JP2751667B2 - Cellular receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellular receiver used for a mobile communication device such as an automobile telephone, and more particularly to a cellular receiver capable of improving intermodulation characteristics.

[0002]

2. Description of the Related Art In a cellular system, a wide area is divided into small cells, and a base station is provided for each of the cells to communicate with a mobile station such as a car telephone while effectively utilizing the frequency. It has become so. FIG. 2 shows a configuration of a conventional cellular receiver used in this cellular system. Only the reception wave of the reception input wave input from the antenna 1 passes through the transmission / reception splitter 2, and the reception wave is amplified by the high-frequency amplifier 3, and then the high-frequency filter 4 attenuates the waves other than the reception frequency band. . The received wave that has passed through the filter 4 is transmitted to the first mixer 5 and the first mixer 5 that constitute the first frequency converter.
After being converted to the first intermediate frequency by the local oscillation circuit 6 and passing through the intermediate frequency filter 7, it is converted to the second intermediate frequency by the second mixer 8 and the second local oscillation circuit 9 constituting the second frequency converter. You. The second intermediate frequency is demodulated by the demodulation circuit 11 after the gain is increased by the second intermediate frequency amplifier 10 to a level at which the demodulation circuit 11 operates. The demodulated signal is amplified by the low frequency amplifier 12 and an audio output is obtained from the speaker 13.

[0003] In addition, this type of cellular receiver is provided with an electric field strength detection circuit 14 for detecting the electric field strength of a received input wave by converting the electric field strength into a voltage and monitoring the received electric field strength. The SAT signal detection circuit 15 detects a base station determination signal (SAT signal) sent from the base station, and constantly determines that the base station is in a communication state. In addition,
The antenna 1 is also connected to a transmitter.

[0004]

In the above-mentioned conventional cellular receiver, the first type is used in order to improve the receiving sensitivity characteristic.
The conversion gain of the mixer 5 is increased. However, when two interfering waves are input in addition to the desired received signal, a problem arises in that intermodulation distortion increases due to a high conversion gain and intermodulation characteristics deteriorate. Therefore, there has been proposed a receiver in which the conversion gain of the first mixer 5 is reduced to reduce the intermodulation distortion and improve the intermodulation characteristics. However, it is said that the high-frequency gain decreases and the reception sensitivity characteristics deteriorate. The problem starts to happen in reverse.

The present invention has been proposed to solve such problems of the conventional technology, and has as its object to propose a cellular receiver which can improve both the receiving sensitivity characteristic and the intermodulation characteristic. .

[0006]

SUMMARY OF THE INVENTION In order to achieve this object, the present invention provides a cellular receiver for a mobile station in which mobile communication is performed with a base station by a cellular system. A receiving field intensity detecting circuit for detecting, and a transistor mixer having a large conversion gain provided in a first frequency converter for converting a received input wave into a first intermediate frequency
Mixer consisting of: and a double rose having a small conversion gain
A second mixer comprising a first mixer and a second mixer, and a high-frequency switch for selectively switching and inputting a reception input wave to the first mixer and the second mixer, and a detection output of the reception electric field strength detection circuit. When it is determined that the electric field strength of the received input wave is small , the high-frequency switch is switched to the first mixer side, and when it is determined that the electric field strength of the received input wave is large, the high-frequency switch is switched to the second mixer. It has a configuration including a control circuit for switching to the mixer side.

Further, in a cellular receiver for a mobile station in which mobile communication is performed with a base station by a cellular system, a reception electric field intensity detection circuit for detecting an electric field intensity of a reception input wave; A base station signal detection circuit for detecting a base station determination signal for constantly determining that the mobile station is in communication with the base station, and a first frequency converter for converting a received input wave into a first intermediate frequency A first mixer having a large conversion gain and a second mixer having a small conversion gain, and a high-frequency switch for selectively switching and inputting a received input wave to the first mixer and the second mixer. , enter the detection output of the received field strength detection circuit and the base station signal detection circuit, the first said high-frequency changeover switch when the electric field strength of the received input wave is determined to be smaller than the predetermined level Mixer side switching, the larger the base station determines signal than the electric field strength is constant level of the received input wave is unable to detect the base station signals when it is not detected determine the
And a control circuit for switching the high-frequency switch to the second mixer side.

[0008]

According to the above configuration, when the received electric field strength is small, the receiving sensitivity characteristic can be enhanced by switching to the transistor mixer side having a large conversion gain.
Further, when the received field strength is large is small Da of conversion gain
By switching to the bull balanced mixer side, the intermodulation characteristics can be improved more than the reception sensitivity characteristics.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the cellular receiver according to the present invention will be described below in detail with reference to the drawings. The same parts as those of the conventional example are denoted by the same reference numerals and described. FIG.
FIG. 1 shows an embodiment of this cellular receiver. In this figure,
Only the reception wave of the reception input wave from the antenna 1 passes through the transmission / reception branching filter 2 and is amplified by the high-frequency amplifier 3. Then, the waves other than the reception frequency band are attenuated by the high-frequency filter 4 in the next stage. The received wave that has passed through the high-frequency filter 4 is sent to a first first mixer 18 having a large conversion gain or a second first mixer 19 having a small conversion gain via a high-frequency switch 17 that is switched by a control circuit 16 described later. Is entered. These first mixers 18 and 19 forming a part of the first frequency converter are provided with the first
The local oscillation frequency is supplied via a switch 17. Second
The first mixer 19 is composed of a double balanced mixer,
Although the conversion gain is smaller than that of the first first mixer 18 composed of a transistor mixer, it is excellent in intermodulation characteristics.

