JPS6140071B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a diode failure detection circuit that determines the quality of a plurality of diodes provided on the same substrate.

2. Description of the Related Art A so-called diode as a semiconductor element is widely used in the field of electronic communication as a rectifying element or a switching element due to its function.

For example, when considering the use as a switching element, depending on the application, a large number of elements are often used in one circuit mechanism, and each element often performs an important function.

As an example, a PIN is used as a phase shift switching control mechanism in a phase shifter that constitutes an electronic scanning antenna.
A diode is used.

As is well known, an electronic scanning antenna consists of, for example, several hundred radiating elements, each of which is connected to a digital phase shifter that controls the phase of the microwave signal. An example of a digital phase shifter is as shown in Figure 1, which is mounted on an alumina substrate at 22.5° (π/8 bits), 45° (π/4 bits), 90° (π/2 pits),
Phase shift circuits 1, 2, which provide a phase shift amount of 180° (π bits)
3 and 4 are formed respectively. The phase shift circuits 1, 2, and 3 are called loaded line type phase shift circuits, and the other phase shift circuit 4 is called a hybrid type phase shift circuit.

By combining these phase shift circuits, a phase shift amount of 0 to _337.5 degrees is obtained at intervals of 22.5 degrees _. ...Determined by the forward or reverse switching control of _D9 . The microwave signal is then introduced into the input terminal 5, and a phase-shifted signal is derived from the output terminal 6 and supplied to a radiating element (not shown).

The switching control signals for the diodes D ₁ , D ₂ , . . . D ₉ are performed by the voltage switching 8 operation from the DC power supply 7 . However, in reality, this is done by converting the so-called TTL signal from the scan control computer into a drive voltage, and the drive voltage at a phase shift of 0 is, for example,
0.9V (current 100mA), drive voltage in phase shift state is about -20V (current 0). However, in such an electronic scanning antenna, if a failure occurs in the phase shifter, the beam pattern obtained by the radiating element will be distorted, and the beam scanning will be in a state different from the phase shift control signal to the phase shifter. Therefore, there is a high risk of obtaining incorrect radar information that is contrary to expectations. Particularly considering that this type of antenna system is used, for example, in an aircraft landing guidance system, in some cases even the failure of even one diode may cause a dangerous situation that may threaten human life.

The present invention was made against this background, and relates to a diode failure detection circuit that can check in advance for phase shifter failures due to diode failures. In operation, a so-called Bilt-In-Test (Bilt-In-Test) is used to instantly detect the quality of the diode during actual operation.
Equipment-BITE) method is required. Therefore, possible byte methods include a method that measures the insertion loss of a high-frequency signal passing through a phase shifter and the amount of phase shift itself, and a method that measures the terminal voltage of a diode that constitutes the phase shifter. However, the former method has the drawback that the configuration of the measurement circuit and device is extremely complicated, making it impractical; however, the latter method, which measures the terminal voltage of the diode, can detect whether the phase shifter is functioning properly with a relatively simple circuit configuration. .

A possible circuit example in this case will be explained with reference to FIG. 2, which shows only a 1-bit phase shifter. The two-pole voltages +2V and -15V of the DC power supply 7 are supplied to the switching circuit 8. . The switching circuit 8 has a switching transistor 81 driven by a control signal from the scan control computer, and its switching output voltage
Vd is supplied to diodes D ₁ and D ₂ of a phase shift circuit which is a failure detection circuit in the next stage, and is simultaneously supplied to one input terminal + of the comparator circuit 9.

A reference voltage source 10 for deriving a comparison reference voltage Vr is connected to the other input terminal - of the comparison circuit 9.
Therefore, the terminal voltage Vd of the diodes D ₁ and D ₂ is usually about 0.8V in a forward bias state and about -15V in a reverse bias state. Here, if the comparison reference voltage Vr in the forward operation state is set to 1.2V, then in the normal forward operation state, the relationship of Vd<Vr is established and no comparison output is obtained. In this state, if we assume that diodes D ₁ and D ₂ fail and both become electrically open, Vd will be around 2V and Vd > Vr, and the comparison output will be reversed, indicating a diode failure. An output of level "1" is obtained.

Next, if the comparison reference voltage Vr is set to -1.5V when the diodes _D1 and _D2 are operating in the reverse direction, Vd will be -15V under normal conditions, and Vd<Vr.
The relationship holds true. In this state, the diode D ₁ ,
If _D2 fails and short circuits (shert), Vd becomes 0V, so the comparison output similarly inverts, Vd>Vr, and a signal level "1" appears at the output of the comparison circuit 9, allowing the detection of a diode short circuit failure.

