JPH1141157A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently obtain a path diversity effect by using plural antennas by providing (n) equalizers for estimating propagation path characteristics, and obtaining an equalized output for the received signal of (n) directional antennas whose directivity is different, and synthesizing the obtained equalized outputs. SOLUTION: Signals from a transmitter are received through plural transmission paths, and signals from different directions are separately received by directional antennas 31-33 having directivity in different directions. When equalizers 34-36 are the maximum likelihood system estimation type, each equalizer 34-36 can separate the preceding wave and delay wave of this received synthetic signal, same phase-correct it, and synthesize (equalize and output) it. Then, the obtained equalized outputs are synthesized by a synthesizer 37 so that a path diversity effect can be obtained to the maximum. A judging circuit 38 judges one point of signal point arrangement in a modulation system used for transmission according to this synthesized output, and operates symbol judgment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving device for a digital radio transmission system, and more particularly to a receiving device used for mobile communication.

[0002]

2. Description of the Related Art FIGS. 3 and 4 are block diagrams showing a conventional receiving apparatus. FIG. 3 is a block diagram showing a receiving apparatus using an adaptive array, and FIG. 4 is a block diagram showing an antenna selecting receiving apparatus using a directional antenna. It is. In the receiving apparatus shown in FIG. 3, 11 to 13 are n omnidirectional receiving antennas, 14
16 are n phase-shift gain adjustment circuits respectively connected to the omnidirectional reception antennas 11 to 13; 17 is a combiner connected to the phase-shift gain adjustment circuits 14 to 16; 18 is a phase-shift gain adjustment circuit 17 The decision circuit 19 connected to
The differential circuit 20 has two inputs connected to the input and output of the determination circuit 18, and 20 is a complex signal ω (k) (k = 1 to n) updating circuit whose input is connected to the output of the difference circuit 19. The output of 20 is connected to the phase shift gain adjustment circuits 14-16.

[0003] The operation of a receiving apparatus using an adaptive array will be described below. Since signals from a transmitter (not shown) are received by the n omnidirectional receiving antennas 11 to 13 via a plurality of propagation paths, signals having different arrival time differences (delays) from different directions of arrival are synthesized ( Multipath reception wave).

The phase shift gain adjustment circuits 14 to 16 perform a phase rotation operation and a gain adjustment on each of the reception signals received by the omnidirectional reception antennas 11 to 13. The signal whose phase and amplitude has been adjusted by the phase shift gain adjustment circuits 14 to 16 is
7, and is output as a composite output y (t) (t is time). The determination circuit 18 estimates a desired signal Y (t) when there is no influence from the propagation path based on the combined output y (t), and sets it as a determination output. The difference circuit 19 detects a difference signal (error signal) between the combined output y (t) and the desired signal Y (t), and updates the phase shift amplitude operation information ω (1) to ω (n) of each antenna. .

Here, the updating method of ω (1) to ω (n) includes an LMS method (Least Mean Square).
error), CMA method (Constant Mod)
ulus Algorithm) and the like are known. In either system, ω (1) to ω (n) are set so that the direction of arrival of the received wave has directivity of the antenna and the null point (reception gain in the direction of arrival) is directed to the other (interference wave or the like) direction. )
Is controlled.

In the configuration of the receiving apparatus using the adaptive array shown in FIG. 3, any directional characteristics can be obtained by using an omnidirectional antenna, so that directivity control can be performed without performing mechanical operation control. There is an advantage. However, in the multipath propagation condition, especially for an arriving wave (delayed wave) having a large arrival delay difference, the directional control is performed so that the null point is regarded as an interference wave. An equalizer trying to obtain a path diversity effect,
CDMA (Code Division Multiple)
The RAKE method of "le Access" has a drawback that the path diversity effect cannot be sufficiently exhibited.

Next, an antenna selective receiving apparatus using the directional antenna shown in FIG. 4 will be described. 21-2
Reference numeral 3 denotes n directional receiving antennas, and 24 denotes receiving antennas 21 to 2 based on output signals of the receiving antennas 21 to 23.
An antenna selection circuit 25 for selecting any one of the antennas 3 and 25 is a switch for connecting any one of the reception antennas 21 to 23 to the determination circuit 26 based on the output signal of the antenna selection circuit 24.

[0008] The operation of the antenna selection receiving apparatus using a directional antenna will be described below. Here, the n directional receiving antennas 21 to 23 are configured to have directivities in different directions. A reception signal from a transmitter (not shown) passes through a plurality of
~ 23. At this time, signals arriving from different directions of arrival are separated by the directivity of the receiving antennas 21 to 23.

[0009] The antenna selection circuit 24 includes an RSSI (Receive Sig) for each of the directional antennas 21 to 23.
nal strength indicator), and controls the changeover switch 25 so as to select the directional antenna reception signal indicating the maximum RSSI. The determination circuit 26 performs data determination based on the reception signal thus selected.

[0010] By using such a configuration, it is possible to select the arrival direction at which the reception level becomes maximum, and to reduce the influence of the reception wave and the interference wave from the other arrival directions. However, even in such a configuration, similarly to the receiving apparatus using the adaptive array shown in FIG. 3, since it is controlled so as not to receive the reception signal of the same transmitter arriving from another direction, the path diversity effect is obtained. There is a drawback that can not be exhibited.

[0011]

The problem of the receiver using the adaptive array, which is an example of the conventional receiver shown in FIG. 3, will be described below in detail with reference to FIG. As a received signal from the transmitter, a signal received earlier in arrival time is referred to as a preceding wave 60, and a signal received with a delay difference that is not negligible compared to the modulation section is referred to as a delayed wave 61.

Here, as shown in FIG.
And the case where the delayed wave 61 is received from different directions of arrival. In a receiving apparatus using an adaptive array antenna, since the delayed wave 61 has a small correlation with the preceding wave 60, in the control for extracting the preceding wave 60, The null point is controlled in the arrival direction of the delayed wave. Accordingly, as shown by the bold line 62 in the figure, the directional characteristics are provided in the arrival direction of the preceding wave where the delayed wave 61 does not arrive. In the equalizer and the CDMA RAKE system, the characteristics can be improved by separating the leading wave 60 and the delayed wave 61 to have a path diversity effect, whereas the receiving device using the adaptive array discards the delayed wave component. Therefore, there arises a problem that the path diversity effect cannot be sufficiently exhibited.

Next, the problem of the antenna selection type configuration using a directional antenna which is an example of the conventional receiving apparatus shown in FIG. 4 will be described in detail with reference to FIG. FIG. 6 shows a case where a plurality of preceding waves 65 to 67 and delayed waves 70 and 71 are received from different arrival directions, similarly to FIG. In the drawing, as an example, each directional antenna has a different directional direction indicated by a dotted fan shape. 1 to No. 8 shows a case of eight directional antennas.

The arriving wave having the maximum amplitude in FIG. 8, if the directional antenna No. 8 is included. 8 is selected. However, in other arrival directions (for example, the delayed wave 7 of the directional antenna No. 3).
1, No. 5, no. The received wave of the preceding wave 66, 67) is discarded although the path can be separated by the directional antenna, so that the path diversity effect cannot be sufficiently exhibited as in the configuration shown in FIG. Produces a point.

The present invention has been made in order to solve the above-mentioned conventional problems, and has as its object to provide a receiving apparatus that can sufficiently obtain a path diversity effect by using a plurality of antennas.

[0016]

As shown in FIG. 1, the present invention relates to a receiving apparatus for a digital radio transmission system, which comprises n directional antennas 31 to 31 having different directivities.
3, n equalizers 34 to 36 for estimating the propagation path characteristics of the reception signals of the respective directional antennas 31 to 33 to obtain an equalized output, and outputs of the n equalizers 34 to 36 A combiner 37 for combining the equalized outputs of
And a judgment circuit 38 for judging the output of the above as one point of the signal point arrangement of the modulation method used for transmission.

Here, each of the equalizers 34 to 36 separates the preceding wave and the delayed wave of the received composite signal, particularly when these equalizers 34 to 36 are maximum likelihood sequence estimation type equalizers. In-phase correction and synthesis (equalized output).

If the equalizers 34 to 36 are decision feedback equalizers, the operation of emphasizing the higher one of the preceding wave and the delayed wave and canceling the lower one is performed.

According to such a configuration, the path diversity effect can be maximized by combining the equalized outputs obtained for the multipaths separated in each direction of arrival by the combiner 37.

As shown in FIG. 2, the present invention relates to a CDMA receiving apparatus for a digital radio transmission system, wherein n directional antennas 4 having different directivities are provided.
N matched filters 44 to 46 which obtain correlation outputs by correlating the received signals of the directional antennas 41 to 43 with the spread codes used for transmission.
And n number of RAKE circuits 47 to 49 for correcting the phase of the correlation pulse trains represented as the correlation outputs of the matched filters 44 to 46 and combining them to obtain a path combined output;
A synthesizer 5 for synthesizing a path synthesis output that is an AKE circuit output
0 and a determination circuit 51 that determines the output of the combiner 50 as one point of a signal point arrangement of the modulation scheme used for transmission.

According to such a configuration, it is possible to maximize the path diversity effect by combining the RAKE combining outputs obtained for the multipaths separated in each direction of arrival.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a block diagram showing a configuration using an equalizer as an embodiment of a directional antenna combining type receiving apparatus according to the present invention. In FIG. 1, 31 to 33 are n
Directional receiving antennas, 34 to 36 are receiving antennas 3
Equalizers connected to 1-33, 37 are equalizers 31-33
Is a decision circuit connected to the output side of the combiner 37.

The operation of the first embodiment will be described below. The n directional receiving antennas 31 to 33 are configured to have directivity in different directions. Signals from a transmitter (not shown) are received via a plurality of propagation paths, and signals arriving from different directions of arrival are directional antennas 31 to 31.
33 and received separately. However, if the directions of arrival are the same, the preceding wave and the delayed wave are received by the same antenna. Therefore, each of the equalizers 34 to 36 receives the synthesized signal of the preceding wave and the delayed wave (only one of them, or (There may be no wave).

In each of the equalizers 34 to 36, especially when these equalizers 34 to 36 are the maximum likelihood sequence estimation type equalizers, the preceding wave and the delayed wave of the received synthesized signal are separated and the in-phase correction is performed. It is possible to equalize and output (equalized output).

If the equalizers 34 to 36 are decision feedback equalizers, the diversity effect is enhanced by the operation of emphasizing the higher level of the preceding wave and the delayed wave and canceling the lower level. can get.

By combining the equalized outputs obtained for the multipaths separated in the respective directions of arrival by the combiner 37, it is possible to obtain the maximum path diversity effect. The determination circuit 38 determines one point of the signal point constellation of the modulation scheme used for transmission from the output combined by the combiner 37,
A symbol determination according to the modulation scheme is performed from the path-diversified signal.

Embodiment 2 FIG. FIG. 2 is a block diagram showing a directional antenna combining type receiving apparatus using a CDMA RAKE circuit as another embodiment of the present invention.
2, 41 to 43 are connected to n directional receiving antennas, 44 to 46 are connected to receiving antennas 41 to 43,
MF (matched filter) using a spread code used for transmission, 47 to 49 are RAKE circuits connected to MFs 44 to 46, 50 is a combiner connected to RAKE circuits 47 to 49, and 51 is a combiner 50 Is connected to the determination circuit.

The operation of the second embodiment will be described below. The n directional receiving antennas 41 to 43 have the same configuration as the receiving antennas 31 to 33 shown in the first embodiment. Signals arriving from different directions of arrival are separated by the directional antennas, and each antenna receives a leading wave and a delayed wave whose arrival directions are close to each other. You.

In the MFs 44 to 46, the correlation is obtained by the same spreading code as in the transmission, and the MF output is obtained by separating the preceding wave and the delayed wave of the received composite signal. The RAKE circuits 47 to 49 correct the in-phase and delayed waves of the MF output in phase and combine them (RA
KE synthesis) is output. The synthesizer 50 can maximize the path diversity effect by synthesizing the RAKE synthesis outputs obtained for the multipaths separated in each direction of arrival. The determination circuit 51 determines one point of the signal point constellation of the modulation scheme used for transmission from the output combined by the combiner 50, and performs symbol determination from the path-diversified signal according to the modulation scheme.

As described above in the first and second embodiments, all incoming directions and all delayed wave components can be in-phase without cutting off the delayed wave components and the signal components in different incoming wave directions which have been cut off in the prior art. And can be combined, and the error rate can be improved.

[0031]

As described above in detail, according to the present invention, it is possible to obtain a sufficient path diversity effect, thereby improving the error rate of digital mobile radio and greatly improving transmission quality. Is achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an equalizer combining receiver using a directional antenna according to a first embodiment.

FIG. 2 is a block diagram showing a RAKE combining type receiving apparatus using a directional antenna according to a second embodiment.

FIG. 3 is a block diagram showing a receiving apparatus using an adaptive array as an example of the related art.

FIG. 4 is a block diagram showing a receiving apparatus using a directional antenna as an example of the related art.

FIG. 5 is an explanatory diagram showing reception directivity characteristics of a reception device using a conventional adaptive array.

FIG. 6 is an explanatory diagram showing reception directivity characteristics of a receiving device using a conventional directional antenna.

[Explanation of symbols]

 31 to 33, 41 to 43 Directional receiving antenna 34 to 36 Equalizer 37, 50 Combiner 38, 51 Judgment circuit 44 to 46 Matched filter (MF) 47 to 49 RAKE circuit

Claims (2)

[Claims] 1. A receiving apparatus for a digital radio transmission system, comprising: n directional antennas having different directivities; and estimating a channel characteristic of a reception signal of each of the directional antennas to obtain an equalized output. Equalizers, a combiner that combines the equalized outputs that are the outputs of the n equalizers, and the output of the combiner is determined as one point of a signal point arrangement of a modulation scheme used for transmission. And a determining circuit for performing the determination. 2. A CDMA system for a digital radio transmission system.
A receiving apparatus of a system, wherein n pieces of directional antennas having different directivities, and n pieces of spread codes used for transmission with respect to the reception signals of the respective directional antennas to obtain a correlation output are obtained. A matched filter, and n number of Rs which are phase-corrected and combined into a path combined output of a correlation pulse train appearing as a correlation output of the matched filter.
An AKE circuit, a combiner that combines the n combined RAKE circuit outputs, and a determination circuit that determines the output of the combiner as one point of a signal point arrangement of a modulation scheme used for transmission. A receiving device, comprising: