JPH09321691A - Radio telephone equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable operating at the plural cellular telephone systems of different band width and to prevent degradation of the reception bit error rate at the time of phasing by increasing the gain of an IF amplifier circuit at a receiver rather than in the case of wide band when switching the IF band to a narrow band with. SOLUTION: When the IF band width is designated to a wide band, changeover switches 4 and 5 are controlled by an IF band width switching control signal 9 so as to be switched to the side of a wide band IF filter 2. In such a switching state of changeover switches 4 and 5, a received signals is passed from a reception mixer circuit 1 to the wide band IF filter 2, amplified by an IF amplifier 7, demodulated by a demodulator 8 and converted to received voice or data. At such a time, the gain of the IF amplifier 7 is set so as to be optimum at the time of a wide band. When the IF band width is designated to a narrow band, the switches 4 and 5 are controlled by the control signal 9 so as to be switched to a side of a narrow band IF filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a configuration of an intermediate frequency circuit of a receiver such as a mobile phone, and more particularly, to a wireless system capable of using both systems in two cellular phone systems having different IF (intermediate frequency) bandwidths. The present invention relates to the configuration of an intermediate frequency circuit of a telephone device.

[0002]

2. Description of the Related Art As the prior art, Japanese Patent Laid-Open No. 57-1843
There is a receiver IF bandwidth switching control device described in Japanese Patent No. 28. FIG. 2 shows the configuration of this conventional device. In FIG. 2, 11 is a wide band BPF (Bandpass Fi).
lter), 13 is a narrow band BPF, 12 and 14 are changeover switches, and 15 is an IF (Intermediate FPF).
frequency) level detector, 16 is an OR gate,
Reference numeral 17 is an AM detector, and 18 is a 9 KHz beat level detector.

In such a receiver IF bandwidth switching control device, the AM detector 17 detects the beat component between the adjacent signal and the desired wave signal, and detects the frequency interval of 9 KHz between the adjacent channel and 9 KHz. When the beat level detector 18 further selects and detects, and when the detection level exceeds a certain value, the changeover switches 12 and 14 are switched to the narrow band BPF.
By controlling so as to switch to the 13 side, the IF bandwidth has a narrow band characteristic to eliminate interference due to adjacent waves.

When the received electric field strength falls below a predetermined level by the IF level detector 15, similarly, the changeover switches 12 and 14 are controlled so as to be switched to the narrow band BPF 13 side, and the IF bandwidth is changed. As a narrow band characteristic, S / N is improved at a low electric field.

As described above, the conventional technique shown in FIG. 2 has the advantages of switching the IF bandwidth to a narrow band when interference occurs and at a low electric field to eliminate interference and improve the S / N of the desired signal.

However, the configuration of the conventional example of FIG. 2 has a problem that it cannot provide an intermediate frequency circuit that can be used in both two cellular telephone systems having different IF bandwidths.

An example of an apparatus that solves such a problem is shown in FIG.
Shown in 1 is a reception mixer circuit, 2 is a wide band IF filter, 3 is a narrow band IF filter, 4 and 5 are changeover switches, 7 is an intermediate frequency amplifier circuit (IF amplifier), 8 is a demodulator (discriminator), and 9 is an IF. 3 shows a bandwidth switching control signal. AMPS (Adv
anced Mobile Phone service
e) System and narrow AMPS system (hereinafter NAM
In a radiotelephone device typified by a dual system compatible mobile phone capable of operating in both systems (PS system), when a base station specifies an AMPS system having a wide IF bandwidth, a control not shown I from the department
By the F bandwidth switching control signal 9, the changeover switch 4,
5 is controlled to switch to the wide band IF filter 2 side. The received signal is sent from the receiving mixer circuit 1 to the wideband IF.
After passing through the filter 2, the signal is amplified by the IF amplifier 7, demodulated by the demodulator 8 and converted into received voice or data.

On the other hand, when the base station specifies the NAMPS system having a narrow IF bandwidth, the IF bandwidth switching control signal 9 similarly causes the changeover switches 4 and 5 to operate.
Are controlled to switch to the narrow band IF filter 3 side. The received signal is sent from the receiving mixer circuit 1 to the narrow band IF.
After passing through the filter 3, the signal is amplified by the IF amplifier 7, demodulated by the demodulator 8 and converted into received voice or data.

[0009]

In the conventional circuit configuration shown in FIG. 3, when operated in a narrow band cellular telephone system, the received bit error rate is deteriorated particularly in the presence of fading and the connection rate is deteriorated. There was a problem.

This is the case where the IF bandwidth is both narrow band and wide band, and since the IF amplifier 7 is commonly used,
This is because, when the gain of the IF amplifier 7 is set to be optimum in a wide band, the gain of the IF amplifier is insufficient in a narrow band, and good receiver performance cannot be exhibited when the input electric field changes such as fading.

Generally, in the narrow band, the thermal noise is reduced due to the narrow band, so that the total gain of the receiver is required to be larger than that of the wide band.

On the other hand, when the gain of the IF amplifier 7 is set to be optimum in a narrow band, the gain of the IF amplifier becomes excessive in a wide band, and the saturation point of the amplifier occurs even in a medium to strong input electric field. However, in the case of a medium to strong input electric field, there is a drawback that the deterioration of the reception distortion rate occurs.

The object of the invention is to eliminate the above-mentioned drawbacks,
An object of the present invention is to provide a wireless telephone device that can operate in a plurality of cellular telephone systems having different F bandwidths.

[0014]

In a radiotelephone device operating in a plurality of different cellular telephone systems, the IF bandwidth of the receiver is switched to wideband and narrowband, and the IF bandwidth is switched to narrowband. In this case, it has means for increasing the gain of the IF amplifier circuit of the receiver as compared with the case of the wide band.

