Third-order Intermodulation Distortion Cancellation Research Articles

Broadband Tunable Third-Order IMD Cancellation Using Left-Handed Transmission-Line-Based Phase Shifter

We demonstrate a broadband tunable third-order intermodulation distortion (IMD) cancellation architecture using a left-handed transmission line (LHTL)-based phase shifter for a feedforward amplifier. The fabricated circuit reduces the third-order IMD of the main amplifier up to 17 dB after adjusting for any frequencies between 1.5 and 2.4 GHz when the frequency difference between the two tones is 2 MHz. In addition, the circuit maintains a spurious-free dynamic range that is greater than 55 dBc at the output. This effective broadband third-order IMD cancellation method is possible because of the broadband and linearly phase-tunable characteristics of the LHTL-based phase shifter.

A Wideband Digital TV Receiver Front-End With Noise and Distortion Cancellation

A low noise and highly linear wideband CMOS receiver front-end for digital TV receivers is proposed. The proposed RF front-end comprises a wideband noise canceling common gate low noise amplifier (LNA) with a capacitively cross-coupled current source, a highly linear up-conversion micromixer with third-order intermodulation distortion cancellation, and a highly linear surface acoustic wave (SAW) driver with enhanced loop gain. The RF front-end was fabricated using a 0.13 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu$</tex> </formula> m CMOS process and it draws 27 mA from a 1.5 V supply voltage. It achieves a voltage gain of 23 dB, a noise figure of less than 4 dB, an IIP3 of greater than <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${-}$</tex> </formula> 6.5 dBm, and an IIP2 of greater than 28 dBm across the entire input band from 54 MHz to 882 MHz.

An analog compensation method for asymmetric IMD characteristics of power amplifier

The modulation frequency affects the asymmetric intermodulation distortion (IMD) products of a RF power amplifier. This effect reduces IMD cancellation performance of power amplifiers in connection with predistortion linearization. A phase extraction method to determine phase difference between upper and lower third-order IMD products and a phase compensation circuit using an envelope injection technique is proposed. The experimental results demonstrate a significant improvement in the third-order IMD cancellation performance.

A novel generalized low-frequency signal-injection method for multistage amplifier linearization

This paper presents for the first time the investigation of multistage amplifier linearization based on the generalized low-frequency signal-injection technique. Difference-frequency signals, generated by a predistortion circuit, are fed to the biasing circuitry of a multistage amplifier for third-order intermodulation-distortion cancellation. The reason that two-stage injection shows better linearization performance than the single-stage injection case is analytically derived. Furthermore, issues on the optimum operating condition, gain error, and bandwidth limitation are also addressed. For demonstration, the measured performance of an experimental system using both the two-tone and digitally modulated test signals are shown.

A novel frequency-independent third-order intermodulation distortion cancellation technique for BJT amplifiers

Second-harmonic control is implemented in a balanced common-emitter configuration to facilitate frequency-independent third-order intermodulation distortion cancellation. Moreover, this circuit configuration facilitates a simultaneous match for either power and linearity or noise and linearity. Experiments demonstrated an improvement of over 15 dB in the output third-order intercept point while maintaining freedom in the choice of load and source impedance.