JP2000174643A - Digital radio receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To output only the reception signals of high quality in a reception environment where interference waves are present or it is required to receive the signals of a low reception level. SOLUTION: An RF front end 1 outputs RSSI (reception strength) signals for indicating the strength of received signals, a unique word detection part 3 outputs UW signals for indicating whether or not the received signals are synchronized and an error correction part 4 outputs BE signals for indicating that an error bit is detected in received digital signals. The BE signals are counted for prescribed time T in a counter 62, the counted value is divided by the total number of bits during the time T in a division circuit 63 and BER signals for indicating an error rate are obtained. A judgement circuit 68 controls a muting circuit 5 so as not to perform a muting operation in the case that the RSSI signals are equal to or above a reference level RFRSSI, the UW signals indicate that synchronization is obtained and the BER signals are equal to or below the reference level RFBER.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver in a digital radio communication system, and more particularly, to a digital radio receiver capable of outputting a signal with a quality set according to a use condition or the like.

[0002]

2. Description of the Related Art With the recent development of communication technology, digital radio communication systems such as portable telephone systems and PHSs (Personal Handy Phone Systems) have become extremely widespread. In such a digital wireless communication system, a transmitter digitally encodes an audio signal, performs error correction encoding, digitally modulates a high frequency signal with the obtained digital signal, and transmits the digital signal from an antenna. On the other hand, the receiver detects the reception strength (RSSI) of the high-frequency signal arriving at the antenna,
Unique word (UW: sync word) detection and CRC
(Guard bit) error check code to detect an error, and the RSSI of a received high-frequency signal
The output signal is muted when the level is lowered or when an error is detected in the demodulated digital signal.

FIG. 2 is a block circuit diagram of a conventional digital radio receiver. In the figure, reference numeral 1 denotes a receiving antenna, 2 denotes an RF receiving unit, and a predetermined number of signals from the receiving antenna 1 are used. In order to receive the high-frequency signal existing in the band and demodulate it into a digital signal, a high-frequency band filter,
It includes a high-frequency amplifier, a mixer, a local oscillator (OSC), and the like. The RF receiver 2 also includes an RSSI circuit for detecting the received signal strength RSSI. Reference numeral 3 denotes a unique word (UW) detection unit, and reference numeral 4 denotes an error correction unit including an error detection circuit. The unique word detection unit 3 detects a unique word added to the digital signal for synchronization, and supplies a frame sample signal to the error correction unit 4 when the unique word is correctly detected. At the same time, it outputs a UW signal indicating whether or not it has been correctly detected. 5 is a muting unit, 6 is a muting control unit for controlling on / off of the muting unit 5,
Muting control unit 6 receives RSS from RF receiving unit 2
Determining whether to mute the audio signal based on the I signal, the UW signal from the unique word detection unit 3 and the BE signal indicating whether or not a bit error from the error correction block 4 has been detected; The muting section 5 outputs a muting control signal Sc to the muting section 5. Reference numeral 7 denotes an audio decoding unit, and reference numeral 8 denotes a speaker.

In the conventional digital radio receiver shown in FIG. 2, when the received signal strength RSSI decreases or an error is detected, the audio signal is muted. It is configured to be. By the way, depending on the degree of error included in the digital signal, there is a case where almost no problem occurs in the sense of hearing.
In the conventional example, even if the hearing is not hindered, the output is muted in any case where the received signal contains an error. That is, since the conventional example does not include means for detecting the degree of error, it is not possible to control the output of the audio signal depending on whether the degree of error is within an allowable range. The present invention has been made in view of such a problem of the conventional example, and its purpose is to reliably mute a received signal carried through a poor transmission path in a digital wireless receiver, Even if the received signal contains an error, it can be output without muting depending on the degree of the error.

