JPH0322106B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a wideband receiver that measures a wide band, such as a spectrum analyzer.

"Background" For example, an input circuit of a spectrum analyzer or a frequency counter is provided with a heralodyne receiving circuit for frequency conversion. Since this receiving circuit has a wide frequency band to be measured, it uses not only the fundamental wave of the local oscillator but also harmonics to perform frequency conversion.

For example, if the measurement target is from 1 GHz to 10 GHz, if the oscillation frequency of the local oscillator can be swept from 1 GHz to 10 GHz, the input signal given will be converted to an intermediate frequency somewhere between 1 GHz and 10 GHz and captured. be able to.

However, it is difficult to sweep a local oscillator over a wide band such as 1 GHz to 10 GHz. For this reason, in general, a local oscillator that can sweep oscillate from 1 GHz to 2 GHz is provided, and this local oscillator generates even-order and odd-order harmonic components for the fundamental wave component of 1 GHz to 2 GHz. Depending on 2~3GHz, 3~4GHz, 4~5G
Hz, 5~6GHz, 6~7GHz, 7~8GHz, 8~9G
Hz, 9 to 10 GHz, and use these harmonic components to sweep all the desired bands, so that even if a signal with an unknown frequency is input, the signal If the frequency is between 1 and 10 GHz, the input signal can be converted into an intermediate frequency signal by any of the harmonic components and can be received.

By the way, the harmonic components output from the local oscillator have different signal levels with respect to the fundamental wave, and the DC components are also not constant. Therefore, the operating point of the frequency converter is not constant, and the conversion efficiency varies depending on the level of the local oscillation signal, the DC component, and the like. Therefore, there is an inconvenience that reception sensitivity differs depending on which harmonic is used to convert an input signal into an intermediate frequency signal.

The receiving sensitivity can be adjusted by appropriately selecting the operating point of the frequency converter. For this reason, it has conventionally been possible to adjust the bias voltage applied to the frequency converter, so that the reception sensitivity can be adjusted to the best condition.

"Prior Art" FIG. 4 shows an example of a conventional wideband receiver. In the figure, 1 is an input terminal, 2 is a frequency converter, and 3 is a local oscillator. As this local oscillator 3, a voltage controlled oscillator such as a YIG oscillator is used, for example. Reference numeral 4 denotes a sweep voltage generator that applies a sweep voltage such as a sawtooth wave voltage or a triangular wave to the local oscillator 3 to sweep the oscillation frequency of the local oscillator 3. Reference numeral 5 indicates a bias supply circuit that provides a bias voltage to the frequency converter 2. The bias supply circuit 5 adjusts the bias voltage applied to the frequency converter 2, thereby making it possible to adjust the receiving sensitivity.

6 is a bandpass filter for extracting an intermediate frequency signal, and 7 is an amplifier.

"Problems to be Solved by the Invention" Conventionally, the bias voltage supplied from the bias voltage supply circuit 5 is manually adjusted to ensure that the level of the intermediate frequency signal obtained at the output side of the amplifier 7, that is, the output terminal 8 is at the maximum level. An operation was required to make the adjustment so that the operation was troublesome.

In addition, since the operation is troublesome, if the frequency of the input signal is analyzed or the frequency of the input signal is measured without adjusting the receiving sensitivity, the measurement accuracy will deteriorate because the measurement will be performed with a poor signal-to-noise ratio.

Therefore, it is an object of the present invention to provide a wideband receiver configured to generate a bias voltage so as to automatically bring the reception sensitivity to the best point.

"Means for Solving the Problem" In the present invention, the controller applies different bias voltages to the frequency converter for each frequency sweep operation, and the maximum detection means generates an intermediate frequency signal obtained by changing the bias voltage. The controller measures the level of the bias voltage and detects the value of the bias voltage that provides the maximum intermediate frequency signal as a result of multiple frequency sweeps, and controls the bias voltage supply circuit to apply this bias voltage to the frequency converter. , the frequency sweep voltage from which the intermediate frequency signal is obtained is controlled to be applied from the sweep voltage generator to the local oscillator. or keep the local oscillator in frequency sweep.

