MAX2388 Front-End IC for WCS Application at 2.3GHz RF and 220MHz IF

Jun 15 2004

Abstract

The MAX2388 front-end IC combines an LNA and a mixer onto one chip. With proper matching, this IC can be used at the WCS band. For this report an RF frequency of 2.3GHz was used with an IF frequency of 220MHz. Traditional receiver measurements were made on the device such as gain, noise figure, IIP3, IIP2, and LO leakage.

General Description

The MAX2388 is a member of a family of receiver front-end devices that also includes the MAX2387 and MAX2389. These devices integrate a low-noise amplifier and a high-linearity downconversion mixer in an ultra-small package, while keeping noise figure at a low level. The MAX2387 and MAX2388 also incorporate an on-chip LO buffer. The MAX2389 omits this LO buffer to minimize current consumption.

The MAX2387 and MAX2388 have been designed for optimal mixer performance with -10dBm LO drive. The MAX2389 mixer performance is optimized for -4dBm typical drive at the LO input port. An external bias resistor controls the tradeoff between mixer 3rd-order nonlinearity and current consumption.

For all devices, both high-gain and low-gain LNA states are featured. The MAX2387 has a 32dB gain step while the MAX2388 and MAX2389 both have an 18dB gain step. A shutdown mode is also included so the IC can be powered down during idle periods, thus increasing battery life.

Although initially designed for the 2110MHz to 2170MHz WCDMA band, these receivers exhibit excellent performance over other frequency ranges as well.

Measured Performance

The measurement data presented here were taken on a standard MAX2388 evaluation kit. The LNA input and output were retuned to be centered at 2315MHz. The mixer matching circuits were tuned for an RF input of 2315MHz, an IF output of 220MHz and low-side LO injection.

Test Conditions

V_CC = 2.85V
RF input power = -30dBm
RF frequency = 2315MHz; LO frequency = 2095MHz (IF = 220MHz)
Two-tone spacing = 1MHz
LO power = -10dBm

Table 1. LNA Measurements
Parameter	High Gain	Low Gain	Units
Gain	14.0	3.7	dB
NF	2.35	7.5	dB
IIP3	5.8	3.5	dBm
S11	-12.5	-4.8	dB
S22	-15.8	-7.0	dB
S12	-24.9	-13.5	dB
I_CC	10.5	7.3	mA

Table 2. Mixer Measurements
Parameter	High Gain	Low Gain	Units
Gain	7.5	7.3	dB
NF	8.5	7.5	dB
IIP3	5.5	0.0	dBm
IIP2 (Note 1)	27	26.5	dBm
LO leakage at IF port	-17.4	-20.9	dBm
LO leakage at LNA input port	-49.7	-53.9	dBm

Note 1: IIP2 was measured by using the half-IF approach. Using this method the interferer tone was applied at 2205MHz.

LNA S-Parameters

S-parameters for the LNA were measured on a MAX2388 EV kit. The trace lengths from the SMA connectors to the IC pins were de-embedded using the port extension feature of the Network Analyzer.