JPH04223723A - Diversity reception device - Google Patents

Abstract

PURPOSE:To obtain satisfactory communication quality by executing optimum switching even if noise levels in respective antennas differ in a diversity reception device. CONSTITUTION:A digital communication wave received in the antennas 10 and 12 is supplied to demodulators 18 and 20 through frequency converters 14 and 16 and a power value is detected in level detecters 24 and 26. In the packet area of the digital communication wave, a carrier level and the noise level are detected and only the noise level is detected in the gap of packets. The detected noise level is held till the next gap of the packets in sample and hold units 30 and 32 by a control signal from a communication control part 34. CNR is calculated in a switching controller 28 for respective systems and the system of higher CNR is selected. A change-over switch 22 is changed over and the demodulation output of high CNR is always outputted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity receiving apparatus, and more particularly to a diversity receiving apparatus for digital mobile communications that calculates the CNR of a plurality of received waves and selects a received wave.

0002

BACKGROUND OF THE INVENTION In recent years, digital communication, which has advantages such as increased demand for digital data communication and increased capacity, has been studied in automobile telephones and the like. 42kbps, 3-channel multiplexed TDMA (time domain multiple access) using π/4 shift QPSK, aiming for 1992
The introduction of an automated telephone system is also being considered.

[0003] In mobile communications such as car telephones, ensuring communication quality is an important issue, regardless of whether it is analog or digital. For example, when a car equipped with a mobile communication device drives through a city, reflection, scattering, and diffraction from buildings and other structures can cause multiple propagation, causing fading of received signals and significantly deteriorating communication quality. I end up.

[0004] As a method for obtaining good communication quality in response to such problems, there is a diversity reception system.

[0005] Here, the diversity receiving system is a receiving system that is equipped with a plurality of receiving antennas and selects and outputs a signal received by one of the receiving antennas. This selection is performed, for example, depending on the level of the reception level. That is, since signals are generally received by a plurality of receiving antennas through different multiplex propagation paths, the reception level differs for each receiving antenna. Since it can be considered that the higher the reception level is, the better the signal related to transmission can be reproduced, the reception signal related to the reception antenna with the highest reception level is adopted.

As described above, in the past, it was possible to obtain a received signal with relatively good communication quality using the diversity reception method.

There are two types of diversity reception methods: an antenna switching diversity reception method and a post-detection selection diversity reception method.

The former method is disclosed, for example, in Japanese Patent Application Laid-Open No. 61-30137, and is a method in which a plurality of receiving antennas are switched and connected to a subsequent demodulator. On the other hand, the latter is a method in which a plurality of demodulators are provided in addition to receiving antennas, and demodulated outputs are selectively output.

The former has an advantage over the latter in that only one demodulator is required, so the device configuration is small and the installation space in the vehicle is small. Although the latter has a larger device configuration than the former, the communication quality is better because it does not perform output switching at high frequencies.

0010

[Problem to be Solved by the Invention] However, in conventional diversity receiving devices, it is assumed that the noise level arriving at each antenna is equal, and the antenna with the highest input power value has the highest CNR and excellent transmission quality. Since the switching is performed based on the judgment, there is a problem that the noise level of each antenna is different due to the following reasons, and the switching is not necessarily optimal.

Namely, (1) As the electronics of automobiles progress, the number of electronic devices mounted on automobiles increases, and some parts of the automobile body generate high noise.

(2) In order to obtain a higher diversity effect, if each antenna is installed further apart, the noise level will differ depending on the difference in the installation position.

(3) When directional antennas are used to eliminate the effects of multiple waves, the noise level may vary depending on the directional direction of each antenna.

The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to provide diversity reception that can perform optimal switching and obtain good communication quality even when the noise levels of each antenna are different. The goal is to provide equipment.

[0015]

Means for Solving the Problems In order to achieve the above object, the diversity receiving device of the present invention includes a plurality of level detection means for respectively detecting power values of received waves from a plurality of receiving antennas, and a plurality of Packet gap detection means detects the reception packet gap between received packets, and the power value of the received wave at the non-reception packet gap detected by the level detection means is determined based on the detection signal from the packet gap detection means at the next packet gap. a hold means for holding the received wave up to the level detection means, and a received power to noise power value (CNR) of the received wave from the power value of the received wave from the level detection means and the power value of the received wave in the gap between non-received packets from the hold means. A calculation means for calculating each reception wave from a plurality of reception antennas for each reception packet, and a selection means for sequentially selecting and combining demodulated reception waves with a high CNR for each reception packet based on the calculated CNR. It is characterized by having.

