JPH0431072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" This invention relates to a direction display device used in ships and the like.

"Prior Art" A conventional direction display device connects a low-frequency goniometer to the rotation axis of a high-frequency goniometer for rotating the pointing direction of an antenna and obtaining a high-frequency received signal modulated by the direction component. By applying a low frequency signal (30KHz) to the antenna, two balanced modulation signals with a phase difference of 90° in amplitude are created, which are synchronized with the rotation of the antenna's pointing direction.
Either you can obtain a signal by amplitude modulating these two balanced modulation signals according to the level of the received signal obtained from the high frequency goniometer, or you can modulate the low frequency signal at the received signal level and give it to the low frequency goniometer. A structure that obtains two balanced modulation signals with a phase difference and applies these two amplitude-modulated balanced modulation signals to the X-axis and Y-axis of a cathode ray tube display to display a propeller-shaped image and the direction of arrival of radio waves. are being taken.

``Problems to be Solved by the Invention'' According to the conventional structure, a mechanical structure is required to rotate the low frequency goniometer synchronously with the high frequency goniometer. It is necessary to adjust the electrical phase matching between the high-frequency goniometer and the low-frequency goniometer by mechanical positioning, and this adjustment requires a lot of effort. There are drawbacks such as restrictions on where the low frequency goniometer can be installed.

``Means for Solving the Problems'' This invention has a structure that is relatively small and can generate a balanced modulation signal independently from a high-frequency goniometer by using an electronic circuit configuration. An object of the present invention is to provide a direction display device that can eliminate the trouble of adjustment.

In this invention, the amplitude data of sine waves and cosine waves are stored in a memory device, and this memory device is used to control the rotation of the antenna.
In other words, it is configured to read out in synchronization with the rotation of the goniometer to obtain two balanced modulation signals having amplitude phases of a sine wave and a cosine wave.

In particular, the amplitude data stored in the memory coil in the memory is amplitude modulated pulse data separated by data representing DC voltage, this amplitude modulated pulse data is read out and DA converted, and the DA converted output is given to the DC blocking means. Accordingly, the structure is such that a balanced modulation signal can be obtained from this DC blocking means. As a result, according to the present invention, the structure is simple, and the phase adjustment of the azimuth component and the two-phase balanced modulation signal can be performed by electronic means. Display devices can be provided.

"Embodiment" FIG. 1 shows an embodiment of the present invention. In the figure, 1 is a pair of antennas with directivity, 2 is a high-frequency goniometer that extracts the azimuth component from this antenna 1,
3 indicates a motor that rotates the moving coil of the goniometer 2. 4 indicates a pulse generator. This pulse generator 4 is a high frequency goniometer 2
rotates in unison with one pulse CK ₁ per rotation,
It is assumed that one pulse CK ₂ is output every 0.2. 5 is an omnidirectional antenna for sense determination, 6
A and 6B are sense switches, 7 is a receiver, and 8 is a detector. Detection by the detector 8 is, for example, negative polarity detection, and the negative polarity detection output is supplied to the direction display device 9.

The direction display device 9 according to the present invention includes a pair of memory devices 1
1A, 11B, an address counter 12 that provides address signals to the memories 11A, 11B, and DA converters 13A, 13B that convert digital data read from the memories 11A, 11B into DA.
and amplifiers 14A, 14B that amplify the DA conversion outputs of the DA converters 13A, 13B to a predetermined level.
, DC blocking means 10A, 10B, resonators 15A, 15B excited by the output signals of the DC blocking means 10A, 10B, and resonators 15A, 15B.
A cathode ray tube display 16 whose output signal is given to an X-axis input terminal and a Y-axis input terminal, and a cathode ray tube display 1
The sense determining circuit 17 applies a brightness modulation signal to the brightness modulation terminal G of No. 6 and determines the direction of arrival of radio waves.

In this invention, a pair of memory devices 11A and 11
It is characterized in that amplitude-modulated pulse data including a carrier component having sine wave-like amplitude data and cosine-wave-like amplitude data is stored in B.

