal A ₂₅ is sampled using a 12 kHz sampling pulse, and the sample value is converted into a 10-bit digital signal. send. For this purpose, the multiplexed clock signals C _b and 8 are transmitted from the first PCM transmission device B.
A kilohertz sampling pulse C _f is supplied to a control timing pulse generator C, and the control timing pulse generator C generates a signal as shown in e in the figure based on the above signal.
A sampling pulse C ₂ of 12 kHz and a delimiter identification signal C ₁ as shown in d of the figure are generated. The delimiter identification signal C ₁ is used to indicate the delimiter of a signal obtained by digitizing different types of analog signals, and is obtained by dividing the sampling pulse C _f by two. Note that it is delayed by 8 bits with respect to the sampling pulse C _f . The multiplexing clock C _b and the sampling pulse C ₂ are supplied to a second PCM transmission device D, which converts the different analog signals input from the input terminal A ₂₅ into the 12 kHz sample. The sampled value is converted into _a 10-bit digital signal and output in series in synchronization with the multiplexed clock signal _Cb . The 10-bit digital signal becomes a 10-bit signal d following the sampling pulse _C2 , as shown in FIG. 2f. The signal d is sent to the buffer memory device E and temporarily stored therein. The buffer memory device E has
A multiplexed clock signal C _b , a 12 kHz sampling pulse C ₂ and a delimiter identification signal C ₁ are supplied, and based on these signals, the digital signals are arranged and output as shown in FIG. 2g. . That is, following the delimiter identification signal _C1 , there is a 10-bit digital signal _d0 from the previous frame, followed by a signal d1, which is the first half (5 bits) of the digital signal d of the current frame, for a _total of 15 bits. Send out. Let this signal be _e1 . At the midpoint of the delimiter identification signal _C1 , a total of 15 signals, including the last half signal _d2 (5 bits) of the digital signal d and the next digital signal d' (10 bits), are generated.
A bit is sent out. Let this signal be _e2 . Following the next delimiter identification signal _C1 , the 10-bit signal _d0 of the previous frame and the signal _d1 of the first half of the current frame are transmitted in the same way as described above. That is, from the buffer memory device E, the delimiter identification signal C ₁
15 bits are sent out per frame in synchronization with . These signals e ₁ and e ₂ are the signal b ₂ shown in Figure 2a.
and b corresponds to the time slot to be sent in ₃ . The multiplexed signal b, the delimiter identification signal C ₁ and the signals e ₁ and e ₂ are combined by an OR circuit F and output from the output terminal F ₁ . OR circuit F
As shown in FIG. _2h , the output signal _of
bit) Separator identification signal C ₁ (1 bit), signal e ₁
(15 bits) and 4th to 24th channel signals b ₄
Following a frame of 125 microseconds consisting of ~ _b24 , a frame synchronization signal _b0 , a signal _b1 of the second channel, a 1-bit "0" pulse, a signal _e2 , and a signal b of the 4th to 24th channels. A frame consisting of ₄ to _b24 is sent out. Thereafter, the above two types of frames are sent out sequentially. Delimiter identification signal mentioned above
A 16-bit signal consisting of signal e ₁ followed by C ₁ is
If f _1A is a 16-bit signal consisting of a 1-bit "0" pulse followed by a signal e ₂ as f _2A , the signal f _1A is a 10-bit signal d ₀ as shown in Figure 2g. and a 5-bit signal _d1, for a total of 15 bits, and the signal _f1B includes a 5-bit signal d2 and _a 5-bit signal d1, as shown in the figure.
Contains a total of 15 bits of the 10-bit signal d'. In other words, the time slots for two channels (4 time slots) in the two frames of multiplexed signal b
Three bit digital signals are transmitted. Therefore, the frequency band from the above two frame signals is
It is possible to demodulate heterogeneous analog signals with 10 bits per sampling at 1.5 times. Note that the delimiter identification signal C ₁ is used to distinguish the signals f _1A and f _1B and to assemble a demodulated signal.

