JPH0767090B2 - Harmonic diversity transceiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic diversity transmitter / receiver in a digital wireless communication system.

[0002]

2. Description of the Related Art In digital radio communication, especially mobile communication, fading is always present, so that it is not easy to secure the quality of received signals. For this reason, diversity technology is often used. For example, using two or more antennas that are separated so that the spatial correlation of the reception level is low, the spatial diversity of receiving by switching to the higher level or the carrier frequency that differs from two or more transmitting base stations by a specific frequency is used. Are modulated by the same baseband signal and transmitted at the same time, and the receiving section uses transmission diversity or the like in which the signal is received by one antenna. In the former case, two receiving antennas are required, and further a circuit for comparing these two receiving levels and a circuit for selecting a signal based on this are required. Therefore, the circuit configuration becomes complicated. Further, in the latter case, it is necessary to secure a constant frequency difference between a plurality of base stations that are distant from each other in distance and to keep the time lag between the base stations of the modulated baseband signal small, which causes a problem that the system configuration becomes complicated. Have.

[0003]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the complicated apparatus structure of the present invention, a signal is transmitted from one station and a receiving section receives it from one antenna and demodulates it. Even so, it is an object of the present invention to provide a harmonic diversity transmitter / receiver having a simple configuration that can obtain a diversity effect.

[0004]

In order to solve the above-mentioned problems, the present invention transmits two signals whose frequencies are separated so as to reduce the correlation in the spatial propagation path in a multiplication relationship from one anthena. At this time, the digital FM modulation index of the fundamental frequency signal is made equal to a value obtained by dividing an arbitrary even number by the multiplication order. Next, the fundamental frequency signal component thus generated and the multiplied harmonic signal component are frequency-converted into a required transmission RF band, appropriately amplified, and transmitted from one anthena.

In the receiving section, the above-mentioned two signals which have been frequency-converted into the RF band and transmitted are received by one anthena, are converted into IF signals having the same center frequency in the detection band, and the original signal is outputted by one FM detector. Demodulate.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing a frequency relationship of a transmitting unit according to the invention of claim 1, and 1 is a signal 1, 2 which constitutes one diversity branch in frequency diversity.
Is a frequency interval that is a difference frequency between the signals 1 and 2 in the IF band and constitutes another diversity branch in the RF band and constitutes another diversity branch in the RF band, and 4 is a frequency interval 3
Is a frequency interval which is the frequency of the frequency divided by 5; 5 is an IF basic signal whose center frequency is the frequency corresponding to the frequency divided; 6 is its doubled signal; 7 is a harmonic signal multiplied by the required order. Is.

When the frequency of the signal 1 in FIG. 1 is f _c1 , the frequency of the signal 2 is f _c2 , the frequency interval 3 is Δf, and the division ratio is K, the frequency interval of 4 is represented by Δf / K, and in the IF band. The multiplication order is K + 1. As described in claim 1, Δf / K is the IF frequency here. Now this is f
_i , that is, f _i = Δf / K A signal obtained by digitally FMing an IF signal of this frequency can be expressed by the following equation as well known. s ₁ (t) = cos {2πf _i t + φ ₁ (t)} (1) where

[0008]

[Equation 1]

Here, the frequency obtained by multiplying the basic IF signal s ₁ (t) by 2 is 6 and the frequency obtained by multiplying K + 1 by 7 is 7. The harmonic signal s ₂ (t) at this time is expressed by the following equation. s ₂ (t) = cos {2π (K + 1) f _i t + φ ₂ (t)} (2) Here, since the modulation index is also multiplied, the following is obtained.

