JP5883285B2 - Radar receiver and radar apparatus - Google Patents

Description

  The present invention relates to a configuration of a receiver for detecting a signal received by an antenna in a radar apparatus.

  The radar apparatus is configured to transmit a microwave signal output from a magnetron from an antenna, and to receive a signal reflected by a target or the like by the antenna and detect the position or the like of the target. Here, the intensity of the signal reflected at a position close to the antenna is extremely strong, and the intensity of the signal reflected at a position far from the antenna is extremely weak. Therefore, in order to enable the radar apparatus to detect a wide range of targets including the vicinity of the antenna, it is required that the receiver has a very wide dynamic range for detecting the received signal.

  However, the dynamic range of an amplifier or the like for amplifying a signal has a limit, and when a signal exceeding the limit is input, the output is saturated. For this reason, the conventional receiver having only one line for detecting a signal has a limit in expanding the dynamic range.

  In order to solve this problem, Patent Document 1 divides the received signal strength into a main line that hardly attenuates the signal and a sub-line that attenuates the signal. The structure which synthesize | combines is disclosed. Japanese Patent Laid-Open No. 2004-228561 states that by distributing signals in this way, signal processing according to the level of the received signal is possible, and a wide dynamic range can be realized. Patent Document 2 also discloses a similar configuration.

  In such a radar receiver, there is a possibility that an excessive signal flows into the receiving system and the amplifier and the like of the receiving system are destroyed. As a cause of such an excessive signal flowing into the receiving system, a case where a reflected signal of a large level is received by the radar antenna can be considered. In addition, a powerful microwave signal output from the magnetron leaks directly from the circulator to the receiving system, or the microwave signal is reflected at the mismatched location between the radar antenna and the waveguide and flows into the receiving system. There is also a case.

  Therefore, in order to prevent the reception system from being destroyed by such an excessive signal, a limiter may be provided at the front stage of the reception system. This limiter suppresses and outputs an input signal having a signal level exceeding a predetermined threshold Th, for example, as shown in FIG. Since an excessive input signal can be suppressed by the limiter, it is possible to prevent the reception system from being destroyed by the excessive signal.

Japanese Patent Laid-Open No. 2000-137071 JP 2008-215952 A

  In the radar receiver as described above, the reception system detects the signal that has passed through the limiter. Since the dynamic range of the conventional radar receiver is narrow, a high level signal for operating the limiter cannot be detected linearly because the receiver is saturated. However, by adopting the configurations of Patent Document 1 and Patent Document 2, the dynamic range of the receiving system can be dramatically expanded so that a large level signal at which the limiter operates can be detected linearly. It has become to. However, if a limiter operates when a high-level signal is input, the signal is suppressed and distorted.

  That is, although the receiving system of the radar receiver adopting the configurations of Patent Document 1 and Patent Document 2 has a performance capable of linearly detecting a large level signal, such a large level signal is Since the signal is distorted by the limiter before being input to the receiving system, a linear detection result cannot be obtained after all. As described above, since the signal is distorted by the limiter, the wide dynamic range of the receiving system cannot be fully utilized.

  Therefore, it is conceivable that the threshold of the limiter is set higher with the expansion of the dynamic range of the receiving system. This makes it difficult to distort large level signals. However, if the threshold of the limiter is raised, a strong microwave signal from a magnetron or the like cannot be sufficiently suppressed by the limiter, and a large amount of power enters the receiving system, causing destruction.

  The present invention has been made in view of the above circumstances, and an object thereof is to increase the saturation level of the entire radar receiver without changing the signal suppression amount of the limiter and the setting of leakage power.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

According to an aspect of the present invention, a radar receiver having the following configuration is provided. That is, the radar receiver includes a limiter, a first detection unit, a limiter excess correction unit, and a signal addition unit. The limiter outputs an input signal below a predetermined signal level as an output signal as it is, and outputs an input signal above the predetermined signal level as a suppressed output signal. The first detector detects the output signal of the limiter and outputs a first detection signal. The limiter excess correction unit, when an input signal of a predetermined signal level or higher is input to the limiter, the input signal of the predetermined level from the first detection signal based on the suppressed output signal to the limiter There outputs a correction signal obtained by amplifying the difference signal obtained by subtracting the first detection signal based on the output signal when inputted. The signal adding unit adds the detection result of the first detection unit and the correction signal.

