IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 44, NO. 3, MARCH 2009 675 Multi-Standard Mobile Broadcast Receiver LNA With Integrated Selectivity and Novel Wideband Impedance Matching Technique Tae Wook Kim, Member, IEEE, Harish Muthali, Susanta Sengupta, Kenneth Barnett, Member, IEEE, and James Jaffee, Member, IEEE Abstract—A CMOS LNA supporting multiple mobile video stan- plification which incorporates the low-pass filter (LPF) section dards (MediaFLO, DVB-H, and ISDB-T) is implemented using a for selectivity against unwanted interfering signals. There is also 0.18 m CMOS process. The LNA uses a novel feedback config- a closed loop path which diverts a portion of the signal power uration and implements an RF elliptic low-pass filter (LPF) re- sponse. Because of this elliptic LPF response, the receiver is able to to realize wideband feedback that can be used to provide wide operate concurrently with radio transmitter leakage from GSM, band impedance matching. DCS, WLAN, and Bluetooth. The design decouples the feedback To accomplish the rejection of the concurrent transmitter path from the main path to allow integration of the LPF as well signals, an integrated elliptic LPF based on a double cascode as obtain wideband input matching. Measurement results show voltage gain of 25 dB, NF of 1.6 dB, and IIP3 of 2 dBm in Medi- topology is proposed. Rejection of 70 dB is achieved by aFLO mode. DVB-H mode demonstrates voltage gain of 25 dB, NF cascading the elliptic LPF response ( 40 dB) with a bandpass of 1.8 dB, and IIP3 of 1 dBm while achieving interference rejec- filter (BPF) response ( 30 dB). The BPF is realized with a tion greater than 70 dB. capacitively tuned transformer load. The cascode devices act as Index Terms—CMOS LNA, broadcast, wireless video, mo- buffers between the filter sections. bile broadcast, concurrent operation, wideband RF, wideband In a mobile wireless communication channel, automatic gain impedance matching, partial feedback, notch filter, integrated control (AGC) functionality is required to avoid exceeding filter, RF filter, elliptic filter, MediaFLO, DVB-H, TV tuner. the dynamic range of the baseband analog-to-digital converter (ADC). Digital AGC can be employed to simplify the RF and I. INTRODUCTION analog design. The AGC in this case is digital in the sense that HE modern consumer expects their mobile phone to sup- there are discrete gain states that are controlled by the digital T port various media services simultaneously. For example, baseband section. The proposed LNA has six discrete gain one should be able to simultaneously discuss a football match states to implement the required AGC. with his friends over a mobile phone using a Bluetooth headset As standardized in the USA, MediaFLO operates in the fre- while enjoying the game on his mobile TV screen. To do this, the quency band 720–760 MHz [3] and does not require wideband phone should support concurrent operation between video re- operation. As such, MediaFLO does not need the same out-of- ceivers and the various transmitters that may exist in the handset. band harmonic rejection as in the wideband DVB-H case. But, The multi-mode, multi-standard receiver must have the neces- because of possible interference from adjacent analog television sary rejection of those transmitter signals while still achieving stations, the MediaFLO system does have a need for narrowly wideband input matching, low noise, and wide dynamic range selective front-end filters to provide significant adjacent channel [1], [2]. rejection. To avoid the additional insertion loss of switches both In order to meet such requirements, several approaches may preceding and following these RF channel select filters, dual in- be taken. Resistive feedback can achieve wideband impedance puts are provided for MediaFLO operation. This removes the matching in short channel MOSFET circuits [4]. However, in need for an RF switch after the filters [3] and hence provides im- proved sensitivity for this situation. This leads to a MediaFLO this low-noise amplifier (LNA), the phase shift caused by the cascade of two LC filter stages and loop gain greater than unity requirement for a single-ended LNA design. can result in amplifier instability [5]. In order to prevent such Therefore, it is advantageous to employ a topology that is instability, we propose a novel partial feedback technique. This easily optimized for this application. For this purpose, a pair of single-ended cascode LNAs with inductive degeneration are allows us to combine two paths, each of which is optimized for its particular function. There is an open loop path for signal am- used in MediaFLO USA operation. To minimize the number of I/Os, these two single-ended LNAs share the same inputs and outputs as the differential DVB-H LNA. A diagram illus- Manuscript received April 22, 2008; revised