Receiver with intermediate frequency error correction
AssigneeMaxim Integrated Products, Inc.
InventorsTheron L. Jones, Andrew Zocher, Luiz Antonio Razera, Jr., Lawrence Rankin Burgess
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Abstract
A receiver having an intermediate frequency error correction circuit includes a mixer having a source input, a local oscillator input, and an IF output, an adjustable frequency local oscillator having an output coupled to the local oscillator input of the mixer, an IF filter having an input coupled to the IF output of the mixer and an IF filtered output, where the IF filter has an IF filter frequency response, and control circuitry coupled to the local oscillator such that the frequency of the local oscillator can be varied to at least: partially correct an IF frequency error.
Claims12
A receiver having an intermediate frequency error correction circuit comprising:
- a mixer having a source input, a local oscillator input, and an IF output,
- an adjustable frequency local oscillator having an output coupled to the local oscillator input of the mixer;
- an IF filter having an input coupled to the IF output of the mixer and an IF filtered output, where the IF filter has an IF filter frequency response;
- control circuitry coupled to the local oscillator such that the frequency of the local oscillator can be varied to at least partially correct an IF frequency error,
- said control circuitry including a demodulator coupled to the output of the IF filter, an averaging circuit coupled to an output of the demodulator, an ADC coupled to an output of the averaging circuit, and a digital controller coupled to an output of the ADC;
- and
- a limiting amplifier coupled between the IF filter and the demodulator.
A method to calibrate an IF stage comprising:
- demodulating an IF signal in an FSK demodulator comprising a PLL of an IF stage to develop a demodulated output signal;
- developing a center signal related to said demodulated output signal which represents a center frequency of the demodulated output signal;
- developing a digital center value corresponding to the center signal;
- and
- changing a frequency derived from a local oscillator based upon a comparison between the center value to a calibration value;
- wherein said center signal is derived by a threshold generator.
Dependencies are inferred from the claim text.