That is, when a signal exceeding the threshold (predetermined signal level) is input to the limiter, a portion of the limiter output signal exceeding the threshold is suppressed. Therefore, as described above, a differential signal that is a portion where the signal level of the input signal exceeds the threshold is extracted from the first detection signal, and a correction signal obtained by amplifying the difference signal is added to the detection result of the first detection unit. As a result, the linearity of the detection result can be improved to some extent . As a result, the dynamic range of the radar receiver can be expanded without changing the setting of the limiter threshold or the like.

  In the radar receiver, the amplification factor in the limiter excess correction unit is set so that a reduction in the signal level of the first detection signal due to the suppression substantially matches the signal level of the correction signal. It is preferable that

  As a result, the first detection signal whose signal level has decreased due to the suppression of the limiter can be appropriately corrected with the correction signal.

  The radar receiver is preferably configured as follows. That is, the radar receiver includes an attenuator that attenuates the output signal of the limiter and outputs the attenuated signal to the first detector, and a second detector that detects the output signal of the limiter and outputs a second detected signal. In addition. The first detection unit outputs a first detection signal obtained by detecting the attenuated output signal of the limiter.

  In this way, by providing separately the second detection unit for detecting without attenuating the signal and the first detection unit for detecting by attenuating the signal, the conventional detection unit that has detected by one system of detection unit is provided. The dynamic range can be expanded compared to the receiver.

The radar receiver preferably has the following configuration. That is, when the signal level of the output signal of the limiter input to the second detection unit is equal to or higher than the first signal level, the second detection unit outputs the second detection signal having a constant signal level. The signal level of the first detection signal when the output signal of the limiter whose signal level is the first signal level is input to the first detection unit is set as the second signal level. The radar receiver outputs a processed first detection signal obtained by extracting a portion having a signal level equal to or higher than the second signal level from the attenuated first detection signal as a detection result of the first detection unit. A waveform processing unit is further provided. The signal adding unit further adds the second detection signal to the detection result of the first detection unit and the correction signal.

As described above , by adding the detection result of the first detection unit , the second detection signal, and the correction signal, it is possible to obtain a detection result having a wide dynamic range and correcting distortion caused by the limiter. .

  According to still another aspect of the present invention, the radar receiver includes: a radar antenna that outputs a received high-frequency signal to the radar receiver; and an oscillator that applies a high-frequency signal to the radar antenna. A radar device is provided.

  This radar apparatus can correct the distortion of the detection signal caused by the limiter while preventing each component of the radar receiver from being destroyed by the strong signal from the oscillator.

1 is a block diagram showing a configuration of a radar apparatus according to an embodiment of the present invention. The graph which shows the relationship between the input signal and output signal of a limiter. The graph which shows the relationship between an input signal and the 2nd detection signal which a 2nd detection part outputs. The graph which shows the relationship between an input signal and the 1st detection signal which a 1st detection part outputs. The graph which shows typically the process in a waveform process part. The graph of the detection signal which added the processed 1st detection signal and the 2nd detection signal. The graph which shows typically the process in a limiter excess correction | amendment part. The graph of the detection signal after correction | amendment which correct | amended the distortion by a limiter.

  Next, embodiments of the present invention will be described with reference to the drawings. The radar device 1 of this embodiment is a marine radar device mounted on a ship, and includes a radar antenna 2, a radar receiver 3, a display device 4, and an oscillator 5, as shown in FIG. .

  The radar antenna 2 is connected to the oscillator 5 and the radar receiver 3 via the circulator 6. As is well known, the radar antenna 2 is configured to be rotated 360 ° in a horizontal plane with a predetermined rotation period.

  The oscillator (specifically magnetron) 5 is configured to apply a high-frequency pulse signal to the radar antenna 2 at a predetermined period. Thereby, a high frequency signal is transmitted from the rotating radar antenna 2 at a predetermined cycle. The high frequency signal transmitted from the radar antenna 2 is reflected by a surrounding target or the like and received by the radar antenna 2. The received high frequency signal is input to the receiver 3.

  The radar receiver 3 includes a limiter 10, frequency conversion units 11 and 12, and detection units 13 and 14.

The high-frequency signal input from the radar antenna 2 to the radar receiver 3 is first passed through the limiter 10. The limiter 10 is configured so that each component of the receiver 3 is an excessive signal when a high level signal is received by the radar antenna 2 or when a strong high-frequency signal output from the oscillator 5 flows into the receiver 3. It is provided to protect from. The signal level [dBm] of the input signal Lim _in to this limiter 10, output signal Lim _out signal level [dBm] from the limiter 10, the relationship is illustrated in Figure 2.

As shown in FIG. 2, the limiter 10 includes an input signal Lim _in signal level below a predetermined signal level (threshold Th) is output as it is. That is, when Lim _in <Th, Lim _out [dBm] = Lim _in [dBm]. In this case, it can be said that the limiter 10 is not operating.

On the other hand, when the signal level of the input signal Lim _in respect limiter 10 exceeds the threshold Th, the suppression of the signal the limiter 10 is operated (compressed) begins. That is, ΔThim _out [dB] = (1 / X) ΔLim _in [dB] when Th ≦ Lim _in . It should be noted, ΔLim _out is, increase the amount of Lim _out from the threshold Th, ΔLim _in is the increased amount of Lim _in from the threshold Th. X is a suppression rate of the limiter 10 and takes a value of 1 or more. When an excessive signal is input to the radar receiver 3 by the limiter 10, the signal level of the signal can be suppressed and output. Therefore, a configuration subsequent to the limiter 10 can be configured from an excessive signal. Can be protected.

  The high-frequency signal that has passed through the limiter 10 as described above is converted to an intermediate frequency by the frequency converters 11 and 12 and detected by the detectors 13 and 14. The detection result of the high frequency signal is output to the display device 4.

  The display device 4 includes a signal processing unit 15 and a color liquid crystal display 16. The signal processing unit 15 is configured to generate a radar image by performing appropriate filtering / threshold processing on the signal from the radar receiver 3. The liquid crystal display 16 is configured to display a radar image generated by the signal processing unit 15.

  Next, the configuration of the radar receiver 3 will be described.

  As shown in FIG. 1, the radar receiver 3 of the present embodiment includes two systems of detectors (a first detector 14 and a second detector 13). Then, the first detection unit 14 and the second detection unit 13 perform detection separately, and then the detection results of both are added by the signal addition unit 17 and output. This configuration is described in, for example, Patent Document 1 and Patent Document 2, and will be described in detail below.

The radar receiver 3 of this embodiment has a signal branching unit 18 that branches the output signal Lim _out of the limiter 10 into two lines. Here, of the two lines branched by the signal branching unit 18, the line where the first detection unit 14 is arranged (the lower line in FIG. 1) is the first line, and the second detection unit 13 is arranged. The line (the upper line in FIG. 1) is called the second line.

First, the second line where the second detector 13 is arranged will be described. In the second line, the output signal Lim _out from the limiter 10 is amplified by the low noise amplifier 19 and then input to the second frequency converter 11.

The second frequency conversion unit 11 includes a mixer 21 and a low-pass filter 22. The output signal Lim _out amplified by the low noise amplifier 19 is mixed with the local oscillator signal output from the local oscillator 20 in the mixer 21, and then the image frequency signal is removed by the low-pass filter 22, whereby the intermediate frequency signal Down converted. This intermediate frequency signal is input to the second detector 13. The low pass filter 22 may be omitted.

