temperature. The respective constants ε′, ε′′, and tan(δ) are formulated in a general form via a non-linear regression and compared to existing data in literature.
This article presents a switched-mode transmitter architecture using a current mode class-D (CMCD) amplifier. To achieve high average efficiency for a modulated signal the envelope of the complex baseband signal is transformed into pulses such that the CMCD amplifier is operated either at its peak efficiency or completely switched off. The CMCD amplifier has been designed based on single-tone active harmonic load-pull measurements to achieve a power-added efficiency (PAE) of 61.5% with 25 W output power at 900 MHz using LDMOS FETs. Removing the losses of the demodulation filter and of the amplifier a 10% higher efficiency than in an ideal class-B amplifier can be obtained for burst-mode operation with a peak-to-average power ratio of 10 dB. V C 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE 20: 446-457, 2010.
We introduce a new technique for the design of an output combiner for Doherty power amplifier (DPA) and its effective exploitation for the development of a wideband laterally diffused metal oxide semiconductor (LDMOS) DPA. The design is enabled by a two-line impedance inverter for the DPA back-off operation, which is capable of 52% of fractional bandwidth. The technique is validated by the development of a DPA prototype for Ultra high frequency terrestrial digital video broadcast (DVB-T) applications, with optimized peak power and efficiency over 470–806 MHz. The prototype delivers between 40 and 53% of average efficiency across the band, at 49 dBm output power in average across the bandwidth, and supporting DVB-T signals with 8 MHz bandwidth and a peak-to-average power ratio of 10.5 dB. It achieves the target adjacent channel power ratio of −52 dBc at 750 MHz if digital pre-distortion is applied, and provides 47.8 dBm of output power with a drain efficiency of 44.3%.
This work presents the design of a current mode class-D (CMCD) amplifier using a measurement based approach. Because the CMCD amplifier is in fact a push-pull version of the inverted class-F amplifier the optimum load impedances for an inverted class-F single-ended operated LDMOS FETs have been determined using an active harmonic load-pull setup. The correct time domain waveforms for an inverted class-F amplifier were verified by measurements and simulations. Based on the harmonic load-pull measurements an experimental current mode class-D amplifier with 61.5% power-added efficiency (PAE) at 25 W output is demonstrated using LDMOS FETs at 900 MHz.
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