The signal waveforms read from this pair of memories 11A and 11B and subjected to DA conversion are shown in FIGS. 2A and 2B.
The amplitude modulated pulses Pa and Pb including carriers shown in FIG. 2A and B are set so that the envelopes of their peak values are in the form of sine waves and cosine waves, and data for one period is stored in the memories 11A and 11B. Write. The amplitude modulation pulses Pa and Pb each have their phases reversed in the first half period and the second half period in one period.
These amplitude modulated pulses Pa and Pb are
A, 10B, and by removing the DC component contained in the amplitude modulation pulses Pa and Pb, a so-called balanced modulation signal Sa, in which the phase of the carrier wave is inverted every half period as shown in C and D in Fig. 2, is generated. Sb is obtained.

For the memories 11A and 11B, semiconductor memories such as ROM can be used, for example. As for the resolution of the write data, for example, amplitude data changed by 0.2 degrees is written alternately with zero data for each address. Also, the resolution in the amplitude direction is, for example,
Quantize to 255 steps.

Memory units 11A and 11B are address counters 12
A count output signal is given from , and the addresses from the first address to the last address are repeatedly read out. This readout period is determined by applying a pulse CK ₂ output from the rotary encoder 4 at a resolution of 0.2° to the address counter 12 so as to match the rotation period of the high-frequency goniometer 2, and using the count output as an address signal in the memory 11A. _.
The relationship between the reading cycles of 11B is always made to match. 18 indicates a synchronous circuit, and this synchronous circuit 1
8, the timing at which the counter 12 is reset is made to match the timing at which the goniometer 2 passes the reference point.

Here, rotary encoder 4 and synchronous circuit 18
A phase adjustment means 21 is provided between the two. This phase adjustment means 21 is, for example, a preset counter 21.
A and a phase setter 21B which provides a set value to the preset counter 21A. The phase setter 21B can be configured by, for example, a digital switch.

The preset counter 21A can be either an up counter or a down counter. For example, a case where a down counter is used will be explained. Set a value corresponding to the delay angle in the phase setter 21B, and use the set value as the synchronization pulse.
It is sufficient to preset the preset counter 21A with CK ₁ and down-count the preset value with pulse CK ₂ . For example, synchronization pulse CK ₁
To delay by 1°, set 1/0.2 = 5, that is, set the digital value equivalent to "5" in decimal in the phase setter 21B, and input this set value to the preset counter 21A at the timing of the synchronization pulse CK ₁ . A down-count signal is generated from the preset counter 21A to which 5 pulses CK ₂ are input by presetting and down-counting the preset value with pulse CK ₂ .
CK ₁ ′ is obtained.

Therefore, by applying this carry down signal CK ₁ ' to the reset terminal R of the address counter 12 through the synchronization circuit 18, the phase of the reading start point of the memories 11A and 11B is delayed by 1° with respect to the rotational phase of the antenna 1. can be done. Therefore, by setting an arbitrary value to the phase setter 21B, it is possible to adjust the phase of the azimuth component and the phase of the two-phase balanced modulation signal generated from the memory devices 11A and 11B into an arbitrary relationship. As a result, even if the azimuth component obtained from the antenna 1 is delayed by the receiver 7, the detector 8, etc., the structure allows electronic adjustment of the reference point of the azimuth component and the phase of the two-phase balanced modulation signal. ing.

Amplitude modulated pulse data having sine amplitude data and amplitude modulated pulse data having cosine amplitude data read from the memories 11A and 11B are applied to DA converters 13A and 13B for DA conversion. this
Amplitude modulated pulses Pa and Pb shown in FIG. 2A and B are obtained by DA conversion.

These amplitude modulated pulses Pa, Pb are amplified to a predetermined level by amplifiers 14A, 14B as required, and supplied to DC blocking means 10A, 10B. The direct current blocking means 10A, 10B can be constituted by a capacitor. DC blocking means 10A, 1
By applying amplitude modulation pulses Pa and Pb to 0B, balanced modulation signals Sa and Sb shown in FIG. 2C and D are obtained. These balanced modulation signals Sa and Sb are sent to the resonator 15.
A and 15B, and the waveforms of the carrier components of the balanced modulation signals Sa and Sb are shaped into sinusoidal waves and are applied to the X-axis and Y-axis input terminals of the cathode ray tube display 16.

