wiki:Internal/NoiseGenerator/Hardware/WiBo

Version 5 (modified by (none), 18 years ago) ( diff )

Orbit Noise Generator Wireless Board (WiBo)

WiBo is a RF front-end board for Orbit Noise Generator designed around a Maxim, Inc. MAX2829ETN+D radio transceiver chip. Schematic is here. It is manufactured as a 4.00 x 4.00” printed circuit board (PCB).

MAX2829ETN+D Transciever WLAN chip (U1)

The MAX2829 is a complex multifunction radio transceiver chip that incorporates most of the radio functions except for the reference oscillator, baseband I/Q amps, power amps and antenna switches. Please refer to the data sheet and eval board notes for more information than can be given here (also check http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4532). Chip configuration is done by BiBo over the serial bus through the programming pins:

BiBo functionWiBo functionMAX2829 function
RADIO_IO_1*CSChip Select, active low
RADIO_IO_3SCLKSerial ClocK
RADIO_IO_4DINData IN

On power up and without programming the MAX2829 is in a low power “all off” state. The internal LO will lock to 2437 MHz but all input and output signals will be disabled. Current draw will be around 200-240 mA.

RF Control Register (U2)

U2 (74HC595), an 8bit serial in parallel out shift register (http://www.fairchildsemi.com/ds/MM/MM74HC595.pdf). Register programming programming is done with:

BiBo functionWiBo102 function74HC595 function
RADIO_IO 2U2 RCKRegister U2 output
RADIO_IO 3U2 SCKSerial Clock
RADIO_IO 4U2 SERSerial Data In

This register controls five functions, namely, turn on/off of the 2GHz and 5GHz power amps, MAX2829 transmit and receive control signals and the MAX2829 shutdown. The register bit assignment is given in the following table:

01234567Function
1xxxxxxxturn MAX2829 on (/SHDN)
x1xxxxxxturn MAX2829 TX on (TXENA)
xx1xxxxxturn MAX2829 RX on (RXENA)
xxx1xxxx5G PA: 5GHZ power amp on
xxxx1xxx2G PA: 2GHz power amp on
xxxxx1xxSPARE 1 output on
xxxxxx1xSPARE 2 output on
xxxxxxx1SPARE 3 output on
xxxxxxxx1SPARE 4 output on (9th bit)

U2 shares serial clock and data lines (RADIO_IO 3 and RADIO_IO 4) with MAX2829. Note: 0 is the first bit in, so shift in reverse order

LTC 1994 Baseband amps (U3xx, U4xx)

U300, U320 are high speed differential opamps (LTC1994) wired in a 2nd order Butterworth filter with cutoff of 10MHz. They act as reconstruction filters for the output of the AD9862 DACs, which are current mode differential outputs of 0-20mA. These amps also DC offset their output to 1.1 VDC to optimally match the MAX2829 inputs. These amps are enabled only when TXENA is high, thereby saving about 18mA of power.

U400, U420 are buffer amps (gain=1) for the MAX2829 baseband I/Q signal outputs (which have 60k ohm output impedance). These amps provide simple 1st order RC filtering with cutoff F = 6 MHz. U400,U420 DC offset to 2.0VDC before sending the baseband I/Q signals to BiBo’s AD9860. These amps are enabled only when RXENA is high.

uPG2035 Switches (U3, U4, U5)

U3,U4 and U5 make up a switching matrix which offers several antenna diversity options. These are fast switching low-loss DPDT switches.

U5 is the TX output switch which switches 2.4 and 5.6 GHz MAX2829 outputs between two antennas A03 and A04. When LED3 is lit (power up default), the switch is “crossed” so the MAX2829 2.4 GHz output is routed to antenna A03 and 5.6 GHz is routed to A04.

U4 is the RX input switch which switches antennas A01 and A02 to both the 2.4 and 5.6 GHz MAX2829 inputs. When LED1 is lit (power up default), the switch is “crossed” so MAX2829 2.4 GHz input is routed to antenna A02 and 5.6 GHz is routed to A01.

The default design does not incorporate U3. Some soldering and jumpering is required to bring U3 into the mix which enables single antenna operation or maximum spatial antenna seperation (using A01 and A04). No further notes are given here.

AWL6951 Power amp (U6)

The AWL6951 is a dual mode (2.4 and 5.6GHz RF power amp) with enable signals and log detectors for measuring power output. U2 control signals 2G PA and 5G PA should only be enabled one-at-a-time to prevent overheating the chip. AUX_ADC_B1 and AUX_ADC_B2 measure the log detector outputs of the 2G and 5G amps respectively. The following measurements were taken,

  • Pout (2.4GHz) @ 210 mA = 20.5 dBm (right on spec) Vout(logDET) = 0.727 V
  • Pout(5.3GHz) @ 220 mA = 19.0 dBm (right on spec) Vout(logDET) = oops ?
  • Pout(5.9GHz) @ 220 mA = 15.0 dBm (-3 dB off spec) Vout(logDET) = oops ?

