JPH07326980A - Mobile communication receiver - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the demodulation characteristics of a mobile communication receiver and to reduce the manufacturing cost and size of the receiver. [Structure] This receiver is used for mobile communication using the super-heterodyne system. This receiver is a mixer (1
1, 13) and an intermediate frequency filter (12, 14), for example, receives a quadrature-modulated received signal.
The output of the intermediate frequency filter 14 is given to the AGC circuit 19 and gain controlled. The output of the AGC circuit is quadrature-detected by the quadrature detector 20 to be an I signal and a Q signal (that is, a baseband signal). This baseband signal is filtered by the baseband filter 21 and given to the demodulator 22 via the A / D converter 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication receiver, and more particularly to a receiver used in a digital radio communication device.

[0002]

2. Description of the Related Art First, a receiver used in a digital wireless communication device will be described with reference to FIG.

For example, a super-heterodyne system is used in a conventional receiver, and an antenna (not shown) is used.
The high-frequency signal (RF signal, for example, quadrature modulation signal) received via is given to the first mixer 11 (this RF signal is, for example, a quadrature modulation wave). And R
The F signal is converted by the first mixer 11 into a first intermediate frequency signal. This first intermediate frequency signal is attenuated by the first intermediate frequency (IF) filter 12 to eliminate unnecessary waves out of the band
Of the second intermediate frequency signal.

The second intermediate frequency signal attenuates out-of-band unwanted waves by the second intermediate frequency filters 14 and 15, but an amplifier 16 is arranged between the second intermediate frequency filters 14 and 15. The amplifier 16 provides isolation.

The output from the second intermediate frequency filter 15 is amplitude-limited (limited) by the limiter amplifier 17, and the demodulator 1 is used as an amplitude-limited signal.
Given to 8. The demodulation device 18 has, for example, a quadrature detector (not shown) built therein, and the amplitude limit signal is quadrature detected to be an I signal and a Q signal, and then the A / D
It is A / D converted by a converter (not shown) and demodulated into demodulated signals (data).

In the receiver shown in FIG. 3, a first intermediate frequency filter 12 and a second intermediate frequency filter 14 are provided.
And 15 get a certain attenuation in the adjacent channel,
In this way, the adjacent and next adjacent channel selectivities are obtained.

[0007]

By the way, in a digital radio communication device (receiver), a predetermined amplitude characteristic within a band (for example, in a π / 4QPSK modulated wave, a so-called root / roll-off characteristic) is generated. It is required to be obtained and have flat group delay characteristics. Therefore, since the first intermediate frequency filter 12 and the second intermediate frequency filters 14 and 15 have flat amplitude characteristics and group delay characteristics within the band and obtain predetermined adjacent and next adjacent channel selectivities, they are large outside the band. The amount of attenuation is calculated.

Generally, a so-called ceramic filter is used as the second intermediate frequency filter. With this ceramic filter, it is extremely difficult to obtain large attenuation in the adjacent channel without deteriorating the amplitude and group delay characteristics in the band. Therefore, even in the first intermediate frequency filter, a large attenuation in the adjacent channel is required without deterioration of the characteristic within the band, and as a result, the first intermediate frequency filter is required to have a strict characteristic. As described above, when strict characteristics are required for the first intermediate frequency filter, considering that the first intermediate frequency is generally high in frequency, tuning adjustment is required, which increases the manufacturing cost. There is a problem.

As described above, strict characteristics are required for each of the first and second intermediate frequency filters, and in order to obtain desired characteristics, it is necessary to arrange filters in multiple stages as described above. However, there is a problem that not only the receiver itself becomes expensive, but also the mounting space must be wide.

Further, in the conventional receiver, there is a problem that the deterioration of the filter characteristic in the pass band cannot be avoided, and as a result, the demodulation characteristic is deteriorated.

An object of the present invention is to provide a mobile communication receiver which is inexpensive to manufacture, small in size, and low in cost.

Another object of the present invention is to provide a mobile communication receiver having good demodulation characteristics.

[0013]

According to the present invention, mixing means for use in mobile communication using the superheterodyne system for receiving a received signal to generate an intermediate frequency signal and a filter for filtering the intermediate frequency signal are provided. A receiver for generating a demodulated signal from the filter signal, the receiver including a filter means for outputting a signal, the controller automatically receiving the filter signal and controlling the filter signal level to a predetermined amplitude level to generate an amplified signal. Gain control means, baseband signal generation means for converting the amplified signal to a baseband signal,
Baseband filter means for filtering the baseband signal to output a baseband filter signal,
A mobile communication receiver having a predetermined dynamic range and demodulating means for demodulating the baseband filter signal to obtain the demodulated signal is obtained.