On the other hand, a constant DC bias voltage -E _B is applied to the reference voltage terminal REF of the DA converters 13A and 13B from a modulation signal source 19 constituted by an operational amplifier, and the other input terminal of this modulation signal source 19 is The detection output signal of the detector 8 is applied, and the detection output signal is superimposed on the DC bias voltage, and this superimposed signal is
It is applied to the reference voltage terminal REF of the DA converters 13A and 13B.

Reference numeral 17 indicates a sense determination circuit. This sense determining circuit 17 takes in the least significant bit signal of the address signal given to the memories 11A and 11B as a clock pulse, and includes a polarity setting circuit 17F that sets the polarity of the clock pulse, and a clock pulse of the polarity set by this polarity setting circuit 17F. A gate 17B for extracting the clock pulse at the time of sense determination, an amplifier 17C for amplifying the clock pulse extracted by the gate 17B to a desired amplitude, and a DC blocking means 17D for removing the DC component from the clock pulse amplified by the amplifier 17.
A resonator 17E for shaping the clock pulse, which has passed through the DC blocking means 17D and had its DC component removed, into a sine waveform, and a constant frequency signal having a sine waveform is output from the resonator 17E. The grit G of the cathode ray tube 16 is given as a brightness modulation signal for sense determination.

This sense determination circuit 17 includes a switch 6 for superimposing a signal received by the omnidirectional sense antenna 5 on a signal containing azimuth information given to the receiver 2 through the goniometer 2 at the time of sense determination.
A and a switch 17B provided for opening the gate 17B and turning on the switch 17B provided for supplying a clock pulse to the amplifier 17C, the circuit enters an operating state and enters a sense determination state.

"Operation" According to the configuration of the present invention described above, the memory device 11
Since amplitude data of sine wave and cosine wave amplitude modulated pulses are read out alternately from A and 11B together with zero amplitude data, the DA converters 13A and 13B output amplitude modulated pulses in the form of sine waves as shown in Figures 2A and B. It is possible to obtain a modulated amplitude modulated pulse Pa and an amplitude modulated pulse Pb including a cosinusoidally amplitude modulated carrier.

When there is no received signal, a constant bias voltage -E _B is applied to each reference voltage terminal REF of the DA converters 13A and 13B from the modulation signal source 19 constituted by an operational amplifier.
The amplitude modulated pulses Pa and Pb output from the DA converters 13A and 13B have sine wave and cosine wave amplitudes synchronized with the rotation of the goniometer 2. (See time points T ₀ to _{T 1} in Figure 3 D and F) This amplitude modulation pulse
By applying Pa and Pb to the DC blocking means 10A and 10B, a balanced modulation signal Sa (FIG. 3E) and a balanced modulation signal Sb (FIG. 3G) can be obtained. Therefore, the balanced modulation signals Sa and Sb are transmitted to the resonator 15A,
15B to the X and Y axes of the cathode ray tube display 11, a circle with a radius determined by the bias voltage -E _B is drawn on the surface of the cathode ray tube display 11, as shown in FIG. Here, resonator 15
If A and 15B are not provided, two-phase balanced modulation signal
Since the Sa and Sb carrier signals are given as rectangular waves to the X and Y axes, the speed at which the electron beam is deflected from one side to the other is fast, so a circle is drawn in which the inside does not shine at all. When such a display method is adopted, the resonators 15A and 15B are not required.

On the other hand, for example, if a radio wave arrives from a direction deviated by 90 degrees from the direction of the ship's course, the detected output signal of the detector 8 will have a waveform as shown at times T ₁ to _{T 2} in FIG. 3B. This detection output signal is modulated by a signal source 19
As a result, a signal on which the bias voltage -E _B detection output signal is superimposed is obtained at the output of the modulation signal source 19 as shown at time T ₁ to _{T 2} in FIG. 3C. By applying this superimposed signal to the reference voltage terminal REF of the DA converters 13A, 13B, the DA converters 13A, 13B output the signals from time T ₁ to D in FIG.
Amplitude modulated pulses Pa′ and Pb′ modulated to amplitudes as shown in T ₂ are obtained. This amplitude modulated pulse
By supplying Pa'Pb' to the resonators 15A and 15B through the DC blocking means 10A and 10B, balanced modulation signals Sa' and Sb' shown in FIGS. 3E and G are obtained from the resonators 15A and 15B. This balanced modulation signal
By applying Sa' and Sb' to the X and Y axes of the cathode ray tube display 16, a propeller-shaped image appears as shown in FIG. By turning on sense determination switches 6A and 6 while this propeller-shaped image is displayed, the direction of arrival of the radio waves is determined. It shows that there are two directions.
Therefore, it is necessary to determine the direction in which the radio waves arrive. This operation is called sense determination.