[0010]

[Equation 2] Now, next, frequency conversion is performed to bring these into the required RF band. Now, the frequency difference between the basic IF frequency signal and the harmonic signal is f _i to (K + 1) f _i = Kf _i = Δf

It goes without saying that the difference between the two frequencies in the RF band is maintained. If the frequency conversion to the RF band in a single stage, the frequency f _c1 signals converted from the station may be used oscillation signal of -f _i s _1R (t) is as follows from (1). _{s 1R (t) = cos {} 2π [f i + (f c1 -f i)] t + φ 1 (t)} = cos {2πf c t 1 + φ 1 (t)} signal s _2R of contrast harmonic wave is converted (t) is s _2R (t) = cos {2π [(K + 1) f _i + (f _c1 −f _i )] t + φ from equation (2)
₂ (t)} = cos {2π (f _c1 + Kf _i ) t + φ ₂ (t)} = cos {2π (f _c1 + Δf) t + φ ₂ (t)} = cos {2πf _c2 t + φ ₂ (t)}

In this way, both the basic IF signal and its harmonic signals are converted into the required RF frequency band. Next, these s _1R (t) and s _2R (t) are transmitted from one anthena and received by the antenna of the receiving section. As described above, since the two frequencies in the RF band are set so that the correlation is small in the spatial propagation path, they are subject to independent fading. The received fundamental frequency signal 1 is r ₁ (t) = R ₁ cos {2πf _c1 t + φ ₁ (t) + θ ₁ } (3) The received harmonic signal 2 is r ₂ (t) = R ₂ cos {2πf _c2 t + φ ₂ (t) + θ ₂ } (4) can be expressed. Here, R ₁ and R ₂ are amplitude fluctuations that normally follow a Rayleigh distribution, and θ ₁ and θ ₂ are phase fluctuations that are uniformly distributed between 0 and 2π. A signal obtained by converting these to the same center frequency f _i in IF as in claim 1 is represented as follows. From equation (3) of the fundamental wave signal, r _i1 (t) = R ₁ cos {2πf _i t + φ ₁ (t) + θ ₁ } (3) ′ From equation (4) of the harmonic signal r _i2 (t) = R ₂ cos {2πf _i t + φ ₂ (t) + θ ₂ } (4) ', the combined received wave r _i (t) is r _i (t) = r _i1 (t) from (3)' and (4) '. + R _i2 (t) = R ₁ cos {2πf _i t + φ ₁ (t) + θ ₁ } + R ₂ cos {2πf _i t + φ ₂ (t) + θ ₂ } = R cos {2πf _i t + Φ (t)} where received The amplitude R and the phase Φ (t) of the composite wave are as follows.

[0013]

[Equation 3] Here, the 1-bit average CNRγ is obtained. Now, assuming that the bit rate of the transmission baseband is f _b and the period of 1 bit of its reciprocal is T _b , from the definition of CNR,

[0014]

[Equation 4] Here, the propagation path is quasi-stationary, that is, stationary on the order of the bit period (normally established because fading is on the order of tens Hz and signal speed is on the order of kHz). R ₁ , R ₂ , θ ₁ , θ ₂ : const. Setting θ ₁ −θ ₂ = Δθ, substituting equation (5) into γ,

[0015]

[Equation 5] From the quasi-stationary assumption

[0016]

[Equation 6] The third term is as follows.

[0017]

[Equation 7] Taking out the integral part is as follows.

[0018]

[Equation 8] In digital FM modulation, if the frequency shift is f _di (i = 1 is a fundamental wave signal, i = 2 is a harmonic wave signal)

[0019]

[Equation 9] ± because that the frequency modulation of _{± f di φ i (t)} = ± 2πf di t i = 1or2 where the data signal corresponds to the mark or space a _n as described above. Therefore, the equations (7) and (8) become the equations (7) 'and (8)', respectively.

[0020]

[Equation 10] From equation (7) ′

[0021]

[Equation 11] The molecule looks like this: sin {2πa _n (f _d1 −f _d2 ) T _b } = sin {π a _n (2 f _d1 / f _b −2 f _d2 / f _b )} where 2 f _d1 / f _b is the modulation index of the fundamental wave signal, 2 f _d2
/ F _b is the modulation index of the harmonic signal. If these are m ₁ and m ₂ , then sin {2πa _n (f _d1 −f _d2 ) T _b } = sin {πa _n (m ₁ −m ₂ )} (9) Here, the modulation is performed as described above. Since the relationship of the exponents is equal to the order of multiplication of the harmonics, one pair (K + 1), that is, m ₂ = m ₁ × (K + 1), and the modulation index of the fundamental wave signal is as follows: m ₁ = even / K If this is put into the equation (9), sin {2πa _n (f _d1 −f _d2 ) T _b } = − sin {πa _n (even / K− (even / K) · (K +
1))} = − sin {πa _n (even number)} = 0 Expression (7) ′, that is, the integral term of cos in Expression (7) is always 0. On the other hand, from equation (8) ′,

[0022]

[Equation 12] Here the numerator is cos {2πa _n (f _d1 −f _d2 ) T _b } −1 = cos {πa _n (m ₁ −m ₂ )} − 1 = cos {πa _n (even number)} − 1 = 0

Therefore, the equation (8) ', that is, the equation (8) is always 0.
become. Therefore, the third term including the random phase Δθ in the 1-bit average CNRγ is constantly 0, and the diversity effect can be realized.