The second detector 13 includes a second amplifier 23 and a second logarithmic detector 24. The intermediate frequency signal from the second frequency converter 11 is appropriately amplified by the second amplifier 23 and then input to the second logarithmic detector 24. The second logarithmic detector 24 performs logarithmic detection on the input signal and outputs a second detection signal Det2. The signal level [dBm] of the input signal Lim _in, the relationship between the second detection signal Det2 [V], shown in Figure 3

The second detection unit 13, since the detection of the signal amplified by the low noise amplifier 19, even when the input signal Lim _in signal level is very weak, and it is possible to accurate detection.

On the other hand, as can be seen from Figure 3, when the signal level of the input signal Lim _in the above Amp _sat, the second detection signal Det2 becomes constant. This is because when the signal level of the input signal Lim _in becomes more Amp _sat, the output of the second amplifier 23 is because is saturated. Therefore, the upper limit Amp _sat input signal Lim _in that the second detection unit 13 can detected linearly, referred to as the saturation input level of the second detection unit 13 (first signal level). Thus, the input signal Lim _in the second detection unit 13 can detects linearly the signal level of the input signal Lim _in is limited in the case of less than the saturation input level Amp _sat.

As described above, the second detection unit 13, when the signal level of the input signal Lim _in small, and is configured to allow the accurate detection.

The threshold Th of the limiter 10 is set to be higher than the saturation input level Amp _sat of the second detector 13. Therefore, beyond the signal level threshold Th of the input signal Lim _in, even been distorted signal in the limiter 10, for signal such a large level that is saturated in the second detection unit 13, the The distorted signal does not affect the output of the second detector 13.

Next, the first line where the first detection unit 14 is arranged will be described. In the first line, the output signal Lim _out from the limiter 10 is attenuated by the attenuator 25 and then input to the first frequency converter 12.

  The first frequency conversion unit 12 includes a mixer 26 and a low-pass filter 27. The output signal from the attenuator 25 is mixed with the local oscillator signal output from the local oscillator 20 in the mixer 26 and then down-converted to an intermediate frequency signal by removing the image frequency signal by the low-pass filter 27. . This intermediate frequency signal is input to the first detector 14. Note that the low-pass filter 27 may be omitted.

The first detector 14 includes a first amplifier 28 and a first logarithmic detector 29. The intermediate frequency signal from the first frequency converter 12 is appropriately amplified by the first amplifier 28 and then input to the first logarithmic detector 29. The first logarithmic detector 29 performs logarithmic detection on the input signal and outputs a first detection signal Det1. The signal level [dBm] of the input signal Lim _in, the relationship between the first detection signal Det1 [V], shown in Figure 4.

As described above, the first detector 14 performs detection after the input signal Limin is attenuated _in advance by the attenuator 25. Thus, the signal level of the input signal Lim _in even if very large, there is no possibility that the output of the first amplifier 28 is saturated. Therefore, the first detection unit 14 can perform linear detection even with a high level signal that would be saturated in the second detection unit 13.

On the other hand, as can be seen from Figure 4, when the signal level of the input signal Lim _in is small, the first detection signal Det1 is constant, or will become almost zero. This is because in the first line are attenuated by the attenuator 25 to the input signal Lim _in, when the signal level of the input signal Lim _in is weak is can not be detected by the first detection unit 14. Thus, it can be detected input signal Lim _in linearly in the first detection unit 14, only when the signal level of the input signal Lim _in about some large.

As described above, the first detection unit 14 is linear detection is configured to allow when the signal level of the input signal Lim _in is large.

  The radar receiver 3 of this embodiment includes a signal adding unit 17 that adds the detection result on the first line and the detection result on the second line. That is, a large level signal can be detected linearly on the first line, and a weak signal can be detected with high precision on the second line. By combining both detection results, a large level can be detected from the weak signal. As a result, it is possible to obtain a result obtained by accurately detecting up to the above signal with a wide dynamic range.

