3G radio
OwnerSimon Atkinson, Aidan Cahalane +1inventors
InventorsSimon Atkinson, Aidan Cahalane, Paul Ferguson JR.
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Abstract
In a UMTS homodyne (direct conversion) receiver the local oscillator may break through as an “on channel” signal. In order to remove this the receiver includes controllable DC offset generators and variable gain amplifiers. These are in series with a high pass filter. Adjustments in the gain or offset can give rise to transients within the filter which effectively blind the receiver until such time as the transients have decayed within the filter. This blind time can be reduced by increasing the bandwidth of the filter during such a transient.
Claims18
A homodyne receiver comprising a high pass filter having a variable time constant and a variable gain amplifier, the filter and amplifier being up-stream of an analogue to digital converter, wherein when at least one of a gain adjustment or offset correction is made the time constant of the high pass filter is reduced for a predetermined period.
A homodyne receiver as claimed in 1, in which during the period in which the time constant is reduced, the bandwidth of the filter is substantially ten times or more greater than a working bandwidth of the filter.
A homodyne receiver comprising signal conditioning means upstream of an analog to digital converter and a high pass filter having a variable time constant, wherein when the signal conditioning means is operated to cause a variation to be made to the signal supplied to the analog to digital converter, the time constant of the filter is set to a reduced value.
Dependencies are inferred from the claim text.