JP3175032B2 - Broadband frequency discriminator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency discriminator for obtaining the frequency of a transmission wave or a reception wave of a broadband transceiver used for a radar device or the like.

[0002]

2. Description of the Related Art FIG. 5 shows a configuration example of a conventional frequency discriminator using a phase detector. 20 is an amplitude limiting amplifier, 21a
Is a power divider, 3 and 4 are transmission lines having lengths L1 and Ls, 22 is a broadband phase detector having input ports 1 and 2 and output ports I and Q, 23 is a 90-degree hybrid, 24a and 24b Is a mixer, and 25a and 25b are low-pass filters. In FIG. 5, portions denoted by the same reference numerals as those in FIG. 1 indicate the same or corresponding portions (hereinafter, the same applies to other drawings).

[0003] In the configuration diagram of FIG.
When a high-frequency signal of power Po and frequency F is input to 0, the signal is amplified and limited to amplitude Ar and output to the power distributor 21a.

The power splitter 21a splits the signal equally, and one of the splitters passes through a transmission line 3 having a length L1.
And the other is also output to port 2 of phase detector 22 via transmission line 4 of length Ls .

The phase detector 22 is a 90 degree hybrid 2
3, the mixers 24a and 24b, and the low-pass filters 25a and 25b. The signals input to the ports 1 and 2 are divided by the power distributor 21b and the 90-degree hybrid 23, and the output is divided by the mixer 24.
a and 24b. In the mixers 24a and 24b, scalar products of the respective signals are obtained, and voltages Vc1 and Vs1 expressed by the following equations are generated at respective output terminals.

Vc1 = Kr · {COSδ−COS (2ωt + δ)} (10a) Vs1 = Kr · {SINδ + SIN (2ωt + δ)} (10b) where δ = 2π · F · (L1-Ls ) / V, (10c) V is the propagation speed of the high-frequency signal and is constant at Kr = Ar / 4.

The low-pass filters 25a and 25b remove the high-frequency component of the second term in {} of the above equations (10a) and (10b), and apply cosine and cosine to the I and Q ports of the phase detector 22. The following voltages Vc and Vs indicating the sine components are output.

Vc = Kr · COS δ (11a) Vs = Kr · SIN δ (11b) To obtain the frequency F, δ is obtained from the equation (11a) or (11b), and the frequency is obtained from the relation of the equation (10c). Find F. Therefore, when the amplitude limiting amplifier 20 is omitted, Kr is not constant with respect to the fluctuation of the input power Po, so that it is difficult to obtain the frequency F only by δ.

In the above-mentioned conventional frequency discriminator, an amplitude limiting amplifier 20 for keeping the amplitude of the input high-frequency signal constant is required. It is necessary for the phase detector 22 to maintain the electrical characteristics of amplitude and phase over a wide frequency band.

[0010]

However, in the above-mentioned conventional frequency discriminator, in order to widen the frequency characteristics, the amplitude / amplitude of an amplitude-limiting amplifier or a phase detector is used.
There are considerable difficulties in component and circuit design to maintain both phase electrical properties constant over a wide frequency range. In order to avoid this, there is also a method in which a circuit is divided into a plurality of bands and configured as a wide band in terms of a circuit configuration. However, since the number of components increases, the structure becomes complicated and the size of the device becomes large.
In addition, there is a drawback that power consumption increases because the number of amplitude limiting amplifiers and phase detectors increases.

The present invention has been made in view of the above points, and in order to eliminate the above-mentioned drawbacks, instead of an amplitude limiting amplifier and a phase detector, a detector having a wide band characteristic, a low-pass filter, and a logarithmic amplifier are used. Using two logarithmic detection amplifiers, subtracting the signals detected and amplified by each logarithmic detection amplifier with a subtractor to remove the influence of the amplitude fluctuation of the input signal, and performing antilogarithmic conversion with an antilogarithmic converter to change the frequency It is an object of the present invention to provide a broadband frequency discriminator that measures the linearity of a signal output voltage, has a simple structure, and easily obtains the frequency of a transmission wave or a reception wave.

[0012]

In the above-mentioned conventional frequency discriminator, since a high-frequency signal needs to be input to the phase detector in principle with a constant amplitude, an amplitude-limiting amplifier or other circuits must be used. It was necessary to keep the amplitude of the high-frequency signal input to the phase detector constant.

According to the present invention, a wideband frequency discriminator is configured without using an amplitude limiting amplifier and a phase detector, which have been conventionally required. In order to solve the above problem, the configuration of the frequency discriminator is as follows. I made it.