Specifically, when the path of the changeover switch for changing the IF bandwidth is changed to the narrow band side, the gain of the IF amplifier is added to the gain of the IF amplifier in the wide band, so that the gain in the narrow band is obtained. Is increased over the wide band, and the optimum gain can be set for the narrow band.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a wireless telephone device of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of one embodiment of the present invention. This wireless telephone device has a configuration in which an IF amplifier 6 is added to the narrow band IF filter 3 side in addition to the configuration of the conventional example of FIG. That is, the receiving mixer circuit 1 is provided, and its output is connected to the contact 4 a of the changeover switch 4. The contact 4b of the changeover switch 4 is connected to the contact 5b of the changeover switch via the narrow band IF filter 3 and the IF amplifier 6. Further, the contact 4c of the changeover switch 4 is connected to the contact 5c of the changeover switch through the broadband IF filter 2.

The contact 5a of the changeover switch 5 is connected to the input of the IF amplifier 7, and the output of the amplifier 7 is connected to the input of the demodulator (discriminator) 8. The changeover switches 4 and 5 are controlled by the IF bandwidth changeover control signal 9.
The switching is controlled.

Next, the operation of this embodiment will be described.

When the IF band width is designated by the base station (not shown) as a wide band, the changeover switches 4 and 5 cause the wide band IF filter 2 by the IF band width change control signal 9.
It is controlled to switch to the side. That is, in the changeover switch 4, the contacts 4a and 4c are connected, and in the changeover switch 5, the contacts 5a and 5c are connected.

In such a switching state of the changeover switches 4 and 5, the reception signal is amplified from the reception mixer circuit 1 through the wide band IF filter 2 and by the IF amplifier 7,
It is demodulated by the demodulator 8 and converted into received voice or data. Here, the gain of the IF amplifier 7 is set to be optimum in a wide band.

On the other hand, when the IF bandwidth is designated as a narrow band by the base station, the IF bandwidth switching control signal 9 causes
The changeover switches 4 and 5 are controlled so as to switch to the narrow band IF filter 3 side. That is, in the changeover switch 4, the contacts 4a and 4b are connected, and the changeover switch 5
In, the contact 5a and the contact 5b are connected.

In such a switching state of the change-over switches 4 and 5, the IF gain in the narrow band is increased because the gain of the IF amplifier 6 is added to the gain of the IF amplifier 7 in the wide band. However, it is possible to set the optimum gain in a narrow band. The reception signal in the narrow band passes from the reception mixer circuit 1 through the narrow band IF filter 3 to the IF amplifier 6
Amplified by 7 and 7, demodulated by the demodulator 8 and converted into received voice or data.

[0024]

As described above, according to the present invention, when the IF bandwidth of the same radio telephone device is switched to operate in a plurality of cellular telephone systems having different IF bandwidths,
Since the gain of the amplifier can be set to be optimum according to the IF bandwidth, there is an effect that the received bit error rate in the presence of fading does not deteriorate due to insufficient total gain of the receiver.

The present invention also has an advantage of preventing the deterioration of the reception distortion rate in the strong input electric field due to the excessive gain of the IF amplifier.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a conventional wireless telephone device.

FIG. 3 is a block diagram showing a conventional wireless telephone device.

[Explanation of symbols]

 1 Receiving Mixer Circuit 2 Wideband IF Filter 3 Narrowband IF Filter 4,5 Switching Switch 6,7 Intermediate Frequency Amplifier Circuit (IF Amplifier) 8 Demodulator (Discriminator) 9 IF Bandwidth Switching Control Signal 11 Wideband BPF 12,14 Changeover switch 13 Narrow band BPF 15 IF level detector 16 OR gate 17 AM detector 189 KHz beat level detector

Claims (5)

[Claims] 1. A radiotelephone device comprising an intermediate frequency amplifier circuit, which is capable of operating in a plurality of different cellular telephone systems by switching the intermediate frequency bandwidth of a receiver between a wide band and a narrow band. A radiotelephone device comprising means for increasing the gain of the intermediate frequency amplifier circuit when the frequency bandwidth is switched to a narrow band as compared with the case of a wideband. 2. A reception mixer circuit for converting a reception signal to an intermediate frequency, a first changeover switch for changing over and outputting the output of the reception mixer circuit, and a first output terminal of the first changeover switch. A narrow band intermediate frequency filter, a first intermediate frequency amplifier circuit connected to the narrow band intermediate frequency filter, a wide band intermediate frequency filter connected to a second output terminal of the first changeover switch, A second changeover switch for switching and outputting the output of the first intermediate frequency amplifier circuit and the output of the wideband intermediate frequency filter; and a second changeover switch connected to an output terminal of the second changeover switch.
And a demodulation circuit that demodulates the output of the second intermediate frequency amplification circuit. 3. The first and second changeover switches,
When the intermediate frequency band width is designated as a wide band, the wide band intermediate frequency filter is connected between the first changeover switch and the second changeover switch, and the intermediate frequency band width is designated as a narrow band. In this case, the narrow band intermediate frequency filter and the first intermediate frequency amplifier circuit are switched between the first changeover switch and the second changeover switch. The wireless telephone device according to claim 2. 4. The gain of the second intermediate frequency amplifier circuit is:
4. The wireless telephone device according to claim 3, wherein the wireless telephone device is set to be optimum when the intermediate frequency bandwidth is designated as a wide band. 5. The radiotelephone apparatus according to claim 4, wherein the switching of the first and second changeover switches is performed by an instruction from a base station.