LNA Optimized for GPS (REP024)
|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.|
Objective: To provide an optimized solution for a GPS LNA using the MAX2641.
By minimizing passive-component size and maximizing cost performance, the MAX2641 LNA provides an optimized solution for a global positioning system (GPS) low-noise amplifier (LNA). Two reference designs were created with the LNA: one using lumped elements and the other transmission lines for the matching circuits. The lumped-element match consists of replacing the input- and output-impedance transformation lines to the LNA with surface-mount coils, resulting in very similar performance with smaller circuit size but extra-parts cost.
LNA gain is 14.7dB with a 1.6dB noise figure (NF) in the 1575MHz band and an IIP3 of -4.3dBm at 3mA ICC. The input match to the LNA is set for a compromise between gamma-opt and conjugate S11, for a -10dB input return loss. The output match and gain depend partly on the inclusion of a short transmission line at the VCC pin (this is also used in the general-purpose EV board).
The MAX2641 is a low-cost LNA operating from a single +2.7V to +5.5V supply. It consumes only 3.5mA of current, while providing a low noise figure, a high gain, a high-input IP3, and an operating frequency range that extends from 1400MHz to 2500MHz. Typical performance for the MAX2641 LNA is a 14.4dB gain, an input of a -4dBm IP3, and a noise figure of 1.3dB at 1900MHz. This LNA is biased internally and designed for use in the cellular, PCS, GPS, and 2.4GHz ISM frequency band.
MAX2641 LNA Test Conditions
- All tests in room temperature
- IIP3 measurements: Pin = -30dBm, Frf = 1575MHz and 1576MHz (GPS)
- PCS LNA input board loss = 0.2dB
- PCS LNA output board loss = 0.2dB
- VCC: 3.0V
MAX2641 LNA Performance Matrix
|DC Supply Current (PCS mode)||
|LNA Rev. Isolation||
|LNA Input Return Loss||
|LNA Output Return Loss||
MAX2641 SiGe LNA (1575MHz) Transmission Line/Lumped-Element Match
MAX2641 LNA Bill of Materials (Transmission Line)
MAX2641 SiGe LNA (1575MHz) Lumped-Element Match
MAX2641 LNA Bill of Materials (Lumped Element)