The signal converted to the first intermediate frequency by the first mixer 18 and the first local oscillation circuit 6 or the first mixer 19 and the first local oscillation circuit 6 is transmitted to the second The signal is converted into a second intermediate frequency by the mixer 8 and the second local oscillation circuit 9 and amplified by the intermediate frequency amplifier 10. The second intermediate frequency signal amplified by the intermediate frequency amplifier 10 is demodulated into a low frequency signal by the demodulation circuit 11, and the low frequency signal is amplified by the low frequency amplifier 12 and
3 outputs a voice.

In the electric field strength detection circuit 14 connected to the intermediate frequency amplifier 10, the electric field strength of the received input wave is converted into a voltage and taken out, and the detection output is supplied to a control circuit 16. The SAT signal detection circuit 15 to which the demodulated output is supplied detects the SAT signal sent from the base station, and supplies the detected output to the control circuit 16.

In the cellular receiver having such a configuration, when it is determined based on the detection output of the electric field intensity detection circuit 14 that a received input wave with a weak electric field intensity is being received, the signal is output from the control circuit 16. The high-frequency switch 17 is switched by the switching control signal to be connected to the first mixer 18. In addition, electric field strength detection circuit 1
If the SAT signal is not detected by the SAT signal detection circuit 15 in spite of the fact that the reception electric field strength detected in Step 4 is equal to or higher than a certain value, the control circuit 16 generates two interference signals in addition to the desired reception signal. When a wave is input, intermodulation distortion occurs and it is determined that the SAT signal cannot be detected, and the high frequency switch 17 is switched to the first mixer 19 side. Thus, when the received electric field strength is below a certain value, the first mixer 18 having a large conversion gain can be used, and the deterioration of the reception sensitivity characteristic can be prevented more than the intermodulation characteristic.

On the other hand, if intermodulation distortion occurs when the received electric field strength is above a certain value, the first intermodulation characteristic is excellent.
Since the mixer 19 can be used, the intermodulation characteristics can be improved more than the reception sensitivity characteristics.

The high-frequency switch 17 may be switched based only on the detection output of the electric field strength detection circuit 14 without referring to the detection output of the SAT signal detection circuit 15.

[0015]

As described above, according to the present invention, the reception sensitivity characteristic can be improved in a place where the reception electric field strength is weak, and the intermodulation characteristic can be improved in a place where the reception electric field strength is strong and intermodulation distortion occurs. Therefore, there is an effect that the reception characteristics of a cellular receiver used for a car phone or the like can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a cellular receiver according to the present invention.

FIG. 2 is a block diagram showing a conventional cellular receiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 Transmitting / receiving splitter 3 High frequency amplifier 4 High frequency filter 6 1st local oscillation circuit 7 Intermediate frequency filter 8 2nd mixer 9 2nd local oscillation circuit 10 2nd intermediate frequency amplifier 11 Demodulation circuit 12 Low frequency amplifier 13 Speaker 14 Electric field Intensity detection circuit 15 SAT signal detection circuit 16 Control circuit 17 High frequency changeover switch 18 First mixer with large conversion gain 19 First mixer with small conversion gain

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04B 1/10-1/28 H03D 7/00 H04B 7/24-7/26 H04B 7/00-7 / 38 H04M 1/00

Claims (3)

(57) [Claims] 1. A cellular receiver for a mobile station in which mobile communication is performed with a base station by a cellular system, a reception electric field intensity detection circuit for detecting an electric field intensity of a reception input wave, From a transistor mixer having a large conversion gain provided in a first frequency converter for converting to an intermediate frequency
Small Double balance between the first mixer and conversion gain comprising
A second mixer composed of a domixer, a high-frequency switch for selectively switching and inputting a reception input wave to the first mixer and the second mixer, and a detection output of the reception electric field strength detection circuit, When it is determined that the electric field strength of the received input wave is small , the high-frequency switch is switched to the first mixer side, and when it is determined that the electric field strength of the received input wave is large, the high-frequency switch is switched to the second mixer. Control circuit switching to mixer side
A cellular receiver comprising a path . 2. A cellular receiver for a mobile station in which mobile communication is performed with a base station by a cellular system, a reception electric field intensity detection circuit for detecting an electric field intensity of a received input wave, A base station signal detection circuit for detecting a base station determination signal for constantly determining that the mobile station is in communication with the base station; a first frequency converter for converting a received input wave into a first intermediate frequency A first mixer having a large conversion gain and a second mixer having a small conversion gain, and a high-frequency switch for selectively switching and inputting a received input wave to the first mixer and the second mixer. the reception field strength detection circuit and the base station signal inputs the detection output of the detection circuit, the first said high-frequency changeover switch when the electric field strength of the received input wave is determined to be smaller than the predetermined level Switching the mixer side, and determines that it can not detect the base station signal when the field strength of the received input wave is large not detected the base station determination signal than a certain level <br/> the high frequency of the changeover switch the second A cellular receiver comprising a control circuit for switching to a mixer side. 3. The cellular receiver according to claim 2, wherein said first mixer comprises a transistor mixer, and said second mixer comprises a double-balanced mixer.