FRONT_END
Below is an example of the FRONT_END block:
[FRONT_END]
NUM_FRONT_ENDS = 2
FE01 = LION
FE02 = LION_L5
[LION]
SAMPLE_FREQ_NUMERATOR = 19999830
SAMPLE_FREQ_DENOMINATOR = 2
QUANTIZATION = 2
NUM_SUPPORTED_SIGNAL_TYPES = 8
SUPPORTED_SIGNAL_TYPES = GPS_L1_CA_PRIMARY GPS_L1_CA_ALT1 GPS_L2_CLM_PRIMARY GPS_L2_CLM_ALT1 SBAS_L1_I_PRIMARY SBAS_L1_I_ALT1 GALILEO_E1_BC_PRIMARY GALILEO_E1_BC_ALT1
FREQ_IF_HZ = 2563362.833776 2593365.172749 2560408.601713 2590410.940685 2563362.833776 2593365.172749 2563362.833776 2593365.172749
PLL_SIGN_FPLL = 1 1 1 1 1 1 1 1
CODE_PHASE_BIAS_METERS = -2.5 -2.5 4.5 4.5 -2.5 -2.5 -2.5 -2.5
[LION_L5]
SAMPLE_FREQ_NUMERATOR = 19999830
SAMPLE_FREQ_DENOMINATOR = 1
QUANTIZATION = 2
NUM_SUPPORTED_SIGNAL_TYPES = 2
SUPPORTED_SIGNAL_TYPES = GPS_L5_IQ_PRIMARY GPS_L5_IQ_ALT1
FREQ_IF_HZ = 5059956.645689 5089952.626886
PLL_SIGN_FPLL = 1 1
CODE_PHASE_BIAS_METERS = -50 -50
When using a RadioLion front end, there are three blocks: [FRONT_END], [LION], and [LION_L5]. The [FRONT_END] block holds the topology parameters, while the [LION] and [LION_L5] blocks hold the sampling and per-signal calibration parameters.
The FRONT_END block contains all of the following configuration parameters:
Topology
NUM_FRONT_ENDS
Default: None
Parameter Class: Structural Configuration
Technical Info: Number of front-end configurations defined in the [FRONT_END] block. Each front end describes a sample stream configuration, including sample rate, quantization, supported signal types, IF frequencies, and signal-specific biases.
Practical Tuning Info: For RadioLion, this value should be set to 2. In other cases, set to the number of distinct front-end / sample-stream configurations used by the receiver.
FE01, FE02, …
Default: None
Parameter Class: Structural Configuration
Technical Info: Ordered names of the front-end configuration sections to instantiate. Each FE## value must match a corresponding config block, such as [LION] or [LION_L5]. Signal banks reference these names in the [BANK] section of the .config file using their FRONT_END setting.
Practical Tuning Info: For RadioLion, which has NUM_FRONT_ENDS = 2, set as shown below:
[FRONT_END]
NUM_FRONT_ENDS = 2
FE01 = LION
FE02 = LION_L5
Sampling
SAMPLE_FREQ_NUMERATOR
Default: None
Parameter Class: Structural Configuration
Technical Info: Numerator of the front-end sample rate, in Hz, expressed together with SAMPLE_FREQ_DENOMINATOR as sample_rate = SAMPLE_FREQ_NUMERATOR / SAMPLE_FREQ_DENOMINATOR. This is the nominal sample rate used throughout PpRx.
Practical Tuning Info: Set to the nominal sample rate for the front end. Do not tune for performance; exact timing is computed in the estimator.
This value must be an integer.
SAMPLE_FREQ_DENOMINATOR
Default: None
Parameter Class: Structural Configuration
Technical Info: Denominator of the front-end sample rate, in Hz, expressed together with SAMPLE_FREQ_NUMERATOR as sample_rate = SAMPLE_FREQ_NUMERATOR / SAMPLE_FREQ_DENOMINATOR. This is the nominal sample rate used throughout PpRx.