In the above example, a case has been described in which diodes D ₁ and D ₂ fail at the same time, but in reality, even if only one of the diodes fails, it will no longer function as a phase shifter.

Therefore, if one diode becomes open due to a failure, reduce the current applied to the diode by 50~
When set to 100mA, Vd is at most 30% compared to the normal state.
It is only ~40mV higher. Therefore 30-40mV
In order to reliably detect a slight voltage fluctuation as a failure, the reference voltage Vr must be set to Vd in the normal state.
It is inconvenient if it is not set so that <Vr<(Vd+30mV). In other words, the reference voltage Vr must be set to a level that is only slightly higher than Vd, at most 30 mV. However, setting such a small high level and maintaining it accurately is difficult due to temperature changes in the diode terminal voltage Vd,
This is difficult to realize if fluctuations in the reference voltage Vr are taken into consideration.

In fact, if the diode bias current is 100mA and the ambient temperature is varied from -10℃ to +50℃,
Since Vd changes by about 100 mV, it is necessary to change the reference voltage Vr according to this temperature change in order to accurately detect the presence or absence of a failure. However, the reference voltage
Although it is theoretically possible to correct Vr by accurately following the temperature change at the location where the diode is installed, in reality, it is necessary to install a temperature sensor,
This is not possible because it requires the addition of a temperature control mechanism, etc.

Therefore, the present invention has been made in view of these circumstances, and therefore provides a diode failure detection circuit that can reliably detect even one open failure among multiple connected diodes and is unaffected by temperature changes. It is something to do.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a circuit diagram showing an embodiment of the present invention. In FIG. 1, the same components as in FIGS. 1 and 2 are given the same reference numerals, and detailed explanations will be omitted.

In particular, the DC power supply 7 and switching circuit 8 are the same as those shown in FIGS. 1 and 2, so they are omitted from the drawings.

Bit phase shifters 1 and 2 constituting the same phase shifter in FIG. 3 are provided on the same substrate, and each includes switching element diodes D ₁ , D ₂ , D ₃ , and D ₄ . Therefore, the diode terminal voltages of the first bit and second bit obtained by the bias voltage via the DC power supply 7 and the switching circuit 8 are V _A ,
Let it be _VB . The output terminal of the first bit is attenuator 1
1. Connected to one terminal + of the first comparator circuit 91 via the distributor 12, and the input level at this time is
Let it be V ₁ . Further, the voltage of this input level V ₁ branched by the divider 12 is sent to the second comparator circuit 92.
is connected to the other terminal -. On the other hand, the output terminal of the second bit is directly connected to the first bit via the voltage divider 13.
is supplied to the other terminal - of the comparator circuit 91, and the input level at that time is set to _V2 .

The voltage at this input level V ₂ is divided by the voltage divider 13 to a level V ₃ , and the second comparison circuit 9
is supplied to one terminal + of 2. In other words, the diode failure detection circuit of the present invention is characterized in that, in order to detect a diode failure, it forms a pair with another diode on the same substrate, and configures the failure detection circuit with the other diode as a reference. be.

Therefore, the inputs of the comparison circuits 91 and 92 are normally
V ₀ < V ₂ , V ₃ < V ₁ and no output is obtained, but V ₁
>V ₂ , V ₃ >V ₁ , the output level is inverted and a level “1” signal is derived.

Therefore, assuming that the diode bias state of each of the first and second bits is in the forward direction, V
_A and _VB are each about 0.8V. Therefore, in such a normal state, the resistances of the attenuator 11 and the voltage divider 13 are adjusted so that the following equation (1) holds between each voltage level.

V ₂ >V ₁ >V ₃ (1) In such a state, it is first assumed that the diode of the first bit becomes open due to a failure. In this state, V _A becomes large, and therefore V ₁ >V ₂ , so the output of the comparator circuit 91 is inverted and an output of level "1" appears. In addition, in the other comparison circuit 92, even if V ₁ becomes large, V ₁ >V ₃
Since the relationship does not change, the level "0" of the comparison circuit 92 does not change.

Furthermore, if the second bit diode becomes open due to a failure, V ₁ <V ₂ and the output of one comparator circuit 91 remains at level "0", or conversely, V ₃ > V ₁ , and the other comparison circuit 9
The output level of "2" is inverted, and an output of level "1" is obtained.