In this way, when an input signal is given, the optimum bias voltage to be applied to the frequency converter is detected, and the optimum bias voltage is applied to the frequency converter to automatically set the best reception state.

Therefore, according to the present invention, even if a signal of an unknown frequency is given, the signal can be automatically received in the best condition. Therefore, it is possible to construct a device that is easy to handle.

"Embodiment" FIG. 1 shows an embodiment of the present invention. In FIG. 1, parts corresponding to those in FIG. 4 are designated by the same reference numerals.

In this invention, a controller 11 is provided, and the bias voltage supply circuit 5 is controlled by the controller 11 so that the value of the bias voltage applied to the frequency converter 2 is changed every time the local oscillator 3 performs a sweep operation. Configure.

The bias voltage supply circuit 5 can use, for example, a DA converter, which supplies a digital signal corresponding to a predetermined bias voltage from the controller 11 to the DA converter, converts this digital signal into a DA converter, and converts the analog voltage into an analog voltage. It can be configured to be applied to the frequency converter 2 as a bias voltage.

The controller 11 can be, for example, a microcomputer, and in the receiving sensitivity setting mode, it gives a sweep command to the sweep voltage generator 4 to generate, for example, a triangular wave-shaped sweep voltage as shown in FIG. 2A.

The oscillation frequency of the local oscillator 3 is swept by this triangular waveform sweep voltage. The controller 11 changes the bias voltage to V ₁ , V ₂ , V ₃ , and V ₄ as shown in FIG. 2B each time the local oscillator 3 is pulled out. The values of this bias voltage V ₁ , V ₂ ,
It is assumed that V ₃ and V ₄ are determined in advance as optimal bias values based on the characteristics of the frequency converter 2 and local oscillator 3. For example, the bias voltage V ₁ is the optimum bias voltage value for the fundamental wave of the local oscillator 3, V ₂ is the optimum bias voltage value for the first, third, seventh, and ninth harmonics of the local oscillator 3, and V ₃ is the optimum bias voltage value for the local oscillator 3.
The optimum bias voltage values for the second, fourth, sixth and eighth harmonics, _V4 , are determined in advance as the optimum bias values for the fifth harmonic of the local oscillator 3,
The voltage value is stored in a memory within the controller 11.

First sweep period for frequency sweeping the local oscillator 3
At T ₁ , the stored value corresponding to the bias voltage value V ₁ is read out and the digital value is given to the bias voltage supply circuit 5 . The bias voltage supply circuit 5 converts this digital value into an analog voltage V ₁ and supplies it to the frequency converter 2 as a bias voltage.

Similarly, in the second sweep period T ₂ , the bias voltage
The digital value corresponding to V ₂ is read out and applied to the bias voltage supply circuit 5 to generate the bias voltage V ₂ . Also, in the third sweep period _T3 , the bias voltage
The digital value corresponding to V ₃ is read out and applied to the bias voltage supply circuit 5 to generate the bias voltage V ₃ . In the fourth sweep period _T4 , a bias voltage _V4 is generated.

On the other hand, 12 indicates maximum level detection means. This maximum level detection means 12 is for detecting the maximum value of the intermediate frequency signal, and is composed of a wave detector 12A.
, a peak hold circuit 12B that peak-holds the detected output signal of the detector 12A, and a voltage comparator 12C.

The intermediate frequency signal output to the output terminal 8 is applied to the detector 12A, and amplitude detection is performed on the intermediate frequency signal.
The detection output of the detector 12A is peak hold circuit 1.
2B and one input terminal of the voltage comparator 12C. The hold output voltage of the peak hold circuit 12B is applied to the other input terminal of the voltage comparator 12C.

In the reception setting mode, the detector 12A detects a signal of unknown frequency input from the input terminal 1.
P ₁ , for each frequency sweep as shown in Figure 2C.
Suppose that P ₂ , P ₃ , and P ₄ are output. This detection output
When P ₁ to P ₄ are input to the peak hold circuit 12B, the hold output voltage of the peak hold circuit 12B becomes the detection output signal P 2 at the time when the maximum detection output signal P ₂ is output, as shown in FIG. _2D . is held at the detected output voltage Vp.

