JP2827875B2 - Microwave band signal generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave band signal generator, and more particularly to a signal generator for generating a wide range of microwave band reference signals at the time of transmission test of digital microwave communication equipment.

[0002]

2. Description of the Related Art When confirming the electrical characteristics of a receiving apparatus during a transmission test of digital microwave communication equipment,
The test is performed by combining transmitters that match the reception frequency. However, when a transmission device having the same frequency cannot be prepared, a new transmission device is manufactured or a different transmission device having a different frequency is used.

[0003]

However, when trying to change the frequency of the transmitter to the target frequency, tuning of the microwave band filter and changing the frequency of the local oscillator are difficult, and each time the cost is high. There was a problem that it took.

Therefore, in order to cover a wide microwave band from 1 GHz to several GHz, an intermediate frequency band (IF
Band), the frequency of the VHF band signal generator is changed, and an electronic tuning type band pass filter (BPF) is used.
(Hereinafter referred to as an electronic tuning BPF) and an amplifier may be used to obtain a reference signal for testing. However, in this method, since the group delay and amplitude characteristics of the electronic tuning BPF change every time tuning is performed, there is a problem that characteristics as a signal generator for testing cannot be obtained.

Japanese Utility Model Laid-Open Publication No. Hei 3-2716 discloses a multi-frequency oscillating unit that generates a low-frequency multi-frequency signal, converts the multi-frequency signal into a microwave band by a first frequency conversion circuit, A multi-frequency synthesized microwave signal generation circuit that obtains a desired frequency signal by using this method has been proposed, but does not describe correction of amplitude distortion or group delay distortion.

The present invention has been proposed in order to solve such problems of the prior art, and eliminates amplitude deviation and group delay deviation generated in an electronic tuning BPF and an amplifier, and can be used in a wide microwave band. It is an object of the present invention to provide a microwave signal generator capable of covering the generation of the reference signal by a single device.

[0007]

In order to achieve this object, a microwave signal generator according to the first aspect of the present invention comprises: a signal generator for outputting a signal in a VHF band as an intermediate frequency; Frequency conversion means for converting a signal from the generator to a desired microwave band frequency, and an amplitude distortion and a group delay distortion which are inserted between the signal generator and the frequency conversion means and are generated in the microwave band. An amplitude group delay equalizer for receiving and equalizing a control signal, a microwave band electronic tuning bandpass filter for filtering and selecting a microwave signal from the frequency conversion means, and a microwave band electronic tuning band. An amplifier for amplifying the microwave signal from the pass filter, a splitter for splitting the signal from the amplifier into an output signal for transmission and a signal for detection, and a splitter for detection from the splitter Frequency converting means for converting a signal into an intermediate frequency band signal, and an amplitude generated by the microwave band electronic tuning band pass filter and the amplifier mainly upon receiving the intermediate frequency band signal from the detecting frequency converting means. The detector includes a detector that detects distortion and group delay distortion, and sends a control signal for correcting the amplitude distortion and group delay distortion to the amplitude group delay equalizer.

According to a second aspect of the present invention, the frequency conversion means comprises a first frequency converter and a second frequency converter, and the detection frequency conversion means comprises a detection first frequency converter. And a second frequency converter for detection, and a local oscillator that sends a local oscillation signal to the first frequency converter and the second frequency converter for detection is shared, and the second frequency converter and the first frequency converter for detection are used. A local oscillator for transmitting a local oscillation signal to the device is shared.

[0009]

According to the above-described structure, the detector mainly detects the amplitude distortion and the group delay distortion generated in the microwave band electronic tuning band-pass filter and the amplifier, and receives the control signal from the detector. By equalizing the amplitude distortion and the group delay distortion by the group delay equalizer, it is possible to generate a desired microwave band transmission signal free from the amplitude distortion and the group delay distortion.

[0010]

Embodiments of 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 microwave band signal generator according to the present invention. In this figure, an IF band signal generator 1 is composed of a digital modulator and generates a VHF band signal which is an intermediate frequency before frequency conversion into a microwave band. From the IF band signal generator 1, for example, 4PSK (phase-shift keying), 8PSK,
16QAM (quadra-ture amplitude modulation), 64
Modulated signals of QAM, 128 QAM, and 250 QAM can be output. Here, PSK is phase shift keying, and QAM is multilevel quadrature amplitude modulation.

