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RF2938
2
Typical Applications
* Wireless LANs * Wireless Local Loop * Secure Communication Links * Inventory Tracking * Wireless Security * Digital Cordless Telephones
2.4GHZ SPREAD-SPECTRUM TRANSCEIVER
Product Description
The RF2938 is a monolithic integrated circuit specifically designed for direct-sequence spread-spectrum systems operating in the 2.4GHz ISM band. The part includes a direct conversion from IF receiver, quadrature demodulator, I/Q baseband amplifiers with gain control and RSSI, on-chip programmable baseband filters, dual data comparators. For the transmit side, a QPSK modulator and upconverter are provided. The design reuses the IF SAW filter for transmit and receive reducing the number of SAW filters required. Two cell or regulated three cell (3.6V maximum) battery applications are supported by the part. The part is also designed to be part of a 2.4GHz chip set consisting of the RF2444 LNA/Mixer and one of the many RFMD high efficiency GaAs HBT PA's and a dual frequency synthesizer. Optimum Technology Matching(R) Applied
Si BJT GaAs HBT SiGe HBT
BW CTRL RX VGC DCFB Q VREF 1 VREF 2 VCC2 VCC3 NC
9.00 + 0.20
0.10 0.00
-A-
0.50 9.00 + 0.10 4.57 + 0.10 sq.
0.22 + 0.05 7.00 + 0.10 sq.
Dimensions in mm
7 MAX 0 MIN 1.00 + 0.10 0.60 + 0.15
Exposed pad protrusion 0.0000 to 0.0127 (see note 4).
0.17 MAX.
NOTES: 0.10 1. Shaded lead is Pin 1. 2. Lead coplanarity - 0.08 with respect to datum "A". 3. Leadframe material: EFTEC 64T copper or equivalent, 0.127 mm (0.005) thick. 4. Solder plating (85/15) on exposed area.
Package Style: TQFP-48 EDF, 9x9
uSi Bi-CMOS
NC 48 NC NC PD RX EN TX EN VCC1 RX IF IN TX IF IN VCC9 TX VGC IF LO VCC8 1 2 3 RX 4 47 46
GaAs MESFET Si CMOS
DCFB I RSSI NC
Features
* 45MHz to 500MHz IF Quad Demod
36 35 34 33 NC NC RXQ DATA Q OUT RXI DATA I OUT VCC4 TXQ DATA TXQ BP TXI DATA TXI BP IF1 OUT+
11
TRANSCEIVERS
45
44
43
42
41
40
39
38
37
* On-Chip Variable Baseband Filters * Quadrature Modulator and Upconverter * 2.7V to 3.6V Operation * Part of 2.4GHz Radio Chipset * 2.4GHz PA Driver
I
5
Q
32 31 30 29
I
6 7 8 9 10 11 12 13 NC 14 RF OUT 15 RF OUT 16 VCC6 17 NC 18 PA IN 19 NC 20 VCC5 21 RF LO 22 RF OUT 23 IF1 OUT24 NC 2
+45 -45
RX_EN
TX_EN
TX
Q
28 27 26 25
Ordering Information
RF2938TR13 RF2938 PCBA 2.4GHz Spread-Spectrum Transceiver (Tape & Reel) Fully Assembled Evaluation Board
Functional Block Diagram
RF Micro Devices, Inc. 7628 Thorndike Road Greensboro, NC 27409, USA
Tel (336) 664 1233 Fax (336) 664 0454 http://www.rfmd.com
Rev A8 010418
2-1
RF2938
Absolute Maximum Ratings Parameter
Supply Voltage Control Voltages Input RF Level LO Input Levels Operating Ambient Temperature Storage Temperature Moisture Sensitivity
Rating
Unit
VDC VDC dBm dBm C C
Refer to "Handling of PSOP and PSSOP Products" on page 16-15 for special handling information. Refer to "Soldering Specifications" on page 16-13 for special soldering information.
-0.5 to +3.6 -0.5 to +3.6 +12 +5 -40 to +85 -40 to +150 JEDEC Level 5 @ 220C
Caution! ESD sensitive device.
RF Micro Devices believes the furnished information is correct and accurate at the time of this printing. However, RF Micro Devices reserves the right to make changes to its products without notice. RF Micro Devices does not assume responsibility for the use of the described product(s).
Parameter
Overall Receiver
RX Frequency Range Cascaded Voltage Gain Cascaded Noise Figure Cascaded Input IP3 Cascaded Input IP3 RSSI Dynamic Range RSSI Output Voltage Compliance IF LO Leakage Quadrature Phase Variation Quadrature Amplitude Offset Quadrature Amplitude Variation
Specification Min. Typ. Max.
Unit
Condition
T=25 C, VCC =3.3V, Freq=280MHz, RBW =10k
45 8 to 93 5 30 105 60 1.1 to 2.3 -68 2 +0.25 0.25 43 5 230-j400 75-j350 -68 -8 3 3 30 500 1.7 1 10 15 400 >80 20
500
MHz dB dB dBV dBV dB V dBm dB dB dB dB dBm dBm % % dB mVPP V
5
Dependent upon RX VGC At maximum gain. VGC <1.2V VGC>2.0V At VGC =1.4V Maximum RSSI is 2.5V or VCC -0.3, whichever is less. VGC =1.4V f=280MHz, LO Power=-10dBm With expected LO amplitude and harmonic content. R1=270k. Q>I
+0.5
IF AMP and Quad Demod
11
TRANSCEIVERS
Gain Control Range Noise Figure IF Input Impedance Input IP3
VGC <1.2V max gain, VGC>2.0V=min gain Single Sideband Single ended. 280MHz Single ended. 374MHz VGC <1.2V VGC >2.0V At maximum gain setting At minimum gain setting VGC <1.2V=max gain, VGC >2.0V=min gain RL >5k, CL <5pF
RX Baseband Amplifiers
THD Gain Control Range Output Voltage DC Output Voltage
RX Baseband Filters
Baseband Filter 3dB Bandwidth Passband Ripple Baseband Filter 3dB Frequency Accuracy Group Delay Group Delay Baseband Filter Ultimate Rejection Output Impedance 35 0.1 30 MHz dB % ns ns dB 5th order Bessel LPF. Set by BW CTRL
At 35MHz, increasing as bandwidth decreases. At 2MHz.
Designed to drive>5k, <5pF load.
2-2
Rev A8 010418
RF2938
Parameter
Data Amplifiers
Bandwidth Gain (Limiting mode) Rise and Fall Time Logic High Output Logic Low Output Hysteresis 40 60 2 VCC 30 5 0.3 MHz dB ns V V mV Open Loop. 5pF load. Source Current 1mA Sink Current 1mA.
Specification Min. Typ. Max.
Unit
Condition
VCC -0.3V
Transmit Modulator and LPF
Filter Gain Baseband Filter 3dB Bandwidth Passband Ripple Group Delay Group Delay Ultimate Rejection Input Impedance Input AC Voltage Input DC Offset Requirement IF Frequency Range Output Impedance I/Q Phase Balance I/Q Gain Balance Conversion Voltage Gain Output P1dB Carrier Output Harmonic Outputs 0 1 15 400 >80 3 1.6 45 1.7 2 2 0.50.25 1.1 -6 -30 -30 200 1.8 500 5 1.0 35 0.1 dB MHz dB ns ns dB k mVp-p V MHz k dB V/V dBm dBm dBc Any setting 5th order Bessel LPF, Set by BW CTRL At 35MHz, increasing as bandwidth decreases. At 2MHz. Single ended Linear, Single ended. For correct operation. Open Collector when TX on, hi-Z when off
With Current Combination into 50 singleended load With Current Combination into 50 singleended load Without external offset adjustments. 280MHz
Transmit VGA and Upconverter
VGA Gain Range VGA Input Voltage Range VGA Gain Sensitivity VGA Input Impedance RF Mixer Output Impedance VGA/Mixer Conversion Gain VGA/Mixer Output Power VGA/Mixer Output Power 17 1.0 to 2.0 17 230-j400 75-j350 50 +10 to +27 -9 -4 dB V dB/V dB dBm dBm Positive Slope 280MHz 374MHz With matching elements. With 50 match on the output. 1dB compression - Single Side Band, TX GC=1.0V 1dB compression - Single Side Band, TX GC=2.0V
11
TRANSCEIVERS
Rev A8 010418
2-3
RF2938
Parameter
Transmit Power Amp
Linear Output Power Gain Output P1dB Output Impedance Input IP3 Input Impedance 6 23 12 50 0 50 VCC -0.3V -0.3 0 >1 1.8 200 2 330 1.33 50 VCC +0.3V 0.3 dBm dB dBm dBm V V M s ns s ns ms s Voltage supplied to the input, not to exceed 3.6V Voltage supplied to the input. <8pF on RSSI output. Full step in gain, to 90% of final output level. I/Q output VALID To IF output VALID To I/Q output VALID To IF output VALID The IF LO is divided by 2 and split into quadrature signals to drive the frequency mixers. f=560MHz peak (2x IF Frequency) f=2.16GHz untuned.
Specification Min. Typ. Max.
Unit
Condition
Power Down Control
Logical Controls "ON" Logical Controls "OFF" Control Input Impedance RSSI Response Time RX VGC Response TIme RX EN Response TIme TX EN Response TIme VPD to RX Response TIme VPD to TX Response TIme
IF LO Input
Input Impedance Input Power Range Input Frequency -15 90 1050-j1200 -10 0 1000 dBm MHz dBm MHz V A mA mA mA mA
RF LO Input
Input Impedance Input Power Range Input Frequency 33-j110 -15 2000 2.7 3.3 1 48 65 70 110 95 105 115 0 2400 3.6
Power Supply
11
TRANSCEIVERS
Voltage Total Current Consumption Sleep Mode Current PA Driver Current RX Current BW (MHz) 0-11 12-20 20-30 TX Current BW (MHz) 0-11 12-20 20-30
VCC =3.3V, Baseband BW 1MHz to 40MHz PD=0, RX EN=1, TX EN =1
Excluding PA Driver mA mA mA
2-4
Rev A8 010418
RF2938
Pin 1 2 3 Function NC NC PD Description
No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results. No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results. This pin is used to power up or down the transmit and receive baseband sections. A logic high powers up the quad demod mixers, TX and RX GmC LPF's, baseband VGA amps, data amps, and IF LO buffer amp/ phase splitter. A logic low powers down the entire IC for sleep mode. Also, see State Decode Table. Enable pin for the receiver 15dB gain IF amp and the RX VGA amp. Powers up all receiver functions when PD is high, turns off the receiver IF circuits when low. Also, see State Decode Table. This pin is used to enable the transmit upconverter, buffer amps, 15db IF amp, quad mod mixers, TX LO buffer, TX VGA, and PA driver. TX EN is active low, when TX EN <1V, the transmit circuit is active if PD is high. A logic high (TX EN >2V) disables the transmit IF/RF circuitry and quad mod. Also, see State Decode Table. Power supply for RX VGA amplifier, IC logic and RX references. IF input for receiver section. Must have DC blocking cap. The capacitor value should be appropriate for the IF frequency. External matching to 50 recommended. For half duplex operation, connect RX IF IN and TX IF IN signals together after the DC blocking caps, then run a transmission line from the output of the IF SAW. AC coupling capacitor must be less than 150pF to prevent delay in switching RX to TX/TX to RX. Input for the TX IF signal after SAW filter. External DC blocking cap required. External matching to 50 recommended. For half duplex operation, connect RX IF IN and TX IF IN signals together after the DC blocking caps, then run a transmission line from the output of the IF SAW. AC coupling capacitor must be less than 150pF to prevent delay in switching RX to TX/TX to RX. Power supply for the TX 15dB gain amp and TX VGA. Gain control setting for the transmit VGA. Positive slope. IF LO input. Must have DC blocking cap. The capacitor value should be appropriate for the IF frequency. LO frequency=2xIF. Quad mod/ demod phase accuracy requires low harmonic content from IF LO, so it is recommended to use an n=3 LPF between the IF VCO and IF LO. This is a high impedance input and the recommended matching approach is to simply add a 100 shunt resistor at this input to constrain the mismatch. This pin requires a 6.5A DC bias current. This can be accomplished with a 270k resistor to VCC for 3.3V operation. Power supply for IF LO buffer and quadrature phase network. No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results. This is the output transistor of the power amp stage. It is an open collector output. The output match is formed by an inductor to VCC, which supplies DC and a series cap.