[0005]

In order to achieve the above-mentioned object of the present invention, a digital radio receiver according to the present invention comprises a receiving strength detecting means for providing an RSSI signal indicating the receiving strength of a received signal; Synchronization detection means for providing a UW signal indicating whether or not synchronization is achieved based on a unique word included in the received signal; error rate detection means for providing a BER signal indicating an error rate of the received digital signal; Muting means for muting the output of the digital radio receiver, RSSI signal, UW signal and BER signal are input, and it is determined whether or not the received digital signal is degraded based on these signals. Muting control means for controlling muting means so that the output of the receiver is muted when it is determined that It is characterized in that it comprises.

In a preferred embodiment of the present invention, the muting control means indicates that the UW signal is synchronized, the RSSI signal is above a predetermined reference level, and the BER signal is a predetermined reference level. When the level is equal to or lower than the level, the digital signal is determined not to be degraded. Further, the error rate detecting means includes:
Means for counting the number of error bits detected by the error detection means of the digital radio receiver for a predetermined fixed time; and counting the number of error bits counted by the total number of bits taken into the error detection means during the fixed time. BE representing the error rate by dividing
Means for providing an R signal.

[0007]

FIG. 1 is a block diagram of a digital radio receiver according to an embodiment of the present invention. In FIG. 1, the same or similar components as those in the conventional example shown in FIG. The same reference numerals are assigned. In the present invention, in comparison with the conventional example of FIG. 2, the muting control unit 6 includes a measurement time setting circuit (T) 61 and a counter for detecting whether the error rate (BER) is within an allowable range. 62,
Division circuit 63, reference level setting circuit 64, and comparator 6
5 is one of the features. In FIG. 1, the comparator 65 is a digital comparator, and the reference level setting circuit 64 also outputs a digital value. When an analog comparator is used as the comparator 65, a converter for performing D / A conversion of the output from the division circuit 63 is provided, and a DC voltage corresponding to the set value is generated from the reference level setting circuit 64; Needless to say, such modifications are required.

The reference level setting circuit 66 and the comparator 67 are also provided in the conventional example (omitted in FIG. 2), and the comparator 67 includes the RSSI signal from the RF receiver 2 and the reference level RF _RSSI . And outputs a high level (H) when the RSSI is equal to or higher than the reference level, and outputs a low level (L) otherwise. Needless to say, the reference level setting circuit 66 and the comparator 67 can be realized by either an analog circuit or a digital circuit. The present invention is further characterized in that the judgment circuit 68 evaluates and judges the state of the transmission path based on the signals from the comparators 65 and 67 and the UW signal from the unique word detection unit 3.

Next, the operation for detecting whether the error rate (BER) of the received digital signal, that is, the degree of error, is within an allowable range will be described. In the present invention, B which needs error detection for error correction
The CH code is used, and the error correction unit 4 detects an error bit and performs error correction every time a frame sample signal is supplied from the unique word detection unit 3. Each time the error correction unit 4 fetches each bit and detects an error bit, the error correction unit 4 outputs B indicating that the error bit has been detected.
E signal is output and the counter 6 of the muting control unit 6
Feed to 2.

The counter 62 counts the number of supplied BE signals and supplies the counted signal to the dividing circuit 63. At a clear terminal of the counter 62, the predetermined time T set by the measuring time setting circuit 61 is up. Each time a clear signal is supplied, the counter 62 is cleared. In addition, the total number of bits taken into the error correction unit 4 during the T time is previously stored in the division circuit 63, and the division circuit 63 sets the time when the measurement time setting circuit 61 outputs the time-up signal. , Using the count value of the counter 62 as a numerator and a preset total number of bits as a denominator, and dividing the value, that is, a BER signal representing an error rate, into a comparator
5 Instead of presetting the total number of bits to be taken into the error correction unit 4 during the T time, the division circuit 63 is provided with a counter for detecting the total number of bits, and the counted value is supplied to the division circuit 63. May be. The comparator 65 compares the BER signal with the reference level RF _BER set in the reference level setting circuit 64, and supplies a high level output to the determination circuit 68 when the BER signal is equal to or lower than the reference level RF _BER . The reference level RF _BER is set according to the use situation, but is set low when importance is placed on the quality of the signal, and is set high when the situation allows some deterioration.

