JPH0936843A - Diversity reception circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold satisfactory reception quality and to retrieve an idle channel during communication without hit. SOLUTION: Antennas 1A and 1B, reception demodulation parts 2A and 2B, synthesizers 3A and 3B, a control part 15 and a decoding part 16 are provided. In a regular communication, the same selected frequency signals are outputted from both the synthesizers 3A and 3B. Demodulation output from the reception demodulation part, which is related to a larger received electric field intensity between SA and SB, is given to the decoding part 16. In the case of retrieving the other idle channel or switching the channel, one synthesizer is caused to output the selected frequency signal of the channel in the middle of communication and the other synthesizer is caused to output the selected frequency signal of the channel of a switching destination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity receiving circuit used in mobile communication terminals such as mobile phones, car phones and cordless phones.

[0002]

2. Description of the Related Art Conventionally, in mobile communication, in order to prevent deterioration of reception quality due to fading, a diversity (space) is used in which a plurality of reception systems are received and a reception signal having a better reception quality is selectively switched to be used. Diversity reception technology is widely used. Diversity receiving technology of this switching method has a pre-detection switching diversity method and a post-detection switching diversity method depending on whether the above-mentioned selective switching of the received signal is performed before demodulation or after demodulation, but in digital communication, at the time of switching, Post-detection switching diversity, in which no code error occurs, is more widely used.

FIG. 2 is a block diagram showing a conventional diversity receiving circuit of post-detection switching system. In the figure, reference numerals 1A and 2B denote receiving antennas, and the receiving antennas 1A and 1B have receiving and demodulating units 2 respectively.
A and 2B are connected. The reception demodulators 2A and 2B receive the same transmission signal from the base station via the receiving antenna connected thereto, and demodulate the reception signal based on a local oscillation frequency signal from the synthesizer 3 described later. And a demodulation output, and each reception electric field strength (RSSI) SA and SB are obtained, and these are transmitted.

The synthesizer 3 is a local oscillator that gives a local oscillation frequency signal to the reception demodulators 2A and 2B under the control of the controller 5 described later. The switching switch 4 is a circuit unit which selectively switches and outputs one of the demodulation outputs sent from the reception demodulation units 2A and 2B under the control of the control unit 5. The decoding unit 6 is a circuit unit that restores the demodulation output sent via the switching switch 4 into an information source signal. The control unit 5 controls the synthesizer 3 based on the control signal from the partner station sent from the decoding unit 6 to send out the local oscillation frequency signal related to the channel being used, and the two received electric field strengths SA. And SB are constantly fetched to determine which level is larger, and the demodulation output from the reception demodulation unit that outputs a large reception electric field strength at that time is switched to be sent to the decoding unit 6. This is a circuit unit that switches the switch 4.

The post-detection switching type diversity receiving circuit configured as described above is an extremely excellent circuit as a measure against fading in mobile communication of digital transmission, and is related to an already established technology.

[0006]

By the way, recently, in mobile communication, a mobile station is often equipped with a so-called free channel search function, but it is desirable to be able to search for a free channel even during communication, if possible. That is, when interference with another station occurs during communication on a certain channel, or during handover accompanying movement from the communication area of one base station to the communication area of another base station, the next channel to be switched and used. Is desired to be searched in advance.

However, the conventional mobile station for mobile communication is
Even if the diversity receiving circuit of the post-detection switching system is provided (that is, even if a measure against fading is taken), other vacant signals are received during reception using a certain channel. The channel cannot be searched, and at the time of the handover, the frequency information of a new communication channel is received and the local oscillation frequency signal is switched based on this. Therefore, at the time of this switching, there is a momentary interruption in which the call is interrupted between the reception of the frequency information and the stable transmission of the new local oscillation frequency signal by the synthesizer.

A method for avoiding the above-mentioned instantaneous interruption and searching for an empty channel even during communication is time division multiplexing, that is, TDMA.
(Time Division Multiple
There is an access method. This TDMA
In the system, since the reception is performed intermittently at the time slot assigned to the own station, it is possible to check the idle state of another channel by using the slot period other than the time slot of the own station.

However, even in such a TDMA system, it is necessary to switch the oscillating frequency of the synthesizer at high speed by utilizing the interval between the time slot of the local station and the slot for performing the search. Need to speed up. However, this increase in speed causes a new design problem such as deterioration of the C / N ratio (carrier-to-noise ratio) of the output of the synthesizer.

The present invention has been made in view of the above-mentioned circumstances, and maintains a channel being used for communication without depending on the TDMA method which causes deterioration of the C / N ratio of the output of the synthesizer to be used. It is an object of the present invention to provide a diversity receiving circuit which can check the vacant state of a channel and which is not interrupted when switching channels.

[0011]

According to the invention of claim 1, the diversity receiving circuit is configured as follows. That is, first and second reception demodulators each provided with a receiving antenna, receiving a transmitted signal, demodulating the received signal, transmitting a demodulated output, and obtaining a received electric field strength and outputting the demodulated output. Incorporating first and second synthesizers for outputting local oscillation frequency signals to the first and second reception / demodulation units, respectively, and both demodulation outputs respectively sent from the first and second reception / demodulation units Under the control of a control unit, which will be described later, a switching switch that selectively sends one of the signals, a decoding unit that inputs and decodes the demodulation output sent via the switching switch, And a control unit for inputting the reception field strengths output from the first and second reception demodulation units and the control signal from the partner station output from the decoding unit, and controlling each of the constituent units based on the control signals. During the normal communication, the control unit causes the both synthesizers to output a local oscillation frequency signal of the same frequency related to the channel being used, and outputs a large received electric field strength to the changeover switch. The demodulation output from the reception demodulation unit of the other one is transmitted, and on the other hand, when searching for an empty channel during communication or when switching channels, the one of the first and second synthesizers concerned The selector switch is controlled so that the demodulation output from the reception demodulator that obtains the local oscillation frequency signal from the synthesizer and outputs the local oscillation frequency signal is given to the decoder 6, and the other synthesizer is searched or switched to the channel. It is configured to output the local oscillation frequency signal according to.