From TX RF Image Filter
Interface Schematic
VCC
Pins 3, 4, 5
10k ESD
To Logic
4 5
RX EN TX EN
See pin 3.
See pin 3.
6 7
VCC1 RX IF IN
See pin 8.
8
TX IF IN
IF SAW Filter
50 strip
DC Block P in 7
Pin 8
9 10 11
VCC9 TX VGC IF LO
R ecom m en ded M atc hing N etw ork for IF LO IF V C O 1 00 C2 1 50 pF
V CC
11
IF LO
P in 1 1
270 k
12 13 14
VCC8 NC RF OUT
VCC
VCC
strip
CBYP 22 nF
CBYP 22 nF Power Amp Output PA OUT PA OUT
Pin 14
14 mA
VCC6
Pin 16
Pin 15
34 mA
PA IN
Pin 18
Bias
Bias
15 16
RF OUT VCC6
This is the output transistor of the power amp stage. It is an open collector output. The output match is formed by an inductor to VCC, which supplies DC and a series cap. Power supply for the PA driver amp. This inductance to ground via decoupling, along with an internal series capacitor, forms the interstage match.
See pin 14.
See pin 14.
Rev A8 010418
2-5
TRANSCEIVERS
RF2938
Pin 17 18 19 20 Function NC PA IN NC VCC5 Description
No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results. Input to the power amplifier stage. This is a 50 input. Requires DC blocking/tuning cap. No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results. Supply for the RF LO buffer, RF upconverter and amplifier.
Interface Schematic
See pin 14.
VCC VCC CBYP 22 nF VCC5
Pin 20
C BYP 22 nF To TX RF Image Filter
RF OUT
Pin 22
12 mA
From TX VGA
VB
RF LO
Pin 21
CBLOCK 22 pF
From RF VCO
21 22 23
RF LO RF OUT IF1 OUT-
Single ended LO input for the transmit upconverter. External matching See pin 20. to 50 and a DC block are required. Upconverted Transmit signal. This 50 output is intended to drive an See pin 20. RF filter to suppress the undesired sideband, harmonics, and other outof-band mixer products. The inverting open collector output of the quadrature modulator. This pin needs to be externally biased and DC isolated from other parts of IF1 OUT+ the circuit. This output can drive a Balun with IF1 OUT+, to convert to unbalanced to drive a SAW filter. The Balun can be either broadband (transformer) or narrowband (discrete LC matching). Alternatively, just IF1 OUT+ can be used to drive a SAW single-ended with an RF choke (high Z at IF) from VCC to IF1 OUT-. No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results. The non-inverting open collector output of the quadrature modulator. This pin needs to be externally biased and DC isolated from other parts of the circuit. This output can drive a Balun with IF1 OUT-, to convert to unbalanced to drive a SAW filter. The Balun can be either broadband (transformer) or narrowband (discrete LC matching). Alternatively, just IF1 OUT+ can be used to drive a SAW single-ended with an RF choke (high Z at IF) from VCC to IF1 OUT+. This is the in-phase modulator bypass pin. A 10nF capacitor to ground is recommended. I input to the baseband 5 pole Bessel LPF for the transmit modulator. This is the quadrature modulator bypass pin. A 10nF capacitor to ground is recommended. Q input to the baseband 5 pole Bessel LPF for the transmit modulator. Power supply for quadrature modulator. Baseband analog signal output for in-phase channel. 500mVP-P linear output. Logic-level data output for the in-phase channel. This is a digital output signal obtained from the output of a Schmitt trigger. 0.3V to VCC3 - 0.3V swing minimum. Baseband analog signal output for quadrature channel. 500mVP-P linear output. Logic-level data output for the quadrature channel. This is a digital output signal obtained from the output of a Schmitt trigger. 0.3V to VCC3 - 0.3V swing minimum. No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results.
IF1 OUT-
24
NC IF1 OUT+
11
TRANSCEIVERS
25
See pin 23.
