Wideband direct DCO modulator with in-band compensation

摘要

A Direct VCO (DCO) modulation apparatus and method that provides a wideband modulated signal output. The wideband response is obtained via signal processing to counteract a high-pass frequency characteristic as seen from the VCO modulation input. That is, low frequency components of data signals are compensated before being applied to a VCO input. The high-pass characteristic in combination with the compensated signal provides a relatively flat, wideband frequency response of the DCO modulator.

主权项

1. An apparatus comprising:
a phase locked loop (PLL) having a VCO-output high-pass characteristic, the PLL comprising:
a voltage controlled oscillator (VCO) having a PLL VCO control input and a modulation VCO control input; and,a phase locked loop controller coupled to the PLL VCO control input and configured to output a PLL control signal to the PLL VCO control input; a signal phase generator configured to generate a phase signal of a desired information-modulated transmit signal; a compensation filter configured to generate a compensated phase signal by increasing low-frequency components of the phase signal to compensate for the VCO-output high-pass characteristic and the VCO gain characteristic; a phase derivative generator having an input coupled to the compensation filter, the phase derivative generator configured to receive the compensated phase signal and to convert the compensated phase signal to a compensated phase derivative modulation signal, and having a modulation control output coupled to the modulation VCO control input for providing the compensated phase derivative modulation signal to the VCO.