JP2568427B2 - Fast switching diversity receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] A high-speed switching diversity receiver that enables high-speed switching diversity and prevents malfunctions of diversity, detects a high frequency component in a field strength detection circuit by increasing a diversity clock frequency. The purpose of this is to prevent the occurrence of diversity malfunction based on the malfunction of electric field strength detection, and to alternately switch between the two systems of receivers and the intermediate frequency output of each receiver. A switching switch to be taken out, an envelope detection means for envelope-detecting the output of the switching switch, and a reception electric field of any of the receivers by taking out the output of the envelope detection means in synchronization with the switching of the switching switch. Determining means for determining whether the level is high, and according to the determination result, one of the receivers In detection after selection diversity receiver for generating an output signal by selecting the tone output,
A filter is inserted between the output of the switching switch and the input of the envelope detection means to pass only the intermediate frequency output.

[Industrial applications]

The present invention relates to a diversity receiver, and more particularly to a high-speed switching diversity receiver that enables high-speed switching diversity and prevents malfunction of diversity.

In a selective diversity receiver after detection, which is often used in mobile communications, by selectively extracting demodulated outputs of both receivers in response to electric field strength signals from two receivers having spatially separated antennas. Reduce the effects of fading.

Generally, the same frequency is repeatedly used as in the above-mentioned space diversity from the viewpoint of effective use of the frequency. In such a system, interference of the same channel and interference of an adjacent channel occur. However, in order to detect such interference, a higher resolution of the electric field strength detection circuit is required. Therefore, it is desired that the diversity receiver be capable of performing high-speed switching diversity and, at this time, be able to prevent malfunction of diversity due to malfunction of field effect strength detection.

[Conventional technology]

FIG. 2 shows a conventional diversity receiver, in which an A branch receives an input of a first antenna,
FIG. 6 illustrates a case where the second antenna is configured to receive an input of a second antenna. In the following, components of both branches A and B are distinguished by adding a suffix 1, respectively.

In both branches, an antenna ANT _1, RF input each band pass filter 1 ₁ ANT _2, 1 ₂ After receiving the O connexion required band limitation to pass through, RF amplifier (RFA) _{2 1,} 2 2
, And is band-limited through band-pass filters 3 ₁ , 3 ₂ to be added to first mixers (MIX) 4 ₁ , 4 ₂ .

In the first mixer 4 _1, 4 _2, each of the high-frequency signal produces a first 1IF signal is mixed with a local oscillator signal of the first local oscillator (1st LOCAL) 5. After this signal is band-limited through a bandpass filter 6 _and 62 second mixer (MIX)
It is added to 7 ₁ and 7 ₂ .

In the second mixer 7 _1, 7 _2, each of the first 1IF signal produces a first 2IF signal of the second local oscillator (2nd LOCAL) is mixed with 8 local oscillation signal of for example 455 KHz. This signal is band-limited through band-pass filters 9 ₁ and 9 ₂ and then amplified in IF amplifiers (IFA) 10 ₁ and 10 ₂ to form a limiter (LIM) 1
The amplitude is limited at 11 ₁ and 11 ₂ and demodulated at demodulators 12 ₁ and 12 ₂ . The output switch 13 selects one of the two demodulated signals to generate an output signal.

On the other hand, the 2IF signals of both Puranchi is removed from filter 9 _1, 9 ₂ on the output side, added to the diversity switching switch 14. Diversity switching switch 14 is inputted from the clock source 15 Yotsute to be switched in response to the diversity black poke, the filter 9 _1, 9 ₂ output by selecting alternately detection amplifier (LOG AMP) 16. The detection amplifier 16 includes a detector and an amplifier having a logarithmic characteristic, and performs envelope detection on the second IF signal input. The envelope output of the detection amplifier 16 is switched synchronously with the switch 14 according to the diversity clock from the clock source 15. The signals are alternately applied to the sample / hold circuits (S / H) 18 ₁ and 18 ₂ via the diversity switching switch 17 to hold the level. Comparator (COM) 19 compares the output level of the sample hold circuit 18 _1, 18 _2, switching the switch 13 according to the level of the level.

As a result, the demodulated output of the branch having the higher electric field level is always switched and output, thereby achieving the purpose of diversity reception.

[Problems to be solved by the invention]

In the conventional diversity receiver, it is not necessary to detect a high frequency component among the frequency components of the interference wave, for example, a component of 5 KHz or more, and accordingly, the frequency characteristic of the combined electric field strength detector in the diversity receiver is several hundred Hz to 2 KHz. It was good if it was about.

Under these circumstances, the diversity clock that drives the diversity switching switch because the input for electric field strength detection is switched in the diversity receiver also has a frequency such as about 7 to 8 KHz that reduces leakage to the audio signal. Was chosen.

In this case, if the sampling time of the detection signal is appropriately selected and the last part of the switched IF signal waveform which does not capture the noise at the time of switching of the diversity switching switch is sampled, the noise caused by the on / off of the diversity switching switch is obtained. Because the influence is suppressed, there is no need to take special measures to increase the speed.

However, in order to detect the interference component of high frequency such as the interference of the adjacent channel and perform the diversity operation, the sampling response is shortened and the frequency response of the electric field intensity detection circuit is increased to increase the frequency to a higher frequency. Although it is necessary to enable detection, the conventional circuit has a problem that a malfunction of the diversity occurs due to noise at the time of switching of the analog switch used for the diversity switching switch.

FIG. 3 exemplifies an analog switch used for a diversity switching switch.

FIG. 3 (a) shows a switch element, and shows a bidirectional switch 31 which turns on and off a signal by setting a low impedance or a high impedance in response to turning on / off a control signal. The diversity switching switch is constructed by combining a required number of such analog switches. (B) shows the crosstalk of such a switch element, and a crosstalk output is generated according to a control signal as shown in the figure. For example, V _DD = 5V, D _SS = −5
At V, the crosstalk voltage is about 120 mV.

4A and 4B show the diversity clock and the waveforms of the input and output of the detection amplifier. FIG. 4A shows the diversity clock, and FIG. 4B shows a beard generated by the crosstalk at the time of switching from the diversity switching switch. 9 shows noise composed of pulse-like pulses. (C) shows the output of the detection amplifier, A shows the envelope output by the IF signal interrupted by the diversity clock, and B shows the output based on the whisker pulse noise of the diversity switching switch.
That is, when the branch is switched to another branch due to the falling edge of the diversity, it operates instantaneously as if the detection clock amplifies the diversity clock, and generates an output as shown in B. Therefore, at a low electric field level, the output indicated by B becomes larger than the output A based on the IF signal, and the level detection is performed by this portion, which causes a malfunction between branches in the diversity operation.

Since the conventional diversity clock frequency is low, such a malfunction is prevented by selecting a phase for sampling the output of the detection amplifier. However, such a countermeasure becomes difficult when the clock frequency becomes high.

SUMMARY OF THE INVENTION The present invention is to solve such a problem of the prior art. The present invention aims to increase the frequency of a diversity clock so that a circuit for detecting electric field strength can detect even high frequency components. It is an object of the present invention to provide a high-speed switching diversity receiver that does not cause a diversity malfunction due to the malfunction of the above.

[Means for Solving the Problems] The present invention is to solve such problems of the prior art, and as shown in the embodiment of FIG.
It has receivers A and B of the system, and alternately takes out the intermediate frequency output from the receivers of the respective systems via the switching switch 14 and takes out the output of the switching switch 14 via the envelope detection means 16 for envelope detection. The output of the envelope detection means 16 is supplied to the determination means 18 ₁ , 18 ₂ , 19 via the switching switch 17 synchronized with the switching of the switching switch 14 to determine which of the receivers has a higher received electric field level, and this In the post-detection selection diversity receiver, which selects the demodulation output of one of the receivers according to the determination result and generates an output signal, the switching switch
A filter 20 that allows only the intermediate frequency output to pass is inserted between the output 14 and the input of the envelope detection means 16.

(Operation)

By inserting a high-pass filter at the input of the detection amplifier in the present invention, it is possible to attenuate low-frequency components in the signal input to the detection amplifier, amplify only necessary IF signals, and perform envelope detection. It can be so.

In FIG. 4, (d) shows the output of the detection amplifier when a high-pass filter is inserted in the input. The output is not generated due to noise based on crosstalk generated from the diversity switching switch, and only the envelope of the IF signal is shown. Is output.

Therefore, according to the present invention, even if the diversity switching is performed at a high speed, the circuit for detecting electric field strength erroneously detects the noise based on the diversity switching switch, and the malfunction of the diversity does not occur.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which the same parts as those in FIG. 2 are indicated by the same numbers, and 20 is a high-pass filter.

In the circuit of FIG. 1, when the diversity clock frequency of the clock source 15 is 10 KHz, the cut-off frequency of the high-pass filter 20 is selected to be about 100 KHz. Accordingly, the filter 20 allows the IF signal (455 KHz) to pass, but does not allow the mustard pulse noise based on the crosstalk generated from the diversity switching switch 14 to pass. In order to perform such an operation, a band-pass filter that selectively passes an IF signal may be used instead of the high-pass filter 20. In this case, the filter Q is suitably about 10.

As described above, in the present invention, since the filter for cutting off the low-frequency component is inserted into the input of the detection amplifier for generating the electric field strength detection signal, the signal is generated when the diversity clock rises or falls from the diversity switching switch. The whisker-like pulse noise does not appear in the output of the detection amplifier. Therefore, even when the electric field intensity is small and the level of the IF signal input to the detection amplifier is low, the level detection is performed by such noise, and the malfunction of the diversity does not occur.

Also, the IF signal is subjected to AM modulation by noise generated due to the operation of the diversity switching switch, and demodulated signals 12 ₁ , 12 ₂
However, there is a phenomenon in which noise of the clock signal frequency is generated in the output signal via the signal, and the noise is mixed into the audio signal. However, when the diversity clock frequency is increased, the noise is out of the audio band and the leakage can be reduced.

〔The invention's effect〕

As described above, according to the present invention, since the filter for cutting off the low frequency is inserted between the diversity switching switch and the electric field strength detection circuit, the influence of the noise based on the crosstalk generated from the diversity switching switch. A malfunction of diversity does not occur, so that high-speed diversity can be achieved, and high-frequency interference such as interference between adjacent channels can be detected. In addition, since the diversity clock frequency is increased, the leakage of the diversity clock to the audio signal is reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a conventional diversity receiver, FIG. 3 is a diagram illustrating an analog switch used in a diversity switching switch, and FIG. 4 is a diversity clock. FIG. 3 is a diagram showing waveforms of input and output of a detection amplifier. 1 ₁ , 1 ₂ , 3 ₁ , 3 ₂ , 6 ₁ , 6 ₂ , 9 ₁ , 9 ₂ ... Band-pass filter 2 ₁ , 2 ₂ ... RF amplifier (RFA) 4 ₁ , 4 ₂ , 7 ₁ , 7 ₂ … Mixer (MIX) 10 ₁ , 10 ₂ … IF amplifier (IFA) 14,17… Diversity switching switch 16… Detector amplifier (LOG AMP) 20… High-pass filter

Claims (1)

(57) [Claims] 1. A two-system receiver (A, B), a switching switch (14) for alternately switching and extracting an intermediate frequency output from each of the receivers (A, B), and an output of the switching switch (14) Envelope detection means (16) for envelope detection
Determining means (17, 18) for determining which receiver has a higher received electric field level by extracting the output of the envelope detection means (16) in synchronization with the switching of the switching switch (14). ₁ , 18 ₂ , 19), and a demodulation selection diversity receiver for selecting one of the demodulated outputs according to the determination result and generating an output signal, wherein the output of the switching switch (14) is And envelope detection means (16)
A high-speed switching diversity receiver characterized in that a filter (20) that allows only an intermediate frequency output to pass is inserted between the input and the input.