26 27 28 29 30 31 32 33 34 35
2-6
TXI BP TXI DATA TXQ BP TXQ DATA VCC4 I OUT RXI DATA Q OUT RXQ DATA NC
Rev A8 010418
RF2938
Pin 36 37 38 39 40 41 42 43 44 45 46 47 48 Pkg Base ESD Function NC NC RSSI DCFB I DCFB Q VCC3 VREF 2 NC BW CTRL VCC2 VREF 1 RX VGC NC Description
No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results. No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results. Received signal strength indicator. Connect 8.2pF to ground. Output impedance is 40k in parallel with 2pF. DC feedback capacitor for in-phase channel. Requires decoupling capacitor to ground. (22nF recommended) DC feedback capacitor for quadrature channel. Requires capacitor to ground. (22nF recommended) Supply for the I and Q data amps.This pin should be bypassed with a 10nF capacitor connected as direct as possible to GND3. Ground this pin if data amps are not used. Gain control reference voltage. No current should be drawn from this pin (<50A). 2.0V nominal. No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results. This pin requires a resistor to ground to set the baseband LPF bandwidth of the receiver and transmit GmC filter amps. Supply for the I and Q baseband and GmC filters. This pin should be bypassed with a 10nF capacitor. This is a bypass pin for the bias circuits of the GmC filter amps and for I/Q inputs. No current should be drawn from this pin (<10A). 1.7V nominal. Receiver IF and baseband amp gain control voltage. Negative slope. No internal connection. May be grounded or connected on adjacent signal or left floating. Connect to ground for best results. Ground for all circuitry in the device. A very low inductance from the base to the PCB groundplane is essential for good performance. Use an array of vias immediately underneath the device. This diode structure is used to provide electrostatic discharge protection to 3kV using the Human body model. The following pins are protected: 3-6, 9, 10, 12, 26-34, 38-42, 44-47.
Interface Schematic
VCC
11
TRANSCEIVERS
Rev A8 010418
2-7
RF2938
State Decode Table Sleep Mode Baseband Only Receive Mode Transmit Mode Full Duplex NOTES BB_EN Enables:
TX_LPF's and buffers Quad Demodulator mixers Baseband VGA and gm-C LPF's Data Amplifiers IF LO buffer/phase splitters
PD 0 1 1 1 1
Input Pins RX EN x 0 1 0 1
TX EN x 1 1 0 0
Internally Decoded Signals BB EN RXIF EN TXRF EN 0 0 0 1 0 0 1 1 0 1 0 1 1 1 1
RXIF_EN Enables:
Front-end IF amplifier (RX) RX IF VGA amplifiers
TXRF_EN Enables:
Front-end IF amplifier (TX) TX VGA RF upconverter and buffer PA driver RF LO buffer
11
TRANSCEIVERS
Quad Modulator mixers
2-8
Rev A8 010418
RF2938
Detailed Functional Block Diagram
BW CTRL RX VGC DCFB Q VREF 1 VREF 2 DCFB I
VCC2
VCC3
RSSI
NC
NC
48 NC 1
47
46
45
44
43
42
41
40
39
38
37 36 NC
BW Control
NC
NC
2
35
NC
PD
3
DC Feedback
34
RXQ DATA
RX EN
4
Logic
+5 dB
0-30 dB
gm-C LPF
33 +6 dB
DC Feedback
Q OUT
0 dB
TX EN
5
REF
32
RXI DATA
VCC1
6 -6 to 37 dB +5 dB 0-30 dB RX
gm-C LPF
31 +6 dB
I OUT
0 dB
15 dB RX IF IN 7
TX Bias
30
VCC4
TX 15 dB TX IF IN 8 -20 to -3 dB
gm-C LPF
29
TXQ DATA
VCC9
9
28
TXQ BP
TX VGC 10 2 IF LO 11 25 dB VCC8 12 13 NC 14 RF OUT 15 RF OUT 16 VCC6 17 NC 18 PA IN 19 NC 20 VCC5 21 RF LO 22 RF OUT 23 IF1 OUT24 NC 25 IF1 OUT+
Phase Splitter
gm-C LPF
27
TXI DATA
11
TRANSCEIVERS
-1.5 dB
3.5 dB 26 TXI BP
Rev A8 010418
2-9
RF2938
Theory of Operation
RECEIVER RX IF AGC/Mixer The front end of the IF AGC starts with a single-ended input and a constant gain amp of 15dB. This first amp stage sets the noise figure and input impedance of the IF section, and its output is taken differentially. The rest of the signal path is differential until the final baseband output, which is converted back to single-ended. Following the front end amp are multiple stages of variable gain differential amplifiers, giving the IF signal path a gain range of 9dB to 52dB. The noise figure (in max gain mode) of the IF amplifiers is 5dB, which should not degrade the system noise figure. The IF to BB mixers are double-balanced, differential in, differential out, mixers with 5dB conversion gain. The LO for each of these mixers is shifted 90 so that the I and Q signals are separated in the mixers. RX Baseband Amps, Filters, Data Slicers, and DC Feedback At baseband frequency, there are multiple AGC amplifiers offering a gain range of 0dB to 30dB. Following these amplifiers are fully integrated gm-C low pass filters to further filter out-of-band signals and spurs that get through the SAW filter, anti-alias the signal prior to the A/D converter, and to band-limit the signal and noise to achieve optimal signal-to-noise ratio. The 3dB cut-off frequency of these low pass filters is programmable with a single external resistor, and continuously variable from 1MHz to 35MHz. A five-pole Bessel type filter response was chosen because it is optimal for data systems due to its flat delay response and clean step response. Butterworth and Chebychev type filters ring when given a step input making them less ideal for data systems. The filter outputs, with +6dBm gain, drive the linear 500mVPP signal off-chip, but also connect internally to a data slicer which squares up the signal to CMOS levels, and drives this "data" signal off-chip. This data slicer is a high speed CMOS comparator with 30mV of hysteresis and self-aligned input DC offset. This data slicer can be independently disabled if only the linear outputs are desired. DC feedback is built into the baseband amplifier section to correct for input offsets. Large DC offsets can arise when a mixer LO leaks to the mixer input and then mixes with itself. DC offsets can also result from random transistor mismatches. A