Measuring adjacent channel power
First Claim
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1. A method for measuring adjacent channel power of a signal source spectrum including frequency shifting the spectrum such that the center frequency of the adjacent channel band is converted to DC;
- filtering the frequency shifted spectrum with a low pass filter; and
measuring the power output from the low pass filter.
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Abstract
A signal source from a transmitter is down-converted by being mixed with a locally generated signal so that a desired adjacent channel band is converted to base band and the adjacent channel power measured after filtering by a low pass filter. To eliminate the notch in the filter characteristics that occurs when the power is measured by a.c coupled means, the locally generated signal is modulated or swept around the center of the adjacent channel band.
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Citations
20 Claims
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1. A method for measuring adjacent channel power of a signal source spectrum including frequency shifting the spectrum such that the center frequency of the adjacent channel band is converted to DC;
- filtering the frequency shifted spectrum with a low pass filter; and
measuring the power output from the low pass filter.
- filtering the frequency shifted spectrum with a low pass filter; and
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2. A method for measuring adjacent channel power of a signal source including the steps of mixing an input signal with a local oscillator signal having angle modulation and which is nominally centered on the desired adjacent channel centre frequency;
- filtering the frequency shifted spectrum with a low pass filter; and
measuring the power output from the low pass filter by means of an a.c. coupled meter. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11)
- filtering the frequency shifted spectrum with a low pass filter; and
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12. Apparatus for measuring adjacent channel power of a signal source comprising:
- signal input means;
signal generating means for generating an angle modulated signal nominally centered on the desired adjacent channel centre frequency;
means for mixing the signal input and the angle modulated signal such that the adjacent channel band is down converted to base band;
a low pass filter for filtering the mixing product; and
a.c. coupled means for measuring the power output from the low pass filter. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
- signal input means;
Specification