However, even if the first detection signal Det1 and the second detection signal Det2 are added as they are, an appropriate detection result cannot be obtained. Therefore, the radar receiver 3 according to the present embodiment allows the first detection signal Det1 and the second detection signal Det2 to be appropriately added according to the saturation input level Amp _sat of the second detection unit 13 in order to appropriately add the first detection signal Det1 and the second detection signal Det2. A waveform processing unit 30 that performs waveform processing on the signal Det1 is provided.

  The waveform processing unit 30 is configured by combining a subtractor circuit using an operational amplifier and a half-wave rectifier circuit.

First, the waveform processing unit 30 as a subtraction circuit subtracts a predetermined signal level V _ref1 (second signal level) from the first detection signal Det1 (FIG. 5A) (FIG. 5B). The signal level V _ref1 is set to the signal level of the first detection signal Det1 output from the first detection unit 14 when Lim _in = Amp _sat . Since there is an individual difference in the second amplifier 23, the saturation input level Amp _sat is different for each radar receiver. Therefore, the waveform processing unit 30 of this embodiment includes a variable resistor for adjusting the value of V _ref1 subtracted from the first detection signal Det1 in the waveform processing unit 30. Thereby, adjustment according to individual differences is possible.

Subsequently, the waveform processing unit 30 as a half-wave rectifier circuit extracts only a signal with a positive sign from the first detection signal Det1 offset by −V _ref1 as described above (FIG. 5C). ). Thus, among the first detection signal Det1 the first detection unit 14 is output, it is possible to extract only the "signal level is saturated input level Amp _sat or more portions of the input signal Lim _in". The signal extracted in this way is referred to as a processed first detection signal Det1 ′. The waveform processing unit 30 outputs the processed first detection signal Det1 ′ to the signal adding unit 17.

That is, the second detection signal Det2, since "the input signal Lim _in the signal level of a portion below the saturation input level Amp _sat" is a signal obtained by detecting only, "the input signal Lim _in signal level is saturated input level Amp _sat in By adding the first detection signal Det1 ′ from which only “the above part” is extracted, the two can be appropriately combined. Here, a signal obtained by adding the processed first detection signal Det1 ′ and the second detection signal Det2 is defined as a detection signal Det. This detection signal Det [V], indicate the signal level [dBm] of the input signal Lim _in, the relationship in FIG.

  In this way, by combining the detection result of the first detection unit 14 and the detection result of the second detection unit 13, compared to the case of only the first detection unit 14 or only the second detection unit 13, A detection signal Det having a wide dynamic range can be obtained.

However, as can be seen from FIG. 6, the signal level of the input signal Lim _in exceeds the threshold Th, the slope of the graph of the detection signal Det is changing. That is, when the input signal Lim _in exceeds the threshold Th, the linearity of the detection signal Det for the input signal Lim _in is impaired. This is because when the signal level of the input signal Lim _in exceeds the threshold Th, because the signal from being suppressed in the limiter 10.

Here, in order to recover the ideal linearity of the detection signal Det, a correction value is applied to the detection signal Det _in the portion of Th ≦ Limin (the portion where the slope of the graph changes) _in the graph of FIG. Add Δ. The correction value Δ can be obtained by amplifying the difference signal ΔDet1 with a predetermined amplification factor. Here, the differential signal ΔDet1 includes a first detection signal Det1 when an input signal Lim _in exceeds the threshold Th, are those taken with a predetermined signal level V _ref2, the difference. This predetermined signal level V _ref2, the signal level of the input signal Lim _in is set to the signal level of the detection signal first detection unit 14 is output when the threshold Th (see Fig. 4). In other words, the difference signal ΔDet1, of the first detection signal Det1, shows a partial linearity is impaired because the input signal Lim _in has exceeded the threshold Th.

