JPH0316451A - Burst detector - Google Patents

Abstract

PURPOSE:To detect the arrival of a burst signal by multiplying 1 and -1 with an input data in the unit of N samples for each modulation period, extracting two sample data points of the modulation period and separating the data into an odd number sample group data and an even number sample group data. CONSTITUTION:A burst APSK modulation signal is subjected to frequency conversion to a base band with an oscillator of a fixed frequency and becomes 2-channel analog signals orthogonal to each other. An A/D converter 1 samples each signal with a high speed clock at a multiple of N of the modulation clock and each sampling value is converted into a digital time series data comprising of quantizing bits. An inverse modulation means 2 multiples 1 and -1 with the input data alternately in the unit of N samples for each modulation period. A sampler 3 extracts two sample data of 1/2 modulation period from the N- sample data for each modulation period and separates from into an odd number sample group data and an even number sample group data. A comparison means 16 compares an output of a 3rd envelope detection means 10 with a detected threshold level and discriminates it to be the detection of a burst signal when the output exceeds the threshold level.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to the use of a TDMA packet communication system or a digital signal system that handles burst voice or data signals.
Odd sample series data and even sample series data are required to detect the arrival of a burst signal, and the present invention relates to a burst signal demodulation device that effectively detects the burst signal.

(Prior Art) Conventionally, a phase locked loop (PLL) has been widely used as a means for demodulating a burst APSK modulated signal. In this case, it is necessary to regenerate the carrier phase for each burst in a short time, and in order to shorten this synchronization time,
It is common to add an unmodulated signal as a preamble to the beginning of each burst. Further, in order to obtain a predetermined timing for starting the PLL control flow when a burst arrives, means for detecting the arrival of a burst signal from an unmodulated signal is required. The conventional perspective detection device is used as a second
The operation thereof will be briefly explained below with reference to the drawings. In this specification, thick lines in the figures indicate orthogonal signals (complex signals), and thin lines indicate real signals.

Parsing in which an unmodulated signal is added as a preamble to the beginning of data} The APSK modulated signal is once frequency-converted to the base band by an oscillator with a fixed frequency, and becomes an analog signal of two orthogonal channels.

Each bit is sampled by an analog/digital (A/D) converter 12 using a clock that is N times the modulation clock (an integer where N>0), and each sampling bit is converted into a digital signal consisting of n (an integer where n>O). Converted to time series data. After the S/N of the output is improved by the first low-pass filter 13, the absolute value is calculated by the envelope detection means 14. Assuming that the orthogonal components of the signal manually input to the envelope detection means 14 are represented by {circle around (1)} and Q, respectively, the envelope p is calculated by the following equation.

p=≠waJ(1) Furthermore, calculation of the square root of equation (1) is difficult to actually realize, and the power p is usually evaluated as a detected value. Alternatively, the following equation is also often used as an approximation of equation (1).

p = tII +IQI/2 (I≧Q)+
I+/2 + IQI (I < Q)
(2) The envelope value detected in this way is input to the second low-pass filter 15, and signal dispersion is improved. The output is compared with a detection threshold by the comparison means 16, and when it exceeds the detection threshold, it is determined that a burst signal has been detected.

(Problem to be solved by the invention) The above is an overview of the conventional burst detection device.

The burst signal that can be detected by this device is one in which a preamble of an unmodulated signal is added to the beginning of the data, and it does not perform the detection function for signals with some kind of modulation, such as 0■ modulation signals. .

Furthermore, recently, a demodulator has been proposed that does not require an unmodulated signal and uses On modulation for carrier synchronization of a part-like APSK modulated signal. Therefore, a means for detecting the arrival of a burst signal in which only the 0n modulation signal is added to the beginning of the data as a preamble has become necessary. SUMMARY OF THE INVENTION An object of the present invention is to provide a burst detection device that detects a burst signal from a preamble of an 0n modulated signal.

(Means for Solving the Problems) The burst detection device of the present invention uses a fixed frequency oscillator to generate a burst amplitude phase shift (APSK) modulated signal in which an 0n modulated signal is added as a preamble to the head of data, into a base band. Receive frequency-converted two-channel orthogonal analog signals, sample each using a high-speed clock that is N times the modulation clock (an integer where N>0), and convert each sample value into quantization bits}n (where n>0). An analog-to-digital (A/D) converter converts the input data into digital time-series data consisting of integers); an inverse modulation means for multiplying the data alternately; a sampler for receiving the output of the inverse modulation means, extracting two points of modulation period sample data, and distributing the output into odd numbered sample series data and even numbered sample series data; The output odd sample series data and even sample series data are respectively processed into first and second signals for improving the signal-to-noise power ratio (S/N).
a low-pass filter; first and second envelope detection means for calculating first and second absolute values of outputs of the first and second low-pass filters; Third and fourth low-pass filters improve the signal dispersion of the first and second envelope detection means, and outputs of the third and fourth low-pass filters are filtered to and a comparison means that receives the output of the envelope detection means and compares it with a detection threshold to detect the arrival of a burst signal.

