JPH08107380A - Diversity receiver - Google Patents

Abstract

PURPOSE: To provide a diversity receiver for spread spectrum communication capable of selecting an antenna in which a correct signal highest in its level is received. CONSTITUTION: This receiver is constituted of plural antennas 1 and 2, a changeover switch 3 selecting the antennas 1 and 2, an RF/IF conversion part 4, an SAW matched filter 51, a delay circuit 52, a multiplier 53, an LPF 54, an absolute value circuit part 6, an AGC circuit 7, an A/D conversion part 8, a correlation signal detection circuit 9 detecting a correlation signal from an absolute value signal, a storage part 10 temporarily storing detection data and AGC data, a comparator 11 comparing the AGC data corresponding to the stored antennas and a control part 12 controlling the changeover switch 3 based on the correlation data corresponding to the comparison result and the stored antennas. The receiver successively switches the antennas 1 and 2, and selects the antennas in which the correct signal highest in its level is received by the comparison result and the correlation signal detection data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to switched diversity among spatial diversity, and more particularly to AGC.
Spread spectrum communication diversity receiver.

[0002]

2. Description of the Related Art "Spatial diversity", "frequency diversity", "time diversity", "directional diversity", "polarization diversity", "electromagnetic field diversity", etc. are considered as diversity as a technology for multipath fading. ing. “Spatial diversity” is classified into a demodulated signal reproduction method, and is classified into a “switching type” shown in FIG. 3, a “straight line combining type” shown in FIG.
The three types of “square-combination type” shown below are known as typical ones. Of the above, “switching diversity” is provided with a switch at the antenna input end as shown in FIG. 3 to switch a plurality of antennas, detect and compare input levels, and select the antenna that gives the best signal. Is the way to do it.

Conventionally, as shown in FIG. 6, a switching diversity receiver has a plurality of antennas spatially separated from each other, a changeover switch for selecting the antennas by a control signal, and an RF signal from the selected antennas. An RF / IF converter that selectively amplifies and converts the RF frequency band to an intermediate frequency band, and a level detector that detects the level of the signal from the RF / IF converter that is input to the detection circuit, and this level A storage unit that stores signals, a comparison unit that compares the stored level signals, and a control unit that controls the changeover switch based on the comparison result of the comparison unit. It is controlled so that the signal level can be obtained. As one method, the plurality of antennas are sequentially switched, the levels of the intermediate frequency signals from the RF / IF conversion unit are stored and compared, and the antenna having a higher level is selected and switched. As another method, the plurality of antennas are sequentially switched, the levels of the intermediate frequency signals from the RF / IF conversion unit are stored and compared, and a high level signal is left in the storage unit to finally obtain the highest level signal. I try to leave a signal.

However, when the above method is applied to a spread spectrum (direct spread) modulation system, the spread spectrum signal has a much wider band than the general narrow band modulation signal and the signal level is also high. Since the signal level is low, there is a problem in that if a narrow-band signal that is not spectrum-spread exists in the same frequency band, the antenna that inputs the narrow-band signal will be erroneously selected by simply comparing the signal levels. Also, if a signal spread-modulated with another spreading code is input at a higher level than the spread-modulated signal that is originally intended to be received, the antenna to be input at a high level may be erroneously selected. was there. In either case, signals other than the desired signal are input at a higher level, making it difficult to demodulate the signal.
The characteristic of spread spectrum modulation, which is inherently resistant to interference, is lost.

In order to solve these problems, in the case of the spread spectrum communication system, as shown in FIG. 7, detection is performed by using the correlation signal which is the output of the SAW (surface acoustic wave) matched filter used for demodulation processing. A method has been proposed in which the detected signal to be converted is converted into an absolute value signal, the levels of the absolute value signal are compared, and the antenna is switched. However, this method can be used because the correlation signal has a level proportional to the reception level without the AGC circuit, but when the AGC circuit is added and the correlation signal is automatically controlled to a constant level, the absolute value signal Since there is no level difference, the levels cannot be compared and cannot be used.

Therefore, it is conceivable to use the AGC signal for controlling the AGC amplifier as the comparison signal. In this case, however, the AGC signal becomes maximum when an incorrect signal having no correlation signal is received. There is a problem that the correct antenna cannot be selected.

[0007]

SUMMARY OF THE INVENTION The present invention solves the problems described above and selects an antenna for inputting a correct and highest level signal, which is an AG for spread spectrum communication.
The purpose is to provide a diversity receiver with C.