October 27, 2008. Current ver- trating this situation is shown in Fig. 1. The outputs of the single- sion published February 25, 2009. T. W. Kim is with the Department of Electrical Engineering, Yonsei Univer- ended and differential LNAs are combined at the transformer for sity, Seoul 120-749, Korea (e-mail: [email protected]). both DVB-H and MediaFLO modes. Since the subsequent mixer H. Muthali, S. Sengupta, and K. Barnett are with Qualcomm, Inc., Austin, stage is differential, the transformer also provides the neces- TX 78759 USA. J. Jaffee is with Qualcomm, Inc., San Diego, CA 92121 USA. sary single-ended-to-differential conversion required in the Me- Digital Object Identifier 10.1109/JSSC.2008.2011035 diaFLO mode. 0018-9200/$25.00 © 2009 IEEE Authorized licensed use limited to: NORTHERN JIAOTONG UNIVERSITY. Downloaded on February 25, 2009 at 21:26 from IEEE Xplore. Restrictions apply. 676 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 44, NO. 3, MARCH 2009 Fig. 1. Proposed LNA block diagram. The paper is organized as follows. Following the introduction to use fully passive techniques with no Q-enhancement. The in Section I, Section II will introduce the system motivation for required rejection can be calculated with the following equa- the DVB-H LNA design. In Section III, the circuit design of tions, where is the required out-of-band rejection of the multi-mode LNAs will be discussed including the integrated the LNA, is the input signal power, is the out-of-band selectivity, the partial feedback topology, and the gain control jammer signal power, is the loss of the front-end RF filter, schemes. In Section IV, measurement results will be presented, and is the antenna isolation between the antennas used and the conclusion will follow in Section V. for the various phone radio transmitters and the antenna used for the broadcast receiver antenna. ( 9.5 dB) is the con- II. SYSTEM MOTIVATION FOR THE DVB-H LNA DESIGN version gain difference between the fundamental tone and the As shown for the wideband case in Fig. 2, the harmonics of third-order harmonic as shown in (1). is the required the local oscillator (LO) signal can translate out-of-band inter- signal-to-noise ratio for detection [12]. (See (1) and (2), at the ferers near the odd-harmonics of the LO into the desired base- bottom of the page.) band channel, resulting in receiver performance degradation. The required LNA rejection from (1) and (2) largely de- Equation (1) for the mixer gain shows how the third harmonic of pends on the RF front-end filter rejection properties. Generally, the LO can be translated to baseband. In (1), is the voltage these improve at larger offset frequencies. Thus, most of the at the intermediate frequency (IF) for the mixer output [6]; higher frequency interferers would have less stringent rejection is the transconductance of the mixer, is the load resistance requirements. If we assume 10 dB margin to allow for con- of the mixer, is the input RF signal frequency, and is tributions from other interference sources or inaccuracies in the LO frequency. In a DVB-H receiver (which uses the fre- estimates of the various attenuation components, (2) indicates quency band of 470–862 MHz [7]–[9]), the third harmonic of that we need 70 dB rejection through the LNA the LO in a direct conversion receiver can translate the DCS at 1.8 GHz. 1.8 GHz transmitter (Tx) signal inside of the wanted baseband signal bandwidth. Similarly, transmitter signals at IMT 2.0 GHz, III. CIRCUIT DESIGN WLAN 2.4 GHz, and Bluetooth 2.4 GHz would be downcon- verted by the harmonics of the LO. It is necessary to reject in- A. On-Chip Elliptic Low-Pass Filter terferers before they enter the mixer [10], [11]. One can improve Fig. 3 shows a schematic diagram of a third-order section of the attenuation by compensating the loss of a resonant tank the elliptic LPF. The LPF section is composed of a parallel LC using negative impedance techniques. However, the attenuation resonator with shunt capacitive terminations. The transfer func- at the resonant frequency will degrade as the blocker power in- tion for the LPF section is given by (3), where is the input creases. This effect is shown in [11]. In this design, we elected current to the filter, is the output current, is the (1) (2) Authorized licensed use limited to: NORTHERN JIAOTONG UNIVERSITY. Downloaded on February 25, 2009 at 21:26 from IEEE Xplore. Restrictions apply. KIM et al.: MULTI-STANDARD MOBILE BROADCAST RECEIVER LNA 677 Fig. 2. Illustration of out-of-band harmonic interference scenario for DVB-H. Fig. 3. Schematic diagram of (a) elliptic LPF and (b) equivalent circuit for the transfer function. output conductance of M1, is the transconductance of M2, resonates at 1.8 GHz to generate maximum attenuation and are shunt capacitors, and is the impedance while and generate the LPF characteristic.