Current draw is that of just the power amp and RF power measured at output of SMA connector when 100kHz modulation is transmitted. Otherwise MAX2829 and other circuitry draws about 170mA so total is about 480-500 mA. NOTE! It is VERY easy to over drive the power amp at either 2.4 or 5.6 GHz. This causes an UNUSUALLY high current draw by the power amp, WATCH IT !

Reference Oscillator (U9)

U9 is a 40 MHz VCXO reference oscillator. Measured frequency standard deviation over a 10 second period is about 10 Hz. AUX_DAC_B controls the frequency offset pin. This can adjust any gross frequency offsets that may exist between different WiBos. Resistors R221 and R222 act as a 10:1 divider of AUX_DAC_B so the total frequency deviation may be adjusted up or down by changing R221/2.

The default measured frequency range is approx. 550Hz/volt at 40 MHz. At 2.4GHz the frequency control will be approx. +-42kHz or 330 Hz/step of AUX_DAC_B. At 5.6GHz the frequency control will be approx. +-100kHz or 780 Hz/step.

Antennasa (A01-A04)

Four antennas (A01-A04) are mounted directly to WiBo102 though provision is made for adding SMA connectors and using off-board antennas if necessary. Two antennas are primarily for transmission (Tx) and two for receiving (Rx). Antenna switching is possible for diversity gain. It is also possible to switch all Tx and Rx signals into a single antenna.

PCB

The PCB is a 4.00 x 4.00” FR-4 four-layer controlled impedance stackup board manufactured by Advanced Circuits, Inc.(http://www.4pcb.com/index.htm). For orientation purposes, reference marks are shown along the top (A-D) and right sides (1-4) of the board in one inch increments.

Looking from the top down, the top copper layer is the component side with all the high-frequency RF transmission lines. The dielectric under this layer is 20 mils thick. The structure of the traces is coplanar waveguide with ground (CPWG). A trace width of 30 mils and gap-to-ground of 18 mils provides a very close match to a 50ohm characteristic impedance.

The next copper layer down is all ground plane. The third layer down is a signal layer with predominately vertical traces surrounded by ground plane. The fourth or bottom layer is another signal layer with predominately horizontal traces.

BiBo’s ADC (analog-to-digital conversion) and DAC (digital-to-analog) conversion comes from an Analog Devices AD9860 MxFE processor. Digital RADIO_IO_x signals come from a Xilinx Spartan 3.

RADIO_IO_1/¾ download programming coefficients to the MAX2829.

Assuming the MAX2829 has already been programmed, to enable a TX RF output the user must program a 11001xxx into U2.

NOTE! Do not turn on both the 2GHz and the 5GHz power amps at the same time! ALSO! Do not turn on both the RXENA and TXENA lines (not sure why?).

Connector J3_F and I/O

This is a 40-pin 2mm dual-inline connector which mates BiBo’s control signals, +3.3 VDC power and ground to WiBo102.

WiBo102 functionJ3_F functionpin#pin#J3_F functionWiBo102 function
hi-speed MAX2829 TXBBQ-DACB-213.3VA
hi-speed MAX2829 TXBBQ+DACB+43GND
hi-speed MAX2829 TXBBI-DACA+653.3VA
hi-speed MAX2829 TXBBI+DACA-87GND
phase modulation of U23AUX_DAC_C1093.3VA
ref osc VCXO frequency adjustAUX_DAC_B1211GND
PLL speed up monitorAUX_DAC_A14133.3VA
½ supply voltageAUX_ADC_A1115 GND
RSSI from MAX2829AUX_ADC_A2 1817N/C
2GHz power amp detectorAUX_ADC_B120193.3VD
5GHz power amp detectorAUX_ADC_B22221GND
hi-speed MAX2829 RXI+ADCA+24233.3VD
hi-speed MAX2829 RXI-ADCA_2625GND
hi-speed MAX2829 RXQ+ADCB+28273.3VD
hi-speed MAX2829 RXQ-ADCB-3029GND
MAX2829 /CSRADIO_IO 132313.3VD
U2 RCKRADIO_IO 23433GND
MAX2829 SCLK and U2 SCKRADIO_IO 33635RADIO_IO 8MAX2829 LD (lock=1=LED on)
MAX2829 DIN and U2 SERRADIO_IO 43837RADIO_IO 7U5 switch(straight=0,cross=1)
U3 switch(straight=0,cross=1)RADIO_IO 54039RADIO_IO 6U4 switch(straight=0,cross=1)

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