Concurrent Dual-Band

Zubair Akhter RFIC Research Group

Indian Institute of Technology, Roo86zubair@gmail.com

Abstract — The paper reports design of a band transmitter for simultaneous operationA combination of direct-conversion and parais utilized to satisfy the requirements omodulation schemes that are employed in wnetwork. The entire transmitter structureusing hybrid microwave integrated circuit (HThe system exhibits a maximum data rate of 6

Keywords-: Dual-band transmitter; ConcurTransmitter on surface mount technology (SM

I. INTRODUCTION Transistor’s invention, Shannon’s inform

the concept of cellular system revolutionizedcommunication technology. Transmitter when compared receiver design, is more renon-existence of critical implementation rejection and band selectivity. Among vaarchitectures, the direct-conversion structuresignal with a local oscillator (LO) outpuamplifying the resulting signal through a (PA) after being band-pass filtered [1]. Henoise is not critical, since baseband signal poenough to maintain the required signal-to-no

A concurrent dual-band transmitter radiofront-end system is designed and implemerequirements of wireless local area networproposed transmitter architecture employs conversion and the parallel schemes to cofrequency ranges of 2.4- to 2.48-GHz and 5[2]. The presented design is a general solutbe further modified to be of use in any of thstandards. This is because its building antenna, power combiner, PA) have suffi(BW) to meet the above standards at compon

II. PROPOSED ARCHITEC

The architecture is divided into four sectfigure (1). Section-1 refers to the basebandwith main emphasis on the modulation schemWLAN, viz., Orthogonal Frequency-Divisi(OFDM). Input signal bandwidth is one of thspecifications that are required for the designRF front-end. Maximum bandwidth of WLAN analog baseband signal is assumed

d Transmitter for 2.4-/5.2-GHz WiApplications

orkee

Nagendra P. PathRFIC Research Gr

Indian Institute of Technolonagppfec@gmail.com, nagppf

concurrent dual-n at 2.4-/5.2-GHz. allel architectures

of various signal wireless local area e is implemented

HMIC) technology. 60-Mbps.

rrent transmitter; MT).

mation theory and d mobile wireless

system design, elaxed because of issues of image

arious transmitter e mixes baseband ut; subsequently, power amplifier

erein, the mixer’s ower is sufficient

oise ratio (SNR). o-frequency (RF)

ented to meet the rk (WLAN). The

both the direct-over dual WLAN .15- to 5.35-GHz tion in that it can he WLAN a/b/g/n

blocks (filters, ficient bandwidth nent level.

CTURE tions, as shown in d processing part me that is used in ion Multiplexing he several crucial n of transmitter’s

f the modulated d to be 30-MHz.

Section-2 indicates that the two aninterest are centered around 60frequencies.

Fig 1: RF front-end architectudual-band transm

In section-3, the two analog b

converted to be transmitted in desirand 5.2-GHz. The up-conversion invlocal oscillator (LO), each for the ranges; thereby, leading to a parallea dual-band power combiner is usdifferent bands’ contents. Section-4concurrent dual-frequency amplwireless transmission. The next design details and measurement resuthe system.

A. Dual-Band Power Combiner The power divider and the com

components for microwave powerfrequently used power divider isdivider. A conventional Wilkinsononly at one design frequency and iit is not suitable for dual band operseen a worldwide effort to develop [3-10] due to trend towards implemobile communication systems. Wvarious constraints on values capacitances. Moreover, inductor dtechnology is a tedious task. The strand Lee [8] is not suitable for cisolation between input ports. Furtconstraint of frequency ratio being a

ireless LAN

hak roup ogy, Roorkee fec@iitr.ernet.in

nalog baseband signals of 00-MHz and 830-MHz

ure of the proposed mitter

baseband signals are up-red WLAN bands of 2.4- volves a set of mixer and two different frequency

l architecture. Thereafter, sed to combine the two 4 involves the process of lification followed by section delves into the

ults of each component of

mbiner are very important r amplifier. One of the s the Wilkinson power n power divider operates its harmonics. Therefore, ration. Recent years have dual-band power divider mentation of multi-band Wu, et. al., [7] exhibit

of inductances and design in microstrip line ructure proposed by Park coupler because of poor ther, the design involves always less than 3.

2011 International Symposium on Electronic System Design

978-0-7695-4570-7/11 $26.00 © 2011 IEEE

DOI 10.1109/ISED.2011.24

1

The implemented dual-band powecombiner is a modified version Wilkinsonwherein each quarter-wavelength (�/4) tr(TL) section is replaced with a �-network [figure (2). This �-section is designed suchcombiner operates at the desired two freque

Fig 2: Transmission line and its �-eq The equivalence between the λ/4 TL- an

be established using ABCD matrices. The Aa λ/4 TL-section is given as follows:

����������� � � ����

when �1 = �� . The ABCD matrix, [T2], fo

����� ������ � ���� ����������������� ��� �� � ���������������� ������ � After equating elements of both matrconditions are derived for dual-frequency (f

Z2 sin�2f1= ± Z1

Z2 sin�2f2= ± Z1

One of the solutions for equations (3) �2f1 = n� –�2f2, where n = 1, 2, 3, 4... etc. ���� �� � �� ! "## $$����������������������������������

���� �� � �� ! "###��������������������������������� ���� �� � %� ! "###���������������������������������

���� �� � %� ! "## $$����������������������������������

where R = f2/f1. Smallest size is achieved for m = n = 1. H

design equations are as follows:

er divider-cum-n power divider, ransmission line [11], as shown in h that the power ncies.

quivalent

nd π-sections can ABCD matrix of

(1)

or �-section is:

�����������������!�����&

(2) rices, following f1 & f2) operation

(3)

(4)

and (4) require

�����������������)*+ ������������������),+ ������������������)-+ �����������������).+ Hence, final

��� �� � /�01��2��� ### Z3 = Z2 tan�2f1 tan�3f1

Dimensions of TL-sections apolytetraflouroethylene (PTFE) subrelative permittivity �r = 3.38, losssubstrate height h = 1.524-mm. mentioned in table (1).

Table 1: Dimensions of Micr

Dimensions

in mm

Characteristics Impedance i/p and o/p lines

Z0=50 Width, W 3.5076 Length, L 19.2 Since, the width for the charac

infeasibily small (0.06291-mm), thfabricated at laboratory level. Sincthe frequency ratio, R, therefore, theimplement all TL-sections. Final taken as 2.0-GHz and 5.2-GHz. Threalizable at laboratory level, are ind

Table 2: Dimensions of Micro

Dimensions

in mm Characteristics

impedance of i/p and o/p lines

Width, W 3.5076

Length, L 19.2

The implemented structure for π-section Wilkinson power combifigure (3). The dimensions used fotwo π-networks are taken from table

Fig 3: Implemented concurrent dua

#### $ )3+ ……... (10)

are calculated for the bstrate, NH9338, having s tangent � = 0.0024 and

These dimensions are

rostrip (calculated)

Characteristics impedances of 4-

section Z2=84 Z3=197 1.3196 0.06291 12.46 13.16

cteristic impedance Z3 is hus, it cannot be easily ce, Z3 value depends on e ratio is compromised to

design frequencies are he optimized dimensions, dicated in table (2).

strip (Implemented)

Characteristics impedances of 4-

section 1.046690 0.31493

11.91 13.6

the designed dual-band ner (WPC) is shown in

or the TL-sections in the e (2).

al-band Power combiner

2

The measurement results for the implemented circuit differ from desired values to some extent, as can be compared through figures (4) and (5).

Fig 4: Simulated S-parameters for concurrent dual-band

power combiner

Fig 5: Measured S-parameters for concurrent dual-band

power combiner

The results still exhibit dual-band characteristic of the circuit at the two desired frequencies. However, the losses may be attributed to fabrication errors. The return losses at the input ports, i.e., port 2 and port 3, are -35dB and -36dB at 2.4-GHz and 5.2-GHz, respectively. Further, coupling from ports 2 and 3 to port 1 is -3.8dB at both the frequencies of interest. Moreover, isolation between the two output ports is -13.6dB at 2.4-GHz and -17.21dB at 5.2-GHz. Hence, the �-section WPC has been designed and implemented successfully along with achievement of the desired results.

B. Mixers and Local Oscillator In this design, two mixers [12], ZEM-4300MH+ and

ZMX-7GHR, are used to up-convert signals in the two parallel branches for the two signal streams at 2.44-GHz and 5.25-GHz. HP-8620 sweep generator and Agilent E8257D PSG Analog signal generator generate the LO signals. For 2.4-GHz band, 600±15 MHz signal is mixed with a LO frequency of 3040-MHz using ZEM-4300MH+,

thereby, producing signals with frequencies 2.44-GHz and 3.64-GHz. For 5.25-GHz band, 830±15MHz signal is mixed with twice the LO frequency (as it is easier to obtain harmonics), thereby, producing 5.25-GHz and 6.91-GHz signal frequencies. Resulting signals are filtered and combined using band-pass filter and thereafter, combined through power combiner.

C. Band-Pass Filters A standard coupled line filter has been employed and the

design equations are taken as follows [13]:

/5�6� � 78�9:� ������#######��$ )""+ /56; � 8�9<:;=�:; �����#### $$��� $ $ )"9+ /56>?� � 7 8�9:>:>?� �����## $ $ $ #�$ )"@+ /5A � /5B" ! 6/5 ! )6/5+�C�$ #$�� $ $ )"D+� /5E � /5B" � 6/5 ! )6/5+�C�#�# $ )"*+ The implemented band-pass filters (BPFs) for the two

parallel signal branches are shown in figure (6).

Fig 6: Implemented band-pass filters (2.4-GHz & 5.25-GHz)

The observed readings for the fabricated BPFs are indicated in figures (7) and (8).

Fig 7: Band-pass filter response 2.44-GHz

3

Fig 8: Band-pass filter response 5.2

D. Power Amplifier In this design, Agilent 8300A Mic

amplifier [14] is used as power amplifier the signal. Basically, this is a wideband ama very large frequency range from 10-MHexhibits a maximum gain of 20-dB with 8dB. Hence, this PA is used to amplifyspectra and the resulting signal is fed to amonopole antenna.

E. Dual-Band Antenna

A monopole type of antenna isimplementation because such antennas antennas for a system. Besides, a monopoldesigned without any protruded portion inoccupies a small volume of the system, thebe useful for WLAN or Bluetooth applicatio

The designed dual-band monopole antenof two rectangular elements that are stackother. It is fed by a 50� microstrip line3.5-mm and length Lf = 10-mm. The rectanelements are printed on one side with lenwidth W = 35mm over the NH9338 substrplane is printed on the other side of the subsLg = 9.2-mm and width Wg = 35-mm. Herectangular monopole element controls the mode of the antenna. It has width of Ws length of Ls = 7.5-mm. On the other hrectangular monopole element controls themode of the antenna and possesses width Wlength Lb = 17.5-mm. There is another elemto improve the return loss at both frequenciWe = 6-mm and Le = 5-mm. One thing tooperating frequency and the bandwidth changes in size of the ground plane. Instructure proposed in [15] uses an extra smto improve the return loss response. In thethis improvement is brought about throlength of the bigger patch as compared to thThe fabricated antenna is shown in figure (9

25-GHz

crowave system (PA) to amplify

mplifier, covering Hz to 20-GHz. It noise figure of

fy the dual-band a dual-frequency

s selected for are concealed

e antenna can be n appearance and ereby, proving to ons. nna [15] consists ked one over the e of width Wf = ngular monopole

ngth L = 45-mm, rate. The ground strate with length erein, the smaller

higher operating = 11.2-mm and

hand, the bigger e lower operating Wb = 15-mm and ment that is used ies and has width o note is that the are sensitive to n any case, the

mall metallic strip e existing design, ugh increase in he smaller patch. 9).

Fig 9: Implemented dual-band

Figure (11) indicates return loss obsMismatch in response may be due to

Fig 10: Simulated and measured re Table (3) compares the measurefabricated antenna with certain staantennas [15], [16].

Table 3: Comparison of measurantenna with some standard prin

@ Bfc @2.44GHz

Reference [15] 760 MHz Reference [16] 570MHz Proposed 950MHz

Figures (11) and (12) show the anradiation patterns for the two design

Fig 11: Measured and simulated Eat 2.4- and 5.2-

d monopole antenna

servation for the antenna. o fabrication tolerances.

eturn loss of the antenna

ed performance of the andard printed monopole

ed performance of the nted monopole antennas Bandwidth z fc @ 5.25GHz

720MHz 310MHz 720MHz

ntenna’s E- and H-plane n frequencies.

E-plane radiation patterns

GHz

4

Fig 12: Measured and simulated H- plane raat 2.4- and 5.2-GHz

III. RESULTS AND DISCUSSI

All designed components are placed acc(1) and, thereafter, the system is fed with asignals. The measurement set-up for the wtransmitter system is shown in figure (13).

Fig 13: Complete set-up for measurementransmitter’s performance

Besides, another identical antenna is pl

region to receive the generated dual-banreceived signal’s spectrum is observed analyzer, and is shown in figure (14).

Fig 14: Spectrum received by the

adiation patterns

ION cording to figure appropriate input whole dual-band

nt of dual-band

laced in far-field nd signals. The on a spectrum

e antenna

IV. REFRENC

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