Claims
- 1. An apparatus for injecting an information-tagged attenuated signal into a communications receiver comprising:
- generating means for generating a signal:
- attenuating means operably coupled to said generating means, for attenuating said signal and thereby generating an attenuated signal;
- attenuation information producing means operably coupled to said attenuating means for producing a modulation signal containing information corresponding to the amount of attenuation imparted to said signal by said attenuation means; and
- modulating means operably coupled to said generating means and to said attenuation information producing means for modulating said signal with said modulation signal.
- 2. An apparatus of claim 1 in which said generating means generates a radio frequency signal.
- 3. An apparatus of claim 1 in which said attenuating means includes a erasable programmable read-only memory (EPROM) containing an attenuation value stored therein corresponding to the amount of attenuation imparted to said signal by said attenuating means.
- 4. An apparatus of claim 3 in which said attenuation information producing means includes an EPROM containing information stored therein corresponding to the attenuation value stored within said EPROM containing said attenuation value.
- 5. An apparatus for injecting an information-tagged attenuated test signal into a communications receiver comprising:
- generating means for generating a signal;
- attenuation control means for providing an attenuation control signal;
- attenuating means operably coupled to said generating means and to said attenuation control means, for attenuating said generated signal with said attenuation control signal thereby generating an attenuated signal;
- information signal producing means operably coupled to said attenuation control means, for producing a modulation signal corresponding to the degree of attenuation provided by said attenuation control signal; and
- modulating means operably coupled to said information signal producing means and to said generating means, for modulating said generated signal with said modulation signal.
- 6. An apparatus of claim 5 in which said generating means generates a radio frequency signal.
- 7. An apparatus of claim 6 in which said attenuation control means includes an erasable programmable read-only memory (EPROM) containing an attenuation value stored therein corresponding to the amount of attenuation imparted to said signal by said attenuation means.
- 8. An apparatus of claim 7 in which said information signal producing means includes an EPROM containing information stored therein corresponding to the attenuation value stored within said EPROM containing said attenuation value.
- 9. An apparatus of claim 8 in which said attenuation value is one of a plurality of attenuation values and in which said information is one of a plurality of information, said information pertaining individually to the attenuation values stored within said EPROM containing said plurality of attenuation values.
- 10. An apparatus for injecting time-variable, information-tagged attenuated test signals into a communications receiver comprising:
- generating means for generating a signal;
- attenuation control signal means for providing time-variable attenuation control signals;
- attenuating means operably coupled to said generating means and to said attenuation control signal means for attenuating said generated signal according to said time-variable attenuation control signals;
- attenuation information signal producing means operably coupled to said attenuation control signal means for producing information modulation signals corresponding to the degree of attenuation provided by said attenuation control signals;
- modulation means operably coupled to said attenuation information signal producing means and to said generating means, for modulating said generated signal with said information modulation signals; and
- timing means operably coupled to said attenuation control signal means and to said attenuation information signal producing means, for assuring a desired timing therebetween.
- 11. The apparatus of claim 10 in which said generated signal is a radio frequency signal.
- 12. The apparatus of claim 11 in which said means for providing said time-variable attenuation control signals includes a first erasable programmable read-only memory (EPROM), said first EPROM being programmed with preselected attenuation control values and preselected attenuation time periods, each of said preselected attenuation control values having a corresponding preselected attenuation time period.
- 13. The apparatus of claim 12 in which said first EPROM is operably coupled to a latch circuit, said first EPROM and said latch circuit being operably coupled to a counter, and said counter being operably coupled to said timing means, so that a programmed preselected attenuation time period output from said first EPROM is counted in said counter and so that a programmed preselected attenuation control value output from said first EPROM is loaded into said latch for said programmed preselected time period, said counter being operably coupled to a memory address circuit and said memory address circuit being operably coupled to said first EPROM to initialize a succession of said programmed preselected attenuation control values and said programmed preselected attenuation time periods to be output from said first EPROM.
- 14. The apparatus of claim 13 in which said attenuation information signal producing means includes a second EPROM containing information stored therein corresponding to the attenuation value stored within said first EPROM.
- 15. The apparatus of claim 14 in which said second EPROM is operably coupled to a second latch circuit, said second latch circuit for addressing individual messages of information within said second EPROM, said second EPROM being operably coupled to a second counter for counting through said individual messages, said second counter being operably coupled to said timing means to assure a desired timing relationship therebetween, said second latch circuit receiving said attenuation values from said first EPROM for said attenuation time periods and addressing said second EPROM thereupon so that modulated signals containing information stored within said second EPROM and corresponding to said attenuation values stored within said first EPROM is output from said second EPROM to be modulated with said signal.
- 16. The apparatus of claim 15 in which said modulated signals are input into a parallel-to-serial converter, said parallel-to-serial converter being operably coupled to said timing means for assuring a desired rate of input into said parallel-to-digital converter, and to a rate generator, also operably coupled to said timing means, for selectively adjusting the output rate of said parallel-to-serial converter.
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purpose without the payment of any royalties thereon or therefor.
1. Field of the invention
This invention pertains broadly to the field of telecommunications. More particularly, the invention pertains to telecommunication receivers. In still greater particularity, the invention relates to a receiver test apparatus for accurately determining receiver response. In yet still greater particularity, the invention relates to a telecommunications receiver test apparatus for injecting programmed attenuated test signals containing test identification messages.
2. Description of the prior art
The response of a telecommunications receiver is crucial to the reception of a clear and concise transmitted message. However, crowded transmission channels and the abundance of ambient noise have made clear and concise reception a challenge for even the most skilled telecommunications engineers.
As a consequence of this challenge, receiving equipment is thoroughly checked to determine how close receiver output is to transmission input.
In the past, a receiver test device permitted an operator to inject a receiver with transmission signals of known attenuation levels. The operator of the receiver under test would then compare a strip chart recording of the receiver response with the known inputted test signals. Changes in received attenuated test signals from one level to another were predicted upon the operator noting the lapsed test transmission time and comparing this time with the test signal programmed to take place at that point in the test transmission sequence.
In circumstances in which the receiver under test was injected with a large sequence of test values, it became increasingly more difficult for operators to determine where in the test sequence response anomalies occurred. This difficulty in turn made prolonged reproducible tests at a desired point in the test sequence extremely difficult, so that a determination as to whether the response error was caused by a receiver fluke or by a receiver malfunction could not easily be made.
The invention substantially overcomes the above described deficiencies by providing an attenuated test signal that includes a contemporaneous message corresponding to the amount of attenuation imparted to the test signal. The simultaneous injection of the message with the test signal makes it easy for an operator of a system under test to determine at what attenuated test level unexpected receiver responses occur. This invention is an improvement of the programmable time varying attenuator patented by the inventors Paul A. Singer and James L. Conrath in U.S. Pat. No. 4,625,332, incorporated by reference herein.
A first embodiment of the invention includes a programmable attenuator operably coupled to a test message injector and a modulator for modulating a message with a generated carrier signal. The programmable attenuator provides a sequence of programed attenuation test signals each of which are injected for preselected time periods. The attenuator is coupled to the test message injector to trigger an attenuation message to be injected with the attenuated signal. Synchronization of the attenuated signal with the attenuation message is provided by a mutually linked timing standard.
A second embodiment includes a continuous wave noise generator, the output of which is first selectively attenuated in the above referred to programmable attenuator and that is then combined with an attenuation message in a channel simulator. The combined signal is output from the channel simulator to be injected into the receiver under test. This embodiment closely approaches typical ambient reception environments as the noise generator and channel simulator provide expected receiver background disturbances.
Each of these embodiments of the invention includes an attenuation message function to facilitate the testing of the telecommunications receiver.
It is an object of the invention to provide an improved telecommunications receiver test apparatus.
Another object of the invention is to provide an improved receiver test apparatus that injects a receiver under test with a test signal that includes a test identification message.
Yet another object of the invention is to provide an improved telecommunications receiver test apparatus that injects a receiver under test with an attenuated test signal that includes a message corresponding to the amount of attenuation imparted to the test signal.
Other objects, advantages and new features of the invention will become apparent from the following detailed description of the invention when considered in conjuction with the accompanied drawings.
US Referenced Citations (8)
Patent Grant
4972511
