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
VBATT = +3.6V, VCC = +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, POUT = +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
VBATT = +3.6V, VCC = +2.85V, fRF = 2347MHz, VOUT = 90mVRMS, WiBro signal, RF specs are antenna referred, TA = +25°C
| Parameter | Test Conditions | Measured | Units | |
|---|---|---|---|---|
| DC Offset | I channels | 6.8 | mV | |
| Q channels | 4.5 | |||
| 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 | |
| Attenuation from 0dB to -32dB | 32.1 | |||
| Gain Variation over Temperature | TA = -40°C to +85°C | LNA gain = 0dB | -5.2 | dB |
| LNA gain = -16dB | -5.3 | |||
| LNA gain = -32dB | -3 | |||
| Gain Variation over Frequency | fLO = 2304MHz to fLO = 2396MHz | 0.2 | dB | |
| Sensitivity at Low Supply Current¹ | 64 QAM, ¾ FEC coding rate, 10% EVM at sensitivity | -79.8 | dBm | |
| 16 QAM, ¾ FEC coding rate, 20% EVM at sensitivity | -90.7 | |||
| Sensitivity at Nominal Supply Current¹ | 64 QAM, ¾ FEC coding rate, 10% EVM at sensitivity | -80.4 | dBm | |
| 16 QAM, ¾ FEC coding rate, 20% EVM at sensitivity | -91.3 | |||
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, VCC = +2.85V, fRF = 2347MHz, VIN = 90mVRMS, 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 | fLO = 2304MHz to fLO = 2396MHz | 1.9 | dB |
| Transit EVM | 16 QAM, ¾ FEC coding rate, POUT = +24dBm, meeting spectral mask | 4.1 | % |
| Transit EVM | 16 QAM, ¾ FEC coding rate, POUT = +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
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