JP2832750B2 - Receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field of the Present Invention> The present invention relates to a wideband receiving apparatus that converts a received signal into a predetermined intermediate frequency band by using a local oscillation signal.

<Related Art> For example, in a receiving apparatus that performs frequency analysis over a wide band, such as a spectrum analyzer, a high-level signal component included in an input signal saturates a mixer or causes cross-modulation, so that accurate frequency analysis is performed. May not be possible.

Further, when the receiving frequency range is wider than the intermediate frequency at the forefront stage or when a harmonic mixer is used, many spurious components such as images are generated.

For this reason, a variable filter (tracking filter) in which the tuning frequency is varied in accordance with the frequency of the local oscillation signal is provided at the previous stage of the mixer, and only the signal component near the reception frequency corresponding to the local oscillation signal is input to the mixer. Conventionally, there has been a receiving apparatus configured as described above.

It is necessary to control the tuning frequency of this variable filter so as to be constantly shifted from the local oscillation frequency by the intermediate frequency over the entire reception band.In order to prevent spurious noise, the pass band of the filter must be controlled. The smaller the value, the more effective.

However, even if the local oscillation frequency can be stabilized by using the PLL circuit technology, the tuning frequency of the filter is susceptible to temperature changes and aging. Several dB for level
受 信 Receive and measure a level that is several tens of dB lower.

For this reason, in a receiving device that automatically sweeps a reception frequency like a spectrum analyzer and analyzes the level of a signal included in the reception frequency range, the tuning frequency of the variable filter is varied by following the local oscillation frequency. An adjustment circuit that can externally correct the control signal of
Receives a stable signal of the level and frequency included in the measurement signal, operates the adjustment circuit to maximize the level of the received signal, and outputs the output of an external oscillator such as a comb generator to the input terminal of the receiver. In the connected state, the adjustment by this adjustment circuit is performed to correct the tracking deviation.

<Problem to be Solved> However, when the level and frequency of the signal included in the measurement signal are constantly changing, the above-described adjustment cannot be performed. In addition, it is very troublesome to use an external oscillator such as a comb generator every time tracking deviation is corrected.

For this reason, a receiver in which an oscillator such as a comb generator is provided in the receiver and this oscillation output is connected to the input side by a switch operation has been realized. Is very expensive.

For this reason, there has been a strong demand for a receiver that can easily correct the tracking deviation without using special equipment.

An object of the present invention is to provide a receiving device that solves this problem.

<Means for Solving the Problem> In order to solve the above problem, the receiving apparatus of the present invention can change the tuning frequency and selectively select a signal component near the tuning frequency among signal components input from the input terminal. A variable filter that passes therethrough; a local oscillator that varies the frequency of the local oscillation signal in accordance with the oscillation control signal; a frequency mixing of the output signal of the variable filter and the local oscillation signal; and a detection function for the input signal. Mixer, an intermediate frequency filter that passes a signal component of a predetermined intermediate frequency band from a mixed component from the mixer, a tuning control signal for setting a tuning frequency of the variable filter to a desired reception frequency, and a frequency of a local oscillation signal. A tracking control means for outputting an oscillation control signal for setting a frequency at which the signal component of the desired reception frequency passes through the intermediate filter; Variable filter control means for setting the tuning frequency of the variable filter in accordance with the control signal; and an oscillation control signal for making the frequency of the local oscillation signal or its harmonic signal equal to the tuning frequency of the variable filter.
Calibration control means for outputting to a local oscillator instead of the tracking control means and switching and connecting the local oscillation signal output to the mixer to the input side of the variable filter, and the local oscillation signal or its harmonics by the calibration control means Correcting means for correcting the set value of the variable filter control means for the variable filter such that after the frequency of the signal is set near the tuning frequency of the variable filter, the detection level detected by the detection operation of the mixer is maximized. ing.

<Operation> Therefore, after the frequency of the local oscillation signal or its harmonic signal is set to the desired tuning frequency of the variable filter by the calibration control means, the detection level of the local oscillation signal detected by the mixer after passing through the variable filter is changed. If the set value from the variable filter control means for the variable filter is corrected by the correction means so as to become the maximum, the tracking deviation of the variable filter at the desired tuning frequency is corrected.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a front end portion of a spectrum analyzer using a harmonic mixing method.

In FIG. 1, reference numeral 2 denotes a variable attenuator that attenuates a signal input from an input terminal 1 by an amount corresponding to a control signal, and 3 denotes a tuning control voltage from Va to Vb, as shown in FIG. This is a variable filter whose tuning frequency is varied from 1.5 to 23 GHz according to Vf, and is constituted by a YIG resonator.

Reference numeral 4 denotes a variable filter control circuit which shifts a tuning control voltage input via a switch 13 described later by a correction amount α output from the manual correction circuit 5 and applies the same to the variable filter 3. By doing so, the tuning frequency of the variable filter 3 can be finely adjusted.