  Based on the above points, the radar receiver 3 of the present embodiment includes a limiter excess correction unit 31 for correcting signal distortion caused by the limiter 10. In addition, the radar receiver 3 includes a second signal branching unit 32 that branches the output of the first detection unit 14 into two. Of the two lines branched by the second signal branching unit, the waveform processing unit 30 is arranged on one side, and the limiter excess correction unit 31 is arranged on the other side.

  The limiter excess correction unit 31 is configured by combining a subtractor circuit using an operational amplifier and a half-wave rectifier circuit.

First, the limiter excess correction unit 31 as a subtraction circuit subtracts a predetermined signal level V _ref2 from the first detection signal Det1 (FIG. 7A) output from the first detection unit 14 (FIG. 7B). ). The signal level V _ref2 is set to the signal level of the first detection signal Det1 output from the first detection unit 14 when Lim _in = Th. Since the limiter 10 has individual differences, the threshold Th differs for each radar receiver. Therefore, the limiter excess correction unit 31 of the present embodiment includes a variable resistor for adjusting the value of V _ref2 subtracted from the first detection signal Det1 in the limiter excess correction unit 31. Thereby, adjustment according to individual differences is possible.

The limiter excess correction unit 31 as a half-wave rectifier circuit extracts only a signal with a positive sign from the first detection signal Det1 offset by −V _ref2 as described above (FIG. 7C). This makes it possible to take out the "first detection signal Det1 when an input signal Lim _in the limiter 10 is suppressed, and the signal level V _ref2 of the detection signal corresponding to the threshold Th, the differential signal ΔDet1 of".

  Further, the limiter excess correction unit 31 amplifies the difference signal ΔDet1 extracted as described above at a predetermined amplification factor B to generate a correction signal Δ (FIG. 5D).

  Although this amplification factor B may be an arbitrary value, the signal level of the correction signal Δ obtained by amplification coincides with the decrease in the signal level of the first detection signal Det1 due to the suppression of the limiter 10 (limiter suppression component). It is preferable if it is set.

Such an amplification factor B can be a value obtained by subtracting 1 from the suppression rate of the limiter 10, for example. That is, as described above, when the signal level of the input signal Lim _in is less than the threshold Th of the limiter 10, the input signal Lim _in the output signal Lim _out of the limiter 10 is 1: 1 relationship, Lim _out [dBm ] = Lim _in [dBm]. However, the signal level of the input signal Lim _in exceeds the threshold Th, collapses input-output relationship of the limiter 10 the limiter 10 is operated, the _{ΔLim out [dB] = (1} / X) ΔLim in [dB] ( X is the limiter suppression rate).

Since the first detection unit 14 performs logarithmic detection, when the limiter 10 is not operating (when the signal level of the input signal Lim _in is less than the threshold Th) is
Det1 [V] = A × Lim _out [dBm] = A × Lim _in [dBm] (1)
(A is a constant [V / dB]). Therefore, _in the region where the signal level of the input signal Limin is less than the threshold Th, the slope of the graph of FIG.

However, when the limiter 10 starts to operate, ΔLim _out [dB] = (1 / X) ΔLim _in [dB]. As a result, as shown in FIG. 6, the slope of the graph of the detection signal Det is A / X. . That is, _in a region where the signal level of the input signal Limin is equal to or higher than the threshold Th,
ΔDet1 [V] = A × ΔLim _out [dB] = (A / X) × ΔLim _in [dB] (2)
It becomes.

On the other hand, without causing distortion due to the limiter 10, when the signal level of the input signal Lim _in is assumed that consists ideal linearity even detection result in the region beyond the threshold Th,
ΔDet1 [V] = A × ΔLim _in [dBm] (3)
Holds.

Here, by subtracting the equation (2) from the equation (3), a decrease in the signal level of the detection signal Det due to the influence of the suppression of the limiter 10 (limiter suppression component Δ) can be obtained.
Δ = A × ΔLim _in − (A / X) × ΔLim _in
= (X-1) {(A / X) × ΔLim _in } (4)
Here, {(A / X) × ΔLim _in } in the formula (3) is the right side of the formula (2) itself. Therefore, Equation (4) can be rewritten as follows.
Δ = (X−1) ΔDet1 (5)
That is, the limiter suppression component Δ can be obtained by multiplying the difference signal ΔDet1 by (X−1).