(Example) Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, thick lines indicate orthogonal signals (or complex signals), and thin lines indicate real signals.

First, a burst APSK modulated signal in which an 0n modulated signal is added as a preamble to the head of data arrives at the burst signal demodulator shown in FIG. This signal is once frequency-converted to the base band by a fixed frequency oscillator and becomes a two-channel analog signal that is orthogonal to each other. The A/D converter 1 outputs each signal by N times the modulation clock (N>0 integer)
sampled using the high-speed clock of
Convert to digital time series data consisting of n (an integer where n>0). In response to the output, the inverse modulation means 2 operates to alternately multiply the signal by 1 and -1 in units of N samples every modulation period. At this point, the bit period has not yet been established, and the timing for switching the multiplier between 1 and -1 every N samples with respect to the input data is uncertain. Upon receiving this output, the sampler 3 extracts two sample data points of 1/2 modulation period from the N sample data of each modulation period, and converts the output into odd sample series data S, (2e-1) (6 = 1 .2
, 3,. ．． ．． ) and even sample series data Sd (2a
(e: 1, 2, 3, ・”).Data Sd (2e-1) and 8,<2e) (7) are input to the first and second low-pass filters 4 and 5, respectively. The absolute value of each output is calculated by the first and second envelope detection means 6 and 7, and then inputted again to the third and fourth low-pass filters 8 and 9. Signal dispersion is improved. Third and fourth low-pass filters 8, 9
The output data of 3, (2e-1) (p = 1.2, 3,
...) and S, C2e) Ce = i, 2, 3, .
...), the third envelope detection means lO calculates the absolute value from the data SdC2e-1) and S, C2e).

Figure 3 shows sample data Sd(2e-1) and S,C2e) for the analog input signal envelope in the absence of noise.
However, each sample timing T2e-1
and T2e are not synchronized with the bit timing, and none of the samples necessarily indicates the highest envelope value. In order to make the envelope detection value maximum and constant,
Paying attention to the fact that the envelope waveform between one symbol of the modulation period is similar to the half-period waveform of a sine wave, sample data S
, (2e-1) and 8, (2e) are mutually orthogonal signals, and by calculating the absolute value, an output similar to the envelope value of the signal point can always be obtained. The comparison means 16 compares the output of the third envelope detection means 10 with a detection threshold, and when the detection threshold is exceeded, it is determined that a burst signal has been detected.

The above is the burst detection device according to the present invention, but it is naturally possible to place the inverse modulation means 2 after the sampler 3 in FIG. 1 and inversely modulate each of the two series of sample data distributed by the sampler 3. is the same as in Figure 1.

(Effects of the Invention) As explained above, the present invention can detect the arrival of a burst signal with a 0n modulation preamble, which was impossible with conventional burst detection devices. It can be expected to have effects such as easy integration into IC and software processing using a digital signal processor (DSP).

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the prior art, and FIG. 3 is a diagram for explaining the operation of the present invention. In the figure, 1...N0 converter, 2...Inverse modulation means, 3...Sampler, 4, 5, 8, 9, 13,
15...Low pass filter, 6, 7, 10, 1
4...Envelope detection means, 11. 16...Comparison means.

Claims (1)

[Claims] A burst amplitude phase shift (APSK) modulation signal with a 0n modulation signal added as a preamble to the beginning of the data is frequency-converted to the baseband using a fixed frequency oscillator.Receives orthogonal two-channel analog signals and modulates each one. Analog/digital (A/D) that samples with a high-speed clock N times the clock (an integer where N>0) and converts each sample value into digital time series data consisting of n quantized bits (an integer where n>0). ) converter, inverse modulation means that receives the output of the A/D converter and alternately multiplies the input data by 1 and -1 in units of N samples every modulation period, and receives the output of the inverse modulation means. , a sampler that extracts two points of modulation period sample data and distributes the output into odd sample series data and even sample series data, and receiving each of the odd sample series data and even sample series data that are outputs of the sampler, first and second low-pass filters that improve the signal-to-noise power ratio (S/N);
and first and second envelope detection means that receive the outputs of each of the second low-pass filters and calculate their absolute values, and receive the outputs of the first and second envelope detection means and calculate the signals thereof. third and fourth low-pass filters for improving dispersion; third envelope detection means for receiving the outputs of the third and fourth low-pass filters and calculating the absolute value thereof; and an output of the envelope detection means. 1. A burst detection device comprising: comparison means for detecting the arrival of a burst signal by comparing it with a detection threshold.