Disclosed herein are devices and methods to reduce unwanted CIM3 emission in a wireless communication device, such that the transmit (TX) power level applied in a RU can be increased without exceeding a regulatory emission requirement. In some aspects, unwanted emission may be reduced by shifting or changing local oscillator (LO) frequencies during TX operation. Some embodiments are directed to a fast-locking PLL with adjustable bandwidth that can be controlled to increase the PLL bandwidth during the RX to TX transition to provide a fast locking to a new LO frequency. Some aspects are directed to configuring an LO frequency shift amount for different RUs when multiple RUs are allocated within a frequency band.

Apparatus and methods for adjusting a gain of an electronic oscillator, such as a voltage-controlled oscillator (VCO), are disclosed. In one aspect, an apparatus for compensating for VCO gain variations includes a charge pump controller. The charge pump controller can be configured to select a VCO gain model based on a comparison of a VCO gain indicator and a threshold value stored in a memory, obtain VCO gain model parameters from the memory corresponding to the selected VCO gain model, and compute a charge pump current control value using the VCO gain model parameters. The charge pump current control value can be used to compensate for VCO gain variations.

Disclosed herein are devices and methods to reduce unwanted CIMS emission in a wireless communication device, such that the transmit (TX) power level applied in a RU can be increased without exceeding a regulatory emission requirement. In some aspects, unwanted emission may be reduced by shifting or changing local oscillator (LO) frequencies during TX operation. Some embodiments are directed to a fast-locking PLL with adjustable bandwidth that can be controlled to increase the PLL bandwidth during the RX to TX transition to provide a fast locking to a new LO frequency. Some aspects are directed to configuring an LO frequency shift amount for different RUs when multiple RUs are allocated within a frequency band.

A fast-locking phase-locked loop (PLL) and an associated fast-locking method thereof are provided. The fast-locking PLL may include a gear-shifting loop filter, which is configured to have a dynamic bandwidth. The gear-shifting loop filter may include a resistor set and a capacitor set coupled to the resistor set, where the resistor set is configured to have a dynamic resistance, and the capacitor set is configured to have a dynamic capacitance. More particularly, the dynamic resistance is switched from a first resistance to a second resistance and the dynamic capacitance is switched from a first capacitance to a second capacitance, to make the dynamic bandwidth be switched from a first bandwidth to a second bandwidth.

A bandwidth adjustment method includes obtaining an upper bandwidth limit and a lower bandwidth limit according to an initial upper bandwidth limit and an initial lower bandwidth limit, obtaining an optimum bandwidth according to the upper bandwidth limit and the lower bandwidth limit, and adjusting the initial upper bandwidth limit and the initial lower and width limit according to the optimum bandwidth.