JPH03185943A - Elimination device for narrow band interference signal - Google Patents

Abstract

PURPOSE:To obtain a small sized interference wave suppression system by detecting a signal intensity of a SAW propagating in the opposite direction with a pn diode, acquiring the information of the intensity of a spectrum of an input signal and using a feedback circuit so as to implement propagation control adaptively. CONSTITUTION:A part consisting of an input transducer group 17 and a 2nd pn diode array group 20 is a part monitoring the intensity distribution of an input spectrum. Input/output transducer groups 17, 18 act like a classification filter classifying the input signal in response to the frequency, propagating and synthesizing the signals again. A 1st pn diode array group 19 on a SAW propagation line provided for each channel controls the attenuation constant of a SAW of each channel. The operation of a narrow band interference suppression filter AISF shown in figure is as follows: An input signal is subject to SAW conversion by the input transducer group 17, monitors a bias shift quantity of the 2nd pn diode array group 20 and a bias control circuit 21 controls a bias voltage of the 1st pn diode for propagation control accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a narrowband interference signal removal device suitable for spread spectrum (SS) communication systems and the like.

[Summary of the invention] Two diode array groups are provided in the SAW propagation path, and one
A narrowband interference signal that detects the SAW signal strength propagating in the opposite direction using one diode array group to obtain information on the spectral strength of the input signal and control the bias of other diode array groups accordingly. It is a removal device.

[Conventional technology] Spread spectrum (SS) that uses a wide frequency range
One of the problems with communication systems is that high-level narrowband interference causes communication failure or high error rates. To solve this problem, surface acoustic waves (SAW)
A filter using a filter has been invented.

As a means to solve the above problem, the present inventors previously proposed Japanese Patent Application No. 63-180822 and Japanese Patent Application No. 63-278769.
No. 63-284884 has been filed.

[Problems to be Solved by the Invention] The invention of the earlier application still leaves room for improvement in the following points.

For example, Japanese Patent Application No. 63-278769 and Japanese Patent Application No. 63-2
In No. 84884, the adaptive operation of narrowband interference suppression is performed by utilizing the self-bias effect of a pn diode array provided in the SAW element, but in this case, the input signal requires relatively large power.

Furthermore, since Japanese Patent Application No. 180822/1982 uses a programmable notch filter without an adaptive function, an input signal monitor circuit and a bias control circuit are required as external circuits.

Further, in the above-mentioned prior patent, the impurity concentration in the Si substrate needs to be low, that is, it needs to have high resistance due to the operating principle of the device.

Therefore, it is essential to form a silicon epitaxial layer with high resistance.

[Object of the Invention] An object of the present invention is to improve the performance of an adaptive narrowband interference suppression system useful in spread spectrum communication systems.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a laminate including a first conductivity type high resistance silicon substrate, an insulating film, and a piezoelectric film, and a laminate formed on the piezoelectric body, an input transducer that frequency-classifies an input signal and generates a plurality of propagation paths; an output transducer that is formed on the piezoelectric body and obtains an output signal from a surface acoustic wave propagated to each propagation path; a first PN diode array formed on the surface side of the first conductivity type silicon substrate in an area sandwiched between each input/output transducer; a second PN diode array group formed on the surface side of the first conductivity type silicon substrate and opposite to each of the first diode array groups with respect to each input transducer; The gist includes detection terminals each independently drawn out from the PN diode array, and bias application terminals each independently drawn out from the first PN diode array.

[Operation] The present invention adds a function to monitor the spectrum intensity of the input signal to the configuration of the earlier patent. In conventional devices, the signal strength of one of the bidirectionally propagating SAWs excited by the input transducer is controlled by a pn diode array provided in the propagation path. That is, the SAW propagating in the opposite direction is not utilized.

In the present invention, the signal strength of the SAW propagating in the opposite direction is
This has been improved so that the information on the spectrum intensity of the input signal is obtained by detection with an n-diode, and the propagation control can be performed adaptively according to the actual usage situation and in accordance with any radio wave environment using a feedback circuit.

In addition, in order to simplify the process, the structure of the Si substrate is
This structure does not include an epitaxial layer and includes only a high-resistance Si substrate.

[Example] The present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 1 shows the configuration of a SAW element for one channel having one center frequency in which there is a narrowband interference signal canceling apparatus according to the present invention.