Reference numeral 6 denotes a harmonic mixer. As shown in FIG. 3, a signal passing through the variable filter 3 and a local signal input through a directional coupler 6a are mixed by a diode 6b.
A signal component of a difference between a signal component of an integral multiple of the local oscillation frequency and an output signal of the variable filter 3 is output ( _R0 is a terminating resistor). Further, the harmonic mixer 6 can detect an input signal by the detecting action of the diode 6b and output the detection level. Incidentally, R ₁ is the resistance of the bias applied, C _1, R ₂ is the resistance and a filter capacitor for smoothing the output of the detection signal.

Reference numeral 7 denotes an intermediate frequency filter having a pass center frequency of 0.5 GHz.

8, as shown in FIG. 4, and outputs a local oscillation signal of 2~6GHz example, in response to the oscillation control voltage V ₀ which from Vc to Vd YI
This is a local oscillator composed of a G oscillator.

9 is reception frequency data corresponding to a desired reception frequency
Upon receiving Df, a tuning control voltage is output so that the tuning frequency of the variable filter 3 becomes the desired receiving frequency, and the frequency of the local oscillation signal is converted from the signal of the desired receiving frequency to an intermediate frequency (0.5 GHz). This is a tracking control unit that outputs an oscillation control voltage for achieving a frequency to be set.

FIG. 5 shows the relationship between the control frequency output and the reception frequency data Df of the tracking control means 9,
The tuning control voltage Vf for the variable filter 3 changes linearly from Va to Vb in the reception frequency range of 1.5 to 23 GHz.

On the other hand, the oscillation control voltage V ₀ for the local oscillator 8
Is a voltage corresponding to a local oscillation frequency that is always an integer fraction of a frequency 0.5 GHz higher than the tuning frequency of the variable filter.

That is, for a reception frequency of 1.5 to 5.5 GHz, a voltage from Vc to Vd for a local oscillation frequency of 2 to 6 GHz is output for mixing with a fundamental wave, and the reception frequency is 5.5 to 11.
Until 5GHz because of mixing by the second-order harmonic, the local oscillation frequency output voltage from V ₁ of the for the 3~6GHz to Vd. Also, if the reception frequency is 11.5-17.5 GHz,
Local frequency is 4 due to mixing by 3rd harmonic.
Outputs a voltage from V ₂ to Vd for the ~6GHz, 17.5
For mixing GHz or more by the fourth harmonic, the local oscillation frequency output voltage from V ₃ to the 4.5~6GHz to Vd.

Therefore, from the tracking control means 9, as shown in FIG. 6, the tuning frequency of the variable filter 3 is equal to the desired reception frequency, and the frequency of the local oscillation signal or its harmonic signal is higher than the desired reception frequency by 0.5 GHz. A control voltage for the frequency is output.

Reference numeral 10 denotes a tracking control unit that receives the calibration command signal, and controls the oscillation control voltage and the tuning control voltage for the local oscillation frequency of the local oscillator 8 and the tuning frequency of the variable filter 3 to become the set calibration frequency. 9 is a calibration control means that outputs in place of 9 and sets the attenuation of the variable attenuator 2 to the maximum.

11 to 13 are based on the switching signal from the calibration control means 10,
The respective control voltages of the calibration control means 10 are respectively applied to the variable attenuator 2,
A switch 14 for switching and inputting to the local oscillator 8 and the variable filter control means 4 is a switching signal from the calibration control means 10 and converts the local signal from the harmonic mixer 6 to the variable filter 3.
The switch is connected to the input side of the device through a directional coupler 15.

Reference numeral 16 denotes a display for displaying a detection level detected by the detection operation of the harmonic mixer 6.

Reference numeral 17 denotes an attenuation control circuit that controls the amount of attenuation of the variable attenuator 2 during normal spectrum measurement.

 Next, the operation of the receiving apparatus will be described.

Assuming that an irregular measurement signal whose level and frequency change every moment is input and tracking correction cannot be performed by this measurement signal, as shown in FIG. Is assumed to cause a tracking shift by Δf from 0.5 GHz when the correction amount α of the manual correction circuit 5 is zero.

Here, for example, when the calibration frequency is set to 4 GHz and a calibration command signal is input to the calibration control means 10, the variable attenuator 2
Is set to the maximum and the variable filter 3
The tuning control voltage V ₄ and the oscillation control voltage V ₂ (see FIG. 5) for causing the tuning frequency of the local oscillator 8 and the local oscillation frequency of the local oscillator 8 to be 4 GHz are output to the variable filter control circuit 4 and the local oscillator 8, respectively. .

Therefore, although the tuning frequencies F ₁ and the local oscillation frequency F ₂ of the variable filter 3 as shown in FIG. 8 together changed in the vicinity of 4 GHz, a state in which detuned by a frequency difference Δf by the tracking deviation, harmonics mixer The level of the local oscillation signal detected by the detection operation 6 is lower than the center (tuning frequency) of the pass characteristic A of the variable filter 3 by d.

