JPH05276202A - Pseudo noise generator for digital modulation - Google Patents

Abstract

PURPOSE:To generate a continuous pseudo noise capable of saving required memory size by generating a signal which simulates an input pseudo noise. CONSTITUTION:A data string P0 of 0 and 1 is inputted from an external pseudo noise generator 1. A 'pseudo' pseudo noise generator 2 generates a signal which simulates the input pseudo signal forming a continuous sequence by adding two bits so as to set the numeric value '0' which comprises the pseudo noise or the number of '0's equal after connecting two pieces of input pseudo data. IQ data conversion for pi/4-shift QPSK modulation is performed on the signal at an IQ conversion/digital filter processing circuit 3, and after digital filtering processing is applied to the signal, an I signal is written on waveform memory A4, and a Q signal on waveform memory B5 by a write address from a generator 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a π / 4 shift QPSK (Quadra Phase Shift) used in a digital mobile phone.
Keying) Pseudo noise generator for digital modulation that generates continuous waveform pseudo noise required for IQ signal generator in keying system, especially pseudo noise generation for digital modulation in which the number of bits of waveform memory for storing pseudo noise is reduced Regarding vessels.

[0002]

2. Description of the Related Art A .pi. / 4 shift QPSK modulation is used as a modulation system in a digital car telephone. This is 2
A symbol consisting of bits is extracted from the orthogonal axes (I axis and Q axis) by
This is a method of using an IQ signal in which digital data is modulated so as to be placed in four phase positions shifted by / 4. Conventionally, there are roughly two types of methods for generating pseudo noise for generating this IQ signal. One is a method of modulating digital data in real time to generate an IQ signal by combining DSP technology and memory capable of operating in real time, and the other method is a digital filter processing that is largely off-line (non-real time) processing. It has a configuration in which it is stored in a capacity memory and is sequentially read from the memory when an IQ signal is generated.

An example of the former is the method proposed by Hewlett-Packard Company. This is "Testing North Amer
ican Dual Mode Cellular, Japan Digital Cellular Tr
ansceivers ”. Since the general method among them requires a large amount of memory, the improved method requires I
The required memory size is reduced by using a ROM having a trigonometric function table instead of the ROM for storing the Q signal.

[0004]

By the way, in the latter method, the real-time property is sacrificed, but there is an advantage that the hardware configuration at the time of occurrence becomes simple by using a large-capacity memory. There is an unavoidable need for large amounts of memory. In other words, this method requires a memory that is eight times as large as the memory length that corresponds to the data length that is input when a continuous wave of pseudo noise is generated, and the advantage that the hardware is simple compared to the former example is alive. Disappear.

The reason why the size of the waveform memory becomes eight times when a continuous wave of normal pseudo noise is generated will be described below. As a premise of the description, 511-bit pseudo noise, which is pseudo noise for digital car telephones, will be described as an example. As the 511-bit pseudo noise, an M series made up of nine flip-flops and an exclusive OR circuit is used, and the number of bits in this M series is 2 ⁹ −1 = 5.
Eleven.

This M sequence is an I symbol of 1 symbol for every 2 bits.
In order to convert into Q data, the data string is repeated twice and the number of data points is an even number of 1022 points. This data string is converted into IQ data according to the π / 4 shift QPSK modulation method.

Since the starting point and the ending point of the resulting data sequence are deviated by π / 8 and they are not continuous, discontinuity occurs when they are looped to generate a continuous wave. Therefore, in order to make the start point and the end point continuous, the input data is repeatedly used eight times. (102 when waveform is generated
If the two symbols are looped as they are, two bits of the first data in the M sequence will change because the phase of the start point and the last phase of the waveform are different. For example, when the head data is "00", it changes to "01".

From the above, the number of bits and memory size required to generate 511-bit continuous pseudo noise are given by the following equation. 511 × 2 × 8 = 8176 bits = 4088 symbols This constraint is based on the standardized pseudo-noise data sequence of π / 4.
This is caused by discontinuity between the start point and the end point of the IQ data after conversion when the shift QPSK / IQ conversion is performed.

The present invention has been made in view of the above points, and an object thereof is to generate a pseudo noise that generates a continuous pseudo noise in which a required memory size is reduced when a continuous pseudo noise in which a memory size is required is generated. Is to realize the vessel.

[0010]

According to the present invention for solving the above-mentioned problems, a pseudo noise signal inputted from the outside is converted into an I signal and a Q signal.
An IQ conversion / digital filter processing circuit for separating into a signal and performing a filtering process, a first waveform memory for an I signal, a second waveform memory for a Q signal, and an I signal in the first waveform memory, In a pseudo noise generator for digital modulation, which comprises an address generator that generates a write address for writing a Q signal in the second waveform memory,
After the input pseudo noise data is connected twice, two consecutive bits are formed by adding two bits so that the numbers of the bits constituting the pseudo noise are equal to "0" or "1". It is characterized by comprising a "pseudo" pseudo noise generator for generating a signal simulating the input pseudo noise.

