JPH033425A - Radio transmitter/receiver - Google Patents

Abstract

PURPOSE:To suppress cross modulation distortion and to improve an S/N by dividing a reception signal into signals with different levels, and selecting the optimum output signal out of plural automatic gain controllers corresponding to the input level of the reception signal. CONSTITUTION:The radio transmitter/receiver includes a distributor 101 which distributes the reception signal to plural signals, plural attenuators 51, -51m which attenuate the levels of the plural signals from the distributor 101, and plural automatic gain controllers 521-52m, 52 which perform the automatic gain control of the output signals from the attenuators 51. Also, it is comprised by including a switch selection circuit 102 which switches and inputs either the output signals from the plural automatic gain controllers 52 based on the level of the reception signal inputted to the distributor 101. And output can be obtained by switching and controlling the automatic gain controllers 521-52m with the switch selection circuit 102 based on the information of the input level from a level detector 104. In such a way, it is possible to suppress the occurrence of the cross modulation and to keep the S/N satisfactorily without increasing the input of a first mixer excessively.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a wireless transmitting/receiving device that includes a transmitting section that transmits a predetermined signal to the outside, and a receiving section that receives a received signal from the outside in a superheterodyne manner. In particular, the present invention relates to a wireless transmitting/receiving device that can improve the signal-to-noise ratio and improve the signal chain.

(Prior Art) Conventionally, this type of wireless transmitter/receiver is used to transmit cable television (CATV) signals using microwaves. For receiving multiple TV channel signals, a device as shown in FIG. 2 is provided.

The wireless transmitter/receiver shown in FIG. 2 has the following configuration. That is, the transmitting section includes an input circuit 2 to which the transmitting terminal 1 is connected, an oscillation modulation circuit 3, an amplifier circuit 4, a bandpass filter 5, and a circulator 6. The transmission channel signal is transmitted from transmission terminal 1 to input circuit 2.
The oscillation modulation circuit 3. Amplification circuit 4. The signal is supplied to an external filter (not shown) via a bandpass filter 5° and a circulator 6.

On the other hand, the receiving section includes a circulator 6, a band rejection filter 7, an amplifier 8, a first mixer 9, a first local oscillator 10, an intermediate frequency amplifier 11, a distributor 12, a band filter 13 . ~1311 and a second mixture n t 4+ ~1
4, bandpass filters 15, to 153, and demodulator 16+
~16. % and output circuits 171-17. , second local oscillators 18t-18, and output terminal 19. ~19. The received signals of a plurality of receiving channels inputted from an external antenna (not shown) are passed through a circulator 6, a band-rejection filter 7 that removes the wraparound of the transmitting channel signal to the receiving channel, and an amplifier 8. Thereafter, the microwave is converted into a second intermediate frequency band by a first mixer 9 having a first local oscillator 10. Thereafter, the signal is amplified by an intermediate frequency amplifier 11 and distributed to n parts by a distributor 12. Bandpass filters 131-13. are supplied with the divided signals, and these signals are passed to second mixers 14.about.14. , the second intermediate frequency band (for example, 70 (MH
z) )). This second intermediate frequency signal is passed through the bandpass filter 15. ~151, demodulators 16t~161, output circuit 17. ~171, and the first channels from output terminals 19+~19, respectively.

The signals are output as signals of the second channel, . . . n-th channel.

FIG. 3 shows the arrangement of each signal of the above-mentioned transmission channel and reception channel on the microwave frequency.

As can be seen from the figure, these channels are equally spaced.

〔Problems to be solved〕

In the conventional device described above, a plurality of reception channels are commonly amplified by the amplifier 8.11 from the microwave to the intermediate frequency band. Therefore, those amplifiers 8.
11 and the input level to the first mixer 9 is high (when the input level to the amplifiers 8, 11 and the first mixer 9 is high, cross-modulation between the receiving channels caused by the nonlinear characteristics of the amplifiers 8, 11 and the first mixer 9 occurs as shown in FIG. This causes a drop in the reception channels arranged at equal intervals, deteriorating the signal-to-noise ratio (S/N).As a result, the saturation output level of the amplifiers 8 and 11 and the first mixer 9 increases. There was a problem in that thick (and good linearity) had to be used.

Furthermore, an amplifier 8. which constitutes these common reception parts.
11 or one part of the first mixer 9 breaks down, all of the plurality of receiving channels become disconnected, and there is also the problem that the overall reliability deteriorates.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a wireless transmitting/receiving device with improved S/N ratio and good communication chain even when a high received signal is input.