[0014]

In the present invention, since the baseband signal is filtered to obtain the adjacent and next adjacent channel selectivities, strictness is not required for the characteristics of the filter for the intermediate frequency signal, and a small filter is used. Not only can it be achieved, but also the demodulation characteristics can be improved, and as a result, the manufacturing cost is low, and the size and cost can be reduced.

[0015]

EXAMPLES The present invention will be described below with reference to examples.

Referring to FIG. 1, in the digital communication receiver shown in FIG. 1, the same components as those of the receiver shown in FIG. 3 are designated by the same reference numerals, and a quadrature modulation signal is shown as an RF signal. Shall be given to the receiver. Figure 3
As can be understood from the description of FIG. 1, in the first intermediate frequency signal in FIG. 1, unnecessary waves separated by more than the next adjacent channel out of the band are attenuated by the first intermediate frequency filter 26 and are given to the second mixer 13. Where it is converted to a second intermediate frequency signal. The second intermediate frequency signal is attenuated by the second intermediate frequency filter 27 at a frequency equal to or higher than the higher harmonic wave and is given to the AGC circuit 19.

The AGC circuit 19 is a variable gain amplifier 19
It has a, a level detector 19b, a reference level setter 19c, and a comparator 19d, and the second intermediate frequency signal is amplified by the variable gain amplifier 19a and output as an amplified signal. Then, this amplified signal is given to the quadrature detector 20 and the level detector 19b. The level detector 19b detects the amplitude level of the amplified signal and outputs a level detection signal indicating the amplitude level value (voltage value). On the other hand, the reference level setter 19c is set with the reference level indicating the reference voltage value.
Outputs a reference level signal.

The level detection signal and the reference level signal are given to the comparator 19d, and the comparator 19d outputs a gain control voltage signal based on the level detection signal and the reference level signal. That is, the comparator 19d compares the level detection signal with the reference level signal, and based on the comparison result, the gain of the variable gain amplifier 19a is adjusted so that the amplitude level of the amplified signal becomes constant (preset reference value). Will be controlled. Specifically, the variable gain amplifier 19 is arranged so that the level detection signal and the reference level signal are equal.
The gain of a will be controlled.

The quadrature detector 20 receives the amplified signal and performs quadrature detection to obtain a baseband signal (that is, an I signal and a Q signal).
Signal). Then, this baseband signal is given to the baseband filter 21. The baseband filter 21 removes unnecessary waves outside the band such as adjacent channels from the baseband signal, and the baseband signal has a predetermined characteristic (for example, when the modulation signal is modulated by π / 4QPSK, the root roll-off is performed). It is filtered by a characteristic) and is output as a baseband filter signal (filter I signal and filter Q signal). This baseband filter signal is first converted into a digital signal by the A / D converter 25 and then given to the demodulator 22 where it is demodulated into a demodulated signal (data) (note that
A / D converter 25 and demodulator 22 constitute demodulation means).

By the way, since the ideal baseband filter 21 can be realized, the attenuation of adjacent and next adjacent channels can be surely obtained. The AGC circuit 19 controls the amplified signal to an amplitude level where saturation does not occur in the quadrature detector 20, and therefore the baseband filter 2
In No. 1, the attenuation characteristic does not deteriorate. In addition, A
The / D converter 25 has a baseband filter signal level of
For example, it has a dynamic range that operates accurately even if it is attenuated to 60 dB.

For example, the next-adjacent-channel selectivity is such that the interfering wave in the next-adjacent channel is 60 dB with respect to the desired wave.
Assuming that the specifications have sensitivity to the desired wave even when the signal is large, a signal whose interfering wave is 60 dB larger than the desired wave is A
When input to the GC circuit 19, the AGC circuit 19 will adjust the level of the interfering wave to a predetermined amplitude. Therefore, when the interfering wave is removed from the baseband signal by the baseband filter 21, a desired wave (baseband filter signal) 60 dB lower than the predetermined amplitude is generated by the A / D converter 2.
5 will be input. However, as mentioned above,
By designing the A / D converter 25, the demodulator 22 will operate correctly even if the baseband filter signal is attenuated by 60 dB.

