JPH07297732A - Receiver - Google Patents

Abstract

(57) [Abstract] [Purpose] In a receiving apparatus including a plurality of BPFs having different characteristics from each other, an influence degree of an interference wave is accurately determined and an appropriate BPF is performed. A switching control unit 12 detects a received signal level and obtains a detection probability of predetermined data included in a demodulated received signal for determining a degree of interference. Then, the switching control unit 12 determines the interference degree from the combination of the received signal level and the detection probability, and selects an appropriate BPF from the filter group 4 based on the interference degree.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for suppressing adjacent interference waves in a receiver, and more particularly to a circuit for selecting a plurality of band pass filters.

[0002]

2. Description of the Related Art In a receiving device such as a heterodyne receiver, when a signal of an adjacent frequency is mixed as an interfering wave,
The desired signal cannot be properly received.
Therefore, it is necessary to suppress the interference wave, and the conventional receiving device has a bandpass filter (bandpass filter: BPF) for suppressing the interference wave. However, if the band is always set to a narrow band, the sensitivity will decrease even though there is no interfering wave. Further, it is desirable to switch the pass band according to the strength of the interfering wave. Therefore, a receiving device has been proposed which switches and uses a plurality of BPFs having different pass band characteristics (see, for example, Japanese Patent Laid-Open No. 57-184328).

FIG. 9 shows such a conventional receiving apparatus. In FIG. 9, the front end portion has a BPF.
16 and a high-frequency amplifier 2 are provided, and the received signal that has passed through them is mixed with the first local oscillator signal by the first mixer 3. The received signal that has passed through the BPF 4 and the amplifier 5 in the first intermediate frequency stage is mixed with the second local oscillator signal in the second mixer 6. A filter group 17 for suppressing interference is provided at the subsequent stage. Here, the filter group 17 is composed of a plurality of BPFs whose pass bands gradually change. The received signal that has passed one of the BPFs in the filter group 17 is input to the FM demodulator 18 via the amplifier 8 and demodulated.

The output of the FM demodulator 18 is the beat detector 1
9 has been entered. The beat detector 19 is a circuit that detects a beat that occurs when a desired wave component and an interfering wave component are mixed, and the switching control unit 20 selects an appropriate BPF according to the beat level.

Next, the operation will be described. The received signal from the ANT is converted to the first intermediate frequency through the BPF 16, the amplifier 2 and the first mixer 3, and then further converted to the BPF 4.
It is converted to the second intermediate frequency through the amplifier 5 and the second mixer 6. Then, the received signal is further detected by the FM demodulator 18 via the BPF 17 and the amplifier 8, and the detected signal is output.

If an interfering wave is received while the desired wave is being received, a beat component generated by the interaction between the desired wave and the interfering wave appears in the output of the FM demodulator 18, and this beat component is detected as a beat. It is detected by the device 19. Next, this beat detection signal is sent to the switching control unit 20, where the size of the beat, that is, the strength of the interfering wave is judged, and based on that, in order to select an appropriate one from the plurality of BPFs. The switching signal is output.

Generally, when there is no interference, the BPF 17a having the widest pass band width and the gentle selectivity characteristic is selected, and when the interference is strong, the BPF 17n having the narrowest pass band width and the steep selectivity characteristic is selected. It

When there is no interfering wave, the BPF 17a having the largest pass band width is selected. As a result, the deterioration of the phase characteristic and the distortion characteristic in the pass band are improved, and the reception sensitivity is improved because the loss is small.

[0009]

In the above-mentioned conventional device,
In the beat detector 19, the output of the demodulation circuit 18 is compared with the threshold level corresponding to each BPF by the comparator. That is, analog comparison and determination are performed. Therefore, the setting of each threshold level is delicate and it takes time to set. Further, since the fluctuations due to environmental conditions such as temperature and aging change are large, there is a possibility that the detection accuracy of the interfering wave may deteriorate. In such a case, there arises a problem that a wide band BPF is selected to cause sensitivity deterioration in the presence of an interfering wave, or a narrow band BPF is selected even when no interfering wave is present and reception sensitivity is not improved.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a receiving apparatus capable of accurately determining the degree of interference itself due to an interference wave and appropriately selecting a BPF. And

[0011]

In order to achieve the above object, the invention according to claim 1 includes a filter group for removing an interfering wave, which comprises a plurality of band pass filters having different characteristics. In a receiving device in which the band pass filter is selected and used, a level detection circuit that detects a received signal level in a subsequent stage of the filter group, a demodulated received signal is monitored, and predetermined data included in the received signal is detected. A predetermined data detection circuit, a detection probability calculation circuit for obtaining a detection probability that the predetermined data is properly detected,
An interference degree determination circuit that determines an interference degree based on a combination of the magnitude of the received signal level and the detection probability, and a filter selection circuit that selects an appropriate bandpass filter from the filter group based on the interference degree. And are included.

