JPH0289439A - Digital radio system - Google Patents

Abstract

PURPOSE:To attain high capability of interference wave elimination and spectrum shaping close to the ideal state by applying spectrum shaping with a BTF of a transmitter, applying spectrum shaping with a SAW filter of a receiver and applying synthesized spectrum shaping. CONSTITUTION:A digital signal and a synchronizing signal inputted from input terminals 1, 2 are subjected to spectrum shaping by a BTF 3, modulated into a signal at an intermediate frequency band by a biphase modulator 4 and the resulting signal is sent to a transmission section 7 via a transmission line 6. The transmission section 7 converts the signal frequency into a radio frequency band and sends it to an antenna. The signal received by the antenna of a receiver 200 is converted into an intermediate frequency signal by a reception section 8, sent to a SAW 10 via the transmission line 9 and spectrum shaping and the elimination of an out-band undesired wave are implemented and the resulting signal is sent to a biphase detector 11, in which the signal is detected into a demodulation base band signal and a data signal, then the digital signal is sent from an output terminal 13 and the synchronizing signal is sent from an output terminal 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) This invention relates to improvements in digital radio systems.

(Prior Art) As a conventional digital radio system, one in which an LCR filter is used in the baseband band for both a transmitting device and a receiving device is known. However, when spectrum shaping is performed in the baseband band on both the transmitting and receiving sides, the CR filter of the receiving device is placed after the detection section, and there is a problem that its ability to remove interference waves near the band is low. was there.

On the other hand, some transmitter and receiver devices use surface acoustic wave (SAW) filters in the intermediate frequency band.

Spectrum shaping with such a configuration improves the ability to remove interference waves on both the transmitting and receiving sides, but if there is slight distortion in the frequency characteristics, group delay characteristics, etc. of the SAW filter, it is necessary to redesign the SAW device chip. However, there is a problem in that it is necessary to add an external correction circuit.

(Problem to be solved by the invention) As mentioned above, the conventional digital wireless system has
There are devices that have an LOR filter installed in the baseband band on the transmitting and receiving sides, but this has the problem of low ability to remove interference waves near the band. However, if there is slight distortion in the frequency characteristics, group delay characteristics, etc. of the SAW filter, it becomes necessary to redesign the device or add an external correction circuit, and the circuit There was a problem that the scale would increase.

The present invention was made in view of the problems of conventional digital wireless systems, and its purpose is to provide a digital wireless system that has high interference wave removal ability and can perform spectrum shaping close to ideal characteristics. It is to be.

[Structure of the Invention] (Means for Solving the Problems) A digital radio system of the present invention includes a transmitting device and a receiving device, and includes a binary transversal filter in the baseband band of the transmitting device; A surface acoustic wave filter is provided in the intermediate frequency band of the device, and the binary transversal filter and the surface acoustic wave filter are divided into characteristics satisfying Nyquist's first criterion by spectrum shaping. .

(Operation) According to the above configuration, spectrum shaping is performed by the BTF (binary transversal filter) of the transmitting device, and spectrum shaping is performed by the SAW filter of the receiving device, resulting in a combined spectrum shaping. Here,
The synthesized spectrum shaping is a combination of the characteristics of each filter and satisfies Nyquist's first criterion. Further, the SAW filter of the receiving device is provided before the detector in the intermediate frequency band, and performs the above-mentioned spectrum shaping as well as accurate removal of unnecessary waves outside the band.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention, in which a two-phase PS
A K-type system is shown. The transmitting device 100 is a BTF3
and a two-phase phase modulator 4, and a transmitter 7 that receives the output of the modulator 5 via an intermediate frequency transmission line 6 and transmits it from the antenna to the antenna as a radio frequency band signal. There is. The BTF 3 is provided before the two-phase phase modulator 4 and performs waveforming in the baseband band. On the other hand, the receiving device 200 includes a receiving section 8 that receives an antenna radio signal via an antenna and converts it into an intermediate frequency signal, and receives the intermediate frequency signal outputted from the receiving section 8 via an intermediate frequency transmission path 9, and receives unnecessary out-of-band signals. The demodulation section 12 includes a SAW filter 10 and a two-phase phase detector 11 for removing the . Here, the SAW filter 10 is provided in an intermediate frequency band before the two-phase phase modulator 11. Further, 1 is a digital signal input terminal, 2 is a synchronization signal input terminal, 13 is a digital signal output terminal, and 14 is a synchronization signal output terminal.

In the above, the BTF 3 and the SAW filter 10 each perform spectrum shaping, and the spectrum shaping is superimposed on the entire system, but in that case, the BT
The F3 and the SAW filter 10 are divided into characteristics that satisfy Nyquist's first criterion by spectrum shaping. For example, do the following:

The well-known Nyquist cosine roll-off characteristic Rol
l(x) is: X: normalized frequency, α: roll-off coefficient. Therefore, by taking the square root of this characteristic,
If the characteristics are such that the BTF 3 and the SAW filter 10 are divided into 0, and the transmission side performs eye aperture correction, the roll-off characteristics on the transmission and reception sides will be as follows.

