circuit note cn- 0134 circuits from the lab? tested circuit designs address com mon design challenges and are engineered for quick and easy system integration. for more information and/or support , visit www.analog.com/cn0 134. devices connected /referenced ADF4350 fractional - n pll ic with i ntegrated vco adl5375 wideband transmit modulator adp150 low noise 3.3 v ldo adp3334 low noise a djustable ldo broadband low error vector magnitude ( evm ) direct conversion transmitter rev . b circuits from the lab? circuits from analog devices have been designed and built by analog devices engineers. standard engineering practices have been employed in the design and construction of each circuit, and their function and performance have been tested and verified in a lab environment at room temperature. however, you are solely responsible for testing the circuit and determining its suitability and applicability for your use and application. accordingly, in no event shall analog devices be liable for direct, indirect, special, incidental, consequential or punitive damages due to any cause whats oever connected to the use of any circuits from the lab circuits. (continued on last page) one technology way, p.o. box 9106, norwood, ma 02062 - 9106, u.s.a. tel: 781.329.4700 www.analog.com/circuits fax: 781.461.3113 ? 2010 analog devices, inc. all rights reserved. evaluation and desig n support circuit evaluation boards cn - 0134 evaluation board ( cftl - cn0134 - evalz ) design and integration files schematic s, layout files, bill of materials circuit function and benefits this circuit is a complete implementation of the analog portion of a broadband direct conversion transmitter ( a nalog b aseband i n, rf out). rf frequencies from 500 mhz to 4.4 ghz are supported throu gh the use of a pll with a broadband integrated v oltage c ontrolled oscillator (vco). harmonic filtering of the lo from the pll ensures excellent quadrature accuracy. 22nf 10nf 330nf 180 ? 82 ? ibbp ibbn loip loin qbbp qbbn spi-compatible serial bus ADF4350 v vco v vco v dd 3.3v cp gnd agnd d gnd rf out bC rf out b+ cp out 1nf 1nf 4.7k ? r set le data clk ref in fref in v tune dv dd av dd ce 10 28 16 29 1 2 3 22 8 31 9 11 18 21 27 51 ? a gndvco 14 15 17 20 7 pdb rf 26 sd gnd 6 32 sdv dd v p 5 sw 4 ad l 537 5 r fout rf out aC rf out a+ 13 12 v vco z bias z bias quadrature phase splitter i/q sma inputs i/q sma inputs adp150 1f 1f 5.5v 5.0v vps1, vps2 adp3334 1f 1f 5.5v 08659-001 figure 1. direct conversion transmitter (simplified schemat ic: all connections and decoupling not shown)
cn- 0134 circuit note rev. b | page 2 of 5 08659-002 figure 2. evaluation board for cn - 0134 direct conversion transmitter low noise ldos ensure that the power management scheme has no adverse impact on phase noise and evm. this combi nation of components represents industry - leading direct conversion transmitter performance over a frequency range of 500 mhz to 4.4 ghz circuit description the circuit shown in figure 1 utilizes the ADF4350 , a fully integrated fractional - n pll ic, and the adl5375 wideband transmit modulator. the ADF4350 provides the local oscillator (lo) signa l for the adl5375 transmit quadrature modulator, which upconverts analog i/q signals to rf. taken together, the two devices provide a wideband baseband iq to rf transmit solution. the ADF4350 is powered off the ultralow noise 3.3 v adp150 regulator for optimal lo phase noise performance. the adl5375 is powered off a 5 v adp3 334 ldo. the adp150 ldo has an output voltage noise of only 9 v rms and helps to optimize vco phase noise and reduce the impact of vco pushing (equivalent to power supply rejection). filtering is required on the ADF4350 rf o utputs to attenuate harmonic levels so as to minimize errors in the quadrature generation block of the adl5375 . from measurement and simulation, the odd order harmonics contribute more than even orde r harmonics to quadrature error and , if attenuated to below ? 30 dbc , results in sideband suppression performance of ? 40 dbc or better. the ADF4350 s 2nd ha rmonic (2h) and 3rd harmonic (3h) levels are as given in the data sheet and shown in table 1 . to get the 3rd harmonic below - 30 dbc, approximately 20 db of attenuation is required. table 1 . ADF4350 rf o u tput h armonic l evels u nfiltered harmonic content (second) ? 19 dbc fundamental vco output harmonic content (third) ? 13 dbc fundamental vco o utput harmonic content (second) ? 20 dbc divided vco output harmonic content (third) ? 10 dbc divided vco output this circuit gives four different filter options to cover four different bands. the filters were designed for a 100 ? differen - tial input ( ADF4350 rf outputs with appropriate matching) and 50 ? differential output ( adl5375 loin differential impedance). a chebyshev response was used for optimal filter roll - off at the expense of increased pass - band ripple. the filter schematic is shown in figure 3 . this topology allows the use of either a fu lly differential filter to minimi z e component count, a single - ended filter for each output , or a combination of the two. it was determined that for higher frequencies (> 2 ghz) two single - ended filters gave the best performance because the series inductor v alues are twice the value compared to a fully differential filter and , hence , the impact of component parasitics is re duced. for lower frequencies (< 2 ghz), a fully differential filter provides adequate results.
circuit note cn- 0134 rev. b | page 3 of 5 table 2 . adf43 50 rf output f ilter c omponent v alues (dni = d o n ot i nsert) frequency range (mhz) z bias l1 (nh) l2 (nh) c1a (pf) c1c (pf) c2a (pf) c2c (pf) c3a (pf) c3c (pf) a. 500C 1300 27 nh|| 50 ? 3.9 3.9 dni 4.7 dni 5.6 dni 3.3 b. 850C 2450 19 nh || (100 ? in position c1c) 2.7 2.7 3.3 100 ? 4.7 dni 3.3 dni c. 1250C 2800 50 ? 0 ? 3.6 dni dni 2.2 dni 1.5 dni d. 2800C 4400 3.9 nh 0 ? 0 ? dni dni dni dni dni dni the ADF4350 output match consists of the z bias pull - up and, to a lesser extent, the decoupling capacitors on the supply node. to get a broadband match it is recommended to use either a resistive load (z bias = 50 ? ) or a resi stive in parallel with a reactive load for z bias . the latter gives slightly higher output power, depending on the inductor chosen. note that it is possible to place the parallel resistor as a differential component (i.e. 100 ?) in position c1c to minimize board space. this is done in filter type c, described in table 2 . the filter should be designed with a cutoff approximately 1.2 to 1.5 times the highest frequency in the band of interest. this allows margin in the design , as typic ally the cutoff will be lower than designed due to parasitics. the effect of pcb parasitics can be simulated in an em simulation tool for improved accuracy. 08659-003 ADF4350 13 rfouta+ 12 rfoutaC adl5375 9 loip 10 loin l1 l2 1nf l1 l2 1nf c1a c1a c1c c2a c2a c2c c3a c3a c3c z bias z bias 120pf 120pf 0.1f 3.3v figure 3. ADF4350 rf output filter s chematic as can be seen from table 2 , at lower frequencies below 1250 mhz , a 5th order filter is required. for 1.25 ghz to 2.8 ghz, 3rd order filtering is sufficient. for frequencies above 2.8 ghz, no filtering is required, as the harmonic levels are sufficie ntly low to meet sideband suppression specifications. 08659-004 0 C70 C60 C50 C40 C30 C20 C10 800 1000 1200 1400 1600 1800 2000 2200 2400 ssb (dbc) frequency (mhz) no filtering filter b: 850mhz to 2450mhz figure 4. sideband suppression for filter b, 850 mhz to 2450 mhz 08659-005 q i error vector measured signal phase error (i/q error phase) magnitude error (i/q error phase) ideal signal (reference) 0 figure 5 . evm plot a sweep of sideband suppression vs. frequency is shown in figure 4 for the circuit using filter b (850 mhz to 2450 mhz). in this sweep, the test conditions were the following: baseband i/q amplitude = 1 v p - p differential sine waves in q uadrature with a 500 mv (adl5 375- 05) dc bias; baseband i/q frequency (fbb) = 1 mhz.
cn- 0134 circuit note rev. b | page 4 of 5 table 3 . single -c arrier w - cdma composite evm results comparing filter vs. n o filter on ADF4350 rf outputs (measured as per 3gpp s pecification test m odel 4 ) frequency (mhz) c omposite evm n o lo f iltering composite evm with lo f iltering , f ilter c mod ulator output power (dbm) 2140 3.50% 1.80% ? 7 1800 3.40% 1.50% ? 7 900 3.30% 0.90% ? 7 error v ector m agnitude ( evm ) is a measure of the quality of the performance of a digital tr ansmitter or receiver and is a measure of the deviation of the actual constellation points from their ideal locations, due to both magnitude and phase errors. this is shown in figure 5 . evm measurements are given in table 3 comparing results with and without the filter. in this case the baseband i / q sig nals were generated using 3gpp test model 4 using a rhode and schwarz amiq i/q modulation generator with differential i and q analog outputs . filter b was also used. a block diagram of the test setup for evm is given in figure 6. adjacent channel leakage r atio (aclr) is a measure of the power in adjacent channels relative to the main channel power and is specified in dbc. the lo phase noise and the linearit y of the modulator are the main contributors to aclr. the aclr test setup is the same as for evm with the exception that coaxial filters were placed on the i/q outputs of the signal generator to reduce aliasing products. 08659-006 r&s amiq gen. i+ iC q+ qC spectrum analyzer [r&s fsq 8] power supply cn-0134 evaluation board 5.5v rf out figure 6. evm measurement setup (simplified diagram ) in addition to the improvement in sideband suppression and evm, there is also a performance benefit to driv ing the adl5375 lo inputs differentially. this im proves modulator oip2 performance by 2 db to 5 db, compared with single - ended lo drive. note that most external vcos only come with a single - ended output, so using the differential outputs on the ADF4350 provides a benefit over an external vco in this case . figure 7 shows sideband suppression results using an 8 5 0 mhz to 2450 mhz filter ( f ilter b) . 08659-004 10 C60 C50 C40 C30 C20 C10 0 0 500 1000 1500 2000 2500 3000 3500 ssb (dbc) frequency (mhz) ssb #10 +5dbm ssb #10 +2dbm ssb #10 C1dbm ssb #10 C4dbm figure 7 . sideband suppression results for 850 mhz to 2450 mhz filter b a complete design support package f or this circuit note can be found at http://www.analog.com/cn0134 - designsupport . n tns it is possible to use the auxiliary outputs on the ADF4350 to switch between two filter types where wideband operation beyond that possible with one single filter is required. this is shown in figure 8 . a n rf d ouble - p ole , 4 - t hrow switch (dp4t) is used to select the differential outputs of either filter 1 or filter 2.
circuit note cn- 0134 rev. b | page 5 of 5 ADF4350 13 rfouta+ 12 rfoutaC 14 rfoutb+ 15 rfoutbC 08659-008 adl5375 9 loip 10 loin 1nf 1nf filter 1 dp4t switch filter 2 figure 8. application d iagram s howing p ossibility of f ilter s witching u sing the ADF4350 m ain and a uxiliary o utputs circuit evaluation a nd test the cftl - 0134- evalz evaluation board con ta ins the circuit described in c ircuit n ote cn - 0134, allowing for the quick setup and evaluation of the circuits performance. the control software for the cftl - 0134- evalz board uses the standard ADF4350 programming software, located on the cd that accompani es the evaluation board. equipment needed a standard pc running windows? xp, windows vista (32 - bit), or windows 7 (32 - bit) with usb p ort, the cftl - 0134 - e va l z circuit evaluation board , and the ADF4350 programming software , power supplies, i - q signal so urce, such as a rhode & schwarz amiq, and a spectrum analyzer such as the rhode & schwartz fsq8 . for additional details see the evaluation guide ( cn0134 - evalguide - reva.pdf ) , which is contained in the design support package ( http://www.analog.com/cn0134 - designsupport ) , and the ADF4350 and adl5375 data sheets. getting started see cn0134 - evalguide - reva.pdf for software installation and test setup. the documentation also includes the block diagram, the application s chematic, the b ill of m aterials, and the layout and a ssembly information . also see t he ad4350 and adl5375 data sheets for additional details. functional block diagram see figure 1 and figure 6 in circuit note cn - 0134 and the cn0134 - evalguide - reva.pdf , wide band tx modulator solution user document in the design support package . setup and test see circuit n ote cn - 0134 and the cn0134 - evalguide - reva.pdf , wideband tx modulator solution user document, for software installation and test setup. also see t he ad4350 and adl5375 data sheets for additional details. learn more cn0 134 design support package: http://www.ana log.com/cn0134 - designsupport adisimpll design tool adisimpower design tool adisimrf design tool an - 0996 ap plication note. the advantages of using a quadrature digital upconverter (qduc) in point - to - point microwave transmit systems . analog devices. an - 1039 application note. correcting imperfections in iq modulators to improve rf signal fidelity . analog devices. data sheets and evaluation boards adf435 0 data sheet ADF4350 evaluation board adl537 5 data sheet adl5375 evaluation board adp15 0 data sheet adp333 4 data sheet revision history 11/10 rev. a to rev. b changes to circuit note title .......................................................... 1 added evaluation and design support section ............................ 1 changes to circuit description sectio n ......................................... 2 changes to figure 6 .......................................................................... 4 added circuit evaluation and test section ................................... 5 9/10 rev. 0 to rev. a changes to circuit note title .......................................................... 1 changes to circuit function and benefits section ....................... 1 changes to circuit description section ......................................... 2 changes to common variations section ....................................... 4 1 / 10 revision 0 : initial version (continued from first page) circuits from the lab circuits are intended only for use with analog devices products and are the intellectual property of an alog devices or its licensors. while you may use the circuits from the lab circuits in the design of your product, no other license is granted by implication or otherwise under any patents or other intellectual property by application or use of the circuits from the lab circuits. information furnished by analog devices is believed to be accurate and reliable. however, "circuits from the lab" are supplied "as is" and without warranties of any kind, express, implied, or statutory including, but not limited to, any implied warranty of merchantability, noninfringem ent or fitne ss for a particular purpose and no responsibility is assumed by analog devices for their use, nor for any infringements of patents or other rights of third parties that may result from t heir use. analog devices reserves the right to change any circuits fro m the lab circuits at any time without notice but is under no obligation to do so. ? 2010 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. cn08659 - 0 - 11/10(b)
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