  Therefore, in this embodiment, the amplification factor B in the limiter excess correction unit 31 is set to a value (X−1) obtained by subtracting 1 from the suppression rate of the limiter 10. As a result, the correction signal Δ obtained by amplifying the difference signal ΔDet1 with the amplification factor B in the limiter excess correction unit 31 can be made to coincide with the decrease in the signal level of the detection signal Det due to the suppression effect of the limiter 10. . The limiter excess correction unit 31 outputs the correction signal Δ to the signal addition unit 17.

Then, the signal adding unit 17 outputs a corrected detection signal Det ′ obtained by adding the correction signal Δ obtained as described above, the processed first detection signal Det1 ′, and the second detection signal Det2. It is configured. Such a corrected after detection signals Det' obtained [V] in the relationship between the signal level [dBm] of the input signal Lim _in, shown in Figure 8.

As described above, the correction signal Δ matches the decrease in the signal level of the detection signal Det due to the suppression effect of the limiter 10 (limiter suppression component Δ), so the correction signal Δ is added to the detection signal Det. Thus, the signal level of the detection signal suppressed by the limiter 10 can be restored. That is, as apparent from a comparison between FIG. 8 and FIG. 6, by adding the correction signal Δ to the detection signal Det, the graph becomes linear and the signal that has been suppressed by the limiter 10 can be corrected. it can. Thus, the linearity of the case where the signal level of the input signal Lim _in exceeds the threshold Th, can be greatly improved.

As described above, the radar receiver 3 according to the present embodiment includes the limiter 10, the first detection unit 14, the limiter excess correction unit 31, and the signal addition unit 17. Limiter 10, together with the input signal Lim _in signal levels below the threshold Th is output as it is, the input signal Lim _in the threshold Th or more signal level and outputs the suppression. The first detector 14 detects the output signal of the limiter 10 and outputs a first detection signal Det1. Limiter excess correction unit 31 includes a first detection signal Det1 the first detection unit 14 is output when the input signal is suppressed by the limiter 10, the detection signal when the input signal is input Lim _in signal level threshold Th A correction signal Δ obtained by amplifying the difference signal ΔDet1 between V _ref2 and a predetermined amplification factor is output. The signal adder 17 adds the detection result Det1 ′ of the first detector 14 and the correction signal Δ and outputs the result.

Thus, one of the first detection signal Det1, takes out a differential signal ΔDet1 signal level of the input signal Lim _in is part that exceeds the threshold Th, the detection of the first detection unit a correction signal Δ that amplifies the By adding to the result, the linearity of the detection result can be improved. Thereby, the dynamic range of the radar receiver 3 can be expanded without changing the setting of the threshold of the limiter 10 or the like.

  In this type of radar apparatus, the performance of the limiter 10 depends on the electrical length between the limiter 10 and the electrical components downstream of the limiter 10 (in this embodiment, the low-noise amplifier 19 and the attenuator 25). Is known to change. This is because a standing wave is generated between the limiter 10 and the electrical component when the leakage power from the limiter 10 is reflected back from the subsequent electrical component, thereby affecting the performance of the limiter 10. To give. In other words, the performance of the limiter 10 can be optimized by adjusting the electrical length between the limiter 10 and an electrical component subsequent to the limiter 10.

Therefore, in this embodiment, as the suppression ratio of the limiter 10 in the region where the input signal Lim _in exceeds the threshold Th is constant as possible, with the limiter 10, between the rear stage of the electrical components of the limiter The electrical length is optimized. Thereby, since the suppression rate by the limiter 10 can be regarded as constant, the limiter excess correction unit that generates the correction signal for correcting the signal suppressed by the limiter 10 can be configured with a simple circuit.

