JPS5928304B2 - Diversity reception method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for reducing the frequency of code errors caused by multipath fading, etc. in fixed or mobile radio communication systems using digital angle modulation. This relates to the reception method.

Conventionally, this type of diversity reception method includes (i)
A method of selectively receiving the received signal of the branch that takes the maximum value by detecting the envelope level of the received signal of each branch and comparing them with each other (selective combination diversity reception method), (■i) Received signal of each branch There is a method (equal gain combining diversity reception method) in which the phases of the received signals of each branch are compared with each other, the phase difference of each branch is controlled to be zero, and then the signals are combined and received at the same level (equal gain combining diversity reception method). A method of combining and receiving signals by comparing them with each other, controlling the respective phase differences to be zero, weighting them in proportion to the envelope level of each received signal, and then performing combined reception (maximized combined diversity reception method). ) have been adopted.

In either case, these methods not only require a circuit for detecting the envelope level ((1) and (111)) and a circuit for detecting the phase difference ((1i) and (111)), but also each A circuit that compares the envelope levels of branches and determines the maximum value and then selects that branch ((1)), a control circuit that makes the phase difference zero ((Ii) and (I
il)) and a circuit ((111)) that weights the received signal of each branch according to the level ratio. This has not only been an obstacle to simplifying and downsizing the structure of the diversity receiving device, but has also caused problems in terms of operational stability and economic efficiency. SUMMARY OF THE INVENTION Accordingly, the present invention aims to improve the above-mentioned drawbacks of the prior art, and its purpose is to reduce the frequency of code errors caused by manoretic path fading and the like.

The present invention is characterized by using the output of a local oscillator that amplitude-modulates the received signal of each branch with a specific waveform that is synchronized with the repetition period of the digital modulation signal waveform and satisfies a mutually complementary relationship. This is a diversity reception method in which a plurality of signals obtained by frequency conversion or direct amplitude modulation of the received signal itself using the specific waveform are synthesized and received, and then delayed detection and integral detection are performed. This will be explained below with reference to the drawings. FIG. 1 shows an embodiment applied to two-branch reception, in which 1 and 2 are receiving antennas, 3 and 4 are frequency converters, 5 and 6 are amplitude modulators, and 7 and 8 are input signals for amplitude modulation. 9 is a local oscillator, 10 is a synthesizer, 11 is a delay detector, 12 is an integral detector, 13 is a clock synchronization circuit, 14 is a waveform generator, and 15 is a demodulation output terminal.

First, the two signals received by the receiving antennas 1 and 2 are applied to the amplitude modulation input signal terminals 7 and 8 using specific waveforms that satisfy a mutually complementary relationship, and are applied to the amplitude modulators 5 and 6. The outputs of the 9 local oscillators subjected to amplitude modulation using the oscillator, and the two signals in the intermediate frequency band obtained by mixing with the frequency converters 3 and 4 are combined and received by the 10 synthesizers. Delay detection is performed by 11, and integral detection is performed by 12 using a clock signal reproduced by a clock synchronization circuit 13, and a desired signal is demodulated and reproduced, and outputted from 15.

It is assumed that the clock signal is generated by the waveform generator 14 using the clock signal reproduced by the clock signal 13.

The fact that the combined reception effect in such a diversity reception system matches that in the conventionally known maximum ratio combining diversity reception system will be explained below using a mathematical formula. Now, the received waves r1(t) and R2(t) by the two receiving antennas are received via a multipath propagation path modeled as a Lehle fading channel. Assuming this, it is expressed mathematically as follows.

(tbi -1C [-t -J list RJ\WC number? γ
IIr'ノ'' However, Re{} in the above formula means taking the real part of {}, and ω.

and ψr]1(t) indicate the center angular frequency of the carrier wave and the digital angle modulation signal, respectively. Moreover, Z1 and Z2 are complex Gaussian variables, and the envelopes Rl and R2 according to the Lehre distribution law and the phase θ1 according to the uniform distribution law
, θ2 as shown in the following equation. ●
◆b Let r1(t) and R2(t) expressed by equation (1) be converted to a specific waveform Mlrl(
When the frequency is converted using the output of the local oscillator which is amplitude-modulated with t) and M2r2(t), two signals e1(t) and E2 are generated in the intermediate frequency band as shown in the following equations.
(t) is obtained.

AO' However, ωo represents an angular frequency corresponding to the intermediate frequency.

By combining the two signals in equation (3), the input e(t) to the differential detector is expressed as shown in the following equation.

c? ? ? ? ζ;;(???C??憚−RJ\??υiexposureTllll~-'NONOX▲IHowever, Z(t) shall be given by the following formula.Here, the noise level of the receiver If the output v(t) of the differential detector is determined to be sufficiently small, the following equation is obtained.T is the delay time in the delay line of the differential detector, and is usually selected as the repetition period of the digital angle modulation signal.

Assuming that the digital angle modulation signal to be considered is a two-phase differential phase modulation signal, ω0T and ψIn(t) each satisfy the following relationship.

Therefore, the output v(t
) is the following formula. This is expressed as t=(n-1) t=NT
By integrating over , we obtain the output of the integral detector as
-T), the formula σ0) becomes.

Here, m1(t) and M2(t) are selected so as to satisfy the following special relational expression. Here n is an integer,
T is the repetition period of the digital signal waveform, and m is the number of branches. The former is a condition for satisfying periodicity,
The latter is a condition for satisfying orthogonality. The above two equations can be summarized as shown in equation (self).