In the process until the voltage Vp is held in the peak hold circuit 12B, the voltage comparator 12C generates a deviation signal every time the detection output signals _P1 and _P2 are applied.
Generate M ₁ and M ₂ . Peak hold circuit 12B
When the peak voltage Vp of the maximum detection output signal _P2 is held, no deviation signal is output from the voltage comparator 12C thereafter. The controller 11 counts the deviation signal output from the voltage comparator 12C, and stores the number of frequency sweeps, that is, the frequency sweep period _T2 at which the maximum detected output signal is obtained.

In this way, the controller 11 can know at which frequency sweep the intermediate frequency signal of the maximum level was obtained, and can detect the value of the bias voltage for obtaining the intermediate frequency signal of the maximum level.

Therefore, the controller 11 executes a predetermined number of frequency sweeps based on this detection data, and then supplies the bias voltage supply circuit 5 with a digital value corresponding to the optimum bias voltage _V2 corresponding to _T2 , for example, to supply the bias voltage. The optimum bias voltage V ₂ is outputted from the circuit 5, and this bias voltage V ₂ is applied to the frequency converter 2.

The sensitivity setting mode is ended with the optimum bias applied to the frequency converter 2, and the process moves to the reception mode. When shifting to the reception mode, the controller 11 gives a reset signal to the peak hold circuit 12B to hold the peak hold circuit 12B in the reset state. At the same time, the controller 11 gives a sweep start command to the sweep voltage generator 4, causes the local oscillator 3 to sweep the frequency again, and the reception state is set. When the intermediate frequency signal is output from the amplifier 7 during frequency sweeping, the detector 12A
A detection output _P5 is output from. Based on this detection output, a deviation signal M ₃ is output from the voltage comparator 12C, and this deviation signal M ₈ is provided to the controller 11.
When a frequency counter is connected after the output terminal 8, the controller 11 stops the sweep of the sweep voltage signal output from the sweep voltage generator 4 when the deviation signal _M3 is input, and maintains this state. Therefore, the frequency converter 2 is maintained in a state of converting an input signal of unknown frequency applied to the input terminal 1 into an intermediate frequency signal, and an intermediate frequency signal having the highest level can be obtained from the output terminal 8.

As another example, in the case of a spectrum analyzer, the local oscillator may be maintained in a frequency sweep state with the optimum bias voltage set, and frequency analysis etc. may be performed. FIG. 3 shows a flowchart for explaining the outline of a program for operating the controller 11.

"Operations and Effects of the Invention" As explained above, according to the present invention, even if a signal of an unknown frequency is applied to the input terminal 1, the bias voltage that has the highest sensitivity to that input signal is detected and automatically detected. The bias voltage can be set to be applied to the frequency converter. Therefore, there is no need to perform any adjustment work to bring the reception sensitivity to the best condition.

Therefore, with the receiver according to the present invention, it is possible to always obtain the best reception condition, so when measuring the frequency or frequency spectrum of the received signal, the measurement accuracy can be improved and highly reliable measurement can be achieved. It can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining one embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of this invention, and FIG. 3 is a microcontroller constituting a controller used in this invention. FIG. 4 is a flowchart for explaining the outline of a program stored in a computer, and a block diagram for explaining a conventional wideband receiver. DESCRIPTION OF SYMBOLS 1...Input terminal, 2...Frequency converter, 3...Local oscillator, 4...Sweep voltage generator, 5...Bias voltage generator, 6...Band pass filter, 7...Amplifier, 8...
Output terminal, 11... Controller, 12... Maximum value detection means, 12A... Detector, 12B... Peak hold circuit, 12C... Voltage comparator.

Claims (1)

[Claims] 1. A local oscillator constituted by a voltage controlled oscillator, B. A sweep voltage generator that sweeps the oscillation frequency of this local oscillator, and C. Frequency mixing of the oscillation signal of the local oscillator and the input signal. (D) a bias voltage supply circuit that provides a bias voltage for adjusting reception sensitivity to this frequency converter; and (E) a frequency converter that provides a bias voltage for adjusting reception sensitivity to this frequency converter; a controller that changes the bias voltage applied to the device; G) means for causing the bias voltage supply circuit to output a bias voltage in a state in which the maximum level detection means detects the maximum level of the intermediate frequency signal.