  Although a preferred embodiment of the present invention has been described above, the above configuration can also be configured as follows.

  The configuration of the present invention can be applied not only to a marine radar device but also to various radar devices.

  In the above-described embodiment, a process of correcting distortion by the limiter 10 is performed on the detection signal output by detecting the output signal of the limiter 10 by the first detection unit 14. However, the present invention is not limited to this, and processing for correcting distortion by the limiter 10 may be performed on the output signal of the limiter 10 (signal before detection).

  In the embodiment described above, the output of the limiter 10 is branched into two, and two detection units are provided. However, the present invention is not limited to this, and only one detection unit may be used. Even in this case, when the saturation level of the detection unit is set higher than the threshold Th of the limiter 10, the effect of the present invention of restoring the linearity by returning the signal suppressed by the limiter 10 to the original state. It can be demonstrated.

  However, the output of the limiter 10 may be branched into three or more, and three or more detection units may be provided.

  The method of determining the amplification factor B in the limiter excess correction unit 31 is not limited to the above. Further, the amplification factor B may be an arbitrary value. That is, the correction signal output from the limiter excess correction unit 31 does not have to coincide with the decrease in the signal level (limiter suppression component) of the first detection signal Det1 due to the influence of suppression of the limiter 10. This is because even if the correction signal does not completely match the limiter suppression component, the linearity can be improved to some extent by adding the correction signal to the detection signal.

  In the above embodiment, the output signal from the limiter 10 is converted into an intermediate frequency signal. However, the detection may be performed while the high frequency signal is maintained.

DESCRIPTION OF SYMBOLS 1 Radar apparatus 2 Radar antenna 3 Radar receiver 5 Oscillator 10 Limiter 13 2nd detection part 14 1st detection part 17 Signal addition part 31 Limiter excess correction part

Claims (5)

An input signal that is less than a predetermined signal level is output as it is as an output signal, and an input signal that is equal to or higher than the predetermined signal level is a limiter that outputs a suppressed output signal;
A first detector for detecting the output signal of the limiter and outputting a first detection signal;
When an input signal of a predetermined signal level or higher is input to the limiter, an output when the input signal of the predetermined level is input to the limiter from the first detection signal based on the suppressed output signal a limiter excess correction unit for outputting a correction signal obtained by amplifying the difference signal obtained by subtracting the first detection signal based on the signal,
A signal addition unit for adding the detection result of the first detection unit and the correction signal;
A radar receiver comprising: The radar receiver according to claim 1,
Wherein said a decrease amount of the signal level of the first detection signal by the suppression, the signal level of the correction signal, but so as to be substantially coincident, that the amplification factor that put the limiter excess correction unit is configured Radar receiver. The radar receiver according to claim 1 or 2,
An attenuator for attenuating the output signal of the limiter and outputting it to the first detector;
A second detector for detecting the output signal of the limiter and outputting a second detection signal;
The radar receiver according to claim 1, wherein the first detector outputs a first detection signal obtained by detecting the attenuated output signal of the limiter. A radar receiver according to claim 3,
When the signal level of the output signal of the limiter input to the second detection unit is equal to or higher than the first signal level, the second detection unit outputs the second detection signal having a constant signal level,
The signal level of the first detection signal when the output signal of the limiter having a signal level of the first signal level is input to the first detection unit is set as a second signal level;
A waveform processing unit that outputs a processed first detection signal obtained by extracting a portion having a signal level equal to or higher than the second signal level from the attenuated first detection signal as a detection result of the first detection unit; Prepared,
The radar receiver according to claim 1 , wherein the signal addition unit further adds the second detection signal to the detection result of the first detection unit and the correction signal . A radar receiver according to any one of claims 1 to 4 ;
A radar antenna that outputs the received high-frequency signal to the radar receiver;
An oscillator for applying a high-frequency signal to the radar antenna;
A radar apparatus comprising:

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