From this, equation (self) can be obtained as follows using R and R2 defined in equation (2).

Equation A3) & is consistent with the output of the delay detection/integral detector when the conventionally known maximum ratio combining diversity reception method is introduced, and the combined reception effect of this diversity reception method is the maximum ratio combination reception effect. It shows that you are getting used to it. An example of a concrete solution that satisfies the equation Q force is ωBT-
The following can be considered as 2π. The above is an explanation for a diversity reception system with two branches, but it is clear that the same thing can be extended to a case with two or more branches, and in that case, the expression a'' corresponds to The relationship is as follows.Furthermore, although the above explanation has been made using a two-phase differential phase modulation signal as an example, it goes without saying that polyphase differential phase modulation signals such as 4-phase, 8-phase, 16-phase, etc. The present invention can be similarly applied to other general digital angle modulation signals to which the differential detection/integral detection method can be applied, including phase continuous FSK signals.

As is clear from the above description, according to the present invention, the clock synchronization signal generated by the waveform generator using the clock synchronization signal regenerated from the demodulation signal is synchronized with the repetition period of the digital modulation signal waveform and has a mutually complementary relationship. By simply receiving multiple signals obtained by frequency conversion using the output of a local oscillator that has been amplitude-modulated by a specific waveform that satisfies The same improvement effect will be obtained.

In the conventional maximum ratio combiner 4 varsity reception system, it was not only necessary to synchronize the carrier phase of the received signals of each branch, but also to weight the received signals of each branch according to their respective envelope levels. Although it was necessary, the present invention eliminates the need for these complicated and advanced techniques. FIG. 2 shows another embodiment of the invention, in which all symbols are the same as in FIG.
) is the angular frequency ω of the intermediate frequency.

ω. It should be easy to understand by putting it as.
In addition, in FIG. 2, the synthesizer may be placed after frequency conversion to an intermediate frequency, and this is a matter of which frequency band should be used to perform the operations of delayed detection and integral detection, and this is all covered by this patent. do. In addition, the delayed detection/detection method used in the present invention
The detection method called integral detection has a noise margin,
Although it is slightly inferior in terms of waveform distortion, interference resistance, etc., as a measure to remedy this, it is also possible to adopt an auxiliary means of performing error correction using delayed detection output over two or more time slots.

As is clear from the above description, according to the present invention, the clock synchronization signal regenerated from the demodulated signal is used to synchronize with the repetition period of the digital modulation signal waveform generated by the waveform generator and to establish a mutually complementary relationship. Either by converting the frequency using the output of a local oscillator that has been amplitude-modulated with a specific waveform that satisfies the user, or by simply synthesizing multiple signals obtained by directly amplitude-modulating the received signal itself with the above-mentioned waveform. Just by receiving the signal, an improvement effect equivalent to that of the conventionally known maximum ratio combining diversity reception method can be obtained.

In the conventional maximum ratio combining diversity reception method, it was not only necessary to synchronize the carrier wave phase of the received signal of each branch, but also to weight the received signal of each branch according to its envelope level. However,
The present invention eliminates the need for these complex and advanced techniques. That is, the present invention can achieve the same effect as the conventional maximum ratio combining diversity method with a simple device configuration, and is particularly advantageous when fading changes quickly. The present invention is not only useful as a measure to improve reliability when transmitting signals using the digital angle modulation method in poor communication channels such as land mobile radio channels where multipath fading is always present, but also useful for improving the reliability of signals transmitted using digital angle modulation. It is also useful as a fixed wireless transmission line using millimeter waves.

[Brief explanation of the drawing]

FIG. 1 is a program diagram of a diversity receiving apparatus in which the present invention is applied to two-branch reception, and FIG. 2 is a program diagram of another diversity receiving apparatus according to the present invention. 1, 2...Receiving antenna, 3, 4...
Frequency converter, 5, 6... Amplitude modulator, 7, 8
...Input signal terminal for amplitude modulation, 9...
Local oscillator, 10...Synthesizer, 11...
・Delay detector, 12... Integral detector, 13...
. . . Clock synchronization circuit, 14 . . . Waveform generator, 15 . . . Demodulation reproduction output signal terminal.

Claims (1)

[Scope of Claims] 1. In a multi-branch diversity reception system in a communication system using digital angle modulation, signals are synchronized with the repetition period of the digital angle modulation signal waveform and have a mutually complementary relationship, that is, m_i(t)−m_i(t −T)=
0: i = 1, 2, 3, ..., m, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (i≠j, i, j = 1, 2, 3, ...
, m) (where n is an integer, T is the repetition period of the digital angle modulation signal waveform, and m is the number of branches) The received signal is frequency-converted using the output of a local oscillator that is amplitude-modulated with a waveform that satisfies the following: A diversity reception method characterized by combining and receiving multiple obtained signals, performing delayed detection and integral detection. 2. In a multi-branch diversity reception system in a communication system used in the digital angle modulation method, the digital angle modulation signal waveform synchronizes with the repetition period and has a mutually complementary relationship, that is, m_i(t)-m_i(t-T)=
0: i = 1, 2, 3, ..., m, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (i≠j, i, j = 1, 2, 3, ...
. A diversity reception method characterized by receiving composite signals, performing delayed detection, and performing integral detection.