In order to determine the sense, the signal AA containing azimuth information output from the goniometer 2 shown in FIG. 9A is used.
The signal BB captured by the omnidirectional antenna 5 is superimposed on the signal BB. Since the pointing direction of the signal AA containing azimuth information outputted from the goniometer 2 is reversed once during one revolution of the moving coil of the high-frequency goniometer 2, the phase of the carrier is reversed, and the phase of the carrier changes to . On the other hand, the received signal BB of the omnidirectional antenna 5 has a constant phase, for example. Therefore, when combining signals AA and BB, we get
A composite wave CC shown in FIG. 9C is obtained. The maximum amplitude of this composite wave CC corresponds to the peak position of the phase of the signal AA, and the minimum amplitude corresponds to the peak position of the phase of the signal AA.

When this composite wave CC is applied to the receiver 7, subjected to negative polarity detection by the wave detector 8, and inputted to the modulation signal source 19, the signal DD shown in FIG. 9D is obtained at the output of the modulation signal source 19.

The signal DD is at the position where the composite wave CC has the maximum amplitude.
When the voltage approaches OV and the composite wave CC reaches its minimum amplitude, it approaches the bias voltage -E _B. Therefore, this signal DD
The reference voltage terminal REF of DA converters 13A and 13B
DA converters 13A and 13B by giving
The balanced modulation signals Sa and Sb output from the 9th
The signals shown in Figures G and H are amplitude modulated into the waveforms shown in GG and HH. In other words, Sa has a GG waveform, and Sb has a
Amplitude modulated to HH waveform.

Here, from the sense determination circuit 17 to the cathode ray tube 16
Sense determination brightness modulation signal II (see Figure 9 I)
When given, this brightness modulation signal II for sense determination
is the signal of the least significant bit of the address signal given to the memories 11A and 11B.
It matches the readout frequency of A and 11B. Therefore, it matches the frequency of the carrier included in the balanced modulation signals Sa and Sb. When the sense determining brightness modulation signal II is, for example, in a negative period, the cathode ray tube 16 is controlled to be cut off and the electron beam is cut off. Since the polarity of the carrier included in the balanced modulation signals Sa and Sb is reversed in synchronization with the 180° rotation of the moving coil of the goniometer 2, for example, the balanced modulation signal Sa
The cut-off period is the period in which Sb and Sb are shaded.

As a result, only one polarity of the amplitude modulated signals GG and HH outputted from the DA converters 13A and 13B at the time of sensing determination is displayed as shown in J and K of FIG. 9. By scanning the electron beam with these unipolar waveforms JJ and KK, only the cardioid KA of one polarity shown in FIG. 10 will be displayed. In addition, at the initial setting, the cardioid
If the direction of KA is opposite to the actual direction, by inverting the logical value given to the input terminal 17A of the polarity setting circuit 17F, the polarity of the brightness modulation signal II for sense determination is inverted, and accurate It can be set to the following state. The cardioid displayed from now on will be the KB on the opposite side.

The sense determining operation explained using FIG. 9 is not a unique operation according to the present invention, but is a conventionally well-known operation, so further explanation will be omitted here, but the important points here are: is memory unit 1
The signal of the least significant bit of the address signal given to 1A and 11B is used as the brightness modulation for sense determination, and by configuring it in this way, the brightness for sense determination matches the frequency of the carrier included in the balanced modulation signal. This has the advantage that a modulated signal can be easily obtained.

"Effect" As explained above, according to the present invention, the memory 11A reads the sine wave amplitude modulated pulse data and the cosine wave amplitude modulated pulse data separated by data representing direct current from the memory 11B, and stores the pulse data. The amplitude modulated pulse Pa by converting to DA
and Pb, and this amplitude modulated pulse Pa and Pb
Since the structure is such that the balanced modulation signals Sa and Sb are obtained by giving the DC blocking means 10A and 10B,
The rotational phase of the antenna 1 and the phase relationship between the two-phase balanced modulation signals Sa and Sb can be adjusted simply by adjusting the timing of starting reading of the memories 11A and 11B. This adjustment can be performed, for example, by the phase adjustment means 21, and by setting an arbitrary value to the phase setter 21B, the rotational phase of the antenna 1 and the phase of the two-phase balanced modulation signals Sa and Sb can be easily adjusted. be able to.

