Bulk Acoustic Wave Duplexers Research Articles

Switchable and Tunable BAW Duplexer Based on Ferroelectric Material.

A switchable and tunable bulk acoustic wave (BAW) duplexer for RF applications is presented in this paper. The fabricated BAW duplexer was built on sapphire substrate using solidly mounted resonators. A metal-organic solution deposition technique was used to form resonators with barium strontium titanate (BST) thin film and six layers of silicon dioxide and tantalum oxide as Bragg reflector. By applying dc bias, the BST thin film shows an electrostrictive effect, and the two filter paths of the BAW duplexer switch to a bandpass response with center frequencies at 4.635 and 4.878 GHz, showing a bandwidth of 119 and 154 MHz for the transmitting (Tx) and receiving (Rx) filters, respectively. Further, the BAW duplexer was simulated using the circuit, Butterworth-van-Dyke, and electromagnetic models. The simulated results are in agreement with the measurements and show the response of bandpass filters at center frequencies of 4.633 and 4.876 GHz for Tx and Rx, respectively.

A complete UMTS transmitter using BAW filters and duplexer: A 90-nm CMOS digital RF signal generator and a 0.25-μm BiCMOS power amplifier

A complete UMTS transmitter is proposed. It is composed of a radiofrequency (RF) signal generator, a power stage, and a bulk acoustic wave (BAW) duplexer. The 90-nm CMOS digital RF signal generator is based on a third-order delta-sigma modulator using innovative design techniques to increase work frequency and a BAW filter to get rid of out-of-band quantization noise. The filter exhibits very high rejection, 3 dB of insertion losses at 1.95 GHz for a 3% fractional bandwidth. The 0.25-μm BiCMOS power stage feeds a BAW duplexer that allows to share a common between W-CDMA emission and reception. This 4 × 4 mm2 duplexer, built with flip-chipped BAW on glass substrate, ensures good isolation. The full transmitter measurements show the compliance with respect to spurious emissions in the different frequency bands and an EVM measurement at the state of the art (<5%). © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

Theoretical considerations on influence of circuit impedance on IMD2 measurement of radio-frequency bulk acoustic wave duplexers

This paper discusses theoretically how the impedance of peripheral circuits influences the measurement of second-order inter-modulation distortion (IMD2) generated in RF BAW duplexers. First, IMD2 properties of RF BAW duplexers are expressed by a rank three tensor. Then, the tensor expression is used to evaluate how the port termination affects the IMD2 output. It is shown that variation of IMD2 output is caused mainly by five mechanisms: 1) variation of the transmit (Tx) signal intensity caused by impedance mismatching at the Tx port; 2) variation of the jammer signal intensity caused by impedance mismatching at the antenna (ANT) port; 3) variation of detector read caused by impedance mismatching at the receive (Rx) port; 4) reentry of the IMD2 signal to the ANT port caused by impedance mismatching at the ANT port; and 5) reentry of the Tx signal to the ANT port caused by impedance mismatching at the ANT port. Because input impedance of the ANT port is usually not defined for jammer signals, a large attenuator must be added to the ANT port to suppress the impedance mismatching. This result is consistent with experiments reported previously.