
Data Sheet HMC6300
Rev. C | Page 13 of 25
THEORY OF OPERATION
An integrated frequency synthesizer creates a low phase noise LO
between 16.3 GHz and 18.3 GHz. The step size of the synthesizer
equates to 250 MHz steps at RF when used with a 71.42857 MHz
reference crystal or 500 MHz if used with a 142.857 reference
crystal. To support IEEE channels (ISM band) with a 540 MHz
step size, use a 154.2857 MHz reference crystal.
If the chip is configured for I/Q baseband input, these signals
are quadrature modulated onto an 8 GHz to 9.1 GHz sliding IF
using the synthesized LO divided by two. There are also options
to input AM/FM/FSK/MSK waveforms directly to the on-chip
IF modulators. The IF signal is then filtered and amplified with
14 dB of variable gain, then mixed with three times the LO
frequency to upconvert to an RF frequency between 57 GHz
and 64 GHz.
Integrated notch filters attenuate the lower mixing product at
40 GHz to 46 GHz. Three RF amplifier stages provide gain to
allow up to 15 dBm of linear and differential output power with
22 dB of variable gain. IF and RF gain can be controlled using
either analog voltages or the digital SPI. For lower power consump-
tion, half of the power amplifier can be disabled to run in a
single-ended configuration; this drops the output power by 3 dB.
An on-chip power detector can be used to monitor the rms
output power. The detector output pin (DETOUT) is connected
through an external resistor to the RFB pin. A resistor value of
1.15 kΩ is recommended for optimal coverage up to the P1dB
point of the transmitter. The REFOUT pin provides the reference
voltage for the detector, and the difference between DETOUT and
REFOUT is used to estimate the output power.
The phase noise and quadrature balance of the on-chip synthesizer
is sufficient to support up to 64 QAM modulation. For higher
order modulation (up to 256 QAM or less than 250 MHz step
size), the HMC6300 can be operated using an external LO.
The HMC6300 transmitter is ideal for FDD operation together
with the HMC6301 receiver chip. However, both devices can
support TDD operation by enabling and disabling the circuits.
All of the enables are placed in register array, four of which
allow for full chip enable or disable in one SPI write.
There are no special power sequencing requirements for the
HMC6300; all voltages are to be applied simultaneously.
REGISTER ARRAY ASSIGNMENT AND SERIAL
INTERFACE
The register arrays for both the transmitter and receiver are
organized into 32 rows of 8 bits. Using the serial interface, the
arrays are written or read one row at a time, as shown in Figure 17
and Figure 18, respectively. Figure 17 shows the sequence of
signals on the ENABLE, CLK, and DATA lines to write one
8-bit row of the register array. The ENABLE line goes low, the
first of 18 data bits (Bit 0) is placed on the DATA line, and 2 ns
or longer after the DATA line stabilizes, the CLK line goes high
to clock in Data Bit 0. The DATA line should remain stable for
at least 2 ns after the rising edge of CLK.
A write operation requires 18 data bits and 18 clock pulses, as
shown in Figure 17. The 18 data bits contain the 8-bit register
array row data (LSB is clocked in first), followed by the register
array row address (ROW 0 through ROW 23, 000000 to 001111,
LSB first), the read/write bit (set to 1 to write), and finally the
Tx Chip Address 110, LSB first).
The Tx IC supports a serial interface running up to several
hundred megahertz, and the interface is 1.2 V CMOS levels.
Note that the register array row address is six bits, but only four
are used to designate 32 rows, the two MSBs are 0.
After the 18th clock pulse of the write operation, the ENABLE
line returns high to load the register array on the IC; prior to
the rising edge of the ENABLE line, no data is written to the
array. The CLK line should have stabilized in the low state at
least 2 ns prior to the rising edge of the ENABLE line.