FIG. 2 is a diagram of a frequency relationship showing the principle corresponding to the invention of claim 2, 1 and 2 show two signals in the RF band, 8 is an intermediate frequency of the RF2 frequency, and 9 is a final frequency. A frequency difference corresponding to the magnitude of the detection IF band frequency to be converted into 10: a first receiving station-originated signal, 11: an IF signal obtained by converting an RF signal 1 by a station-originated signal 10, 12: an RF signal 2 being a station IF signal converted by the outgoing signal 10, 13 is 2
The second local oscillation signal has an intermediate frequency between the two IF signals 11 and 12, and 14 is an IF signal for detection in which the IF signals 11 and 12 are converted. The operation is as follows. The RF received signal from the antenna is represented by the equations (3) and (4) as before. The fundamental wave reception signal 1 is r ₁ (t) = R ₁ cos {2πf _c1 t + φ ₁ (t) + θ ₁ } (3) The harmonic reception signal 2 is r ₂ (t) = R ₂ cos {2πf _c2 t + φ ₂ ( t) + θ ₂ } (4) As in claim 2, the first local oscillation frequency is expressed as follows. f _i1 = f _c1 + Δf / 2−f _i where Δf is the difference frequency of the RF2 signal as described above. The received signal converted by the first local oscillator signal is as follows. The signal converted from the received signal 1 is r _1i1
If (t), then f _i1 > f _c1 and _therefore r _1i1 (t) = R ₁ cos {2π (f _c1 + Δf / 2−f _i ) t − [2πf _c1 t + φ ₁ (t) + θ ₁ ]} = _{R 1 cos {2π (Δf /} 2-f i) t-φ 1 (t) -θ 1} (10) where the coefficients of the modulation signal phi ₁ (t) is - has become.
This is because the direction of frequency modulation corresponds to ± of the modulation drive signal.

[0025]

[Equation 13] Is meant to be. If the signal converted from the received signal 2 is r _2i1 (t), then f _i1 <f _c2 , so r _2i1 (t) = R ₂ cos {2πf _c2 t + φ ₂ (t) + θ ₂ −2π (f _c1 + Δf / 2-f _i ) t} = R ₂ cos {2π (Δf / 2 + f _i ) t + φ ₂ (t) + θ ₂ } (11)

As described in claim 2, the second local oscillator signal is r _1i1 (t) and r which are IF signals converted by the first local oscillator.
_2i1 first this because it is an intermediate frequency (t) is converted by to the _{f i2 = {(Δf / 2} -f i) + (Δf / 2 + f i)} / 2 = Δf / 2 The frequency and f _i2 The two IF signals are as follows. Signal r _{1i2 obtained} by converting the fundamental wave signal
(t) is r _1i2 (t) = R ₁ cos {2πf _i2 t-[(Δf / 2−f _i ) t−φ ₁ (t) −θ ₁ ]} = R ₁ cos {2πf _i t + φ ₁ (t ) + θ _1} harmonic signal signal is converted r _2i2 (t) is _{r 2i2 (t) = R 2} cos {2π (Δf / 2 + f i) t + φ 2 (t) + θ 2 -2πf i2 t} = R 2 cos {2πf _i t + φ ₂ (t) + θ ₂ }

As described above, the signals r _1i2 (t) and r _2i2 (t)
Assuming that the center frequencies are completely the same at f _i and the modulation index satisfies the above condition, a simple addition of both signals can realize a diversity effect equivalent to maximum ratio combining.