The comparator 67 receives the RSS from the RY receiver 2.
Compared with the I signal and the reference level RF _RSSI set in the reference level setting circuit 66, the high level is output to the determination circuit 68 when the RSSI signal is high, and the low level is output when the RSSI signal is low. The reference level RF _RSSI is set high when the area of use is relatively small and it is necessary to reduce the influence of interference from other _sources. Is set low.

As shown in Table 1 below, the determination circuit 68 determines whether the UW signal from the unique word detector 3 and the output signals from the comparators 65 and 67 are high (H) or low (L). , The state of the transmission path, that is, the quality of the received digital signal is determined. In Table 1, X indicating the input state includes both the cases of H and L, and indicates that the determination of the output state is not affected. MUTE indicating the output state indicates a muting state, and OUT indicates a signal output state.

Table 1 Table 1 UW signal HL HH Output of comparator 65 HXL H Output of comparator 67 HXXL audio signal OUT MUTE MUTE MUTE

As apparent from Table 1, the UW signal indicates that synchronization is achieved, the BER signal indicates that the error rate is below the reference level, and the RSSI signal indicates that the received signal strength is above the reference level. , The signal is decoded without muting, and muted otherwise. The above criteria are as follows. (1) If the UW signal is at a low level and indicates that synchronization has not been achieved, frame synchronization is not reliably performed, so that the reliability of error correction and error rate BER detection both decreases, and the digital signal Cannot guarantee the quality of
The output is muted regardless of the state of the SSI signal and the BER signal. (2) If the error rate is high even when synchronization is established,
Since this indicates that the influence of an interference wave or the like is large, the quality of the digital signal is low, and the output is muted regardless of the state of the RSSI signal. (3) Even if the synchronization is achieved and the error rate is acceptable, if the RSSI signal is at a low level, the reception level may be automatically limited due to reception of an interference wave or the like. Yes, so also muting the output. The evaluation of the quality of the digital signal in the muting control unit 6 can be realized by computer software.

Since the present invention is configured as described above, it is possible to set whether or not to output a received digital signal in accordance with a use situation. Further, in a reception environment in which an interfering wave is present or a signal having a low reception level must be received, only a high-quality reception signal can be output.

[Brief description of the drawings]

FIG. 1 is a block diagram of a digital wireless receiver according to one embodiment of the present invention.

FIG. 2 is a block diagram of a conventional digital wireless receiver.

Claims (3)

[Claims] 1. A digital radio receiver, comprising: a reception strength detection means for providing an RSSI signal indicating the reception strength of a received signal; and indicating whether or not synchronization is achieved based on a unique word included in the received signal. Synchronization detection means for providing a UW signal; error rate detection means for providing a BER signal indicating an error rate of a received digital signal; muting means for muting an output of a digital radio receiver; RSSI signal; And a BER signal, and determine whether or not the received digital signal is degraded based on these signals, and when it is determined that the digital signal is degraded, muting means so that the output of the receiver is muted And a muting control means for controlling the operation of the digital radio receiver. 2. The digital radio receiver according to claim 1, wherein the muting control means indicates that the UW signal is synchronized, the RSSI signal is higher than a predetermined reference level, and the BER signal is higher. A digital wireless device configured to determine that there is no deterioration of a digital signal when the level is equal to or lower than a predetermined reference level. 3. The digital wireless receiver according to claim 2, wherein the error rate detecting means counts the number of error bits detected by the error detecting means of the digital wireless receiver for a predetermined period of time; Means for providing the BER signal indicating the error rate by dividing the set number of error bits by the total number of bits taken into the error detection means during the predetermined time.