JPH0352427A - Circuit for detecting fault of diode switch - Google Patents

Abstract

PURPOSE:To surely detect any kind of fault of a diode by detecting a beat frequency component generated at a time when transmission output from two transmitters are mixed and sent to an antenna due to the fault of a diode switch. CONSTITUTION:When the diode of the diode switch 3 is deteriorated, etc., and its impedance is changed, the transmission output (input 1, input 2) from the transmitter cannot be blocked with a diode D1 or D2. Consequently, the transmission output (input 1, input 2) from the two transmitters are mixed and outputted from an output terminal P0 to an antenna feed line 7. The fault of the diode can be detected by detecting a beat signal generated at such a case with a detector 6 and a beat frequency component detecting part 9. In such a manner, the fault of the diode can be completely detected extending over a wide range.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figure 4) Means for solving the problems to be solved by the invention (Figure 1) Working examples (Figure 2) , Fig. 3) Effects of the Invention [Summary] Regarding a failure detection circuit for a diode switch, in particular, it is possible to detect a change in only the capacitance due to element deterioration in the failure detection of a diode that is placed next to the diode switch, and to detect a diode failure. For the purpose of ensuring reliable detection, in a diode switch failure detection circuit that switches the transmission output of two independent frequencies and sends it to the antenna, the output terminal of the diode switch is connected to the transmission output of the output terminal. The detector is equipped with a detector that detects the beat frequency component, and a beat frequency component detector that extracts only the beat frequency component from the output of the detector. Detection is performed, and the beat frequency component detection section extracts only the beat frequency component and detects the damage caused by the diode switch! It is configured to perform I detection.

[Industrial application field]

The present invention relates to a failure detection circuit for a diode switch, and more specifically, it relates to a pin (PIN) diode, etc. that turns on/off signals in a frequency range above the UHF band, such as for switching the transmission output of a hot standby type microwave radio device. A failure detection circuit for a diode switch that is used to detect failures in diode switches that have been used in the past, and that is particularly capable of reliably detecting failures due to deterioration of diodes.

[Conventional technology]

Conventionally, in the frequency range above the UHF band, for example, for switching the transmission output of hot standby type microwave radio equipment,
Diode switches constructed with PIN diodes were commonly used as the means used to turn signals on and off.

The diode switch was provided with a diode switch failure detection circuit for detecting failure.

Figure 4 shows one of the conventional diode switch failure detection circuits.
It is a figure showing an example.

In the figure, l, 2 are transmitters, 3 is a diode switch, 4 is a diode drive control section, 5 is a diode monitoring section,
6 indicates a wave detector, and 7 indicates an antenna feed line.

In addition, D1 and D2 are diodes (PI-N diodes) connected at a position λ/4 (λ: wavelength) from the output terminal Po.
, L1 and L2 are choke coils, Trx and Trt are transistors, A1 to A3 are amplifiers, C l-
C4 is a compling capacitor, R1, R! shows resistance.

In the diode switch drive control section 4, the input 1dt
When is applied to the transistor 7r1 to turn it on, current flows in the order of the diode D1 → choke coil L+-"resistor R1-}transistor Trt, and the diode switch 3
The diode DI is driven and turned on, resulting in a low impedance state.

At this time, the transistor Tr! is off, diode D2
If it is off, it is in a high impedance state. In such a state (Ds on, D! off), the output from transmitter 1 is the diode D! The output from the transmitter 2 is not supplied to the antenna, and only the output from the transmitter 2 is supplied to the antenna via the antenna feed line 7.

Further, the transistor Tr1 is turned off, and the transistor Tr! When input Id2 is applied to turn it on, a current flows in the order of diode D2 -> choke coil L2 - resistor R2 -> transistor Tr2, turning on diode D2 and entering a low impedance state. In this state (Ds off, D2 off), the output from transmitter 2 is blocked by diode D2 and is not fed to the antenna, and only the output of transmitter l is fed to the antenna.

In this way, by controlling the transistors Trl and Trshi to turn on/off, the diodes D1 and D2 can be turned on/off.
It can be turned off, thereby allowing the transmission outputs of transmitters 1 and 2 to be switched and supplied to the antenna.