The invention according to claim 2 is characterized in that the predetermined data is data for frame synchronization.

According to a third aspect of the present invention, the predetermined data is data for error detection.

According to a fourth aspect of the present invention, the receiving device is characterized in that the filter group is provided in an intermediate frequency stage.

The invention according to claim 5 is characterized in that the filter group is provided in a front end portion.

According to a sixth aspect of the present invention, the filter group is provided in both the intermediate frequency stage and the front end section, and they are switched in conjunction with each other.

[0017]

According to the above structure, the reception signal level after passing through the filter is detected, and the probability that the predetermined data is properly detected is obtained. Here, as the predetermined data, for example, frame synchronization data or error detection data is used. The former can be adopted when the content of communication data can be increased, and the latter uses existing data.

Then, the degree of interference is determined based on the combination of the received signal level and the detection probability of the predetermined data, and the bandpass filter corresponding to the degree of interference is selected. Therefore, the reception level of the desired wave is used as the criterion, and whether the demodulated data can be properly read is also used as the criterion, so the degree of interference (interference degree) that the interference wave gives to the desired wave can be accurately determined. As a result, it is possible to select an appropriate filter according to the state. Further, since the data can be digitally processed, the degree of interference can be determined with high accuracy in that sense.

That is, in the present invention, the degree of interference is accurately determined based on a plurality of information, and the filter is switched based on the determination result.

The filter groups are arranged, for example, in one or both of the first stage and the intermediate frequency stage. When they are arranged in both stages, interlocking switching is performed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the receiving apparatus according to the present invention. This receiving device is provided, for example, in a base station of a cordless telephone system. In addition,
The same components as those in the related art are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, the filter group 4 is composed of a plurality of BPFs 4a-4n in the first intermediate frequency stage.
Each BPF differs from each other in pass band width, selectivity characteristic and insertion loss as in the conventional case. Nyquist filter 7
Determines the characteristic of the demodulator 9 in the second intermediate frequency stage, which demodulates the signal and converts it into a digital signal. The data processing circuit 10 is
It processes data as a demodulated digital signal.

In the first embodiment, the UW detection circuit 11
Is for detecting a unique word (hereinafter referred to as UW) from the demodulated data and outputting a detection pulse. U
W is a frame synchronization signal, which is inserted into the communication frame on the transmission side.

The switching control unit 12 is a circuit for switching a plurality of BPFs according to the detection state of the UW signal and the magnitude of the reception input level (hereinafter referred to as RSSI) signal, and outputs the switching signal.

As will be described later in detail, the switching control unit 12 has a function of calculating a detection probability that the UW signal is properly detected, a function of determining the degree of disturbance according to a degree of interference determination table, and a filter switching signal. And a function to generate.

Specifically, the switching control unit 12 uses the RSSI
A / D converter 12a for converting a signal into a digital signal
A circuit 12b for averaging the level of the RSSI signal within a certain period of time, a circuit 12c for averaging UW detection pulses within a certain period of time to obtain a detection probability, and an arithmetic circuit for determining the degree of interference and generating a switching signal And 12d. Here, the certain fixed time is generally about 10 to 20 times as long as one frame.

Next, the operation will be described. The reception signal from the ANT passes through the BPF 1, the high frequency amplifier 2, and the first mixer 3 in the front end section, is converted into the first intermediate frequency, and is then supplied to the first intermediate frequency BPF group 4.

The received signal that has passed through the first intermediate frequency BPF selected by the switching control unit 12 is sent to the second mixer 6 after passing through the amplifier 5, and is converted into the second intermediate frequency here. . Further, the received signal passes through the amplifier 8 and is demodulated by the demodulator 9 and converted into a digital signal (data), and then the data processing circuit 10 performs general processing of the data.

Here, of the BPF group 4, the BPF 4a has the widest pass bandwidth, the selectivity characteristics are gentle, and the insertion loss is small. On the contrary, the BPF 4n has the narrowest pass band width, steep selectivity characteristics, and large insertion loss. The BPFs 4b to 4 (n-1) have intermediate characteristics in a stepwise manner.

Next, the operation when there is no interfering wave and when there is an interfering wave will be described. FIG. 7 shows an example of the disturbance degree determination table in the switching control unit 12. In FIG. 7, P indicates the UW detection probability, and P1 <P
2 <P3 <P4 ≦ 1. L indicates the reception level (RSSI level) of the desired wave, and L1 <L2 <L3 <L4. U is the size affected by the interference wave (interference degree)
And U0 <U1 <U2 <U3, for example, U0 indicates a state where there is almost no interference, and U3 indicates a state where there is strong interference. Note that P1 to P4 and L1 to L4 mean intervals, that is, the detection probability is 4 between 0 and 1.
It is divided into two sections. In addition, the degree of disturbance is classified into four levels. The number of stages is set according to the number of filters.

When there is no disturbing wave or the desired wave is sufficiently larger than the disturbing wave, the probability of UW detection is high (P4). Therefore, the disturbing degree is always U0 regardless of the RSSI level value, and the disturbing wave is received. It is determined that not. Therefore, in the first intermediate frequency BPF group 4, the BPF 4a is selected according to the instruction from the switching control unit 12.
That is, only the BPF 4a is connected. BPF4a is
Since the pass band width is wide and the insertion loss is small, good reception is possible even when the reception input level is lowered.

On the other hand, the RSSI level is sufficient (L3,
L4), the UW detection probability is small (P1,
In the case of P2), the magnitude of the disturbing wave is U2 or U3, and it is determined that the strong disturbing effect is occurring. Therefore, the BPF 4c or 4d (not shown) is selected in the first intermediate frequency BPF group 4. Since the BPF 4c or 4d has a narrow pass band width and a steep selectivity characteristic, it can sufficiently attenuate an interference wave, and enables good and stable reception.

When the magnitude of the interfering wave is U0, BP
F4a is selected, when U1, BPF4b is selected,
When U2, BPF4C is selected.

As described above, when there is no interfering wave,
Alternatively, when the interfering wave is sufficiently smaller than the desired wave, a BPF with a wide pass band and low loss is selected, so that the sensitivity can be improved. On the other hand, when the interfering wave is large (strong), a BPF having a narrow pass band width and a steep selectivity characteristic is selected, so that the interfering wave can be sufficiently attenuated to reduce the influence and good reception is possible. Become.

Next, a second embodiment will be described. Example 1
Then, in determining the interfering wave, the detection state of the UW signal is monitored, the detection probability is obtained, and the magnitude of the interfering wave (interference degree) is determined in combination with the magnitude of the RSSI level. Then, instead of monitoring the detection state of the UW signal, the CRC error detection result may be monitored. FIG. 2 shows the configuration of the second embodiment. The operation until the received signal from the ANT is output to the data processing circuit 10 via the demodulator 9 is the same as that in the first embodiment.

The demodulated data processed by the data processing circuit 10 is sent to the CRC error detection circuit 13, where it is determined whether or not there is an error, and the output is sent to the switching control unit 12. The switching control unit 12 has the same function as that of the first embodiment, that is,
A circuit 12c for averaging CRC error detection results within a certain period of time to obtain a probability of proper detection, a circuit 12b for averaging the RSSI level, and an arithmetic circuit for determining the degree of disturbance according to the degree of interference determination table and outputting a switching signal. 12d
And.

FIG. 8 shows an interference wave determination table. The table is stored in the ROM or the like. In FIG. 8, Q indicates a CRC error detection result (detection probability), and there is a relationship of Q1 <Q2 <Q3 <Q4 ≤1, and the subsequent determination method is the same as that of the first embodiment (FIG. 7).

In the first and second embodiments, since the existing code can be used as the data for judging the degree of interference, it is not necessary to insert a special code on the transmitting side. Various data can be adopted as the data for determining the degree of disturbance.

Next, a third embodiment will be described. Example 1
Then, the switching control was performed for the first intermediate frequency BPF group, but instead, the present invention can be applied to the case where a plurality of BPFs are provided in the front end portion and the BPFs are selected. This will be described below.

In the BPF group 14 in the front end section, the BPF 14a has the widest pass band width, gentle selectivity characteristics, and small insertion loss. BP
On the contrary, F14n has the narrowest pass band width, steep selectivity characteristics, and large insertion loss. The method of detecting the interfering wave and switching / connecting the BPF is the same as in the first embodiment.
Size of RSSI level and UW included in demodulation data
The degree of interference is determined based on the combination of detection states (detection probabilities) of signals, and the BPF is selected according to the degree of interference.

That is, when there is no interfering wave or the interfering wave is sufficiently smaller than the desired wave, the BPF is 14
a is selected, and 14n is selected when the interference wave is strong. Since the BPF14 group is arranged in the front end part, the BPF insertion loss influences the NF of the receiver and directly affects the sensitivity of the receiver. Therefore, when the BPF14a is selected, the insertion loss is small and the sensitivity is small. Can be improved.

Next, a fourth embodiment will be described. In the third embodiment, for determining the degree of interference and controlling the switching of the BPF,
Although it was performed by monitoring the magnitude of the RSSI level and the detection state of the UW signal, the same effect can be obtained by monitoring the magnitude of the RSSI level and the CRC error detection result (detection probability). . In that case, the configuration is as shown in FIG.

Next, the fifth and sixth embodiments will be described. In the fifth and sixth embodiments, the BPF group is provided in both the first intermediate frequency stage and the front end section. In that case, the switching control is simultaneously performed on the two BPF groups.

In the fifth embodiment shown in FIG. 5, determination of the degree of obstruction,
BPF switching control is based on the size of RSSI level and UW.
This is performed by monitoring the detection state (detection probability) of the signal. On the other hand, in the sixth embodiment shown in FIG. 6, the size of the RSSI level and the CRC error detection result (detection probability) are monitored.

As described above, the probability that the predetermined data periodically inserted into the received signal can be properly judged can be used as the basis for the judgment of the degree of interference, so that the influence of the interference wave on the desired wave can be directly detected and the received signal can be detected. Since the level is taken into consideration, the degree of interference can be determined with high accuracy.

[0047]

As described above, according to the present invention, the influence of the interfering wave can be accurately determined, and an appropriate filter can be selected accordingly. Therefore, depending on the presence or absence of interference and the degree,
It is possible to form a stable and best reception state. In addition, since the main part of the determination can be configured by a digital circuit, the advantages of no adjustment of the circuit, no adjustment time required, and low cost can be obtained, and stable operation can be ensured against environmental conditions such as aging of temperature.

[Brief description of drawings]

FIG. 1 is a block diagram of a receiving device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a receiving device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a receiving device according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a receiving device according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of a receiving device according to a fifth embodiment of the present invention.

FIG. 6 is a block diagram of a receiving device according to a sixth embodiment of the present invention.

FIG. 7 is a diagram showing a first example of a disturbance degree determination table.

FIG. 8 is a diagram showing a second example of a disturbance degree determination table.

FIG. 9 is a block diagram showing a conventional receiving device. .

[Explanation of symbols]

4 bandpass filter (BPF) of the first intermediate frequency stage,
7 bandpass filter of the second intermediate frequency stage, 9 demodulator, 10 data processing circuit, 11 unique word (U
W) Detection circuit, 12 switching control section, 13 CRC error detection circuit, 14 band pass filter (BPF) of front end section.

Claims (6)

[Claims] 1. A receiving apparatus including a filter group for removing an interfering wave, comprising a plurality of bandpass filters having different characteristics from each other, wherein any one of the bandpass filters is selected and used, in a subsequent stage of the filter group. A level detection circuit for detecting the received signal level, a predetermined data detection circuit for monitoring the demodulated reception signal and detecting predetermined data included in the received signal, and a detection for obtaining a detection probability that the predetermined data is properly detected Probability calculation circuit, interference degree determination circuit that determines the degree of interference based on the combination of the magnitude of the received signal level and the detection probability, based on the interference degree, an appropriate bandpass filter from the filter group A receiving device comprising: a filter selecting circuit for selecting. 2. The receiving device according to claim 1, wherein the predetermined data is data for frame synchronization. 3. The receiving device according to claim 1, wherein the predetermined data is data for error detection. 4. The receiver according to claim 1, wherein the filter group is provided in an intermediate frequency stage. 5. The receiving device according to claim 1, wherein the filter group is provided in a front end section. 6. The receiving device according to claim 1, wherein the filter group is provided in both the intermediate frequency stage and the front end section, and they are interlocked and switched.