In the figure, 1 is a high resistance p(n) Si single crystal substrate, 2
is a thermal oxide film layer formed on the substrate, 3 is a ZnO piezoelectric thin film formed on the thermal oxide film layer, and 4, 5.6 are metal electrodes formed thereon, each having a surface wave comb shape for input. A transducer, an output surface wave comb transducer, and a gate electrode.

7 is p (n) type Si under the metal electrode of the transducer.
This is a high-concentration impurity diffusion region formed within the transducer, and serves to improve the excitation efficiency of the transducer. 8 is a p (n) type Si substrate 1 under the gate electrode 6
an n” (p”) impurity diffusion region formed within the
9 is a p''(n'') impurity diffusion region formed in the p(n) type Si substrate l below the gate electrode 6, and a first pn diode array is formed along the SAW propagation path. . As shown in the prior patent, the operation of this pn diode array is such that the carrier density in the silicon substrate is controlled by controlling the diode bias, and the interaction between the SAW and the carriers increases the attenuation constant of the SAW to 100 dB/c.
It also plays a role in significantly changing the amount by more than m. In other words, it has the ability to turn channels on and off quickly. 10
is the p(n) type Si substrate 1 outside the input transducer.
an n(p) impurity diffusion region formed within the second pn diode array; 11 is a resistor connected to the pn diode array, and 12 is a DC power supply.

13 is a voltage signal monitor terminal where the input signal is converted to SAW and detected by the second pn diode array;
This is the terminal at which the strength (power) of the input signal within that channel (frequency range) is observed as a voltage change. 14 is a bias control terminal of the first pn diode array.

Although not shown in the figure, an improved version of the earlier application may also be considered. This structure has the first pn diode array (8 and 9) for propagation control shown in FIG. 1 extended to below the input transducer 4, which further improves the filter characteristics. Next, the SAW signal detection function by the second pn diode array of the present invention will be explained. A second pn diode array 10 located outside the input transducer 4 is biased via a resistor 11 with a DC power supply 12 . 7- The best bias point of SAW detection sensitivity is at a slightly forward biased point.

The SAW converted by the input transducer is the second pn
Spatially propagates the diode potential on the diode array,
Modulated in time. The nonlinear resistance of the second pn diode generates a DC component that depends on the SAW signal strength, and the potential of the monitor terminal 13 shifts from the initial bias voltage to the reverse bias voltage. This shift amount corresponds to the input signal strength.

FIG. 2 shows the relationship between the input signal power and the bias shift amount of one monitor terminal. The bias shift amount is the SAW power (
It is proportional to the square of the input signal power).

In this way, the SAW potential is square-law detected by the pn diode array provided outside the input transducer, and the input signal strength is obtained as a baseband signal.

Therefore, information on the frequency spectrum intensity distribution of the input signal can be easily obtained by configuring a plurality of channels of the above-mentioned SAW elements each having a different center frequency connected in parallel.

8- FIG. 3 shows a configuration example of a narrowband interference suppression filter system formed by connecting n channels of SAW elements having the above-described structure in parallel. From now on, this narrowband interference suppression filter will be used as A I
SF (Adaptive Interference)
This will be called eSuppression Filter).

The part in FIG. 3 consisting of the input transducer group 17 and the second pn diode array group 20 is a part that monitors the intensity distribution of the input spectrum. The input/output transducers 17 and 18 function as a sorting filter that classifies input signals according to their frequencies, propagates them, and synthesizes them again.''

The first p on the SAW propagation path provided for each channel
An n-diode array group 19 controls the attenuation constant of the SAW of each channel.

The operation of the Al5F system of FIG. 3 is as follows. The input signal is converted into SAW by the input transducer group 17, and the bias shift amount of the second pn diode array group 20 is monitored and the bias voltage of the first pn diode for propagation control is adjusted by the bias control circuit 2. controlled by the engineer.

The function of this bias control circuit 21 is to amplify the bias shift amount of the second pn diode 20 according to the signal strength of each channel, and bias the pn diode 19 of the channel with a large shift amount in the opposite direction. be. Alternatively, in addition to simply amplifying, it has a function of setting a certain threshold value and turning on (forward bias) or OFF (reverse bias) the bias of the I-th pn diode 19 using a comparator.

As you can see from Figures 1 and 3, Al5 in Figure 3
The F system has the advantage of being able to be monolithically integrated on the -Si substrate, making it possible to achieve higher performance and smaller size of the system.

FIG. 4 explains the flow of signal processing in the Al5F system. (a) shows an input signal spectrum in which narrowband interference waves (B, C) are added to a wideband 5S-DS signal (A).

m to the channel number corresponding to the frequency of interference waves B and C.
is detected, and adapting to the environment, the filter characteristics of Al5F become characteristics in which a notch is formed in the m channel portion, as shown in (b). The spectrum of the output signal of Al5F having this characteristic becomes spectrum (c) in which the interference waves B and C are suppressed.

FIG. 5 shows an example of a system configuration in which the Al5F system shown in FIG. 3 is incorporated into the input stage of a receiving section of a DS-8S system. The Al5F system 30 is provided before the correlator, and the AGC (auto gain control) is installed before the correlator.
l) A circuit 31 is provided. In this system configuration example, the output of the Al5F system 30 is fed back and the gain control of the amplifier is performed by the AGC 31.

BPF32 is a bind pass filter. If an AGC circuit is installed without installing an Al5F system, if there is a high-power narrowband interference wave, the DS-8S communication system will have problems such as inability to communicate or increased error rate because the gain will be controlled by the interference signal itself. It happens. However, when the Al5F system 30 is provided, it becomes possible to control the gain according to the signal strength of the interference wave suppressed signal, that is, the spread spectrum signal itself, and the functionality of the DS-8S system is dramatically improved.

The sixth diode is a modification of the embodiment shown in FIG. 1, and corresponds to the second diode array 10.
A top electrode 6' is provided.

[Effects of the Invention] As explained above, according to the present invention, the following effects can be obtained as an Al5F system.

(1) The response time is extremely fast because the notch characteristics of the filter are controlled by diode bias control.

(2) Since the spectrum of the input signal is detected and the bias control of the diode is performed, the power required for the input signal can be reduced by high sensitivity detection.

(3) Adaptive suppression is possible without any limit to the number of narrowband high-level interference signals.

(4) The adaptive suppression system for interference waves can be configured monolithically, and the system can be simplified and downsized. Furthermore, the device productivity is also good.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 12- is a diagram showing the relationship between the voltage at one terminal of the input signal monitor and input power in the above embodiment, and FIG. 3 is a diagram showing the narrowband interference of the present invention. Block diagram showing an example of a system configuration of a filter for suppression, No. 4
5 is a block diagram showing a part of the receiving section of the DS-8S system using the system shown in FIG. 3, and FIG. 6 is an example of the embodiment shown in FIG. 1. It is a schematic diagram showing a modification of . 1...P(n) type cavity resistor SL single crystal substrate, 2...Silicon oxide film, 3...
...ZnO piezoelectric thin film, 4...Input transducer, 5...Output transducer, 6,6'...Gate electrode, 7.
......High concentration impurity region, 8...
...n+ (p+) impurity diffusion region (first PN diode array), 9...p"(n")
Impurity diffusion region, 10......n(p) impurity diffusion region (second PN diode array), 11...
......Resistor, 12...DC power supply, 13...Input signal monitor terminal, 14
......Bias control terminal.

Claims (2)

[Claims] (1) A laminate including a first conductivity type high-resistance silicon substrate, an insulating film, and a piezoelectric film, and an input transducer formed on the piezoelectric material to classify input signals into frequencies and generate a plurality of propagation paths. , an output transducer formed on the piezoelectric body and obtaining an output signal from a surface acoustic wave propagated on each propagation path; a group of gate electrodes formed on the piezoelectric body corresponding to each of the propagation paths; a first PN diode array group formed on the surface side of the first conductivity type silicon high resistance substrate in an area sandwiched between each input/output transducer; and for each input transducer, a second PN diode array group formed on the opposite side of each of the first diode array groups, and detection terminals each independently drawn out from the second PN diode array, A narrowband interference signal removal device comprising: bias application terminals each independently drawn out from the first PN diode array. (2) The narrowband interference signal removal device according to claim (1), further comprising a bias control circuit that controls a bias voltage applied to the bias application terminal.