Hao-Shun Yang

A Miniaturized 3 dB Branch-Line Hybrid Coupler With Harmonics Suppression

This letter presents a miniaturized 3 dB branch-line hybrid coupler with second harmonic suppression using high-impedance transmission lines and interdigitated shunt capacitors. By using the interdigitated capacitors shunt with the transmission lines, further minimization of the 3 dB branch-line hybrid coupler can be achieved compared with previously reported techniques. The design of the interdigitated shunt capacitors requires concurrent optimization of the capacitance to the ground and the edge-coupling interdigitated capacitance between the ports. For validation, a miniaturized 3 dB branch-line hybrid coupler at 836.5 MHz was designed and implemented. The proposed 3 dB branch-line hybrid coupler achieved a compact size of 27.75 mm × 25.7 mm, or equivalently 0.077λo×0.072λo, where λo is the free-space wavelength. Moreover, the coupler can suppress second harmonic components by 20 dB while maintaining similar measured performance compared to the conventional branch-line hybrid coupler.

A Polar-Transmitter Architecture Using Multiphase Pulsewidth Modulation

This paper presents a transmitter architecture based on a pulse-modulated polar transmitter using multiphase pulsewidth modulation. The modulation to the radio-frequency input signal, instead of conventional drain modulation, significantly reduces the circuit complexity, while the multiphase modulation technique reduces the out-of-band emissions. An 836.5-MHz four-phase prototype transmitter using four class-C power amplifiers in parallel was constructed. Using the transmitter, single-phase, two-phase, and four-phase pulsewidth modulated signals were tested to verify the benefits of using the proposed multiphase architecture. Using a CDMA2000 1X signal, 46.8% efficiency at a 29-dBm output power level was measured while passing the spectral-mask requirements without using any kind of digital predistortion or calibration.

A Multi-Level Pulse Modulated Polar Transmitter Using Digital Pulse-Width Modulation

This letter presents a multi-level pulse modulated polar transmitter architecture. Compared to a conventional gate-modulated envelope elimination and restoration transmitter, the use of the proposed technique is capable of reducing the in-band quantization noise level. Moreover, the proposed technique can increase the pulse-width modulation sampling frequency by relaxing its resolution requirement, which eases the filtering requirement at the output. A prototype transmitter system is constructed using commercially available components. Using a CDMA2000 1X signal at 836.5 MHz, it achieved over 40% power-added efficiency at 24.5 dBm output power level while passing the adjacent and alternate channel power ratios for the CDMA2000 standard.

A Polar Transmitter Using Interleaving Pulse Modulation for Multimode Handsets

This paper presents a highly efficient polar transmitter using interleaving pulse modulation for multiple communication standards. Using the proposed interleaving pulse modulation technique, a polar transmitter can suppress the odd-order output spurs deeply with a feasible value of essential sampling frequency and keep the residual spurs from falling into the receive bands. To validate the proposed technique, a prototype polar transmitter was constructed and evaluated. Using global system for mobile communications, enhanced data rates for GSM evolution, and wideband code division multiple access (WCDMA) signals at 836.5 MHz, the polar transmitter achieved 68%, 45.5%, and 41.2% power-added efficiency at output power levels of 28, 26, and 25 dBm, respectively. The measurement results were able to pass the spectral requirements defined by the respective standards without the use of any pre-distortion or calibration techniques. Moreover, the polar transmitter was able to achieve an output dynamic range of 80 dB required by the WCDMA standard.

A Technique for Implementing Wide Dynamic-Range Polar Transmitters

This paper presents a technique for implementing wide dynamic-range polar transmitters based on the envelope elimination and restoration technique. The fast-varying instantaneous output power level is controlled by a switch that modulates the input signal of the power amplifier (PA), whereas the slow-varying average power level is controlled by changing the dc voltage of the drain of the PA. A cellular band prototype transmitter system is constructed using commercially available components. Using a CDMA2000 1× signal with 4.5-dB peak-to-average power ratio at 836.5 MHz, the prototype transmitter achieved a dynamic range of over 80 dB while passing the adjacent and alternate channel power ratios for the CDMA2000 standard without the use of digital pre-distortion or calibration.