Apart from the switching operation described above, a diode monitoring section 5 is provided to monitor failure of the diode. In this diode monitoring section 5, the diode switch drive control section 4
The voltages of resistors R1 and R2 are taken out and the voltages of amplifiers AI and At
and amplify the alarm signals ALM1 and ALM, respectively.
Outputs * to monitor diode failure.

For example, suppose that the on-resistance of the diode D2 has increased due to element deterioration or the like. In this state, if diode D1 is turned off and diode D2 is turned on, the transmission output of transmitter 1 is supplied to the antenna, and at the same time the output from transmitter 2 cannot be completely blocked by diode D2. Supplied to the antenna.

Therefore, the output of the transmitter 1 and the output of the transmitter 2 interfere with each other, reducing line quality.

As mentioned above, the diode of diode switch 3 is
When the on-resistance increases due to element deterioration, the control current of the diode flowing through the transistor Tr1 or Tra changes.

This change in control current is tapped off via the resistor Rtx Rl and produces an alarm signal A L M ! , ALM2, so the alarm signal ALM! Alternatively, by checking ALM2, a diode failure can be detected.

In addition, as described above, the transmitter 1 and the transmitter 2 are switched by the diode switch 3, and the transmission output is sent from one of the transmitters to the antenna via the antenna feed line 7, but at this time, The transmission output is detected by a detector 6 connected to the antenna feed line 7, and the amplifier A
3 and output as a DC voltage output for use in monitoring, etc.

[Problem to be solved by the invention]

In the conventional device as described above, when detecting a failure of a diode that constitutes a diode switch, it is possible to easily detect a change in the on-resistance of the diode.

However, when a diode fails and only the capacitance between the electrodes changes (increases), the failure cannot be detected because the control current of the diode does not change.

The present invention eliminates these conventional drawbacks and makes it possible to detect failures in diodes constituting a diode switch, in particular by detecting changes in only the capacitance due to element deterioration, thereby ensuring reliable detection of diode failures. The purpose is to do so.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention, and the principle of the present invention will be explained below based on this diagram.

In the figure, 1 and 2 are mutually independent frequencies fl and f.
2 transmitter, 3 diode switch, 6 detector, 7
8 is a DC voltage monitoring section, 9 is a beat frequency detection section, DI and D2 are diodes, and H is a hybrid.

The baseband signal is split by hybrid H and sent to transmitters 1 and 2. The transmit power from transmitters l and 2 is switched by diode switch 3,
Either one of the transmission outputs is sent from the output end Pa to the antenna via the antenna feed line 7.

In such a hot standby type microwave radio device, transmitters 1 and 2 use independent frequencies. For this reason, the diode D! Alternatively, if D2 deteriorates and as a result, the diode cannot block the transmission output, the outputs of transmitters 1 and 2 are mixed and sent to the antenna from the output terminal P0 via the antenna feed line 7. It may happen.

In such a case, when the output sent to the antenna feed line 7 is subjected to combined detection, a beat (difference frequency) signal is generated.

The present invention has been made focusing on this point, and includes a detector 6 on the antenna feed line 7 and a beat frequency component detection section 9.
The beat frequency component generated due to deterioration of the diode is extracted and the failure of the diode is detected.

Note that the DC voltage monitoring unit 8 extracts a DC voltage signal from the output of the wave detector 6 and monitors the power passing through the antenna feed line 7 using a meter or the like.

[Effect]

Since the present invention is structured as described above, it has the following effects.

In a hot standby type device in which transmission output is switched using a diode switch, the diodes constituting the diode switch may fail due to deterioration or the like.

In such a case, if the on-resistance of the diode changes, it is possible to detect a fault using the conventional method, but if only the capacitance changes, the fault cannot be detected by the conventional method.

However, in the present invention, since a beat signal caused by a diode failure is detected, it becomes possible to detect the above-mentioned diode failure, which was previously impossible.

Therefore, diode failure detection can be performed more reliably. 〔Example〕 Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a block diagram of the first embodiment of the present invention, and the same reference numerals as in FIGS. 1 and 4 indicate the same parts.