[0008]

In order to solve the above problems, the present invention provides a plurality of antennas spatially separated from each other,
A changeover switch for selecting the antenna by a control signal, an RF / IF converter for selectively amplifying a spread spectrum modulation signal from the selected antenna and converting it from an RF frequency band to an intermediate frequency band, and a signal of the intermediate frequency. A detection circuit that inputs and outputs a detection signal, an absolute value circuit unit that converts the detection signal from the detection circuit into an absolute value signal and outputs the absolute value signal, and the RF from the absolute value signal from the absolute value circuit unit.
An AGC circuit that generates an AGC signal that controls the / IF converter, an A / D converter that converts the AGC signal from the AGC circuit into a digital signal, and a correlation signal is detected from the absolute value signal from the absolute value circuit. Correlation signal detection circuit, storage unit for temporarily storing detection data from the correlation signal detection circuit and AGC data from the A / D conversion unit, and AGC data corresponding to the plurality of antennas stored in the storage unit And a control unit that outputs a control signal for controlling the changeover switch based on the comparison result from the comparator and the correlation data corresponding to the plurality of antennas stored in the storage unit. , The antenna is sequentially switched by the control signal from the control unit, and the antenna that receives the signal with the correlation signal detection data and the highest reception level is selected. It has to.

[0009]

According to the diversity receiver of the present invention, the spread spectrum modulation signals from a plurality of antennas are selectively amplified and gain controlled by the RF / IF converter to be converted into an intermediate frequency band. Then, the correlation signal obtained by passing the signal in the intermediate frequency band through the SAW matched filter is differentially detected, this is converted into an absolute value signal by an absolute value circuit, and the AGC signal generated from this absolute value signal is subjected to the RF / IF conversion. Feedback to the department,
Based on the result of comparing the converted AGC data for each antenna with the digital signal and the correlation signal detection data for detecting the correlation signal from the absolute value signal, the control unit has the correlation signal and receives the signal. Switching to the antenna that inputs the highest level signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A diversity receiver according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a diversity receiver according to the present invention. In the figure, 1 is a first antenna and 2 is a second antenna. Reference numeral 3 denotes a changeover switch, which switches the antenna 1 and the antenna 2 by a control signal from the control unit 13. Reference numeral 4 denotes an RF / IF converter, which selects a spread spectrum modulated RF band signal selected and input by the changeover switch by a band pass filter (BPF) 41, amplifies it by a linear amplifier 42, and further, an AGC amplifier 43. Then, the level is made constant by the AGC signal, and the down converter 44 converts the signal into an intermediate frequency band signal. 5
Is a detection circuit unit that receives a signal modulated by a spreading code to be received and obtains a correlation signal, a SAW matched filter 51, and a delay circuit 52 that delays the correlation signal by one spreading period. The multiplier 53 that outputs the delayed detection signal by multiplying the correlation signal before the delay and the correlation signal after the delay, and the LPF that outputs the detection signal by cutting the high frequency component of the delayed detection signal. Low-pass filter) 54
It consists of. An absolute value circuit unit 6 converts the detection signal into an absolute value signal.

Reference numeral 7 denotes an AGC circuit, which receives the absolute value signal and performs peak detection, a peak detection circuit 71, a loop filter 72 for converting the peak detection signal into a smooth signal, and a reference for comparing the signal with a reference signal. It is composed of a comparison circuit 73 and a DC offset circuit 74 for offsetting a DC component,
The AGC signal is generated. 8 is an A / D converter,
The AGC signal is converted into a digital signal to obtain AGC data. A correlation signal detection circuit 9 detects the presence or absence of a correlation signal from the absolute value signal and outputs the detection signal as correlation detection data. A storage unit 10 stores the AGC data and the detection data corresponding to the plurality of antenna numbers. A comparator 11 compares the AGC data stored in the storage unit and inputs the comparison result to the control unit 12. Reference numeral 12 denotes the control unit, which controls switching of the changeover switch 3 based on the input comparison result and the correlation detection data stored in the storage unit.

The operation of the above arrangement will be described below. According to the control signal from the control unit 12, the spread spectrum modulated RF signal input from the first antenna 1 is selected by the changeover switch 3 and input to the RF / IF conversion unit 4, and the selective amplification and the level are made constant. After that, it is converted into the IF signal S1 in the intermediate frequency band shown in FIG. The IF signal S1 is passed through the SAW matched filter 51 to obtain the correlation signal S2 shown in FIG.
Then, the differential detection is performed via the multiplier 53 and the high frequency component is cut through the LPF 54 to obtain the detection signal S3 shown in FIG. The detected signal S3 is sent to the absolute value circuit section 6 as shown in FIG.
It is converted into an absolute value signal S4 shown in d and input to the AGC circuit 7 and the correlation signal detection circuit 9. The absolute value signal S4 is peak-detected by the AGC circuit 7, converted into a DC signal through a loop filter, and compared with a reference signal, and then the DC component is offset to obtain an AGC signal. This AGC signal is
The AGC amplifier 43 is controlled, converted into a digital signal by the A / D converter 8, and stored in the storage unit 10 as AGC data corresponding to the antenna number. For the absolute value signal S4, the presence or absence of a correlation signal is detected by the correlation signal detection circuit 9, and this detection data is stored in the storage unit 10 in correspondence with the antenna number. The stored AGC data is compared by the comparator 11 for each antenna number, a correlation signal is generated based on the comparison result and the stored presence / absence detection data of the correlation data, and the signal is received from the antenna having the highest reception level. As described above, the control unit 12 controls the switching unit 3
Are in control.

[0013]

As described above, according to the diversity receiving apparatus of the present invention, the spread spectrum modulated signals from the plurality of antennas are selectively amplified and gain-controlled by the RF / IF converter to be converted into the intermediate frequency band. Then, the correlation signal obtained by passing the signal in the intermediate frequency band through the SAW matched filter is subjected to delay detection, this is converted into an absolute value signal by an absolute value circuit, and an AGC made from this absolute value signal
The signal is fed back to the RF / IF converter, and A / D converted into a digital signal.
Based on the result of comparing the C data for each antenna and the correlation signal detection data for detecting the correlation signal from the absolute value signal,
Since the control unit has switched to the antenna that receives the signal having the highest received level and the correlation signal, the AGC for spread spectrum communication that selects the antenna that inputs the highest level signal with the correct signal It is possible to provide a diversity receiving device.

[Brief description of drawings]

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

FIG. 2 shows a signal waveform of a main part of a diversity receiver for spread spectrum communication with AGC according to the present invention.

FIG. 3 is a block diagram showing a conventional diversity receiver.

FIG. 4 is a block diagram showing a conventional diversity receiver.

FIG. 5 is a block diagram showing a conventional diversity receiver.

FIG. 6 is a block diagram showing a conventional switched diversity receiver.

FIG. 7 is a block diagram showing a conventional diversity receiver for spread spectrum communication.

[Explanation of symbols]

 1 1st antenna 2 2nd antenna 3 Changeover switch 4 RF / IF conversion part 5 Detection circuit part 6 Absolute value circuit 7 AGC circuit 8 A / D conversion part 9 Correlation signal detection circuit 10 Storage part 11 Comparator 12 Control part 41 band pass filter 42 linear amplifier 43 AGC amplifier 44 down converter 51 SAW matched filter 52 delay circuit 53 multiplier 54 low pass filter 71 peak detection circuit 72 loop filter 73 reference comparison circuit 74 DC offset circuit

Claims (6)

[Claims] 1. A plurality of antennas spatially separated from each other, a changeover switch for selecting the antenna by a control signal, a spread spectrum modulation signal from the selected antenna is selectively amplified, and an intermediate frequency band rather than an RF frequency band. An RF / IF conversion unit for converting into a signal, a detection circuit for inputting the intermediate frequency signal and outputting a detection signal, and an absolute value circuit unit for converting the detection signal from the detection circuit into an absolute value signal and outputting the absolute value signal. , An AG for generating an AGC signal for controlling the RF / IF conversion unit from an absolute value signal from the absolute value circuit unit
A C circuit, an A / D converter for converting the AGC signal from the AGC circuit into a digital signal, and a correlation signal detection circuit for detecting a correlation signal from the absolute value signal from the absolute value circuit,
A storage unit for temporarily storing the detection data from the correlation signal detection circuit and the AGC data from the A / D conversion unit, and a comparator for respectively comparing the AGC data corresponding to the plurality of antennas stored in the storage unit. , A control unit for outputting a control signal for controlling the changeover switch based on a comparison result from the comparator and correlation data corresponding to a plurality of antennas stored in the storage unit, and a control signal from the control unit The diversity receiving device is characterized in that the antennas are sequentially switched by the above, and the antenna that receives the signal having the correlation signal detection data and the highest reception level is selected. 2. The diversity receiving apparatus according to claim 1, wherein the RF / IF conversion unit includes a bandpass filter, a linear amplifier, an AGC amplifier, and a down converter. 3. The detector circuit outputs S, which outputs a correlation signal.
An AW matched filter, a delay circuit that delays the correlation signal, a multiplier that multiplies the signal from the SAW matched filter and a signal from the delay circuit, and a high frequency component of the detection signal from the multiplier is cut. The diversity receiving apparatus according to claim 1, wherein the diversity receiving apparatus is configured with an LPF that outputs a detection signal. 4. The diversity receiver according to claim 1, wherein the AGC circuit comprises a peak detection circuit, a loop filter, a reference comparison circuit, and a DC offset circuit. 5. The diversity receiving apparatus according to claim 1, wherein the storage unit is composed of a plurality of registers. 6. The control unit is configured to sequentially switch the plurality of antennas when power is turned on and when a reception channel in the RF / IF conversion unit is switched. Diversity receiver.