According to a second aspect of the present invention, the control section of the diversity receiving circuit according to the first aspect is configured as follows. That is, when an error continuously occurs in the output of the decoding unit for a certain period of time, the search for the empty channel is started.

According to a third aspect of the invention, the control section of the diversity receiving circuit according to the first aspect is configured as follows. That is, when the levels of both the received electric field strengths continuously decrease over a certain period of time, the search for the empty channel is started.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. In addition, in FIG.
2. The circuit section given the same reference numeral as the circuit section in FIG. 2 has the same function as the circuit section in FIG. That is,
In the present embodiment, unlike the conventional example shown in FIG. 2 described above, two synthesizers are provided, and the reception demodulator 2
A synthesizer 3A gives a local oscillation frequency signal to A,
The synthesizer 3B provides a local oscillation frequency signal to the reception demodulator 2B. Then, the control unit 15
Has a configuration in which the two synthesizers can be controlled separately and independently.

Next, the operation of the present embodiment configured as described above will be described. While the mobile station is communicating with the base station, the control unit 15 controls the synthesizers 3A and 3B to output the same local oscillation frequency signal, and the reception demodulation unit 2
The magnitude comparison judgment of the reception electric field strengths SA and SB from A and 2B is always performed, and the demodulation output from the side of the reception demodulation section which is receiving with the large reception electric field strength is input to the decoding section 6. Changeover switch 4 is changed over. In this way, the excellent function of the diversity receiving circuit is exhibited, and deterioration of reception quality due to fading is avoided.

In the case of occurrence of interference with other stations during communication or in the case of handover, a continuous error occurs in the control signal from the decoding unit 6 and the level of both received electric field strengths decreases. However, on the basis of these, the control unit 15 determines that the reception channel needs to be switched. At this time, the control unit 1
5 causes the synthesizer 3A to output a local oscillation frequency signal related to the channel being used for reception,
The changeover switch is controlled so that the demodulation output from the reception demodulation unit 2A is given to the decoding unit 6. That is, it is possible to continue the reception in the reception system including the reception antenna 1A and the reception demodulation unit 2A. At the same time, the synthesizer 3B is caused to output to the reception demodulation unit 2B the local oscillation frequency signal related to the switching destination channel and the channel for checking the idle state.

In this way, the synthesizer 3B which can search for a free channel while holding the currently communicating channel or prepare for switching to another channel and which sets the channel of the switching destination is Since it is already stable at the time of switching, communication failure such as so-called momentary interruption does not occur.

[0018]

As described in detail above, according to the present invention, the channel being used for communication is maintained without relying on the TDMA method which causes the deterioration of the C / N ratio of the output of the synthesizer used. , It is possible to provide a diversity receiving circuit that can check the vacant state of other channels and that is not interrupted when switching channels.

[Brief description of drawings]

FIG. 1 is a block diagram of a diversity receiving circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a conventional diversity receiving circuit.

[Explanation of symbols]

 1A reception antenna 1B reception antenna 2A reception demodulation unit 2B reception demodulation unit 3 synthesizer 3A synthesizer 3B synthesizer SA reception electric field strength SB reception electric field strength 4th switching switch 5 control unit 15 control unit 6 decoding unit

Claims (3)

[Claims] 1. A first and a second reception demodulation section, each of which is provided with a reception antenna, receives a transmitted signal, demodulates the reception signal, sends out a demodulation output, obtains a reception electric field strength and outputs the demodulated output. And first and second synthesizers that output local oscillation frequency signals to the first and second reception and demodulation units, respectively, and both demodulation outputs that are respectively transmitted from the first and second reception and demodulation units. Under the control of the control unit, which will be described later, a switching switch that selectively sends one of the signals, and a decoding unit that inputs and decodes the demodulation output sent via the switching switch, Control for inputting both the reception electric field strengths output from the first and second reception demodulation units and the control signal from the partner station output from the decoding unit, and controlling each component based on them During normal communication, the control unit causes the both synthesizers to output a local oscillation frequency signal of the same frequency related to the channel being used, and causes the changeover switch to generate a large received electric field strength. The demodulation output from the receiving and demodulating section that is outputting is sent out, and on the other hand, when searching for an empty channel during communication or when switching channels, one of the first and second synthesizers is in communication. The selector switch is controlled so as to output the local oscillation frequency signal related to the channel and the demodulation output from the reception demodulation unit that obtains the local oscillation frequency signal from the synthesizer to the decoding unit 6, and causes the other synthesizer to search or switch. A diver configured to output a local oscillation frequency signal related to the previous channel -City receiver circuit. 2. The control unit is configured to start the search for the empty channel when an error continuously occurs in the output of the decoding unit for a certain period of time. The diversity receiving circuit according to claim 1. 3. The control unit, when the levels of both of the reception electric field strengths continuously decrease over a certain period of time,
The diversity receiving circuit according to claim 1, wherein the diversity receiving circuit is configured to start searching for the empty channel.