(1) In addition to the power divider of the divider ko and the two transmission lines, a power combiner with a combining ratio k1 is provided, and a logarithmic detector comprising a detector / low-pass filter having a wide band characteristic and a logarithmic amplifier is provided. Two amplifiers are installed, and a subtractor for subtracting each signal detected and amplified by the logarithmic detection amplifier is provided to cancel the amplitude fluctuation of the input high-frequency signal, and the signal of the subtraction result is subjected to inverse logarithmic conversion to obtain the output frequency. An antilogarithmic converter for obtaining the linearity of the signal voltage was installed to constitute a wideband frequency discriminator.

(2) In the wideband frequency discriminator having the configuration of the above (1), the value of the distribution ratio of the power divider for eliminating the aliasing of the frequency signal voltage and the value of the combination ratio of the power combiner can be selectively performed. As described above, an attenuator is provided on any one of the two transmission lines so that a stable output can be obtained.

[0016]

With the above construction, the logarithmic detection amplifier has a wideband characteristic by using a wideband detector, and the detected received signal is logarithmically amplified after passing through a low-pass filter. Amplifies the detected reference signal with a logarithmic amplifier, subtracts both signals to cancel the amplitude fluctuation of the input high-frequency signal, and obtains the linearity of the output frequency signal voltage by performing inverse logarithmic conversion. so,
Unlike a conventional frequency discriminator, it does not require a high frequency limiting amplifier or a phase detector having a wide band characteristic. Further, an attenuator is provided on any one of the two transmission lines for removing the aliasing of the frequency signal voltage, so that the value of the distribution ratio of the power divider to be used and the value of the combination ratio of the power combiner can be selected selectively. Thus, a wide-band frequency discriminator that is not affected by the amplitude fluctuation of the input high-frequency signal can be easily configured with a simple structure.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a wideband frequency discriminator according to a first embodiment of the present invention.

In FIG. 1, reference numerals 1a and 1b denote power dividers having a distribution ratio Ko for distributing high-frequency signals, 3 denotes a transmission line having a length L1 for transmitting the distributed high-frequency signals, and 4 denotes distributed high-frequency signals. Is a transmission line having a length Ls, 5 is a power combiner having a combining ratio k1 for combining the transmitted high-frequency signal and the distributed high-frequency signal, and 6a and 6b are for detecting and transmitting the high-frequency signal.
A logarithmic detection amplifier having respective gains G1 and Go for logarithmic amplification (described in detail in FIG. 2), 7 is a subtractor for subtracting the signal amplified by the logarithmic detection amplifier, and 8 is an inverse logarithmic converter for converting the subtracted signal into an antilogarithm Logarithmic converter.

In the above configuration diagram, when a high frequency signal of power Po and frequency F is input to the power divider 1a having the wideband characteristic, the signal is divided by the distribution ratio Ko and the power divider 1b having the wideband characteristic and logarithmic detection. Output to the amplifier 6b. In the logarithmic detection amplifier 6b, the input high-frequency signal is logarithmically detected and amplified, and output to the subtracter 7 as the reference power Ps represented by the equation (1).

Ps = LOG [Po · Ko ² · Go] (1) The other signal output to the power divider 1 b having the wideband characteristic is further divided by the power divider 1 b, and one is divided into the transmission line 3.
Are output to the port 1 of the power combiner 5 having the wideband characteristic via the transmission line 4, and the rest are similarly output to the port 2 of the power combiner 5 via the transmission line 4.

The power combiner 5 combines the signals input to the ports 1 and 2 and outputs the result to the logarithmic detection amplifier 6a.

In the logarithmic detection amplifier 6a, the input high-frequency signal is logarithmically detected and amplified, and output to the subtracter 7 as the reception power Pr shown in the equation (2).

Pr = LOG [Po · Ka ² · (1 + 2 · Kb · COSδ + Kb ² ) · G1] (2) where Ka = (1-Ko) · Ko · (1-K1), Kb = [{(1-Ko). (1-K1)} / {Ko.K1}] ^1/2 . (2b) In the subtractor 7, the reference power Ps of the logarithmic input is the received power Pr.
It is subtracted from, and output to the inverse logarithmic converter 8 as a frequency signal power Pf in (3). Note that the logarithm of the subtractor 7 is
The received power Pr may be subtracted from the input reference power Ps.
No.

Pf = Pr−Ps (3) In the antilogarithmic converter 8, the logarithmic frequency signal power Pf is subjected to antilogarithmic conversion and linearized, and the frequency signal voltage represented by the equation (4) is obtained.
Outputs Vf.

