| 9 | | A. PCB |
| | 9 | ||!BiBo function||WiBo102 function||MAX2829 function|| |
| | 10 | ||RADIO_IO_1||*CS||Chip Select, active low|| |
| | 11 | ||RADIO_IO_3||SCLK||Serial ClocK|| |
| | 12 | ||RADIO_IO_4||DIN||Data IN|| |
| | 13 | |
| | 14 | 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. |
| | 15 | |
| | 16 | === RF Control Register (U2) === |
| | 17 | |
| | 18 | U2 (74HC595), an 8bit serial in parallel out shift register (http://www.fairchildsemi.com/ds/MM/MM74HC595.pdf). Register programming programming is done with: |
| | 19 | |
| | 20 | ||!BiBo function||WiBo102 function||74HC595 function|| |
| | 21 | ||RADIO_IO 2||U2 RCK||Register U2 output|| |
| | 22 | ||RADIO_IO 3||U2 SCK||Serial Clock|| |
| | 23 | ||RADIO_IO 4||U2 SER||Serial Data In|| |
| | 24 | |
| | 25 | 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: |
| | 26 | |
| | 27 | ||01234567||Function|| |
| | 28 | ||1xxxxxxx||turn MAX2829 on (/SHDN)|| |
| | 29 | ||x1xxxxxx||turn MAX2829 TX on (TXENA)|| |
| | 30 | ||xx1xxxxx||turn MAX2829 RX on (RXENA)|| |
| | 31 | ||xxx1xxxx||5G PA: 5GHZ power amp on|| |
| | 32 | ||xxxx1xxx||2G PA: 2GHz power amp on|| |
| | 33 | ||xxxxx1xx||SPARE 1 output on|| |
| | 34 | ||xxxxxx1x||SPARE 2 output on|| |
| | 35 | ||xxxxxxx1||SPARE 3 output on|| |
| | 36 | ||xxxxxxxx1||SPARE 4 output on (9th bit)|| |
| | 37 | |
| | 38 | U2 shares serial clock and data lines (RADIO_IO 3 and RADIO_IO 4) with MAX2829. |
| | 39 | |
| | 40 | Note: 0 is the first bit in, so shift in reverse order |
| | 41 | |
| | 42 | === LTC 1994 Baseband amps (U3xx, U4xx) === |
| | 43 | |
| | 44 | 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. |
| | 45 | These amps are enabled only when TXENA is high, thereby saving about 18mA of power. |
| | 46 | |
| | 47 | 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. |
| | 48 | |
| | 49 | === uPG2035 Switches (U3, U4, U5) === |
| | 50 | |
| | 51 | U3,U4 and U5 make up a switching matrix which offers several antenna diversity options. |
| | 52 | These are fast switching low-loss DPDT switches. |
| | 53 | |
| | 54 | 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. |
| | 55 | |
| | 56 | 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. |
| | 57 | |
| | 58 | 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. |
| | 59 | |
| | 60 | === AWL6951 Power amp (U6) === |
| | 61 | |
| | 62 | 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, |
| | 63 | |
| | 64 | * Pout (2.4GHz) @ 210 mA = 20.5 dBm (right on spec) Vout(logDET) = 0.727 V |
| | 65 | |
| | 66 | * Pout(5.3GHz) @ 220 mA = 19.0 dBm (right on spec) Vout(logDET) = oops ? |
| | 67 | |
| | 68 | * Pout(5.9GHz) @ 220 mA = 15.0 dBm (-3 dB off spec) Vout(logDET) = oops ? |
| | 69 | |
| | 70 | 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. |
| | 71 | |
| | 72 | 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 ! |
| | 73 | |
| | 74 | === Reference Oscillator (U9) === |
| | 75 | |
| | 76 | U9 is a 40 MHz VCXO reference oscillator. |
| | 77 | Measured frequency standard deviation over a 10 second period is about 10 Hz. |
| | 78 | |
| | 79 | 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. |
| | 80 | |
| | 81 | The default measured frequency range is approx. 550Hz/volt at 40 MHz. |
| | 82 | At 2.4GHz the frequency control will be approx. +-42kHz or 330 Hz/step of AUX_DAC_B. |
| | 83 | At 5.6GHz the frequency control will be approx. +-100kHz or 780 Hz/step. |
| | 84 | |
| | 85 | === Antennasa (A01-A04) === |
| | 86 | 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. |
| | 87 | |
| | 88 | == PCB == |
| | 89 | |