In this example, the heterogeneous analog signal has a frequency band of 6 kHz and is sampled with a sampling pulse C ₂ having a frequency (12 kHz) that is 1.5 times higher than the sampling pulse C _f (8 kHz) of a normal audio signal. Since each sample value is converted into a 10-bit digital signal, higher quality signal transmission is possible.
Then, three of the above 10-bit digital signals are inserted into two channels of time slots (16 bits).
Since I configured it to send and receive data using two
Three frames are sent. That is, three 10-bit signals (30 bits) are normally sent in four time slots (32 bits) of the channel. Therefore, there is an effect that the use efficiency of the transmission path is good.

Generally, in a PCM transmission device that converts and transmits an analog signal sampled by a sampling pulse with a frequency of f Hertz into an N-bit digital signal, different types of analog signals are converted into N-bit digital signals.
When sampling with a sampling pulse of 1.5 times the frequency, set the sampling value to [4/3 x N]
It can be converted into a bit digital signal.
Here, the symbol [ ] is a Gauss symbol, and in the above example, [4/3×8] is 10. When 4/3×N is an integer, completely efficient information transmission is possible, but demodulation becomes somewhat complicated. By selecting [4/3×N]×1.5 to be smaller than 2N, demodulation in the receiving section is facilitated by using the difference from 2N bits as a delimiter identification signal.

As described above, in the present invention, a different kind of analog signal having a different bandwidth and noise standard from a normal analog signal is sampled using a sampling pulse with a frequency 1.5 times that of a normal sampling pulse, and the sample value is obtained. Since it is configured to convert into a [4/3 x N] bit digital signal and transmit the digital signal using two channels of normal signals, it has the effect of improving the efficiency of using the transmission path. . Moreover, if the above-mentioned [4/3×N]×1.5 is selected to be smaller than 2N, the difference is used as a delimiter identification signal, which has the effect of facilitating demodulation. The decrease in the efficiency of use of the transmission line due to this is extremely small.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a time chart showing the signals of each part of the above embodiment. In the figure, _A1 to _A25 ...input terminals, B...first
PCM transmission device, b...Multiplexed signal, _b0 ...Frame synchronization signal, _b1 to _b24 ...8-bit digital signal,
C... Control timing pulse generator, C _b ... Multiplexed clock signal, C _f ... 8 kHz sampling pulse, C ₁ ... Delimiter identification signal, C ₂ ... 12 kHz sampling pulse, D... Second PCM transmission. device, d,
d ₀ , d'...10-bit digital signal, d ₁ ...First half 5-bit signal of digital signal d, _d2 ...Last half 5-bit signal of digital signal d, E...Buffer memory device, e ₁ , e ₂ ...Signal output from the buffer memory device, F...OR circuit, _F1 ...output terminal.

Claims (1)

[Claims] 1. Converting the analog signals A ₁ to _{A 24} sampled by a sampling pulse of a constant frequency into N-bit digital signals, and arranging a plurality of sets of the N-bit digital signals in one frame. The first
In a device equipped with PCM transmission device B, a different type of analog signal different from the above analog signal
A control timing pulse generator C that generates a sampling pulse for sampling A ₂₅ with a sampling pulse having a frequency 1.5 times that of the sampling pulse, and a sampling pulse output from the control timing pulse generator. A second PCM transmission device D that samples the different types of analog signals and converts and outputs one sample value into a [4/3×N] bit digital signal, and sequentially stores the output signals of the second PCM transmission device. and a buffer memory device E that outputs the stored digital signal at a rate of [4/3×N]×1.5 bits per frame in synchronization with a delimiter identification signal obtained by dividing the sampling pulse of a constant frequency; The output signal is
A PCM transmission device characterized by comprising: means for combining with and outputting an output signal of the PCM transmission device. However, the symbol [ ] is a Gaussian symbol and represents the largest integer value that does not exceed the numbers enclosed by this symbol. 2. In the PCM transmission device according to claim 1, 1.5 times the [4/3×N] bits is selected to be smaller than 2N, and the combining and outputting means is the delimiter identification signal. What is claimed is: 1. A PCM transmission device characterized in that the PCM transmission device is configured to combine an output signal with an output signal and send it out onto a transmission path.