Vf = Kf · (1 + 2 · Kb · COSδ + Kb ² ) (4) Here, Kf = G1 / Go · (Ka / Ko) ² .

In the equation (4), Kf and kb are constants with respect to the change of the frequency F, and only the term of COSδ in () changes. Further, it can be seen that the fluctuation of the amplitude of the input power Po is canceled at the stage of the equation (3) and does not affect the frequency signal voltage Vf of the equation (4).

Therefore, the frequency signal voltage Vf is equal to the input power
Regardless of the fluctuation of the amplitude of Po, the cosine change with respect to the frequency F is shown by the relationship shown in the equation (2).
By obtaining the frequency signal voltage Vf from the equation, the frequency F can be obtained.

The lengths of the transmission lines 3 and 4 may have the relationship shown by the following equation.

L1 + Ls ≦ V · (1 / F1 + 2 / F2) / 2 (5) Here, F1 is a lower limit frequency, and F2 is an upper limit frequency.

According to the equation (4), there is a fold of the frequency signal voltage Vf depending on the selection of Kb. To eliminate this, the term () in the equation (4) is set to be larger than zero. What is necessary is just to select the constant Kb. Therefore, the relationship between the distribution ratio Ko of the power distributors 1a and 1b and the combination ratio K1 of the power combiner 5 may be represented by the following expression using the expression (2b).

K1 / (1-K1) ≦ (1-Ko) / Ko (6) FIG. 2 is a block diagram showing a configuration example of the logarithmic detection amplifiers 6a and 6b according to the embodiment of FIG.

In FIG. 2, reference numeral 9 denotes a detector for detecting a distributed or synthesized high-frequency signal, 10 a low-pass filter, and 11 a logarithmic amplifier for logarithmic amplification of the detected signal.

The signals from the power divider 1a in FIG. 1 or the power combiner 5 are supplied to the logarithmic detection amplifiers 6a and 6b in FIG.
Are detected by the detector 9 having the wideband characteristic, and the low-pass filter 10 removes the high-frequency component of the frequency F of the high-frequency signal, and extracts only the amplitude component. The logarithmic amplifier 11 logarithmically amplifies this amplitude component and generates logarithmic detection amplifiers 6a and 6a.
It is output as an output signal of b.

Therefore, in FIG. 2, only the detector 9 needs the wideband characteristic, and the low-pass filter 1
The frequency characteristics of 0 and the logarithmic amplifier 11 may correspond to the frequency components included in the amplitude components after detection.

FIG. 3 is a block diagram showing the configuration of an embodiment of the wideband frequency discriminator according to the second aspect of the present invention. In FIG. 3, reference numeral 12 denotes an attenuator, and portions denoted by the same reference numerals as those in FIG. Indicates the same or corresponding parts.

FIG. 3 shows a configuration in which the value of the distribution ratio of the power divider and the value of the combination ratio of the power combiner can be selectively selected to eliminate the aliasing of the frequency signal voltage Vf.

In the wideband frequency discriminator of the present invention shown in FIG. 1, in order to eliminate the aliasing of the frequency signal voltage Vf, the constants Ko and Ko are set so that the term () in the equation (4) becomes larger than zero.
Although it was necessary to select K1 according to the relationship of the formula (6), FIG. 3 shows that the relationship of the formula (6) can be equivalently given by the attenuator 12 having the attenuation rate K3. And an attenuator 12 is inserted between the transmission line 3 and the power combiner 5 having the combining ratio K1. In the configuration of FIG. 3, the following relationship may be satisfied.

K1 / (1-K1) ≦ (1-Ko) · K3 / Ko (7) FIG. 4 is a diagram showing an example of the input / output characteristics of the wideband frequency discriminator of the present invention shown in FIG.

FIG. 4 shows the power distributors 1a, 1a and 1b in FIG.
b, the distribution ratio Ko = 0.5, the length L1 of the transmission line 3 = 105 mm, the length Ls of the transmission line 4 = 97 mm, and the composite ratio K1 of the power combiner 5 =
The relationship between the frequency signal voltage Vf (vertical axis) and the frequency F (horizontal axis) was measured as 0.5, and the frequency F was changed from 2 GHz to 18 GHz.

FIG. 4 shows that the frequency discriminator operates over a wide frequency band.

Further, with respect to the fluctuation of the input power Po, the fluctuation of the frequency signal voltage Vf when the fluctuation of the input power Po is changed by 30 dB is within ± 2%. It was confirmed that it became a broadband frequency discriminator.

The power distributors 1a and 1b in FIG.
The power distribution unit may be used as a single unit, the transmission lines 3 and 4 may be of a lumped constant type instead of the distributed constant type, and the logarithmic detection amplifiers 6a and 6b have a video output. May be used.