In other words, even if a phase rotation is applied to the azimuth component signal in the receiver 7, the detector 8, etc., the phase adjustment means 21 can correct the phase shift corresponding to the amount of phase rotation. As a result, there is an advantage that the effort required during installation can be significantly reduced.
Further, depending on the installation situation of the antenna 1, an azimuth error may occur. This orientation error can also be corrected by the phase adjustment means 21, and the structure is such that adjustment can be easily performed in this respect as well.

Also, since the amplitude modulation pulse data separated by data representing direct current is stored in the memories 11A and 11B, this amplitude modulation pulse data is read out,
DC blocking means 10A, 10B output the DA conversion output.
Balanced modulation signal Sa including the carrier just by giving
Since Sb can be obtained, the circuit structure can be simplified.

In other words, as disclosed in Japanese Unexamined Patent Publication No. 131574/1983, amplitude data of sine waves and cosine waves are stored in a storage device, and this amplitude data is read out to generate a balanced modulation signal whose amplitude changes in a sine wave shape. One possible method is to obtain a balanced modulation signal whose amplitude changes like a cosine wave, but such a method would require two double balanced modulators and a video carrier wave that generates the carrier of the balanced modulation signal. In addition to requiring a generator and a modulator, the circuit structure becomes more complex.
These balance adjustment operations also have the drawback of being more complicated and time-consuming.

In contrast, in the present invention, the storage devices 11A, 11
Since the signal can be converted into a balanced modulation signal by the combination of B and the DA converters 13A and 13B, the advantage is that the circuit structure can be greatly simplified compared to the case where a double balanced modulator is used.

"Embodiment of the Second Invention" In the first invention described above, the case where unipolar amplitude modulated pulse data is stored in the memory devices 11A and 11B has been described, but in the second invention of this application, as shown in FIG. Balanced modulation signal that swings positive and negative around zero
Sa and Sb themselves are stored in the storage devices 11A and 11B. In this case, DA converters 13A and 13B
A balanced modulation signal can be obtained directly from the DC blocking means 10A, 10B without the need for direct current blocking means 10A, 10B. however,
The DA converters 13A and 13B require bipolar DA converters capable of DA converting positive and negative digital signals.

As another example of the first invention, as shown in FIG. 7, it may be configured to store amplitude modulated pulse data having, for example, a positive polarity DC component E _DC .
In this case, the peak values of the amplitude modulated pulses P ₁ , P ₂ ,
P ₃ and P ₄ change in the form of a sine wave and a cosine wave, and the values on the opposite side E ₁ , E ₂ , and E ₃ are stored in the memory 1 as values representing directness.
1A and 11B.

In the case of this FIG. 7, the DA converters 13A, 13
B may have a function of DA converting a unipolar digital signal. In this case, by taking out the DA conversion output through the DC blocking means 10A, 10B, the balanced modulation signals Sa, shown in FIG. 2C and D, can be obtained.
You can get Sb. Furthermore, as a further example of the first invention, unipolar amplitude modulated pulse data including a DC component can be stored in the memories 11A and 11B as shown in FIG.

[Brief explanation of drawings]

FIG. 1 is a system diagram for explaining one embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the main parts of the present invention, and FIG. 3 is the operation of the entire direction display device according to the present invention. Waveform diagram for explaining, 4th
5 and 5 are front views for explaining examples of display results in the direction display device, FIG. 6 is a waveform diagram showing an embodiment of the second invention of this application, and FIGS. 7 and 8.
The figure is a waveform diagram for explaining a modified embodiment of the first invention, FIG. 9 is a waveform diagram for explaining the sense determination operation, and FIG. 10 is a front view for explaining the display state at the time of sense determination. It is. 1: Receiving antenna, 2: Goniometer, 3: Motor, 4: Pulse generator, 5: Omnidirectional antenna, 6A, 6B: Sense switch, 7: Receiver, 8: Detector, 9: Direction display device, 11A ,1
1B: Memory device, 12: Address counter, 13
A, 13B: DA converter, 14A, 14B: amplifier, 15A, 15B: resonator, 16: cathode ray tube display, 17: sense determination circuit, 18: synchronization circuit,
19: Modulation signal source, 21: Phase adjustment means, 21
A: Preset counter, 21B: Phase setter,
Pa: amplitude modulated pulse with sinusoidal amplitude;
Pb: amplitude modulated pulse with cosine wave-like amplitude;
Sa: Balanced modulation signal with sinusoidal amplitude, Sb:
Balanced modulated signal with cosine-like amplitude.