large external capacitor is needed for the DC feedback to set the high pass 2-10 cutoff, and this capacitor is reused to set the DC input level for the self-aligned data slicer. RSSI and VGC Operation The receive signal path also has an RSSI output which is the sum of both the I and Q channels. The RSSI has about 60dBm of dynamic range and the RSSI characteristic is optimized to give best linearity and dynamic range at a VGC setting of 1.4V. It is recommended that the system sets VGC to 1.4V to take an RSSI reading to make channel activity and signal level decisions, then adjusts VGC to obtain optimum dynamic range from the IOUT and QOUT outputs. LO Input Buffers RF LO Buffer The RF LO input has a limiting amplifier before the mixer on both the RF2444 (RX) and RF2938 (TX). This limiting amplifier design and layout is identical on both ICs, which will make the input impedance the same as well. Having this amplifier between the VCO and mixer minimizes any reverse effect the mixer has on the VCO, expands the range of acceptable LO input levels, and holds the LO input impedance constant when switching between RX and TX. The LO input power range is -18dBm to +5dBm, which should make it easy to interface to any VCO and frequency synthesizer. IF LO Buffer The IF LO input has a limiting amplifier before the phase splitting network to amplify the signal and help isolate the VCO from the IC. Also, the LO input signal must be twice the desired intermediate frequency. This simplifies the quadrature network and helps reduce the LO leakage onto the RX_IF input pin (since the LO input is now at a different frequency than the IF). The amplitude of this input needs to be between -15dBm and 0dBm. Excessive IF LO harmonic content affects phase balance of the modulator and demodulator so it is recommended that a simple n=3 low pass filter is included between VCO and IF LO input. The IF LO input requires a DC bias current of +6.5A. This can be accomplished with a 270k resistor to VCC for 3.3V operation. Failing to provide this will cause a phase imbalance in the IF LO quadrature divider of up to 8, which in turn causes a similar imbalance in the I/Q outputs and the TX modulator.
11
TRANSCEIVERS
Rev A8 010418
RF2938
TRANSMITTER TX LPF and Mixers The transmit section starts with a pair of 5-pole Bessel filters identical to the filters in the receive section and with the same 3dB frequency. These filters pre-shape and band-limit the digital or analog input signals prior to the first upconversion to IF. These filters have a high input impedance and expect an input signal of 200mVPP typical. Following these low pass filters are the I/Q quadrature upconverter mixers. Each of these mixers is half the size and half the current of the RF to IF downconverter on the RF2444. Recall that this upconverted signal may drive the same SAW filter (in half duplex mode) as the RF2444 and therefore share the same load. Having the sum of the two BB to IF mixers equal in size and DC current to the RF to IF mixer, will minimize the time required to switch between RX and TX, and will facilitate the best impedance match to the filter. TX VGA The AGC after the SAW filter starts with a switch and a constant gain amplifier of 15dB, which is identical to the circuitry on the receive IF AGC. This was, done, as on the RX signal path, so that the input impedance will remain constant for different TX gain control voltages. Following this 15dB gain amplifier is a single stage of gain control offering 15dB gain range. The main purpose of adding this variable gain is to give the system the flexibility to use different SAW filters and image filters with different insertion loss values. This gain could also be adjusted real time, if desired. TX Upconverter The IF to RF upconverter is a double-balanced differential mixer with a differential to single-ended converter on the output to supply 0dBm peak linear power to the image filter. The upconverted SSB signal should have -6dBm power at this point, and the image will have the same power, but due to the correlated nature of the signal and image, the output must support 0dBm of linear power to maintain linearly. +6dBm PA Driver The SSB output of the upconverter is -6dBm of linear power. The image filter should have at most 4dB of insertion loss while removing the image, LO, 2LO and any other spurs. The filter output should supply the PA driver input -10dBm of power. The PA driver is a two-stage class A amplifier with 10dB gain per stage and capable of delivering 6dBm of linear power to a 50 load, and has a 1dB compression point of 12dBm. For lower power applications, this PA driver can be used to drive a 50 antenna directly.
11
TRANSCEIVERS
Rev A8 010418
2-11
RF2938
RF M icro D evices 2.4 G Hz ISM Chipset
IL = 3 -4 dB 2.4 to 2 .48 3 G H z VGC1
R F 2 93 8 TQ F P -4 8 E P P
RSSI
R F 24 4 4 S S O P -16 E P P
G ain S e le ct
OUT Q
SAW
IL = 10 dB m ax
RX
LNA D u al G a in M o de s -5 dB a nd +10 dB 15 dB G ain
RX
15 dB
DATA Q
IF A m p
-1 5 d B to 3 5 d B G a in OUT I
TX
15 dB B as e B an d A m p. A ctive S elec tab le LP F (f C = 1 M H z to 4 0 M H z ) 0-3 0 d B G a in
Filter
2 .4 to 2.4 83 G H z
TX
D is cre te P in D io de
DATA I
R F 25 1 7 S SO P -2 8 RF VCO IF VCO 2 + 4 5 -45
D u al F req ue n cy S yn th esize r
F ilter
I IN P U T
R F 2 1 26
23 dB m or 3 3 d B m E x tern al P A
10 dBm P A D riv er
1 5 d B G a in R a ng e
F ilter
S elec tab le LP F Q IN P U T
VGC2
IL = 3 -4 d B 2.4 to 2.48 3 G H z
Figure 1. Entire Chipset Functional Block Diagram
11
TRANSCEIVERS
2-12
Rev A8 010418
RF2938
Evaluation Board Schematic
(Download Bill of Materials from www.rfmd.com.)
