Adjacent channel selectivity signal generator system
AssigneeHewlett-Packard Company
InventorsWilliam J. Crilly, Jr., Earl C. Herleikson
Life of this patent
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Abstract
In an adjacent channel measurement system, a desired channel signal and an adjacent channel signal are generated using a single signal generator. The output from this generator is modulated with a signal from an offset oscillator to produce a carrier and a sideband signal, one in each channel. The ratio of the carrier amplitude to the sideband amplitude is set by the system's modulation index, which is controlled by an audio attenuator on the output of the offset oscillator.
Claims33
In a method of measuring or compliance testing for adjacent channel selectivity in a radio receiver including the steps:
- tuning the radio receiver to a first RF frequency;
- providing the receiver a first RF signal at said first RF frequency;
- providing the receiver a second RF signal at a second RF frequency adjacent the first RF frequency;
- relating the amplitude of the first RF signal to the second RF signal;
- and
- measuring the receiver signal-to-noise ratio;
- an improvement comprising generating the first and second RF signal with a single signal generator by generating a signal at one of said first or second RF frequencies and modulating said signal with a subcarrier to produce a sideband at the other of said first or second RF frequencies.
An apparatus useful in measuring adjacent channel selectivity of a radio receiver under test comprising:
- an RF signal generator for producing an RF signal;
- an offset signal generator for producing an offset signal;
- first modulation means for modulating the RF signal with the offset signal to produce first and second RF signals, one of said first or second RF signals being a sideband of the other;
- means for generating first and second different baseband modulation signals;
- second modulation means for modulating the first RF signal with the first baseband modulation signal;
- third modulation means for modulating the second RF signal with the second baseband modulation signal;
- and
- means for providing a single composite signal, comprising both the first RF signal modulated with the first baseband modulation signal, and the second RF signal modulated with the second baseband modulation signal, to the radio receiver under test.
A method of generating first and second RF signals used in measuring adjacent channel selectivity of a receiver under test, the method comprising the steps:
- generating first and second baseband modulation signals;
- summing said baseband modulation signals to produce a summed modulation signal;
- producing an offset signal;
- frequency modulating said offset signal with the summed modulation signal to yield a subcarrier signal;
- controlling the level of the subcarrier signal;
- producing an RF signal;
- and
- amplitude modulating said RF signal with the subcarrier signal and additionally modulating said RF signal with both the subcarrier signal and the second baseband modulation signal using a form of modulation other than amplitude modulation, so as to produce a composite RF signal, said composite signal including said first and second RF signals.
An apparatus useful in measuring adjacent channel selectivity of a radio receiver under test comprising:
- baseband modulation signal means for generating first and second baseband modulation signals;
- summing means for summing the baseband modulation signals to produce a summed modulation signal;
- offset oscillator means for producing an offset signal;
- first modulation means for frequency modulating said offset signal with the summed modulation signal to yield a subcarrier signal;
- level control means for controlling the level of the subcarrier signal;
- RF oscillator means for producing an RF signal;
- and
- second modulation means for amplitude modulating the RF signal with the subcarrier signal and additionally modulating the RF signal with both the subcarrier signal and the second baseband modulation signal using a form of modulation other than amplitude modulation, so as to produce a composite RF signal.
A method of providing first and second RF signals to a radio receiver undergoing an adjacent channel selectivity measurement test, the method comprising the steps:
- generating the first RF signal;
- generating an offset signal;
- modulating said first RF signal with the offset signal using both amplitude and narrow band frequency modulation with equal modulation indices of m and .beta., respectively, so a sideband produced by the amplitude modulation of the first RF signal cancels a sideband produced by the frequency modulation of the first RF signal, leaving another sideband produced by each type of modulation to sum constructively and serve as the second RF signal;
- and
- providing said modulated first RF signal and said second RF signal to a radio receiver under test.
Dependencies are inferred from the claim text.