As can be easily understood from the above description,
As the first and second intermediate frequency filters, it is possible to use filters that do not require attenuation in adjacent and next adjacent channels. That is, it is sufficient for the first and second intermediate frequency filters 26 and 27 to remove an interfering wave that is far from the desired wave frequency, and the second intermediate frequency filter may be a low-pass filter, which is close to the desired wave frequency. Then, there is no need to increase the amount of attenuation. As a result, as the first and second intermediate frequency filters, those having a wide pass band may be used, and the number of stages can be reduced to roughen the characteristics.
It can be composed of simple things such as filters. Therefore, as the first and second intermediate frequency filters, unadjusted filters can be used. As a result, the adjustment cost is low and a small filter is sufficient. That is, the mounting space is small and the receiver can be inexpensive.

In addition, the attenuation of the pass band, that is, the selection of the desired wave is substantially determined only by the base band filter, so that the demodulation characteristic is hardly deteriorated.

FIG. 2 shows another embodiment of the receiver according to the present invention. In the embodiment shown in FIG. 2, a level detector 23 is provided instead of the level detector 19b shown in FIG. 1, and the level detector 23 is connected to the output side of the baseband filter 21. That is, the level detector 23 detects the amplitude level of the baseband filter signal, generates a level detection signal, and supplies it to the comparator 19d. As can be understood from FIG. 2, in this embodiment, as a result of performing the AGC operation based on the desired wave, the desired wave is adjusted to a predetermined level in the AGC circuit 19 regardless of the interfering wave. . Therefore, the A / D converter 2 shown in FIG.
The dynamic range of 4 is the same as that of the conventional example described in FIG. 3 (since the A / D converter shown in FIG. 2 has a different dynamic range from the A / D converter shown in FIG. 1, that is, Since the dynamic range of the A / D converter shown in FIG. 2 is smaller than that of the A / D converter shown in FIG. 1, reference numeral 24 in FIG.
A D converter is shown. Also in FIG. 2, it goes without saying that the A / D converter 24 and the demodulator 22 constitute demodulation means).

[0025]

As described above, according to the present invention, since the baseband signal is filtered to obtain the adjacent and next adjacent channel selectivity, the filter characteristics for the intermediate frequency signal are not required to be strict. Moreover, a small and inexpensive filter can be used. Further, it is possible to easily realize a filter having a wide band and no deterioration of the amplitude characteristic group delay characteristic, and as a result, there is an advantage that the demodulation characteristic is hardly deteriorated. Furthermore, there is an effect that a small-sized receiver can be provided at a low manufacturing cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a mobile communication receiver according to the present invention.

FIG. 2 is a block diagram showing another embodiment of a mobile communication receiver according to the present invention.

FIG. 3 is a block diagram showing a conventional mobile communication receiver.

[Explanation of symbols]

 11, 13 Mixer 12, 14, 15 Intermediate frequency filter 16 Amplifier 17 Limiter amplifier 18 Demodulator 19 AGC circuit 20 Quadrature detector 21 Baseband filter 22 Demodulator 24, 25 A / D converter

Claims (4)

[Claims] 1. A mixing means used for mobile communication using the super-heterodyne system, for receiving a received signal to generate an intermediate frequency signal, and a filtering means for filtering the intermediate frequency signal and outputting a filter signal. A receiver for generating a demodulated signal from the filter signal, the automatic gain control means for receiving the filter signal and controlling the filter signal level to a predetermined amplitude level to generate an amplified signal; Baseband signal generating means for converting into a band signal, baseband filter means for filtering the baseband signal and outputting a baseband filter signal, and demodulating the baseband filter signal having a predetermined dynamic range A receiver for mobile communication, comprising: a demodulation unit that obtains the demodulated signal. 2. The mobile communication receiver according to claim 1, wherein the received signal is a quadrature modulated signal, and a quadrature detector is used as the baseband signal generating means.
The mobile communication receiver, wherein the baseband signal includes an I signal and a Q signal. 3. The mobile communication receiver according to claim 1, wherein the automatic gain control means receives the filter signal and outputs the amplified signal.
Level detection means for receiving one of the amplified signal and the baseband filter signal as an input signal, detecting the amplitude level of the input signal and transmitting a level detection signal, and a reference indicating a preset reference amplitude level. Control means for receiving the level signal and the level detection signal, obtaining an error between the reference level signal and the level detection signal, and controlling the variable gain amplifying means based on the error. Mobile communication receiver. 4. The mobile communication receiver according to claim 3, wherein when the level detecting means receives the amplified signal as the input signal, the demodulating means operates as the predetermined dynamic range. When the first dynamic range is set and the level detection means receives the baseband filter signal as the input signal, the demodulation means is set to the second dynamic range as the predetermined dynamic range. The receiver for mobile communication is characterized in that the first dynamic range is larger than the second dynamic range.