Next, consider a diode short-circuit failure. First of all
If the diode of the bit is short-circuited due to a failure, V _A =0V and V ₁ =0V. As a result, the comparator circuit 91 has V ₁ <V ₂ and there is no change in the output, but the comparator circuit 92 has an inverted state and V ₃ >V ₁
As a result, a signal level "1" appears at the output.

Similarly, when a short-circuit accident occurs in the diode of the second bit, the output level of the comparator circuit 91 is inverted to "1", and the output of the other comparator circuit 92 remains unchanged.

In this way, if there is no change in the output of either of the comparison circuits 91, 92, both diodes are in a normal state, and conversely, if either of the comparison circuits 91,
If an output signal appears at 92, it can be seen that one of the diodes has an open or short circuit failure.

In this embodiment, the first bit and the second bit are also composed of the same type of PIN diode and are provided on the same substrate. Therefore, even if the temperature of this phase shifter itself changes, the diode terminal voltages V _A and V _B of each bit change in the same tendency, so the relative values of the voltages V ₁ , V ₂ , and V ₃ are as follows. , almost unchanged. Therefore, it can also be said to be a detected signal.
Since the level difference between V ₁ , V ₂ , and V ₃ can be set to be considerably small, it is possible to detect even a reversal phenomenon caused by a slight voltage fluctuation.

That is, in a normal state, if each voltage level difference is ΔV and the attenuator 11 and voltage divider 13 are set so that ΔV = V ₂ - _{V 1} = V ₁ - V ₃ , then the numerical example given above If you refer to ΔV,
If it is set to 15mV, even voltage fluctuations of about 30mV that occur when one diode becomes open can be made accurate.

As described above, the diode failure detection circuit according to the present invention can sensitively and reliably detect abnormalities in the terminal voltage of the diode, so it can detect not only failures in the diodes themselves that constitute the phase shifter, but also detection in the driver circuit that supplies bias voltage to the diodes. This has the advantage that abnormalities in the diode terminal voltage caused by failures can be immediately detected.

In the above embodiment, a phase shifter consisting of two bits was explained, but in actual array antennas, one phase shifter consists of, for example, π/8, π/4, π.
Since it consists of a 4-bit phase shifter consisting of /2, π bits,
It is only necessary to add one more circuit shown in FIG.

In the above embodiment, if both the first and second bits simultaneously cause the same type of failure, the comparison circuits 91 and 92 cannot detect it. However, in reality, it is extremely rare for both bits to have the same mode of failure. In order to detect a failure even in such a rare case, the comparator circuits 95 and 96 may be configured in combination with other bit phase shifter circuits as shown in FIG. Also in FIG. 4, it is possible to detect any combination of failures as long as the four bits 1, 2, 3, and 4 do not fail in the same mode.

Further, as long as the combination of detection diodes is on the same substrate, it is not necessarily necessary to perform comparative detection between adjacent diodes, and the combination can be arbitrary.

In the above embodiment, the diode failure detection circuit in a diode phase shifter was described as an example, but the present invention is not limited to this and can be applied to failure circuits of various devices using diodes such as diode switches.

As described above, the diode failure detection circuit according to the present invention compares the terminal voltages of diodes on the same substrate and detects the fluctuation of the voltage difference in the event of a failure. This has great practical effects, such as eliminating the need for a temperature detection circuit or its correction circuit.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a phase shifter using diodes, Figure 2 is a circuit diagram of a conventional diode failure detection circuit, Figure 3 is a circuit diagram of an embodiment of the present invention, and Figure 4 is a circuit diagram of a phase shifter using diodes. The figure is a circuit diagram showing another embodiment of the present invention. 1, 2, 3, 4...Bit phase shifter, 7...DC power supply, _D1 to _D9 ...Diode, 9,91,96
...Comparison circuit.

Claims (1)

[Scope of Claims] 1. A DC power source that supplies a DC voltage; first and second diodes each having one terminal connected to the DC power source and provided on the same substrate; a divider connected to the one terminal via an attenuator; a voltage divider connected to the one terminal of the second diode; and one output from each of the divider and the voltage divider. a first comparator that compares signals; and a second comparator that compares the other signal output from each of the divider and the voltage divider; One of the output signals is V ₁ and V ₂ , and the other signal output from each of the distributor and the voltage divider is
By setting V ₄ and V ₃ and satisfying the relationship of V ₁ = V ₄ and V ₃ < V ₁ < V ₂ , a failure of the pair of diodes is detected from the output results of the first and second comparators. A diode failure detection circuit characterized by: