JP2008219364A - Microwave relay receiving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an FPU receiving device capable of reducing deterioration in transmission quality due to interference of an adjacent wave by judging the deterioration in transmission quality due to the interference of the adjacent channel signal wave by quantitatively detecting a transmission state. <P>SOLUTION: An intermediate frequency band of the FPU receiving device is provided with a band-pass filter of a desired wave BPF 2A, a lower adjacent wave BPF 3A, and an upper adjacent wave BPF 4A, and outputs thereof are detected by detecting circuits 2 to 4 to display a reception power level on a console panel. When an adjacent wave has a higher reception electric field than the desired wave, a desired wave level is corrected based upon the detection output difference between the adjacent wave and desired wave to maintain a desired wave reception electric field display function, and AGC operation of a reception high-frequency unit corresponding to a radio wave environment is performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a broadcast microwave repeater (FPU) receiver, and more particularly to an FPU receiver improved in transmission quality deterioration due to interference of adjacent channel signal waves.

  2. Description of the Related Art Conventionally, in a receiving device of a broadcast wave microwave relay device, a received input electric field value and a bit error rate (BER) value are displayed on an operation panel, and the state of a transmission state is determined from these information. It was only. The high frequency level diagram until the received RF (high frequency) signal is input to the demodulator is automatically controlled using a gain variable circuit, but is fixedly and uniquely determined by the received electric field. It was a thing.

  In addition, as a conventional example for reducing adjacent channel signal wave interference, for example, Patent Document 1 obtains sufficient suppression of interference caused by adjacent channel signal waves by using a band pass filter so as to widen the frequency space between channels. There has been proposed a digital transmission apparatus configured as described above.

JP 2002-247004 A

  The frequency that can be used in the FPU receiver is that the channel interval is 18 MHz, and the occupied band of the modulated wave is substantially the same. The influence of the adjacent channel signal wave is one factor that determines the transmission quality in addition to the desired wave receiving electric field and modulation method.

  In the above-described prior art, when it is intended to operate only in the reception channel (desired wave) and the amplification stage is operated in a sufficiently linear region, the desired wave to disturbing wave ratio (D / U ratio) is −several tens. Since there is an adjacent channel signal wave of dB, when it is received, adjacent channel interference occurs due to adjacent wave interference, the amount of distortion becomes excessive, and a spectrum that cannot be demodulated is transmitted to the FPU reception control unit. . For this reason, problems such as interruption of broadcasting during transmission may occur.

  In order to cope with this problem, even if the D / U ratio is increased, if a level diagram of the internal high-frequency signal that can be transmitted is assembled, if there is no adjacent channel signal wave, the result is an overcompensated level diagram. There is a problem that the operation in a non-linear region becomes relatively large.

  Further, the FPU user determines the state of the transmission state by displaying the received electric field value and the BER value of the FPU receiver. When affected by the adjacent channel signal wave, a difference appears in the BER value estimated from the received electric field value, and the transmission quality is deteriorated. However, whether or not it is due to the deterioration of the characteristics of the device is immediately determined. There is also a problem that judgment cannot be obtained.

  Therefore, an object of the present invention is to make it possible to quantitatively determine the transmission state, to immediately determine that the transmission quality is deteriorated due to the interference of the adjacent channel signal wave, and to deteriorate the transmission quality due to the interference of the adjacent channel signal wave. It is an object of the present invention to provide an FPU receiving apparatus that can reduce the noise.

In order to solve the above problems, a microwave relay receiver according to the present invention includes a variable gain low noise amplifier, a bandpass filter for a desired wave, a bandpass filter for an adjacent wave, and a band for the desired wave. A desired wave detector for detecting a pass filter output; an adjacent wave detector for detecting the band pass filter output for the adjacent wave; a reception electric field display arithmetic circuit; and an operation panel including a display unit. ,
The received electric field display arithmetic circuit calculates the received electric field level of the desired wave and the adjacent wave based on the desired wave detector output and the adjacent wave detector output, and at least the received electric field level of the adjacent wave Is displayed on the operation panel, and the attenuation amount of the variable gain low noise amplifier is determined according to the maximum value of the calculated received electric field levels.

  According to the present invention, an AGC (Automatic Gain Control) circuit that is effective only when the power level of an adjacent channel signal wave is quantitatively detected and interference occurs due to the adjacent channel signal wave based on this information is provided. Therefore, overcompensation can be eliminated and operation in the linear region can be ensured.

  Embodiments of an FPU receiving apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the configuration of the FPU receiving apparatus of this embodiment. In the FPU receiver, an RF (high frequency) signal received by the receiving antenna ANT is input to a variable gain low noise amplifier 10 having a variable gain function via an RF band pass filter BPF1 connected to a terminal T1. The The output of the variable gain low noise amplifier 10 is input to one input terminal of the frequency converter 11 via the bandpass filter BPF2 in the RF band, and the oscillation frequency of the local oscillator 13 is input to the other input terminal. The Here, the local oscillator 13 uses an oscillator having a configuration in which the oscillation output is detected by the detector 16 and stable oscillation is obtained at a predetermined frequency by a PLL (Phase Locked Loop) circuit. The RF signal is mixed with the oscillation output of the local oscillator 13 in the frequency converter 11 and frequency-converted to a signal having a first intermediate frequency. The signal converted to the first intermediate frequency is further input to the frequency converter 12 via the bandpass filter BPF3 in the first intermediate frequency band, mixed with the oscillation output of the local oscillator 14, and the second intermediate frequency signal. Frequency conversion. The signal of the second intermediate frequency is fed back to the variable gain low noise amplifier 10 via the variable gain circuit 1 and the low noise amplifier AGC circuit 15 in the second intermediate frequency band, and the gain is corrected to a substantially constant power level. The The gain-corrected second intermediate frequency modulated wave is transmitted to the FPU reception control unit (demodulation unit) 22 via the coaxial cable 21 connected to the output terminal T2 of the variable gain circuit 1. At this time, the coaxial cable is used with a length ranging from several meters to about 300 meters depending on the utilization system. In the reception control unit 22, the power level reduced by the coaxial cable 21 is gain-corrected and applied to the demodulator 23. The demodulator 23 outputs the received information signal such as video / audio after the demodulation processing.

  In the FPU receiver according to the present invention, the variable gain circuit 1 shown in FIG. 1 is configured as shown in the block diagram of FIG. 2, thereby reducing the interference of adjacent channel signal waves.

  In FIG. 2, the second intermediate frequency signal frequency-converted by the frequency converter 12 of FIG. 1 is distributed by the distributor 24 connected to the terminal T, and the distributed signal is pre-amplifier 25 and distributor. 29. One signal of the second intermediate frequency distributed by the distributor 29 is input to the arithmetic circuit 1 via the band pass filter BPF 3A and the detection circuit 3. The other signal distributed by the distributor 29 is input to the arithmetic circuit 1 via the band pass filter BPF 4A and the detection circuit 4.

  The second intermediate frequency amplified by the preamplifier 25 is distributed by a distributor 27 via a SAW filter (Surface Acoustic Wave Filter) 26, and one of the distributed second intermediate frequencies is input to the gain variable circuit 2. The other is input to the bandpass filter BPF2A. The second intermediate frequency input to the gain variable circuit 2 is further distributed by the distributor 28 and detected by the detection circuit 1 via the bandpass filter BPF4 in the second intermediate frequency band. This detection output is fed back to the variable gain circuit 2, and after the gain of the variable gain circuit 2 is automatically adjusted to a gain determined corresponding to the detection output, as shown in FIG. The signal is input to the FPU reception control unit 22 through the coaxial cable 21 connected to the output terminal T2.

  On the other hand, the second intermediate frequency input to the band pass filter BPF2A is detected by the detection circuit 2, and the detection output is input to the arithmetic circuit 1. The output of the arithmetic circuit 1 is input to the reception electric field display arithmetic circuit 17 of FIG. 1 and fed back to the low noise amplifier AGC circuit 15 of FIG.

  Note that the second intermediate frequency amplified by the preamplifier 25 extracts only the desired wave by the SAW filter 26 in the second intermediate frequency band. In the system, even if the RF reception electric field is reduced to near the noise floor of the antenna by techniques such as quadrature modulation and error correction, the RF signal can be demodulated if the gain can be linearly corrected.

  In addition, since the FPU receiver is portable and can be used for short-distance transmission in the usage situation, it has the ability to receive even if the received electric field is -10 dBm to -20 dBm, but the D / U ratio is -several There are not a few radio wave environments that are over 10 dB. For this reason, the total gain of the reception high-frequency unit needs to be varied by approximately 10 dB to 100 dB.

  When the received electric field is relatively large within the receivable received power range, the signal-to-noise ratio (S / N ratio) is good. Therefore, the received RF band is attenuated by the variable gain low noise amplifier 10 of FIG. In the path from the converter 21 to the second intermediate frequency band SAW filter 42, the back-off from the saturation level of each element, that is, the difference between the saturation level of each element and the maximum received electric field level is taken, and the operation in the linear region is performed. Secure. If this attenuation is increased, the D / U ratio can be increased, but if overcompensation is performed, the transmission quality in the case where no U wave is present may be deteriorated. For this reason, in the second intermediate frequency band, this problem can be solved by determining the attenuation amount in accordance with the signal wave having a high reception electric field among the desired wave (D wave) or the adjacent channel signal wave.

  However, since this attenuation is one of the elements for calculating the desired wave received electric field by the received electric field display arithmetic circuit 17 in FIG. 1, there is a problem that a difference occurs in the indicated value of the desired wave received electric field display meter. Arise.

Therefore, as shown in FIG. 3, the band pass filter BPF2A of the second intermediate frequency band, the band pass filter for passing only a desired wave channel signal having a center frequency f _0, the second intermediate frequency band-pass filter BPF3A is f ₀ - The bandpass filter that passes only the lower adjacent channel signal having Δf as the center frequency and the bandpass filter BPF4A in the second intermediate frequency band are bandpass filters that pass only the upper adjacent channel signal having the center frequency of f ₀ + Δf. As shown in FIG. 2, each signal wave is detected by detection circuits 2-4. As a result, the received electric field values of the desired wave and the adjacent wave can be calculated quantitatively, and these electric field values are input to the CPU via the received electric field display arithmetic circuit 17 of FIG. It is possible to display the current received radio wave environment on the screen 20.

  Furthermore, it is possible to warn on the display screen that the transmission quality is deteriorated due to the influence of the adjacent channel wave signal. The vertical axis E of the desired wave received electric field display meter screen 20 indicates the received electric field level, and the horizontal axis t indicates time.

  Outputs obtained by detecting the signals extracted by the bandpass filters BPF2A, BPF3A, and BPF4A in the second intermediate frequency band by the detectors are compared in the arithmetic circuit 1, and the maximum one is selected. Output to the AGC circuit 15. The reception electric field display arithmetic circuit 17 converts the attenuation of the variable gain low noise amplifier 10 and the gain in the AGC circuit 15 for the low noise amplifier downstream of the second intermediate frequency band SAW filter 26 to obtain the reception electric field. ing. When the adjacent wave has a higher power level than the desired wave, that is, when the adjacent wave is received and interference is caused by the adjacent channel signal wave, the desired signal is output to the reception electric field display arithmetic circuit 17. The wave reception electric field can be corrected, and the problem that a difference occurs in the indicated value of the desired wave reception electric field display meter can be solved.

  For example, when the desired wave reception electric field is −40 dBm and the interference wave reception electric field is −30 dBm, the variable gain low noise amplifier 10 varies the gain so as to obtain a gain corresponding to the interference wave reception electric field. The detection output of the desired wave is detected as a received electric field of −40 dBm or less. Therefore, by adding the detection level difference between the desired wave and the interference wave to the desired wave detection output, the received electric field display calculation circuit 17 can process the desired wave received electric field as −40 dBm.

  The preferred embodiment of the FPU receiving apparatus according to the present invention has been described above, but the present invention is not limited to this embodiment, and various modifications can be made without departing from the spirit of the present invention. Of course. For example, in the embodiment, only the electric field level of the adjacent wave is displayed on the operation panel. However, the electric field level of the desired wave and the adjacent wave, and the BER value may be displayed. It goes without saying that a video monitor output function on which power level information is superimposed may be provided so that the transmission state can be determined quantitatively.

The block diagram which shows schematic structure of the microwave relay receiver which concerns on this invention. The block diagram which shows the circuit structure of the gain variable circuit 1 shown in FIG. FIG. 3 is a diagram illustrating an example of attenuation characteristics of a bandpass filter used in the reception high-frequency unit illustrated in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Variable gain low noise amplifier, 11, 12 ... Frequency converter, 13, 14 ... Oscillator, 15 ... AGC circuit for low noise amplifier, 16 ... Detector, 17 ... Arithmetic circuit for displaying received electric field, 18 ... CPU, DESCRIPTION OF SYMBOLS 19 ... Operation panel, 20 ... Receive electric field display meter screen, 21 ... Coaxial cable, 22 ... FPU reception control part, 23 ... Demodulator, 24 ... Distributor, 25 ... Preamplifier, 26 ... SAW filter, 27-29 ... distributor, 30 ... amplifier, ANT ... antenna, T, BPF1 to BPF4 ... bandpass filter, BPF2A, BPF3A, BPF4A ... bandpass filter, T1, T2 ... terminals.

Claims (1)

Variable gain low noise amplifier, bandpass filter for desired wave, bandpass filter for adjacent wave, desired wave detector for detecting bandpass filter output for desired wave, and for adjacent wave An adjacent wave detector for detecting the band-pass filter output, a reception electric field display arithmetic circuit, and an operation panel including a display unit;
The received electric field display arithmetic circuit calculates the received electric field level of the desired wave and the adjacent wave based on the desired wave detector output and the adjacent wave detector output, and at least the received electric field level of the adjacent wave Is displayed on the operation panel, and the attenuation amount of the variable gain low noise amplifier is determined according to the maximum value of the calculated received electric field levels.

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