Practical Tuning Info: Set based on the nominal sample rate for the front end. Do not tune for performance; exact timing is computed in the estimator.
This value must be an integer.
QUANTIZATION
Default: None
Parameter Class: Structural Configuration
Technical Info: Number of bits per IQ or IF sample component used by the front-end sample stream.
Practical Tuning Info: This value must be set to match the sample quantization of the front-end. For RadioLion, use a value of 2.
Supported signals
NUM_SUPPORTED_SIGNAL_TYPES
Default: None
Parameter Class: Operational Configuration
Technical Info: Number of signal types listed in SUPPORTED_SIGNAL_TYPES for this front end.
Practical Tuning Info: Set to the exact number of signals this front-end configuration supports.
This value must match the length of all the following arrays: SUPPORTED_SIGNAL_TYPES, FREQ_IF_HZ, PLL_SIGN_FPLL, and CODE_PHASE_BIAS_METERS.
SUPPORTED_SIGNAL_TYPES
Default: None
Parameter Class: Operational Configuration
Technical Info: List of signal types supported by this front-end configuration. Each listed signal has corresponding entries in the front-end arrays FREQ_IF_HZ, PLL_SIGN_FPLL, and CODE_PHASE_BIAS_METERS.
Practical Tuning Info: Include all signals for which tracking is desired. Commonly used signal names are listed below, each of which should be followed by the suffix _PRIMARY or _ALT1 to indicate which antenna is desired for tracking (e.g. GPS_L1_CA should be included in SUPPORTED_SIGNAL_TYPES as GPS_L1_CA_PRIMARY or GPS_L1_CA_ALT1):
GPS_L1_CA
GALILEO_E1_BC
BDS_B1_CPD
SBAS_L1_I
GPS_L2_CLM
GPS_L5_IQ
GALILEO_E5A_IQ
BDS_B2A_PD
Per-signal calibration
FREQ_IF_HZ
Default: None
Parameter Class: Structural Configuration
Technical Info: Intermediate frequency, in Hz, of each supported signal in the sampled front-end data stream.
Practical Tuning Info: Set this to match the nominal IF frequency of the signal in the front-end. This value should not be tuned.
For the RadioLion, use the following settings:
- All primary antenna signals at the L1 band center of 1575.42 MHz:
2563362.833776 - All alternate antenna signals at the L1 band center of 1575.42 MHz:
2593365.172749 - All primary antenna signals at the L2 band center of 1227.60 MHz:
2560408.601713 - All alternate antenna signals at the L2 band center of 1227.60 MHz:
2590410.940685 - All primary antenna signals at the L5 band center of 1176.45 MHz:
5059956.645689 - All alternate antenna signals at the L5 band center of 1176.45 MHz:
5089952.626886
This list must contain one value per entry in SUPPORTED_SIGNAL_TYPES, in the same order.
PLL_SIGN_FPLL
Default: None
Parameter Class: Structural Configuration
Technical Info: Defines whether the front end mixes the incoming RF with a wave above or below the carrier (high-side vs. low-side mixing).
Practical Tuning Info: This value is a front-end parameter and should not be tuned; -1 indicates high-side mixing, and 1 indicates low-side mixing. For RadioLion, this value should be set to 1 for all signals.
This list must contain one value per entry in SUPPORTED_SIGNAL_TYPES, in the same order.
CODE_PHASE_BIAS_METERS
Default: None
Parameter Class: Tunable
Impact of Change: Medium
Technical Info: Per-signal correction, in meters, for fixed pseudorange offsets introduced by the front-end signal path. The estimator uses this value to align measurements from different signals to a common reference.
Practical Tuning Info: This value is dependent on the differential path delay between signals in the front-end.
For RadioLion, use the following settings:
- All L1-band signals:
-2.5 - All L2-band signals:
4.5 - All L5-band signals:
-50
This list must contain one value per entry in SUPPORTED_SIGNAL_TYPES, in the same order.