In FIG. 3, another attenuator may be inserted on the transmission line 4 in addition to the attenuator 12 in order to easily obtain the relationship of the equation (7).

[0045]

As described above, in addition to the power divider having the distribution ratio Ko and two transmission lines as in the present invention, a power combiner having a combination ratio K1 and a wideband detector / low-pass filter and a logarithmic amplifier are provided. Two logarithmic detection amplifiers are provided, and the received signal is detected and logarithmically amplified by this. On the other hand, the reference signal distributed by the power divider is amplified by another logarithmic detection amplifier, and both signals are subtracted by a subtractor. By removing the fluctuation of the amplitude of the input power Po by subtraction, and configuring the frequency discriminator so as to improve the linearity of the frequency signal by performing an inverse logarithmic conversion of the signal resulting from the subtraction by an antilogarithmic converter, A simple structure that does not require a high-frequency limiting amplifier with a wideband characteristic to keep the amplitude of the high-frequency signal constant or a phase detector with a wideband characteristic to obtain the frequency signal voltage, which was necessary for the frequency discriminator. Easy wideband frequency discriminator Excellent effect can be obtained.

Further, 2 which constitutes the frequency discriminator of the present invention
If an attenuator is provided on any one of the transmission lines, there is an advantage that the value of the distribution ratio of the power distributor used and the value of the combination ratio of the power combiner can be selectively selected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a wideband frequency discriminator according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a logarithmic detection amplifier provided in the embodiment of FIG.

FIG. 3 is a block diagram of a configuration showing an embodiment of a wideband frequency discriminator according to a second embodiment of the present invention.

FIG. 4 is a characteristic diagram showing an example of input / output characteristics of the wideband frequency discriminator shown in FIG.

FIG. 5 is a configuration diagram showing a conventional frequency discriminator.

[Explanation of symbols]

 1a, 1b Power divider 3, 4 Transmission line 5 Power combiner 6a, 6b Logarithmic detection amplifier 7 Subtractor 8 Antilogarithmic converter 9 Detector 10 Low-pass filter 11 Logarithmic amplifier 12 Attenuator 20 Amplitude limiting amplifier 21a, 21b Power divider 22 Phase detector 23 90-degree hybrid 24a, 24b Mixer 25a, 25b Low-pass filter

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 23/02 G01R 23/12 H03D 3/06

Claims (3)

(57) [Claims] 1. Two transmission lines of different lengths (3 and 4)
A frequency discriminator for discriminating the frequency (F) of the high-frequency signal by using the difference in the propagation length of the high-frequency signal caused by the first and second distributed high-frequency signals having a distribution ratio Ko Power distributor (1a) for distributing power to
And having the same distribution ratio Ko as the first power divider,
A second power divider (1b) for distributing the distributed high-frequency signal to two further distributed high-frequency signals and inputting the two further distributed high-frequency signals to the two transmission lines
A power combiner (5) having a combining ratio K1 and combining signals output from the two transmission lines; and logarithmically detecting and amplifying an output signal of the power combiner to perform first logarithmic detection. A first logarithmic detection amplifier (6a) that outputs an amplified signal power (Pr); and a logarithmic detection and amplification of the second distributed high-frequency signal, and outputs a logarithmic second detection amplification signal power (Ps). A second logarithmic detection amplifier (6b), subtracting one of the logarithmic first output power and the logarithmic second output power from the other, and outputting the subtraction result as a logarithmic frequency signal power (Pf) A subtractor (7) for performing an inverse logarithmic conversion of the logarithmic frequency signal power and outputting a frequency signal voltage (Vf); and converting the frequency signal voltage (Vf) from the frequency signal voltage (Vf). A broadband frequency discriminator for determining a frequency. 2. A distribution ratio ko of the first and second power dividers and a composite ratio of the power combiner to eliminate aliasing of a frequency signal voltage (Vf) at an output of the antilogarithmic converter. 2. The wideband frequency discriminator according to claim 1, wherein the relationship of K1 is K1 / (1-K1) ≤ (1-Ko) / Ko. 3. An attenuator (1) having an attenuation rate K3 on one of the two transmission lines to remove a turn of the frequency signal voltage (Vf) at the output of the antilogarithmic converter.
2), and the relationship between the distribution ratio Ko of the first and second power distributors, the composite ratio K1 of the power combiner, and the attenuation factor K3 is expressed as K1 / (1-K1) ≦ (1-Ko 2. The broadband frequency discriminator according to claim 1, wherein K3 / Ko.