[Means for solving problems]

In order to achieve the above object, the wireless transmitting/receiving device of the present invention includes a transmitting section that transmits a predetermined signal to the outside, and a receiving section that receives a received signal from the outside in a superheterodyne manner. comprises a splitter that divides a received signal into a plurality of signals, a plurality of attenuators that attenuates the levels of the plurality of signals from the splitter, and a plurality of automatic gain adjusters that respectively automatically adjust the output signal from each attenuator. and a switching selection circuit that switches and outputs one of the output signals from the plurality of automatic gain adjusters based on the level of the received signal input to the distributor. This is a characteristic feature.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a wireless transmitter/receiver according to the present invention. In FIG. 1, the same components as those of the apparatus shown in FIG. 2 will be described with the same reference numerals.

The wireless transmitting/receiving device shown in FIG. 1 differs from the device shown in FIG. Attenuator 51. ~51. and an attenuator 51. ~51. A plurality of automatic gain adjusters 52. ~52. and the plurality of automatic gain adjusters 52. ~52. A switching selection circuit 102 which switches and outputs one of the output signals from a switching control signal using a switching control signal, a switching control circuit 103 which outputs a switching control signal, and a switching control circuit 103 which detects the level of a received signal input to the distributor 101. A level detector 104 that supplies a predetermined signal to the switching control circuit 103 is provided, and the amplifier 11 is eliminated and the output signal of the first mixer 9 is sent to the distributor 1.
The point is that it is given to 2.

The operation of the embodiment configured as described above will be explained.

The received signals of a plurality of channels inputted from the circulator 6 to the band rejection filter that removes the wraparound of the transmission channel signal to the reception channel are distributed by the distributor 101 into m attenuators 511 to 511, each having a different amount of attenuation. 51, and then an automatic gain adjuster 52. ~5
2. is input. Here, attenuators 5, 11 to 51. If the amount of attenuation is T,,T,...T, then T,<T
, <...<T. In other words, a level detector 104 is provided at the output of the 0 divider 101, which has the highest input level to the attenuator 511, and the input level decreases sequentially. When the input level to the device 101 is high, the automatic gain adjuster 52 is switched and controlled so that the output signal from the automatic gain adjuster 521 side is outputted from the switching selection circuit 102 in order as the input level decreases.

As a result, even when the receiving input electric field to the device is high, there is no excessive input to the first mixer 9, and it is possible to suppress the occurrence of cross-modulation between channels. Therefore,
Good S/N ratio can be maintained. Note that fluctuations in the input electric field received by the device are unavoidable due to fading in the wireless transmission section, attenuation of radio waves due to rain, and the like.

The output signal of the first mixer 9 is distributed by a distributor 12, and
Similarly to FIG. 2, each channel is converted into a second intermediate frequency signal, demodulated, and output terminals 51+ to 51 of each channel.
51. is output from.

〔Effect of the invention〕

As explained above, the present invention divides a received signal into signals with different levels, and selects one output signal from a plurality of automatic gain adjusters according to the input level of the received signal. Therefore, an excessive input signal is not input to the first mixer, and the S/N ratio due to cross-modulation distortion can be improved. Moreover, since the present invention does not require the use of circuit elements or circuits that particularly consume power, power consumption can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the wireless transmitting/receiving device of the present invention, FIG. 2 is a block diagram showing a conventional device, and FIG. 3 is an explanatory diagram showing frequencies of each channel. 51, ~51. ...Attenuators 52, ~521...Automatic gain controller 101...Distributor 102...Switching selection circuit 103...Switching control circuit 104...Level detector

Claims (1)

[Claims] In a wireless transmitting/receiving device comprising a transmitting section that transmits a predetermined signal to the outside, and a receiving section that superheterodyne receives a received signal from the outside, the receiving section includes a distributor that divides the received signal into a plurality of signals. , a plurality of attenuators that attenuate the levels of the plurality of signals from the distributor, a plurality of automatic gain adjusters that automatically adjust the gain of the output signals from each attenuator, and a plurality of automatic gain adjusters that attenuate the levels of the plurality of signals from the plurality of automatic gain adjusters. A wireless transmitting/receiving device comprising: a switching selection circuit that switches and outputs one of the output signals based on the level of a received signal input to the distributor.