Zero if direct conversion fewest components easiest to

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Unformatted text preview: -80 -60 -40 -20 band by producing a DC output proportional to the log AVERAGE slope of approximately of the IF signal level with aRF INPUT POWER (dBm) 15mV/dB (see Typical Operating Characteristics). 0 L TOTAL = L1 + LPARASITICS where: 70 fp is the amount the crystal frequency is pulled in ppm. Cm is the motional capacitance of the crystal. 60 0 -50 Superhet vs. “zero-IF” vs. low IF Superhet - Need IF filters + Quadrature demod circuitry operates at relatively low frequency Low-IF + Only 1 A/D converter + Quadrature demod is done in DSP - perfect I/Q channel balance. - May need “image-reject” mixer to attenuate the image response. Zero-IF (direct conversion) + Fewest components, easiest to implement “on-chip” - Quadrature demod operates at carrier frequency (need high frequency quadrature splitter and 2 high frequency mixers) - LO leakage causes DC offsets in I/Q channels. I and Q channel output spectrum has a (possibly large) “spike” at DC. Can saturate DC-coupled amplifiers - must be removed. Desired signal’s DC component will also be removed. - “flicker noise” (1/f noise) is a problem. High gain at baseband means that 1/f noise in baseband amplifiers may dominate near DC. 1 9-3 1 2 3 ; R e v 1 a ; 9/0 4 KIT ATION EVALU BLE AVAILA C o m ple t e SD A RS R e c eiv er F e a t u re s o Integrated Receiver, Requires Only One SAW Filter To form a c om p l e t e S D A RS ra d io, th e M A X2140 r e q u ir e s o n l y a l o w - n o i s e a m p l i f i e r ( L N A ) , w h i c h c a n b e c o n tr o l l e d b y a b a s e b a n d c o n tr o l l e r . T h e s m a l l n u m b e r o f e x t e rn a l c o m p o n e n t s n e e d e d m a k e s t h e M A X 2 1 4 0b a s e d p l a t f o rm t h e l o w e s t c o s t a n d t h e s m a l l e s t s o l uti o n f or S D A R S . T h e r e c e i v e r i n c l u d e s a s e l f- c o n t a i n e d R F A G C l o o p a n d b a s e b a n d - c o n tr o l l e d I F A G C l o o p , e f f e c t i v e l y p r o vi d in g a tot a l d y n a mi c r a n g e of o v e r 9 2 d B . o Differential I/Q Interface o Bias Supply for External LNAs o Overcurrent Protection o Low-Power Standby Mode o Very Small 44-Pin Thin QFN Package O rd e r i n g I n f o r m a t i o n PART TEMP RANGE PIN-PACKAGE M A X2140 E T H -4 0° C t o + 8 5° C 4 4 T h i n Q F N - E P* *E P = E x p os e d p a d d l e . • In d i v i d u a l f u n c ti o n a l b l o c k s h u t d o w n T h e M A X 2 1 4 0 m i n i m i z e s t h e r e q u ir e m e n t o n t h e b a s e b a n d c o n tr o l l e r . N o c o m p e n s a t i o n o r c a l i b r a t i o n p r o c e d u r e s a r e r e q u ir e d . T h e d e v i c e i s a v a i l a b l e i n a 7 m m  7 m m 4 4- p i n t h i n Q F N p a c k a g e . VCC_BE4 IF2QO- IF2QI- IF2QO+ IF2QI+ QOUT- QOUT+ 43 I2CA1 44 • L o w p a s s filt e rs t u n i n g I2CA2 B l o c k D i a g r a m /P i n C o n f i g u r a t i o n SCL A 2-w ir e i n t e rf a c e (I2 C ™ b u s c o m p a t i b l e ) p ro g r a m s t h e c ir c u i t f o r a w i d e v a ri e t y o f c o n d i t i o n s , p r o v i d i n g f e a t ur e s s u c h a s : • Pro g r a m m a b l e g a i n s o Complete Integrated Frequency Generation SDA C h a n n e l s e l e c ti v it y i s e n s ur e d b y t h e S A W filt e r a n d b y o n- c h i p m o n o lit h i c l o w p a s s filt e rs . T h e fr a c t i o n a l- N P L L a l l o w s a v e ry s m a l l fr e q u e n c y st e p , m a kin g p o s si b l e th e im p l e m e nt a tio n of a n A F C lo o p . A d d itio n a lly , th e r e f e r e n c e is p ro vi d e d b y a n e x t e rn a l X T A L a n d o n- c h i p o s c ill a t or. A r e f e r e n c e b u f f e r o u t p u t i s a l s o p ro v i d e d . o Self-Contained RF AGC Loop 42 41 40 39 38 37 36 35 34 XM TUNER VCC_FE0 1 32 VCCREG RFIN- 3 31 VCC_VCO MAX2140 VCC_FE1 4 Σ ∆ - MOD CHP VCC_FE2 8 27 VCC_A LPF HPF 26 VCC_D /4/8 QUAD AGCPWM 9 25 REFOUT IFIN+ 10 24 XTAL LPF HPF IFIN- 11 13 14 15 16 17 18 19 20 21 22 VCC_BE2 VCC_BE3 VINANT VOUTANT IF2IO- IF2II- IF2IO+ I F 2I I + IOUT- IOUT+ 23 VCC_XTAL 12 VCC_BE1 I 2 C i s a tr a d e m a r k o f P h i l i p s C o r p . P u r c h a s e o f I 2 C c o m p o n e n t s fr o m M a x i m I n t e g r a t e d P r o d u c t s , In c . , or o n e o f it s s u b li c e n s e d A s s o c i a t e d C o m p a n i e s , c o n v e y s a li c e n s e u n d e r t h e P h ili p s I2 C P a t e n t R i g h t s t o u s e t h e s e c o mp o n e n t s i n a n I2 C s y s t e m , p ro v i d e d t h a t t h e s y s t e m c o n f orm s t o t h e I2 C S t a n d a r d S p e c i f i c a t i o n a s d e f i n e d b y P h i l i p s . 29 CPOUT 28 LOCK RFAGC_C 7 2 . 4 G H z IS M R a d i o s PFD 1/R IFOUT- 6 S a t e llit e D i g it a l A u d i o R a d i o S e rv i c e s (S D A R S) 30 VCC_FE3 1/N RF AGC IFOUT+ 5 A p pli c a tio n s 33 VTUNE RFIN+ 2 ACTUAL SIZE 7mm x 7mm ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit...
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