Claims (1)

[Scope of Claims] 1. A goniometer that extracts a received signal containing arrival direction information of radio waves from a direction-finding antenna; B. a motor that rotates a moving coil of this goniometer; and C. synchronized with the rotation of the moving coil of the goniometer. a pulse generator that generates a reference pulse representing a reference point of rotation and a clock pulse representing a minute rotational angular position of the movable coil of the goniometer; D reset by the reference clock output from this pulse generator; an address counter that counts E and generates an address corresponding to each rotational angular position of the movable coil of the goniometer; a first memory in which amplitude modulated pulse data whose value envelope is sinusoidal and data representing direct current are alternately stored; a second memory in which amplitude modulated pulse data whose peak value envelope is in the form of a cosine wave and data representing direct current are alternately stored in each address; A pair of DA converters that perform DA conversion on amplitude modulated pulse data and data representing direct current, respectively; A balanced modulation signal in which a direct current component is removed from a pulse and an amplitude modulated pulse having a cosine wave envelope separated by a voltage representing direct current, and the envelopes on the positive side and negative side change in the form of a sine wave.
A cathode ray tube in which the two-phase balanced modulation signal extracted through the direct current blocking means is applied to the X-axis and Y-axis. and J Apply a voltage corresponding to the level of the received signal obtained from the moving coil of the goniometer to the reference voltage input terminal of the DA converter, and modulate both of the two balanced modulation signals according to the received signal level. A direction display device comprising: a modulated signal source; 2 A: A goniometer that extracts a received signal containing information on the direction of arrival of radio waves from a direction-finding antenna; B: A motor that rotates the moving coil of this goniometer; C: A motor that synchronizes with the rotation of the moving coil of the goniometer and represents a reference point for rotation. a pulse generator that generates a reference pulse and a clock pulse representing a minute rotational angle position of the movable coil of the goniometer; an address counter that generates an address corresponding to each rotation angle position of the moving coil; A first memory device stores amplitude modulation pulse data that alternately changes between positive and negative, and F is read out in address order by an address signal output from the address counter, and each address has a a second memory storing amplitude modulated pulse data whose side and negative side envelopes alternately change between positive and negative in the form of a cosine wave; A pair of DA converters that respectively perform DA conversion on data and output balanced modulation signals including carrier waves; I Apply a voltage corresponding to the level of the received signal containing azimuth information obtained from the moving coil of the goniometer to the reference voltage input terminals of the pair of DA converters, and adjust both of the two balanced modulation signals to the received signal level. A direction display device comprising: a modulation signal source that modulates according to; 3A It is equipped with an omnidirectional antenna and a direction-finding antenna whose directional directions are orthogonal to each other, and a reference pulse synchronized with the rotation of a moving coil of a goniometer connected to the direction-finding antenna. , has a clock generator that generates a clock pulse for each minute rotation angle of the moving coil, reads out sine wave and cosine wave data from the memory by the clock pulse output from this clock generator, and sends this read output to the DA converter. A two-phase balanced modulation signal is created by converting it into an analog signal, and this two-phase balanced modulation signal is combined with the azimuth information to display the arrival direction of the radio wave, and the direction information is combined with the direction information received by the omnidirectional antenna In a direction display device equipped with a sense decision switch that determines the arrival direction of radio waves by superimposing signals, when the sense decision switch is turned on, a switch that operates in conjunction with the sense decision switch A gate controlled to be open is provided, and a pulse signal of the least significant bit which alternately repeats H logic and L logic is extracted from the address signal applied to the memory through this gate, and the pulse signal of the least significant bit is extracted by this gate. An azimuth display device characterized in that the pulse signal of the least significant bit is applied to a display device as a sense determination brightness modulation signal.