A dual mode InGaP/GaAs heterojunction bipolar transistor (HBT) power amplifier (PA) using a parallel power-combining transformer (PCT) is presented herein. A low loss transformer is implemented on a printed circuit board (PCB) to improve the passive efficiency of a PCT. Dual-mode operation is applied to reduce the current consumption at a low power level. In the low-power (LP) mode, one of the individual amplifiers is turned off to reduce the current consumption. Additionally, a third-order intermodulation distortion (IMD3) cancellation method using a PCT combiner is proposed to improve linearity performance. Nonlinear IMD3 components from each amplifier cancel each other out through magnetic coupling in the secondary winding of the PCT. The implemented PA achieves a saturated output power of 33.8 dBm and a peak power-added efficiency (PAE) of 54.5% at 0.91 GHz with a 5-V power supply. An average output power of 25.2 dBm with an adjacent channel leakage ratio (ACLR) of −42 dBc is delivered when the PA is tested with an orthogonal frequency division multiplexing (OFDM) 64-quadrature amplitude modulated (64-QAM) signal with a bandwidth of 10 MHz and peak-to-average power ratio (PAPR) of 7.8 dB. When compared with the high-power (HP) mode operation, the LP mode operation could save 48% of the current consumption at an average output power of 10.4 dBm.
In this paper, the design of a compact broadband lumped-distributed balun, including impedance matching, is suggested. For the broadband impedance characteristic of the suggested balun design, the even-mode impedances of the balun were analyzed using the differential port impedance (Z in ). The proposed balun enables broadband impedance matching without an additional impedance-matching network, thereby reducing the circuit size and passive loss. The suggested balun was fabricated using FR4-based PCB and its performance was verified. The balun was designed to match a single-ended port impedance of 50 Ω and a Z in of 25 Ω. The fabricated balun has a −10-dB return loss from 550 to 950 MHz. Z in was measured to confirm impedance transformation and matching of the fabricated balun. The measured real value of impedance was 25±5 Ω and the imaginary value was 0±5 Ω from 640 to 870 MHz. The electrical length of the balun was reduced to 18°K
In this paper, a design methodology for a fully integrated impedance-transforming multi-winding 90° coupler is proposed. The operation of the proposed coupler was verified using measurement results. These couplers were fabricated using the WIN semiconductor InGaP/GaAs heterojunction bipolar transistor (HBT) process. To provide an impedance transformation, the proposed couplers were designed with 3, 4 and 5 turn coils for 50-, 75-, and 100-Ω impedance transformations, respectively. The center frequencies of each coupler were 5.5, 3.33, and 2.47 GHz. Two copper metal layers were combined together with a via to attain a high Q factor, and its improvement was analyzed. The measurement results show that the insertion losses of the proposed couplers are less than 0.37 dB and phase imbalances are less than 2.74°.
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