NOTES: 1) R4 is used to set the bandwidth of the GMC Filters. 2) Pins 14 through 22 contain 2.4 GHz signals. Place tuning/bypass components as close as possible. Make all lines on these pins 50 . 3) For normal operation, move C33 to C38 and install all components with an asterisk. *Do not populate. 50 strip C17 8 pF PD RX EN TX EN VCC R5 10 C13 100 pF 1 2 3 4
IF Amp I
VCC
R6 0 VGC C14 100 pF C10 10 nF R4 10 k
R7 10
C15 100 pF C11 10 nF C19 22 nF C18 22 nF
J15 RSSI
48
47
46
45
44
43
42
41
40
39
38
37 36 35 34 50 strip 33 32 50 strip 50 strip 50 strip
J14 Q DATA J13 Q OUT J12 I DATA J11 I OUT
J1 RX IF IN
50 strip
C4 100 pF R3* 0
50 strip
L2 150 nH
5
15 dB -15 dB to 35 dB Gain Q
6 7 8 R10* 0 L9 68 nH 9
Q Baseband Amp Active Selectable LPF (fc=1 MHz to 40 MHz) 0-30 dB Gain
31 30 29
15 dB I Active Selectable LPF (fc=1 MHz to 40 MHz)
J2 TX IF IN
50 strip
C36 2 pF
C3 100 pF
RX_EN
15 dB Gain Range
C20 22 nF 50 strip C6 0.1 uF C2 10 nF C5 0.1 uF C1 10 nF
2938400, Rev -
VCC
TX_EN
J10 Q IN
28 27 2 +45 -45 26 25 13 14 15 16 17 18 19 20 21 22 23 24
VCC C21 22 nF GC TX J3 IF LO 50 strip C25 1 pF L6 27 nH VCC C7 100 pF R1 270 k
10 11 12
50 strip
J9 I IN
L8 39 nH R8 1 k
VCC C34 22 nF 50 strip J8 IF OUT
C16 22 nF
L1 2.7 nH VCC C23 22 nF P1 P1-1 C9 10 nF + C12 4.7 uF P1-3 1 2 3 CON3 P2 P2-1 1 2 P2-3 3 CON3 TX EN GND RX EN P3-3 P3-1 P3 1 2 3 CON3 PD GND VGC J4 PA OUT VCC VCC GND GC TX 50 strip C26 12 pF
C24 22 nF
C27 2 pF
C22 22 nF
C28 22 pF L3 3.9 nH C29 3 pF 50 strip
L7 220 nH C31 3 pF
C38* 5 pF C32 3 pF
IN
C33 5 pF
FL1*
50 strip
OUT
SAWTEK 855392
50 strip L4 3.9 nH C25 22 nF
C30 22 pF
50 strip
J7 RF OUT
J5 PA IN VCC
J6 RF LO
11
TRANSCEIVERS
Rev A8 010418
2-13
RF2938
Evaluation Board Layout Board Size 2.580" x 2.086"
Thickness: Top to Ground Laminate, 0.008"; Ground to Bottom Laminate, 0.023"; Board Material FR-4; Multi-Layer
11
TRANSCEIVERS
2-14
Rev A8 010418
RF2938
VIN versus POUT
-3.0 -4.0 -5.0 -6.0 -7.0 (VCC=2.7V to 3.6V, I & Q in=1MHz, RBW=10k , IF LO=560MHz@-10dBm) Pout, -40C Pout, 25C Pout, 85C 0.50 0.60
VIN versus Amplitude Error
(VCC=2.7V to 3.6V, I & Q in=1MHz, RBW=10k , IF LO=560MHz@-10dBm) Ampl Err, -40C Ampl Err, 25C Ampl Err, 85C
Amplitude Error (dB)
200.0 300.0 400.0 500.0 600.0 700.0 800.0
-8.0
0.40
POUT (dBm)
-9.0 -10.0 -11.0 -12.0 -13.0 -14.0 -15.0 -16.0 -17.0 100.0
0.30
0.20
0.10
0.00 0 100 200 300 400 500 600 700 800
VIN (mVP-P)
VIN (mVP-P)
TX IF POUT versus IF LO
-14.4 -14.6 -14.8 -15.0 Pout, -40C Pout, 25C Pout, 85C (VCC=3.15V, I & Q in=1MHz@100mVP-P, RBW=10k , IF LO=560MHz) -22.0 -24.0 -26.0 -28.0 -30.0 -32.0 -34.0 -36.0 -38.0 -40.0 -42.0 -44.0 -46.0 -48.0 -50.0 -52.0 -54.0 -56.0 -58.0 -60.0 -62.0 -25.0
LO & 2LO Out versus IF LO (VCC=3.15V, IF LO=560MHz)
LO_out, -40C 2LO_out, -40C LO_out, 25C 2LO_out, 25C LO_out, 85C 2LO_out, 85C
TX IF POUT (dBm)
-15.2 -15.4 -15.6 -15.8 -16.0 -16.2 -16.4 -25.0
LO Out (dBm)
11
-20.0 -15.0 -10.0 -5.0 0.0
-20.0
-15.0
-10.0
-5.0
0.0
IF LO (dBm)
IF LO (dBm)
RF Conversion Gain versus RF LO Level
(VCC=3.15V, Tx IF in=280MHz@-50dBm, RF LO=2160MHz) 20.0 19.5 19.0 18.5 18.0 17.5 17.0 16.5
RF LOOUT & RF 2LOOUT versus RF LO Level (VCC=3.15V,
VGC=1.5V, Tx IF in=280MHz@-50dBm, RF LO=2160MHz, 2LOOUT=4320MHz) 0.0 25C LOout 85C LOout -5.0 -40C LOout 25C 2LOout 85C 2LOout -10.0 -15.0
LOOUT (dBm)
Gain (dB)
-20.0 -25.0 -30.0 -35.0 -40.0 -45.0 -50.0 -20.0 -18.0 -16.0 -14.0 -12.0 -10.0 -8.0 -6.0 -4.0
16.0 15.5 15.0 14.5 14.0 13.5 13.0 12.5 12.0 11.5 11.0 -20.0 -18.0 -16.0 -14.0 -12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 25C Gain 85C Gain -40C Gain
