WiBro Reference Design with the MAX2837

Figure 1.The WiBro reference design features the MAX2837 direct-conversion transceiver

Important Design Features:

Complete RF-to-Baseband WiBro Solution
+23dBm Transmit Power at 5% EVM and Meets Spectral Mask Requirements
-79dBm Receive Sensitivity at 10% EVM
60dB of Transmit Gain-Control Range
94dB of Receive Gain-Control Range
Optimized Low-Current Modes

Figure 2. Block diagram for the WiBro reference design

Lab Measurements

Supply Current Summary

V_BATT= +3.6V, V_CC = +2.85V, TA = +25°C


Parameter	Test Conditions	Measured	Units
Shutdown Supply Current	MAX2837 and PA in shutdown; regulators and VCTCXO still active	1.8	mA
Idle Supply Current	MAX2837 in idle mode; PA in shutdown; regulators and VCTCXO active	34.8	mA
Transmit Supply Current	16 QAM, ¾ FEC coding rate, P_OUT = +24dBm, EVM = 5%	392.6	mA
Receive Supply Current In	Low-current mode	79	mA
Receive Supply Current In	Nominal current mode	96.2	mA

Receive Summary

V_BATT = +3.6V, V_CC = +2.85V, f_RF = 2347MHz, V_OUT = 90mVRMS, WiBro signal, RF specs are antenna referred, T_A = +25°C

Parameter	Test Conditions		Measured	Units
DC Offset	I channels		6.8	mV
DC Offset	Q channels		4.5	mV
VGA Gain Step Size			2	dB
Receive Gain-Control Range	Max to min VGA gain		61.7	dB
Receive LNA Gain Step	Attenuation from 0dB to -16dB		-15.9	dB
Receive LNA Gain Step	Attenuation from 0dB to -32dB		32.1	dB
Gain Variation over Temperature	T_A = -40°C to +85°C	LNA gain = 0dB	-5.2	dB
		LNA gain = -16dB	-5.3
		LNA gain = -32dB	-3
Gain Variation over Frequency	f_LO = 2304MHz to f_LO = 2396MHz		0.2	dB
Sensitivity at Low Supply Current¹	64 QAM, ¾ FEC coding rate, 10% EVM at sensitivity		-79.8	dBm
Sensitivity at Low Supply Current¹	16 QAM, ¾ FEC coding rate, 20% EVM at sensitivity		-90.7	dBm
Sensitivity at Nominal Supply Current¹	64 QAM, ¾ FEC coding rate, 10% EVM at sensitivity		-80.4	dBm
Sensitivity at Nominal Supply Current¹	16 QAM, ¾ FEC coding rate, 20% EVM at sensitivity		-91.3	dBm

¹Rx EVM limits are at BB I/Q Rx outputs, and are given in the IEEE® 802.16e specification Table 338, "Receiver SNR Assumptions." The assumption is that this EVM for this modulation rate is sufficient to meet 1e-6 BER.

Transmit Summary

VBATT = +3.6V, V_CC = +2.85V, fRF = 2347MHz, V_IN = 90mV_RMS, WiBro signal, RF specs are antenna referred, TA = +25°C


Parameter	Test Conditions	Measured	Units
LO Leakage	Q = 640/352µA, I = 576/416µA	-39.6	dBc
Sideband Suppression	I/Q phase = -0.5°	-52.5	dBc
Transmit Power-Control Range	Including PA Gain Step	64.5	dB
Gain Variation over Frequency	f_LO = 2304MHz to f_LO = 2396MHz	1.9	dB
Transit EVM	16 QAM, ¾ FEC coding rate, P_OUT = +24dBm, meeting spectral mask	4.1	%
Transit EVM	16 QAM, ¾ FEC coding rate, P_OUT = +23dBm, meeting spectral mask	3.5	%

Transit Operating Characteristics

Figure 3. Output EVM for the reference design. The WiBro reference design delivers more than 23dBm of output power at the antenna, while meeting the required EVM specification of 5.5% over the entire 2.3GHz to 2.4GHz band

Figure 4. Transmit capture for the reference design. This capture shows the transmit spectrum, EVM constellation, and spectrum of the reference design at 23dBm of output power at the antenna. Measured EVM = 3.9% at 23dBm at 2.347GHz

Figure 5. 2.35GHz, 10MHz spectral mask using ETSI-EN-301-021F mask. This capture shows that the WiBro reference design meets the ETSI-EN-301-021F spectral mask at 23dBm of output power at the antenna.

Figure 6. Receive gain characteristic across the 2.3GHz to 2.4GHz band. Gain variation over frequency is less than 0.2dB. Gain-control range, not including LNA gain steps, is 62dB, approximately 2dB per gain step.

Figure 7. Gain characteristic across three LNA gain attenuations and temperatures. Gain variation over temperature for LNA attenuations 0dB and -16dB is approximately 5dB, and roughly 3dB for -32dB gain attenuation.

Detailed Description

The WiBro reference design includes the following components: MAX2837 direct-conversion transceiver, Micro Mobio MMPA372X PA, MAX8510 regulators, Murata balanced-to-unbalanced SAW bandpass filters, Hexawave HWS466 SPDT Tx/Rx switch, and Vishay Si1563DH load switch.

The MAX2837 is a single-chip, wideband, direct-conversion transceiver designed for 2.3GHz to 2.7GHz WiBro and WiMax radios. The transceiver is fully equipped with an on-chip broadband VCO, fast settling sigma delta RF synthesizer, crystal oscillator, programmable lowpass filters, proprietary DC offset cancellation, I/Q error and carrier leakage detection circuits. The MAX2837 offers less than 1.4% of transmit EVM at -3dBm driver output power, and receive sensitivity better than -79dBm. When integrated with the MMPA372X PA and Murata BPF, the reference design can deliver at least 23dBm of output power at the antenna, while meeting WiBro EVM and spectral-mask requirements with margin