[0011]

The "pseudo" pseudo noise generator connects the input pseudo noise twice, and then, the two bits "0" or "1" are equalized so that the numbers of "0" and "1" in the sequence are equal. 1 "is added to generate and output" pseudo "pseudo noise that simulates pseudo noise forming a continuous sequence. The IQ conversion / digital filtering processing circuit modulates and filters this pseudo noise into an IQ signal, and then stores the I signal in the first waveform memory and the Q signal in the second waveform memory.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 is a pseudo noise generator that externally supplies the original regular pseudo noise to the apparatus of this embodiment. As for the pseudo noise generated by the pseudo noise generator 1, a 511-bit data string of "0" and "1" is used in the digital car telephone standard, and this data string is designated as P ₀ .

2 is π / 4 based on this P ₀ data string.
It is a "pseudo" pseudo noise generator that generates "pseudo" pseudo noise P ₁ that does not increase the required waveform memory size even if the IQ signal for the shift QPSK modulation signal is generated.

Reference numeral 3 is an IQ conversion that performs noise data generated by the "pseudo" pseudo noise generator 2 after IQ data conversion for π / 4 shift QPSK modulation, and then performs digital filtering processing for removing unnecessary noise. / A digital filtering processing circuit.

The "pseudo" pseudo noise generator 2 and the IQ conversion / digital filtering processing circuit 3 are non-real time processing circuits. Reference numeral 4 is a waveform memory A for storing an I signal of "pseudo" pseudo noise converted into an IQ signal, and 5 is a waveform memory B for storing a Q signal. The write address to the waveform memory A4 and the waveform memory B5 is output from the address generator 6.

Next, the operation of the embodiment configured as described above will be described. First, the external pseudo noise generators 1 to 51
A 1-bit “0”, “1” data string P ₀ is input.
The "pseudo" pseudo noise generator 2 is "pseudo" in the following procedure.
Pseudo noise P ₁ is generated. Double the number of bits by connecting P ₀ twice. P ₀ is 51
If it is 1 bit, it will be 1022 bits. 2-bit "0" or "1" is added to the created data string. This is because when "1" is one more than "0" in the 511-bit data string, "0" is added, and "0" is "1".
If there are more, add "1". Since this data sequence P ₀ is a sequence in which the number of “0” or “1” is different by 1, the number sequence in which P ₀ is simply connected twice produces two differences. Therefore, by adding "0" or "1" in this way, "0" and "1" become the same number. The resulting data string is 1024 bits. The obtained 1024-bit data string P ₁ is used as “pseudo” pseudo noise.

The "pseudo" pseudo noise thus created is subjected to IQ data conversion for .pi. / 4 shift QPSK modulation in the IQ conversion / digital filter processing circuit 3 and subjected to digital filtering processing, followed by addressing. According to the write address from the generator 6, the I signal is written in the waveform memory A4 and the Q signal is written in the waveform memory B5. These signals are read and output to the DA converter.

As described above, according to this embodiment, a π / 4 shift Q which is a modulation system for a digital car telephone or the like is used.
In the PSK modulation method, continuous generation of pseudo noise can be realized with a small memory (1/8 of the regular size) and a simple circuit configuration.

In the above embodiment, the pseudo noise is not limited to the M series data, and other series data suitable for the purpose may be used.

[0020]

As described in detail above, according to the present invention, the pseudo noise data used for the π / 4 QPSK modulation can be made into the pseudo noise which can reduce the size of the memory to be stored, and can be put to practical use. The above effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 2 “Pseudo” pseudo noise generator 3 IQ conversion / digital filtering processing circuit 4, 5 Waveform memory 6 Address generator

Claims (1)

[Claims] 1. An IQ conversion / digital filter processing circuit (3) for separating a pseudo noise signal input from the outside into an I signal and a Q signal and performing a filtering process, and a first waveform memory (4) for the I signal. ) And a second waveform memory for the Q signal (5)
And the I signal to the first waveform memory (4) and the second signal to the second waveform memory (4).
In the pseudo noise generator for digital modulation, which is composed of the address generator (6) for generating the write address for writing the Q signal in the waveform memory (5) of FIG. Further, a signal simulating the input pseudo noise which forms a continuous number sequence by adding two bits so that the number of "0" or "1" of the bits constituting the pseudo noise becomes equal is generated. Pseudo noise generator for digital modulation, characterized in that it comprises a "pseudo" pseudo noise generator (2).