-2.0
0.0
2.0
4.0
6.0
RF LO (dBm)
RF LO (dBm)
Rev A8 010418
2-15
TRANSCEIVERS
RF2938
RF Conversion Gain versus VGC
(VCC=2.7V, Tx IF in=280Mhz-50dBm, RF LO=2160MHz@-10dBm) 31.0 30.0 29.0 28.0 27.0 26.0 25.0 24.0 23.0 22.0 21.0 20.0 19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 25C Gain 85C Gain -40C 32.0 31.0 30.0 29.0 28.0 27.0 26.0 25.0 24.0 23.0 22.0 21.0 20.0 19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0
RF Conversion Gain versus VGC
(VCC=3.15V, Tx IF in=280MHz@-50dBm, RF LO=2160MHz @-10dBm) 25C Gain 85C Gain -40C Gain
Gain (dB)
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
Gain (dB)
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
VGC (VDC)
VGC (VDC)
RF Conversion Gain versus VGC
(VCC=3.6V, Tx IF in=280MHz@-50dBm, RF LO=2160MHz@-10dBm) 32.0 31.0 30.0 29.0 28.0 27.0 26.0 25.0 24.0 23.0 22.0 21.0 20.0 19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 -7.0 25C Gain 85C Gain -40C Gain -8.0 -9.0 -10.0 -11.0 -12.0 -13.0
IF-RF IIP3 versus VGC
(VCC=2.7V, Tx IF in=12dB Below IP1dB, RF LO=2160MHz@-10dBm) 25C IIP3 85C IIP3 -40C IIP3
IIP3 (dBm)
Gain (dB)
-14.0 -15.0 -16.0 -17.0 -18.0 -19.0 -20.0 -21.0 -22.0 -23.0 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
11
TRANSCEIVERS
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
VGC (VDC)
VGC (VDC)
IF-RF IIP3 versus VGC
(VCC=3.15V, Tx IF in=12dB Below IP1dB, RF LO=2160MHz@-10dBm) -7.0 -8.0 -9.0 -10.0 -11.0 -12.0 -13.0 25C IIP3 85C IIP3 -40C IIP3 -7.0 -8.0 -9.0 -10.0 -11.0 -12.0 -13.0 -14.0 -15.0 -16.0 -17.0 -18.0 -19.0 -20.0 -21.0 -22.0 -23.0 -24.0 -25.0 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
IF-RF IIP3 versus VGC
(VCC=3.6V, Tx IF in=12dB Below IP1dB, RF LO=2160MHz@-10dBm) 25C IIP3 85C IIP3 -40C IIP3
IIP3 (dBm)
-15.0 -16.0 -17.0 -18.0 -19.0 -20.0 -21.0 -22.0 -23.0 -24.0
IIP3 (dBm)
-14.0
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
VGC (VDC)
VGC (VDC)
2-16
Rev A8 010418
RF2938
IF-RF OP1dB versus VGC
(VCC=2.7V, Tx IF in=280Mhz, RF LO=2160MHz@-10dBm) -3.5 -4.0 -4.5 -5.0 -5.5 25C OP1dB 85C OP1dB -40C OP1dB -3.5 -4.0 -4.5 -5.0 -5.5 25C OP1dB 85C OP1dB -40C OP1dB
IF-RF OP1dB versus VGC
(VCC=3.15V, Tx IF in=280MHz, RF LO=2160MHz@-10dBm)
OP1dB (dBm)
-6.5 -7.0 -7.5 -8.0 -8.5 -9.0 -9.5 -10.0 -10.5 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
OP1dB (dBm)
-6.0
-6.0 -6.5 -7.0 -7.5 -8.0 -8.5 -9.0 -9.5 -10.0 -10.5 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
VGC (VDC)
VGC (VDC)
IF-RF OP1dB versus VGC
(VCC=3.6V, Tx IF in=280MHz, RF LO=2160MHz@-10dBm) -3.0 -3.5 -4.0 -4.5 -5.0 25C OP1dB 85C OP1dB -40C OP1dB 210.0 200.0 190.0 180.0 170.0 160.0 150.0
ICC versus RBW (Temp=Ambient, VCC=3.15V, GC TX=1.5V,
I & Q in=100mVP-P, IF LO=-10dBm) Tx Icc Rx Icc Total Icc
OP1dB (dBm)
-5.5
ICC [mA]
-6.0 -6.5 -7.0 -7.5 -8.0 -8.5 -9.0 -9.5 -10.0 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
140.0 130.0 120.0 110.0 100.0 90.0 80.0 70.0 60.0 1.0 10.0 100.0 1000.0
11
RBW [k]
VGC (VDC)
TX 3dB BW point versus RBW (Broadband 50 match on IF out, Temp=Ambient,
VCC=3.15V, GCTX=1.5V, I & Qin=100mVP-P, IFLO=560MHz @-10dBm)
RX 3dB BW versus RBW (Temp=Ambient, VCC=3.15V, VGC=1.6V,
30.0 RX IFIN =-67dBm, IF LO=560MHz@-10dBm)
50.0 45.0
25.0 40.0 35.0 30.0 25.0 20.0 15.0 10.0 5.0 5.0 0.0 1.0 10.0 100.0 1000.0 0.0 1.0 10.0 100.0 1000.0
3 dB BW Point [MHz]
3dB BW Point [MHz]
20.0
15.0
10.0
RBW [k]
RBW [k]
Rev A8 010418
2-17
TRANSCEIVERS
RF2938
RX ICC versus VCC (VGC=1.2V to 2.0V, I & Q_out=500mVP-P,