Here, by operating the manual correction circuit 5 while checking the level of the display 16 and setting the correction amount α at which the detection level becomes maximum in the variable filter control circuit 4, the tuning frequency of the variable filter 3 and the local oscillation The frequency and the frequency coincide, and if the measurement state is returned with this correction amount α, the difference between the tuning frequency and the local oscillation frequency (including harmonics) is the intermediate frequency (0.5 GHz).
And the tracking error disappears.

In general, tracking deviation occurs almost uniformly over a wide band. Therefore, after performing calibration at 4 GHz as described above, if this calibration control state is released, there is no tracking deviation in a wide band including the calibration frequency. Reception measurement becomes possible.

This calibration process may be performed at a plurality of different calibration frequencies.

During this calibration operation, even if a measurement signal including a frequency signal substantially equal to the calibration frequency is input, the variable attenuator 2
, The calibration operation is not hindered.

<Another embodiment of the present invention> Note that the calibration control means of the above embodiment controls both the tuning frequency of the variable filter and the local oscillation frequency of the local oscillator so as to be a preset calibration frequency. Although the voltage has been output, only the control voltage for the local oscillator may be varied so that the local oscillation frequency or its harmonic frequency matches the tuning frequency of the variable filter.

In the above embodiment, the tuning control signal for the variable filter is manually corrected.
As shown in the figure, at the time of calibration, the detection level from the harmonic mixer 6 is stored in the memory 20 while the correction amount from the correction circuit 5 'is automatically varied within a predetermined range, and the correction amount at which the maximum detection level is obtained is varied. The calibration control means 10 'may be configured to automatically set the filter control circuit 4. In the case of such a configuration, for example, a calibration command signal is output from a timer or the like every predetermined time, and the timing of calibration can be automated.

Further, the manual correction circuit 5 of the above embodiment shift-corrects the tuning control voltage for the variable filter. However, if the tracking deviation is not uniform depending on the reception band, the variable filter control circuit for the tuning control voltage is used. Of the sensitivity (correction of the inclination) may be made possible.

<Effects of the Present Invention> As described above, the receiving apparatus of the present invention
Adjust the local oscillation frequency to the tuning frequency of the variable filter, switch to the input side of the variable filter, detect the level of the input local oscillation signal by the detection function of the mixer, and adjust the tuning frequency of the variable filter so that the detected level becomes maximum. Since the tracking deviation can be eliminated by correcting the value for setting, the tracking correction can be performed extremely easily even without an input signal without using an expensive external oscillator such as a comb generator. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention, FIG. 2 is a characteristic diagram of a main part of the embodiment, FIG. 3 is a circuit diagram showing a configuration of a main part of the embodiment, FIG. 4 is a characteristic diagram of the main part of one embodiment, FIGS. 5 and 6 are diagrams for explaining the operation of the main part of the embodiment, and FIGS. FIG. 9 is a block diagram illustrating the configuration of another embodiment of the present invention. 2 ... variable attenuator, 3 ... variable filter, 4 ... variable filter control circuit, 5 ... manual correction circuit, 6 ... harmonic mixer, 7 ... intermediate frequency filter, 8 ... local oscillator, 9
…… Tracking control means, 10 …… Calibration control means.

Claims (2)

(57) [Claims] A tuning filter that can vary a tuning frequency and selectively passes a signal component near a tuning frequency among signal components input from an input terminal; and a filter that adjusts a frequency of a local oscillation signal according to an oscillation control signal. A local oscillator to be varied, a frequency mixer between the output signal of the variable filter and the local oscillation signal, and a mixer having a detection function for an input signal; and a predetermined intermediate frequency band from a mixed component from the mixer. An intermediate frequency filter that passes the signal component of the variable filter, a tuning control signal for setting the tuning frequency of the variable filter to a desired reception frequency, and the frequency of the local oscillation signal, the signal component of the desired reception frequency to the intermediate Tracking control means for outputting an oscillation control signal for setting a frequency to be passed through the filter; and a variable filter corresponding to the tuning control signal. Variable filter control means for setting the tuning frequency of, the oscillation control signal for equalizing the frequency of the local oscillation signal or its harmonic signal to the tuning frequency of the variable filter, instead of the tracking control means, While outputting to the local oscillator, calibration control means for switching and connecting the local oscillation signal output to the mixer to the input side of the variable filter, the calibration control means for the local oscillation signal or its harmonic signal After the frequency is set near the tuning frequency of the variable filter, correction means for correcting the set value of the variable filter control means for the variable filter so that the detection level detected by the detection operation of the mixer is maximized. And correcting a tracking deviation of a tuning frequency of the variable filter with respect to the local oscillation frequency. Apparatus. 2. A variable attenuator for attenuating a signal input to the input terminal and outputting the attenuated signal to the variable filter, wherein the calibration control means adjusts a frequency of the local oscillation signal or a harmonic signal thereof. An oscillation control signal for equalizing the tuning frequency of the variable filter is output to the local oscillator instead of the tracking control means, and the local oscillation signal is switched to the input side of the variable filter, and the variable attenuator is output. 2. The receiving apparatus according to claim 1, wherein the receiving apparatus outputs a control signal for maximizing an amount of attenuation.