Transmission side; Tf(x)=yrx/2/5i11(πx
/2)・force 61 open receiving side; Rf(x)=r pressure 1i Such a digital radio system operates as follows. The digital signal and synchronization signal input from input terminals 1 and 2 are spectrum-shaped by BTF3,
The signal is modulated into an intermediate frequency band signal by the two-phase phase modulator 4 and sent to the transmitter 7 via the intermediate frequency transmission path 6. The transmitter 7 converts the signal into a radio frequency band, and sends the signal from the antenna to the antenna. In the receiving device 200, the signal received by the antenna is converted into an intermediate frequency signal by the receiving section 8, and sent to the SAW filter 10 via the intermediate frequency transmission path 9.

The SAW filter 10 performs spectrum shaping and removes out-of-band unnecessary waves coming in from antennas, etc., and sends it to the two-phase phase detector 11, where it is detected and converted into a demodulated baseband signal, which is then converted into a data signal level. The digital signal is output from output terminal 13 and the synchronization signal is output from output terminal 1.
4, respectively.

The SAW filter 10 removes unnecessary waves, and
By superimposing the spectrum shaping of the TF3 and the SAW filter 10, a Nyquist cosine roll-off characteristic with theoretically zero code amount interference can be obtained.

FIG. 2 is a block diagram of a four-phase PSK digital wireless system. In this figure, the same components as in FIG. 1 are given the same reference numerals as in FIG. 1, and the explanation thereof will be omitted. In this embodiment, the digital signals arriving from the input terminals 15 and 16 are summed by the transmission logic circuit 18 of the transmitting device 100A, and the BTF31.3 is converted into two series of data.
2 respectively.

In BTF31.32, each series of signals and input terminal 17
It receives the synchronization signal arriving from the 4-phase modulator 19, performs spectrum shaping, and sends it to the 4-phase phase modulator 19.

The four-phase phase modulator 19 performs modulation into an intermediate frequency signal, and the same operation as the two-phase PSK system shown in FIG. 1 is performed in the transmission path. And SA of receiving part @200A
The intermediate frequency band signal input to the W filter 10 is subjected to spectrum shaping and removal of unnecessary waves outside the band, demodulated into a baseband signal by a four-phase phase detector 20, and converted to a data signal level. Reception logic circuit 21
sent to.

In the reception logic circuit 21, a difference operation is performed to obtain two systems of digital signals, and the digital signals are outputted to the output terminals 22.
23, synchronization signals are sent out from output terminals 24, respectively. The above-mentioned four-phase phase modulator 19 includes two O-π modulators, which perform modulation by giving carrier waves with a 0 phase shift and a π/2 phase shift to receive two sequences of orthogonal phases. I am getting a modulated signal. Therefore, it is necessary to perform spectrum shaping of the signals input to the two 0-π modulators, and two BTFs are required. In addition, the SAW filter installed in the intermediate frequency band is the one that synthesizes the eight systems (before separation).
Since it is for signals, only one is required.

Although the above embodiments have shown the two-phase PSK method and the four-phase PSK method, the present invention is not particularly limited to these methods and is also applicable to, for example, the QAM method. This QA
The M method is equivalent to the 4-phase PSK method, and uses two BTFs.
A system can be configured with one SAW filter.

Further, in the above embodiment, all of the eye aperture correction characteristics are provided on the transmitting side, but some or all of them may be provided on the receiving side.

Roughly speaking, in the embodiment, square root division of Roll(x) is used, but the present invention can be constructed using other theoretical formulas for spectrum shaping and other division methods.

[Effects of the Invention] As explained above, according to the present invention, the BTF of the transmitting device
Spectrum shaping is performed by the SAW filter of the receiving device, resulting in a synthesized spectrum shaping.

Here, in the synthesized spectrum shaping, the characteristics of each filter are combined, and the divided characteristics satisfying the Nyquist's first criterion are combined to satisfy the Nyquist's first criterion. Further, the SAW filter of the receiving device is provided before the detector in the intermediate frequency band, and unnecessary waves can be accurately removed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the invention, and FIG. 2 is a block diagram of another embodiment of the invention. 3.31, 32... Binary transversal filter 4... Two-phase phase modulator 5... Modulation section 6.9
...Intermediate frequency transmission path 7...Transmitter section 8...Receiver section 10...SAW filter 11...2-phase phase detector 18...Transmission logic circuit 19...4-phase phase modulator 20...4-phase phase detector 21...Reception logic circuit 100, 100A...Transmission device 200
, 200^...receiving device

Claims (1)

[Claims] It consists of a transmitting device and a receiving device, and the transmitting device is provided with a binary transversal filter in the baseband band, while the receiving device is provided with a surface acoustic wave filter in the intermediate frequency band, and the binary transversal filter and the surface 1. A digital radio system characterized in that an elastic wave filter is divided into characteristics satisfying Nyquist's first criterion by spectrum shaping.