Between the IF band signal generator 1 and the first frequency converter 3, an amplitude group delay equalizer 2 composed of an IF band transversal equalizer or TRV is inserted. The specific configuration of the amplitude group delay equalizer 2 will be described later in detail with reference to FIG.

A second frequency converter 4 comprising a microwave band frequency synthesizer following the next stage, a microwave band electronic tuning / bandpass filter 5 (hereinafter referred to as microwave band electronic tuning BPF5), an amplifier 6, a distributor 7, and The attenuator 8 forms an output signal system. The control of the microwave band electronic tuning BPF 5 is performed by the BPF controller 11.

On the other hand, the first frequency converter for detection 12 connected to the distributor 7 and the second frequency converter for detection 1 following the next stage
3 and a detector 14 comprising a digital demodulator mainly detect the amplitude distortion and the group delay distortion generated by the microwave band electronic tuning BPF 5 and the amplifier 6 and control the amplitude group delay equalizer 2. It constitutes a signal detection system. The specific configuration of the detector 14 will be described later in detail with reference to FIG.

The first local oscillator 9 includes the first frequency converter 3
The second local oscillator 10 is shared by the second frequency converter 4 and the first frequency converter 12 for detection.

The data input unit and the display 16 are provided on the front panel of the control panel 15, and can perform input setting of a desired transmission frequency on the control panel 15, and display the input result and the like. Thus, when testing a device having a different frequency, the frequency can be set with one touch from the front panel. An external interface panel 17 connected to the control panel 15 is provided for externally setting a transmission frequency and the like by remote control. From the control panel 15, frequency data for setting the transmission frequency is sent to the second local oscillator 10, and the BPF controller 1
1 is sent control data.

Next, the operation of the microwave signal generator constructed as described above will be described. First, a VHF band signal, which is an intermediate frequency generated by the IF band signal generator 1, passes through an amplitude group delay equalizer 2 and is sent to a first frequency converter 3, where the first frequency converter 3 Is mixed with the local oscillation signal from the first local oscillator 9 and frequency-converted into a signal in the microwave band, and the band is limited by the BPF in the converter 3. The signal in this microwave band is
The signal is mixed with the local oscillation signal from the second local oscillator 10 by the second frequency converter 4 at the next stage, thereby being converted into a desired transmission frequency.
5 is selected for filtering. Frequency data for setting a transmission frequency is sent from the control panel 15 to the second local oscillator 10. A control signal to the microwave band electronic tuning BPF 5 is supplied from the BPF controller 11.

The microwave signal selected by the microwave band electronic tuning BPF 5 is amplified by the amplifier 6 to a signal of a required magnitude, and the signal level is kept constant by the automatic amplitude control circuit (ALC) provided in the amplifier 6. Controlled. The output signal of the amplifier 6 is divided by the divider 7 into a transmission output signal and a control signal detection system detection signal.
The transmission output signal passes through the attenuator 8 whose attenuation is set by a signal from the control panel 15 and is output to the output terminal 18 as a carrier wave in the microwave band.

On the other hand, the detection signal branched by the distributor 7 is sent to the second local oscillator 10 by the first frequency converter 12 for detection.
, And frequency-converted, and band-limited by the BPF in the converter 12. Further, the signal is sent to the second frequency converter 13 for detection and mixed with the local oscillation signal from the first local oscillator 9 to be frequency-converted into an intermediate frequency band (IF band). After the band is limited, the gain is further controlled by an automatic gain control circuit (AGC).

The AGC-controlled intermediate frequency signal is demodulated by the detector 14 and amplitude distortion (amplitude deviation) mainly generated by the microwave band electronic tuning BPF 5 and the amplifier 6.
And group delay distortion (group delay deviation) are detected. This allows
In the detector 14, a quadrant signal and an error signal which are control signals for the amplitude group delay equalizer 2 are generated. Where the quadrant signal is
The data P channel signal (Pch signal) and the data Q channel signal (Qch signal) are used, and the error signal is made up of the error Pch signal and the error Qch signal.

