Abstract: This application note presents the schematic and bill of materials to optimize the MAX2108 satellite tuner for 950MHz to 1750MHz operation. Rapid engineering prototypes are real circuits that Maxim application engineers have built and measured in our labs. They can provide a starting point for new RF designs. They are not available as evaluation kits. Additional Information: Wireless Product Line Page Quick View Data Sheet for the MAX2108 Applications Technical Support Objective: To optimize the MAX2108 direct-conversion tuner for operation from 950MHz to 1750MHz. A reference evaluation board has been developed and tested for the MAX2108 satellite, digital video broadcasting (DVB) tuner IC. Important board design features include a transmission-line input match, a pair of 0.1dB ripple differential Tchebychev lowpass I and Q filters at 35MHz cutoff, and DC voltage regulators. A pair of MAX4145 video op amps acts as baluns to terminate the lowpass filters and drive the 50Ω output test ports. The board was laid out for easy testing and modification using FR4 material for low cost. To provide for the op-amp baluns, ± 8VDC is required at the board input. The result of the design was that all data sheet targets were met, including greater than 50dB gain range, IIP3 and IIP2 of +8dBm and +14dBm over the band, and NF of 10dB to 13dB over the band. An excellent reverse isolation was obtained of -87dBm LO power measured at the RF input port, which was achieved through the use of an LO balun and carefully planned layout. The MAX2108 is a low-cost direct-conversion tuner IC designed for use in digital, direct-broadcast satellite (DBS) television set-top box units and microwave links. Its direct-conversion architecture reduces system cost, compared to devices with IF-based architectures. The MAX2108 directly tunes L-band signals to baseband using a broadband I/Q downconverter offering typically +8dBm IIP3. The operating frequency range spans from 950MHz to 2150MHz. The MAX2108 includes a low-noise amplifier with gain control, two downconverter mixers with output buffers, a 90-degree quadtrature generator, and a divide-by-32/33 prescaler. Specifications for Optimized Operation at 950MHz to 1750MHz Item Requirements Qualifications Lab Results PCB Material FR-4, four layers Two-layer FR-4 eval PCB FR-4 Circuit Area N/R See test eval PCB - Shielding N/R - - Connectors F-type for tuner input, SMA for LO F-type for tuner input, SMA for LO - Vcc +5.0V DC for tuner +8.0V, and -8.0V DC for linear regulators +8.0V DC, -8.0V DC (Note 1) Icc TBD TBD 128mA @ +8.0V, 22mA @ -8.0V Frequency 950MHz to 1750MHz - 950MHz to 1750MHz RF Power In -20dBm to -70dBm - -20dBm to -70dBm Gain-Control Range 50dB - >50dB IIP3 +8dBm - +6dBm (Note 2) IIP2 +14dBm - +25dBm (Note 3) Noise Figure 10dB - 11dB @ 950MHz, 10dB @ 1300MHz, 13.4dB @ 1750MHz (Note 4) Input-Return Loss -10dB -7.5dB min from 950MHz to 1750MHz -7.5dB min from 950MHz to 1750MHz LO Drive Level -10dBm -10dBm -10dBm LO Leakage at RFIN Port -100dBm - -87dBm @ 950MHz, -87dBm @ 1300MHz, -76dBm @ 1750MHz (Note 4) Baseband Filter fc Not required 0.1dB Chebyshev fc = 35MHz 0.1dB Chebyshev fc = 35MHz Notes: 1. Linear regulators are on-board. MAX2108 DC operating voltage is +5.0V. MAX4145 diff. line-receiver DC operating voltages are ±5.0V. 2. Prf in = -20dBm per tone, GC set to +3.4V, f1rf in = 1749MHz, f2rf in = 1751MHz, fLO = 1740MHz. 3. Prf in = -20dBm per tone, GC set to +3.4V, f1rf in = 1200MHz, f2rf in = 2150MHz, fLO = 951MHz, f baseband = 1MHz. 4. GC set to +3.6V. Schematic (PDF, 89k) Bill of Materials Related Parts   APP 1986: Aug 22, 2002 MAX2108 Direct-Conversion Tuner IC Full Data Sheet (PDF, 180kB) Free Samples Automatic Updates Would you like to be automatically notified when new application notes are published in your areas of interest? Sign up for EE-Mail™. We Want Your Feedback!   Download, PDF Format (49kB)  AN1986, AN 1986, APP1986, Appnote1986, Appnote 1986