JP3248179B2 - Wireless receiver - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio receiving apparatus, and more particularly to a radio receiving apparatus that receives and demodulates a high-frequency signal modulated by digital data and corrects the demodulated digital data by an equalizer. Related to the device.

[Conventional technology]

Conventionally, this type of radio receiving apparatus has been configured as shown in a block diagram of FIG. In FIG. 2, a high-frequency reception signal modulated by digital data is input to an antenna 1. The received signal is a radio frequency (RF) 2, which receives and amplifies the received signal and converts the frequency to an intermediate frequency signal.
The intermediate frequency signal is band-limited by a band-pass filter (IF-FIL) 31, passed through an intermediate frequency unit (IF) 3 amplified by an amplifier (IF-AMP) 33, and demodulated to digital data by a demodulation unit (DEM) 4. Is done. The demodulated demodulated data is corrected by an equalizer (EQL) 5 for the effects of multipath fading or the like generated on the radio channel of the received signal, and output as a data signal (DATA) 6. On the other hand, the intermediate frequency signal branched from the amplifier 33 in the intermediate frequency section 3 is input to an electric field intensity detector (LEV DET) 34 for detecting the level thereof, and an electric field intensity signal (LEVEL) which is reception level information of a reception signal.
7 is obtained. The electric field strength signal 7 is input to the equalizer 5 as a control signal thereof, and is also output as a received electric field monitor signal outside the apparatus.

[Problems to be solved by the invention]

In general, in the above-described radio receiving apparatus, the band of the signal input to the demodulation unit is often narrower than the signal band of the reception signal in order to reduce the noise input to the demodulation unit. This band limitation is mainly performed by a band-pass filter in the intermediate frequency section. Assuming that the pass band of the band-pass filter is B and the symbol rate of the received signal is 1 / T (bit interval T of data), the product of B and T, that is, the degree of band limitation is represented by BT. If BT = 0.5, the response to a change in the amplitude of the received signal at a speed corresponding to the symbol rate is halved.

By the way, when the equalizer corrects the deterioration of the amplitude and the waveform of demodulated data due to the multipath fading, the amplitude fluctuation caused by the multipath fading,
That is, it is necessary to capture the fluctuation of the amplitude for each symbol as information. In the above-described conventional radio receiving apparatus, electric field strength detection is performed using a signal that has passed through a band-pass filter, and the obtained electric field strength signal is input to an equalizer as information on amplitude fluctuation.

For this reason, if the band limitation is strengthened for noise reduction, it is difficult to obtain correct amplitude fluctuation information, and the equalizer cannot perform an appropriate amplitude equalization operation.

[Means for solving the problem]

A radio receiving apparatus according to the present invention receives and amplifies a high-frequency signal modulated by digital data and converts the frequency to an intermediate-frequency signal, and the intermediate-frequency signal is input and band-limited by a first band-pass filter. An intermediate frequency unit that outputs an intermediate frequency signal and an electric field intensity signal indicating the reception level of the received high-frequency signal detected by the electric field intensity detector, and a demodulation unit that demodulates the band-limited intermediate frequency signal to demodulated data. An equalizing unit that corrects the demodulated data according to a change in the reception level of the received high-frequency signal based on the electric field strength signal, wherein the passband is wider than the passband of the first bandpass filter. An intermediate frequency signal branched from an input side of the first band-pass filter, and receiving the first band-pass signal with respect to a change in reception level; Outputs faithfully response signal than the signal that has passed through the filter, and a second band pass filter for input to said field intensity detector as a reception level detection target signal.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

 FIG. 1 is a block diagram of one embodiment of the present invention.

The high frequency received signal modulated by the digital data input from the antenna 1 is converted into an intermediate frequency signal by the high frequency unit 2 and input to the intermediate frequency unit 3. Here, the intermediate frequency signal is split into two, one of which is a bandpass filter 31.
And the other is input to the band-pass filter 32. The intermediate frequency signal is subjected to a band limitation of BT ≦ 1 (for example, BT = 0.6) by the band-pass filter 31 for noise reduction. The band-limited intermediate frequency signal is subjected to quadrature detection by the demodulation unit 4 and demodulated into digital data. The demodulated data is corrected by the equalizer 5 for data waveform deterioration due to multi-valve fading.

Degradation of demodulated data due to multipath fading
This occurs when high-frequency signals passing through wireless propagation paths having different delay times are combined, and becomes largest when the difference between the delay times is equal to the data bit interval T. At this time, the received signals may cancel each other, and the amplitude is greatly attenuated in 1-bit units. The equalizer 5 estimates the effect of multipath fading based on the amplitude change information and the phase change information obtained from the demodulated data subjected to the quadrature detection, and corrects the demodulated data. Therefore, it is necessary for the electric field strength signal 7 to give the change in the level of the received signal to the equalizer 5 faithfully.
That is, it must respond to a change in the symbol rate of the received signal at a speed. For example, the symbol rate is 300Kbp
Even if the input signal is s, the output signal of the band-pass filter 31 whose signal band is limited to BT = 0.6 becomes difficult to respond to an amplitude change having a frequency component of 180 KHz or more.

The phenomenon described above is shown in the response diagram of the electric field intensity signal in FIG. FIG. 3 (a) shows the true electric field strength of the received signal, indicating that there is attenuation over one symbol length (T). FIG. 3B shows a response to FIG. 3A when the received signal is band-limited to BT = 1, and FIG. 3C shows a response when BT <1.

In the embodiment shown in FIG. 1, a band-pass filter 32 is provided to be branched to the input side of a band-pass filter 31 for performing band limitation for demodulation. The pass band width of the band pass filter 32 is set to a value different from that of the band pass filter 31, for example, BT.
= 1. The electric field intensity detector 34 is connected to the band-pass filter 32, detects the electric field intensity level of the received signal based on a change in the required speed level, and inputs the detected electric field intensity signal 7 to the equalizer 5. . As a result, the equalizer 5 can faithfully obtain the amplitude change information irrespective of the band limitation of the demodulation intermediate frequency signal, and can perform appropriate amplitude and waveform equalization.

〔The invention's effect〕

As described above, the radio receiving apparatus according to the present invention provides a bandpass filter for detecting the electric field strength level separately from the bandpass filter for band limitation of the demodulated signal, so that the Information can be given accurately. As a result, the deterioration of the amplitude and waveform of demodulated data due to multipath fading and the like can be corrected by utilizing the capability of the equalizing unit, and the transmission signal error rate of the communication system using this wireless receiver is reduced and the line quality is improved. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a wireless receiving apparatus according to the present invention, FIG. 2 is a block diagram of a conventional wireless receiving apparatus,
FIG. 3 is a response diagram of the electric field intensity signal. 1 ... antenna, 2 ... high frequency part, 3 ... intermediate frequency part,
4 demodulation unit, 5 equalization unit, 6 data signal, 7
... electric field strength signal, 31, 32 ... band-pass filter, 33 ...
Amplifier, 34 ... Electric field strength detector.

Claims (1)

(57) [Claims] 1. A high-frequency section for receiving and amplifying a high-frequency signal modulated by digital data and converting the frequency into an intermediate-frequency signal, and an intermediate-frequency signal input with the intermediate-frequency signal and band-limited by a first band-pass filter And an intermediate frequency unit that outputs an electric field intensity signal indicating the reception level of the received high-frequency signal detected by the electric field intensity detector, and a demodulation unit that demodulates the band-limited intermediate frequency signal to demodulated data.
An equalizer that corrects the demodulated data according to a change in the reception level of the received high-frequency signal based on the electric field strength signal, wherein the passband is wider than the passband of the first bandpass filter. An intermediate frequency signal having a characteristic and branched from the input side of the first band-pass filter is input, and a signal more faithfully responding to a change in reception level than a signal having passed through the first band-pass filter is input. A wireless receiving apparatus, comprising: a second band-pass filter that outputs a signal to be input to the electric field intensity detector as a signal to be detected as a reception level.