[0016]

[Operation] The diversity receiving device of the present invention has such a configuration, and the level detector detects the power value of the received digital communication wave, but the power value is nil in the packet gap. Since it is a signal, it will give a noise level.

[0017] Therefore, by detecting this packet gap, holding it until the next packet gap as the noise level, calculating the CNR at the time of packet reception, and selecting the higher receiving system, the noise level of each antenna can be adjusted. The optimal receiving system can be selected even if the receiving system is different.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the diversity receiving apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of the configuration of this embodiment, and the receiving apparatus of this embodiment has two receiving systems each including an antenna, a frequency converter, and a demodulator. A selection diversity method is adopted. That is, antennas 10 and 12 are installed at predetermined positions in a car with a predetermined distance apart, and these two antennas 10 and 12 receive digital communication waves transmitted from a base station, and transmit them to frequency converters 14 and 16, respectively. supply to. Frequency converters 14 and 16 down-convert the input received waves and supply them to demodulators 18 and 20, as well as level detectors 24 and 26 that detect the power value of the received waves.

After the received waves input to the demodulators 18 and 20 are demodulated, they are supplied to the selector switch 22, where one system of received waves is selected according to the method described later, and the received waves are sent via the communication control section 34. Output.

On the other hand, the power value of the received waves that are down-converted by the frequency converters 14 and 16 and supplied to the level detectors 24 and 26 is detected, but as shown in FIG.
As shown in the timing chart, in the packet region of the digital communication wave sent from the base station, a composite level of the carrier level and noise level is detected, while in the no-signal region between the packet regions. In this case, there is no carrier level, and only the noise level is detected. Therefore, by measuring the power value of the received wave in this packet gap, only the noise level of the received wave can be detected.

Therefore, in this embodiment, the detection signals from the level detectors 24 and 26 are switched to the switching controller 28.
The sample and hold devices 30 and 32 hold the power value in the packet gap and measure the noise level.

That is, when the above-mentioned communication control section 34 detects a packet gap, this communication control section 34 supplies a sample and hold control signal (see FIG. 2(c)) to the above-mentioned sample and hold devices 30 and 32. Sample hold device 3
0 and 32 receive this control signal and hold the power value of the received wave in the packet gap, that is, the noise level, until the next packet gap. In FIG. 2, the noise level maintained in this way is indicated by a dash-dotted line. Then, by supplying the held noise level to the switching controller 28, the carrier level and noise level from each system are input to the switching controller 28, and the CNR in the received packet is measured. Then, the switching controller 28 compares the CNR of each system, selects the system with the highest CNR, and supplies a selection signal to the aforementioned changeover switch 22 to perform switching.

[0024] Then, the received signal outputted via the communication control section 34 is always a demodulated signal with a high CNR, and a signal with the highest communication quality can be obtained. Note that in this embodiment, the noise level in the packet gap is held, and this held noise level is regarded as the noise level in the next packet, and the CN
Although R is calculated, since fluctuations in the noise level generated from electronic devices installed in automobiles and the like are sufficiently long compared to one packet time, CNR can be measured with sufficient accuracy.

[0025]

As explained above, according to the diversity receiving device according to the present invention, the best transmission quality can be achieved by monitoring the carrier level and noise level of each system and selecting the system with the best CNR. It becomes possible to obtain.

[Brief explanation of the drawing]

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

FIG. 2 is a timing chart diagram in the same embodiment.

[Explanation of symbols]

10,12 Antenna 24, 26 Level detector 28 Switching controller 30, 32 Sample and hold device 34 Communication control section

Claims (1)

[Claims] 1. A diversity receiving device for digital mobile communications that receives digital received waves consisting of a plurality of received packets with a plurality of antennas, demodulates them, and combines them, wherein the received waves from the plurality of reception antennas are a plurality of level detecting means for detecting power values respectively; a packet gap detecting means for detecting a received packet gap between the plurality of received packets; and a detection signal from the packet gap detecting means detected by the level detecting means. a hold means for holding the power value of the received wave in the no-receive packet gap until the next packet gap; the power value of the received wave from the level detection means and the power of the received wave in the no-receive packet gap from the hold means; calculating means for calculating a received power to noise power value (CNR) of a received wave for each received packet for each received wave from the plurality of receiving antennas from the value; and a demodulated received wave having a high CNR based on the calculated CNR. a selection means for sequentially selecting and synthesizing for each received packet;
A diversity receiving device comprising: