JPH04185130A - Diversity receiver for spread spectrum communication - Google Patents

Abstract

PURPOSE:To reduce the effect of a multi-path and to attain stable transmission reception by providing a 2nd antenna parted spatially with respect to a 1st antenna and taking the signal of the 2nd antenna non-correlation from the signal of the 1st antenna. CONSTITUTION:The receiver consists of antennas 13, 14, filters 15, 16, amplifiers 17, 18, a delay device 19 and a synthesizer 20 or the like. Then the distance between the antennas 13, 14 is spatially parted by lambda/3 (lambda is a wavelength of a carrier) or over so that an SS reception signal S5(t) from the antenna 13 and an SS reception signal S6(t) from the antenna 14 are almost in non- correlation. Thus, the SS signal received by the antenna 14 reaches an independent reception signal level. For example, a phase difference of a carrier in the correlation spike is 0 deg. (synchronization), the synthesized correlation spike is not almost suppressed. Thus, the effect of the multi-path is reduced and stable transmission reception is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diversity receiving device suitable for spectrum communication.

[Summary of the Invention] This is a diversity device that has two spatially separated antennas and reduces the effects of multipath by delaying and combining one of the SS signals received by these antennas.

[Prior art] Svegtram diffusion communication system (hereinafter abbreviated as SS communication system)
is known as a method that is more resistant to multipath fading than normal narrowband communication methods (such as FM). However, this is not necessarily the case when the delay time difference between the direct wave and the reflected wave is within 2 chips of the PNN code.

In order to clarify this problem, as shown in Figure 5,
A case will be considered in which there is a direct path and a reflected path in the propagation path from the S transmitter 1 to the SS receiver 2, and the SS receiver 2 receives a direct wave and a reflected wave. Here, it is assumed that the signal levels of the direct wave and the reflected wave are equal, and a convolver is used as a correlator in the SS receiver 2.

First, when the SS receiver 2 receives a direct wave, the convolver performs a correlation calculation between the received PN code of the direct wave and its time-reversed reference l) input code, resulting in a correlation spike as shown in FIG. A correlation output called . Note that the pulse width T is the length of one PN code chip.

Next, when a reflected wave of the same level is received following a direct wave, the delay time difference between the reflected wave and the direct wave is PNN code 2
Within the chip length, the correlation spike due to the direct wave and the correlation spike due to the reflected wave will interfere.

For example, the delay time difference between the direct wave and the reflected wave is Pt'J code 2
Within the chip length, the carrier phase difference during the correlation spike of the correlator output for each received signal is 1.80°
In the case of (reverse phase), the synthesized correlation spikes are almost suppressed as shown in Figure 7, so the S/N improvement effect by process gain, which is a feature of the SS communication system, cannot be expected, and therefore the data Demodulation performance is also poor.

Note that this problem is the same even if a matched filter or the like is used as the correlator. .

As a solution to these problems with conventional methods, various diversity methods can be considered, similar to narrowband communication methods.Diversity methods utilize multiple received signals that have statistically low correlation. For example, there is a selection diversity system as shown in FIG.

This method consists of antennas 3, 4, filters 5, 6, amplifiers 7, 8, detectors 9, 10, envelope comparator 11, selection switch 12, etc., and the distance between antennas 3 and 4 is determined spatially. By separating them north by λ/3 (λ, the wavelength of the carrier wave), the SS received signal (t) from antenna 3 and the SS received signal (t) from antenna 4 become almost uncorrelated. We are using. The operation of each part shown in FIG. 8 will be described below.

Filters 5 and 6 remove signals in bands other than S, (t) and S, (t), and amplifiers 7 and 8 remove signals in bands other than S, (t) and S, (t).
Detectors 9 and 10 amplify S,(t).
, (t) and S, (t), and the envelope comparator 11 detects the detector outputs S, (t) and S, (t).
The 1 selection switch 12 selects the one with the larger received signal level based on the comparison information from the envelope comparator 11, and selects the one with the larger received signal level.
Output to S receiver 2. This improves the S/ of the received SS signal, and can be expected to improve data demodulation performance.

[Problems to be Solved by the Invention] However, this conventional selection diversity method
, 10, a large number of circuit components such as an envelope comparator 11 and a selection switch 12 are required, which is disadvantageous in terms of miniaturization and cost of the device, and switching noise generated in the selection switch 12 affects data demodulation performance. There was a problem with that.

An object of the present invention is to provide a diversity receiving device that has a relatively simple configuration, reduces the effects of multipath, and enables stable transmission and reception.

[Means for Solving the Problems] Note [In order to achieve the first objective, the diversity receiving device for SVEG tram spread communication of the present invention has a first antenna and a second antenna spatially separated from the first antenna. an antenna, a delay device that delays <3 from the second antenna for a predetermined period of time, and -1- a signal from the antenna of description 1.
The gist of the present invention is to include a composition means for composition of the outputs of the first delay means.

[Operation] The second anti-missing signal is uncorrelated with the first antenna signal and its level is independent, so the correlation spike of the SS receiver in response to the composite ratio horn is suppressed by multipath. Things will go away.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of diversity equipment for SS communication according to the present invention. This device consists of an anti-t 13° 14, a filter +5.16, an amplifier +7.18° delay 191, a synthesizer 20, etc.

Next, the operation of the above embodiment will be explained.

The antennas 13 and 14 are spatially separated by λ/;3 or more, and the SS reception signal is received from the antenna 1:3 side.

(1) and the SS reception signal from the Asitenato 4 side.

Make sure that (1) is almost uncorrelated. Filter 15.
16 removes signals in bands other than S, (t) and S, (t), and amplifiers 17 and 18 remove signals in bands other than S, (t).

(t), S, and (t) are amplified. The delay device 19 delays the output S,(t) of the amplifier 18, and the delay time τ is τ≧PN code 2 chip length and the maximum delay of the reflected wave that has an influence on the direct wave. Assuming that the time is τ8, a delay time of τ≧2τa is set. The combiner 20 combines the output S,(t) of the amplifier 17 and the output S,(t) of the delay device 19. The combined SS received signal is S
After amplification, frequency conversion, etc. are performed in the S receiver 2 as is well known, a time-reversed reference PN code and its correlation calculation are performed in a convolver.

Note that the delay device 19 applies the delay to the synthesizer 20.
The SS signal received at the antenna 13 side and the SS signal received at the antenna 14 side which are combined are separated in the time domain as correlation spikes by a correlator, and the SS signals at the antenna 13 side and the antenna 14 side are separated in the time domain. This is to remove the interference of the received signal, and the S received on the antenna 13 side is
In the S signal, the delay time difference between the direct wave and the reflected wave is PNN
Within code 2 chips, the carrier phase difference in the correlation spike of the correlator output for each received signal is 180'.
In the case of (reverse phase), as described in the conventional example, the synthesized correlated spikes are almost suppressed as shown in FIG. However, since the SS signal received on the antenna 14 side has no correlation with that on the antenna 13 side, the received signal level becomes independent. For example, if the phase difference of the carriers in the correlated spikes is O' (in-phase), the combined correlated spikes will hardly be suppressed as shown in FIG. 2.

In such a state, the present device delays and synthesizes the SS signals received at the antenna 14 side, thereby eliminating the suppression of correlation spikes due to multipath as shown in FIG. Improves the S/N of the received SS signal.

The aim is to improve data demodulation performance.

Note that the above description is based on the case where there are two antennas, but
When using multiple antennas to further improve the data demodulation ability, each antenna has a different delay time (τ1,..., τ,) that can be separated as correlated spikes in the 1-time domain, as shown in Figure 4. It is sufficient to prepare delay devices d1 to dn-, and to combine their outputs. In FIG. 4, a1 to an are antennas, b1 to bn are filters, and c1
~c, 1 is an amplifier, and e is a combiner.

[Effects of the Invention] As explained above, the device of the present invention can be realized with a simpler configuration than the conventional example, and the number of circuit components can be reduced, so that the device can be made smaller and the cost can be reduced. Furthermore, since the antenna outputs are combined, it is possible to eliminate switching noise caused by the selection switch.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Figs. 2 and 3 are explanatory diagrams of the operation of the above embodiment, Fig. 4 is a block diagram showing another embodiment of the invention, and Fig. 5 7 to 7 are explanatory diagrams of conventional systems, and FIG. 8 is a block diagram of another conventional system. 2...SS receiver, 13.14...
...Antenna, 15.16...Filter, 17,1.8...Amplifier, 19...
...Delay device, 20...Synthesizer. Patent Applicant Glarion Co., Ltd. Agent Patent Attorney Nagai 1) Take Sanbu 11-4 Figure 2

Claims (1)

[Claims] A first antenna, a second antenna spatially separated from the first antenna, a delay means for delaying a signal from the second antenna for a predetermined time, A diversity receiving device for spread spectrum communication, comprising: combining means for combining a signal from an antenna and the output of the delay means.