JPH0799521A - Burst signal detection circuit - Google Patents

Abstract

PURPOSE:To reduce mis-detection by simply forming the burst detection circuit employing a digital circuit by using phase information so as to detect a burst signal. CONSTITUTION:A base band signal separated into I and Q channels at an orthogonal detection circuit is inputted to a ROM into which phase information is written, and a reception modulation wave phase signal from the ROM is inputted to difference circuits 10-1, 10-2. Then outputs are inputted to an adder circuit 40 and a delay circuit 30, their outputs are added and the sum is given to an absolute value circuit 50, the absolute value obtained therefrom is inputted to an accumulation circuit 60, in which the accumulation value over a predetermined time is fed to a comparator circuit 70. When the value given to the comparator circuit 70 is less than a set allowable limit or below, the circuit 70 outputs a burst detection signal. A burst is detected by using phase information in this way, then no adjustment, low power consumption and miniaturization are more facilitated in comparison with the detection of a burst signal by an analog circuit and mis-detection due to a mixed signal such as interference noise is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burst signal detection circuit in digital radio communication.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a conventional burst signal detection circuit. The conventional detection of a burst signal is generally performed by a reception electric field strength detector (Received S) which receives a reception wave intermediate frequency (IF) signal from which noise other than a desired frequency band is removed by a bandpass filter or the like.
Signal Strength Indicator:
RSSI) 80. The received electric field strength detector 80 outputs the electric field strength of the input signal as an analog signal. A comparison circuit 90, which receives the output of the received electric field intensity detector, compares the magnitude with a certain threshold value, and outputs a burst detection signal assuming that a burst signal is detected when the magnitude is larger than the threshold value.

[0003]

The received electric field strength detector used in the prior art is an analog element, and other comparison circuits and the like also have a circuit configuration using an analog circuit or an analog-digital conversion circuit, which is downsized and has no adjustment. It is disadvantageous in terms of conversion. Further, since the conventional method using the received electric field intensity detector detects the burst signal using the amplitude information of the received modulated wave, a mixed signal such as interference noise may be erroneously detected. Furthermore, this method cannot be used after passing through an element such as a limiter that is often used in a mobile communication receiver and that lacks amplitude information.

It is an object of the present invention to provide a burst signal detection circuit which detects a burst signal by using phase information of a received modulated wave.

[0005]

A feature of the present invention for achieving the above object is that a phase-modulated signal including a specific pattern is input, and the difference from the signal delayed by one symbol time is K times (K is 1). K number of difference circuits to perform the above natural number)
An adder circuit for adding the output of the delay circuit for delaying the output by one symbol time and the output of the K-time difference circuit;
An absolute value circuit that takes the absolute value of the output of the adder circuit, a cumulative adder circuit that cumulatively adds the output for a fixed time, and a burst signal detection signal when the output of the cumulative adder circuit is smaller than a predetermined allowable value. And a burst signal detection circuit having a comparison circuit for

[0006]

According to the present invention, burst detection is performed using phase information instead of using amplitude information as in the prior art. Therefore, the present invention can be applied to a signal that has passed through an element such as a limiter that is often used in a mobile communication receiver and that lacks amplitude information, and the burst detection circuit can be easily provided by a digital circuit in the baseband. It becomes feasible.
Moreover, since amplitude information is not used, the probability of erroneously detecting a mixed signal such as interference noise is reduced.

[0007]

FIG. 1 is a diagram showing an embodiment of the present invention. The present invention can be applied to the case where the K times difference signal of the received wave phase signal becomes a periodic signal like a sine function. here,
Using the burst format shown in FIG. 2,
Further, a case where a π / 4-shift QPSK modulation method is used as a modulation method will be described as an example.

A received modulated wave phase signal is input to the burst signal detection circuit of the present invention. The received modulation wave phase signal is obtained by, for example, phase information (arcta) of a baseband signal separated into I channel and Q channel by a quadrature detection circuit.
It can be easily obtained by inputting to the ROM in which n (I / Q)) is written. The received modulated wave phase signal is input to a K times difference circuit (K = 2 in this case). FIG. 3 shows a signal obtained by subtracting the received modulated wave phase signal twice in the preamble portion of the burst format shown in FIG. 2 in the present embodiment. The difference number K is selected in consideration of the transmission preamble pattern and the modulation method so that the K-time difference signal becomes a periodic signal as shown in FIG. For example, including a pattern with a preamble of "1001" (π /
4) In the case of QPSK modulation, K = 2 is suitable. In many cases, the value of K will be 2 or 3 or less.

Next, the output of the two-time difference circuit is input to the adder circuit 40 and, at the same time, is input to the delay circuit (1 symbol time delay) 30. In the adder circuit 40, the output of the two-time difference circuit and the output of the delay circuit are added (as can be seen from FIG. 3, the output value of the adder circuit is zero when there is no noise) and is input to the absolute value circuit 50. It The absolute value circuit 50 takes the absolute value of the added value and inputs it to the cumulative addition circuit 60. The cumulative addition circuit 60 obtains a cumulative addition value over a certain fixed time. The output of the cumulative addition circuit is input to the comparison circuit 70, and if it is equal to or less than the set allowable value, a burst detection signal is output.

[0010]

According to the present invention, burst detection is performed using phase information instead of using amplitude information as in the prior art. Therefore, the present invention can be applied to a signal that has passed through an element such as a limiter that is often used in a mobile communication receiver and that lacks amplitude information, and the burst detection circuit can be easily provided by a digital circuit in a baseband or the like. It becomes feasible. Therefore, as compared with the conventional burst signal detector using the analog circuit, it is advantageous in terms of no adjustment, low power consumption, and miniaturization. Also, the probability of erroneously detecting a mixed signal such as interference noise is reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a burst format.

FIG. 3 is a diagram showing a two-time difference signal.

FIG. 4 is a diagram showing a conventional example.

[Explanation of symbols]

 10-1, 10-2 Difference circuit 20 Subtraction circuit 30 Delay circuit (1 symbol time) 40 Addition circuit 50 Absolute value circuit 60 Cumulative addition circuit 70, 90 Comparison circuit 80 Received field strength detector

Claims (1)

[Claims] 1. A phase-modulated signal including a specific pattern is input, and the difference from the signal delayed by one symbol time is K.
Number of times (K is a natural number of 1 or more), an adder circuit that adds the output of the delay circuit that delays the output by one symbol time, and the output of the K-time difference circuit, and the output of the adder circuit An absolute value circuit that takes an absolute value of, a cumulative addition circuit that cumulatively adds the outputs for a certain period of time, and a comparison circuit that outputs a burst signal detection signal when the output of the cumulative addition circuit is smaller than a predetermined allowable value. A burst signal detection circuit having.