A Highly Efficient LTE Pulse-Modulated Polar Transmitter Using Wideband Power Recycling

This paper presents a wideband power recycling technique for pulse-modulated polar transmitters (PMPTs). The technique allows unwanted out-of-band modulation spurs in PMPTs to be rectified and recovered back to the power supply for efficiency improvement. By configuring the power amplifiers as a balanced amplifier with dual-phase digital pulse-width modulation, the odd modulation spurs can be extracted directly from the isolation port of the output-combining quadrature coupler. Using the proposed architecture, the prototype transmitter achieved 59.1% drain efficiency at an output channel power of 26.2 dBm using a 10-MHz bandwidth long-term evolution 16-quadrature amplitude modulation test signal at 836.5 MHz. After output signal restoration by a surface-acoustic-wave filter, an output power level of 24.8 dBm and 42.8% drain efficiency were achieved while passing the spectral and receive-band-noise requirements without using any digital pre-distortion techniques.

A Wideband Pulse-Modulated Polar Transmitter Using Envelope Correction for LTE Applications

The pulse-modulated polar transmitter (PMPT) uses the envelope information to pulse modulate the phase information to implement a highly linear and highly efficient polar transmitter. The bandwidth of the PMPT is primarily determined by the pulsewidth modulation sampling frequency of the envelope information. For wide bandwidth applications such as long-term evolution (LTE), finite rise and fall times of the RF pulses distort the envelope information. In this paper, the nonideal RF pulses are analyzed and an envelope correction method is proposed to reduce the distortion in wide bandwidth applications using the PMPT architecture. For validation, a cellular-band prototype transmitter system was constructed using commercially available components. Using a 20-MHz bandwidth 16-QAM LTE signal at 836.5 MHz, the prototype transmitter achieved an output power of 22.7 dBm and drain efficiency of 33% while passing the spectral requirements of the LTE standard.

A pulse modulated polar transmitter for CDMA handsets

This paper presents a pulse modulated polar transmitter with the designed class-E power amplifiers for CDMA handsets. Compared to the conventional drain/collector-modulated envelope elimination and restoration transmitter, the presented implementation is capable of reducing circuit complexity and making the envelope and RF phase signals easily synchronized. A prototype transmitter system is constructed using commercially available components. Measuring using a CDMA IS-95 signal at 900 MHz, it achieves 49.3% efficiency at 26.6-dBm output power level while passing the adjacent and alternate channel power ratio requirements without using any pre-distortion or calibration. Moreover, the polar transmitter achieves more than 20 dB of output dynamic range.

A 1.2-V 90-nm Fully Integrated Compact CMOS Linear Power Amplifier Using the Coupled L-Shape Concentric Vortical Transformer

This paper presents a 90-nm fully integrated CMOS linear power amplifier (PA) using a coupled L-shape concentric vortical transformer (CL-CVT) for the fourth-generation long-term evolution (LTE) communication standard. Using the proposed output combining CL-CVT architecture, the outer diameter required by the power combiner is reduced by 66% compared to the distributed active transformer with similar performance. Moreover, the PA is able to efficiently combine four push-pull output stages and achieve nearly constant power over several LTE bands with a total chip area less than 1 mm2. With a 1.2-V supply voltage, the PA delivers 27.3-dBm maximum output power with a peak drain efficiency of 47% at 2.4 GHz. Using a 20-MHz LTE 16-QAM test signal, the PA achieves 24.6% power-added efficiency at an output power level of 22 dBm and passes the spectral requirements defined by the LTE standard without using any pre-distortion or calibration techniques.

Linearity Enhanced Wide-Bandwidth Pulse-Modulated Polar Transmitters for LTE Femtocell Applications

The pulse-modulated polar transmitter (PMPT) uses envelope information to pulse modulate phase information to implement highly linear and highly efficient polar transmitters. Previous implementations of the PMPT successfully achieved bandwidths up to 5 MHz. However, as the bandwidth of the signal increases, nonidealities of the PMPT limit the performance of this architecture. The nonidealities are predominantly aliasing from pulsewidth modulation (PWM) and distortions from switching, which degrade the spectral performance. By using aliasing-free digital PWM and digital pre-distortion concurrently, spectral performance of the PMPT can be improved for wide bandwidth applications. For validation, a prototype transmitter was tested with a 20-MHz bandwidth downlink long-term evolution (LTE) signal at 836.5 MHz. Using the proposed method, the prototype transmitter achieved an output power of 19.8 dBm and drain efficiency of 24.4% while passing the spectral requirements of the LTE standard for femtocell base stations.