70.00 69.50 69.00 68.50 68.00 67.50 67.00 66.50 66.00 65.50 65.00 64.50 64.00 63.50 63.00 62.50 62.00 61.50 61.00 60.50 60.00 59.50 59.00 2.7 IF LO=560MHz@-10dBm, RBW=100k) ) Icc, -40C Icc, +25C Icc, +85C 100.00 95.00 90.00 85.00 80.00 75.00 70.00 Gain, -40C Gain, +25C Gain, +85C
RX Gain versus VGC (VCC=2.7-3.6V, RX IFIN=280.5MHz, RBW=100k , I & Q
out=500mVP-P, IF LO=560MHz@-10dBm)
Gain (dB)
ICC (mA)
65.00 60.00 55.00 50.00 45.00 40.00 35.00 30.00 25.00 20.00 15.00
2.8
2.9
3.0
3.1
3.2
3.3
3.4
3.5
3.6
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
VCC (VDC)
VGC (VDC)
Input P1dB versus VGC (Temp=Ambient, VCC=3.15V,
-15.00 -20.00 -25.00 -30.00 -35.00 RX IFIN=280.5MHz, RBW=100k , IF LO=560MHz@-10dBm) 38.00 36.00 34.00 32.00 30.00 28.00
Noise Figure versus VGC (Temp=Ambient, VCC=3.15V,
RX IFIN=291MHz, RBW=5.1k , IF LO=560MHz@-10dBm)
Input P1dB [dBm]
Noise Figure [dB]
1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0
-40.00 -45.00 -50.00 -55.00 -60.00 -65.00
26.00 24.00 22.00 20.00 18.00 16.00 14.00 12.00 10.00
11
TRANSCEIVERS
-70.00 -75.00 -80.00 -85.00
8.00 6.00 4.00 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0
VGC [VDC]
VGC [VDC]
I & Q Amplitude Balance versus VGC (VCC=3.15V, RX IFIN=280.5MHz,
RBW=100k , I & Q out=500mVP-P, IF LO=560MHz@-10dBm)
I & Q Phase Balance versus VGC (VCC=2.7-3.6V,
RX IFIN=280.5MHz, RBW=100k , I & Q out=500mV P-P, IF LO=560MHz@-10dBm)
3.00 Ampl_Err, -40C 2.50 Ampl_Err, +25C Ampl_Err, +85C
12.00 11.00 10.00 9.00
I & Q Amplitude Error (dB)
I & Q Phase Error ( o)
2.00
8.00 7.00 6.00 5.00 4.00 3.00 Phase Err, -40C
1.50
1.00
0.50
2.00 1.00
Phase Err, +25C Phase Err, +85C
0.00 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0
0.00 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0
VGC (VDC)
VGC (VDC)
2-18
Rev A8 010418
RF2938
RSSI versus VGC (VCC=3.15V, Temp=25oC, IF LO=-10dBm)
2.600 2.500 2.400 2.300 2.200 2.100 2.000 1.900 1.800 1.700 1.600 1.500 1.400 1.300 1.200 1.100 1.000 0.900 0.800 0.700 0.600 -100 RSSI, VGC= 1.2V RSSI, VGC= 1.4V RSSI, VGC= 1.6V RSSI, VGC= 1.8V RSSI, VGC= 2.0V
RSSI versus VCC (VGC=1.4V, Temp=25oC, IF LO=-10dBm)
2.800 2.700 2.600 2.500 2.400 2.300 2.200 2.100 2.000 1.900 1.800 1.700 1.600 1.500 1.400 1.300 1.200 1.100 1.000 -100 RSSI, Vcc= 2.7V RSSI, Vcc= 3.15V RSSI, Vcc= 3.6V
RSSI (VDC)
RSSI (VDC)
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
RF Lvl (dBm)
RF Lvl (dBm)
RSSI versus Temp (VCC=3.15V, VGC=1.4V, IF LO=-10dBm)
2.600 2.500 2.400 2.300 2.200 2.100 RSSI, -40C RSSI, +25C RSSI, +85C 24.00 23.75 23.50 23.25 23.00 22.75 22.50 22.25 22.00 21.75 21.50 21.25 21.00 20.75 20.50 20.25 20.00 19.75 19.50 19.25 19.00 2.70
PA Gain versus VCC
(PA in=2440MHz@-30dBm)
-40C Gain 25C Gain 85C Gain
RSSI (VDC)
2.000 1.900 1.800 1.700 1.600 1.500 1.400 1.300 1.200 1.100 1.000 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0
Gain (dB)
11
3.15 3.60
RF Lvl (dBm)
VCC (V)
PA IIP3 versus VCC
(PA in=2439 & 2440MHz@13dB Below IP1dB Point) 3.25 3.00 2.75 2.50 2.25 -40C IIP3 25C IIP3 85C IIP3 14.00 13.75 14.50 14.25
PA OP1dB versus VCC
(PA in=2440MHz) -40C OP1dB 25C OP1dB 85C OP1dB
OP1dB (dBm)
IIP3 (dBm)
2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0.00 2.70
13.50 13.25 13.00 12.75 12.50 12.25 12.00 2.70
3.15
3.60
3.15
3.60
VCC (V)
VCC (V)
Rev A8 010418
2-19
TRANSCEIVERS
RF2938
PA 2f0 versus VCC
(PA in=2440MHz@-15dBm, 2nd Harmonic=4800MHz) 35.00 34.75 34.50 34.25 34.00 33.75 -40C 2fo 25C 2fo 85C 2fo
2f0 (dBc)
33.50 33.25 33.00 32.75 32.50 32.25 32.00 31.75 31.50 31.25 2.70
3.15
3.60
VCC (V)
11
TRANSCEIVERS
2-20
Rev A8 010418

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