The quadrant signal and the error signal detected by the detector 14 are sent to the amplitude group delay equalizer 2. Accordingly, the amplitude group delay equalizer 2 correlates the demodulated quadrant signal and the error signal, and controls the weight of each tap of the transversal filter to reduce the amplitude distortion generated in the microwave band. Group delay distortion is equalized in the IF band.

By this signal processing, the amplitude distortion and the group delay distortion generated in the microwave band electronic tuning BPF 5 and the amplifier 6 can be corrected, and the microwave band (1 GHz to several GHz) free of the amplitude distortion and the group delay distortion is required. The transmission signal of the frequency to be transmitted can be instantaneously transmitted from the output terminal 18.

The amplitude distortion and group delay distortion of the first frequency converter 3, the second frequency converter 4, the first frequency converter 12 for detection, and the second frequency converter 13 for detection have no influence on the characteristics. Designed to be. Further, since the amplitude group delay equalizer 2 and the detector 14 need to be used in accordance with the IF band signal generator 1, they are configured in a unit type or can be switched by a switch.

Next, the detailed configuration and operation of the amplitude group delay equalizer 2 and the detector 14 will be further described. FIG. 2 shows an amplitude group delay equalizer 2 having, for example, a 5-tap configuration. The amplitude group delay equalizer 2 includes four delay lines T _-2 , T _-1 , T ₁ , and T ₂ equal to the clock cycle of the IF band signal generator 1. Ci _-2 , Ci _-1 , Ci ₁ , Ci ₂ and Cr _-2 , C
r ₋₁ , Cr ₁ and Cr ₂ are variable weighting circuits. Here, the subscript “−2” advances by 2 bits, and the subscript “−1”.
Is one bit ahead, the subscript “1” corresponds to one bit delay, and the subscript “2” corresponds to two bits delay. Center tap C ₀
Corresponds to time 0. Reference numerals 19, 20, and 21 denote signal synthesis circuits, and reference numeral 22 denotes a control signal generation circuit.

A method of equalizing the amplitude group delay will be described. The impulse response at the time of no distortion is shown by a dotted line in FIG. 3A. When T is a clock cycle, the amplitude is zero at each sample point of t = nT, that is, there is no intersymbol interference. Note that the clock cycle is set to about 20 nsec. However, when distortion occurs in the transmission path, an impulse response shown, for example, by a solid line occurs, and intersymbol interference occurs at each sample point. In the example shown in FIG. 3A, t = ±
At T, particularly large intersymbol interferences A and B occur. Now, considering demodulated signal sequences S ₋₁ , S ₀ , and S ₁ (the amplitudes are assumed to be equal), at sample points at t = 0, intersymbol interference from S ₋₁ to A and S ₁ to B is S _It is superimposed on ₀ , and correct identification cannot be performed.

To remove intersymbol interference A and B from ± 1 bit shown in FIG. 3B, the following is performed. Delay line T
The signal S ₁ one bit before held by _{1 is} made to have the same amplitude and opposite phase with respect to the interference B by the variable weighting circuits Ci ₁ and Cr ₁ , and if this is added to the main signal S ₀ , the code from S ₁ Interference B can be removed. The same applies to intersymbol interference A. Thereby, the amplitude distortion and the group delay distortion generated in the microwave band electronic tuning BPF 5 and the amplifier 6 can be equalized.

Next, a method of detecting an error signal will be described.
The signal waveform at the time of no distortion is 4 at the sampling point in the case of 16QAM.
Has converged to the value. If these four values are set as a reference level, an error signal can be detected from a deviation from the reference level.

A determination is made as to which pulse of the preceding and following pulse train this error originated from by correlating the error signal and the data signal downward with a fixed time relationship, and controlling only taps having a causal relationship. The error to zero. This is called a ZF (zero focing) control method.

Next, the signal flow will be described by taking the detector 14 in the case of 16QAM shown in FIG. 4 as an example. 16QA
The M input signal is amplified to a fixed level by an AGC amplifier 23 to which an AGC signal is sent from a logic circuit 28, and then divided into two signals of Pch and Qch by a hybrid transformer 24. These two series of signals are output to the logic circuit 28.
Are automatically detected by a synchronous detection circuit 25 to which an automatic phase control (APC) signal is sent. In this synchronous detection,
In the case of Pch, the IF signal of 16QAM is detected by a reproduced carrier having a phase indicated by an arrow as shown in FIG. 5, and a baseband signal (eye pattern) having a quaternary value as shown by a is detected. Similarly, in Qch, a carrier having a 90 ° phase shift is detected to generate a quaternary signal a ′. a and b (a
'And b') are exactly the same.

