JP3223402B2 - Burst signal detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

[0003]

The receiving electric field strength detector used in the prior art is an analog element, and the other comparing circuits and the like also have a circuit configuration using an analog circuit or an analog-to-digital conversion circuit, so that they can be reduced in size and adjusted without adjustment. It is disadvantageous in terms of conversion. Further, in the conventional method using the reception electric field strength detector, since a burst signal is detected using amplitude information of a reception modulation wave, a mixed signal such as interference noise may be erroneously detected. Furthermore, this method cannot be used after passing through an element that lacks amplitude information such as a limiter often used in a mobile communication receiver.

An object of the present invention is to provide a burst signal detection circuit for detecting a burst signal using phase information of a received modulated wave.

[0005]

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

[0006]

According to the present invention, burst detection is performed by using phase information instead of using amplitude information as in the prior art. Therefore, the present invention can be applied to a signal after passing through an element that lacks amplitude information, such as a limiter, which is often used in a mobile communication receiver, and the burst detection circuit can be simplified by a digital circuit in the baseband band. It becomes feasible.
Further, since the 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 a case where the K-time difference signal of the received wave phase signal is a periodic signal such as 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.

[0008] A received modulated wave phase signal is input to the burst signal detection circuit of the present invention. The received modulated wave phase signal is obtained, for example, by converting a baseband signal separated into an I channel and a Q channel by a quadrature detection circuit into phase information (arcta).
n (I / Q)) can be easily obtained by inputting it into the ROM in which it is written. The received modulated wave phase signal is input to a K-th difference circuit (here, K = 2). FIG. 3 shows a signal obtained by twice differentiating the received modulated wave phase signal in the preamble portion of the burst format shown in FIG. 2 in this embodiment. The number of times of difference K is selected in consideration of the transmission preamble pattern and the modulation scheme so that the K-time difference signal becomes a periodic signal as shown in FIG. For example, the preamble includes a pattern of “1001” (π /
4) For QPSK modulation, K = 2 is appropriate. 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 an adder circuit 40, while being input to a delay circuit (one 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 becomes zero when there is no noise) and is input to the absolute value circuit 50. You. The absolute value circuit 50 takes the absolute value of the added value and inputs the absolute value to the cumulative addition circuit 60. The cumulative addition circuit 60 calculates a cumulative addition value over a certain period of time. The output of the accumulating circuit is input to a comparing circuit 70, and if it is equal to or less than a set allowable value, a burst detecting 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 after passing through an element that lacks amplitude information, such as a limiter, which is often used in a mobile communication receiver, and the burst detection circuit can be simplified by a digital circuit in baseband or the like. It becomes feasible. Therefore, it is advantageous in non-adjustment, low power consumption, and miniaturization as compared with a burst signal detector using a conventional analog circuit. Further, the probability of erroneously detecting a mixed signal such as interference noise is reduced.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram showing a differential signal twice.

FIG. 4 is a diagram showing a conventional example.

[Explanation of symbols]

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

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-110611 (JP, A) JP-A-6-252965 (JP, A) JP-A-4-68841 (JP, A) 205062 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04L 27/00-27/38

Claims (1)

(57) [Claims] 1. A phase modulation signal including a specific pattern is input, and a difference from a signal delayed by one symbol time is represented by K
A K-time difference circuit for performing the number of times (K is a natural number of 1 or more), an addition circuit for adding the output of the delay circuit for delaying its output by one symbol time, and the output of the K-time difference circuit; An absolute value circuit that takes an absolute value of the following, a cumulative addition circuit that cumulatively adds the output of the absolute value circuit 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, comprising: