GPS receiver RF chip There are currently many commercial IF-baseband chip solutions for GPS applications. Many companies choose to design their own ASIC chips with independent property rights, but they lack the RF-IF front-end chip that down-converts the transmitted GPS frequency to a low IF frequency. Maxim has produced several RF chips, providing excellent options for accomplishing these tasks. Mini Air Purifier,Mini Air Filter,Air Purifier Portable Mini,Mini Purifier CIXI KYFEN ELECTRONICS CO.,LTD, , https://www.kyfengroup.com
The MAX2741 / MAX2742 / MAX2744 / MAX2745 are high-performance CMOS single-chip GPS front-end downconverters. These devices that have been put on the market consume very low power consumption and do not require expensive IF SAW filters or large-sized separate IF bandpass filters. All devices include low-noise amplifiers, mixers, BPFs, automatic gain control amplifiers, local oscillator synthesizers, clock buffers, and digital samplers. The product selection guide is shown in Table 1. For more information about these products, please visit the following data sheets and application note links.
Table 1. CMOS GPS RF front-end receiver IC selection guide Part Supply Voltage (V) Supply Current (mA) Reference Clock (MHz) IF Frequency (MHz) Conversion Gain (dB) Noise Figure (dB) IIP3 (dBm) MAX2741 2.7 to 3.0 30 2 to 26 37.38 (first)
3.78 (second) 32 (first)
47 (second) 4.7 (first)
12 (second) -30 (first)
-36 (second) MAX2742 2.4 to 3.6 14 18.414 1.023 117 4.5 -32 MAX2744 2.4 to 3.6 twenty one 16.368
32.736 4.092 120 3.5 -25 MAX2745 2.4 to 3.6 twenty one 16.368
32.736 4.092 120 3.5 -25
The MAX2654 / MAX2655 1575MHz SiGe low noise amplifier has high gain, low noise, and high linearity. These two RF chips integrate a 50Ω output matching network, reducing the number of external components. The MAX2654 RF chip provides a gain of 15.1dB, a noise figure of 1.5dB, and an input third-order intermodulation point (IIP3) of -7.8dBm. To improve linearity, the MAX2655 RF chip provides 14.1dB gain, 1.45dB noise figure, and adjustable IIP3 performance from + 2.2dBm to + 3.8dBm. The supply current of MAX2654 is lower 5.8mA, while the supply current of MAX2655 is adjustable from 5.9mA to 10.1mA. Both chips also have a 0.1µA low-power shutdown mode. The MAX2641 SiGe LNA is another excellent choice, offering 15.7dB of gain, 1.2dB (at 1575MHz) ultra-low noise figure, and + 1.4dBm IIP3. The supply current is lower 3.5mA. The MAX2641 does not provide a low-power shutdown mode and an on-chip integrated output matching network.
Maxim has not yet launched an independent GPS LNA that supports gain step control, but it can use the MAX2563 to tune it in the GPS band to obtain an excellent solution. The MAX2563 is a SiGe LNA designed for the US PCS and European DCS receiving bands. After replacing the matching components, the MAX2563 can provide a gain of 19.2dB, a noise figure of 1.57dB, and an IIP3 index of -5.2dBm. For more information, please refer to Application Note 3248: The MAX2653 LNA has gain step control and can be retuned for GPS applications.
The MAX2680 / MAX2681 / MAX2682 are a series of SiGe down-conversion mixers with an acceptable RF frequency range of 2.5GHz to 400MHz. This series is best suited for GPS applications at 1575MHz. The IF output is tunable from 10MHz to 500MHz IF frequency. The performance of MAX2680, MAX2681 and MAX2682 is shown in the table below:
Table 2. GPS SiGe downconverter chip selection guide Part Supply Current (mA) Frequency 900MHz 1950MHz IIP3 (dBm) NF (dB) Gain (dB) IIP3 (dBm) NF (dB) Gain (dB) MAX2680 5.0 -12.9 6.3 11.6 -8.2 8.3 7.6 MAX2681 8.7 -6.1 7.0 14.2 +0.5 11.1 8.4 MAX2682 15.0 -1.8 6.5 14.7 +4.4 10.2 10.4
The following block diagram summarizes the main performance characteristics of Maxim's various GPS RF chips. 
RF chip for GPS receiver