More Information - Wireless Home - Application Notes and Tutorials - EV Kit Software - Technical Support   Abstract: This reference design is a complete RF front-end solution for a GPS receiver using Maxim's MAX2769 GPS receiver chip. The MAX2769 is a low cost, single conversion, low IF GPS receiver that offers two integrated LNAs with different specifications, I/Q channel filters with variable bandwidth and order, and a digital IF output that supports 1-bit and 2-bit operation. This reference design offers high performance, small size, and low BOM cost. Figure 1. GPS reference design features the MAX2769. Important Design Features Dual-Input Uncommitted LNA for Separate Passive and Active Antenna Inputs Integrated Active Antenna Sensor Which Can Autoswitch the Antenna Input The I and Q Channel-Select Filters Can Be Selected as Either Third or Fifth Order Provides 110dB Cascaded Gain and a 1.5dB Cascaded NF in LNA1 Mode The IF Output Is Adjustable in 63 Steps Between 0MHz and 12.5MHz Can Be Used in Preconfigured States that Do not Require Programming Through the 3-wire SPI™ Interface Figure 2. Block diagram for the GPS reference design. Lab Measurements Supply Current Summary VCC = +3.0V, TA = +25°C Parameter Test Conditions Meas. Unit Operating Supply Current Using LNA1 in default and low-current modes 18 mA Receive Summary Operating conditions: VCC = 3V; TA = +25°C, Operating in default mode, PCB trace losses are included. Parameter Test Condition Meas. Unit LNA1 Power Gain Default and low-current modes 18.6 dB LNA1 Noise Figure Default and low-current modes 1.05 dB LNA1 Third-Order Input Intercept Point Default and low-current modes; LNA input to output. P1 = P2 = -30dBm; f1 = 1575MHz, f2 = 1576MHz -1 dBm LNA2 Power Gain Default mode 12.9 dB LNA2 Noise Figure Default mode 1.35 dB LNA2 Third-Order Input Intercept Point Default mode -2 dBm Overall System NF Using LNA1; PGA gain is maximum (CONF3[27:22] is 111111) 1.6 dB Using LNA2; PGA gain is maximum (CONF3[27:22] is 111111) 3.1 IF Out Freq/Gain Range Through System Using LNA1 1575.42MHz in, 4.092MHz out; analog output mode 59 -117 dB 4MHz Offset Rejection 1579.42MHz in, third-order BPF; PGA gain is maximum (CONF3[27:22] is 111111) 32 dB 1579.42MHz in, fifth-order BPF; PGA gain is maximum (CONF3[27:22] is 111111) 51 IF Passband 3dB Bandwidth IF filter center bandwidth 2.6MHz; set bit 4:3 of CONF1 register to 00 2.9 MHz Operating Characteristics Figure 3. Input S11 of the MAX2769 LNA1. Measured by network analyzer at 1575.42MHz. The S11 is -10.4dB. Detailed Description This reference design is a low-cost, single-conversion, low-IF GPS receiver. The design offers more flexibility and performance than its predecessors for a wide range of GPS applications such as mobile handsets, PDA's, embedded PCs, and automotive applications. SPI is a trademark of Motorola, Inc. Related Parts   APP 4279: Sep 22, 2008 MAX2769 Universal GPS Receiver 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 (116kB)  AN4279, AN 4279, APP4279, Appnote4279, Appnote 4279