FIG. 3 shows the basic structure of the transmitting section of the present invention.
Is a transmission baseband signal, 16 is an FSK modulator, 17 is a multiplication circuit, 18 is a selective amplification circuit, 19 is a frequency conversion and power amplifier, and 20 is a transmission antenna. The operation is as follows. With the baseband signal 15, the FSK modulator 16 performs FSK with a modulation index (even / K). Next, the multiplication circuit 17 multiplies (K + 1), and the selective amplification circuit 18 amplifies the levels of the basic signal and the multiplication signal before multiplication to have appropriate levels. Next, a frequency conversion and power amplifier 19 frequency-converts into a target RF band by using a required local oscillator, and a frequency-converted fundamental wave signal and a converted harmonic signal of a multiplied wave are transmitted from the transmission antenna 20. .

FIG. 4 is a circuit configuration showing a receiving section according to the invention of claim 2, 21 is a receiving antenna, 22 is a first receiving station originating, and 23 is a first receiving station originating 22 and a first IF. A frequency converter for converting the frequency to, 24 is a second receiving station,
Reference numeral 25 is a second frequency converter for converting into a detection band, 26 is an FM detector, and 27 is a regenerated baseband signal.

[0030]

As described above, according to the present invention, phase control combining diversity can be achieved by detecting the two received waves from one antenna as they are without performing phase control and weighted combining of carrier frequencies or IF frequencies. It is possible to obtain the same effect as the characteristic.

[Brief description of drawings]

FIG. 1 is a transmission side spectrum relationship diagram showing an example of the operating principle of the present invention.

FIG. 2 is a reception side spectrum relationship diagram showing an example of the operating principle of the present invention.

FIG. 3 is a basic configuration explanatory diagram showing an example of a transmission unit of the present invention.

FIG. 4 is a basic configuration explanatory diagram showing an example of a receiving unit of the present invention.

[Explanation of symbols]

1 ... Signal 1 that constitutes one diversity branch
(Spectrum), 2 ... signal 2 (spectrum) that constitutes another diversity branch, 3 ... frequency interval that is the difference frequency between signal 1 and signal 4, ... frequency that is the frequency of an interval obtained by dividing frequency interval 3 Interval, 5 ... IF basic signal, 6 ... 2 multiplied signal, 7 ... multiplied harmonic signal, 8 ... RF2
Intermediate frequency, 9 ... Detection IF to be finally converted
Frequency difference corresponding to the magnitude of band frequency, 10 ... First receiving station-originated signal, 11 ... IF signal obtained by converting RF signal 1 by station-originated signal 10, 12 ... RF signal 2 by station-generated signal 10. IF signal, 13 ... second receiving station originating signal,
14 ... IF signal for detection, 15 ... Transmission baseband signal, 16 ... FSK modulator, 17 ... Multiplication circuit, 18 ... Selective amplification circuit, 19 ... Frequency conversion and power amplifier, 20 ... Transmission antenna, 21 ... Reception antenna , 22 ... First receiving station originating, 23 ... Frequency converter, 24 ... Second receiving station originating, 25
... Second frequency converter for converting to detection band, 26 ... FM
Detector, 27 ... Regenerated baseband signal.

Claims (2)

[Claims] 1. In a system for transmitting and receiving a digital FM signal, an integer of a difference frequency Δf of two signals having a relationship such that the correlation is low in a frequency band used in a spatial propagation path.
The first frequency signal fi fi = Δf / K of K fraction as a basic IF signal, any even number performs digital FM modulation to the modulation index value divided by the integer which only one from the integer integer greater multiplication The amplified signal and the basic IF modulated signal in the used frequency band.
A harmonic diversity transmitter / receiver including a transmission unit that frequency-converts a signal and transmits the signal, and a reception unit that receives these two signals from one antenna, converts the signals to the same center frequency signal in the IF band, and demodulates. 2. The harmonic diversity transmitter / receiver according to claim 1, wherein a signal having a frequency lower than an intermediate frequency of the received two signal frequencies by an IF frequency for finally detecting is used as a first receiving station originating signal. Using a receiving unit that performs frequency conversion, and then frequency-converts the signal of the intermediate frequency between the two signals in the IF band, which has been converted from the above two signals, as the second local oscillator signal and converts it to the same IF frequency. A harmonic diversity transmitter / receiver.