In the figure, R3 is a coupling resistor, D3 is a detection diode, C6 is a DC blocking capacitor, D4 is a rectifying diode, C7 is a smoothing capacitor, C5 is a detection capacitor, 10 and 11 are Schott circuits (SCH ), ALM3
, ALM4 indicates an alarm output, and A4 indicates a low frequency amplifier.

The diode switch 3 is the same as the conventional example (see FIG. 4), and the diodes Dl and D2 are connected to the output terminal Po.
Connect at a position λ/4 (λ: wavelength) away from

A detection diode D3 and a detection capacitor C5 are connected to the output terminal Po (antenna feed line 7) via a coupling resistor R3 of the detector 6.

The output of the detection circuit 6 is sent to the low frequency amplifier A via the DC blocking capacitor C6 of the beat frequency detection section 9.
4 and amplify the level. Then diode D4
After rectifying with C7 and smoothing with capacitor C7, level detection is performed with Schmitt circuit IO.

In this Schmitt circuit 10, it is detected whether the beat frequency component is equal to or higher than a predetermined value, and an alarm A L M
Outputs 4.

The output of the detector 6 is input to the DC amplifier A3 of the DC voltage detection section 8, and after being amplified, it is taken out as a monitor output, and is monitored with a meter (voltmeter), etc. SCH)11 detects whether the DC level is above a predetermined value and sends an alarm signal AL.
Output M3.

The above-mentioned monitor output and alarm signal ALM3 can be used not only for conventional monitoring but also for monitoring the passing loss of the diode switch 3, detecting a failure of the diode switch, and the like.

The diode of diode switch 3 has deteriorated,
If its impedance changes, the transmitted output from the transmitter (input 1, human power 2) will be changed by the diode D! Or it becomes impossible to prevent it with the amount of D.

Therefore, as explained in the conventional example, the transmission outputs (input 1, input 2) from the two transmitters are mixed and output from the output terminal PO to the antenna feed line 7. If the beat signal generated in this case is detected by the wave detector 6 and the beat frequency component detection section 9, a failure of the diode can be detected.

Even if only the capacitance of the diode changes and the control current of the diode does not change, this beat signal can be detected if a mixed output appears at the output terminal Po, so it can be detected against a wide range of diode failures. This means that it can be detected sufficiently.

FIG. 3 is a block diagram of the second embodiment, and the same reference numerals as in FIGS. 1, 2, and 4 indicate the same parts.

In this embodiment, a failure diode determination section 12 is provided to determine which diode has failed and to issue an alarm signal A.
It is designed to output LMs.

The alarm signal ALMa from the beat frequency component detection section 9 and the diode drive control signal from the diode switch drive control section 4 are input to the faulty diode determination section l2.
For example, by taking the AND of both signals, it is determined which diode is faulty, and the alarm signal AL
Output Ms.

〔Effect of the invention〕

As explained above, the present invention has the following effects.

That is, in the present invention, when outputs from two transmitters with independent frequencies are switched by a diode switch and supplied to the antenna, two
The transmission outputs from the two transmitters are mixed and sent to the antenna, and at this time, the beat frequency component can be extracted by synthetically detecting the mixed output. By detecting this beat frequency component, failures such as deterioration of diode elements in the diode switch are detected, so that any type of diode failure can be reliably detected.

[Brief explanation of drawings]

FIG. 1 is a principle diagram of a failure detection circuit for a diode switch according to the present invention, FIG. 2 is a block diagram of the first embodiment of the present invention, FIG. 3 is a block diagram of the second embodiment of the present invention, and FIG. The figure is a block diagram of a conventional example. 1, 2-・One transmitter 3-・Diode switch 6
- Detector 8 - DC voltage detection section 9 - Beat frequency component detection section

Claims (1)

[Claims] In a failure detection circuit for a diode switch that switches transmission outputs of two independent frequencies and sends them to an antenna, a detector (6) is provided at the output end of the diode switch to detect the transmission output of the output end. and a beat frequency component detection unit (9) that extracts only the beat frequency component from the output of the detector (6), and detects when the two transmission outputs are mixed and output due to a failure of the diode switch. 1. A failure detection circuit for a diode switch, characterized in that a failure detection circuit for a diode switch is performed by performing synthetic detection by a detector (6), and further extracting only the beat frequency component by a beat frequency component detection unit (9).