Cartesian loop transmitter and method of adjusting an output level of such transmitter
First Claim
1. A Cartesian loop transmitter having a forward path and a feedback path, each of these paths comprising an I-channel and a Q-channel, as well as an isolator eliminator, said transmitter comprising:
- a) a first low pass filter and a first wide band pass filter connected to said I-channel at LP2;
b) a second low pass filter and a second wide band pass filter connected to said Q-channel at LP2;
c) a first root mean square detector collecting signals from said first wide band pass filter;
and from said second wide band pass filter;
d) a second root mean square detector collecting signals from said first low pass filter and from said second low pass filter;
e) a first divider connected to said first and said second root mean square detectors to produce a first ratio using signals from said first and said second root mean square detectors; and
f) a means for comparing connected to said first divider, the means for comparing comparing the first ratio to a first threshold, the means for comparing providing a signal; and
g) a digital system connected to input attenuators on said I- and Q-channels and to the means for comparing, the digital system controlling an attenuation setting of the transmitter based on the signal from the means for comparing.
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Accused Products
Abstract
A Cartesian loop transmitter having isolator eliminator circuitry is presented. The isolator eliminator circuitry includes a set of low pass and wide band pass as well as narrow band pass filters for each of I- and Q-channels, root mean square detectors and dividers connected to a means for comparing. Signals from the means for comparing are received by a microprocessor which controls attenuation setting. The output level of the transmitter is adjusted by generating a small signal measuring an on-channel signal level and a small signal level and then calculating a ratio of the small signal to the on-channel signal. The attenuation setting is increased if the ratio exceeds a defined threshold.
69 Citations
19 Claims
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1. A Cartesian loop transmitter having a forward path and a feedback path, each of these paths comprising an I-channel and a Q-channel, as well as an isolator eliminator, said transmitter comprising:
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a) a first low pass filter and a first wide band pass filter connected to said I-channel at LP2; b) a second low pass filter and a second wide band pass filter connected to said Q-channel at LP2; c) a first root mean square detector collecting signals from said first wide band pass filter; and from said second wide band pass filter; d) a second root mean square detector collecting signals from said first low pass filter and from said second low pass filter; e) a first divider connected to said first and said second root mean square detectors to produce a first ratio using signals from said first and said second root mean square detectors; and f) a means for comparing connected to said first divider, the means for comparing comparing the first ratio to a first threshold, the means for comparing providing a signal; and g) a digital system connected to input attenuators on said I- and Q-channels and to the means for comparing, the digital system controlling an attenuation setting of the transmitter based on the signal from the means for comparing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of adjusting an output level of a Cartesian loop transmitter in a digital radio system, the method comprising the steps of:
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a) generating a small signal at a predefined frequency offset in relation to a transmission channel; b) applying a factory predefined attenuation setting for adjusting said output level if an attenuation setting for a previous slot is not available, or c) applying said attenuation setting obtained in previous slot for adjusting said output level in a current slot; d) measuring an on-channel baseband signal level at LP2; e) measuring a small signal level of said small signal at a predefined frequency offset at LP2; f) calculating a first ratio of said small signal level to said on-channel baseband signal level; and g) increasing an attenuation setting of an input signal if said first ratio is above a first threshold; and h) storing said attenuation setting of an input signal in a memory. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification