A 90-nm CMOS Quadrature Power Amplifier With High Efficiency Designed For Wireless Application

Abstract

The quadrature power amplifier (QPA) is used in a CMOS radio frequencies (RF) amplifier for wireless communication system such as WLAN and mobile communication (WCDMA). Because of its high efficiency at high frequency operation and good linearity. This paper presents a design and analysis in the time and frequency domains for quadrature power amplifier based on 90-nm CMOS technology. The Class D power amplifier is used in the QPA configuration, because of the switch mode amplifiers provide amplification for modulated signals at RF with high efficiency and linearity. The quadrature signals are to be directly amplified by using a QPA without decomposing these signal to a phase and amplitude signal because of the lack of its separate avoid and the linearity and bandwidth requirements, thus reducing power consumption. The results obtained show that the QPA can be used in a wide band spectrum. The amplifier has very good power added efficiency (PAE%) about (70.5%) and IDM3 is (62.6dBm) at maximum output power (24.35dBm) and input power greater than (20dBm). The amplitude distortion has been obtained in this work about (1.36 dB/dB), and phase distortion about (0.27 degree/dB). Keyword : Quadrature power amplifier(QPA), Quadrature modulator, classes amplifier. ) ةینقت مادختسا 90-nm CMOS ل ( ربكم میمصت لا )عون ةردق Quadrature ةءافكب ( ةیلاع تاقیبطتلا يف ةیكلسلالا يلع رفس نامقل .د نیسح ةزمح لماش لیعامسا رابجلا دبع دمحا لصوملا ةعماج / ةیئابرھكلا ةسدنھلا مسق ةصلاخلا عون ةردقلا ربكم مدختسی ) Quadrature ( لثم ةیكلسلالا تاقیبطتلا يف ) WLAN ةیولخلا تلااصتلاا ةمظناو ( ) WCDMA ( ةیلاعلا ھتءافك ببسب .ةدیج ةیطخبو ةیلاعلا تاددرتلا دنع ينمزلا نیزیحلاب لیلحتو میمصت ثحبلا اذھ يف مت يددرتلاو ل ) عون ةردقلا ربكم Quadrature ( بو ) ةینقت 90-nm CMOS .( ُتسا ) عون ةردقلا ربكم ربكملا ءانب يف مدخ D ( .ةیلاع ةءافكبو ةدیج ةیطخبو ةیویدارلا تاددرتلا دنع ةنمضملا تاراشلاا ریبكت ىلع ةرداق ةیحاتفملا ةردقلا تاربكم نلا مت كیكفت نودب مدختسملا ربكملا للاخ نم رشابم لكشب تامولعملا ةراشا ریبكتو نیمضت اھ روطلا ةراشاو عاستلاا ةراشا ىلا ةیطخو ةعساو ةمزح ضرع رفوی كلذ نلا فیط ىلع لمعی ربكملا نا جئاتنلا للاخ نم نیبت .ةلیلق كلاھتسا ةردقو ةیلاع او ةدیج ةیطخ كلتمتو ،تاددرتلا نم عس )يلاوح ىلا ةفاضملا ةردقلا ةءافك تلصو تیح ةیلاع ةءافكو 70.5% ( ةمیقو ) يلاوح ةثلاثلا ةیقفاوتلا عم لخادتلا -62.6dBm ( ) جارخا ةردق مظعا دنع 24.35dBm و ( ب ردق ة لاخدا ربكا )نم 20dBm .( ) يلاوح يعاستلاا ھیوشتلا لمشت يتلا ھیوشتلا رادقمل ةنكمم ةمیق لقا ىلع لوصحلا مت 1.36 dB/dB ( ) يلاوح يروطلا ھیوشتلاو 0.27 degree/dB .( Received: 26 – 5 2015 Accepted: 7 – 12 2015 Al-Rafidain Engineering Vol. 23 No. 5 December 2015 55 1Introduction The RF Power Amplifiers (PAs) are used in a wide variety of applications including wireless communication, TV transmissions, radar and RF heating. The basic techniques for RF power amplification can use classes as A, B, C, D, E, and F, for frequencies ranging from very low frequency through microwave frequencies. It is a critical element in transmitter units of communication systems, is expected to provide a suitable output power can range from a few mW to MW, depend by application. The output power from a PA must be sufficient for reliable transmission with a very good gain, high efficiency and linearity. High gain reduces the number of amplifier stages required to deliver the desired output power and hence reduces the size and manufacturing cost. High efficiency improves thermal management, battery lifetime and operational costs. Good linearity is necessary for bandwidth efficient modulation [1]. The mobile communication has become quite common in today with the increasing needs of effectively utilized bandwidth, and efficient and compact device technologies. The growth of wireless technologies is extremely fast. The information can be easily communicated by mobile communication system such as third generation wide-band code multiple access(WCDMA). High efficiency and good linearity are among the important characteristics of a base station power amplifier used in plurality of the communication application. The PAs are typically blocks of radio frequency front end circuits, which take more care to get efficient PA for saving the power consumption [2]. In the RF transmitter, the message signal undergoes several steps such as digital signal processing, digital to analog conversion and filtering. The last step between up conversion of the baseband signal to RF frequencies and the antenna is the amplification of the signal. The conventional way of designing PA’s is not to achieve maximum power transfer, but aiming for high efficiency and high linearity [3]. The power amplifier efficiency is a significant issue for the overall efficiency of most wireless system. Therefore, currently there are different kinds of Switched mode power amplifiers developed showing very high efficiency at higher frequencies. But all of these amplifiers are subjected to drive with the constant envelope signals. Whereas, for the increasing demand of high data rate transmissions in wireless communication there are some new modulation schemes introduced with generating no more a constant envelope signal but a high peak to average power signal. Therefore, recently a new technique is proposed, called the quadrature modulation for operating the switched mode PAs efficiently while driven by a high peak to average power signal [4]. C.H. Li et al. [5] presented a proposed of new power amplifier (PA) architecture as a more power efficient way to amplify modulated signals at radio-frequencies (RF) compared to conventional polar power amplifiers such as the Envelope Elimination and Restoration (EER) linearizing technique. the quadrature PA designed based on 90-nm CMOS models. They show a functional quadrature PA model with a power added efficiency of 30% at 6.4dBm output power driven at 2.4GHz and a maximum input power at 10MHz bandwidth, and 25% PAE at 5.1dBm output power at 50MHz. But the quadrature PA was designed in this paper has a good PAE about 70.5% at maximum output power of (24.35dBm) and input power greater than (20dBm) compared with [5]. In [6] F. Wang and others provided a detailed the wideband envelope elimination and restoration power amplifier(EER) with high efficiency wideband envelope amplifier for WLAN 802.11g applications. The authors have been gotten a PAE about 28% at 19dBm maximum output power driven at RF frequency 2.4GHz. Ali: A 90-nm CMOS Quadrature Power Amplifier With High Efficiency --------56 Figure (1): Quadrature modulator Figure (2): Block diagram of quadrature power amplifier (QPA) In this work an advanced design system (ADS) software has been used to design the RF amplifier type quadrature PA with high linearity and efficiency based on 90-nm process. The results obtained are very good and can be used on other frequencies such 2.14GHz for mobile communication and 2.45GHz for wireless applications 2Quadrature Power Amplifier (QPA) The QPA is a new power amplifier architecture and proposed as a more power efficient way to amplify modulated signals at radio-frequencies compared to conventional polar PAs. The quadrature signals as represented message signals (I(t) and Q(t)) can be directly amplified and modulated with RF carrier signal by using a QPA without decomposing the signal to phase and amplitude sets. The lack of a separating phase and amplitude signal path avoids the linearity and bandwidth requirements [5]. 2-1 Quadrature Signals The modulated RF signal is described as: ( ) = ( ) sin( + ∅( )) ............... (1) But written as ( ) = ( ) ( + ∅( )) ............... (2) ( ) = ( ) [ ( ) (∅( ) − ( ) (∅( )] ............... (3) ( ) = ( )cos(∅( )) ............... (4) ( ) = ( ) sin(∅( )) ............... (5) By using ( ) and ( ) in the equation (3) resulting in: ( ) = ( ) cos( ) − ( )sin( ) ............... (6) This result shows that a modulated RF signal can also be expressed as a subtraction of two modulated quadrature signals I(t) and Q(t). Figure (1) shows a possible block diagram of such quadrature modulator scheme. Two message signals, I(t) and Q(t) are mixed with a local oscillator with a 90° phase shift with respect to each other. A subtraction is used to obtain the signal according to (6)[7]. Figure (2) shows the concept for a PA system. The most basic form consists of two quadrature modulated PA’s, 90° phase difference in bridge mode. Each PA is driven by constant amplitude, constant phase, carrier signal with the voltage supply modulated by either I(t) or Q(t) signal. The load is an antenna sensing the difference between the modulated outputs of both PAs. Al-Rafidain Engineering Vol. 23 No. 5 December 2015 57 Figure (3): Quadrature power amplifier The bandwidth of the signal in a quadrature PA system, determined by the quadrature signals I(t) and Q(t), is much higher than the limited bandwidth of the other RF power amplifiers. The downside of using a quadrature configuration is the mismatch between the I and Q side in amplitude or phase. The result is a corrupted reconstruction of the RF message signal, downgrading overall performance[8]. A second downside using a quadrature configuration is the need for a power combiner. 2-2 Choice Of PA Configuration In Quadrature PA System The PA modulates an RF carrier signal with the quadrature signals I(t) and Q(t). The simplest way to achieve this is to use a switch mode amplifier such as Class D or Class E. These configurations are easily suitable for supply voltage modulation. Driving the amplifier with a hard switching RF signal and using the quadrature signal as supply voltage should generate the wanted modulated RF signal. Supply modulation using a linear mode amplifier such as Class-A or Class AB, would be impossible since the output current is not a direct and linear function of the voltage supply. Modulating and driving such PA configuration would involve a more complicated configuration [6]. The Class D has been choice in this work because of its higher efficiency, and it's a switch drive with a hard switching, 2.4-G