Front end filter circuitry for a dual band GSM/DCS cellular phone
AssigneeConexant Systems, Inc.
InventorJohn R. Rowland, Jr.
Life of this patent
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Abstract
A front end circuit for an RF dual band GSM/DCS phone includes a first channel including an elliptical high-pass filter, a first SAW filter, and a low noise amplifier and a second channel including a second SAW filter and a second low noise amplifier. The output of each channel is alternately switchable to a single-side band mixer circuit. This front end circuit arrangement provides significantly reduced cost and part count over other approaches.
Claims25
A radio frequency circuit comprising:
- a high-pass filter receiving an RF signal;
- a first SAW filter having an input connected to the high-pass filter;
- a first amplifier connected to the output of the first SAW filter;
- a second SAW filter receiving an RF signal;
- a second amplifier connected to the output of the second SAW filter;
- a combiner for combining the outputs of the first and second amplifier to form an output signal;
- and
- a single side band mixer having an input connected to the combiner to receive the output signal.
A front end radio frequency receiver comprising:
- a high-pass filter;
- a first SAW filter having an input connected to the high-pass filter;
- and
- a mixer having an input connected to the output of the first SAW filter, wherein the mixer suppresses a frequency component consisting of a local oscillator frequency minus an IF frequency, and the high-pass filter provides compensation for insufficient side band suppression by the mixer.
A method for down-converting a dual band radio frequency (RF) signal comprising the steps of:
- filtering a first RF signal with a high-pass filter and a first SAW filter;
- filtering a second RF signal with a second SAW filter;
- amplifying the first and second RF signal;
- combining the first and second RF signal to form an output signal;
- and
- mixing the output signal and a local oscillator signal with a single-side band mixer.
A method for down-converting a dual band radio frequency (RF) signal in a DCS frequency channel comprising the steps of:
- filtering an RF signal with a high-pass filter and a first SAW filter;
- providing compensation for insufficient side band suppression in the RF signal;
- and
- mixing the RF signal and a local oscillator signal with a single-side band mixer, wherein the mixing step further comprises the step of suppressing a frequency component consisting of a local oscillator frequency minus an IF frequency.
Dependencies are inferred from the claim text.