C ₀ and c ₀ ′ are obtained by full-wave rectification of the signals a and a ′ by full-wave rectifiers 26 and 27, respectively. identification, and outputs the four columns baseband signal of _{S 11, S 12, S 21} , S 22 from the logic circuit 29.

The error signal is 4 value converges may be set as the reference level, in FIG. _{6 c +, c - (c} + ', c -
The deviation is detected by reading the deviation from the reference signal level of the convergence point subjected to full-wave rectification as in).

[0031] c _+, c _- a c ₊ ', c _-' the error signal detected from, are used as the control signal of the AGC circuit of the baseband type. B ₀ , c ₊ , c ₀ , c ₋
And the error signals due to b ₀ ′, c ₊ ′, and c ₋ ′ are used for synchronizing the phase and regenerating the carrier. Also, Pc
The respective error signals of h and Qch are sent to the baseband interference canceller and the amplitude group delay equalizer 2.

[0032]

As described above, according to the present invention, amplitude distortion and group delay distortion mainly generated by a microwave band electronic tuning BPF and an amplifier are detected and equalized by an amplitude group delay equalizer. Wide frequency range of microwave
It can be covered by a single device and can easily transmit the required test microwave signal without amplitude distortion and group delay distortion. As a result, in the transmission test of digital microwave communication equipment, there is no need to manufacture a new transmission device that matches the reception frequency or to change the frequency of the transmission device to a frequency that matches the reception frequency. It is possible to significantly reduce the number of inspection steps and cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a microwave band signal generator according to the present invention.

FIG. 2 is a block diagram showing a specific configuration of an amplitude group delay equalizer.

3A and 3B are diagrams for explaining the operation of an amplitude group delay equalizer, wherein FIG. 3A shows an impulse response when there is no distortion and when a distortion occurs in a transmission path, and FIG. Is shown.

FIG. 4 is a block diagram showing a specific configuration of a detector.

FIG. 5 is a diagram for explaining an operation of detecting baseband signals in four columns.

FIG. 6 is a diagram for explaining an operation of detecting an error signal.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 IF band signal generator 2 Amplitude group delay equalizer 3 First frequency converter 4 Second frequency converter 5 Microwave band electronic tuning BPF 6 Amplifier 7 Distributor 8 Attenuator 9 First local oscillator 10 Second local oscillator Reference Signs List 11 BPF controller 12 First frequency converter for detection 13 Second frequency converter for detection 14 Detector 15 Control panel 16 Data input unit and display 17 External interface panel

Claims (2)

(57) [Claims] A signal generator for outputting a signal in a VHF band serving as an intermediate frequency; frequency conversion means for converting a signal from the signal generator into a frequency in a desired microwave band; An amplitude group delay equalizer that is inserted between the frequency conversion unit and receives and equalizes the amplitude distortion and the group delay distortion generated in the microwave band by receiving the control signal. A microwave band electronic tuning / bandpass filter for selecting a filter, an amplifier for amplifying a microwave signal from the microwave band electronic tuning / bandpass filter, an output signal for transmission from the amplifier and a detection signal A frequency divider for converting the detection signal from the distributor into an intermediate frequency band signal; and an intermediate signal from the frequency converter for detection. Receiving the waveband signal, detecting the amplitude distortion and the group delay distortion mainly generated in the microwave band electronic tuning bandpass filter and the amplifier, and transmitting the control signal for correcting the amplitude distortion and the group delay distortion to the above. A microwave band signal generating apparatus, comprising: a detector for transmitting the signal to an amplitude group delay equalizer. 2. The frequency conversion means comprises a first frequency converter and a second frequency converter, and the detection frequency conversion means comprises a detection first frequency converter and a detection second frequency converter. A local oscillator for transmitting a local oscillation signal to the first frequency converter and the second frequency converter for detection, and a local oscillator for transmitting a local oscillation signal to the second frequency converter and the first frequency converter for detection. 2. The microwave band signal generator according to claim 1, wherein the oscillator is shared.